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051981815	description	DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Lateral ionic drifts occur when a discontinuity develops in the body of the plasma as a result of quantum asymmetrical interactions. Quantum asymmetries are amplified to produce a bending of the body of the plasma. The result is crowding of magnetic lines of flux on one side of the plasma which tends to push the plasma toward the wall of the container and effectively lower the temperature and confinement density. The quantum asymmetries are in fact the result of internal structural irregularities within the fabric of the ponderable bodies comprising the plasma, namely the nuclei, electrons, etc. The objective then is to reorient the crystalline lattices of those of the nuclei and electrons which are inappropriate for the production of thermonuclear power in that they are subject to quantum asymmetrical interaction with other particles. This is accomplished by application of an electromagnetic field at a flux density B calculated according to the relationship mc.sup.2 =Bvlq, where "m", "v", and "l" are the mass, velocity and length, respectively, of the plasma body or constituent thereof, and "c" and "q" represent constants, namely the speed of light and the quantum of charge. According to the invention, at least one supplemental field at the required flux density to resonate with at least one form of particle in the plasma, for example deuterium nuclei, is applied to the plasma body by means of a large poloidal coil forming a solenoid of sufficient dimensions to substantially apply the supplemental field to the whole of the fusion apparatus. The flux density applied via the supplemental coil is relatively low in power as compared to the driving fields applied to the plasma in order to confine and heat it. The supplemental field can alternatively or additionally be applied by toroidal field coils, the supplemental field in each case being incident on the body of plasma and all the ponderable bodies therein. The invention relies in part on a relationship of gravitational energy (mc.sup.2) and electromagnetic energy (Bvlq). This relationship concerns the fundamental nature of particles and fields. Various persons have searched for a unified field theory which would link the physics of particles with the physics of space. The hallmark of Newtonian particle theory was force at a distance. However, this did not suit Einstein because he felt that forces at a distance could not fully describe the raw experience of daily life. Material events occur not by actions-at-a-distance but by contact. Einstein, therefore, felt that the best scientific theory is a field theory. Nevertheless, neither special nor general relativity eliminated the disturbing dualism between particle and field. It was therefore natural for Einstein, after general relativity, to attempt to create a unified field theory which could describe the electromagnetic and gravitational fields, from which particles would emerge as knots in space-time. Additionally, the electro-weak and electro-strong nuclear forces would be manifestations of the electromagnetic force. Threefold unification includes the electromagnetic, the weak and the strong nuclear forces. Fourfold unification would include gravity, the elasticity of space-time requiring that events which occur by contact may indeed produce mechanical vibrations of the electromagnetic field from electromagnetic oscillations by deformation of the gravitational field. According to the invention, gravitational and electromagnetic potential are set in dual resonance by the equation mc.sup.2 =Bvl coulomb. EQU .sigma.=Bvl, and (1) EQU E/q=.sigma.. (2) Therefore, EQU E=Bvlq. (3) Also, EQU E=mc.sup.2. (4) Thus, E/c.sup.2 is a mass point or ponderable body of field; "B" is magnetic flux; "v" is velocity, namely the relative electron and earth's orbital velocity; "l" is the length of the pertinent conductor; "E" is the magnetic field energy; ".sigma." is induced electromagnetic field strength; "q" is the electric charge; and, "c" the velocity of light. From equations (3.) and (4.), we get EQU mc.sup.2 =Bvlq Where "q" represents a single coulomb. (5) Equation (5.) is essentially the equation of cyclotron resonance, when the velocity limit maximum of a subject accelerated ion is equal to c. Thus, all point masses are considered to possess magnetic moments which relate to the total field as ponderable charged domains of matter. Therefore, all "strings" are inherently interfaces or edges of energy domains as well as components of domains. Magnetic resonance interactions and the piezoelectric effect point to the relation of the mechanical to the field in all matters, substantiated by infrared emissions from materials subjected to electromagnetic radiation. EQU v/r=B(q/m)=.omega. (6) EQU B=mv/qr (7) From equation (5.), we have ##EQU1## Combining equations (7.) and (8.), we get ##EQU2## mc.sup.2 =Bvlq shows the relation of inertial frames in equivalence as waves of fields are correlated in resonant systems of energy interactions corresponding to gravitational masses of discrete ponderable bodies of relative quantum character. Vibrating strings creating oscillations of electromagnetic fields in a much larger string, a line conductor of length l, will resonate with a system composed of quantum character (and mass m) having internal strings of total gravitational energy mc.sup.2. mass m is in each case connected to a system of particular stiffness within the conductor (l) so the electromagnetic vibrations of interaction (Bvlq) correspond with the natural resonant frequency of mass m, inducing internal vibration in mass m. An analysis of the units of measure according to equation (5.) as to a quantum, one coulomb charge is as follows, letting mc.sup.2 =Bvl(l): ##EQU3## Derived from equations (12.) and (13.): ##EQU4## The foregoing equations can be considered in discussion of Jacobson resonance (according to the invention), cyclotron resonance and Zeeman resonance. In accordance with classical mechanics and the special theory of relativity, space-time has an existence independent of matter or field. In order to describe at all that which fills or occupies space and interacts in dependence upon relative coordinates therein, space-time or the inertial system with its metrical properties must be thought of as existing to begin with, otherwise the description of "that which fills up space" has no meaning. On the basis of the general theory of relativity, on the other hand, it is space as opposed to "what fills space" which is affected in a manner relating to the coordinates of masses. Space has no separate existence. Thus a pure gravitational field might have been described in terms of the g.sub.ik (i.e., as a function of coordinates) by solution of the gravitational equations. The functions g.sub.ik describe not only the field, but at the same time also the topological and metrical structural properties of the manifold. Then it follows, there is no such thing as an empty space; i.e , a space without field. Space-time does not claim existence on its own, but only as a structural quality of the field. Thus, according to Einstein, Descartes was not far from the truth when he believed he must exclude the existence of an empty space. The notion appeared to Einstein as absurd, so long as physical reality is seen exclusively in ponderable bodies. It requires the idea of the field as the representative of reality, in combination with the general principle of relativity, to show the true kernel of Descartes idea: there it exists no space "empty of field". mc.sup.2 =Bvl coulomb describes the mathematical relation of quantum mechanics to general relativity in terms manifest by the concrete physical reality of gravitational point masses and vibrating string or wave segments of spatial line extensions; i.e., wavelength as given by .lambda.=h/mv, comprised by reference points. DeBroglie waves or waves of probability describe a set of waves that represent the behavior under appropriate conditions of a particle, e.g., its diffraction by a crystal lattice. In Zeeman and cyclotron resonance, a wave is considered a disturbance traveling through a medium by virtue of elastic and inertial factors of the medium being relatively small and returning to zero. When the disturbance has passed .lambda. represents the distance in a wavetrain between a vibrating particle and the nearest one vibrating in the same phase. In Jacobson resonance, "l" represents summation of all the distances between vibrating ponderable bodies, i.e., the total length of a system under consideration as does "q" represent the summation of all the charges that experience a force from the total energy resulting from the electromagnetic field interaction when there occurs unification of gravity and electromagnetic potential. Thus, in this context, .lambda.=l (length) and q=l (unity). This includes four-dimensional space delineated by a total field incorporating gravitational points or ponderable bodies generating all action-at-a-distance by way of string. Two postulates are essential features of this equivalence of gravitational and electromagnetic interaction energies in dual resonance: (a) All spontaneous interactions are independent. Inertial systems are independent in terms of ponderable bodies but dependent upon the hitherto "undetected" aether. The foregoing explains the reason for the absence of electromagnetic fields in the pure gravitational equations. Gravity is based upon an inertial system independent of electromagnetic fields and dependent upon the ponderable bodies comprising the gravitational field. (b) Gravitational energy is outside matter because it is contained within the abstract point masses formulating the fabric of the metric of space-time itself. The gravitational energy is hidden in the abstract points creating this elemental structure of the pure spatial metric according to E=mc.sup.2. In considering the fundamental equation of magnetic resonance, we write the expression E=the g.sub.e factor the Bohr magneton * the flux density * c. When the electronic g factor=2 and the Bohr magneton=(qh)/(4 pimc), we look for the equivalence of the expression (g.sub.e * .beta..sub.e * B * c)=Bclq. In this manner, we shall determine that the cyclotron resonance equation and the fundamental equation of magnetic resonance are precisely the same as the general unified field equation, mc.sup.2 =Bvl coulomb, when vmax=c, and r=1. We note DeBroglie said, when v=c EQU l=.lambda.=h/mc, .lambda. being distance. (15) The Bohr magneton is the equal to ##EQU5## Thus, EQU g.sub.e .beta..sub.e Bc=g.sub.e BcLq/2=E=mc.sup.2 (17) The adjustment for the 2 in the denominator is made in Zeeman resonance by the electronic g factor. Note g.sub.e =2.002322. Therein, the electronic g factor is equal to 2 and adjusts the magnetic resonance equation so that it is an expression equal to Bclq which is equal to energy. In accordance with the understanding that the symbol v is equal to c, with respect to the Lorentz transformation relative to the coordinate system of the perceiver, we see that in the equation of Zeeman resonance c is a constant which connotes an inertial velocity utilized in all calculations, precisely as the orbital earth velocity is used for our current purposes in all calculations for the general unified field equation, mc.sup.2 =Bvl coulomb. In considering the E=g.sub.e .beta..sub.e Bc (equation (17.)), we see that we may write EQU E=mc2=2qmc.sup.2 (t/4pimc)Bc. (18) Dividing both sides by mc.sup.2 and by t, we get the expression ##EQU6## This is precisely the expression for cyclotron resonance. Furthermore, in accordance with equation (6.), we may write the expression for cyclotron resonance as v/r=qB/m. When r=1, EQU mv=rqB=lqB. (20) Dividing both sides by t, EQU mv/t =vqB=F. (21) Multiplying both sides by l, EQU Fl=W=E=Bvlq (22) Thus, as a general expression for the equation for cyclotron resonance, we may write mc.sup.2 =Bvlq. However, when dealing with the equation for cyclotron resonance in a more specific manner, we may let v=c and write EQU c/r=qB/m (23) Therefore, EQU mc=qBr (24) Again, r=l, and EQU mc=qBl (25) Multiplying both sides by c, results in equation (17.), namely mc.sup.2 =Bclq, the same expression that we obtained from the fundamental equation for magnetic resonance when the upper velocity limit of the accelerated ion equals c. We note that when mv.sup.2 =mc.sup.2, we may write m.sub.1 v.sup.2 =m.sub.2 c.sup.2 and m.sub.1 is greater than m.sub.2. In a more general unified field equation mc.sup.2 =Bvl coulomb, where m is a quantum mass contained within a string of length l, and q=unity as a result of a single coulomb being a fundamental resonant harmonic of charge. Be definition, a volt=energy per unit charge or E/q. Therefore, we may write E=Bvlq, while q=1, maintaining the integrity of q as a fundamental unit of charge. Therefore we may write the expression: total energy, expressed as E, is equal to Bvlq. Integrity of the units is seen as we reiterate the following: ##EQU7## An important consideration is the nonarbitrariness of the magnitude of a single coulomb. If the magnitude of a single coulomb is an arbitrary choice, then the foregoing would be erroneous. On the other hand, if the magnitude of a single unit of charge designated by definition to be a coulomb, is a nonarbitrary choice and indeed a fundamental harmonic of charge in resonance with varying charge harmonics, then the foregoing is absolutely correct. In this manner, the general unified field equation eliminates the necessity to delineate the particular charge of the mass given on the left side of the equation to be therein contained within the string line conductor l undergoing the electromagnetic interaction. This means that when the q in the general expression mc.sup.2 =Bvl coulomb is a single coulomb, resonant vibration of field induced within the string line conductor via the electromagnetic interaction will fundamentally jiggle masses which are resonant energy domains to the total energy production of the electromagnetic interaction. Within a plasma system, the framework designates that nuclei and electrons will be the fundamental mass units to be mechanically vibrated by electromagnetic interactions with very weak magnetic fields. The weak fields are an adjuvant to the strong magnetic fields necessarily employed. It is possible to consider variation of the g factor and r=l. Zeeman resonance and cyclotron resonance are equivalent to Jacobson resonance when vmax=c and r=l. It must be particularly noted that the general expression mc.sup.2 =Bvl coulomb describes a system wherein the g factor is electronic, i.e., g.sub.e =2. This distinction may be explained with the utilization of string theory. In string theory, the manifestation of a particle depends upon its internal state of vibration and its linear extension in space-time. Although the linear extension refers also to curvilinear or geodetic lines, the perception of a straight line is fundamentally relativistic. More specifically, the arc of a semicircle is a string with total length approximately 6.28 or pir, when r=2. When the string is closed into a full loop, the diameter is 2. The radius of the arc of the semicircle having a length 6.28 is 2, wherein the diameter of the closed loop is equal to 2. Thus r=l, l being the extension seen cross-sectionally in two dimensions. The diameter of the open arc of 6.28 is equal to 4. The electronic g factor describes a string which is manifested as an electron point mass when the loop is closed. The nuclear g factor describes a string manifested as a proton as the string is open into the arc of the semicircle, and as this arc is further extended linearly, a perceiver looking at the string from a two dimensional planar angle cross-sectionally sees a string approximately 5.6. This is because the arc string is open somewhat in between a totally extended linear state and the fundamental state of a semicircular arc wherein the diameter would be 4. Thus string theory explains the necessity for the variation of the electronic g factor to the nuclear g factor, i.e., the same string manifesting itself as two different fundamental particles, dependent upon the extension in space-time regulated by the internal state of vibration. The interstitial hidden string is a propitiator of the fusion reaction. The abstract reference points which create the metric of space-time are closed in General Relativity to the electromagnetic field, in fact to all matter. Yet we have seen those abstract points actually contain gravitational energy, and maintain in independent inertial system while taking part in the construction of the reality of the field itself. This paradoxical situation presented by nature may only be explained with hidden string, a connection of the substance of the field to the substance of that entity which is apparently ultimate to the field in quantum character. The question of the aether returns to haunt physics as we maintain our search of the connecting matter between the mass points that comprise string, and the connections between gauge particles. The question of the kinetic aether and relative closure of the universe then rests entirely upon the existence of hidden string. Repeating equation (5.), mc.sup.2 =Bvlq, and equation (11.), which is derived from (5.), B=m/qt, ##EQU8## Derived from the physical definitions (12.) and (13.), EQU 10.sup.4 gauss=Kg/(coulsec). (28) A single coulomb of charge contains: EQU 6.25.times.10.sup.18 e.sup.- 9.11.times.10.sup.-28 g=5.7.times.10-9 grams of matter. (29) EQU one gauss=1.75.times.10.sup.7 g/sec. (30) Most particularly, a single maxwell, the magnetic line of force, carries approximately: EQU 1.75.times.10.sup.7 gcm.sup.2 *s.sup.- 1. (31) Indeed, the single magnetic line of force, in a vacuum, carries about seventeen-and-a-half million grams of matter every second through a square centimeter of extension. Cross sectionally the plane is infinitesimally narrow as string. It is lucid that a kinetic aether of variance in dimensional quality must serve as our unseen source of hidden string. Therefore, every abstract reference point comprising the essential fabric of the metric of space-time is itself an intrinsic Galilean coordinate system. The foregoing considerations have practical application with respect to plasma confinement. The gravitational aether is only discoverable in terms of the potential to predict phenomena resulting from interactions which may be supposed to influence the aether and thereby to subsequently or concomitantly influence the relations of the electromagnetic field. Plasma physics presents the opportunity to examine the natural theory and number symmetry correlations, to verify that the kinetic aether (1) does really exist and (2) is not absolutely inertially independent but is relativistically so. With reference to FIG. 1, the Tokamak magnetic confinement apparatus, engages hot plasma gas of fusible fuel, i.e., deuterium and tritium. Fusion reactors of this type have thus far produced temperatures as high as 300 million degrees Kelvin for periods of up to a few seconds. Although the temperature is high enough, the time during which the necessary temperature and confinement may be maintained is inadequate for ignition of the plasma and the resultant Q greater than the 20, which is fairly typical of such a system. In a Tokamak which is the size of an auditorium, only about 2 grams of deuterium-tritium fuel are set to vaporize in a vacuum. Space-time within the framework of the toroidal magnetic confinement apparatus is crystallized in very regular patterns, in terms of the abstract points which make up the metric of intrinsic quality of space-time itself. Viewed from the perspective of this realm there is indeed little material comprising the electromagnetic field of the magnetic chamber. The rapidity of motion of the fusible material increases as the temperature increases. As the kinetic energy of the nuclei increases to above 100,000 electron volts something critical occurs. The criticality of the occurrence must be dependent upon the fact that the mechanistic structure of the electromagnetic field comprising the matter in the chamber creates not just lines of electrons, and discontinuities in said lines (popping out quasi-particles), but it in fact must squeeze the relativistic magnetic monopole intrinsic to the gravitational field outside the matter therein. A chain reaction ensues to move real ponderable bodies, however virtual and ghostlike they may be from the gravitational aether, to the electromagnetic field and vice versa, in perfectly symmetrical fashion. Thus we may create on a substructured level only with very weak magnetic fields as a quantum gravity, the equalization of material tension body of the aether. This kinetic, virtual interchange of gauge particles is the principal propitiator of ignition of controlled thermonuclear fusion. The regulator of the crystalline structure of the electromagnetic field itself is principally the quantum Hall effect and the relatives thereof, i.e., the cyclotron resonance effect, magnetic resonance and the piezoelectric effect. According to the invention, magnetic fields are set up wherein the toroidal magnetic confinement system is placed in a plane at right angles to the magnetic lines of force. A transverse Lorentz force is produced and is adjustable with variation in the field strength. The open circuit created in a transverse direction to the substantial plane of the toroidal confinement chamber and at right angles to extra poloidal electromagnets (set in resonance with nuclei and electrons), adjusts conditions in a homeostatic manner. This means that the internal gravitational strings of electrons and nuclei of a plasma will be virtually adjustable wherein the greater lateral movement of the particles to lower the plasma temperature by colliding with the walls of the container will be avoidable. Substantially, the electrons and nuclei that would have been lost to system without the extra poloidal weak intensity magnetic fields may be contained by the framework of the conductive mode of the body of the plasma, fundamentally necessary to establish and meet the Lawson criterion for particle density and confinement time. A Tokamak according to the invention, as shown in FIG. 1, has a toroidal confinement chamber 22, with a plurality of toroidal field coils 24. Poloidal coils 26 and ohmic heating coils 28 are included. However, in addition to these elements as required for basically confining and heating the plasma, the invention employs supplemental field generating coils 30. In the embodiment shown, two coils 30 defining produce supplemental fields at right angles to the plane of the toroidal confinement chamber 22, the coils 30 having an internal span or lumen sufficient to substantially encompass the toroidal vessel. The coils 30 are energized to provide weak magnetic fields at levels as calculated hereinafter, such that the additional electromagnetic fields produced by the supplemental poloidal coils 30 set the reactor in dual resonance with the gravitational energies of the electrons and nuclei which otherwise would have been lost to the system and uncontrollable. ##EQU9## This flux density B is obtained at the toroidal confinement vessel by means of one of the poloidal magnet coils 30. This supplemental field of the poloidal coils is set in resonance with deuterons. The Tokamak Fusion Test Reactor (TFTR) at Princeton has demonstrated an energy confinement time (r) of 0.4 sec at a peak electron density (n) of 1.times.10.sup.14 cm.sup.-3, for an n r of 4.times.10.sup.13 cm cm.sup.-3 sec at a temperature of 2.2 KeV, using deuterium pellet injection. Deriving B from mc.sup.2 =Bvl coulomb, using an approximation for the plasma circumference, shows nearly the same number with exponential reciprocal as n r experimentally derived. EQU mc.sup.2 =Bvl coulomb (34) ##EQU10## The second poloidal stabilizing magnet is energized at this level, namely the level required for tuning to electrons. The flux density in accordance with the dimensions of the reactor as indicated is 9.times.10.sup.-17 gauss. The n .lambda. for particles which are electrons must of course be reciprocally greater as indicated. ##EQU11## This length of 1.03.times.105 cm is a more appropriate circumference for the plasma, to prevent loss of temperature from lateral particle drift. The application of the field according to the preferred embodiment of the invention requires two additional poloidal magnetic coils 30, as indicated in FIG. 1, namely one for the deuterium nuclei and one for the electrons in the plasma. It is also possible to arrange supplemental toroidal coils 32, as shown in FIG. 2, to supplement the magnetic confinement and heating fields with tuned fields at a level calculated as disclosed herein to establish dual resonance of the electromagnetic and gravitational energies of the relevant particles. The very weak magnetic field associated with the deuteron mass is the steady magnetic field associated with the gyromagnetic ratio of the electron in the cyclotron resonance formula: EQU f.sub.c =qB/2m, (39) when f.sub.c is the frequency of fluctuation of the field of the sun. The supplemental field coil can be operated with a relatively larger number of turns and relatively lower voltage or a relatively lower number of turns and higher voltage, the objective being simply to provide a supplemental field at the noted flux density. The supplemental coils can be made of a semiconductor material such as germanium or silicon. FIG. 2 illustrates an embodiment wherein one secondary poloidal coil 30 is provided. The secondary coil defines a large solenoid 40, of sufficient dimensions to substantially encompass the fusion reactor. This secondary coil is operated to produce a magnetic flux density in the area of the plasma confinement vessel according to the relationship mc.sup.2 =Bvl coulomb, where the mass m is the mass of a particle in the plasma, particularly deuterium or tritium nuclei. The supplemental toroidal coils 32 can be tuned to one particle mass and the poloidal coil 30 to another particle mass. The invention having been disclosed, additional variations will become apparent to persons skilled in the art and aware of this disclosure. Reference should be made to the appended claims rather than the foregoing specification as indicating the true scope of the invention in which exclusive rights are claimed.
	summary
	abstract	In order to provide a boiling water type nuclear reactor use control rod with a guide use roller which improves corrosive environment at a clearance in the guide use roller and suppresses a generation of stress corrosion cracking while maintaining sliding function of the control rod by the guide use roller, at least one of a handle 5, a lower portion supporting plate 2a and a dropping speed limiter 2 is provided with the guide use roller, and a space which causes water flow in a clearance between a pin 9 and a pin hole 12 in the guide use roller is provided adjacent the clearance.
	summary
	description	The present invention relates to radiotherapy apparatus. The accurate delivery of radiotherapy to a patient depends on a number of factors, including the accurate determination of the patient's current position, in terms of both their gross external position and the position of the internal structures that are to be irradiated or avoided. Some form of investigative x-ray apparatus is therefore a valuable part of a radiotherapy apparatus. Given that the apparatus itself is capable of producing a beam of x-rays, it might be thought that this could be used as an investigative source. However, the therapeutic beam is typically at a high energy (in the MV range) and therefore the image contrast is poor and the dose delivered to the patient is relatively high. The poor contrast results from the attenuation coefficients that apply at higher energies as opposed to those that apply, at lower energies. At higher energies, the coefficients of bone and tissue are similar, thereby limiting the potential contrast that is obtainable. It is therefore desirable to use a lower energy beam for investigative purposes. Beams with energies in the kV range can be detected more easily, apply a lower dose to the patient, and interact mainly via the photoelectric effect. The latter effect is dependent on atomic number, and the large difference between bone (20Ca) and water (1H and 8O) therefore allows a much better image contrast. However, a separate source of kV x-rays presents various engineering difficulties. Such a source inherently adds additional cost and complexity to the apparatus. Further, spatial clearance requirements dictate that such sources view the patient along an axis that is offset by 90° from the therapeutic beam axis. Thus, as the therapeutic source is rotated around the patient, the diagnostic source is likewise rotated. These axes need to be aligned, and need to be kept in alignment. It is therefore desirable to achieve a co-incident investigative kV source for a therapeutic MV source—a so-called “beams-eye-view” source. However, this is not a trivial step. Galbraith (“Low-energy imaging with high-energy bremsstrahlung beams”, Medical Physics Vol. 16 No. 5, September/October 1989 pp 734-746) reported that simple replacement of the Tungsten or Copper target with a low-Z Carbon or Beryllium target allowed the production of a low-energy beam which could be used for diagnosis. Galbraith also noted that the electron beam will interact with the electron window to produce bremsstrahlung radiation which he was able to use for imaging. Accelerators typically operate by producing a high-energy beam of electrons; this is allowed to impinge on a target to produce x-rays. The electron beam moves from its vacuum enclosure to the atmosphere via an “electron window” in the enclosure, of Aluminium in Galbraith's case. Galbraith noted that in doing so, the beam produced x-radiation. Normally, this would be absorbed by the conventional treatment target, but without a target it is free for use in diagnosis. Galbraith's suggestion of the electron window as a target also left the hypothetical patient being irradiated with the main part of the electron beam. Galbraith concluded that manufacturers should incorporate diagnostic modes in future accelerators to allow for modification in this direction, as the application of the method to standard accelerators “would in general be a difficult task”. Flampouri et al. (“Optimisation of megavoltage beam and detector characteristics for portal imaging in radiotherapy”, PhD thesis, University of London, 2003) demonstrated the replacement of the conventional Tungsten or Copper target for an MV source with an aluminium target and the removal of the conventional flattening filter, to produce a low energy beam from the apparatus otherwise used to produce an MV beam suitable for imaging, including projection radiographs and CT imaging using the treatment machine. Zheng et al (“Simple Beamline Modifications for High Performance Portal Imaging”, 8th International Workshop on Electronic Portal Imaging, Brighton, UK, 29th Jun. to 1 Jul. 2004) reported the replacement of the conventional Tungsten or Copper target for an MV source with a graphite or aluminium target and the removal of the conventional flattening filter, to produce a low energy beam from the apparatus otherwise used to produce an MV beam. To allow for interchangeability of the target, however, the cassette carrying the standard and graphite or aluminium targets is located outside the vacuum enclosure, and therefore some distance from the source. Zheng does not discuss any interaction between the electron beam and the window, although he references Galbraith. The prior art described in the previous section is either concerned with the production of X-rays from the vacuum window suitable for imaging during electron therapy [Galbraith] or with the use of low-Z targets on which electrons impinge to produce X-rays suitable for imaging [Galbraith, Flampouri, Zheng]. To date, therefore, there does not appear to be a device able to switch easily between a therapeutic beam and a beam-eye-view diagnostic beam produced by the vacuum window and is therefore capable of offering good image resolution, high contrast images and low patient dose. The x-ray production method described herein consists of a thin electron/vacuum window, which acts as an X-ray transmission target for impinging electrons, combined with an electron beam absorber of lower atomic number than the material of the vacuum window. The electron window transmits a large proportion of the electron beam but is of a sufficient thickness that on average a relatively small proportion of the electrons energy is deposited and converted to useful bremsstrahlung radiation suitable for imaging applications. This is in contrast to a conventional imaging or therapy target, where all electrons are absorbed within the target. The lower atomic number electron beam absorber serves to remove the residual electrons transmitted through the vacuum window (which otherwise would result in unacceptable levels of patient skin dose). In addition, depending on the X-ray spectrum produced, a diagnostic filter can be included to reduce the skin dose by removing X-rays of energy approximately <30 keV. The present invention therefore provides a radiation source, comprising an electron gun, a pair of targets locatable in the path of a beam produced by the electron gun, the targets having different emission characteristics, and an electron absorber insertable into and withdrawable from the path of the beam. Generally, one of the targets will be thin and will also act as the vacuum window. In this way, a practical and realisable device is provided which is able to employ the principle of using the vacuum window for imaging enumerated by Galbraith in a manner that is safe and practical to use with patients. In the described embodiment, the targets are interchangeably locatable in the path, but other designs of radiation source may differ. In the current Elekta design, the electron gun is within an evacuated region and the therapy target is located in a wall portion of the vacuum chamber. Electrons accelerated by the gun impinge on the target and produce an x-ray beam outside the chamber. To move the apparatus out of its “therapy x-ray” mode into its “electron” mode, the target is moved to one side, out of the electron beam, and a Nickel electron window moves into position. We therefore propose to use the electron/vacuum window as an imaging target; therefore, in a preferred form of the present invention the electron gun is within a vacuum chamber, and the pair of targets are located at a boundary of the vacuum chamber. Thus, one target (imaging target/vacuum window) is preferably of Nickel or other suitable material (e.g. stainless steel, titanium), that can be formed into a relatively thin target, able to withstand the electron beam current, to act as a vacuum/air interface and of sufficient thickness to produce bremsstrahlung radiation but thin enough to transmit the bremsstrahlung photons so as not to be self absorbing. Such a target is capable of acting as an electron window (where desired) to allow the apparatus to produce a therapeutic electron beam. However, the atomic number properties of Nickel or other suitable material formed into a thin target will allow the production of a useful bremsstrahlung radiation. The other target (therapy target) can be a conventional x-ray target such as at least one of Copper, Tungsten, or a composite including Copper and Tungsten. The electron absorber, which is located outside the vacuum chamber and is used in conjunction with the imaging target only, preferably comprises a material of atomic number lower than the vacuum window, such as Carbon, Beryllium, Aluminium etc. In addition, the use of a diagnostic filter made of Aluminium or other suitable material can be included to reduce the skin dose in imaging mode. Most radiation sources of this type include a primary collimator, located in the beam subsequent to the targets. The electron absorber/insert can be located in the primary collimator or any other location suitably close to the vacuum window. Our current design includes a pair of alternative primary collimators, one associated with the x-ray therapy target and another associates with the Nickel electron window. We therefore prefer that there are a plurality of primary collimators interchangeably locatable in the path of the beam, at least one of which primary collimators contains the electron absorber. Such a radiation source can of course be included within a radiotherapy apparatus, to which the present invention further relates. In such apparatus, the radiation source is usually rotatable around a horizontal axis that lies in the path of the beam, a horizontal axis that is usually perpendicular to the beam. We prefer that there is also an electronic imaging system in the path of the beam, and (more preferably) a patient support between the source and the electronic imaging system. The latter may incorporate a flat panel imaging device, which can be optimised for a low energy x-ray source rather than the high energy for which a panel in this location is usually optimised. Panels based on scintillator crystals are therefore suitable. Current panels are based on Caesium Iodide, Gadolinium Oxisulphide or Cadmium Tungstate, but others may become available. Thus, preferred embodiments of the x-ray production method described herein consist of a thin vacuum window, which acts as an X-ray transmission target for impinging electrons, combined with an electron beam absorber of lower atomic number than the material of the vacuum window; the thin vacuum window produces a photon beam of energy suitable for imaging applications and the electron beam absorber serves to remove the electrons transmitted through the vacuum window (which otherwise would results in unacceptable levels of patient skin dose). In addition, depending on the X-ray spectrum produced, a diagnostic filter can be included to reduce the skin dose by removing X-rays of energy approximately <30 keV. The successful treatment of cancer with radiotherapy requires a large radiation dose to be deposited accurately in both position and intensity. To verify that the patient is in the correct position, portal images have traditionally been acquired throughout the patient's treatment. These images are produced using the megavoltage treatment beam and (unfortunately) suffer from inherently low contrast. This in turn limits the ability to position the patient accurately. An increase in accuracy could potentially lead to higher tumour control and/or lower normal tissue complication with the expectation of improved therapeutic benefit. Several methods for improving this situation have been proposed and fall into three categories. The first method involves changing the object properties, for example by inserting fiducial markers in the treatment region. Secondly, improvements to the imaging device can be made, and thirdly the imaging beam spectrum may be modified. The latter either involves attaching a kV source to the linac, integrating a kV source in the linac or introducing lower atomic number (Z) targets into a standard linac. In the last three cases the aim is to produce an imaging spectrum with a high proportion of photons between the energies of 40 and 200 keV. At these energies, the photo-electric interaction dominates, and thus bone and soft-tissue contrast is increased compared to standard MV images where Compton scatter dominates. This invention is based on employing a thin electron/vacuum window to act as an X-ray transmission target for impinging electrons, combined with an electron beam absorber of lower atomic number than the material of the vacuum window and possibly a diagnostic filter. This arrangement results in bremsstrahlung production with a significantly lower average energy than the treatment beam. The use of a thin, high Z detector can be used to image the lower energy section of the linac spectrum. It involves an arrangement of a linear accelerator for CT imaging using a beam modified to improve image quality by a combination of lowering the beam energy, modifying the x-ray target, and using the components of the linear accelerator to shape the beam and optimising a detector to image the beam. The implementation of a beam's-eye-view imaging system differs across the literature. Galbraith (1989) primarily used experimental techniques to produce high contrast images of thin objects using a thick low Z target. The images were acquired using film sensitive to energies in the diagnostic range. Ostapiak et al. (1998) and Tsechanski et al. (1998) investigated adjusting the thickness and composition of targets using Monte Carlo methods. They did not however investigate the full imaging system with Monte Carlo methods as in Flampouri et al. (2002). Flampouri et al. (2002) deduced the optimal target to be 6 mm of aluminium whilst Tsechanski et al. (1998) used 1.5 mm of copper. All the previous studies differ in the way the system was implemented. Of particular note is that different linac types and models were used in each study, which subsequently affected the positioning of the low Z target. Galbraith (1989) and Ostapiak et al. (1998) placed their targets as close to the electron window as possible, whilst Flampouri et al. (2002) and Tsechanski et al. (1998) placed the targets in the secondary filter carousel. Experimental Arrangement We have developed an optimum design for an imaging beam given that the lower-Z absorber should be placed as close as possible to the vacuum window, without a major re-design of the linac head. An Elekta Limited Precise™ treatment system linac (Elekta Limited, Crawley, UK) was modified by placing a low Z insert into the high energy collimator port. The insert consisted of 2 cm of carbon (density=1.8 g·cm-3) supported by an aluminium alloy cone that fixed to the high energy difference filter mountings on the bottom of the primary collimator. The thickness of the carbon insert was sufficient to stop all primary electrons emerging from the electron window. The carbon insert was placed in the primary collimator as this was the closest position it could be placed to the exit window of the waveguide. The linac was operated in 4 MeV electron mode with the primary and secondary scatter foils removed. The only items in the beam path were the nickel electron window, carbon insert, monitor ion chamber, mirror and Mylar cross hair sheet. To increase the dose rate from the linac the electron gun current was increased to match the current used in the high dose rate electron (HDRE) mode of the linac. This increases the beam current by a factor of 10, enabling images to be acquired in clinically acceptable times (circa 1 second). This beam current was used as linacs of this model had previously been life tested to this level. A schematic diagram of the top section of the linac (excluding Jaws and Multi-leaf collimator) can be seen in FIG. 1. This includes an electron path 10 leading to a Nickel electron window 12. After the primary scatter foil assembly 14, the resulting beam meets a 2 cm carbon filter/absorber 16 mounted in one of the rotatable primary collimators 18. The carbon filter/absorber 16 is supported in place by an aluminium holder 20 attached to the primary collimator 18. Below the primary collimator 18 is the secondary filter carousel 22 and then the ion chamber 24. Additional filters may also be placed, including the imaging bowtie filter (usually present in CT scanners to correct for beam intensity variations arising from patient geometry) and the use of collimators to shape the beam. These may be the normal collimation system of the treatment machine, such as multileaf collimators or conventional jaw collimators. The position of the electron absorber may be at one of various distances from the electron window, but is best placed close to the electron window to maintain a small focal spot and hence high spatial resolution. A tissue-equivalent phantom, Atlantis (Flampouri et al. 2002) was used as a quantitative measure of contrast of the different x-ray systems. The phantom consists of varying thicknesses of bone equivalent plastic surrounded by water. Three water depths were used; 5.8, 15.8 and 25.8 cm, so as to estimate contrast in the head and neck, torso, and pelvis respectively. The water depths are made up of 0.8 cm Perspex (density=1.03 g·cm-3) and the remainder is water e.g. 5.8 cm=5 cm water+0.8 cm Perspex. The spatial resolution of the system was assessed by analysing a PIPS pro phantom (Rajapakshe 1996) and images acquired of a humanoid anthropomorphic phantom for the head and neck for qualitative image assessment. Two in-direct amorphous silicon based detectors (Antonuk 2002) manufactured by PerkinElmer (Fremont, Calif., USA) were employed. The Elekta iViewGT electronic portal imager (EPID) and the Elekta XVI panel were also considered. The basic detector layers can be seen in FIG. 2 (which is not to scale) for the iViewGT panel (Parent et al. 2006). These are: The major difference between the XVI panel and the iViewGT panel is the omission of the copper plate and the substitution of the gadolinium oxisulphide scintillator for a columnar, thallium doped, Caesium Iodide (CsI(Th)) crystal. The iViewGT panel is normally used for imaging the megavoltage linac beam and the XVI panel is currently used on the Elekta Synergy system for imaging with kV photons. All panels were positioned in a standard megavoltage detector arm, resulting in a distance of 159 cm from the target to the panel surface. Images were acquired using the PerkinElmer x-ray imaging software (XIS) and the panels ran in free running mode i.e. not synchronized to the beam delivery. The iViewGT panel acquired images at 568 ms and the XVI panel at 142.5 ms. Both frame rates where chosen to avoid saturating the detectors during open field acquisitions, but to also give good dynamic range. All images were offset and gain corrected using equation 1 on a pixel by pixel basis. Icorrected is the gain and offset corrected image, Imeasured IS the image to be corrected, Igain is a 26×26 cm open field image and Ioffset is an image acquired when the panel is not being irradiated. I corrected ⁡ ( x , y ) = I measured ⁡ ( x , y ) - I offset ⁡ ( x , y ) I gain ⁡ ( x , y ) - I offset ⁡ ( x , y ) ( 1 ) The Low Z linac was characterised by obtaining depth dose curves and profiles in a water tank (Scanditronix-Wellhofer) using a CU500E controller unit and electrometer. The field and reference chambers were compact cylindrical ion chambers, type CC13 with a 0.13 cc sensitive volume (Scanditronix-Wellhofer). Depth dose curves and profiles were acquired for a 20×20 cm field, SSD=95 cm for both the 6MV and low Z beam using both Monte Carlo and experimental measurements. The two detectors described previously were modelled using DOSXYZnrc. A previously published model of the iViewGT panel was used (Parent et al. 2006). This was modified for the XVI panel i.e. removal of copper plate and modification of scintillator type and thickness. The image was taken as the dose deposited in the scintillator. Optical photon transport was not included as it was not expected to affect image properties in this case (Evans et al. 2006). To investigate the response of the panels to various input x-ray spectra the dose deposited in the scintillator layer of the detectors was simulated for various mono-energetic pencil beams. These beams were evenly spaced on a log 10 scale between 0.001 MeV and 10 MeV so as to sample adequately the response of the detectors over the range of energies in question. The contrast was calculated by analysing the average pixel value in each of the bone segments and using equation 2. I0cmbone is the average pixel intensity in the section of the Atlantis phantom with no bone insert (0 cm) and Ixcmbone, is the average pixel intensity in the section of the Atlantis phantom with an x cm bone insert. To negate errors associated with a tilted beam and to account for the un-flattened nature of the low Z beam, images of the Atlantis phantom where ‘flattened’ by dividing this image by one of the same water thickness but without the bone inserts. Contrast xcmbone = I 0 ⁢ cmbone - I xcmbone 0.5 * ( I 0 ⁢ cmbone + I xcmbone ) ( 2 ) FIG. 3 shows the results of Monte Carlo calculation of the electron energy fluence at various levels in a linac for 4 MeV electrons. It can be seen that shown that the electrons scatter substantially in air between the electron window and the secondary filter carousel. The electron fluence distribution is 8 cm wide at the secondary filter carousel and thus any image formed with a target at this level would suffer severe spatial resolution degradation. Therefore, to obtain high resolution images the absorber cannot be placed far from the vacuum window. The Monte Carlo model of the low Z linac shows a substantial photon fluence from the Nickel electron window. FIG. 4 shows that at the isocentre plane, 71% of the photon fluence is from primary photons produced in the nickel window. Table 1 shows the proportions in the central 5×5 cm of a 20×20 cm field. TABLE 1Energy Fluence contributions in a 5 × 5 cm square atSSD = 100 cm for the Low Z linac with a 20 × 20 cm fieldComponent% of photon energy fluenceNi electron window70.95Primary Collimator0.7Carbon absorber28.23OtherRemainder (0.12) Galbraith (1989) deliberately formed images using photons produced from an aluminium electron window in an AECL Therac-20 accelerator, but the contribution from such photons was not discussed in subsequent low Z papers (Flampouri et al. 2002, Ostapiak et al. 1998, Tsechanski 1998). The production of a significant photon fluence in the thin nickel window arises due to nickel's high atomic number (Z=28) and density (8.9 g·cm-3). As bremsstrahlung production is proportional to Z2, the efficiency of the process is greatly increased for the high Z, nickel window over the low Z, carbon insert. In our design the Carbon absorber acts primarily to remove primary electrons from the beam; as a by-product it also produces further low energy bremsstrahlung photons. It must be noted that the proportion of photons from the electron window will depend on the type of the linac used due to a variety of different materials and thicknesses being used by the linac manufacturer. FIGS. 5a and 5b show the depth dose curves and profiles for the low Z beam for the Monte Carlo simulations and experiment. Good agreement is seen between the Monte Carlo and experimental results suggesting that the model of the system is accurate. A slight tilt in the experimental beam is present as shown in FIG. 5b, and this is likely due to a small tilt in the carbon insert or due to the non-standard operating mode of the ion chamber and servo system. The latter is affected by the lack of secondary electrons normally generated in the flattening filter. This results in a lack of electronic equilibrium in the ion chamber. 6MV data is also shown highlighting the different dosimetric properties of the beams. For 20×20 cm fields the 6MV beam dmax is at 1.25 cm whilst it is 1.15 cm for the Low Z beam. Inherent contrast results calculated for the Atlantis phantom are shown in FIG. 6. Significant improvements in contrast are seen for all low Z beam systems over the standard 6MV/iViewGT system. For thin, 5.8 cm phantoms contrast for 1.6 cm bone increases by a factor of 2.42 with the LowZ/iViewGT system and by a factor of 4.62 with the LowZ/XVI setup. For thicker phantoms the improvement in contrast decreases but even with a 25.8 cm phantom a 1.3 times increase in contrast is noted with the low Z beam. The increase in contrast is due to two factors. Firstly the low Z linac produces a higher proportion of diagnostic x-rays than the 6MV linac and secondly that the different panels are sensitive to different regions of the photon spectrum. FIG. 7 illustrates the response of the different detectors as well as the different photon spectra produced by the low Z and 6MV linacs. At energies around the mean of the 6MV beam (1.6 MeV), the response of all detectors is very low whilst there are very few photons around 100 keV for the 6MV beam. Conversely the un-attenuated low Z beam has its peak fluence at or around the maximum response of the detectors. The Elekta iViewGT is less responsive than the XVI panel, owing to the thinner and hence less quantum efficient scintillator. The copper plate also limits the quantity of low energy photons that reach the scintillator. Due to the megavoltage nature of the low Z beam significant beam hardening occurs for thick phantoms. As the phantoms get thicker the beams are stripped of the low energy photons resulting in lower contrast images. This observation of very little contrast improvement for thicker phantoms has been noted previously (Flampouri et al. 2002, Galbraith 1989, Ostapiak 1998, Tsechanski 1998) and is therefore an inherent disadvantage of any megavoltage generated low Z beam. Table 2 presents the dose needed to form an image with the same Signal to noise ratio as the conventional 6MV/iViewGT system. The contrast value quoted is for 1.6 cm Bone in x cm water. Table 3 shows the imaging dose required to form an image with the same Contrast to Noise Ratio (CNR). TABLE 2Dose comparison for the low Z/XVI system when the SNRis kept the same as the standard 6MV/iViewGT system.% of6MVPhantomBeamSNRDoseDoseContrast5.8 cm water6MV/iViewGT96.352cGy100%0.0474LowZ/XVI96.350.1325cGy6.63% 0.219025.8 cm Water6MV/iViewGT68.892cGy100%0.0426LowZ/XVI68.890.4819cGy 24%0.0575 TABLE 3Dose comparison at a constant contrast to noise ratio.% ofPhantomBeamCNRDose6MV Dose5.8 cm water6MV/iViewGT21.392cGy 100%LowZ/XVI21.390.00901cGy0.45%25.8 cm Water6MV/iViewGT8.37042cGy 100%LowZ/XVI8.37040.272cGy13.6% Both sets of results show a significant dose saving for thin phantoms. A dose reduction of a factor of 14 is possible for a 5.8 cm phantom whilst still obtaining a 4.62 times increase in contrast. For the thickest phantom a dose saving of a factor of 3 and an increase in contrast of a factor of 1.3 is observed. Contrast to noise ratio calculations show that a further reduction in dose is possible for constant CNR. 0.5% of the dose is required for thin phantoms for the low Z beam compared to the 6MV system. For thicker phantoms we still require only 13.6% of the dose of the 6MV images for the Low Z system. Imaging times vary according to the phantom thickness due to the restricted beam current used for the low Z beam, to safeguard the electron window. For a 5.8 cm phantom, images with the same SNR as a 2cGy 6MV image can be acquired in 0.35 seconds. For a 25.8 cm phantom this increases to 1.27 seconds. These times are acceptable for portal imaging, but if quicker acquisitions were required for cone beam CT then the SNR would have to be sacrificed or a thicker scintillator with a high quantum efficiency (QE) employed. We also considered the spatial resolution that is achievable. The photon source of the low Z linac is a combination of photons emitted from the electron window and Carbon insert as shown in FIG. 8. For both the 6MV and low Z Monte Carlo simulations, the input electron spot size was the same. However due to the different positions of the targets the overall photon spot shape is slightly different. The 50% points are similar for the two systems but the Low Z beam has a broader tail around the 15% region. The broadening of the tails is due to the larger electron spot hitting the Carbon insert after passing through the nickel electron window and being scattered in a volume of air. This could be improved by moving the carbon insert/absorber closer to the nickel window. The spatial resolution of the whole system was assessed by measuring the MTF using the PIPS-pro phantom placed on a couch at SSD=105.8 cm. FIG. 9 shows the MTF's for the LowZ/XVI and 6MV/iViewGT systems. The LowZ/XVI system therefore performs better at higher frequencies resulting in sharper images. Whilst the detectors are similar, the presence of the copper plate on the iViewGT panel increases the size of the point spread function for the 6MV beam by scattering electrons and photons before they interact with the scintillator. Also the higher energy 6MV photons may scatter larger distances and can backscatter into the scintillator. On the other hand the secondary source of photons from the carbon insert in the low Z linac act to reduce the MTF as they broaden the low Z spot size. Analysis of the results of qualitative Phantoms showed that image quality is superior in the Low Z/XVI image, supporting the quantitative measurements described previously despite the image being formed with a lower dose. Teeth, oral cavity and spine are clearly visible in the LowZ/XVI image highlighting the superior contrast and preservation of spatial resolution. FIGS. 10 to 13 show a practical version of an Elekta treatment head incorporating the above ideas. They show part of the wall of a vacuum chamber 100 which incorporates an electron gun 102 (illustrated schematically) such as a linear accelerator. This wall 100 has an aperture 104 which is covered by a sliding carrier 106 that includes a Tungsten/Copper layered target 108 and an electron window 110. In one position, shown in FIG. 10, the carrier 106 is moved so that the target 108 covers the aperture 104. In another position, shown in FIG. 11, the carrier 106 is moved so that the electron window 110 covers the aperture 104. Immediately outside the chamber 100 is a primary collimator set 112. This set 112 includes a first primary collimator 114 and a second primary collimator 116 into which has been inserted a carbon absorber 118 held in place with Aluminium support struts 120. The carbon absorber 118 could of course be held in place by a variety of alternative means, such as by providing suitable recess. FIG. 14 shows such an arrangement, in which the primary collimator 116′ is re-shaped to include a wider diameter recess 148 and the carbon filter 118′ has a corresponding collar 150 so that it sits in the recess 148. The set 112 is indexable between two positions, akin to the sliding carrier 106, so that one primary collimator, of the two is presented in front of the aperture 104. If required a diagnostic filter could also be placed close to (or attached to) the electron absorber to reduce the patient skin dose from low energy photons (<30 keV). Beneath the primary collimator set 112, there is a motorised filter carousel 122. This is mounted on an axle 124 offset to one side beneath the aperture 106 and includes a plurality of filter recesses 126, 128. A first filter recess 126 is (in this case) empty although is could alternatively contain a conventional flattening filter. A second filter recess 128 contains a so-called “bow-tie” filter 130. Bowtie filters are used in CT (computed tomography) scanning for a variety of reasons, including to equalise the signal to noise ratio and to eliminate certain image artifacts etc. Generally, a bow-tie filter is used to compensate the X-ray attenuation for the different thickness regions in the patient, so that uniform X-ray intensity is produced at the detector. It allows a greater intensity to pass in a central region of the beam, progressively attenuating the beam more towards the outer edges. Below the bow-tie filter 130, there is an ion chamber 132 (FIG. 12) and a set of collimators generally indicated as 134. This can include elements such as multi-leaf collimators, block collimators, and the like, operating in one or more planes transverse to the beam. Below the collimators there will usually be a patient 136 supported on a patient table 138. Below the patient table is a flat panel scintillator detector 140 (as described above), mounted on an automated imager arm (not shown) which can extend the flat panel detector 140 into place or withdraw it, as required. As shown in FIG. 13, the entire radiation head 142 is mounted so as to be rotatable around a horizontal axis 144, taking the flat panel detector 140 with it. The patient 136 is supported on the patient table 138 so that the axis 144 is within the patient. The intersection of the axis 144 with the centre of the beam produced by the radiation head 142 is usually referred to as the “isocentre”. It is usual for the patient table 138 to be motorised so that the patient 136 can be positioned as required with the tumour site at or close to the isocentre. Thus, the electron gun 102 creates an electron beam 146 which is directed towards the aperture 104. The first configuration to consider is that shown in FIG. 10, in which the Cu/W target 106 covers the aperture 104 and the empty primary collimator 114 is beneath the aperture, followed by the empty filter holder 126 (or a flattening filter). In this arrangement, the electron beam will impinge on the target 108 and create a therapeutic beam of x-rays. These will be roughly collimated by the primary collimator 114 and then (optionally) flattened before being collimated to a desired shape by the main collimator set 134. Thus, a normal x-ray treatment is obtained. By moving the sliding carrier 106, the Cu/W target is moved out of the way of the electron beam and is replaced with the electron window 110. Provided that no other changes are made, the electron beam will then escape from the radiation head 142 and, after collimation, impinge on the patient. This mode is suitable for some treatments, particularly those involving the skin. If the primary collimator set 112 is also moved, then the alternative primary collimator 116 will be employed and the carbon (preferably graphite) absorber 118 will be placed in the path 146 of the electron beam. This will absorb the electrons and prevent them from reaching the patient. As a result, the only significant emission of the radiation head 142 will be the bremsstrahlung created by interaction of the electron beam and the Nickel electron window, which will then be acting as a target. Of course, this bremsstrahlung radiation was also created while the apparatus was operating in the electron treatment mode, but was a very low dose compared to the electron beam. The flat panel detector 140 can then be brought into the beam by extending the imager arm, to provide high contrast x-ray images of the patient using the low energy (kV) radiation produced by the radiation head 142. The motorised collimators 134, normally used for shaping the high energy (MV) therapeutic beam can then be used to shape the diagnostic beam. Thus, it is straightforward to automatically produce different imaging field sizes, removing the current need for different removable collimator cassettes in the kV beam. If the filter carousel is then also rotated in order to bring the bow-tie filter 130 into the path of the low-energy x-ray beam, to produce the arrangement shown in FIG. 11, then a beam that is highly optimal for cone beam CT scanning is obtained. The radiation head 142 and the flat panel detector 140 can be rotated around the patient 136 in order to obtain a good set of two-dimensional images for use in creating a cone beam CT image set. A low Z system has been implemented that produces superior images than that of the current 6MV/iViewGT combinations. The use of a highly quantum efficient detector optimised for the KV energy range results in a contrast improvement of a factor of 4.62 for thin (5.8 cm thick) phantoms and 1.3 for thicker 25.8 cm phantoms. Most importantly, significant dose savings have been noted suggesting this technique would be well suited for megavoltage CT. Such systems have hitherto been limited by the large dose required to acquire the projection images. The system offers a very simple modification to a standard linac coupled with a readily available imaging panel. Whilst the system is unlikely to compete with the dose and contrast results of gantry mounted kV systems, it offers a less complex solution and an image originating from the therapeutic portal of the linear accelerator. These advantages will, in practice, be more valuable. It will of course be understood that many variations may be made to the above-described embodiment without departing from the scope of the present invention.
053414071	description	DESCRIPTION OF THE SPECIFIC EMBODIMENTS I. THE TUBING STRUCTURE As used herein, the term "tubing" refers to a metal tube having various uses, and the term "fuel rod container" or simply "container" refers to tubing used in fuel rods to enclose fuel pellets. Sometimes the fuel rod container is referred to as "cladding" or "cladding tube". Referring to FIG. 1, a fuel element 14 (commonly referred to as a fuel rod) includes a fuel rod container 17 surrounding a fuel material core 16. The fuel element 14 is designed to provide excellent thermal contact between the fuel rod container 17 and the fuel material core 16, a minimum of parasitic neutron absorption, and resistance to bowing and vibration which is occasionally caused by flow of coolant at high velocity. The fuel material core is typically a plurality of fuel pellets of fissionable and/or fertile material. The fuel core may have various shapes, such as cylindrical pellets, spheres, or small particles. Various nuclear fuels may be used, including uranium compounds, thorium compounds and mixtures thereof. A preferred fuel is uranium dioxide or a mixture comprising uranium dioxide and plutonium dioxide. The container 17 is a composite cladding having a structure including a substrate 21, a zirconium barrier 22, and an inner layer or liner 23. The substrate forms the outer circumferential region of a cladding tube, the inner layer forms as inner circumferential region of the cladding tube, and the zirconium barrier is located therebetween. The substrate may be made from a conventional cladding material such as a stainless steel or zirconium alloy. Suitable zirconium alloys for the substrate preferably include at least about 98% zirconium, up to about 0.25% iron, up to about 0.1% nickel, and up to about 1.7% tin (all percents by weight). Other alloying elements may include niobium, bismuth, molybdenum, as well as various other elements used in the art. Most generally, any zirconium alloy with suitable corrosive resistance to BWR water and with sufficient strength and ductility may be employed. In a preferred embodiment of this invention, the substrate is Zircaloy-2 or Zircaloy-4. In other preferred embodiments, "Zirlo"--a zirconium based alloy containing about 1% tin, about 1% niobium, and less than about 0.2% iron--is employed. Other exemplary substrate alloys include zirconium/2.5% niobium, "NSF" alloys (about 1% tin, about 0.2-0.5% ion, about 0.05% nickel, about 0.6-1% niobium, and the balance zirconium), "Valloy" (about 0.1% iron, about 1.2% chromium, and the balance zirconium), and "Excel" or "Excellite" (about 0.3% niobium, about 0.3 molybdenum, about 1.2 to 1.5% tin, and the balance zirconium). Still other exemplary alloys include various bismuth-containing zirconium alloys such as those described in U.S. Pat. No. 4,876,064 issued to Taylor on Oct. 24, 1989. These alloys include, for example, (1) about 0.5 to 2.5 weight percent bismuth, (2) about 0.5 to 2.3 weight percent of a mixture of bismuth and tin plus about 0.5 to 1.0 weight percent of solute which may be niobium, molybdenum, tellurium, or mixtures thereof, or (3) about 0.5 to 2.5 weight percent of a mixture of tin and bismuth plus about 0.3 to 1.0 weight percent tellurium. In some preferred embodiments, the substrate will have a microstructure (i.e. precipitate size distribution) that resists corrosion and/or crack propagation. It is known that the microstructure of Zircaloys and other alloys can be controlled by the anneal temperature and time as well as other fabrication parameters. It is also known that in boiling water reactors (BWRs), smaller precipitates generally provide superior resistance to corrosion while in pressurized water reactors (PWRs), larger precipitates generally provide improved resistance to corrosion. In either environment, coarse precipitates provide improved resistance to axial crack propagation. In a preferred embodiment, the substrate will have a dense distribution of fine precipitate (e.g., between about 0.01 and 0.15 micrometers in diameter) in the outer circumferential region and a less dense distribution of coarse precipitates (e.g., between about 0.2 and 1 micrometers in diameter) in the interior circumferential region. This embodiment will be especially preferred in BWRs. In PWRs, preferred substrates will have coarse precipitates distributed throughout. Detailed discussions of Zircaloy microstructure and methods of fabricating cladding having a desired microstructure are found in U.S. patent application Ser. No. 08/052,793 entitled ZIRCALOY TUBING HAVING HIGH RESISTANCE TO CRACK PROPAGATION and U.S. patent application Ser. No. 08/052,791 entitled METHOD OF FABRICATING ZIRCALOY TUBING HAVING HIGH RESISTANCE TO CRACK PROPAGATION, both of which were filed on Apr. 23, 1993, assigned to the assignee hereof, and are incorporated herein by reference for all purposes. Metallurgically bonded on the inside surface of substrate 21 is the zirconium barrier 22. The barrier, together with the inner liner, shields the substrate from the nuclear fuel material inside the composite cladding. Fuel pellet-induced stress may be introduced by, for example, swelling of the pellets at reactor operating temperatures so that the pellet presses against the cladding. In effect, the zirconium barrier deforms plastically to relieve pellet-induced stresses in the fuel element during swelling. The barrier also serves to inhibit stress corrosion cracking and protects the cladding from contact and reaction with such impurities and fission products. The zirconium barrier maintains low yield strength, low hardness, and other desirable structural properties even after prolonged use because it is resistant to radiation hardening. In preferred embodiments, the thickness of the barrier layer is between about 50 and 130 micrometers (approximately 2.5 mils) and more preferably between about 75 and 115 micrometers (approximately 3.2 to 4.7 mils). In a typical cladding, the zirconium barrier forms between about 5% to about 30% of the thickness or cross-section of the cladding. Generally, the zirconium barrier layer may be made from unalloyed zirconium possessing the desired structural properties. Suitable barrier layers are made from "low oxygen sponge" grade zirconium, "reactor grade sponge" zirconium, and higher purity "crystal bar zirconium". Generally, there are at least 1,000 parts per million (ppm) by weight and less than about 5,000 ppm impurities in sponge zirconium and preferably less than 4,200 ppm. Oxygen is preferably kept within the range of about 200 to about 800 ppm. Other typical impurity levels include the following: aluminum--75 ppm or less; boron--0.4 ppm or less; cadmium--0.4 ppm or less; carbon--270 ppm or less; chromium--200 ppm or less; cobalt--20 ppm or less; copper--50 ppm or less; hafnium--100 ppm or less; hydrogen--25 ppm or less; iron--350 ppm or less; magnesium--20 ppm or less; manganese--50 ppm or less; molybdenum--50 ppm or less; nickel--70 ppm or less; niobium--100 ppm or less; nitrogen--80 ppm or less; silicon--100 ppm or less; tin--50 ppm or less; tungsten--100 ppm or less; titanium--50 ppm or less; and uranium--3.5 ppm or less. Sponge zirconium is typically prepared by reduction with elemental magnesium at elevated temperatures at atmospheric pressure. The reaction takes place in an inert atmosphere such as helium or argon. Crystal bar zirconium is produced from sponge zirconium by converting the zirconium metal in sponge zirconium to zirconium tetraiodide vapor and then decomposing the iodide on an incandescent wire. Crystal bar zirconium is more expensive than sponge zirconium, but has few impurities and has greater resistance to radiation damage. Metallurgically bonded to the inside surface of the zirconium barrier 22 is the inner liner 23. As shown, the inner liner is the portion of the composite cladding closest to the nuclear fuel material 16. This layer protects the zirconium barrier from rapid oxidation should the fuel element interior come in contact with steam. Thus, the inner liner should be a relatively corrosion resistant material such as Zircaloy. For purposes of this invention, however, the inner liner should be softer than conventional Zircaloy so that crack initiation and propagation on the inner surface of the cladding tube are minimized. Although the inner liner should be softer than conventional Zircaloy, it is preferably harder than the zirconium barrier. This permits the tube to be machined, honed, etc. more easily than the softer unalloyed zirconium. Thus, the inner layer of this invention provides the additional benefit of permitting various fabrication steps to be performed more easily than is possible with a naked zirconium barrier. The inner liner can be formed from a variety of zirconium alloys. Suitable alloys should be resistant to corrosion in steam at 300.degree.-400.degree. C. and relatively soft in comparison to conventional Zircaloys. Many zirconium alloys of specified composition meet these criteria. Generally, alloys containing low concentrations of alloying metals (e.g. Cr, Ni, Nb, Sn) and/or oxygen will be softer. However, care should be taken in reducing the alloying elements to levels that might substantially diminish the corrosion resistance of the alloy. One preferred class of zirconium alloys has a relatively low tin concentration in comparison to corresponding structural alloys (e.g. Zircaloys used in cladding substrates). Preferred low-tin inner liner compositions will be zirconium alloys having less than about 1.2% tin by weight. More preferably, the alloys will have between about 0.3 to 1.2% tin, and most preferably about 0.8% tin. One class of suitable alloys include at least about 98% zirconium, up to about 0.24% iron and less than about 1.2% tin (all percents by weight). Some liner alloys will also contain between about 0.05 and 0.15 chromium and/or between about 0.03 and 0.08 nickel. Other additives may include niobium, bismuth, and molybdenum, as well as various other elements used in the art. Examples of suitable alloys from this class include low tin modified Zircaloys. Preferably, the tin concentration in such modified Zircaloys will be between about 0.5 and 1.2% by weight, and more preferably between about 0.8 and 1.0% by weight. In two specific preferred embodiments the tin contents in the modified Zircaloys are about 0.8% and about 1.0% by weight, respectively. In other preferred Zircaloys, the concentration of iron in the alloy will be reduced. For example, a modified Zircaloys-2 will contain less than about 0.12 percent iron, and we believe preferably between about 0.02 and 0.1% iron by weight. A modified Zircaloy-4 will contain less than about 0.2% iron, and we believe preferably between about 0.02 and 0.12% iron by weight. Because iron, as well as nickel and chromium, can provide some corrosion resistance, its concentration preferably will not be lowered to the point where corrosion resistance is significantly compromised in the modified Zircaloys. Other preferred zirconium alloys have reduced oxygen concentrations. Generally, lower oxygen contents in the liner alloy translates to greater resistance to cracking. In commercially available Zircaloy, the oxygen concentration is made purposely high, about 1000 ppm by weight, so that the Zircaloy is sufficiently strong to withstand the stresses encountered by a cladding tube. Because the inner liners of the structures of this invention need not be particularly strong, the oxygen content of these liner can be reduced to values substantially below that of conventional structural alloys. Zircaloy inner liners of the present invention therefore preferably contain less than about 1000 ppm, more preferably less than about 800 ppm, and most preferably less than about 600 ppm oxygen by weight. Of course, the hardness of other, non-Zircaloy, zirconium alloys can be reduced by decreasing the oxygen and tin concentrations. In addition to the modified Zircaloys described above, relatively soft and corrosion resistant zirconium alloys suitable for the inner liners of this invention include the dilute iron-chrome alloys, the Zirlos (as described above), and modified versions of these alloys having reduced tin and oxygen contents. Dilute iron-chromium zirconium alloy liners preferably contain about 0.07 to 0.24% iron and about 0.05 to 0.15% chromium by weight. One example of such alloy includes about 0.1% iron, about 0.05% chromium, and/or about 0.04% nickel. Such alloys are described in U.S. patent application No. 08/011,559 (filed on Feb. 1, 1993, naming Rosenbaum, Adamson, and Cheng as inventors, and assigned to the assignee of this application). Still other suitable alloys are the bismuth containing zirconium alloys disclosed in U.S. Pat. No. 4,876,064 (containing between about 0.5 and 2.5 weight % bismuth as discussed above in connection with the substrate). Preferably, the bismuth-containing alloys will be relatively soft. Thus, they will often have relatively low tin and/or oxygen contents. The inner liner should be sufficiently thin that microcracks are prevented from reaching critical depth. If a crack in the inner liner exceeds the critical depth, it could propagate beyond the inner liner and into the barrier and even the substrate. The critical depth varies depending upon the particular alloy from which the inner liner is made. In general, so long as the inner layer can maintain its corrosion resistance, thinner layers are preferred. The critical depth for modified Zircaloy inner liners of this invention is less than about 30 micrometers, and preferably less than about 20 micrometers. With some fabrication methods, it may be impractical to produce liners thinner than about 10 micrometers. Thus, the inner liner thickness will often be limited to between about 10 and 20 micrometers thick. It should be recognized, however, that thinner layers can be produced with slightly modified fabrication methods such as those employing vapor deposition techniques. In one example, the cladding tube total thickness is about 700 micrometers (approximately 28 mils), of which the inner liner or layer occupies less than 15 micrometers (approximately 0.6 mils) and the zirconium barrier occupies about 75 to 115 micrometers (approximately 3.2 to 4.7 mils). Referring now to FIG. 2, a cutaway sectional view of a nuclear fuel bundle or assembly 10 is shown. The fuel bundle is a discrete unit of fuel containing many individual sealed fuel elements or rods R each containing a cladding tube of this invention. In addition, the fuel bundle consists of a flow channel C provided at its upper end with an upper lifting bale 12 and at its lower end with a nose piece L and lower lifting bale 11. The upper end of channel C is open at 13 and the lower end of the nose piece is provided with coolant flow openings. The array of fuel elements or rods R is enclosed in channel C and supported therein by means of upper tie plate U and lower tie plate (not shown). Certain of the fuel rods serving to "tie" the tie plates together--thus frequently being called "tie rods" (not shown). In addition, one or more spacers S may be disposed within the flow channel to hold the fuel elements in alignment with one another and the flow channel. During the in service life of the fuel bundle, the liquid coolant ordinarily enters through the openings in the lower end of the nose piece, passes upwardly around fuel elements R, and discharges at upper outlet 13 in partially vaporized condition. Referring now to FIG. 3, the fuel elements or rods R are sealed at their ends by end plugs 18 welded to the fuel rod container 17, which may include studs 19 to facilitate the mounting of the fuel element in the fuel assembly. A void space or plenum 20 is provided at one end of the element to permit longitudinal expansion of the fuel material 16 and accumulation of gases released by the fuel material. A getter (not shown) is typically employed to remove various deleterious gases and other products of the fission reaction. A nuclear fuel material retainer 24 in the form of a helical member is positioned within space 20 to provide restraint against axial movement of the pellet column during handling and transportation of the fuel element. An important property of the composite cladding of this invention is that the foregoing improvements are achieved with a negligible to moderate neutron penalty (depending on choice of barrier material). Such a cladding is readily accepted in nuclear reactors since the cladding would have minimal eutectic formation (depending on choice of barrier material) in the substrate portion of the cladding during a loss of cooling accident or an accident involving the dropping of a nuclear control rod. Further, the composite cladding has a very small heat transfer penalty in that there is no thermal barrier to transfer of heat such as results in the situation where a separate foil or liner is inserted in a fuel element. Also the composite cladding of this invention is inspectable by conventional non-destructive testing methods during various stages of fabrication. In addition to the foregoing, because zirconium and the zirconium alloy are selected for the structure, the inside and outside surfaces of the composite cladding are compatible with manufacturing processes for light water nuclear reactor cladding and this enables the use of current manufacturing procedures, lubricants, etchants, etc. MANUFACTURE OF THE TUBING Various methods can be used to fabricate the cladding tubes of this invention. Suitable methods should produce sufficient cross diffusion between the substrate and the metal barrier and between the metal barrier and the inner liner to form metallurgical bonds, but insufficient cross diffusion to alloy with the metal barrier itself. Typically, the barrier and inner liner are provided as cylindrical tubes or sleeves that are bonded to the inside surface of a hollow zirconium alloy billet (which forms the substrate in the final cladding). Preferably, the components are bound to one another by coextrusion, but other methods may be employed. For example, the components can also be bonded to the billet by hot isostatic pressing or explosive bonding. In another method, the barrier and inner liner sleeves are bonded to the billet inner surface by heating (such as at 750.degree. C. for 8 hours) to give diffusion bonding between the tubes and the billet. Prior to bonding (by, for example, extrusion), the barrier and inner liner sleeves preferably are joined to the billet at their ends by a bonding process such as electron beam welding in a high vacuum. Electron beam welding is a conventional process in which an electron beam is used to heat the ends of the cylindrical tubes until they fuse. Extrusion is accomplished by putting the tube through a set of tapered dies under high pressure at about 1000.degree. to 1400.degree. F. (about 538.degree. to 760.degree. C.). Suitable extruders are available from Mannessmann Demang, Coreobolis, Pa. After extrusion, the composite is subjected to a conventional annealing and tube reduction processes to produce a product known as a "tubeshell" which is available in specified dimensions and compositions from various vendors such as Teledyne Wahchang (Albany, Oreg. USA), Western Zirconium (A Westinghouse company of Ogden, Utah), and Cezus (France). To obtain the final tubing of the necessary dimensions, various manufacturing steps such as cold-working, heat treating, and annealing may be employed. The equipment and operating conditions necessary to carry out these various steps will be readily apparent to those of skill in the art, and are described in U.S. patent application Ser. No. 08/091,672 entitled METHOD FOR MAKING FUEL CLADDING HAVING ZIRCONIUM BARRIER LAYERS AND INNER LINERS which was filed on Jul. 14, 1993, the same day as the instant application, is assigned to the assignee hereof and is incorporated herein by reference for all purposes. One suitable method of tube reduction involves three passes of about 65 to 80% cold work (conducted with a Pilger mill) followed in each case by a stress relief or recrystallization anneal. A specific preferred process according to this invention is now described. It should be understood that although the conditions described in this example are quite specific, each step of the process could be conducted under a range of conditions. The process is started with a hollow Zircaloy billet of approximately six to ten inches in diameter and two feet in length. The billet will form the substrate of a structure by the end of the process. At that point, the billet will be converted to about 400 feet of tubing having about a one-half inch outer diameter. First, the billet is rapidly quenched. Generally, the quench involves heating the billet above about 1000.degree. C., and then rapidly cooling from 1000.degree. C. to about 700.degree. C. by immersion in a tank of water. The quench rate is important between 1000.degree. C. and 700.degree. C.; after 700.degree. C. is reached, however, the rate of cooling can be increased or decreased as desired. Next, a tube of the metal selected to be the zirconium barrier is inserted into the hollow billet of the material selected to be the substrate, and a tube of the material selected to be the inner liner is inserted into the metal barrier tube. The ends of the billet, barrier, and inner liner tubes are then bonded by electron beam welding as described above. The welded tube is extruded with the tube temperature being at about 570.degree. C. to a diameter of about 3 inches. The extruded tube is further annealed and cold worked to produce a tubeshell of about 2.5 inches in diameter. The tubeshell--which has a zirconium barrier and inner liner bonded therein--is subjected to a first of three cold work passes. The tubeshell is passed through a pilger mill. It will be understood by the reader that pilger mills are generally available, albeit fairly complicated, pieces of equipment. During cold working with a pilger mill, a shaped die is rolled on the outside of the tube while a hard tapered mandrel supports the inside of the tube. In this manner, the wall thickness and diameter of the tube are simultaneously reduced. Typically about 69% cold work is performed in the first pass. This percent value is roughly analogous to the percent reduction of the wall thickness. If the tube is given any more cold work without stress relief, it may likely crack during manufacture. To relieve the stress caused by cold working, the tube is annealed at about 593.degree. C. for two hours in a large vacuum annealing furnace such as is available from Centorr Vacuum Industries, located in Nashua, N.H. Next, the tube is heat treated at about 927.degree. C. on the outer 30% of the wall. This is accomplished by heating the tubeshell with a high-energy or frequency (from an induction coil) which penetrates about 33% of the wall. During the induction heating water flows through the tube center. This serves two purposes: first it maintains the interior of the tube at a lower temperature while the outer region is heated, and second it very rapidly quenches the entire tube when the heating energy is removed. It is important to recognize that the inner portion of the tubeshell is not substantially heated. Further details of the induction heating process are provided in U.S. Pat. No. 4,576,654 to Eddens which is incorporated herein by reference for all purposes. This selective heating step imparts corrosion resistance to the outer region of the substrate by producing fine precipitates therein. Regarding the cooling of the tube, any fluid which is generally inert with respect to the zirconium alloy or barrier material can be used. For example, a gas coolant, water, or even stream can be used in such a process. At this point, a second pass cold work is performed (this time to about 74%) with a pilger mill. To remove the stress induced by this second pass cold work step, another anneal (again at 593.degree. C. for about 2 hours) is performed. Finally, the third pass cold work is performed as before. This reduces the tube to its final size--about one-half inch outer diameter with a nominal wall thickness of roughly 30 mils. This tube is cut up into lengths for fuel rods (i.e. about 14 feet long) and given a final recrystallization anneal at 577.degree. C. for about two hours. Alternatively, the final anneal could be a stress relief anneal conducted at any temperature between about 480.degree. C. to 577.degree. C. After the final anneal, the tube is ready for use in the reactor. It will be recognized by those of skill in the art that various steps are performed in addition to those listed in the above processes. For example, chemical etching is employed to remove superficial defects caused by the tube reduction mill. Further, straightening of tubes is often performed with pieces of equipment designed for this purpose. In addition, various nondestructive tests such as corrosion tests and ultrasonic tests for crack imperfections in the surface are performed. This is not an exhaustive list, but merely serves to describe some steps which may be employed. The composite tubing of this invention can be used to make nuclear fuel elements by first affixing a closure to one end of the tubing so that only one open end remains. The completed fuel element is prepared by filling the cladding container with nuclear fuel material, inserting a nuclear fuel material retaining means into the cavity, applying a closure to the open end of the container leaving the cavity in communication with the nuclear fuel, and then bonding the end of the clad container to the closure to form a tight seal therebetween. CONCLUSION Although the foregoing invention has been described in some detail for purposes of clarity of understanding, it will be apparent that certain changes and modifications may be practiced within the scope of the appended claims. For instance, although the specification has described preferred zirconium alloy tubes, other shapes may be used as well. For example, plates and metal sections of other shapes may also be used. The Zircaloys and other alloys described above are examples of alloys that can advantageously be used as tubing in the present invention. Some other zirconium-based alloys as well as certain other metal alloys having similar structures can in many instances also employ the structure described herein to resist damage to the fuel side of the cladding.
	description	This application is a divisional of U.S. patent application Ser. No. 13/946,516, filed Jul. 19, 2013, which is a continuation of International Application No. PCT/EP2012/050533, filed on Jan. 14, 2012, German Patent Application No. 10 2011 002 953.2, filed on Jan. 21, 2011, and U.S. Provisional Application No. 61/434,869, also filed on Jan. 21, 2011, the entire disclosures of which are incorporated herein by reference in their entireties. The present invention relates to a substrate for a mirror for Extreme-Ultraviolet (EUV) lithography comprising a base body and also to a mirror for an EUV projection exposure apparatus comprising such a substrate. In order to make it possible to create ever finer structures using lithographic methods during the production of semiconductor components, for example, use is made of light having an ever shorter wavelength. If light in the extreme ultraviolet (EUV) wavelength range is used, for instance at wavelengths of between about 5 nm and 20 nm, it is no longer possible to use lens-like elements in transmission, but instead illumination and projection objectives are fashioned from mirror elements with highly reflective coatings which are adapted to the respective operating wavelength. In contrast to mirrors in the visible and ultraviolet wavelength ranges, it is also the case in theory that maximum reflectivities only of less than 80% can be achieved per mirror. Since EUV projective devices generally have a plurality of mirrors, it is necessary for each of these to have the highest possible reflectivity in order to ensure sufficiently high overall reflectivity. In order both to keep losses in intensity as a result of stray radiation as low as possible and to avoid imaging aberrations, mirror substrates or mirrors which are produced by applying a highly reflective layer to the mirror substrate should have the lowest possible microroughness. The root mean squared (RMS) roughness is calculated from the mean value of the squares of the deviation of the measured points over the surface with respect to a central area, which is laid through the surface such that the sum of the deviations with respect to the central area is minimal. Particularly for optical elements for EUV lithography, the roughness in a spatial frequency range of 0.1 μm to 200 μm is particularly important for avoiding negative influences on the optical properties of the optical elements. It is an object of the present invention to provide mirror substrates which are suitable as substrates for mirrors used at wavelengths in the EUV wavelength range. This object is achieved, according to one aspect, by a substrate for a mirror for EUV lithography comprising a base body, characterized in that the base body is made of a precipitation-hardened alloy, preferably a precipitation-hardened copper or aluminum alloy. During the precipitation hardening, an alloy is subjected to heat treatment in order to increase the hardening strength thereof. During the heat treatment, metastable phases are precipitated in finely distributed form such that they form an effective obstacle to dislocation movements. As a result, the long-term stability or within certain limits the temperature stability of the structure of the base body can be increased further. The precipitation hardening is usually carried out in three steps. In a first step, which is also referred to as solution annealing, the alloy is heated until all the elements which are needed for precipitation are present in solution. In order to obtain the purest possible distribution of the mixed phase, the temperature should be chosen to be very high, but not so high that individual constituents of the microstructure melt. After the solution annealing, quenching can prevent fusion and thus precipitation of coarse particles. The solid solution remains in a metastable, supersaturated single-phase state. By subsequent heating to temperatures which are low compared to the solution annealing, the supersaturated single-phase solid solution is converted into a two-phase alloy. The phase which is predominantly cohesive and generally arises in a higher proportion is called matrix, and the other phase is called precipitation. Since many nuclei were formed during the preceding quenching, many small precipitations which are distributed homogeneously in the microstructure and increase the structural strength are formed. It is advantageous for substrates and mirrors on the basis of a base body made of precipitation-hardened alloys to be used at temperatures which lie considerably below the solution annealing temperature, preferably below the precipitation temperature. In a further aspect, the object is achieved by a substrate for a mirror for EUV lithography comprising a base body, wherein the base body is made of an alloy having a composition which, in the phase diagram, lies in a region which is bounded by phase stability lines. Alloys having such compositions have the advantage that any segregation processes can be stopped entirely by heat treatments, and therefore said alloys then have an increased high-temperature strength. This substrate has an increased long-term stability, as a result of which it is possible to ensure that the roughness values change as little as possible throughout the service life of an EUV projection exposure apparatus comprising mirrors based on this substrate. Particularly in the case of mirrors which are arranged further to the rear in the beam path, for example in the projection system, where they are exposed to lower thermal loading, it is possible to ensure that the roughness values remain constant over long periods of time. The alloy is preferably an alloy with a substitution lattice. In the case of substitution lattices, alloying components having a relatively low concentration are incorporated into the lattice structure of the component having the highest concentration, such that the lattice strength is further increased. This increases the structural stability given an increase in temperature and in particular over long periods of time. It is particularly preferable for the alloy to be precipitation-hardened. During the precipitation hardening, an alloy is subjected to heat treatment in order to increase the hardening strength thereof. During the heat treatment, metastable phases are precipitated in finely distributed form such that they form an effective obstacle to dislocation movements. As a result, the long-term stability or within certain limits the temperature stability of the structure of the base body can be increased further. The precipitation hardening is usually carried out in three steps. In a first step, which is also referred to as solution annealing, the alloy is heated until all the elements which are needed for precipitation are present in solution. In order to obtain the purest possible distribution of the mixed phase, the temperature should be chosen to be very high, but not so high that individual constituents of the microstructure melt. After the solution annealing, quenching can prevent fusion and thus precipitation of coarse particles. The solid solution remains in a metastable, supersaturated single-phase state. By subsequent heating to temperatures which are low compared to the solution annealing, the supersaturated single-phase solid solution is converted into a two-phase alloy. The phase which is predominantly cohesive and generally arises in a higher proportion is called matrix, and the other phase is called precipitation. Since many nuclei were formed during the preceding quenching, many small precipitations which are distributed homogeneously in the microstructure and increase the structural strength are formed. It is advantageous for substrates and mirrors on the basis of a base body made of precipitation-hardened alloys to be used at temperatures which lie considerably below the solution annealing temperature, preferably below the precipitation temperature. In particularly preferred embodiments, the alloy is a copper alloy or an aluminum alloy, very particularly preferably a precipitation-hardened copper alloy. Copper alloys in particular can be readily cooled, and it is therefore possible to ensure that the operating temperature during the EUV lithography is sufficiently low, in particular in the case of precipitation-hardened alloys, in order to be able to prevent structural changes. In addition, it is possible to obtain high strengths both in the case of copper alloys and in the case of aluminum alloys even at temperatures considerably above room temperature. In a further aspect, the object is achieved by a substrate for a mirror for EUV lithography comprising a base body, wherein the base body is made of a particulate composite. Particulate composites likewise have a high strength or structural stability. As a result, they are likewise highly suitable for use in mirror substrates for EUV lithography, in particular for long-term applications. Particulate composites have dispersoids which are insoluble in a matrix. It is preferable for the dispersoids to be made of ceramic material, in particular of oxides, carbides, nitrides and/or borides. In a manner similar to the precipitations in the precipitation hardening, the dispersoids form obstacles for dislocation movements within a matrix, in particular when they are present in finely distributed form. It is preferable for the particulate composite to have spheroidal dispersoids. It is thereby possible to reduce the stress or distortion energy in the particulate composite, which can lead to a higher high-temperature strength. Dispersoids having a spheroidal geometry can be obtained by particular soft-annealing processes. By way of example, it is possible to carry out soft-annealing processes in which the material is held for one to two hours at a temperature at which the basic phase of the matrix of the particulate composite is stable, whereas other phases in solutions go just into solution. Then, the temperature of the material is fluctuated repeatedly around this temperature range, and subsequently the material is slowly cooled at about 10° C. to 20° C. per hour. Such temperature treatments can be carried out with the alloys described above such that any precipitations are spheroidized, in particular in the case of precipitation-hardened alloys. It has proved to be particularly advantageous for the particulate composite to have dispersoids of an extent of between 1 nm and 20 nm. It is thereby possible to achieve particularly good strengths and at the same time to minimize a negative influence on microroughness values. In preferred embodiments, the particulate composite has a metallic matrix, this particularly preferably being a copper matrix or an aluminum matrix. Examples of suitable dispersoids in this case are titanium carbide, aluminum oxide, silicon carbide, silicon oxide or carbon in a graphite or diamond modification. In further preferred embodiments, the particulate composite has a ceramic matrix, in particular a silicon or carbon matrix. In this case, silicon carbide particles, in particular, have proved to be suitable as dispersoids. In a further aspect, the object is achieved by a substrate for a mirror for EUV lithography comprising a base body, wherein the base body is made of an intermetallic phase of an alloy system. Intermetallic phases are materials with a high strength and a high melting temperature. By way of example, they are used in aircraft engines or exhaust-gas turbochargers. In structural terms, the elementary cells of these special alloys have a high valence electron density. As a result, they have a covalent bond fraction which is high for metals and thereby have a particularly high lattice strength. It has been found that, in addition to a high specific strength and high melting temperatures, intermetallic phases overall have a high thermal stability with low diffusion coefficients and a high creep strength. These properties can ensure that, even under high thermal loading, as can occur for example in the case of mirrors which are arranged further forward in the beam path in an EUV projection exposure apparatus, in particular in the illumination system of an EUV projection exposure apparatus, the substrate experiences as little change as possible even over relatively long periods of time, and as a result properties such as the microroughness also remain as constant as possible. It is advantageous for the base body to be made of an intermetallic phase in which the stoichiometric standard composition is observed. In other words, preference is given to intermetallic phases with a composition having integer indices. Particular preference is given to intermetallic phases having the smallest possible elementary cells. It is thereby possible to further reduce the probability of mixed phases arising as the temperature increases. As a result of the occurrence of appropriate precipitations, for example at grain boundaries, mixed phases of alloys having a differing structure could lead to an increase in microroughness, which could impair the optical quality of a mirror comprising such a substrate. In particularly preferred embodiments, the base body is made of an intermetallic phase having a composition which corresponds to a phase stability line in the phase diagram of the corresponding alloy system. In this context, a “phase stability line” is to be understood as meaning a phase boundary line which runs parallel to the temperature axis in the phase diagram. Such compositions have the major advantage that no segregation occurs as the temperatures increase. Particular preference is given to intermetallic phases on a phase stability line which have no phase transition up to the melting point. The fewer the phase transitions which lie in particular in temperature ranges which can occur during use in EUV projection exposure apparatuses, and the more parallel the phase boundary line runs in relation to the temperature axis, the lesser the probability of the microroughness being adversely affected under the influence of thermal loading as a result of structural changes in the base body of the substrate. It is particularly preferable for the base body to be made of an alloy having a composition which, in the phase diagram, lies in a region which is bounded by phase stability lines. Alloys having such compositions have the advantage that any segregation processes can be stopped entirely by heat treatments, and therefore said alloys then have an increased high-temperature strength. It is advantageous that the intermetallic phase has the same Bravais lattice as the components thereof in crystalline form. As a result, it is possible to achieve a particularly stable crystalline structure which can further reduce a structural change as the temperature increases and/or over long periods of time, such that the roughness values of a mirror for EUV lithography which is based on such a substrate remain as unimpaired as possible throughout the service life. In particularly preferred embodiments, the alloy system is a binary alloy system, preferably with copper as one of the two components, particularly preferably a binary aluminum-copper system. Copper, in particular, has a high thermal conductivity. Substrates comprising a base body with a high copper fraction can thus be cooled particularly readily in order to thereby additionally prevent a structural change over the service life. On the basis of aluminum, it is possible to obtain high-strength materials which have a good dimensional stability. It should be pointed out that intermetallic phases of other alloy systems may also be suitable for mirror substrates for EUV lithography. In particular, intermetallic phases of ternary or quaternary alloy systems or alloy systems with five or more components may also be involved. In this context, it should be pointed out that real alloys always also have traces of impurities. Mention is made of components of an alloy system here only if the respective component has a marked influence on the phase diagram of the respective alloy system. As a whole, it has proved to be advantageous in the case of the base body materials described here for the material of the base body to have a face-centered cubic lattice structure. It is thereby possible to further increase the structural strength compared to body-centered cubic structures, for example, and therefore face-centered cubic materials are particularly suitable for use over long periods of time and, if appropriate, at elevated temperatures. It is particularly preferable that the material of the base body experiences no changes in microstructure in the event of changes in temperature from 20° C. to 150° C. over a period of time of 1 year. This temperature range includes those temperatures which are achieved when mirrors based on this substrate are used in an EUV projection exposure apparatus. Since the base body materials experience changes in structure only at temperatures of above 150° C., it is possible to reduce the influence which the structure of the base body has on the roughness values of the mirror substrate or of the mirror based thereon practically to zero. The changes in structure may involve a very wide variety of effects, for example the positional change of dislocations, oscillations of the atoms, instances of roughening, such as the so-called orange peel effect, or else segregation processes. In preferred embodiments, a polishing layer is arranged on the base body. It is advantageous that an adhesion-promoter layer is arranged between the base body and the polishing layer. Preferred polishing layers are, inter alia, layers which have been deposited without external current, for example nickel-phosphorus or nickel-boron layers. In this case, they can be present in a crystalline phase or in an X-ray-amorphous phase. In the case of nickel-phosphorus layers, preference is given to layers containing more than 11% by weight phosphorus. The layers can also be nickel-phosphorus alloy layers which also comprise one or two additional metals. The layers can likewise be nickel-phosphorus or nickel-boron dispersion layers which, if appropriate, likewise contain one or two additional metals. This also applies to nickel-boron layers. Furthermore, copper layers, quartz glass layers, amorphous or crystalline silicon layers, amorphous silicon carbide layers or else indium-tin oxide (ITO) layers have proved to be advantageous. All of these layers have the common feature that they can be polished to roughnesses of an RMS value of 5 angstroms or else considerably lower in particular in the spatial frequency range of between 10 nm and 1 μm. Using the base body materials described here, it is possible to observe a stability of the microroughness in the spatial frequency range of 10 nm to 250 μm even under thermal loading and in long-term operation, since base body materials which have no morphological surface degradation under these conditions are proposed. In particular, the microroughness is obtained on an angstrom scale in RMS values. In the spatial frequency range of 10 nm to 1 μm, the changes in roughness can lie in a region of less than 2.5 angstroms; in the spatial frequency range of 1 μm to 250 μm, it is possible to achieve a fluctuation of the roughness values of less than 3 angstroms. Depending on the combination of the base body material and the polishing layer material, it can be advantageous to provide an adhesion-promoter layer between the base body and the polishing layer in order to achieve a good bond between the base body and the polishing layer. In a further aspect, the object is achieved by a mirror for an EUV projection exposure apparatus, comprising a substrate as described above and a highly reflective layer on the substrate, in particular on a polishing layer. The mirrors for EUV projection exposure apparatuses are distinguished by a structural strength which is high with regard to long operating periods even at elevated temperatures and therefore by approximately constant roughness values throughout the period of use. In this case, it is possible to achieve service lives of a number of years. The substrates mentioned here, in particular on the basis of a base body made of an intermetallic phase, of a precipitation-hardened copper alloy or of a particulate composite, are suitable in particular but not only for use in the illumination system of an EUV projection exposure apparatus, for example in the form of facet mirrors. The features mentioned above and further features are apparent not only from the claims but also from the description and the drawings, wherein the individual features can in each case be realized by themselves or as a plurality in the form of subcombinations in an embodiment of the invention and in other fields and can constitute advantageous and inherently protectable embodiments. FIG. 1a schematically shows a first variant of an embodiment of a substrate 1 comprising a base body 2 and a polishing layer 3 applied thereto. The base body 2 and the polishing layer 3 perform different functions. Whereas a good dimensional stability is a priority for the base body 2, good machining and polishing properties are of primary importance for the polishing layer 3. The polishing layer can be applied by conventional vacuum coating processes, for example sputtering processes, electron beam evaporation, molecular beam epitaxy or ion beam-assisted coating. If the polishing layer is a metallic material, for example copper, nickel-phosphorus or nickel-boron, it is preferably applied without external current. Nickel-phosphorus or nickel-boron polishing layers, in particular, can also be applied as dispersion layers, in which case polytetrafluoroethylene can serve as the dispersant, for example. Nickel-phosphorus or nickel-boron polishing layers, in particular, are preferably applied with relatively high concentrations of phosphorus or boron, such that they are present predominantly or even completely in amorphous form and thereby have better polishing properties. They can then be hardened by, for example, heat treatment, plasma treatment or ion bombardment. Silicon as polishing layer material can also be deposited in amorphous or crystalline form in a manner controlled by the coating process. Amorphous silicon can be polished more effectively than crystalline silicon and, if required, can likewise be hardened by heat treatment, plasma treatment or ion bombardment. Polishing layers made of silicon or silicon dioxide can also be smoothed through use of ion beams. The polishing layer can also be made of silicon carbide or of indium-tin oxide. Preferred thicknesses of the polishing layer 3 can be about 5 μm to 10 μm for metal-based, polished polishing layers. In the case of non-metallic polishing layers 3, preferred layer thicknesses are about 1.5 μm to 3 μm. Using conventional polishing processes, metallic polishing layers can be polished to root mean squared roughnesses of less than 0.3 nm in the spatial frequency range of 1 μm to 200 μm and to root mean squared roughnesses of less than 0.25 nm in the spatial frequency range of 0.01 μm to 1 μm. Using conventional polishing processes, non-metallic polishing layers can be polished to root mean squared roughnesses of less than 0.3 nm over the entire spatial frequency range of 0.01 μm to 200 μm. FIG. 1b schematically shows a variant of the substrate 1 shown in FIG. 1a, in which an adhesion-promoter layer 4 is arranged between the base body 2 and the polishing layer 3. It is preferable that the adhesion-promoter layer 4 can have a thickness of up to 1 μm, preferably of between 100 nm and 500 nm. By way of example, it can be applied using CVD (chemical vapor deposition) or PVD (physical vapor deposition) processes. Such substrates 1 can be further processed to form EUV mirrors 5, as is shown schematically in FIG. 2a in a first variant of an embodiment, by applying a highly reflective layer 6 to the polishing layer 3. For use in the case of EUV radiation in the wavelength range of about 5 nm to 20 nm and with normal incidence of radiation, the highly reflective layer 6 is particularly preferably a multilayer system of alternating layers of material with a differing real part of the complex refractive index via which a crystal with network planes at which Bragg diffraction takes place is simulated to some extent. A multilayer system of alternating layers of silicon and molybdenum can be applied, for example, for use at 13 nm to 14 nm. Particularly if the highly reflective layer 6 is configured as a multilayer system, it is preferably applied using conventional vacuum coating processes such as, for example, sputtering processes, electron beam evaporation, molecular beam epitaxy or ion-beam-assisted coating. For use in the case of EUV radiation in the wavelength range of about 5 nm to 20 nm and with grazing incidence of radiation, preference is given to mirrors with an uppermost layer of metal, for example of ruthenium. FIG. 2b schematically shows a further variant of the mirror 5 shown in FIG. 2a, in which an adhesion-promoter layer 4 is arranged between the base body 2 and the polishing layer 3 of the substrate 1 of the mirror 5. In a first example, the base body 2 of the mirror 5 or of the substrate 1 can be made of a particulate composite. In particular, the base body 2 can be made of a particulate composite having a metallic matrix. By way of example, the latter can be a 2000 to 7000 series aluminum alloy, preferably a 5000 to 7000 series aluminum alloy, copper, a low-alloy copper alloy or copper niobate. The preferably spheroidal dispersoids of an extent in the range of 1 nm to 20 nm are advantageously titanium carbide, titanium oxide, aluminum oxide, silicon carbide, silicon oxide, graphite or diamond-like carbon, it also being possible for dispersoids of differing materials to be provided in the matrix. These materials can be produced by powder metallurgy, for example. The base body 2 can also be made of a particulate composite having a ceramic matrix. By way of example, particulate composites having a silicon or carbon matrix and silicon carbide dispersoids are particularly suitable. As a result of their covalent bond, they have a particularly high lattice rigidity. It is particularly preferable for the dispersoids to be distributed as homogeneously as possible in the matrix, for said dispersoids to be as small as possible and for the composite to have the smallest possible dispersoid spacings. In a second example, the base body 2 can be made of an alloy having components which have similar atomic radii and have a structure with a substitution lattice. By way of example, this may be the alloy system copper-nickel or silicon-aluminum. In a third example, the base body 2 can be made of a precipitation-hardened alloy. By way of example, it can be made of precipitation-hardened copper or aluminum alloys such as AlCu4Mg1, CuCr, CuNi1Si, CuCr1Zr, CuZr, CuCoBe, CuNiSi. In specific embodiments, the alloys were subjected to a further heat treatment after the precipitation hardening, this having the effect that the precipitations assume a spheroidal form in order to reduce stress or distortion energies in the material so as to further increase the high-temperature strength. To this end, the material is held for one to two hours at a temperature at which the basic phase of the matrix of the particulate composite is stable, whereas other phases in solutions go indeed into solution. Then, the temperature of the material is fluctuated repeatedly around this temperature range, and subsequently the material is slowly cooled at about 10° C. to 20° C. per hour. In a fourth example, the base body 2 can be made of an intermetallic phase. FIG. 3 shows the phase diagram of a binary aluminum-copper system, the intermetallic phases of which are particularly suitable as the material of the base body 2. At 300° C., sixteen intermetallic phases of AlxCuy, where x, y are integers, are stable. Of these, ten intermetallic phases stay stable upon cooling to room temperature (not shown here). The most important phases are indicated in FIG. 3 with the stoichiometric composition thereof. All of them lie at phase boundary lines which run parallel to the temperature axis over a certain temperature range. As a result, the microstructure thereof remains completely unchanged in these respective temperature ranges. Particular preference is given to Al2Cu, Al2Cu3 or Al3Cu5, inter alia, as the material of a base body of a mirror substrate for EUV lithography. In variations, it is also possible to use other binary alloy systems, one component of which is copper, for example binary systems of copper and zinc, tin, lanthanum, cerium, silicon or titanium. In a fifth example, the base body 2 can also be made of an alloy having a composition which lies between two phase stability lines. These regions are shaded gray in FIG. 3. Since the precipitation processes have been stopped by heat treatments, these alloys are present in a thermally stable phase. In this respect, preference is given to compositions from particularly wide ranges, for instance between Al2Cu and AlCu. The substrates of the examples mentioned here have particularly high strengths of 300 MPa or more, even at temperatures of up to 150° C., and also have a good long-term stability. The substrates, which comprise copper in the base body thereof, additionally have high thermal conductivities, and therefore they can be readily cooled. On account of their special base body, the substrates do not experience any changes in microstructure in temperature ranges which arise in long-term operation of mirrors in EUV projection exposure apparatuses. As a result, EUV mirrors having such a substrate have the advantage that the roughness values thereof remain substantially constant over their service life, in particular in the spatial frequency range of 0.1 μm to 200 μm. The EUV mirrors described here are suitable both for use in the illumination system, with which a mask or a reticle is illuminated with EUV radiation, and in the projection system, with which the structure of the mask or of the reticle is projected onto an object to be exposed, for example a semiconductor wafer, of an EUV projection exposure apparatus. Owing to their high-temperature strength and resilience, they are particularly suitable for mirrors arranged further forward in the beam path, where the thermal loading is higher, for instance in the illumination system. They are particularly suitable for use as facets of pupil facet mirrors and particularly of field facet mirrors. The above description of the specific embodiments has been given by way of example. From the disclosure given, those skilled in the art will not only understand the present invention and its attendant advantages, but will also find apparent various changes and modifications to the structures disclosed. The applicant seeks, therefore, to cover all such changes and modifications as fall within the spirit and scope of the invention, as defined by the appended claims, and equivalents thereof.
050283847	claims	1. A method of enhancing personnel safety in the operation of a water cooled, steam producing, boiling water nuclear fission reactor wherein a portion of circulating coolant water is vaporized to steam by heat produced from fissioning fuel within a reactor pressure vessel and the produced steam with any entrained water and volatile components is passed through a steam separator and steam dryer device in route to power generating means, comprising the step of inhibiting the conveyance of volatile nitrogen compounds with the steam by catalytic oxidation of any volatile nitrogen components carried with the steam to non-volatile nitrogen compounds. 2. The method of enhancing personnel safety in the operation of a nuclear reactor of claim 1, wherein the catalytic oxidation of any volatile nitrogen compounds carried with the steam to non-volatile nitrogen compounds is effected by contacting the steam and an volatile nitrogen compounds with a metallic oxide catalyst. 3. The method of enhancing personnel safety in the operation of a nuclear reactor of claim 1, wherein the catalytic oxidation of any volatile nitrogen compounds carried with the steam to non-volatile nitrogen compounds is effected by contacting the steam and any volatile nitrogen compounds with at least one metallic oxide catalyst selected from the group consisting of titanium dioxide and zirconium dioxide. 4. The method of enhancing personnel safety in the operation of a nuclear reactor of claim 1, wherein the catalytic oxidation of any volatile nitrogen compounds carried with the steam to non-volatile nitrogen compounds is effected by contacting the steam and any volatile nitrogen compounds with a metallic oxide catalyst comprising titanium dioxide. 5. A method of enhancing personnel safety in the operation of a water cooled, steam producing, boiling water nuclear fission reactor wherein a position of circulating coolant water is vaporized to steam by heat produced from fissioning fuel within a reactor pressure vessel and the produced steam with any entrained water and volatile components from the coolant water is passed through a steam separator and steam dryer in route to a power generating means, comprising the steps of adding hydrogen to the circulating water coolant to repress corrosion and inhibiting the conveyance of volatile nitrogen compounds with the steam from the reactor pressure vessel by catalytic oxidation of any volatile nitrogen compounds carried with the steam to non-volatile nitrogen compounds. 6. The method of enhancing personnel safety in the operation of a nuclear reactor of claim 5, wherein the catalytic oxidation of any volatile nitrogen compounds carried with the steam to non-volatile nitrogen compounds is effected by contacting the steam and any volatile nitrogen compounds with a metallic oxide catalyst. 7. The method of enhancing personnel safety in the operation of a nuclear reactor of claim 5, wherein the catalytic oxidation of any volatile nitrogen compounds carried with the steam to non-volatile nitrogen compounds is effected by contacting the steam and any volatile nitrogen compounds with at least one metallic oxide catalyst selected from the group consisting of titanium dioxide and zirconium dioxide. 8. The method of enhancing personnel safety in the operation of a nuclear reactor of claim 5, wherein the catalytic oxidation of any volatile nitrogen compounds carried with the steam to non-volatile nitrogen compounds is effected by contacting the steam and any volatile nitrogen compounds with a metallic oxide catalyst comprising titanium dioxide. 9. A method of enhancing personnel safety in the operation of a water cooled, steam producing, boiling water nuclear fission reactor wherein a portion of circulating coolant water is vaporized to steam by heat produced from fissioning nuclear fuel within a reactor pressure vessel and the produced steam with any entrained liquid water and volatile components from the coolant water is passed through a steam separator and steam dryer within the reactor pressure vessel before discharge to a power generating means, comprising the steps of adding hydrogen to the circulating water coolant to repress corrosion and inhibiting the conveyance of volatile nitrogen compounds with the steam from the reactor pressure vessel by catalytic oxidation with titanium dioxide of any volatile nitrogen compounds carried with the steam to non-volatile nitrogen compounds. 10. A method of enhancing personnel safety in the operation of a water cooled, steam producing, boiling water nuclear fission reactor wherein a portion of circulating coolant water is vaporized to steam by heat produced from fissioning nuclear fuel within a reactor pressure vessel and the produced steam with any entrained liquid water and volatile components from the coolant water is passed through a steam separator and steam dryer within the reactor pressure vessel before discharge to a power generating means, comprising the steps of adding hydrogen to the circulating coolant water to repress corrosion within the circulating system and inhibiting the conveyance of volatile nitrogen compounds comprising ammonia with the steam from the reactor pressure vessel by catalytic oxidation with titanium dioxide of any volatile nitrogen compounds comprising ammonia carried with the steam to non-volatile nitrogen compounds comprising nitrates an nitrites.
	claims	1. A core plate assembly for a boiling water reactor of nuclear plant, comprising:a core plate having a plurality of through-going apertures;a beam structure comprising a plurality of parallel first beams and a plurality of parallel second beams being perpendicular to the first beams, wherein the first and second beams enclose a plurality of rectangular areas beneath the core plate, wherein each of the rectangular areas encloses four of said through-going apertures;a plurality of control rod guide tubes, each being aligned with a respective one of the through-going apertures; anda plurality of transition pieces, each being received in a respective one of the control rod guide tubes, and each having four passages for communicating with a respective fuel assembly, each passage permitting a coolant flow into the respective fuel assembly,wherein a respective flow inlet for the coolant into each passage is provided,wherein at least one of the flow inlets has a non-circular cross-sectional shape, wherein the non-circular cross-sectional shape comprises a circular hole with a first recess extending therefrom. 2. A core plate assembly according to claim 1, wherein the first recess extends in sideward direction from the circular hole. 3. A core plate assembly according to claim 1, wherein the cross-sectional shape of the at least one flow inlet comprises a second recess extending in sideward direction from the circular hole. 4. A core plate assembly according to claim 3, wherein the first recess and the second recess are provided opposite to each other. 5. A core plate assembly according to claim 1, wherein the flow inlet is located between an upper end of the first and second beams and a lower end of the first and second beams. 6. A core plate assembly according to claim 1, wherein the at least one flow inlet is located opposite to a corner between one of the first beams and one of the second beams. 7. A core plate assembly according to claim 1, wherein the flow inlet extends through a first hole through the transition piece and a second hole through the control rod guide tube. 8. A core plate assembly according to claim 7, wherein the cross-sectional shape of the at least one flow inlet is determined by the first hole. 9. A core plate assembly according to claim 7, wherein the cross-sectional shape of the at least one flow inlet is determined by the second hole. 10. A core plate assembly according to claim 7, wherein a sheet is provided between the transition piece and the control rod guide tube, wherein the flow inlet extends through a third hole through the sheet, and wherein the cross-sectional shape of the at least one flow inlet is determined by the third hole. 11. A core plate assembly according to claim 10, wherein the sheet is joined to the transition piece. 12. A method of performing work on a core plate assembly of a boiling water reactor of a nuclear plant, the core plate assembly comprising:a core plate having a plurality of through-going apertures,a beam structure comprising a plurality of parallel first beams and a plurality of parallel second beams being perpendicular to the first beams, wherein the first and second beams enclose a plurality of rectangular areas beneath the core plate, wherein each of the rectangular areas encloses four of said through-going apertures,a plurality of control rod guide tubes, each being received in a respective one of the through-going apertures, anda plurality of transition pieces, each being received in a respective one of the control rod guide tubes, and each having four passages for receiving a respective fuel assembly, each passage permitting a coolant flow into the respective fuel assembly,wherein a respective flow inlet for the coolant into each passage is provided,the method comprising the steps of:removing one of the fuel assemblies from the boiling water reactor,introducing an elongated tool into the boiling water reactor and into the passage from which said fuel assembly was removed;positioning a tool head of the elongated tool in the proximity of the flow inlet of said passage; andactuating the tool head to cut said flow inlets to a non-circular cross-sectional shape.
	description	A preferred embodiment of a scanned-slot X-ray imaging setup is displayed in FIG. 1. It comprises a first collimator 102 provided with a first slot 102a, and a second collimator 104 provided with a second slot 104a. The collimators are spaced apart so that a space is provided in which an object 103 to be examined is positioned. A detector 106 is located beneath the second collimator 104. An X-ray source 100 is also provided. X-rays 101 incident to the setup are shaped by the first collimator 102 so that they hit the detector 106. The second collimator 104 absorbs Compton scattered X-rays from the object 103. Ideally, the collimators 102,104 and the detector 106 are symmetrical with respect to a centerline 105. If the slots are equal in width, and the detector also has this width, any misalignment caused by deviation from the symmetry line 105 for one of the slots or the detector results in a loss in efficiency. To avoid this problem, the second collimator slot 104a is slightly wider in comparison to the first collimator slot 102a. Moreover, the detector 106 width is not only larger than the collimator slot 102a, but also larger than the collimator 104. This arrangement is indicated in slightly exaggerated form in FIG. 1. With this setup, the system is insensitive to small misalignments with respect to the symmetry line 105, decreasing manufacturing cost while improving reliability. FIG. 2 illustrates the principle of the invention. It is assumed that the distance between the source 100, first collimator 102 and the second collimator 104 is a and b, respectively, the width of the slot of first collimator 102x, and the width of the slot of the second collimator 104y. Taking into the account the magnification due to the divergent X-ray beam and the principle of similar triangles, then a x = b y ⁢ xe2x80x83 ⁢ or ⁢ xe2x80x83 ⁢ x a = ⁢ y b ⇒ y = x ⁢ xe2x80x83 ⁢ b a What is needed is a wider second collimator such that y+2p=yxe2x80x2 greater than y, i.e., xb/a+2p greater than y, where p is a safety margin and yxe2x80x2 is the desired width. Therefore, a misalignment can be allowed with respect to the central symmetry line less than the safety margin p and still not loose any primary radiation in the second collimator 2. The same reasoning is applicable to the detector width. The safety factor p depends on the stability of the actual beam, and corresponds to a probability of misalignment. The range of p may be between about 0 to about 200 xcexcm. The distance p should be chosen such that any increase in radiation dose due to misalignment should be less than about 5% of the total radiation dose given to the patient. The probability for misalignment has to be assessed through repetitive measurements under realistic operating conditions for the X-ray imaging set-up. The loss factor for primary radiation may be about 1%. Moreover, the dead area 107 is due to mechanical damage when cutting the detectors on the wafer. This dead area 107 is usually provided with a guard-ring placed between the edge and the active detector area to sink leak current emanating from the mechanical damage. The dead area is so covered by the collimator 104 that it is not exposed to the X-rays. The collimators 102,104 are preferably made from efficient absorbers, such as W, Cu or Fe. The detector could be a silicon strip detector, a charge coupled device (xe2x80x9cCCDxe2x80x9d) camera coupled to a scintillating screen or a gas avalanche detector such as a parallel plate chamber. In the case of the CCD camera coupled to the scintillating screen, this coupling could be provided through, for example, optical fiber bundles. In case of silicon strip detectors, the wafers can be made at least about 500 xcexcm thick without problems. The signals are registered by standard state of the art electronics. When the detector is a semiconductor detector, it can be advantageously oriented edge-on to the incident x-rays. By edge-on, it is meant that the X-rays incite one edge of the of the detector, which also can be tilted slightly. Another option would be to provide a detector in the form of a film screen combination. A gas detector with the gas volume oriented edge-on can be made to any desired thickness by introducing a drift volume where the electrons created through interaction with the gas molecules can be collected through an electric drift field and drifted towards the edge of the detector where avalanche multiplication can take place and the signal registered by state of the art electronics. In FIG. 3, a top view of a system with a plurality of first collimator slots is displayed. Each of the lines 201 indicates one slot, i.e., a hole cut in the metal with a width equivalent to the desired width of the X-ray beam after passing the collimator. As shown, there is a plurality of collimators in two dimensions. FIGS. 1 and 2 correspond to a cross-section along line Axe2x80x94A in FIG. 3 for any of the slots 201 indicated in FIG. 3. While there has been disclosed effective and efficient embodiments of the invention using specific terms, it should be well understood that the invention is not limited to such embodiments as there might be changes made in the arrangement, disposition, and form of the parts without departing from the principle of the present invention as comprehended within the scope of the accompanying claims.
	claims	1. A method of thinning a sample section for TEM analysis, the method comprising:loading the sample to be thinned into an ion beam system;thinning the sample section by directing a substantially normal ion beam at a first side of the sample section in a milling pattern that thins the sample section in a series of passes, each pass having a scan speed and comprising moving the beam in a raster pattern from the outside of the sample section inward to the desired sample face and then returning to the outside of the sample section, the series of passes continuing until the first side of the sample section has been thinned to a desired depth wherein said scan speed decreases as it gets closer to said desired depth; andautomatically thinning the sample section by directing a substantially normal ion beam at the opposite second side of the sample section in a milling pattern that thins the sample section in a series of passes, each pass having a scan speed and comprising moving the beam in a raster pattern from the outside of the sample section inward to the desired sample face and then returning to the outside of the sample section, the series of passes continuing until the second side of the sample section has been thinned to a desired depth wherein said scan speed decreases as it gets closer to said desired depth. 2. The method of claim 1 wherein moving the beam in a raster pattern from the outside of the sample section inward to the desired sample face and then returning to the outside of the sample section comprises moving the beam in a raster pattern having an x-direction parallel to the desired sample face and a y-direction perpendicular to the desired sample face, said raster pattern comprising scanning the beam back and forth in the x-direction and then stepping the beam forward toward the desired sample face, said steps continuing until the desired sample face is reached. 3. The method of claim 2 wherein the time between forward steps becomes longer as the beam approaches the desired sample face. 4. The method of claim 2 wherein the beam dwell time increases as the beam approaches the desired sample face. 5. The method of claim 1 further comprising at the conclusion of each pass in the milling pattern moving the ion beam away from the sample face and beginning a new pass. 6. The method of claim 5 wherein multiple passes of the beam are used to reach the desired mill depth for the sample face. 7. The method of claim 1 wherein either heat or electrostatic charge buildup is allowed to dissipate between ion beam passes. 8. The method of claim 6 in which said multiple beam passes are made without changing the beam angle, energy, current, current density, or diameter. 9. The method of claim 1 in which thinning the sample section comprises thinning a central portion of the sample, leaving thicker material at the bottom and sides of the thinned portion. 10. The method of claim 9 in which the thinned central portion is approximately 3 μm wide, 4 μm deep, and less than 70 nm thick. 11. The method of claim 1 further comprising imaging the sample section during the thinning process and using automatic metrology software to determine whether the desired sample thickness has been reached. 12. A system for thinning a sample section for TEM analysis, comprising:a sample stage for supporting the sample section;an ion beam source for producing an ion beam to mill the sample section; anda controller programmed to control the ion beam source and the stage to carry out the method of claim 1. 13. The method of claim 1 further comprising extracting the sample from a wafer, wherein loading the sample to be thinned into an ion beam system occurs after the sample is extracted from the wafer. 14. A method of extracting a microscopic sample from a substrate, the method comprising:defining a sample section to be extracted on a substrate;directing a substantially normal ion beam at the substrate surface, said beam being scanned in a rectangular area to form a first rectangular hole having a predetermined depth, said first rectangular hole being adjacent to the sample section to be extracted;directing said beam at the substrate surface, said beam being scanned in a rectangular area to form a second rectangular hole having a predetermined depth, said second rectangular hole being adjacent to the sample section to be extracted but on the opposite side of said sample section from the first rectangular hole so that the remaining material between the two rectangles forms a thin vertical wafer that includes the sample section to be extracted;directing the ion beam at the remaining material at a non-normal angle in order to undercut the remaining material;rotating the sample by 180 degrees;directing the ion beam at the remaining material at a non-normal angle from the opposite side of the sample section in order to free the bottom of the sample section from the substrate;directing the ion beam at the remaining material at a non-normal angle in order to free the sides of the sample section leaving at tab of material on either side of the sample section connecting the sample section to the substrate;thinning the sample section by directing a substantially normal ion beam at a first side of the sample section in a milling pattern that thins the sample section in a series of passes, each pass having a scan speed and comprising moving the beam in a raster pattern from the outside of the sample section inward to the desired sample face and then returning to the outside of the sample section, the series of passes continuing until the first side of the sample section has been thinned to a desired depth wherein said scan speed decreases as it gets closer to the desired depth;thinning the sample section by directing a substantially normal ion beam at the opposite second side of the sample section in a milling pattern that thins the sample section in a series of passes, each pass having a scan speed and comprising moving the beam in a raster pattern from the outside of the sample section inward to the desired sample face and then returning to the outside of the sample section, the series of passes continuing until the second side of the sample section has been thinned to a desired depth wherein said scan speed decreases as it gets closer to the desired depth;severing the tabs of material on either side of the sample section connecting the sample section to the substrate in order to free the sample; andremoving the sample from the substrate. 15. The method of claim 14 wherein moving the beam in a raster pattern from the outside of the sample section inward to the desired sample face and then returning to the outside of the sample section comprises moving the beam in a raster pattern having an x-direction parallel to the desired sample face and a y-direction perpendicular to the desired sample face, said raster pattern comprising scanning the beam back and forth in the x-direction and then stepping the beam forward toward the desired sample face, said steps continuing until the desired sample face is reached. 16. The method of claim 15 wherein the time between forward steps becomes longer as the beam approaches the desired sample face. 17. The method of claim 15 wherein the beam dwell time increases as the beam approaches the desired sample face. 18. The method of claim 14 further comprising at the conclusion of each pass in the milling pattern moving the ion beam away from the sample face and beginning a new pass. 19. The method of claim 18 wherein multiple passes of the beam are used to reach the desired mill depth for the sample face. 20. The method of claim 14 wherein either heat or electrostatic charge buildup is allowed to dissipate between ion beam passes. 21. The method of claim 19 in which said multiple beam passes are made without changing the beam angle, energy, current, current density, or diameter. 22. The method of claim 14 in which thinning the sample section comprises thinning a central portion of the sample, leaving thicker material at the bottom and sides of the thinned portion. 23. The method of claim 22 in which the thinned central portion is approximately 3 μm wide, 4 μm deep, and less than 70 nm thick. 24. The method of claim 14 further comprising imaging the sample section during the thinning process and using automatic metrology software to determine whether the desired sample thickness has been reached. 25. The method of claim 14 further comprising:after thinning the first and second sides of the sample section, imaging the sample site;using automated metrology software to process the image to determine the thickness of the thinned sample section;if analysis of the image determines that the sample section is thicker than the desired thickness, redirecting the ion beam at the first and second sides to thin the sample section; andrepeating these steps until the desired thickness is reached. 26. The method of claim 14 wherein all steps are performed automatically without human intervention.
	abstract	A safety system for a nuclear power plant includes first through fourth sensors; a first division, including a first calculation module that determines first and second calculation results based on signals from the first and second sensors, a first data-sharing module for sharing the first and second calculation results with a second division, and a first voting logic for generating a first safety demand signal based on the first through fourth calculation results; and the second division, including a second calculation module for determining the third and fourth calculation results based on signals from the third and fourth sensors, a second data-sharing module for sharing the third and fourth calculation results with the first division, and a second voting logic for generating a second safety demand signal based on the first, second, third, and fourth calculation results, wherein the first through fourth sensors each monitor the same plant parameters.
	description	This invention was developed with support from the U.S. government under a contract with the United States Department of Energy, Contract No. DE-NA0000622. Accordingly, the U.S. Government has certain rights in this invention. The present invention relates to light shields for protecting electronic devices from exposure to light. Many electronic devices such as X-ray scanners, cameras, video equipment, motion detectors, and other electronic equipment have sensitive operational components that can be damaged or rendered ineffective when exposed to too much light. For example, overexposure of a phosphor panel of an X-ray scanner degrades the X-ray image and may erase the X-ray image altogether. Such overexposure may also damage the phosphor panel and other internal components. Electronic devices used outdoors and in well-lit areas are especially susceptible to overexposure risks and are therefore often fitted with light shields to block light from reaching their sensitive components. Unfortunately, conventional light shields often do not conform to contours of the electronic devices, thus allowing some light to pass between the light shields and the electronic devices. Light shields that do form a close fit are typically made specifically for one model of electronic device and cannot be adjusted or used with any other device. The present invention solves the above-described problems and provides a distinct advance in the art of light shields for electronic devices. More particularly, the present invention provides an adjustable light shield apparatus for blocking light from reaching sensitive components of an X-ray device, camera, video equipment, motion sensor, or other electronic device. The light shield can be adjusted to conform to electronic devices of different sizes and shapes. An embodiment of the light shielding apparatus broadly includes left and right support assemblies, a cross member, and an opaque shroud. The left and right support assemblies support the opaque shroud and provide rigidity to the light shielding apparatus. The left and right support assemblies each include primary support structure, a mounting component positioned on a proximal end of the primary support structure, and a lower support member depending from the primary support structure. The primary support structure directly supports the opaque shroud and may include a sloped shroud engagement surface, support member fastener holes, cross member fastener holes, and shroud fastener holes. The sloped shroud engagement surface extends downwardly and outwardly from the primary support structure such that the sloped shroud engagement surfaces on both of the primary support structures cooperatively urge the opaque shroud into a cylindrical dome shape when the light shielding apparatus is assembled. The support member fastener holes receive support member fasteners for removably connecting the lower support member to the primary support structure. The support member fasteners may be spring plungers, thumb screws, bolts, or any other suitable fastener. The cross member fastener holes receive cross member fasteners for removably connecting the cross member to the primary support structure. The shroud fastener holes receive shroud fasteners for removably connecting the opaque shroud to the primary support structure. The shroud fastener holes may be positioned on an underside of the primary support structure below the sloped shroud engagement surface. The shroud fasteners may be thumb screws, bolts, pins, or any other suitable fastener. The primary support structure may be formed of rectangular tubing, molded plastic, or any other suitable material and may vary in size depending on the type and size range of electronic devices for which the light shielding apparatus may be used. The mounting element is provided for removably connecting the light shielding apparatus to the front of the electronic device and broadly includes left and right hooks and a lower tab. The left and right hooks extend outwardly and downwardly from a proximal end of the primary support structure for engaging mounting slots on the electronic device. The lower tab extends outwardly below the left and right hooks for engaging a protrusion near the slots so as to prevent the hooks from being inadvertently dislodged from the slots. The lower support member retains the light shielding apparatus in an upright orientation when the light shielding apparatus is connected to the electronic device and includes a downwardly extending section and a horizontally extending section. The downwardly extending section provides vertical spacing between the horizontally extending section and the primary support structure and may be angled towards the proximal end of the primary support structure. The horizontally extending section continues horizontally from the lower end of the downwardly extending section towards the proximal end of the primary support structure. The end of the horizontally extending section may include a flat, angled, or contoured rubber pad or rubber stop for contacting the electronic device. The lower support member may be removably or shiftably connected to the primary support structure via the support member fasteners for compact storage. The cross member retains the left and right support assemblies in a coupled relationship with each other and may be connected to distal ends of the primary support structures or the vertically extending section of the lower support member via fasteners inserted into the cross member fastener holes. The cross member may be connected in one of a number of positions for spacing the primary support structures from each other according to the size and shape of the electronic device. The opaque shroud blocks light from reaching the electronic device and may include a cover, left and right upturned portions, and left and right outwardly extending strips. The cover may be extended between the primary support structures of the left and right support assemblies and may take the shape of a cylindrical dome or similar shape when deployed so as to form a central space covered from above. The cover may have a predetermined radius or may be adjustable so as to conform to the shape of a front cap of the electronic device. The upturned portions extend from left and right edges of the cover on outer sides of the cover. The upturned portions may be connected to the cover via staples or other fasteners so as to form a reinforced region. The outwardly extending strips turn outward from the upturned portions so as to form flanges extending substantially the length of the cover. The outwardly extending strips may include fastener holes for receiving the shroud fasteners. The fastener holes may be elongated or open-ended slots for allowing the opaque shroud to be adjusted relative to the support assemblies. The opaque shroud may be formed of canvas, rubber, or any other substantially flexible material or molded plastic, sheet metal, or any other substantially rigid material. The light shielding apparatus may be assembled by connecting the support members, cross member, and opaque shroud to the primary support structures of the left and right support assemblies. The opaque shroud may initially need to be manually urged into the cylindrical shape, while the inwardly sloping surfaces of the primary support structures help the opaque shroud retain the cylindrical dome shape. The support assemblies may then be connected to the electronic device by pivoting the light shielding apparatus upwards so that the lower tabs of the mounting elements clear the mounting bosses of the electronic device. The left and right hooks of the mounting elements may then be inserted or lowered into the slots of the electronic device. The light shielding apparatus may then be pivoted downwards, once the lower tabs clear the mounting bosses, until the lower support members contact the lower portion of the electronic device. The opaque shield may be adjusted once the light shielding apparatus is mounted on the electronic device such that the cover overlaps or contacts the cap of the electronic device. The light shielding apparatus may be removed from the electronic device by pivoting the light shielding apparatus upwards until the lower tabs of the mounting elements clear the mounting bosses of the electronic device. The light shielding apparatus may then be shifted upwards until the left and right hooks of the mounting elements are free from the slots of the electronic device. The lower support members, cross member, and opaque shroud may then be disconnected from the primary support structures and the opaque shroud may be folded or rolled up for compact storage. The above described light shielding apparatus provides many advantages over the prior art. For example, the light shielding apparatus may be easily connected to the electronic device without removing the electronic device from its mount and may be used with many different sizes and types of electronic devices. The opaque shroud may be flexed or adjusted to ensure that light is prevented from reaching the electronic device between the front of the electronic device and the opaque shroud regardless of the shape of the front of the electronic device. In addition, the light shielding apparatus is lightweight and can be disassembled for compact storage. This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. Other aspects and advantages of the present invention will be apparent from the following detailed description of the embodiments and the accompanying drawing figures. The drawing figures do not limit the present invention to the specific embodiments disclosed and described herein. The drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the invention. The following detailed description of the invention references the accompanying drawings that illustrate specific embodiments in which the invention can be practiced. The embodiments are intended to describe aspects of the invention in sufficient detail to enable those skilled in the art to practice the invention. Other embodiments can be utilized and changes can be made without departing from the scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense. The scope of the present invention is defined only by the appended claims, along with the full scope of equivalents to which such claims are entitled. In this description, references to “one embodiment”, “an embodiment”, or “embodiments” mean that the feature or features being referred to are included in at least one embodiment of the technology. Separate references to “one embodiment”, “an embodiment”, or “embodiments” in this description do not necessarily refer to the same embodiment and are also not mutually exclusive unless so stated and/or except as will be readily apparent to those skilled in the art from the description. For example, a feature, structure, act, etc. described in one embodiment may also be included in other embodiments, but is not necessarily included. Thus, the present technology can include a variety of combinations and/or integrations of the embodiments described herein. Turning now to the drawing figures, a light shielding apparatus 10 constructed in accordance with a preferred embodiment of the invention is illustrated. The light shielding apparatus 10 blocks light from reaching an electronic device such as an X-ray scanner 100, camera, video equipment, motion detector, or other electronic device and broadly comprises left and right support assemblies 12, 14, a cross member 16, and an opaque shroud 18. The left and right support assemblies 12, 14 support the opaque shroud 18 and provide rigidity to the light shielding apparatus 10. The left and right support assemblies 12, 14 each broadly include primary support structure 20, a mounting component 22 positioned on a proximal end of the primary support structure 20, and a lower support member 24 extending downwardly from the primary support structure 20. The primary support structure 20 directly supports the opaque shroud 18 and may include a sloped shroud engagement surface 26, one or more support member fastener holes 28, one or more cross member fastener holes 30, and one or more shroud fastener holes 32. The sloped shroud engagement surface 26 extends downwardly and outwardly from the primary support structure 20 towards the opposite support assembly and engages lower portions of the opaque shroud 18 such that the sloped shroud engagement surfaces 26 on both of the primary support structures 20 cooperatively urge the opaque shroud 18 into a cylindrical dome as described below. The one or more support member fastener holes 28 receive support member fasteners 34 for removably connecting the lower support member 24 to the primary support structure 20 and may be positioned on a side or bottom of the primary support structure 20. The support member fasteners 34 may be spring plungers, thumb screws, bolts, or any other suitable fastener. The cross member fastener holes 30 receive cross member fasteners for removably connecting the cross member 16 to the primary support structure 20 and may be positioned on the distal end of the primary support structure 20. Alternatively, the cross member fastener holes 30 may be positioned on the downwardly extending sections 44 of the lower support members 24, as shown in FIG. 6. The shroud fastener holes 32 receive shroud fasteners 36 for removably connecting the opaque shroud 18 to the primary support structure 20 and may be positioned on an underside of the primary support structure 20 below the sloped shroud engagement surface 26. The shroud fasteners 36 may be thumb screws, bolts, pins, or any other suitable fastener. The primary support structure 20 may be approximately five inches to approximately fifteen inches long, approximately one inch to approximately four inches wide, and approximately one half of an inch to two inches tall, or any other suitable length, width, and height. The primary support structure 20 may be formed of rectangular tubing, molded plastic, or any other suitable shape and material. It will be understood that the primary support structure 20 may be larger or smaller depending on the type and size of the electronic device 100 for which the light shielding apparatus 10 may be used. The mounting element 22 of each support assembly 12, 14 is provided for removably connecting the light shielding apparatus 10 to the electronic device 100 and broadly includes left and right hooks 38, 40 and a lower tab 42, as shown in FIGS. 3-5. The left and right hooks 38, 40 each may extend outwardly and downwardly from an upper portion of the proximal end of the primary support structure 20 and may be configured to engage slots 102 or other geometry of the electronic device 100. The lower tab 42 extends outwardly from a lower portion of the proximal end of the primary support structure 20 and ensures that the left and right hooks 38, 40 are not accidentally dislodged from or moved out of engagement with the slots 102 of the electronic device 100, as explained in more detail below. The mounting element 22 may be formed of machined rectangular tubing, fabricated metal, molded plastic, or any other suitable material. The lower support member 24 retains the light shielding apparatus 10 in an upright orientation (i.e., in alignment with the electronic device) when the light shielding apparatus 10 is connected to the electronic device 100 and broadly includes a downwardly extending section 44 and a horizontally extending section 46, as best seen in FIG. 2. The downwardly extending section 44 provides vertical spacing between the horizontally extending section 46 and the primary support structure 20 and may be angled towards the proximal end of the primary support structure 20. The horizontally extending section 46 continues from the lower end of the downwardly extending section 44 horizontally towards the proximal end of the primary support structure 20. The horizontally extending section 46 terminates at an end 48 configured to contact a lower portion of the electronic device 100. The end 48 may include a flat, angled, or contoured (e.g., rounded) rubber pad or rubber stop for contacting the electronic device 100 without scratching it. The lower support member 24 may be formed of rectangular tubing, molded plastic, or any other suitable material. The lower support member 24 may be removably or shiftably connected to the primary support structure 20 via the support member fasteners 34. Alternatively, the lower support member 24 may be permanently attached to the primary support structure 20 via welding, adhesive, or interference fit. The cross member 16 retains the left and right support assemblies 12, 14 in a coupled relationship with each other and may be connected to the primary support structures of the left and right support assemblies 12, 14 or the downwardly extending portions 44 of the lower support members 24 via fasteners inserted into the cross member fastener holes 30. The cross member 16 may be connected in one of a plurality of positions, as described in more detail below. The cross member 16 may be formed of rectangular tubing (FIGS. 1-5), bar stock (FIG. 6), molded plastic, or any other suitable material and may be any length, for dictating the spacing between the left and right support assemblies 12, 14. The opaque shroud 18 blocks light from reaching the electronic device 100 and includes a cover 50, upturned or upwardly extending portions 52, and outwardly extending strips 54, as best seen in FIG. 3. The cover 50 may be extended between the primary support structures 20 of the left and right support assemblies 12, 14 and may take the shape of a cylindrical dome or similar shape when deployed so as to form a central space 56 covered from above. The cover 50 may have a radius larger than a radius of a scanner bed of the electronic device 100 and smaller than a radius of an end cap 104 of the electronic device 100. That is, the cover 50 may form an extension of the end cap 104 to provide additional protection. The cover 50 may be rigid or substantially flexible for being used with electronic devices of different sizes and shapes. The upturned portions 52 may extend upwards from the left and right edges of the cover 50 on outer sides of the cover 50 and may be fastened to the cover 50 via staples, stitches, adhesive, welding, or any other suitable means depending on the type of material forming the opaque shroud 18. The outwardly extending strips 54 extend away from the cover 50 from tops of the upturned portions 52 so as to form flaps or tabs on either side of the cover 50. The outwardly extending strips 54 may include fastener holes 58 for receiving the shroud fasteners 36 and may be elongated or open-ended slots for allowing the opaque shroud 18 to be adjusted relative to the support assemblies 12, 14, as described in more detail below. The opaque shroud 18 may be formed of canvas, rubber, plastic, sheet metal, or any other suitable material and may be substantially flexible for being folded and/or rolled up when not in use and for being adjustably positioned and shaped as desired when in use. Use of the above-described light shielding apparatus 10 will now be described in more detail. First, the lower support members 24 may be connected to the primary support structures 20 of the left and right support assemblies 12, 14 via the support member fasteners 34. The opaque shroud 18 may then be connected to the left and right primary support structures 20 via the shroud fasteners 36. More specifically, the fastener holes 58 of the outwardly extending strips 54 of the opaque shroud 18 may be aligned with the shroud fastener holes 32 of the primary support structure 20 such that the shroud fasteners 36 may be inserted therethrough. The slotted shape of the fastener holes 58 may allow the opaque shroud 18 to be moved in relation to the primary support structure 20 before the shroud fasteners 36 are tightened. The cross member 16 may then be connected to the left and right support assemblies 12, 14 or the lower support members 24 via the cross member fastener holes 30 so as to couple the left and right support assemblies 12, 14 together. The cross member 16 may be connected in one of a plurality of positions such that the left and right support assemblies 12, 14 may be spaced apart from each other according to the size and shape of the electronic device. If the opaque shroud 18 is made of canvas or other non-rigid material, it may need to be unfolded or unrolled before attachment and manually urged into the cylindrical dome shape. The light shielding apparatus 10 may be removably connected to the electronic device 100 as follows. First, the left and right hooks 38, 40 of the mounting elements 22 may be positioned near the slots 102 of the electronic device 100. The light shielding apparatus 10 may need to be pivoted upwards slightly such that the lower tabs 42 clear the mounting boss 106 of the electronic device 100 as the left and right hooks 38, 40 are lowered into the slots 102. The light shielding apparatus 10 may then be pivoted downwards until the lower support members 24 contact the lower portion of the electronic device 10 such that the light shielding apparatus 10 hangs from and rests against the front of the electronic device 10. The opaque shroud 18 should align with operative components of the electronic device 100 (e.g., optical lens of a camera) but may be adjusted as described above until light is substantially or completely blocked from reaching the operative components of the electronic device 100. The light shielding apparatus 10 may then be removed from the electronic device 100 and disassembled as follows. First, the apparatus 10 may be pivoted upwards until the lower tabs 42 clear the mounting boss 106. The left and right hooks 38, 40 may then be slid upwards out of the slots 102 so as to be disconnected from the electronic device 100. The lower support members 24 and the cross member 16 may then be disconnected from the left and right support assemblies 12, 14 by removing the support member fasteners 34 and cross member fasteners. The opaque shroud 18 may also be disconnected from the primary support structures 20 and removed, folded, and/or rolled for storage. The above-describe light shielding apparatus 10 provides many advantages over the prior art. For example, the light shielding apparatus 10 may be easily connected to the electronic device 100 without removing the electronic device 100 from its mount and may be used with many different sizes and types of electronic devices. For example, the left and right support assemblies 12, 14 may be spaced closer together or farther apart from each other for use on smaller or larger electronic devices such as X-ray devices having standard 14×17 phosphor panels and X-ray devices having larger 14×51 phosphor panels. The opaque shroud 18 may be flexed or adjusted to ensure that light is prevented from reaching the electronic device 100 between the front of the electronic device 100 and the opaque shroud 18 regardless of the shape of the front of the electronic device 100. The light shielding apparatus 10 may also protect the electronic device 100 from the elements and dust accumulation. In addition, the light shielding apparatus 10 is lightweight and can be disassembled for compact storage. Although the invention has been described with reference to the embodiments illustrated in the attached drawing figures, it is noted that equivalents may be employed and substitutions made herein without departing from the scope of the invention as recited in the claims.
	description	This application is a divisional of U.S. application Ser. No. 13/336,155, filed Dec. 23, 2011, which is a divisional of U.S. application Ser. No. 12/542,926, filed Aug. 18, 2009, which claims priority under 35 U.S.C. §119 to German Patent Application DE 10 2008 045 336.6, filed Sep. 1, 2008. The entire contents of each of these applications is incorporated herein by reference. The disclosure relates to a processing system that can provide multiple energy beams for modifying and/or inspecting an object. The multiple energy beams may include a laser beam and a particle beam, such as an electron beam or an ion beam. In the manufacture of miniaturized devices there exists a desire to modify an object by removing material from the object or by depositing material on the object. Conventional systems used for modifying the object include a microscope for inspecting the object to monitor a process of the modification. An example of such conventional system is an electron microscope, in which an electron beam generated by the electron microscope is used for inspecting the object and also for activating a processing gas modifying the object. Another example of a conventional processing system includes an electron microscope to generate an electron beam and an ion beam column to generate an ion beam, where the electron beam and the ion beam can be directed to a same location of an object to be modified. Here, the ion beam can be used to modify the object, and the electron beam can be used to monitor the progress of such sample modification. A process gas can be supplied to the object to modify the object by an interaction with the process gas which is activated by the electron beam and/or the ion beam. The conventional system using a particle beam, such as an electron beam or an ion beam, for modification of the object has an advantage in that the processing of the object can be performed with a relatively high accuracy. A disadvantage of such system is that the modification of the object can be slow and that a high processing time can be involved if a larger amounts of materials are to be removed from or deposited on the object. Other known processing systems use a laser beam to remove material from an object. The removal rate, i.e. an amount of material removed per unit time, of the laser system is typically greater than that of a charged particle beam system. However, the accuracy of the modification of the object employing the laser system is typically much lower than the accuracy achievable with a particle beam system. In some embodiments, the disclosure provides a processing system that directs multiple energy beams toward an object to perform process the object (e.g., modify of the object, inspect the object). In some embodiments, a processing system includes a particle beam column to generate a particle beam directed to a first processing location, and a laser system to generate a laser beam directed to a second processing location. In certain embodiments, the particle beam column may include an electron beam column or an ion beam column, where the particle beam column can also be configured to operate as a particle beam microscope by including a secondary particle detector. The secondary particle detector may include an electron detector or an ion detector. In some embodiments, the first processing location substantially coincides with the second processing location such that the object can be moved to the a location and can be processed at that location by both the laser beam and the particle beam without having to move the object for subsequent laser beam and particle beam processing. In certain embodiments, the first processing location onto which the particle beam is directed is spaced apart from the second processing location onto which the laser beam is directed. The spaced apart processing locations can have an advantage if particles or other contaminations are generated by the laser beam, because the spacing can considerably reduce the deposition of such particles or other contaminants on components of the particle beam column as compared to situations where the first and second processing locations coincide. In certain embodiments, the processing system includes a protector for protecting components of the particle beam column from particles or other contaminations produced during a processing with the laser beam. It is possible that a considerable amount of particles and other contaminations is released from the object during a laser processing and that such particles and contaminations can deposit on sensitive components of the particle beam system. Exemplary sensitive components of the particle beam system include electrodes and apertures of the particle beam column. Deposition on such components of the particle beam column may result in a deterioration of a performance of the particle beam column. For example, focussing of the particle beam may be deteriorated or imaging quality of the particle beam column may be deteriorated. In some embodiments, the protector includes a plate and an actuator configured to move the plate back and forth between a first position in which the components of the particle beam system are protected from particles and contaminations released during the laser processing, and a second position particle in which the components of the particle beam system are not protected from the particles and contaminations released during the laser processing. In certain embodiments, the protector is configured such that, in its first position, particles and other contaminations generated by the laser beam are prevented from hitting sensitive components of the particle beam column, while processing of the object using the particle beam is prevented by the plate. In the second position, the plate is in a retracted position in which processing or inspection of the object using the particle beam column is possible. In some embodiments, the protector includes a door separating a first vacuum space in which the first processing location is located from second vacuum space in which the second processing location is located. The door may provide a shutter which closes an opening between the two vacuum spaces, where the shutter may allow, in its closed position, to maintain a pressure difference between the first and second vacuum spaces. For this purpose, each of the first and second vacuum spaces may include separate vacuum ports connection to vacuum pumps. In embodiments where the first processing location is spaced apart from the second processing location, in general, the object has to be moved between the two processing locations to allow processing by both the laser beam and particle beam. In some embodiments, the object is mounted on an object mount of a stage, where the stage includes at least one actuator to displace the object mount relative to the base. It is then possible to position the stage relative to the particle beam column and control the at least one actuator such that plural different locations of the object are located at the first processing location of the particle beam, without moving the base of the stage relative to the particle beam column. The base of the stage can be maintained at a fixed position on a suitable support, for example. In certain embodiments, the processing system includes a transport device configured to move the stage back and forth between first and second predetermined positions. If the stage is positioned in the first position, the object mounted on the stage is located close to the first processing location to be processed by the particle beam, and if the stage is positioned in its second position, the object mounted on the stage is positioned close to the second processing location to be processed by the laser beam. In such configuration, the object can be moved back and forth between the first and second processing locations without removing the object from the object mount of the stage. According to exemplary embodiments, the transport device includes an actuator performing a translation of the stage from the first position to the second position. The transport device may include a carrier, such as a rail, to support the stage during translation between the first and second positions. In some embodiments, in which the first and second processing locations are spaced apart from each other, the transport device includes a gripper configured to grip the object for movement between a first stage and a second stage, where the first stage mounts the object for processing by the particle beam, and the second stage is configured to mount the object for processing by the laser beam. In some embodiments, the transport device for moving the object between the first and second processing locations includes an actuator for performing the movement. The actuator can include a rod traversing a wall of the vacuum vessel, where a sealing between the vacuum vessel and the rod is arranged such that a distance between the sealing and the first processing location is greater than a distance between the sealing and the second processing location. In the exemplary embodiments described below, components that are alike in function and structure are generally designated by alike reference numerals. Therefore, to understand the features of the individual components of a specific embodiment, the description of other embodiments and the summary may be referred to. FIG. 1 is a schematic front view of a portion of a processing system 1 and illustrates a functionality of an object mount 3 which can be used in some embodiments of the processing system to mount an object 5 in front of a particle beam column 7. The particle beam column 7 is, in the illustrated example, an electron beam column for generating an electron beam 11 directed towards a processing location 9. The object mount 3 is configured to hold the object 5 such that a surface thereof is located at the processing location 9 and such that the object can be displaced in a x-direction, in a y-direction, a z-direction and such that the object can be tilted about an axis 13 oriented parallel to the y-direction, where the axis 13 is located close to the processing location 9 or intersects the processing location 9. The object 5 is mounted on and fixed to an object mount 15 of a stage 17. The object 5 can be abutted against an end stop on the object mount 15, and can be adhered to the object mount or fixed to the object mount 15 by a clamp and/or another suitable mechanism. The stage 17 includes a base 19 and an intermediate component 21 which can be displaced by an actuator 18, such as a motor, in the y-direction as indicated by an arrow 23. The object mount can be displaced relative to the intermediate component 21 in the x-direction by operating a further actuator 20 as this is schematically indicated by an arrow 25 in FIG. 2. The base 19 rests on a bracket 27 which is articulated to a base 29 of the object mount 3 such that the base 19 can be pivoted about the axis 13. The option of pivoting the object 5 about the axis 13 is indicated by an arrow 24 in FIG. 2. The stage 17 may further include an additional intermediate component mounted between the intermediate component 21 and the base 15 to displace the object 5 relative to the base 29 in the z-direction, such that the object mounted on the object mount can be displaced relative to the base of the object mount in three independent directions. FIG. 4 is a schematic illustration of the processing system 1, in which the base 29 illustrated with reference to FIG. 1 above is not shown in FIG. 4. The processing system 1 includes two particle beam columns which include the electron beam column 7 for generating the electron beam 11 directed to the processing location 9, and an ion beam column 41 for generating an ion beam 43 which is also directed to the processing location 9. The electron beam column 7 includes an electron source 45 having a cathode 47, an electrode system 49, a condenser lens system 51 for generating the beam 11. The electron beam 11 traverses a secondary electron detector 53 and an objective lens 54 for focussing the electron beam 11 at the processing location 9. Beam deflectors 55 are provided for varying the position onto which the electron beam 11 is incident on the object 5. The deflectors 55 can be used to scan the electron beam 11 across a surface of the object 5. Secondary electrons generated during such scanning can be detected with the detector 53 to generate an electron microscopic image of the object 5 in the scanned region at the processing location 9. Additional secondary particle detectors, such as an electron detector 57 or an ion detector can be located adjacent to the electron beam column 7 close to the processing location 9 and within a vacuum chamber 59 to also detect secondary particles. The ion beam column 41 includes an ion source 61 and electrodes 63 for shaping and accelerating an ion beam 43. Beam deflectors 65 and focussing coils or focussing electrodes 67 are provided to focus the ion beam 43 at the processing location 9 and to scan the ion beam 43 across a region of be object 5. A gas supply system 69 includes a reservoir 71 for a processing gas which can be selectively supplied via a conduit 73 ending close to the processing location 9 by operating a valve 75. The processing gas can be activated by the ion beam or the electron beam to selectively remove material from the object 5 or to selectively deposit material on the object 5. Such processing can be monitored using the electron microscope 7. A removal of material from the object 5 can be also achieved by directing the ion beam onto the object without supplying of a processing gas. The vacuum chamber 59 is defined by a vacuum vessel 79 which can be evacuated by a vacuum pump connected to the vessel at a pumping port 81 and which can be vented via a venting port 83. The electron beam column includes a vacuum vessel 84 having a small aperture traversed by the electron beam 11 and separating upper and lower vacuum spaces wherein the electron source is located in the upper vacuum space which is separately pumped via a pumping port 85, such that the electron source 45 can be permanently maintained under high vacuum conditions even when the processing gas is supplied to the processing location 9. Background information about systems using plural particle beams for processing of an object can be obtained, for example, from US 2005/0184251 A1, U.S. Pat. No. 6,855,938 and U.S. patent application Ser. No. 12/448,229, wherein the full disclosure of these documents is incorporated by reference herein. The processing system 1 further includes a laser system 91 which is configured to direct a laser beam 93 to a second processing location 95. For this purpose, the laser system 91 includes a laser 97 and collimation optics 99 to shape the laser beam 93. The laser beam is directed via one or more mirrors 101 or via a light guide to a location close to the vacuum chamber 97 where it is incident on a mirror 103 which directs the beam towards the second processing location 95 and which is pivotable as indicated by arrow 105 such that the beam 93 can be scanned across a object disposed at the processing location 95. The laser beam 93 enters the vacuum space 109 by traversing a window 107. The vacuum space 109 is also defined by the vacuum chamber 79 and can be separated from the vacuum space 59 by closing a door 111. The door 111 includes a shutter plate 113 which is indicated in FIG. 4 by continuous lines in an open position and in broken lines when it is positioned in a closing position. An actuating rod of the door is used to displace the shutter plate 113 from its open position to its closed position. The door 111 can be adapted such that it is, in its closed position, vacuum tight by providing a suitable sealing 112 between the shutter plate 113 and the vacuum vessel 97. It is then possible to maintain different vacuum pressures in the vacuum spaces 59 and 109 if the door is in its closed position. The vacuum space 109 can be separately evacuated via a vacuum port 115 and vented via a venting port 116. The object 5 can be moved back and forth between the processing location 9 and the processing location 95 by operating the transport system 121. The transport system 121 includes a rod 123 traversing a vacuum seal 125 to extend into the vacuum space 109. The vacuum seal 125 is located at a distance from the processing location 95 which is smaller than a distance between the vacuum seal 125 and the processing location 9. A connector 127 is provided at an end of the rod 123 wherein the connector 127 is configured to be mechanically connected to the base 19 of the stage 17. The connector can be further configured to provide an electrical connection to the stage to control the actuators of the stage in order to displace the object 5 relative to the base of the stage in the at least two or three independent directions. Electrical signals for controlling the actuators con me supplied via wires 126 extending from a controller 128 located outside of the vacuum vessel 79 through an interior of the rod 123 to the connector 127. Sensors, such as one ore more position sensors, can be provided on the stage 17 to measure a current position of the object mount 15 relative to the base 19 of the stage, such that the controller 128 can perform the control of the actuators based on the signals provided by the sensors supplied to the controller via the connector 127 and wires 126 extending through the rod 123. In the situation shown in FIG. 4, the stage 17 is located such that the object 5 is located at the processing location 9 such that it can be inspected or modified by the electron beam 11 or the ion beam 43. The stage 17 is shown in broken lines in FIG. 4 in a position such that the object 5 is located at the processing location 95 for processing by the laser beam 93. The transport system 21 can move the stage 17, together with the object 5 mounted thereon, back and forth between these two positions. For this purpose, the transport system 121 includes a rail or supporting bar 131 to support the stage 17 against gravity during its transport movement between the processing locations. When the stage is positioned at the processing location 9, the stage is carried by the bracket 27 of the object mount 3 as illustrated above. As shown in FIG. 4, a space 133 is provided between the support bar 131 to allow tilting of the bracket 27 about axis 13 without interference with the support bar 131 after the bar 123 is released from the connector 127 and sufficiently retracted. It is however possible to pull the base 19 of the stage 17 across the distance 133 onto the supporting bar 131. The supporting bar 131 further includes a further space 135 which is traversed by the shutter plate 113 when the door 111 is in its closed position. The door 111 can be closed when the transport system 123 has pulled the stage 17 to the position at the processing location 95, or if the stage is pushed to the position at the processing location 9 and the rod 123 is released from the connector 127 and completely drawn back into the vacuum space 109. The object 5 is processed with the laser beam 93 at the processing location 95, wherein particles or contaminations evaporating from or released from the object will deteriorate the vacuum conditions in vacuum space 109. It is possible to close the door 11 to separate the vacuum space 59 from the vacuum space 109 to prevent a deterioration of the vacuum in the vacuum space 59. It is in particular possible to prevent contamination of the vacuum space 59 and contamination of components of the particle beam columns 7 and 41. Processing of the object 5 with the laser beam 93 is monitored using an end point detector 141 which may include, for example, a light source 143 for generating a measuring light beam 144 and a light detector 45. The measuring light beam 144 is directed towards the processing location 95 and enters the vacuum space 109 by traversing the window 146. The light detector 145 receives emerging light 147 originating from processing location 95 through a window 148. The light received by the detector 145 can be analysed to determine a processing condition of the object 5, and the processing of the object 5 by the laser beam 93 can be terminated based on such determination. After the processing by the laser beam 43 is terminated, the door 111 is opened and the transport system 121 moves the object 5 together with the stage to the processing location 9. A further processing of the object 5 can be performed at the processing location 9 by operating the ion beam 43 or electron beam 11, and the object 5 can also be imaged by the electron microscope 7. A positioning of the stage 17 on the bracket 27 can be performed with a high accuracy. For example, an end stop 22 can be used to precisely position the stage on the bracket 27 wherein the transport system 121 abuts the base of the stage 17 against the end stop 22 before releasing the connector 127. It is also possible to precisely position the stage on the bracket 17 by using micro switches or proximity sensors and by operating the transport system 121 until such sensors provide a desired measuring signal. FIG. 3 shows an exemplary embodiment in which an optical distance measuring system 151 is used for positioning a stage 17a relative to a support 27a. The optical distance measuring system 151 emits a light beam 152 reflected from a mirror 153 mounted on a base 19a of the stage 17a. The light reflected from the mirror is analysed for determining a distance between the base 19a and the measuring system 151. The transport system 121 is operated until the measured distance equals a desired distance to a sufficient accuracy. FIG. 5 shows a further embodiment of a processing system lb which has a configuration similar to the configuration of the processing system illustrated with reference to FIG. 4 above. The processing system lb differs from the processing system illustrated above in that a transport system 121 for displacing an object 5b back and forth between a processing location 9b for processing by particle beams 11b and 43b, and a processing location 95b for processing by a laser beam 93b. The processing system includes a rod 123b and a gripper 127b attached to an end of the rod 123b for gripping the object 5b. The object is moved between the processing locations 9b and 95b without moving a stage 17b. The stage 17b remains at its position relative to the processing location 9b and is used to correctly position and orient the object 5b relative to the particle beams 11b and 43b. A separate stage 18b is provided at the processing location 95b. The gripper 127b can place the object 5b on the stage 18b. The stage 18b may have a configuration which is less complicated than a configuration of the stage 17b. For example, it might be unnecessary to tilt the object about an axis or it may be unnecessary to move the object in three independent directions since the laser beam 93b can be scanned by a pivotable mirror 103b across a region of the object 5b which is larger than a region across the electron beam 11b or the ion beam 43b can be scanned. It may be also unnecessary to provide positional movements in a z-direction, since the collimating optic 99b can be moved in z-direction for changing the focus of the laser beam in z-direction. FIG. 6 is a schematic illustration of a further embodiment of a processing system 1c having a configuration similar to a configuration of the processing systems illustrated with reference to FIGS. 4 and 5 above. The processing system 1c differs from the processing systems illustrated above in that a processing location 9c for processing an object 5c using a particle beam substantially coincides with a processing location 95c for processing the object 5c using a laser beam 93c. The processing locations 9c and 95c are located in a common vacuum space 59c. The processing system 1c does not include a transport system for moving the object between different processing locations. However, the processing system 1c includes a protection system 161 including a cup-shaped protector 163 partially enclosing components of a particle beam column 7c when the protection system is in a protecting position as shown in FIG. 6. The protection system 161 further includes a cup-shaped protector 165 partially enclosing components of an ion beam column 41c when the protection system is in the protection position. The protectors 163 and 165 protect components of the electron beam column 7c and the ion beam column 41c during processing of the object 5c with the laser beam 93c. After termination of the processing by the laser beam 93c, the protectors 163 and 165 which are mounted on a rod 167 can be retracted into a retracted position in which they do not interfere with a processing of the object 5c with the electron beam 11c or the ion beam 43c. The rod 167 may traverse a vacuum vessel 79c defining the vacuum space 59c by traversing a suitable sealing 169. The rod 167 can be operated by an actuator, such as a motor, or by hand, for displacing the protectors 163, 165 between the protecting position and the retracted position. Protectors and those illustrated above can also be used to protect particle detectors disposed in the vacuum space 59c close to the object 5b while performing the processing with the laser beam. In the embodiments illustrated above, an electron beam column and an ion beam column are provided. It is, however, also possible to provide only one particle beam column, such as the electron beam column or the ion beam column, wherein the single particle beam column is integrated in a processing system together with a laser system for processing the object. In the embodiments illustrated with reference to FIGS. 4 and 5 above, the processing location for processing using at least one particle beam is located at a relatively large distance from a processing location for processing by a laser beam. Moreover, a door is provided for separating the corresponding vacuum spaces from each other. It is, however, also possible to merely provide a protector between the processing location for laser processing and the processing position for particle beam processing, wherein the protector intercepts particles released during the laser beam processing. The protector can be formed as a plate which is attached to a rod or other suitable tool for displacing the protector. In some of these embodiments it may be unnecessary to provide the protector with a function of a vacuum tight shutter such that the two processing locations can be located in a same vacuum space. However, it is also possible to separate the corresponding vacuum spaces by a vacuum lock including more than one shutter such that the object is placed in a space between two closed shutters when it is transferred from one processing position to the other. The above illustrated embodiments, the laser processing system generates a laser beam which traverses a window in a vacuum vessel to enter the vacuum space, wherein a raster device, such as a pivotable mirror (103) is located outside of the vacuum space. It is, however, also possible to direct the laser beam into the interior of the vacuum space by another mechanism, such as a light guide, and it is also possible to have the collimation optics located within the vacuum space. In the above illustrated embodiments, an end point detector for determining a termination of the laser processing includes a light source for generating a measuring beam and a detector. According to other embodiments, it is possible to determinate the processing by the laser beam based on other principles. For example, light generated by the processing laser beam and reflected from the object can be detected to monitor the laser processing. It is further possible to detect a light generated by a laser induced plasma generated during the operation of the processing laser. It is further possible to provide a plasma source for generating a plasma close to the process object, wherein material removed from the object experiences charge carrier recombinations which generate characteristic light which is indicated of the type of material currently processed. A determination for terminating the laser processing can be based on detection of such characteristic light.
	description	This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2004-354467, filed Dec. 7, 2004, the entire contents of which are incorporated herein by reference. 1. Field of the Invention The present invention relates to a method of creating charged beam drawing data used for a charged beam drawing apparatus to draw a pattern on a sample using a charged beam, a charged beam drawing method, a charged beam drawing apparatus and a semiconductor device manufacturing method. 2. Description of the Related Art In manufacturing of LSI currently, there is an increasing demand for high precision of pattern transferring and processing dimensions for high integration of wires and devices. To respond to such a demand, recently, an electron beam drawing apparatus has been used for drawing a fine pattern on a sample such as a semiconductor wafer or a mask substrate. Design data of a device pattern to be drawn on a sample is normally converted beforehand into drawing data corresponding to a drawing apparatus. The drawing data is recorded (stored) into a storage device or the like attached to the drawing apparatus. The step for converting the design data into the drawing data includes a step of decomposing the device pattern into relatively simple patterns (for example, rectangular patterns), and a step of dividing the design pattern into mesh fields corresponding to the deflection width of an electron beam of the drawing apparatus. In the pattern drawing by an electron beam drawing apparatus, an electron beam where an electron generated from an electron source is accelerated is formed through a plurality of variable apertures with reference to the drawing data, and this formed electron beam is deflected by two stages or more of deflectors, and focused onto a sample on a movable stage by an electromagnetic lens, thereby a pattern is drawn (Japanese Patent Nos. 3085918, 3125724, and 3168996). FIG. 14 is a view schematically showing an example of the field division of design data that is performed in electron beam drawing. In FIG. 14, a subfield is divided into 4×4. In FIG. 14, reference numeral 91 (square shown by a thick solid line) shows a subfield, 92 to 94 (patterns shown by diagonal lines) show design data corresponding to drawing data of relatively large dimensions (for example, 130 nm L&S or pad electrode), 95 to 97 (patterns shown by stripes) show design data corresponding to drawing data of relatively fine dimensions (for example, 60 nm L&S). At the center of a drawing field, the deflection angle by a corresponding deflector is zero. At the portion that is more apart from the center of the field, the deflection angle of an electron beam becomes larger. When the deflection angle of the electron beam is large, blurring of the beam becomes relatively large owing to aberration of the electromagnetic lens and the like, and as a consequence, the resolution of the pattern drawing becomes lower than that at the center of the field. FIG. 15 shows results (SEM photos) of an evaluation by an SEM on resist pattern drawn by a conventional drawing method by use of the design data of FIG. 14, and obtained after a developing process and the like. From FIG. 15, it is known that the resolution of the fine pattern that is near the field center entangled by a dotted line is relatively preferable. Further, it is known that there is not a significant problem in the resolution even in the relatively large pattern at the end of the field outside of the dotted line. However, it is known that, in the fine pattern at the edge of the field, the deterioration of the resolution is conspicuous, and it is extremely difficult to resolve the fine pattern. As a method for solving this problem, and for resolving fine patterns in the entire drawing area, there is known a method in which the drawing field is set small, and the electron beam deflection width is made small, thereby drawing is performed. However, in the above method, the number of drawing fields increases. Consequently, there occurs a problem that it requires longer drawing time than the above conventional drawing method, and the throughput is decreased. According to an aspect of the present invention, there is provided a method of creating charged beam drawing data used for a charged beam drawing apparatus to draw a pattern on a drawing area of a sample by irradiating a charged beam onto the sample, the method comprising: selecting a charged beam drawing apparatus which divides the drawing area into two or more hierarchical fields including a plurality of main fields, a plurality of subfields which are lower in layer than the plurality of main fields and a plurality of unit fields which are lower in layer than the plurality of subfields, and draws a pattern using the unit field as a drawing unit, as the charged beam drawing apparatus to draw the pattern; dividing design data corresponding to the pattern to be drawn on the drawing area into a plurality of first design data corresponding to the plurality of main fields, dividing each of the plurality of first design data into a plurality of second design data corresponding to the plurality of subfields, and dividing each of the plurality of second design data into a plurality of third design data corresponding to the plurality of unit fields; evaluating quality of resist resolution to a predetermined dimension on each of the plurality of unit fields; creating a table which relates the plurality of unit fields to the quality of the resist resolution based on an evaluation result acquired by the evaluating the quality of the resist resolution; judging whether or not each of the plurality of third design data corresponds to data having the predetermined dimension and corresponds to a pattern falling in the unit field which the quality of the resist resolution is rejectable based on the predetermined dimension and the table; and converting data judged to correspond to the data among the plurality of third design data into first drawing data after performing a coordinate conversion so that the data fall in the unit field which the resist resolution is acceptable, and converting data judged not to correspond to the data among the plurality of third design data into second drawing data without performing the coordinate conversion. According to an aspect of the present invention, there is provided a charged beam drawing method using a charged beam drawing apparatus to draw a pattern on a drawing area of a sample by irradiating a charged beam onto the sample, the method comprising: selecting a charged beam drawing apparatus which divides the drawing area into two or more hierarchical fields including a plurality of main fields, a plurality of subfields which are lower in layer than the plurality of main fields and a plurality of unit fields which are lower in layer than the plurality of subfields, and draws a pattern using the unit field as a drawing unit, as the charged beam drawing apparatus to draw the pattern; dividing design data corresponding to the pattern to be drawn on the drawing area into a plurality of first design data corresponding to the plurality of main fields, dividing each of the plurality of first design data into a plurality of second design data corresponding to the plurality of subfields, and dividing each of the plurality of second design data into a plurality of third design data corresponding to the plurality of unit fields; evaluating quality of resist resolution to a predetermined dimension on each of the plurality of unit fields; creating a table which defines a unit field having an acceptable resist resolution and a unit field having a rejectable resist resolution among the plurality of unit fields based on an evaluation result acquired by the evaluating the quality of the resist resolution; judging whether or not each of the plurality of third design data corresponds to data having the predetermined dimension and corresponds to a pattern falling in the unit field which the quality of the resist resolution is rejectable based on the predetermined dimension and the table; and converting data judged to correspond to the data among the plurality of third design data into first drawing data after performing a coordinate conversion so that the data fall in the unit field which the resist resolution is acceptable, and converting data judged not to correspond to the data among the plurality of third design data into second drawing data without performing the coordinate conversion. According to an aspect of the present invention, there is provided a charged beam drawing apparatus to draw a pattern on a drawing area of a sample by irradiating a charged beam onto the sample, the pattern being drawn using a unit field as a drawing unit, the charged beam drawing apparatus comprising: a first dividing section configured to divide the drawing area into two or more hierarchical fields including a plurality of main fields, a plurality of subfields which are lower in layer than the plurality of main fields and a plurality of unit fields which are lower in layer than the plurality of subfields, a second dividing section configured to divide design data corresponding to the pattern to be drawn on the drawing area into a plurality of first design data corresponding to the plurality of main fields, dividing each of the plurality of first design data into a plurality of second design data corresponding to the plurality of subfields, and dividing each of the plurality of second design data into a plurality of third design data corresponding to the plurality of unit fields; a resolution evaluating section configured to evaluate quality of resist resolution to a predetermined dimension on each of the plurality of unit fields; a table creating section configured to create a table which relates the plurality of unit fields to the quality of the resist resolution based on an evaluation result acquired by the evaluating the quality of the resist resolution; a judging section configured to judge whether or not each of the plurality of third design data corresponds to data having the predetermined dimension and corresponds to a pattern falling in the unit field which the quality of the resist resolution is rejectable based on the predetermined dimension and the table; a coordinate converting section configured to convert a coordinate of data judged to correspond to the data among the plurality of third design data into a coordinate so that the data fall in the unit field which the resist resolution is acceptable, a first data converting section configured to convert the third design data whose coordinate is converted by the coordinate converting section into a first drawing data; a second data converting section configured to convert data judged not to correspond to the data among the plurality of third design data into a second drawing data without performing the coordinate conversion; and a drawing section configured to draw the pattern by referring to drawing data including the first and second drawing data and irradiating the charged beam onto the sample, the drawing section drawing patterns in the subfields by referring to the first drawing data using the unit field as a drawing unit for each of the plurality of subfields, and in a case where there exists a pattern not being drawn in the subfields, the drawing section drawing the pattern not being drawn on a desired position in the subfields by referring to the second drawing data and by moving the sample, or by referring to the second drawing data and by adjusting a deflection position of the charged beam on the subfields. According to an aspect of the present invention, there is provided semiconductor device manufacturing method comprising: preparing a sample including a substrate and a resist film formed on the substrate; and drawing a pattern on the resist film by a charged beam drawing method according to an aspect of the present invention. Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a flow chart showing an electron beam drawing data creation method of an embodiment. FIG. 2 is a flow chart showing an electron beam drawing method of the present embodiment. First, design data of a device pattern to be formed on a wafer (sample) is prepared (step S1). The above design data is prepared beforehand, or newly created by a designer. The device pattern includes a plurality of patterns. The design data includes a plurality of data (pattern data) corresponding to these plural patterns. Next, the design data is divided into meshes, for each field corresponding to the deflection width of a drawing apparatus (step S2). The configuration of fields in the present embodiment, as shown in FIG. 3, is provided in such a manner that a chip 2 on a wafer 1 is divided into a plurality (n pieces) of fields (main fields) 3, the main field 3 is divided into a plurality (m pieces) of areas (subfields) 4, and the subfield 4 is divided into a plurality (16 pieces) of areas (divided subfields) 5. Meanwhile, dimensions to become a critical pattern in each subfield (critical pattern dimensions) are set based on the above design data (step S3). Further, a resolution evaluation of resist pattern (evaluation of quality of resolution of resist pattern) in each subfield is performed (step S4). Based on the result of the above resolution evaluation (evaluation of the quality of the resolution), each divided subfield is classified as a divided subfield whose resolution is acceptable (hereinafter referred to as “OK area”) or a divided subfield whose resolution is rejectable (hereinafter referred to as “NG area”). In addition, based on the result of the above classification, a distribution table in which “OK areas” with acceptable resolution and “NG areas” with rejectable resolution in the subfield are specified (OK/NG area distribution table) is created (step S5). In the case of the subfield shown in FIG. 14, 2×2 divided subfields at the center become OK areas, 12 divided subfields outside thereof become NG areas, and a distribution table including these items of information is created, as shown in FIG. 4. The above resolution evaluation is carried out to patterns having minimum dimensions necessary for circuit operation. More specifically, a resist is applied onto a wafer, a pattern is drawn on the above resist, the resist having the pattern drawn thereon is developed and thereby a resist pattern is formed. Thereafter, dimensional variations of the resist pattern in the field are evaluated. The wafer and the resist are same as a wafer and a resist to be used practically. As another method of the resolution evaluation, there is a real time evaluation method. For example, there is a real time evaluation method using a beam calibration mark provided beforehand on a movable stage of a drawing apparatus. More specifically, first, one of plural divided subfields is selected. Herein, the number of divided subfields is 16. Next, the position of the movable stage is set so that the beam calibration mark should be set at the position corresponding to the selected divided subfield (first step). Next, the beam calibration mark on the movable stage is scanned with an electron beam (second step). Next, an intensity profile of the electron beam that has scanned the beam calibration mark is acquired (third step). The first to third steps are carried out to remaining divided subfields (fourth step). In the case of using the above evaluation method, the resolution distribution in the filed is evaluated in real time manners. Therefore, even if the apparatus conditions change owing to changes over time and the like, it is possible to suppress defects of the pattern resolution. Thereby, it becomes possible to further improve the manufacturing yields of semiconductor products. Before the critical pattern dimension setting (step S3), the resolution evaluation (step S4) and the OK/NG area distribution table (step S5) may be performed, or alternatively, the step S3 and the steps S4, S5 may be performed in parallel (simultaneously). Next, with regard to the pattern size and pattern position of each pattern data in the design data, two conditions, (1) whether the pattern size is equal to the critical dimensions or less or not, and (2) whether the pattern position is in the NG area or not, are judged (step S6). As the result of the judgment, pattern data that does not satisfy the above (1) and (2) at the same time are, in normal manners, converted into a drawing data format corresponding to the drawing apparatus (step S7). In the case of FIG. 14, the design data 92 to 95 are the pattern data that does not satisfy the above (1) and (2) at the same time. In FIG. 5, drawing data 92′ to 95′ corresponding to the design data 92 to 95 converted into the drawing data format are shown schematically. In FIG. 5, the area entangled by a dotted line corresponds to an OK area, and the outside of the area entangled by the dotted line corresponds to an NG area. The pattern data converted into the drawing data format (drawing data) is recorded (stored) into a first drawing data storage device (step S8). Thereafter, the procedure goes back to the step S6, where judgment is performed on the next pattern data. on the other hand, as the result of the judgment in step S6, the following process (step S9) is performed to the pattern data that satisfies the above (1) and (2) at the same time. That is, a coordinate conversion is carried out so that the pattern data falls in the OK area. The coordinate conversion is a coordinate conversion on the design data. In the case of FIG. 14, the patterns 96, 97 become the pattern data that satisfies the above (1) and (2) at the same time. In FIG. 6, drawing data 96′ corresponding to the data 96 converted into the drawing data format is shown schematically. In FIG. 7, drawing data 97′ corresponding to the data 97 converted into the drawing data format is shown schematically. In FIGS. 6 and 7, the area entangled by a dotted line corresponds to an OK area, and the outside of the area entangled by the dotted line corresponds to an NG area. Thereafter, in the same manner as in steps S7, S8, the pattern data is converted into the drawing data format, and is recorded into a second drawing data storage device (steps S10, S11). The first drawing data storage device and the second drawing data storage device may be one common drawing data storage device. Thereafter, the procedure goes back to the step S6, where judgment is performed on the next pattern data. In this manner, the judgment in step S6 is performed to all the pattern data. As a result, the drawing data are divided into two groups, i.e., those obtained by converting the pattern data normally into the drawing data format without performing the coordinate conversion (normal drawing data), and those obtained by converting the pattern data into the drawing data format after performing the coordinate conversion (coordinate-converted drawing data). Further, the coordinate-converted drawing data are divided into a plurality of groups, except the case where all the pattern data are coordinate-converted in the same manner. The above processes are carried out to each subfield of each main field, and thereby necessary drawing data are acquired. Next, an electron beam drawing method using the electron beam drawing data obtained by the creation method of the present embodiment mentioned above will be explained with reference to FIG. 2. In FIG. 2, MFi·SUBj shows a subfield SUBj (j=j, . . . , m) in a main field MFi (i=1, . . . , n). First, the first MFi·SUBj (i=1, j=1) is selected, the normal drawing data concerning MF1·SUB1 is referred to, and it is judged whether there is normal drawing data or not (steps S12, S13). When it is judged that there is normal drawing data, the electron beam drawing apparatus sequentially draws patterns in the OK areas onto a desired position in the resists on the wafer in normal manners (step S14). In the case of FIG. 14, the patterns corresponding to the design data 92 to 95 are sequentially drawn onto a desired position in the resists on the wafer in normal manners. On the other hand, when it is judged that there is not normal drawing data and after the completion of the step S14, it is judged whether or not there is any pattern not drawn yet in the above MFi·SUBj (step S15). As a result of the judgment, when there are patterns not drawn yet, i.e., when there are patterns in the NG area, and the coordinate conversion of the pattern data is performed, the coordinate-converted drawing data is referred to, and the electron beam drawing apparatus sequentially draws the patterns in the NG area onto the resists on the wafer (step S16). In the case of FIG. 14, the patterns corresponding to the design data 96, 97 are sequentially drawn onto a desired position in the resists on the wafer. Herein, in the step S16, an X-Y stage (movable stage) having the wafer loaded thereon is moved, or the irradiation position of the electron beam on the wafer (EB irradiation position) is changed, so that the patterns should be drawn onto a desired position on the resists on the wafer. The deflection of the EB irradiation position can be performed by a deflector that performs the positioning of the electron beam in the subfield. Next, j is changed into j+1, and the steps S14, S15 are performed. These steps S13 to S16 are carried out until j becomes m in step S17. That is, they are carried out until drawing of all the patterns in all the subfields in the main field MFi (herein MF1) is completed. Next, i is changed into i+1, and the steps S12 to S17 are performed. These steps S12 to S17 are carried out until i becomes n in step S12. That is, they are carried out until drawing of all the patterns in all the subfields in all the main fields is completed. FIG. 8 is a diagram schematically showing a configuration of a charged beam drawing apparatus for embodying the electron beam drawing data creation method and the electron beam drawing method of the present embodiment described above. The charged beam drawing apparatus of the present embodiment includes a drawing data creating unit 41 for creating electron beam drawing data, and a drawing apparatus 42 for performing electron beam drawing by use of the electron beam drawing data created by the drawing data creating unit 41. The charged beam drawing apparatus of the present embodiment differs from the conventional one in that it includes the drawing data creating unit 41. Further, the drawing apparatus 42 is basically same as the conventional drawing apparatus, except that drawing data to be used are different, and that in the case of performing drawing by use of the coordinate-converted drawing data, the X-Y stage is moved, or the EB irradiation position on the wafer is changed, so that the above patterns should be drawn on a desired position in the resists on the wafer. The drawing data creating unit 41, as shown in FIG. 8, includes a resolution evaluation device 51, a table creating unit 52, a storage device 53, a field dividing circuit 54, a critical pattern dimension setting circuit 55, a judging circuit 56, a first data converting circuit 57, a first drawing data storage device 58, a coordinate converting circuit 59, a second data converting circuit 60, and a second drawing data storage device 61. The resolution evaluation device 51 performs a resolution evaluation of resist pattern (evaluation of quality of resolution of resist pattern) in each subfield. The table creating unit 52 creates the OK/NG area distribution table based on the result of the resolution evaluation acquired by the resolution evaluation device 51. The storage device 53 records (stores) the OK/NG area distribution table created by the table creating unit 52. The field dividing circuit 54 divides the design data into meshes for each field corresponding to the deflection width of the drawing apparatus 42. The critical pattern dimension setting circuit 55 sets the critical pattern dimensions in each subfield based on the design data. The judging circuit 56 judges, with regard to the pattern size and pattern position of each pattern data in the design data, two conditions, (1) whether or not the pattern size is equal to the critical dimensions or less, and (2) whether or not the pattern position is in the NG area. The first data converting circuit 57 converts pattern data that are judged not to satisfy the above (1) and (2) at the same time by the judging circuit 56 into a drawing data format corresponding to the drawing apparatus 42 in normal manners. The first drawing data storage device 58 records (stores) the pattern data converted into the drawing data format (drawing data) by the first data converting circuit 57. The coordinate converting circuit 59 performs a coordinate conversion so that the pattern data judged to satisfy the above (1) and (2) at the same time by the judging circuit 56 is within in the OK area. The second data converting circuit 60 converts the pattern data converted by the coordinate converting circuit 59 into the drawing data format corresponding to the drawing apparatus 42. The second drawing data storage device 61 records (stores) the pattern data converted into the drawing data format by the second data converting circuit 60 (drawing data). The first data converting circuit 57 and the second data converting circuit 60 may be one common data converting circuit. In the same manner, the first drawing data storage device 58 and the second drawing data storage device 61 may be one common drawing data storage device. FIG. 9 is a diagram schematically showing a configuration of the drawing apparatus 42. An electron beam 12 emitted from an electron gun 11 goes through a current limit aperture mask 13. The current density of the electron beam 12 that has gone through the current limit aperture mask 13 is adjusted by a condenser lens 14. The electron beam 12 whose current density is adjusted illuminates a first shaping aperture mask 15 evenly. The electron beam (image) that has gone through the first shaping aperture mask 15 is focused onto a second shaping aperture (CP aperture) 20 by a projector lens 18. An optical overlapping degree of the first shaping aperture mask 15 and the second shaping aperture mask 20 is controlled by a shaping deflector 19. The optical overlapping degree is judged by the overlapping with the second shaping aperture mask 20 formed by the shaping deflector 19. The image by the optical overlapping of the first shaping aperture mask 15 and the second shaping aperture mask 20 is reduced by a reducing lens 21. This reduced image is focused onto a wafer (sample) 27 by an objective lens 23. The condenser lens 14, the projector lens 18, the reducing lens 21 and the objective lens 23 are controlled by a lens controlling circuit 29. The position of the electron beam 12 on the wafer 27 is set by the voltage applied to an objective deflector 22. The objective deflector 22 includes a main deflector 221 and a sub deflector 222. The main deflector 221 positions the electron beam in the subfield in the main field, and the sub deflector 222 positions the electron beam in the divided subfield in the subfield. The voltage applied to the main deflector 221 and the sub deflector 222 is given from a beam deflecting circuit 32. That is, the beam deflecting circuit 32 supplies the voltage corresponding to the data read from a storage device 35 (pattern data to be drawn) to the main deflector 221 and the sub deflector 222. Depending on the size of the voltage supplied to the main deflector 221 and the sub deflector 222, the deflection amount of the electron beam 12 changes, and the electron beam 12 on the subfield and the divided subfield is judged in correspondence to this deflection amount. The main deflector 221 and the sub deflector 222 and the shaping deflector 19 are, for example, electrostatic deflectors. By use of the above deflectors, it is possible to deflect the electron beam 12 at a high speed and high precision. The electron beam 12 that has gone through the second shaping aperture mask 20, the reducing lens 21 and the objective lens 23 is detected by a detector 24. Thereby, the intensity distribution of the electron beam that has gone through the second shaping aperture mask 20, and is in a surface nearly parallel with the second shaping aperture 20 just before being irradiated onto the wafer 27 can be detected. The detector 24 is made of for example a Faraday cup, and the intensity of the electrode beam is given for example by a current. The wafer 27 together with a mark stand 25 is arranged on a movable stage 26. By moving the movable stage 26, the wafer 27, the Faraday cup 28 or the mark stand 25 is selected. The movement of the movable stage 26 is controlled by a stage controlling circuit 34. Further, when the position of the electron beam 12 on the wafer 27 is moved, the electron beam 12 is deflected onto a blanking aperture mask 16 by a blanking deflector 17, so that unnecessary portions on the wafer 27 should not be exposed. Thereby, the electron beam does not reach the surface of the wafer 27, so that the unnecessary portions on the wafer 27 are prevented from being exposed. The voltage to be applied to the blanking deflector 17 is given from the blanking deflecting circuit 30. That is, the blanking deflecting circuit 30 applies the voltage corresponding to the data read from the storage device 35 (pattern data to be drawn) to the blanking deflector 17. Various data necessary for drawing are recorded (stored) in the storage device 35. In the storage device 35, drawing data sent from drawing data storage devices 58, 61 are also recorded (stored). The data read from the storage device 35 are sent to various circuits 29, 30, 31, 32 and 34. Next, a semiconductor device manufacturing method of the present embodiment will be explained hereinafter. The semiconductor device manufacturing method of the present embodiment is a method including a step where a pattern is drawn on a resist film by the charged beam drawing method of the present embodiment. More specifically, the method is as described below. First, a resist film is applied onto a substrate including a semiconductor substrate. The semiconductor substrate is, for example, a silicone substrate, or an SOI substrate. Next, a pattern is drawn on the resist film by the charged beam drawing method of the present embodiment. Thereafter, the resist film is developed, thereby a resist pattern is formed. Next, using the resist pattern as a mask, the substrate is etched, thereby a pattern is formed on the substrate. Herein, when the underlying layer of the resist film (most top layer of substrate) is a polycrystalline silicone film or a metal film, an electrode pattern, a wire pattern and the like are formed. When the underlying layer of the resist film is an insulation film, a fine contact hole pattern, a gate insulation film and the like are formed. When the underlying layer of the resist is the semiconductor substrate, an isolation trench (STI) and the like are formed. Meanwhile, the present invention is not limited to the above embodiment. For example, in the above embodiment, the case of an OK/NG area distribution where portions near the center of the subfield are OK areas has been explained. However, the present invention is effective also when applied to other OK/NG area distribution than the above. For example, as shown in FIG. 10, in some conditions of the drawing apparatus, there is an OK/NG area distribution where portions displaced from the field center are OK areas. In such a case, drawing data as shown in FIGS. 11 to 13 are created, and drawing is performed, thereby the same effects as in the present embodiment can be attained. FIG. 11 shows design data 92 to 94 in the NG areas and data 95 to 97 in the OK areas, i.e., drawing data corresponding to patterns not requiring the coordinate conversion. FIG. 12 shows drawing data created by performing the coordinate conversion on data 97 in the NG area in FIG. 10. FIG. 13 shows drawing data created by performing the coordinate conversion on data 95, 97 in the NG area in FIG. 10. The data 95 to 97 corresponding to the pattern of the critical pattern dimensions lie over the NG areas and the OK areas. The data 95 to 97 in the OK areas becomes drawing data 951′ to 971′ without the coordinate conversion, and the data 95 to 97 in the NG areas becomes drawing data 952′ to 972′ through the coordinate conversion. Further, in the above embodiment, the case of the drawing apparatus and the drawing method using the electron beam has been explained. However, the present invention may be also applied to a drawing apparatus and a drawing method using other charged beam such as an ion bean in the same manners. Furthermore, in the above embodiment, the case where a wafer is used as a sample (semiconductor device manufacturing method) has been explained. However, the present invention may be also applied to a case using a transparent substrate such as a quartz substrate (photo mask manufacturing method, flat panel display manufacturing method) in the same manners. Moreover, in the above embodiment, the case where the drawing area is divided into two hierarchical fields has been explained. However, the drawing area may be divided into three or more hierarchical fields. For example, three hierarchical fields include a plurality of main fields, a plurality of subfields, sub-subfields of the layer lower than the above plural subfields and divided subfields (unit fields) of the layer lower than the above sub-subfields. Corresponding to this, deflectors include three stage deflectors of a main deflector, a sub deflector and a sub-sub deflector. Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.
	description	The present invention contains subject matter related to Japanese Patent Application JP 2007-327921 filed in the Japanese Patent Office on Dec. 19, 2007, the entire contents of which being incorporated herein by reference. 1. Field of the Invention The present invention relates to an electromagnetic-wave suppressing material used to suppress undesired electromagnetic radiation from an electronic apparatus, an electromagnetic-wave suppressing device including such an electromagnetic-wave suppressing material, and an electronic apparatus having the electromagnetic-wave suppressing device including the electromagnetic-wave suppressing material. 2. Description of the Related Art An increase in use of high-frequency electromagnetic waves in recent years has newly caused environmental disadvantages such as malfunction of an apparatus due to electromagnetic wave noise and undesirable influences of such electromagnetic radiation on the human's brain and body. For example, a 2.45 GHz band, one of frequency bands available in license-exempt wireless communications, has been used in many apparatuses for wireless LAN (IEEE 802.11b), Blue Tooth®, ISM (Industrial, Scientific and Medical), and so on. Furthermore, speedup and digitalization of clock frequencies of information apparatuses may cause harmonics in such a frequency band. Thus, risks of the occurrence of interference are highly increasing because of exponential increases in numbers and diversities of both potential electromagnetic wave source and interference-damage receiving side. In order to cope with such electromagnetic interferences (EMI), individual apparatuses may need to be sufficiently resistant to any influence of electromagnetic waves coming from the outside (i.e., an improvement in immunity). Simultaneously, the apparatuses may need to be prevented from radiating undesired electromagnetic waves which may interfere with normal operations of other apparatuses (i.e., suppression of emission). Such requirements are collectively referred to as electromagnetic compatibility (EMC). Various standards have been defined for allowing electronic apparatuses to ensure electromagnetic compatibility under electromagnetic environment. For obtaining EMC in circuit design, a disturbance-suppressing element has been mainly used as a circuit element for preventing an electromagnetic disturbance wave from entering an electronic apparatus in addition to reducing the electromagnetic disturbance wave generated from the electronic apparatus. Examples of the disturbance-suppressing element include a varistor and an LC filter which is a combination of capacitors and induction coils. These elements are designed so that they have a small loss when desired signals pass through the elements and have a large reflection loss and passage loss against disturbance waves. These elements can be combined by any suitable method and used in almost all electronic circuits. However, the combination of a disturbance-suppressing element and a circuit element may cause a specific resonance frequency. In this case, voltage and current waveforms may oscillate to distort a desired signal waveform. Besides, the wavelength of an electromagnetic wave in the range of GHz band frequencies may be close to the circuit length of an electromagnetic circuit. Thus, the circuit itself may act as an antenna for the electromagnetic wave, possibly causing the circuit to malfunction. Thus, when the EMC may not be obtained at the stage of circuit design, it has been attempted to obtain EMC in the stage of packaging design. In recent years, an attention has been drawn to the use of a material for suppressing or absorbing an electromagnetic wave (hereinafter, collectively referred to as an “electromagnetic-wave suppressing material”) in the form of a sheet prepared by mixing magnetic powder with resin. The principle of the electromagnetic-wave absorption in the electromagnetic-wave suppressing or absorbing material is a conversion of most electromagnetic-wave energy incident thereon into thermal energy in the inside of the material. Therefore, each of the electromagnetic-wave suppressing and absorbing materials can lower the amounts of both the energy reflected in the forward direction and the energy permeated in the backward direction. Here, mechanisms of converting electromagnetic-wave energy to thermal energy can be mainly classified into three types: conduction loss, dielectric loss, and magnetic loss. Electromagnetic-wave absorption energy per unit volume, P [W/m3], is expressed by the following Equation 1 using electric field E, magnetic field H, and electromagnetic-wave frequency f. P = 1 2 ⁢ σ ⁢  E  2 + π ⁢ ⁢ f ⁢ ⁢ ɛ ″ ⁢  E  2 + π ⁢ ⁢ f ⁢ ⁢ μ ″ ⁢  H  2 [ Equation ⁢ ⁢ 1 ] Electric conductivity: σComplex permittivity: ∈=∈′−j∈″Complex magnetic permeability: μ=μ′−jμ″ In the Equation 1, the first term represents conduction loss, the second term represents dielectric loss, and the third term represents magnetic loss. Magnetic materials have been typically used as materials for suppressing electromagnetic waves in the high-frequency band. Thus, magnetic sheets made of magnetic materials are designed to increase the magnetic permeability, the third term μ″ of the above Equation 1, for suppressing and absorbing electromagnetic waves. On the other hand, the present inventors have proposed a material having a high permittivity ∈″, the second term of the above Equation 1, indicating the dielectric loss at a frequency in the MHz or GHz band (see Japanese Unexamined Patent Application Publication No. 2006-73991). The present inventors have paid their attention to the permittivity of a liquid material with ions such as an electrolyte and have proposed an electromagnetic-wave suppressing material with a high electromagnetic-wave absorbing efficiency as described above. The electrolyte, which contains ions, causes ionic conduction in response to the applied electric field. Unless it is a superconductive material, there is a resistance component in the electrolyte. Accordingly, the ionic conductance is influenced by the amount of such resistance component, though depending on the kind of a solvent or the like. Thus, such a resistance component may correspond to the loss part ∈r″ of the specific permittivity. In addition, the loss part ∈r″ of the specific permittivity may have a value in the range of several tens to several hundreds or more at a frequency of 1 GHz or less. In other words, the electrolyte with ions may convert the incident electromagnetic-wave energy into Joule heat and also may absorb the energy. However, any water-containing material, such as an electrolyte, may require a difficult technology in terms of volatilization of water while securing the reliability thereof in “property retention for several years or for ten or more years”. Therefore, the feature of preventing water from volatilization may need to be added not to the electromagnetic-wave suppressing material but a material laminated thereon. In consideration of the above reliability, the present inventors have proposed an electromagnetic-wave suppressing material using an ionic liquid (ion liquid) containing only ions (see Japanese Unexamined Patent Application Publication No. 2007-27470). The use of the ionic liquid (ion liquid) containing only ions leads to an increase in the amount of electromagnetic-wave suppression/absorption. Further, volatilization of a liquid material can be prevented by taking advantage of its boiling point of several hundred degrees Celsius. Furthermore, the ionic liquid containing only ions has the properties of nonvolatility, nonflammability, thermal stability, chemical stability, high ionic conductivity, and electric polarization tolerance. However, in the case of using an ionic liquid (ion liquid) such as one described above alone, the effects of suppressing and absorbing electromagnetic waves can be determined by the physical properties of the ionic liquid (ion liquid). Thus, it is difficult to obtain further improvements in electromagnetic-wave suppression/absorption effects. Furthermore, the ionic liquid has a low viscosity. For making an electromagnetic-wave suppressing material in sheet form or any desired form, a material having a certain degree of viscosity can be made in sheet form without difficulties. However, a sufficient viscosity may not be obtained with the ionic liquid alone. It is desirable to provide an electromagnetic-wave suppressing material having an increased electromagnetic-wave suppressing effect and, from design and manufacture perspective, flexibly of making into any of various forms while securing high reliability. It is also desirable to provide an electromagnetic-wave suppressing device using the electromagnetic-wave suppressing material. Furthermore, it is desirable to provide an electronic apparatus including the electromagnetic-wave suppressing material and the electromagnetic-wave suppressing device. According to an embodiment of the present invention, there is provided an electromagnetic-wave suppressing material including an ionic liquid and nanometer-order particles mixed with the ionic liquid, wherein 10 wt % or more of the nanometer-order particles is mixed with respect to 100 wt % of the ionic liquid. According to another embodiment of the present invention, there is provided an electromagnetic-wave suppressing device including the electromagnetic-wave suppressing material according to the above embodiment of the invention. According to further embodiment of the present invention, there is provided an electronic apparatus including an integrated circuit device, a wiring line, and the electromagnetic-wave suppressing device according to the above embodiment, where the electromagnetic-wave suppressing device is located in the vicinity of the integrated circuit device or the wiring line. According to the configuration of the electromagnetic-wave suppressing material of the above embodiment of the invention, a sufficient viscosity can be obtained by mixing 10 wt % or more of nanometer-order particles with respect to 100 wt % of an ionic liquid (ion liquid). Thus, the electromagnetic-wave suppressing material in slurry or paste form can be obtained. Therefore, the electromagnetic-wave suppressing material can be made in sheet form or any desired form. In addition, the ionic liquid is excellent in nonvolatility, nonflammability, thermal stability, and chemical stability, so that an electromagnetic-wave suppressing material can be provided with the properties of the ionic liquid (ion liquid). Furthermore, the electromagnetic-wave suppressing material can be provided with the properties of nanometer-order particles, such as permittivity and magnetic permeability thereof, and the physical properties of the electromagnetic-wave suppressing material can be controlled. According to the configuration of the electromagnetic-wave suppressing device of the above embodiment of the invention, it is made of the electromagnetic-wave suppressing material of the above embodiment of the invention. Since the electromagnetic-wave suppressing material can be made in sheet form or any desired form, the electromagnetic-wave suppressing device can be made in any form. In addition, according to the configuration of the electronic apparatus of the above embodiment of the invention, the apparatus includes the electromagnetic-wave suppressing device located in the vicinity of an integrated circuit device or a wiring line, so that radiation of the electromagnetic waves generated from an integrated circuit device or a wiring line to the outside of the apparatus can be suppressed. Furthermore, the electromagnetic-wave suppressing device of the above embodiment of the invention can be made in any desired form. Thus, the electromagnetic-wave suppressing device can be easily mounted on any place in the vicinity of an integrated circuit device or a wiring line in the electronic apparatus. According to the electromagnetic-wave suppressing material and the electromagnetic-wave suppressing device of the above embodiments, the electromagnetic-wave suppressing material can be made in sheet form or any desired form and thus the electromagnetic-wave suppressing device in any desired form can be designed. In addition, since the ionic liquid included in the electromagnetic-wave suppressing material is excellent in nonvolatility, nonflammability, thermal stability, and chemical stability, both the electromagnetic-wave suppressing material and the electromagnetic-wave suppressing device can be provided with high environmental reliability against temperature changes or the like. Furthermore, both the electromagnetic-wave suppressing material and the electromagnetic-wave suppressing device can be provided with the properties of nanometer-order particles, such as permittivity and magnetic permeability thereof, and the physical properties of the electromagnetic-wave suppressing material can be controlled, so that further improvements in effects of suppressing and absorbing electromagnetic waves can be obtained. Furthermore, according to the electronic apparatus of the above embodiment of the invention, radiation of the electromagnetic waves generated from an integrated circuit device or a wiring line to the outside of the apparatus can be suppressed. Thus, the electronic apparatus with electromagnetic compatibility and high reliability for stable operation can be obtained. First, the outline of an embodiment of the present invention will be described. According to an embodiment of the present invention, an electromagnetic-wave suppressing material includes a mixture of an ionic liquid (ion liquid) and nanometer-order particles. The ionic liquid (ion liquid) preferably contains positive ions and negative ions. For the positive ions (cations), any of aromatic compounds such as imidazolium salts and pyridinium salts, aliphatic quaternary ammonium salts, and aliphatic cyclic ammonium salts can be used. For the negative ions (anions), any of inorganic ions, such as tetraflluoroborate (BF4−) and 6-fluorophosphate (PF6−), and fluorine-containing organic anions, such as CF3SO2− and perfluoro sulfone imide (CF3SO2)2N−: TFSI) can be used. Combinations of these ions are typically used as materials for the ionic liquid. However, the present embodiment is not limited to these materials. FIGS. 1A to 1C represent chemical formulae of materials of ionic liquids prepared with different combinations of the above materials. Such materials are used for the ionic liquid in the embodiment of the invention. FIG. 1A represents the chemical formula of the material prepared by combining 1-ethyl-3-methyl imidazolium (EMI), one of imidazolium salts, with an anionic ion X− ((CF3SO2)2N−,BF4−,PF6−, or the like). FIG. 1B represents the chemical formula of the material prepared by combining 3-butyl pyridium (BP), one of pyridinium salts, with the anionic ion X−. FIG. 1C represents the chemical formula of the material prepared by combining trimethyl hexyl ammonium, one of aliphatic quaternary ammonium salts, with the anionic ion X−. Ionic liquids including such materials have the properties of nonvolatility, nonflammability, thermal stability, chemical stability (being hardly changed over time because ions may not react with other components), high ion conductivity, and electric polarization tolerance. In such ionic liquids, amounts of electromagnetic-wave suppression and absorption are increased by ionic conduction caused in the ionic liquid due to the action of electromagnetic wave and Joule heat generated by the collision of ions in the ionic conduction. In particular, such ionic liquids are excellent in nonvolatility and stability because the coagulating point thereof is −20° C. and the boiling point or the decomposition point thereof is as high as several hundred degrees Celsius. In the embodiment of the present invention, the nanometer-order particles mixed with an ionic liquid may preferably be a dielectric material with a specific permittivity of 10 or more at 1 kHz at room temperature or a magnetic material with a relative magnetic permeability of 100 or more at 100 MHz at room temperature. The use of such a dielectric or magnetic material as nanometer-order particles can provide the electromagnetic-wave suppressing material with additional properties of permittivity, magnetic permeability, and the like. Examples of the dielectric material with a specific permittivity of 10 or more at 1 kHz at room temperature include barium titanate, lead zirconium titanate, and titanium oxide. In addition, examples of the magnetic material with a relative magnetic permeability of 100 or more at 100 MHz at room temperature include Mn—Zn ferrite, Ni—Zn ferrite, and Cu—Zn ferrite. Materials of the nanometer-order particles used in the embodiment of the invention are not limited to these materials. The nanometer-order particles used may be those with a particle size of less than 1 μm, more preferably of about 300 nm or less. The electromagnetic-wave suppressing material can be prepared by mixing 10 wt % of such particles with respect to 100 wt % of the ionic liquid. In this way, the electromagnetic-wave suppressing material can be provided with sufficient viscosity as it is prepared by mixing 10 wt % or more of nanometer-order particles with respect to 100 wt % of an ionic liquid. Furthermore, the electromagnetic-wave suppressing device can be made in slurry or paste form as it is made of such an electromagnetic-wave suppressing material. In other words, it becomes possible to provide electromagnetic-wave suppressing devices in various forms, such as sheet and bulk forms and also in other desired forms. Next, FIGS. 2A to 2C show different configurations of electromagnetic-wave suppressing devices, each of which is made of an electromagnetic-wave suppressing material. Each of the electromagnetic-wave suppressing devices includes an electromagnetic-wave suppressing material 1 prepared by mixing any of the above-described ionic liquids with nanometer-order particles. FIG. 2A shows an electromagnetic-wave suppressing device 21 configured using the electromagnetic-wave suppressing material 1 alone in sheet form or the like. Here, the electromagnetic wave material may be made in bulk form instead of sheet form. FIG. 2B shows an electromagnetic-wave suppressing device 22 configured by covering the electromagnetic-wave suppressing material 1 with a film (sealing member) to be sealed. The film 2 may be a film container with or without electronic-wave absorbability. Preferably, however, it is not a film reflecting electromagnetic waves (e.g., aluminum foil). FIG. 2C shows an electromagnetic-wave suppressing device 23 configured by covering the electromagnetic-wave suppressing material 1 placed on a board 3 with a laminate material 4 made of an insulating material so that the electromagnetic-wave suppressing device 23 can be sealed between the board 3 and the laminate material 4. Measurement of Properties Here, the electromagnetic-wave suppressing material according to the embodiment of the present invention was actually produced and the properties thereof were then investigated. An ionic liquid was prepared using 1-ethyl-3-methyl imidazolium (EMI) as a positive ion and bis-trifluoromethyl sulfonylimide (TFSI) as a negative ion, followed by mixing the ionic liquid with titanium oxide (TiO2) powder with a particle size of about 20 nm to 30 nm as nanometer-order particles. The mixing of these components was carried out using a mixer. The amount of mixed titanium oxide powder was changed to 5 wt %, 10 wt %, and 15 wt % with respect to 100 wt % of the ionic liquid and samples were then prepared for the respective mixing amounts. The samples of the respective mixing amounts were subjected to the measurement of the viscosity of materials in mixture. The results of the viscosity measurement are listed in Table 1. TABLE 1SampleViscosityIonic liquid + TiO2 (5 wt %)154cPIonic liquid + TiO2 (10 wt %)1260cPIonic liquid + TiO2 (15 wt %)>9500cP As shown in Table 1, the higher the amount of titanium oxide to be mixed increases, the more the viscosity increases. In other words, a sufficiently high viscosity of 1000 cP or more was obtained with 10 wt % or more of titanium oxide. Therefore, a desired amount of titanium oxide to be mixed is 10 wt % or more. Here, 1 cP (centipoise)=0.01 P=0.001 Pa·s=1 mPa·s. On the other hand, as a comparative example, a sample was prepared by mixing ferrite powder with a particle size of about 20 μm to 30 μm with the ionic liquid (ion liquid). In the sample of the comparative example, the ionic liquid (ion liquid) and the ferrite powder were separated from each other, so that a mixing state (i.e., slurry or paste state) was not obtained. As a result, it is found that an increase in viscosity can be obtained by mixing the nanometer-order particles with the ionic liquid (ion liquid) in comparison with the ionic liquid alone. Next, the electromagnetic-wave suppressing effects of the respective samples were measured. Here, a method for the measurement will be described with reference to FIGS. 3 and 4. FIGS. 3A and 3B illustrate an electromagnetic-wave suppressing device, where FIG. 3A is a schematic view thereof and FIG. 3B is a cross-sectional view thereof. The electromagnetic-wave suppressing device was prepared by forming a micro-strip line 13 on a board 11 having a ground-potential conductive layer 12 on the backside thereof. A sample 20 was mounted on the micro-strip line 13. Furthermore, the board 11 with a permittivity ∈r of 4.1 had a height of 100.0 mm, a width of 100.0 mm, and a thickness of 1.5 mm. On the other hand, the micro-strip line 13 had a film thickness of about 0.025 mm, a width of 3.0 mm, and a length of 100.0 mm. In addition, the micro-strip line 13 is designed to have a characteristic impedance of about 50 Ω. For comparatively evaluating the electromagnetic-wave suppressing effects of the respective samples in the same volume, a vessel (the inner dimensions thereof: 22 mm×22 mm×5 mm, the wall thickness thereof: 0.2 mm) 14 for mounting a sample thereon was arranged on the micro-strip line 13. Then, the sample 20 was placed in the vessel 14. Furthermore, as shown in FIG. 4, a network analyzer 15 was used as a measuring apparatus. The network analyzer 15 was connected to the both ends of the micro-strip line 13 through wiring lines 16. Then, an input terminal 17A and an output terminal 17B were provided to the terminal areas between the wiring lines 16 and the micro-strip line 13. Then, a signal was input from the input side of the micro-strip line 13 and output to the output side thereof to determine the reflection and transmission properties of the sample 20. In addition, as a comparative example, the same measurement was carried out without the sample 20. When the signal is input into the input side of the micro-strip line 13, the loss amount is obtained by subtracting both the reflected amount (S11) and the transmitted amount (S21) from the input amount. The ratio of the loss amount to the input amount is obtained as a loss ratio (Loss). The reflected amount (S11) is obtained from the measured reflection property, while the transmitted amount (S12) is obtained from the measured transmission property. The frequency characteristic of loss ratio was calculated from the input amount, and the reflection amount and the transmitted amount. FIG. 5 represents the properties of loss absorbed by the sample 20 or the micro-strip board 11 as the results of measuring the electromagnetic-wave suppressing effects. As shown in FIG. 5, the vertical axis represents the ratio of loss (Loss) and the horizontal axis represents the frequency. Furthermore, FIG. 6 shows the amount of loss in each sample 20, which is obtained by subtracting the amount of loss without the sample 20 from the measurement result shown in FIG. 5, or the amount of loss in the sample 20 from which the loss in the micro-strip board 11 was removed (ΔLoss: an electromagnetic-wave suppressing effect). FIGS. 5 and 6 indicate that an increase in the amount of nanometer-order titanium oxide powder mixed with the ionic liquid (ion liquid) leads to an increase in an electromagnetic-wave suppressing effect. Such results may be obtained, because the permittivity (or conductivity) of the sample 20 is changed by mixing titanium oxide. Furthermore, the specific permittivity of the respective samples were measured. The results of the measurement are shown in FIG. 7. FIG. 7 indicates that an increase in the amount of titanium oxide mixed leads to an increase in the specific permittivity of the respective samples. A change in physical property may be related to a change in the amount of electronic wave suppression. Thus, an electromagnetic-wave suppressing material in a slurry or paste form can be provided by mixing nanometer-order dielectric material powder with an ionic liquid (ion liquid). In addition, a permittivity can also be controlled. Furthermore, the same effects as that of the dielectric material can be obtained even if nanometer-order magnetic material powder is mixed with an ionic liquid (ion liquid). In addition, the ionic liquid (ion liquid) can be further provided with the magnetic permeability. Therefore, it becomes possible to provide a suitable material for suppressing electromagnetic waves and design an electromagnetic-wave suppressing device using such a material by mixing the nanometer-order particles of the dielectric material or the magnetic material with the ionic liquid (ion liquid). Next, examples of an electronic apparatus according to an embodiment of the present invention will be described. Here, the electromagnetic-wave suppressing material and the electromagnetic-wave suppressing device according to an embodiment of the present invention are included in these electronic apparatuses. FIG. 8 is a schematic perspective view illustrating a video camera that is a first example of the electronic apparatus according to an embodiment of the present invention. As shown in FIG. 8, a video camera 30 includes an A-board (printed-wiring board) 31A on which electronic parts are mounted, a B-board (printed-wiring board) 31B on which electronic parts are mounted, and a monitor screen 32. FIG. 9 is a perspective view illustrating main parts of the video camera 30. As shown in FIG. 9, in this video camera 30, the electromagnetic-wave suppressing materials 1 according to an embodiment of the invention may be arranged to hold a flexible-wiring lines 33 electrically connecting the A-board 31A and the B-board 31B. Another electromagnetic-wave suppressing material 1 may be arranged on other places. For example, it may be attached to the upper surface of an integrated circuit (IC) chip 35 or the like mounted on the respective boards 31A and 31B. Further, the electromagnetic-wave suppressing material 1 may be attached not only to the top surface of the IC chip 35 or the like, but also to the side of the IC chip 35 or in the vicinity thereof. In that case also, an electromagnetic-wave suppressing effect can be obtained. Furthermore, the electromagnetic-wave suppressing material according to an embodiment of the present invention can be arranged in the vicinity of wiring lines 34 on the B-board 31B as illustrated in FIG. 9. In this example, the electromagnetic-wave suppressing material 1 is made in sheet form or the like to form the electromagnetic-wave suppressing device with the electromagnetic-wave suppressing material 1 alone in a manner similar to the electromagnetic-wave suppressing device 21 as illustrated in FIG. 2A. In the first example as described above, the radiation of electromagnet waves generated from the IC chip 35 and the wiring lines 33 and 34 can be suppressed with the electromagnetic-wave suppressing materials 1 arranged in the vicinity of the IC chip 35 and the wiring lines 33 and 34. Instead of forming the electromagnetic-wave suppressing device using the electromagnetic-wave suppressing material 1 alone as illustrated in FIG. 9, for example, the electromagnetic-wave suppressing device may be formed such that the electromagnetic-wave suppressing material 1 is sealed with an insulating film. Next, FIG. 10 is a schematic perspective view illustrating a video camera that is a second example of the electronic apparatus according to an embodiment of the present invention. As shown in FIG. 10, a video camera 40 includes a B-board (printed-wiring board) 31B on which electronic parts are mounted and a C-board (printed-wiring board) 31C on which electronic parts are mounted. The video camera 40 further includes a casing 36 and a monitor screen 32. FIG. 11 is a perspective view illustrating main parts of the video camera 40. As shown in FIG. 11, in this video camera 40, the electromagnetic-wave suppressing material 1 according to an embodiment of the invention alone may be arranged to fill the space between the B-board 31B and the C-board 31C when the C-board 31C is arranged in the vicinity of the B-board 31B, where electronic parts such as IC chips 35 are mounted on the respective boards 31B and 31C. In particular, for example, as illustrated in the cross-sectional view of FIG. 12A, the electromagnetic-wave suppressing material 1 can be sandwiched between the mounting side of the B-board 31B and the non-mounting side of the C-board 31C. In addition, for example, as illustrated in the cross-sectional view of FIG. 12B, the electromagnetic-wave suppressing material 1 can be sandwiched between the mounting side of the B-board 31B and the mounting side of the C-board 31C. If there is a risk of short circuit on the surface of such board, the surfaces of the B-board 31B and the C-board 31C may be coated with an insulating laminate film 37 as illustrated in the respective cross-sectional views of FIGS. 12A and 12B. Accordingly, the space between the B-board 31B and the C-board 31C can be filled with the electromagnetic-wave suppressing material 1 alone on the insulating laminate film. Similarly, when the casing 36 is arranged in the vicinity of the C-board 31C, an insulating laminate film 37 is applied to the surface of the C-board 31C as illustrated in the perspective view of FIG. 13 and the cross-sectional view of FIG. 14 so that the space between the C-board 31C and the casing 36 can be filled with the electromagnetic-wave suppressing material 1 of an embodiment of the invention alone. In the second example also, instead of forming the electromagnetic-wave suppressing device using the electromagnetic-wave suppressing material 1 alone, the electromagnetic-wave suppressing device may be formed in other ways such that the electromagnetic-wave suppressing material 1 is sealed with an insulating film. Thus, the electromagnetic-wave suppressing material 1 is provided to at least one of the area of generating inner electromagnetic waves and the area of receiving external electromagnetic waves. Accordingly, the influence of electromagnetic waves to the electronic apparatus or the influence of electromagnetic waves from the electronic apparatus can be suppressed to a minimum. Accordingly, the electronic apparatus with electromagnetic compatibility and high reliability for stable operation can be obtained. FIGS. 2A to 2C illustrate only a few examples of the electromagnetic-wave suppressing device according to an embodiment. According to an embodiment of the present invention, the electromagnetic-wave suppressing device may have any other form because the electromagnetic-wave suppressing material is capable of being prepared in any desired form. FIGS. 15A to 15C are schematic views illustrating other examples of the configuration of an electromagnetic-wave suppressing device according to an embodiment of the present invention. FIG. 15A is a perspective view of the electromagnetic-wave suppressing device and FIG. 15B is a cross-sectional view thereof. As illustrated in FIGS. 15A and 15B, an electromagnetic-wave suppressing device 50 of the example includes a cylindrical resin casing 51, which also serves as a sealing member, sealed with an electromagnetic-wave suppressing material 52. The resin casing 51 is a hollow casing having a cylindrical shape. The hollow casing is filled and sealed with the electromagnetic-wave suppressing material 52 to have a cylindrical form as a whole. As shown in FIG. 15B, the resin casing 51, which becomes a cylindrical form when mounted, is divided in two along the center axis passing through a central opening 53. The divided two halves (hereinafter, referred to as divided cores) 51a and 51b of a sealing member can be opened and closed via a flexible connection part 51c. The divided cores 51a and 51b in a closed combined state forms the cylindrical form. The respective divided cores 51a and 51b have hollow structures to be independently filled and sealed with the electromagnetic-wave suppressing material 52. In addition, the connection part 51c is made of resin with the same quality of materials as that of the divided cores 51a and 51b to connect the outer walls of the divided cores 51a and 51b. Furthermore, the resin casing 51 formed of the divided cores 51a and 51b is made of resin capable of transmitting electromagnetic waves. In addition, the casing 51 has such hardness as to keep the cores in a certain form. The electromagnetic-wave suppressing device 50 can be prepared by injecting the electromagnetic-wave suppressing material 52 into the resin casing 51. FIG. 15C is a perspective view illustrating the state of the electromagnetic-wave suppressing device 50 represented in FIGS. 15A and 15B being attached to a harness 54 that is an electric-signal transmitting medium. When the electromagnetic-wave suppressing device 50 of this example is attached to the harness 54, the divided cores 51a and 51b are opened (the state shown in FIG. 15B) and the harness 54 is then placed in the central opening 53. Subsequently, the divided cores 51a and 51b are closed together to be integrated with the harness 54. Furthermore, the divided cores 51a and 51b can be engaged or joined together using an engaging device (not shown). For example, according to a method, recessed and protruded portions are formed on the divided cores 51a and 51b to engage them together or a tape is used to join them together. Therefore, the divided cores 51a and 51b can be easily attached to the harness 54 of the electromagnetic-wave suppressing device 50 in a manner of holding the harness 54. Furthermore, in this example, the electromagnetic-wave suppressing device 50 may be alternatively prepared by making the electromagnetic-wave suppressing material 52 in sheet form in advance and then fitting the electromagnetic-wave suppressing material 52 in the core-shaped resin casing 51. Alternatively, the sealing member may be, for example, one made of PET, film, glass, or the like instead of the resin casing. The electromagnetic-wave suppressing device 50 of this example is prepared by filling and sealing the hollow cylindrical resin casing 51, which also serves as an sealing member, with the electromagnetic-wave suppressing material 52. Thus, as shown in FIG. 15C, the harness 54 or the like is held by the resin casing 51, so that the electromagnetic-wave suppressing device 50 can suppress electromagnetic wave interference in a high-frequency band. In addition, the resin casing 51 is formed of two divided core halves 51a and 51b connected using a flexible connection part 51c. Thus, it can be easily attached to an electric signal transmitting medium such as the harness 54. In the example as illustrated in FIGS. 15A to 15C, the cylindrical electromagnetic-wave suppressing device 50 is used. Alternatively, the device 50 may be a rectangular-shaped device having a rectangular outer shape and a central opening with a circular cross section. Alternatively, furthermore, it may be made in another form if desired. The present invention is not limited to the above embodiments and may be embodied in several forms without departing from the gist of the invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alterations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof.
	abstract	The invention is an apparatus for producing an IR (infra-red) signature. In the method, the apparatus is mounted on a target to give the target an infra-red signature whereby the target can be acquired by an appropriate weapon sensor.
044973497	summary	BACKGROUND OF THE INVENTION This invention relates to apparatus for mixing a gas and a liquid, and for dispensing the resultant solution. In some fields, especially the medical field, it is desirable to dissolve a gas in a liquid without loss of the gas and without contamination of the solution. One specific use for the apparatus is the dissolving of a radioactive gas such as xenon-133 in a liquid such as saline to provide a radioactive solution and provide for extraction of a portion of the solution for subsequent use such as tracering in medical analysis. For such applications, the dispenser should also provide radioactive shielding for protection of personnel handling the equipment. One such apparatus is shown in U.S. Pat. No. 3,742,988. In this apparatus, a crushable ampule is positioned in a closed container which is charged with the saline. The ampule is crushed or broken by a lead screw positioned in a cap for the container to permit mixture of the gas and liquid. An inlet line provides for introducing the saline into the container, and an outlet line provides for withdrawing the solution. This prior art device has a number of disadvantages. It is not well suited for use with small volumes, in the order of 5 to 6 cubic centimeters as compared to 30 cubic centimeters. The device requires crushing of the ampule within the container. Also, the gas is mixed with the liquid in the container rather than in the ampule, thereby lowering the concentration of the radioactive gas in the liquid and increasing the possibility of contamination. In another prior art apparatus which has been in use for several years, the larger portion of an ampule is enclosed in plaster, a syringe cap is attached to the ampule neck by a rubber tube, a syringe is coupled to the interior of the rubber tube by a plastic line and a small needle through the syringe cap, and a larger needle with a valve at the outer end is inserted through the syringe cap into the ampule neck to break the ampule seal. This prior art device also has disadvantages. The ampule neck often broke at the time the seal was broken or during subsequent use and there was considerable gas leakage. The unit was akward to assemble and handle, and time was required to initially seal the ampule in plaster. Accordingly, it is an object of the present invention to provide a new and improved apparatus for mixing a gas and a liquid and for dispensing the resultant solution. A particular object is to provide such an apparatus which is especially well suited for handling small volumes, typically 5 to 6 cubic centimeters and less. Another object is to provide such an apparatus wherein the ampule is fully enclosed and protected in a housing and maintained intact, with the liquid being introduced into the ampule for mixing with the gas. An additional object is to provide such an apparatus incorporating a collar for clamping the ampule in place and a cap for sealing engagement with the ampule, with flow paths for gas and liquid within the housing and cap. Other objects, advantages, features and results will more fully appear in the course of the following description. SUMMARY OF THE INVENTION An apparatus for dispensing a gas contained in a sealed ampule by dissolving the gas in a liquid and withdrawing the resultant solution in quantities as desired. The apparatus includes a housing with a cavity for receiving the ampule with the housing having a cap or the like for retaining the ampule, a seat for engagement with the ampule output line, and flow paths from the exterior of the housing to the seat. The apparatus also includes means for connecting a syringe to one of the flow paths. A hollow needle is positioned in the other flow path with an end entering the ampule output line for breaking the seal within the ampule with the resultant inflow of liquid from the syringe into the ampule and dissolving of the gas into the liquid. The gas-liquid solution may then be withdrawn through the needle, with needle flow controlled by a valve carried on the needle. A split collar is positioned about the ampule outlet line for inserting and removing the ampule, and for fixing the ampule in the housing, with the main body of the ampule spaced from the housing and with the mouth of the ampule outlet line engaging the cap in sealing relation.
	abstract	A nuclear reactor cooling system with passive cooling capabilities operable during a loss-of-coolant accident (LOCA) without available electric power. The system includes a reactor vessel with nuclear fuel core located in a reactor well. An in-containment water storage tank is fluidly coupled to the reactor well and holds an inventory of cooling water. During a LOCA event, the tank floods the reactor well with water. Eventually, the water heated by decay heat from the reactor vaporizes producing steam. The steam flows to an in-containment heat exchanger and condenses. The condensate is returned to the reactor well in a closed flow loop system in which flow may circulate solely via gravity from changes in phase and density of the water. In one embodiment, the heat exchanger may be an array of heat dissipater ducts mounted on the wall of the inner containment vessel surrounded by a heat sink.
	claims	1. A water-air combined passive feed water cooling apparatus for a nuclear reactor containment building comprising:a water-cooled heat exchanger connected to the inside of the containment building, the water-cooled heat exchanger configured to cool down main steam of a steam generator;a cooling tank located outside the containment building, the cooling tank comprising the water-cooled heat exchanger therein and configured to store cooling water at a surface level and condense the main steam generated by the steam generator;an evaporative steam pipe connected to the cooling tank and having a bottom end positioned above the surface level of the cooling water, the evaporative steam pipe configured to receive steam of the cooling water generated by the water-cooled heat exchanger in the cooling tank;an air-cooled heat exchanger positioned above the cooling tank and connected to the evaporative steam pipe and configured to cool and condense the steam flowing into the evaporative steam pipe, the air-cooled heat exchanger having an opening portion at a top end of the air-cooled heat exchanger configured to emit non-condensable gas outside of the containment building;a condensed water collecting pipe configured to refill the cooling tank with the steam condensed by the air-cooled heat exchanger, wherein the condensed water collecting pipe has a bottom end positioned below the surface level of the cooling water; andan air induction duct extending vertically along an outside surface of the containment building above the cooling tank, the duct configured to induce an air flow around the air-cooled heat exchanger positioned within the duct. 2. The apparatus of claim 1, wherein the cooling tank is a pressure vessel. 3. The apparatus of claim 1, wherein the air-cooled heat exchanger comprises a radiator receiving steam of cooling water generated in the cooling tank through the evaporative steam pipe and emitting heat outwards. 4. The apparatus of claim 3, wherein the radiator is formed of at least two vertical pipes and at least two horizontal pipes intersecting with one another. 5. The apparatus of claim 3, wherein the radiator comprises at least one pipe having an incline to allow condensed steam to flow toward the condensed water collecting pipe. 6. The apparatus of claim 5, wherein the condensed steam is allowed to flow into the vertical pipes extended from the condensed water collecting pipe due to the incline. 7. The apparatus of claim 6, wherein the condensed water collecting pipe, to prevent a backflow toward the condensed water collecting pipe, has an outlet located below an uppermost location of the water-cooled heat exchanger. 8. The apparatus of claim 1, wherein the air-cooled heat exchanger comprises at least a horizontal heat exchange condensing tube. 9. The apparatus of claim 8, wherein the horizontal heat exchange condensing tube is formed of a heat exchange tube comprising a cooling fin to increase heat emission efficiency. 10. The apparatus of claim 1, wherein the opening portion is a pipe. 11. The apparatus of claim 3, wherein the opening portion is a pipe connected to a top pipe of the radiator. 12. A water-air combined passive feed water cooling system for a nuclear reactor containment building formed of a plurality of passive feed water cooling systems each comprising:a water-cooled heat exchanger located outside the containment building and connected to the inside of the containment building and configured to cool down main steam of a steam generator;a cooling tank located outside the containment building, the cooling tank comprising the water-cooled heat exchanger therein and configured to store cooling water at a surface level and condense the main steam generated by the steam generator;an evaporative steam pipe connected to the cooling tank and having a bottom end positioned above the surface level of the cooling water, the evaporative steam pipe configured to receive steam of the cooling water generated by the water-cooled heat exchanger in the cooling tank;an air-cooled heat exchanger positioned above the cooling tank connected to the evaporative steam pipe and configured to cool and condense the steam flowing into the evaporative steam pipe, the air-cooled heat exchanger having an opening portion at a top end of the air-cooled heat exchanger configured to emit non-condensable gas outside of the containment building;a condensed water collecting pipe configured to refill the cooling tank with the steam condensed by the air-cooled heat exchanger, wherein the condensed water collecting pipe has a bottom end positioned below the surface level of the cooling water;an air induction duct formed of a hollow pipe comprising one air inlet and one air outlet, the duct extending vertically along an outside surface of the containment building above the cooling tank and configured to induce an air flow around the air-cooled heat exchanger positioned within the duct; anda cooling air blower installed inside the air induction duct and configured to forcibly generate the air flow,wherein each quadrant of the containment building is provided with one of the plurality of the passive feed water cooling systems. 13. The system of claim 12, wherein the cooling air blower is located on a top end inside the air induction duct. 14. The system of claim 12, wherein the cooling air blower is located on a bottom end inside the air induction duct. 15. The system of claim 12, wherein the cooling air blower is located in a middle inside the air induction duct. 16. The system of claim 12, wherein the cooling air blower is selectively formed in at least two selected from the top end, the bottom end, and the middle inside the air induction duct. 17. The system of claim 12, wherein the air induction duct is extended in a direction horizontal to a ground surface. 18. The system of claim 12, wherein the cooling air blower comprises:an electric-powered fan generating an air flow; anda driving unit for driving the electric-powered fan. 19. The system of claim 18, wherein the electric-powered fan comprises at least three rotors, andwherein to naturally circulate the air when the driving unit does not operate, the electric-powered fan has a total projected cross-sectional area of the rotors less than about ⅓ of a cross-sectional area of the air induction duct. 20. The system of claim 18, wherein the driving unit is formed of a motor.
043022863	claims	1. An improved reactor vessel in-service inspection assembly having an inspection transducer positioning arm wherein the improvement comprises means for locating the positioning arm at a pre-established location within a hollow portion of the reactor vessel cavity wherein the locating means includes: means affixed to the positioning arm for generating and simultaneously, radially, directing acoustic signals around the circumference of the hollow portion of the vessel cavity and receiving the signals reflected off of the cavity walls and redirected to the location from which the signals were originally, radially directed, at a position within the hollow portion wherein the generating and receiving means comprises an acoustic transducer and reflector wherein the reflector is constructed to radially direct the acoustic signals generated by the transducer to the walls of the hollow portion of the reactor vessel cavity and redirect the acoustic energy reflected off the cavity walls back to the reflector to the transducer; means for monitoring the received signals as a function of time; and means for positioning the arm in response to the monitored difference in time of reception of the received signals, at the pre-established location within the hollow portion of the reactor vessel cavity. means for generating and simultaneously, radially directing acoustic signals around the circumference of the cavity and receiving the signals reflected off of the cavity walls and redirected to the location from which the signals were originally, radially directed, at a position within the cavity wherein the generating and receiving means comprises an acoustic transducer and reflector wherein the reflector is constructed to radially direct the acoustic signals generated by the transducer to the walls of the cavity and redirect the acoustic energy reflected of the cavity walls back to the reflector to the transducer; means for monitoring the received signals as a function of time; and means for positioning the generating and receiving means in response to the monitored difference in time of reception of the received signals, at the pre-established location within the cavity. 2. The reactor vessel in-service inspection assembly of claim 1 wherein the generating and receiving means comprises an acoustic transducer having a cylindrical acoustic generating face. 3. The reactor vessel in-service inspection assembly of claim 2 wherein the axis of revolution of the cylindrical generating face is coincident with the axis of the positioning arm. 4. The reactor vessel in-service inspection assembly of claim 1 wherein the reflector is shaped as a cone. 5. The reactor vessel in-service inspection assembly of claim 1 wherein the reflector is shaped as a three-sided pyramid. 6. The reactor vessel in-service inspection assembly of claim 1 wherein the reflector is shaped as a four-sided pyramid. 7. The reactor vessel in-service inspection assembly of claim 1 wherein the reflector is positioned on the axis of the positioning arm. 8. The reactor vessel in-service inspection assembly of claim 6 wherein the means for locating the arm moves the arm in a forward and reverse direction along lines parallel to both the X and Y axes. 9. The reactor vessel in-service inspection assembly of claim 1 or 8 wherein the means for locating the arm positions the arm at the pre-established location automatically in response to the monitored difference in time of reception of the received signals. 10. The reactor vessel in-service inspection assembly of claim 1 wherein the pre-established location is substantially at the center of the hollow portion of the reactor vessel cavity. 11. The reactor vessel in-service inspection assembly of claim 10 wherein the means for locating the arm moves the arm in a direction to minimize the time difference between received signals. 12. Apparatus for identifying a pre-established location within a hollow cavity comprising: 13. The apparatus of claim 12 wherein the reflector is constructed as a pyramid. 14. The apparatus of claim 13 wherein the reflector is a three-sided pyramid. 15. The apparatus of claim 13 wherein the reflector is a four-sided pyramid. 16. The apparatus of claim 15 wherein the means for positioning the generating and receiving means moves the generating and receiving means in a forward and reverse direction along lines parallel to both the X and Y axes. 17. The apparatus of claim 12 or 16 wherein the means for positioning the generating and receiving means positions the generating and receiving means at the pre-established location automatically in response to the monitored difference in time of reception of the received signals. 18. The apparatus of claim 12 wherein the pre-established location is substantially at the center of the cavity. 19. The apparatus of claim 18 wherein the means for positioning the generating and receiving means moves the generating and receiving means in a direction to minimize the time difference between received signals.
	summary
	description	Referring to the drawings for a better understanding of the function and structure of the invention, FIG. 1 shows an exploded view of the primary components of one embodiment of the infrared scene projector 10. A primary housing or case 11 acts as a protective enclosure and support for the primary electronics assembly 12 which is mated to an infrared array assembly 13. As shown in the Figure, screws affix the combined electronics assembly 12 and infrared array assembly 13 into housing 11 along an outer circumferential margin of the array assembly board 13 seated on an inner circumferential flange of the housing 11. A lens mounting plate 14 is aligned onto dowels extending forward from the primary housing 11 with additional screws securing the plate 14 against the housing as shown, enclosing the electronics assembly 12 and the array assembly 13 within the housing 11. Aperture 15 is located at the center of the lens mounting plate 14 to allow passage of the infrared emissions emanating from the seated infrared emitter array. The aperture 15 also serves as a receptor for lens assembly 16 which includes a threaded or smooth extension from its body for mounting onto the plate 14. As shown in FIG. 2, the to assembled scene projector 10 occupies a rather compact and unobtrusive shape, having a typical thickness of approximately 3 inches and a total length measured from the foremost point on the lens assembly to the rearmost portion of the housing of only about 8 inches. FIGS. 3a-b shows another embodiment of the scene projector 10 in which the enclosed electronics (12, 13) and housing components (11) are outfitted with a tower and fold mirror in lieu of a refractive lens assembly 14, 16, and placed adjacent to a collimator assembly. In certain applications it is advantageous that the scene-projector 10 be positioned in front of a large aperture enclosed within a weather resistant housing. In such applications, a fold mirror and collimator assembly allows for testing structures to be positioned within an aircraft or vehicle for the purposes of mission readiness and target acquisition refinements. As shown in FIG. 3a, an angled collimator mounting plate 17 supports a tower assembly 18 of multiple leg extensions 18a-h, and a fold mirror 19 is held by a suitable bracket 21 that allows for positioning of the mirror in an angle for reflecting a projected infrared image into an adjacent collimator. As shown in FIG. 3b, a typical collimator assembly 22 might include, two curved mirrors, one convex and one concave, both suitably shaped to focus a projected infrared image onto a proximally located infrared sensor objective. As will be understood in the industry, various types of collimator lens and shapes can be manufactured to address various types of targeting sensor sizes and other physical configurations of infrared sensor electronics. It will also be noticed that the collimator mounting plate 17 is angled at approximately 12.32xc2x0. However offset angles of various ranges are anticipated to address various types of collimator and fold mirror configurations and sizes. The figure shows a Ritchey-Chretien type of collimator, although various configurations and types will be utilized. In the shown example configuration, both mirror surfaces are off-axis aspheric sections with an 8-inch clear aperture having a 36-inch focal length. An interface plate engages alignment pins to allow for positioning of the infrared array at the tilted image plane of the collimator. FIGS. 4-9 show different elevational views of the refractive lens embodiment of the infrared projector 10. FIG. 8 additionally shows an access plate 26 that allows for access to the internal wiring harness (not shown) connecting the internal electronics assembly boards to the projector""s external port connectors. FIG. 9 shows external connectors, namely, a standard RS-232 9 pin serial port connector 28, a 10 pin recessed pin grid connector 29 which provides power and grounding for the projector, and a video input jack 30 that provides a port for receiving RS-170 video signals. FIG. 10 shows a perspective cut away view of the assembled scene projector showing relative positions of various critical components for the scene projector 10. The projector housing 11 holds the passive heat sink 32 via screws protruding through each heat sink cooling fin, allowing for isolation of the heat conducted away from the array emitter 51 from the primary electronics assembly 12. Bracket 31 holding electronic assemblies 34 and 36 (not visible) is secured into array emitter CCA 13 with 4 screws extending through the emitter CCA 13 and into the bracket 31. The assemblies 34 and 36 are secured to the bracket with flat pan screws. A TEC (Thermoelectric Cooler) device 33 is positioned between heat sink 32 and infrared array assembly board 13 and affixed to a flat portion of the heat sink 32 with thermally conducting pads and to the bottom of the actual array emitter. As can be seen in the figure, connectors are suitably positioned to engage each of the boards electronic internal connectors and provide for electrical communications between the boards over prescribed lines. A rectangular aperture in the printed circuit board holding the infrared array emitter 51 allows the TEC cooling device to be mounted directly onto the ventral surface of the ceramic semiconductor package of the emitter array 51, which is affixed thereto with suitable heat conducting pads. The heat sink 32 is also adhesively affixed to the heat transference side of the TEC to promote transfer heat emissions generated by the infrared emitter away from the emitter and against the inner surface of the housing 11 Heat is therefore conducted away from the emitter 51 and the primary electronic assembly 12 through the housing 11 top and bottom surfaces. As those skilled in the art will appreciate, establishing proper controls for background infrared emissions is an important component in proper infrared scene generation. The disclosed arrangement of the TEC cooler and suitably sized heat sink allows for sufficient dissipation of heat energy from the infrared array emitter such that, under proper electrical control as will be discussed, background energy emissions are controlled. Thermoelectric cooling devices such as the TEC cooler disclosed herein 33 are primarily electric heat pumps used for the removal of heat from one side of a TEC device to another side. Each side is sometimes referred to as the hot and cold sides of the TEC device. In the disclosed embodiment, the cold or cooling side of the TEC device is affixed to the rear or underside portion of the infrared emitter array and the hot or heat dissipation side is located on a side opposite from the cooling side and against a forward-most, flat portion of the passive heat sink 32. A suitable TEC cooler utilized in the disclosed design is a FRIGICHIP FC series type available from Melcor, Inc. The passive heat sink 32 is made from suitably conductive metal alloys such as conductive aluminum which satisfactorily dissipates heat transferred by the TEC cooler. As infrared emitter technology advances, it is anticipated that a passive heat sink design may, in and of itself, provide sufficient cooling, thereby obviating the need for thermoelectric cooling. The infrared array emitter 51 can be comprised of any industry standard matrix addressable infrared emitter (albeit with some electronics reconfiguration for each model). The current preferred embodiment utilizes analog generated input signals to address image pixel intensity requirements, although the inventors contemplate that a purely digital based infrared emitter will be available in the future. A suitable emitter for the current design is offered by Honeywell, Inc. under the brand name Brite 128-512 Infrared Emitters. These types of emitters directly radiate energy from underlying pixel addressable points on a silicon wafer. A matrix of 128xc3x97128 pixels form a matrix of gray body emitters with an infrared radiance that varies as a function of an applied voltage. These types of Honeywell emitters generate infrared radiance at individual pixel locations by passing current through a thin film resistor suspended above a polarized substrate. The current through the emitter resistor is a function of the gate voltage stored in the hold capacitor connected to the gate allowing for very low power operation by which pixel emissions vary within a wide dynamic range. Moreover, these types of infrared emitters have high vacuum integrity because the pixels are fabricated using low vapor pressure materials, such as nitride and oxides, with bulk properties having melting temperatures in the 1500-2000 k temperature range. Hence, each pixel emits a high contrast infrared point with very high thermal stability that performs over a range of atmospheric pressures, such as may be experienced in airborne applications. As partially shown in FIG. 10, connectors on the infrared emitter array assembly board 13 provide for electrical signal connections between various electronic assembly boards, and wiring harness 38 provides electrical signal connectivity from external connectors 28-30 to the various boards. Referring now to FIG. 11, the system consists of four functional components: (1) a DSP circuit card assembly (xe2x80x9cCCAxe2x80x9d) 36; (2) a scene generator circuit card assembly 34; (3) an infrared emitter array CCA 13; and, (4) an optical assembly 53. The scene generator CCA 34 provides power 41 to other functional elements in the system. A RS-232 port 43 provides serial information input into the DSP CCA 36 to receive computer commands from a graphical user interface running on a separate personal computer (not shown) and also provides for reprogramming of internal firmware and downloading of DSP operational commands. A connector 30 (see FIG. 9) allows for RS-170 signals 42 to be received by the scene generator CCA 34, which are then separated into digital video data 64 and video synchronization information 67. A digital signal processor or xe2x80x9cDSPxe2x80x9d integrated semiconductor 46 provides video data 47 for conversion through a digital analog converter 48 into analog signals 49 received by infrared emitter array 51 for infrared image generation 52. The DSP 46 provides direct video feed from the RS-170 signal into the digital analog converter 48 or, alternatively, the DSP can generate its own infrared images through algorithm computations stored in FLASH memory and in association with logic stored in firmware FPGA 56 (Field Programmable Gate Array). Also, an RS-232 source 43 can provide a bit mapped scene image to be held in high speed memory on the DSP CCA 36 such that it can then be transferred directly to the infrared image emitter array 51. A TEC cooler 58 provides cooling to the array emitter 51 as already discussed and thermistor 99 outputs a feedback signal to analog digital converter 54 that is read by DSP integrated circuit 46. In response, the DSP outputs commands through the FPGA interface 56 to control the TEC cooling rate through TEC control signals 57. FIG. 12 shows more specific details regarding the function and operation of individual components located on the scene generator CCA 34. A buffer 71 normalizes voltages compatible with the CCA""s voltage levels from the inputted RS-170 signal 42, and a video sink separator 72 separates the video synchronization signal from the RS-170 buffered signal to establish a timing indicator signal for use by pixel clock generator 73. The pixel clock generator includes logic to send appropriate clock signals via a pixel clock input line to a 12-bit analog to digital converter 74. xe2x80x9cBackporchxe2x80x9d signal 76 from separator 72 is used to offset-normalize the video information 78 via DC restorer 77 to allow for proper digital conversion. Video information 78 is then converted from analog to digital via 12-bit video analog to digital converter 74 and saved in a 256Kxc3x9718 FIFO 79 memory for interim storage of individual interlaced signal fields. The pixel clock generator 73 generates a field storage signal at approximately a 60 Hz rate so that interlaced fields can be combined into a non-interlaced frame by the DSP CCA 36. The pixel clock generator 73 utilizes external phase loop logic 81 in conjunction with the pixel clock generator logic 73 contained within the FPGA 56 to produce the appropriate clock signals. The combination of these video and logic elements 82 allows for the continual conversion of RS-170 source signals, either in color or black and white, to be continually digitized and processed by the DSP CCA 36. As will be explained in more detail, the DSP CCA 36 has available one field of video stored in the FIFO 79 for processing in accordance with prior downloaded instructions from a separate user software package or prior loaded internal processing instructions. Due to the speed of the DSP processor, processing of individual video fields stored in the FIFO 79 occurs well prior to the availability of the next interlaced video field presented by the external RS-170 signal source, thereby permitting the combining of interlaced fields into a non-interlaced image and the timely transference of the image to the emitter array 51. FIFO interface 83 provides a signal to the DSP CCA 36 signaling whether or not the FIFO 79 contains a complete field and is available for transference to the DSP CCA. FIFO interface 83 also sends control signals to the FIFO 79 instructing the FIFO to load digital video from the 12-bit video analog-to-digital converter 74. Core interface logic 84 provides interface logic to accept control signals from the DSP CCA 36 via multiplexed buses 86-88. Bus lines 86-88 are physically identical on the scene generator CCA 34 and on the DSP CCA 36. However, the digital signal processor 46 utilizes chip selects to multiplex values on the bus 86-88 to present data and receive data from appropriate integrated circuits such as, for example, the FIFO video frame information 79 and transference of core logic instructions to core interface 84 on FPGA 56. Bus 86-88 is utilized to transfer 32 bit data information to data buffer 91 and matrix addressing array buffer 92. FPGA 56 also includes digital to analog conversion interface logic 95 that provides control signals to the 32 bit digital analog converter 93. Those skilled in the art will understand, therefore, that the 20 bit address bus, the 32 bit data bus, and the control bus 86-88 are a multiplex set of lines circumscribing paths on both the scene generator CCA 34 and the DSP CCA 36. By using a chip select function, the DSP CCA 36 can receive interlaced video field data from FIFO 79 and combine it with a second interlaced field to produce a non-interlaced display image frame for writing to the 32 16-bit DAC 93 in preparation for display. A 32-bit data buffer 91 is used for signal fan out to the 32 16-bit DACs 93. Pixel intensity information is retained in the 32 16-bit DAC 93 and presented to the infrared emitter array 51 via eight analog input lines 77. These analog input values are held and the DSP CCA 36 energizes the appropriate address lines. A TTL-to-CMOS buffer 92 is used to convert the DSP CCA 36 3.3V TTL logic levels to 5V CMOS logic required by the infrared emitter array 51. Additional address strobes are replicated until all of the pixels in the array 51 have been loaded with analog intensity information. Although a 128xc3x97128 pixel configuration is shown, those skilled in the art will understand that a scalable addressing scheme may be utilized to address larger arrays such as a 256xc3x97256 or 512xc3x97512 pixel arrays. The TEC cooler 58 is mounted to the underside of the array 51 to provide cooling as previously discussed. A TEC cooler drive 96 receives constant frequency signal from a pulse width modulator 97 which varies its duty cycle in accordance with modulation logic in the FPGA 56 to control the rate of cooling by the TEC cooler 58, and which in turn is controlled by command signals provided by the DSP CCA 36 through the core interface logic 84. A thermistor measurement circuit 98 receives sensory information from a temperature sensitive thermistor 99 which is then converted into digital information through analog to digital converter 54 on the DSP CCA 36. Digital signal processor 46 then interprets digital values of the thermistor measurement circuit 98 and sends appropriate control signals to the FPGA 56 to control the modulator 97. Hence, through this feedback communication strategy, the TEC cooler 58 can be controlled with a high level of granularity that allows for control of the background infrared emissions of the infrared emitter array 51, thereby enhancing infrared image generation integrity. Module interface 101 comprises an external connector 29 and wiring harness (not shown) providing appropriate +5V, +12V, and xe2x88x9212V input voltages and returns. The module interface 101 also comprises the RS-232 pin connector 28 that allows for direct connection into the DSP CCA 36. In order to minimize feedback noise potential, a separate pixel power line 102 provides +5V direct input and return into the infrared emitter array 51. If common +5V lines were utilized to power the infrared emitter array 51, a possibility of switching noise generated by the DSP CCA 36 could be propagated through power lines into the array CCA 13 and provide undesirable interference with the infrared emitter""s operation. Referring now to FIG. 13 for a better understanding of the operation of the DSP CCA 36, a TMS320C6211 digital signal processor 46 provides the primary processing functions of the DSP CCA 36. Texas Instruments is the manufacturer of the TMS320 series of digital processors two of which, the TMS320C62211 (non-floating point) and the TMS320C6711 (floating point) digital signal processors, may be utilized in the instant described design. However, those skilled in the art will understand that any type of processor having the capability of executing instructions and algorithmic processes at sufficient speeds may be utilized. For example, the inventors anticipate that a general purpose microprocessor such as Intel""s 386 16-bit line of microprocessors could be utilized in place of herein described digital signal processor. The DSP CCA 36 is a fairly self-contained CCA and may be utilized in various other systems. The actual DSP operates at 150 MHz and uses an internal 100 MHz system bus, and the speed of the DSP CCA 36 is approximately 1200 MIPS or 600 MFLOPS. The DSP CCA includes 256Kxc3x9716 bit FLASH memory 111 and 64Kxc3x9732 bit asynchronous static memory (ASRAM) 112 for DSP program store and image calculations. The CCA 36 also utilizes several high speed and low speed (100 MSPS, 100 KSPS) analog to digital converters (not shown) controlled by a XLINX FPGA through control lines 114. The procedures by which the TMS32ODSP, or an alternative microprocessor, are programmed will not be discussed in as much as programming kits and code compilers are readily available and well understood in the industry. For example, Texas Instruments offers a software developer""s kit called a xe2x80x9cCode Composer Studio Development Environmentxe2x80x9d for the TMS320 line of DSPs and Intel sells similar developer kits for its line of microprocessors allowing for DSP code assembly and compilation. The DSP 46 communicates to the scene generator CCA 34 via external memory interface EMIF 121 and via connectors 116 and 117. Other communication links such as the RS-232 link 43, a controlled area network link (not shown), and a host port interface (HPI) 130 can also be invoked for other types of communication and controls. Currently the EMIF is a little endian format, but other suitable formats may be utilized. Flash memory 111 includes FPGA reprogramming code 119 to allow for reprogramming of the XLINX FPGA 113 and includes a protective portion of flash memory for boot up code 125. The DSP 46 and the XLINX FPGA 113 communicate with the scene generator CCA 34 through the external memory interface 121. The DSP 46 utilizes four external address spaces in its external memory interface 121, namely; CE0, CE1, CE2, and CE3. CE0 is used to access static RAM 112 and CE1 is used to access FLASH memory 111, registers on a separate PLD (not shown), and registers on the XLINX FPGA 113. The XLINX FPGA 113 decodes each of these address spaces into four sub address spaces to allow a total of eight addressable spaces. Therefore, the XLINX FPGA may utilize one of its sub-address enables using the top two address bits (ADR21 and ADR20) from which chip enables CE2 or CE3 may be activated by the DSP 46 via the EMIF 121. The scene projector CCA 34 generally utilizes 5 of the 8 sub addresses to decode logic signals. The XLINX FPGA 113 includes all the necessary logic to decode and control various peripherals on the DSP CCA 36. This includes the Analog to Digital Converter (ADC) 54 for receiving thermistor measurement signals 98, DSP external interrupt control registers, such as interrupt pole, mask, and status registers, and an optional fast ADC, other optional fast and slow Analog to Digital Converters (DAC), LED control registers, clock control registers, and FPGA configuration status registers. Communications between the DSP CCA 36 and the scene generator CCA 34 occur through CE decodes over the address bus, the data bus of the EMIF, and the read/write control signals of the EMIF bus. The CE lines (see Figure) decode whether the EMIF bus lines are being utilized for communication between the DSP 46 and the scene generator FPGA 56, the DSP and the scene generator CCA digital analog converters, or the FIFO 79. Transceivers 122 and 123 insure error free communications across connectors 116 and 117 between the DSP CCA 36 and the scene generator CCA 34. Also, a separate programmable logic (PLD) device on the DSP CCA (not shown) controls the FLASH memory 111, sets the timing input for and enables reprogramming of the XLINX FPGA 113, contains XLINX FPGA 113 read back signals, and generates a 10 MHz clock for the use of an optional controlled area network controller. FIG. 14 shows an optical element configuration suitable for the herein described scene projector. Various types of optical assemblies and optical elements may be utilized to project an image emitted by the infrared emitter 51 onto various objectives. The shown optical assembly is optimized to project an image into a selected FLIR objective lens. It will be understood that varying optical assemblies could utilize threaded or bayonet type mounts to facilitate the interchangeability of lens on mounting plate 14 to allow for rapid reconfiguration of the infrared projector 10 to suit different situations. Inasmuch as optical assemblies and techniques for combining various optical elements to produce suitable focal lengths and fields of view are well known and understood in the industry, a detailed description of individual optical elements will not be provided. Nonetheless, an example configuration is shown in FIG. 14 which has been used by the inventors and is suitable for the herein described types of applications. As shown, individual pixel elements of the infrared emitter array 51 emanate from plane position 131 and are refracted by zinc selenide optical element 132. Element 132 has shaped properties pursuant to the values shown and is suitable for infrared refraction. Infrared image rays strike a second germanium optical element 133 and are again refracted to project an infrared image into a test article objective. Element 133 has optical properties as shown in the Figure. A typical distance of the optical element 132 and infrared source 131 is 16.4562 mm and the distance between Element 132 and Element 133 is 79.0 mm. In operation, the scene projector 10 can produce infrared images through three primary methods: (1) it can project a received RS-170 video signal which is refreshed at television video rates; (2) it can project a preloaded bit-map image received via the RS-232 communications link; or (3) it can construct synthetic images from parameters received from a separate user interface running on a serially connected personal computer or other computing device. Preloaded images, either through parameter description or as a bit-mapped image, can also be saved in memory (111 or 112) and projected on demand. In fact, a demonstration program using stored images or a preloaded test program can be created by storing such images or parameters and accessing them through an iterative display loop program. Creation of synthetic objects are accomplished by transferring inputs from an operator via a host interface to the scene projector 10, and executing algorithms stored in memory using transferred variable values to create images. A separate application program running on a personal computer allows a user to send command functions to the scene projector instructing it to, for example, be ready to receive a bit mapped image for display, prepare for firmware programming, start displaying RS-170 images, begin receiving object descriptor information to calculate and display synthetic image objects, etc. Selected functions are communicated to the DSP in a binary string of digits as a packet in a form as shown in Table 1: In the situation in which a command function calling for an object to be synthesized and displayed by the scene projector is transferred to the DSP, the data argument would consist of image creation parameters called xe2x80x9cobject descriptors.xe2x80x9d The PC application program includes a graphical user interface or xe2x80x9cGUIxe2x80x9d that allows for easy input of the object descriptors via predefined fields. These defined object descriptors are then grouped into the argument of the command function packet as part of the Data Field and transferred to the DSP CCA 36 via the serial RS-232 connection. The format and parameters of the object descriptor data portion is as shown in Table 2 below. The inventors envision a multitude of types and quantities of description elements, but 13 pre-defined parameters seem to satisfactorily describe most synthetic images. Since the type and operation of a graphical user interface is not essential for a complete understanding of the operation of the scene projector 10, and since combining a list of input object parameters into a binary data packet and transferring it to the memory of a computing device is well understood in the industry and may be accomplished in a variety of ways, further description of such interfaces will not be described. The essential capability of the remote user interface is that it be able to transfer binary files and bit mapped images via the RS-232 link, and that the creation of the object descriptors be created and transferred into memory elements 111 or 112. Object descriptors shown in Table 2 below are satisfactory for most synthetic images: Upon transmission of a command function packet calling for the creation of a defined image, the DSP 46 uses the received descriptors to set the initial conditions of the image and to set a rate timer that regulates the motion of the object, if any. The DSP then calculates the location of the object origin in terms of two dimensional Cartesian coordinates. After calculating the sweep position and orbit angle from the sweep rate and orbit angular rates respectively, the origin is computed utilizing the specified sweep position, sweep range, orbit angle, and orbit radius. Once the origin of the object is determined, the object is drawn in static memory 112 as a matrix representing individual pixel elements of the array 51. Various predefined objects are preprogrammed into the DSP""s memory 112 for execution upon receiving a recognized object type in the descriptor data (see parameter 9). The selected object type at the required size and specified delta temperature is then drawn using a combination of three basic drawing functions (not to be confused with operation command functions). The primary drawing functions and their associated arguments are a xe2x80x9cplotlinexe2x80x9d (x0,y0,x1,y1, width), a xe2x80x9cplot circlexe2x80x9d (radius), and a xe2x80x9cfillxe2x80x9d (color). Each object is drawn using a combination of these primary drawing functions calculated by the DSP in association with other user supplied inputs from the scene projector""s GUI. Each drawing function has an initial configuration and is scaled using the descriptor parameters to form the selected object. For example, a bar object might be invoked, a 4-bar object, a circle object, a triangle object, or an alignment object. Solid objects such as the triangle and circle are filled with a color that is based on a user inputted temperature differential. If rotation of an object is required then the rotation angle and rotation angular rate are provided in the object descriptor data, which are used to compute the next required image in a movement sequence. This is done using a polar coordinate system in which the coordinates of key features of the object are first computed and then the object is drawn in the same manner as in the original object position. After an object image is drawn by the DSP and saved in memory, the object image information is written to the infrared array. In the event that the drawn image moves beyond the 128xc3x97128 array pixel matrix bounds, the portion of the object still within the boundary of the pixel matrix is displayed. This display strategy allows for the replacement or upgrading of the 128xc3x97128 array to larger arrays such as 256 or 512 pixels without rewriting the DSP instructions. Below, a description of how each primary object is drawn by the DSP is given in terms of the primary drawing functions. Obviously, as new objects are added over time, new functions may also be created to efficiently draw each object. The bar object is essentially a 7:1 aspect ratio bar constructed from the line and fill functions. Based on the user specified size described in terms of number of pixel elements, two horizontal lines are drawn and two connecting vertical lines having a length 7 times that of the bar width are inserted between their endpoints. The resulting rectangle is then filled with the fill level or xe2x80x9ccolorxe2x80x9d based on the received delta temperature parameter. The 4-bar object is created using a four 7:1 aspect ratio bar equally spaced by an equidistant amount. The perimeter of the resulting pattern is a square which is then centered in the array and each bar is then constructed as with the single bar method, but with lines added and a fill color drawn. The circle object uses the size specified by the operator in parameter No. 10 as the radius of a circle where the units of the radius is in number of pixel emitters of the array. The circle function is used to draw the circle object and then the fill function is applied. A triangle is created using three line functions and applying the fill function. The size of the triangle is specified by the user and determines the distance in emitters from the center of the array to the vertices of an isosceles triangle. Lastly, the alignment object is generated by combining four concentric circle functions and two orthogonal lines through the center point of the circles. The temperature level of the lines are based on the temperature delta selected by the operator. While the above four objects have been developed using the described three primary drawing line functions, it will be understood that additional drawing functions and objects will likely be developed depending upon the evolution of testing applications and additional testing refinements. While we have shown our invention in one form, it will be obvious to those skilled in the art that it is not so limited but is susceptible of various changes and modifications without departing from the spirit thereof.
	abstract	A collimator, which is adhesively bonded to a detector element array, is prevented from falling off from the radiation detection apparatus even in case that a failure of the adhesive joint occurs in the collimator. There is provided a radiation detection apparatus comprising: a detector element array in which a plurality of detector elements are arranged substantially in a fan-angle direction and in a cone-angle direction of a radiation; a collimator adhesively bonded to a side of the detector element array on which the radiation impinges, and having outer end surfaces on both sides in the slice direction tapered to align with a direction of emission from a radiation source; and a pair of blocks disposed to sandwich the collimator in the cone-angle direction, and having inner end surfaces on both sides in the cone-angle direction tapered to align with the direction of emission.
	claims	1. An apparatus comprising:a fastener operable to couple to a nuclear reactor module within a reactor bay, wherein the nuclear reactor module includes a reactor vessel and a reactor core positioned within the reactor vessel;a reactor bay interface panel positioned proximate the reactor bay;a cable operable to couple to each of the reactor bay interface panel and one or more sensors located within the nuclear reactor module such that the reactor bay interface panel is operable for accepting one or more signals from the one or more sensors within the nuclear reactor module, wherein the one or more signals are conveyed from the one or more sensors to the reactor bay interface panel by the cable, the cable further having a connector for removable attachment to the reactor bay interface panel; anda device operable to move at least the reactor vessel and the reactor core of the nuclear reactor module in a lateral direction, a crane interface panel being connected to the device, wherein the crane interface panel and the connector move with the device when the device moves the reactor vessel, and further wherein the cable and connector, when removed from the reactor bay interface panel, are attachable to the crane interface panel whereby the one or more signals are conveyed from the one or more sensors to the crane interface panel. 2. The apparatus of claim 1, wherein the device operable to move at least the reactor vessel and the reactor core of the nuclear reactor module in the lateral direction operates to move the reactor vessel of the nuclear reactor module in a first direction and a second direction approximately orthogonal to the first direction. 3. The apparatus of claim 1, further comprising a track for maintaining a minimum bend radius of at least one other cable that conveys the one or more signals. 4. The apparatus of claim 1, further comprising a controller for assisting and relocating the nuclear reactor module to a lower containment vessel removal fixture located in a servicing area. 5. The apparatus of claim 1, further comprising a conduit operable to hold a receiver that receives the one or more signals from the one or more sensors located within the nuclear reactor module. 6. An apparatus comprising:a crane having a fastener, the fastener being operable to couple to a nuclear reactor module, wherein the nuclear reactor module includes a reactor vessel and a reactor core positioned within the reactor vessel, the crane being operable to move the nuclear reactor module in a lateral direction with respect to a reactor bay;a reactor bay interface panel positioned proximate the reactor bay;a crane interface panel attached to the crane for movement together with the crane;a cable operable to couple to each of the reactor bay interface panel and one or more sensors located within the nuclear reactor module such that the reactor bay interface panel is operable to accept one or more signals from the one or more sensors within the nuclear reactor module, wherein the one or more signals are conveyed from the one or more sensors to the reactor bay interface panel by the cable, the cable further having a connector for removable attachment to the reactor bay interface panel, wherein the cable and the connector are detachable from the reactor bay interface panel and attachable to the crane interface panel such that when the connector is attached to the crane interface panel the crane interface panel is operable to accept one or more signals from the one or more sensors within the nuclear reactor module; andwherein the connector and the crane interface panel move together with the crane when the crane is operating to move the nuclear reactor module. 7. The apparatus of claim 6, further comprising a conduit operable to hold a receiver that receives the one or more signals from the interface panels and conveys the one or more signals to a receptacle. 8. An apparatus comprising:a crane having a fastener, the fastener being operable to couple to a nuclear reactor module within a reactor bay, wherein the nuclear reactor module includes a reactor vessel and a reactor core positioned within the reactor vessel, the crane being operable to move the nuclear reactor module in a lateral direction;a reactor bay interface panel positioned proximate the reactor bay;a cable having a connector at an end of the cable external to the nuclear reactor module, the cable operable to convey signals from one or more sensors located within the nuclear reactor module, the cable further being selectively attachable to and detachable from the reactor bay interface panel; anda crane interface panel attached to the crane for movement together with the crane, the crane interface panel being adapted for removable attachment of the connector of the cable, the crane interface panel being operable to accept the one or more signals from the one or more sensors within the nuclear reactor module when the cable is detached from the reactor bay interface panel and attached to the crane interface panel;wherein, when the cable is detached from the reactor bay interface panel and attached to the crane interface panel, the connector and the crane interface panel move together with the crane when the crane is operating to move the nuclear reactor module. 9. The apparatus of claim 8, wherein the crane interface panel further comprises a sensor receiver. 10. The apparatus of claim 9, further comprising an operator display coupled to the sensor receiver. 11. The apparatus of claim 10, further comprising a servicing area display coupled to the sensor receiver. 12. The apparatus of claim 8, wherein the crane is operable to move the reactor vessel of the nuclear reactor module in a first direction and a second direction approximately orthogonal to the first direction. 13. The apparatus of claim 8, further comprising a track for maintaining a minimum bend radius of at least one other cable that conveys the one or more signals. 14. The apparatus of claim 8, further comprising a controller for assisting and relocating the nuclear reactor module to a lower containment vessel removal fixture located in a servicing area. 15. The apparatus of claim 8, further comprising a conduit operable to hold a receiver that receives the one or more signals from the one or more sensors located within the nuclear reactor module.
051805260	summary	The present invention relates to the cleaning of solutions of alkylphosphates, and in particular to alkylphosphates dissolved in a hydrophobic organic solvent. Such solutions are used in solvent extraction processes involved in the production of uranium from uranium ore. During use, especially in the recovery of waste uranium from the main ore conversion process, both the alkylphosphates and the solvent gradually become increasingly degraded as a result of chemical changes due to radiolysis and attack by acids. In time the degradation products interfere with the solvent extraction process to such a degree that the solution has to be replaced and the discarded uranium-contaminated material disposed of at considerable cost. It has now been found that by first removing, by means of a suitable reagent, sufficient complexed nitric acid (and other complexed species of uranium and iron) from the impure alkylphosphate solution, and subsequently subjecting the said solution to an ion-exchange treatment, a solution can be produced which satisfies the requirements for re-usability. According to the present invention, there is provided a process for cleaning a degraded solution of an alkyl phosphate in a hydrophobic organic solvent the solution being degraded in the solvent extraction of uranium ore and containing complexed nitric acid and complexed species comprising uranium therein, the process comprising the steps of washing the said solution with aqueous sulphuric acid to remove the complexed nitric acid and the complexed species and contacting the washed solution with an ion exchange material. The invention is particularly directed at the treatment of solutions of trialkylphosphate in which the alkyl groups range from ethyl to octyl, especially butyl, and in particular n-butyl. The hydrophobic organic solvent for the trialkylphosphate is normally a hydrocarbon liquid, usually a mixture of hydrocarbons, for example obtained from the distillation of petroleum, 10 typically a kerosene boiling between 180.degree. C and 290.degree. C, of which odourless kerosene is frequently employed. The concentration of alkylphosphate in the hydrophobic organic solvent can vary widely and compositions can be treated in which the alkylphosphate is concentrated or very dilute. In general the alkyl phosphate will be present in the solution at a concentration of about 5 to 50% on a volume to volume basis. Typically, a solution for treatment after use in the production of nuclear grade uranium would comprise about 20-40% v/v of tributylphosphate (TBP) in odourless kerosene. Decommissioned alkylphosphate solutions in hydrocarbon liquid, that is, solutions which have become degraded in use to such an extent that they can no longer be used, can contain significant amounts of uranium and nitric acid mainly in an organically complexed form. The concentration of aqueous sulphuric acid used for washing the alkylphosphate solution can vary widely and generally falls within the range 30% v/v to 0.1% v/v H.sub.2 SO.sub.4 preferably 5% v/v to 0.1% v/v H A typical concentration used is about 4% v/v H.sub.2 SO.sub.4 in water. The washing method may be any method suitable for efficient contact between the organic phase and the aqueous phase and which provides a contact time sufficient for efficient mass transfer. A counter-current flow system is preferred and appropriate means such as box mixer-settlers or pulsed columns may be employed to effect contact. The ratio of the volume of alkylphosphate solution to the volume of aqueous sulphuric acid during washing can vary widely, and is usually between 20 and 0.05 volumes of aqueous sulphuric acid to one volume of alkylphosphate solution. In general, a temperature of ambient or above during washing is favoured, and temperatures in the range 15.degree. C. to 60.degree. C., preferably 18.degree. C. to 25.degree. C., are suitable. The first step of the process of the invention, namely washing with aqueous sulphuric acid, is primarily of importance in the removal of organically complexed nitric acid and/or free nitric acid from the alkylphosphate solution. Removal of such contaminants facilitates the subsequent ion-exchange step in the process of the invention by preventing, it is believed, the adsorption of nitrate ions on to the ion exchange material which would lead to a disastrous loss of the ability of the ion exchange material to remove degradation products from the alkylphosphate solution. The washing step is also beneficial in removing uranium, wholly or partially, from the alkylphosphate solution. Apart from avoiding a reduction in ion-exchange capacity, the ion-exchange material is not contaminated by radioactive material, thereby facilitating safe disposal of the material used to regenerate the ion exchange resin. The ion-exchange materials used in the second step of the process according to the invention are preferably chosen from anionic ion exchange materials, inorganic or organic, for example resins of the chemical type or types designated as styrene divinyl benzene copolymers. Weakly basic anionic resins are preferred. Mixed anionic/cationic resins are also useful, for example Duolite MB5113, available from Diamond Shamrock (Polymers) Ltd. The ion exchange resin may also advantageously be of the macroreticular type. Examples of preferred ion-exchange resins for use in the process of the invention include the strongly basic anionic resin designated Amberlyst A26 and particularly the weakly basic anionic resin Amberlyst A21, both available from the Rohm & Haas Co. Amberlyst A21 is a macroreticular resin having an amino functional group and an average pore diameter of 900-1300 Angstroms whereas Amberlyst A26, also a macroreticular resin, has a quaternary ammonium functional group and a pore-diameter of 400-700 Angstroms. An ion-exchange resin of some interest is the anionic Duolite A116 available from Diamond Shamrock (Polymers) Ltd). In use, the ion-exchange resins are normally in the hydroxyl ionic forms. The ion-exchange step of the process of the invention can be carried out by any convenient method known in the art. Contact between the washed solution and the ion-exchange resin is preferably carried out in a packed column of the ion exchange resin. The operation of the ion-exchange column is preferably carried out on a continuous basis until regeneration of the resin becomes necessary. It is desirable to filter the washed solution before it enters the column so as to avoid fouling of the resin with any solid particles present which could reduce its efficiency and effective life. It is important to ensure that sufficient contact time between the washed solution and the ion-exchange resin is provided in order to ensure an adequate degree of purification of the alkylphosphate solution being treated. In general, the longer the contact time the more efficient is the ion-exchange process. It is convenient to express contact time in a packed column in terms of the number of "bed-volumes" passed through the column per hour, usually abbreviated to Bv/hr. By way of example contact times of between 0.1 Bv/hr and 20 Bv/hr can be used, but a contact time of 0.1-1.0 Bv/hr is preferred. The progress of cleaning the solution of alkyl phosphate can conveniently be followed throughout the process of the invention by measuring the Retained Uranium (RU) value of the solution expressed as micrograms of uranium per milliliter (.mu.g U/ml) of solution. This value is most readily determined by an empirical method in which a sample of the solution is saturated with uranium by the addition of uranyl nitrate, extracted five times with dilute (0.06% w/v) nitric acid and the amount of uranium remaining measured by a standard technique. Although not essential, it may be useful in certain cases to wash the alkylphosphate solution with a weak alkali, for example aqueous sodium carbonate, before it is subjected to the first step of washing with aqueous sulphuric acid in the process of the invention. After use, the ion exchange resin may be regenerated by any suitable method known in the art. We prefer to use aqueous sodium hydroxide as regenerant, usually at a concentration of 4% to 10% W/V. The amount of regenerant is usually between 100% and 500% of the theoretical capacity of the ion exchange column.
052788822	summary	BACKGROUND OF THE INVENTION This invention relates to alloys for use in light water nuclear reactor (LWR) core structural components and fuel cladding. More particularly, this invention relates to a zirconium alloy for such use which exhibits superior ductility, creep strength, and corrosion resistance after irradiation. Still more particularly, this invention relates to a zirconium alloy with improved creep strength, corrosion resistance, and low neutron absorption cross section by controlling its alloy composition to within particular ranges, and especially including oxygen in particularly high ranges, thus to assist in reducing hydrogen uptake of the proposed alloy. DESCRIPTION OF THE PRIOR ART Zirconium alloys are used in the fuel assembly structural components of nuclear reactors, such as in fuel rod cladding, guide or thimble tubes, grid strips, instrument tubes, and so forth because of their low neutron cross section, good corrosion resistance in high pressure/high temperature steam and water, good mechanical strength and fabricability. Zirconium alloys, particularly those commonly known as Zircaloy-2 and Zircaloy-4 have been used in light water reactor cores because of their relatively small capture cross section for thermal neutrons. The addition of 0.5 to 2.0 percent by weight niobium and up to 0.25 percent of a third alloying element to these zirconium alloys for purposes of corrosion resistance in the reactor core is suggested in U.S. Pat. No. 4,649,023 as part of a teaching of producing a microstructure of homogeneously dispersed fine precipitates of less than about 800 angstroms. The third alloying element is a constituent such as iron, chromium, molybdenum, vanadium, copper, nickel and tungsten. Pellet-clad interaction (PCI) resistance is sought in U.S. Pat. Nos. 4,675,153 and 4,664,831 by use of zirconium-based alloys including "zirconium-2.5 w/o niobium". The latter teaching also refers to "Zr-Nb alloys containing about 1.0 to 3.0 w/o Nb". In these patents, oxygen is present "below about 350 ppm of said alloy". U.S. Pat. No. 4,648,912 teaches improving high temperature corrosion resistance of an alpha zirconium alloy body by rapidly scanning the surface of the body with a laser beam. The alloy treated included zirconium-niobium alloys. Thus, it has been found by various investigators in the prior art literature that the addition of niobium to a zirconium alloy for use in light water reactors will reduce hydrogen uptake from waterside corrosion, stabilize alloying element and oxygen-irradiation defect complexes, and make the alloy more resistant to annealing of irradiation damage. It is also reported by investigators that niobium will enhance work hardenability of irradiated Zircaloy but that an addition of niobium above the 1 percent level will not result in further additional benefit in mechanical properties. An improved ductile irradiated zirconium alloy is described in U.S. Pat. No. 4,879,093 issued to an inventor in this application. The alloy has a stabilized microstructure which minimizes loss of alloy ductility required to resist release of fission gases and to handle spent fuel safely. The alloy retains a reasonable corrosion resistance in both pressurized water reactors (PWR) and boiling water reactors (BWR) because of its optimum intermetallic precipitate average particle size. The alloy of the '093 patent is based on an alpha phase zirconium-tin-niobium or alpha phase zirconium-tin-molybdenum alloy having characteristics as shown in Table 1 of that patent with niobium, if present, in a range of from a measurable amount up to 0.6 percent by weight. The molybdenum, if present, is in a range of from a measurable amount up to 0.1 percent by weight. The zirconium-tin system is known as "Zircaloy" and, typically, if Zircaloy-4, for example, would also have 0.18 to 0.24 percent by weight iron, 0.07 to 0.13 percent by weight chromium, oxygen in the range of from 1000 to 1600 ppm, 1.2 to 1.7 percent by weight tin, and the remainder zirconium. U.S. Pat. No. 4,992,240 discloses another zirconium alloy containing on a weight basis, 0.4 to 1.2% tin, 0.2 to 0.4% iron, 0.1 to 0.6% chromium, not higher than 0.5% of niobium, and balance zirconium, wherein the sum weight proportions of tin, iron and chromium is in the range of 0.9 to 1.5%. Oxygen, according to FIG. 4 of the '240 patent, is about 1770 ppm to 1840 ppm. Niobium is apparently optional, and silicon is not reported. Recent trends in the nuclear industry include shifts toward higher coolant temperatures to increase the thermal efficiency and toward higher fuel discharge burnups to increase the fuel utilization. Both the higher coolant temperatures and discharge burnups tend to increase the in-reactor corrosion and hydrogen uptake of the zirconium alloys. The high levels of neutron fluence and simultaneous hydrogen pickup degrade the ductility of zirconium alloys. For these more demanding service conditions, it is therefore necessary to improve the corrosion resistance and irradiated ductility of zirconium alloys. Accordingly, it is a continuing problem in this art to develop a zirconium alloy having superior ductility after irradiation; good corrosion resistance, especially independent of processing history; reduced hydrogen absorption by the alloy; and a significant solid solution alloy strength. It is another continuing general problem in this art to improve the corrosion resistance and irradiated ductility of zirconium alloys used in fuel assembly structural components in nuclear reactors. It is another continuing general problem in this art to provide a zirconium alloy which has superior creep resistance, superior corrosion resistance, and low neutron absorption cross section by the selection of alloying elements in particular ranges. It is another continuing general problem in this art to provide a zirconium alloy with selected alloying elements to assist in reducing hydrogen uptake of the alloy.
	claims	1. A nuclear reactor system comprising:a reactor comprising:a reactor tank;a reactor core within the reactor tank, the reactor core comprising a fuel column of metal or cermet fuel using liquid sodium as a heat transfer medium; anda pump for circulating the liquid sodium through a heat exchanger; andat least one passive safety system comprising reactivity feedbacks;at least one passive load follow system; andwherein the system produces approximately 50 MWe to approximately 100 MWe. 2. The nuclear reactor system of claim 1, further comprising a heat source reactor driving a supercritical CO2 Brayton cycle energy converter. 3. The nuclear reactor system of claim 2, wherein the energy converter has a conversion efficiency of approximately 39% to approximately 41%. 4. The nuclear reactor system of claim 1, further comprising a heat source reactor driving a Rankine steam cycle. 5. The nuclear reactor system of claim 1, further comprising bottoming cycles for cogeneration. 6. The nuclear reactor system of claim 1, further comprising a balance of plant with no nuclear safety function. 7. The nuclear reactor system of claim 1, wherein the reactor tank comprises thin walled stainless steel. 8. The nuclear reactor system of claim 1, wherein the reactor tank is positioned in a guard vessel. 9. The nuclear reactor system of claim 8, wherein the reactor tank further comprises a deck, and wherein at least the deck is enclosed by a removable dome. 10. The nuclear reactor system of claim 9, wherein the guard vessel and the removable dome form a containment structure. 11. The nuclear reactor system of claim 10, wherein the containment structure is emplaced in a silo shield structure with seismic isolation. 12. The nuclear reactor system of claim 1, wherein the reactor core comprises enriched uranium/zirconium alloy for an initial core. 13. The nuclear reactor system of claim 1, wherein the reactor core comprises recycled uranium/transuranic zirconium for refueling cores. 14. The nuclear reactor system of claim 1, wherein the reactor core comprises one or more multi-assembly clusters. 15. The nuclear reactor system of claim 14, wherein the one or more multi-assembly clusters have derated specific power (kwt/kg fuel) for enabling long refueling intervals and enabling refueling operations to begin approximately two weeks after reactor shutdown. 16. The nuclear reactor system of claim 1, wherein the system comprises a burnup swing of less than approximately 1% Δk/k. 17. The nuclear reactor system of claim 1, wherein the at least one passive safety system comprises a passive decay heat removal channel. 18. The nuclear reactor system of claim 17, wherein the passive decay heat removal channel operates at less than or approximately equal to 1% full power. 19. The nuclear reactor system of claim 1, wherein the at least one passive safety system relate to power characteristics, fuel characteristics, and coolant temperatures. 20. The nuclear reactor system of claim 1, wherein the at least one passive load follow system comprises sensing balance of plant demand communicated via flow rate and return temperature of a heat transport loop. 21. The nuclear reactor system of claim 1, wherein the system produces approximately 100 MWe. 22. A method for providing nuclear energy, the method comprising:providing a nuclear reactor system, the system comprising:a reactor comprising:a reactor tank;a reactor core within the reactor tank, the reactor core comprising a fuel column of metal or cermet fuel using liquid sodium as a heat transfer medium; anda pump for circulating the liquid sodium through a heat exchanger;at least one passive safety system comprising reactivity feedbacks; andat least one passive load follow system;initiating the nuclear reactor system;converting heat to electricity; andsupplying the electricity, andwherein the system produces approximately 50 MWe to approximately 100 MWe. 23. The method of claim 22, further comprising a balance of plant with no nuclear safety function. 24. The method of claim 22, wherein the at least one passive safety system comprises a passive decay heat removal channel. 25. The method of claim 22, wherein the at least one passive load follow system comprises sensing balance of plant demand communicated via flow rate and return temperature of a heat transport loop.
	claims	1. A rotary electrostatic actuator (EA) apparatus comprising:a high voltage source of at least about 40 kV;a target material receiving voltage from said high voltage source;wherein a source vane is attracted to said target material as a result of charges attracted to higher E fields;wherein said actuator implements partial discharge; andwherein said partial discharge comprises a storage capacitor re-charging said target. 2. The device of claim 1, wherein said source comprises a radioisotope emission high voltage source. 3. The device of claim 2, wherein said source comprises S35. 4. The device of claim 2, wherein said source comprises P32. 5. The device of claim 2, wherein said source comprises P33. 6. The device of claim 2, wherein said source comprises Ca45. 7. The device of claim 2, wherein said source comprises Sn123. 8. The device of claim 1, wherein said source comprises at least one of piezoelectric crystals and Van de Graff generator. 9. The device of claim 1, wherein said actuator is a disk rotor. 10. The device of claim 1, wherein said actuator is a vertical wall rotor. 11. The device of claim 1, wherein said actuator is a stacked rotor. 12. The device of claim 1, wherein said source comprises a replaceable source. 13. An electrostatic rotary actuator method comprising:providing emission from a source;capturing said emission by a target material;generating rotation from electrostatic force; anddischarging developed potential;wherein said actuator implements partial discharge; andwherein said partial discharge comprises a storage capacitor re-charging said target. 14. The method of claim 13, wherein said source is a radioisotope providing said emission. 15. The method of claim 14, wherein said source is a low atomic number, below about 17, beta emitter source. 16. The method of claim 14, wherein said radioisotope source further provides electrical power. 17. The method of claim 13, wherein said step of discharging comprises partial discharge. 18. A radioisotope fueled electrostatic disk rotary actuator nano air vehicle apparatus comprising:two pairs of chutes comprised of metal, wherein said two pairs of chutes comprise a surface film of a light metallic element;a rotating vane disk, between said two pairs of chutes and coaxial with said two pairs of chutes, said rotating vane disk comprising twenty four source vanes comprising beta-emitting radioisotope comprising at least one of S35 and Ca45, wherein said radioisotope comprises a source film with a thickness of about approximately one half penetration depth, whereby current is a maximum;a housing comprising a lead-plated vacuum envelope, enclosing said two pairs of chutes and said rotating vane disk, whereby emission products of said radioisotope are contained, said vacuum envelope is sputtered deposition plated with a lead layer of about approximately one micron, whereby surrounding area is protected from soft X-rays, and beta upset of localized electronics is prevented; andwherein rotation of said rotary actuator is magnetically coupled directly to a propeller component, thereby eliminating losses due to a mechanical gear box, whereby propulsion is provided to said nano air vehicle.
	description	The invention provides a radiopharmaceutical pig (xe2x80x9cpigxe2x80x9d) and transportation apparatus, which is lighter and more efficient that conventional pigs and transportation apparatus. Turning to FIG. 1, the pig 10 of the present invention has an elongated tubular sidewall 12 that extends between two closed ends 14, 16. The two closed ends 14, 16 are thicker and contain relatively more radiation shielding material than is contained in the elongated tubular sidewall 12. The two closed ends 14, 16 and side wall 12 form an interior chamber 18 to house a radioactive substance which may be contained within a syringe 20. The pig 10 also has a plastic liner 22 fitted inside the chamber 18 for protecting the syringe inside the pig 10. The radioactive resistant material used to make the pig 10 may be lead, whose thickness at the two closed ends 14, 16 sufficiently shields against penetration of radiation through the closed ends 14, 16 and whose thickness at the elongated tubular sidewall 12 itself may not be sufficient to provide adequate shielding against penetration of radiation from the radioactive substances inside the pig 10. To compensate for this radiation shielding deficiency in the sidewall 12 of the pig 10, the pig 10 is fitted within a cavity 24 defined by a radiation shield 26, whose thickness in addition to the thickness of the sidewall 12 of the pig 10 is sufficient to resist penetration of radiation, preferably by an amount at least as great as the amount of radiation penetration resistance provided by the closed ends 14, 16. Although the radiation shield 26 is required for resisting radiation penetration with respect to the elongated tubular sidewall 12, the radiation shield 26 can be configured with open ends 28, 30 because the lead at the two closed ends 14, 16 of the pig 10 is sufficient to provide the necessary shielding above and below the radioactive source inside the syringe 32. This aspect allows the closed ends 14, 16 of the pig 10 to extend beyond each of the open ends 28,30 of the radiation shield 26, which provides for a combination pig 10 and radiation shield 26 that is relatively lightweight. The pig 10 is preferably configured as an assembly of two sections wherein the two sections are selectively mated with each other for closing the pig through a threading configuration or any other suitable method of mating the two sections (e.g., clasp, tong and groove, etc.). FIG. 2 shows the conventional 5 cc syringe 32 filled to capacity and closed with a luer lock 34. A luer lock 34 is often used by radiopharmaceutical manufacturers producing FDG F18 as a safety measure to prevent leakage. This is particularly important when air shipping the FDG F18 because the closed syringe must be able to withstand varied air pressures. The syringe 32 resides in the plastic liner 22 of the pig 10 (FIG. 3). As shown in FIG. 3, the pig 10 has two sections 36, 38 that mate with each other via a thread configuration 40. The thread configuration 40 is at the outside of inner end 42 of the section 38 at the inside of widened lip 44 of the section 36. Turning to FIG. 4, the radiation shield 26 is supported in a shipping container 46 such as a conventional metallic ammunition can or plastic or cardboard container. A sheet metal bracket 48 or some other sufficiently rigid bracket material 48 may be affixed to an inside surface in the case of the container 46 can and held in place with high density foam 50 (FIG. 5), such as high density polyurethane or polyethylene foam. Additional foam 50 between the base 56 of the container 46 (FIG. 1) and a lid 54 clamp the pig 10 in place upon fastening the lid 54 of the container 46. As shown in FIG. 1, radiation shield 26 is configured to define a cavity 24 into which the pig 10 is arranged. In the preferred embodiment, the radiation shield 26 has a contour that converges toward each of the open ends 28, providing a central area 56 between the two ends that is thicker than the area of the radiation shield 26 proximate to each of the ends. This configuration provides sufficient shielding while minimizing weight. Those skilled in the art will recognize that while the radiation shield 26 illustrated is contoured at both ends, only one end could be contoured, only part of one end could be contoured, the contour could be smaller, it could be arcuate rather than flat, etc. So long as the shape makes the weight less than a full cylindrical shape but maintains sufficient radiation shielding it will still fall within the scope of the invention. This highly efficient use of the radiation shield 26 allows for the adequate shielding of a FDG F18 dose as high as 700 mCi in containers that weigh less than 50 lbs. and still have a removable pig 10. A different, lighter weight, radiation shield 26 can be used for smaller doses by modifying the radiation shield 26, shown in FIG. 1, to have less lead to create an even lighter shipping container. This saves shipping charges and may also reduce the risk of injury to the people handling the containers as compared to conventional arrangements. According to DOT regulations, the radioactivity reading on the surface of the shipping container must be less than 50 mRems/hour and must also be less than about 1 mRems/hour at a reading that is taken at a distance of about 1 meter from the shipping container. The amount of lead required for adequate shielding is based on conventional formulae and tables that take into account the pharmaceutical properties, shielding material and distance between the radioactive substance and the outside of the shipping container. The required amount of shielding material drops off rapidly as the distance to the outside of the container increases. FIG. 6 shows the minimum profile for the amount of lead required in the radiation shield 26. The distance between the center of the syringe 32 to the outside of the shipping container 46 along the angles shown is in inches or centimeters. The thickness of lead required for proper shielding, at specific Rems per hour (R), is shown in inches at various angles. The numbers that appear in FIG. 6 near the center thereof show various required thicknesses of the lead forming the pig 10 of the present invention, in inches, for the angles shown. The distances from the radioactive substance to the outside of the shipping container 46 at the angles 58 shown and the thickness of lead in the pig 10 in inches are used to determine the thickness requirements of the radiation shield 26 at the particular angles. The thicknesses are plotted along the angle lines. These points are connected to show the minimum profile 60 of the lead radiation shield. The profile is then modified into a shape 62 that can be manufactured and supported by the shipping container 46. The minimum amount of lead required in the closed end portions of the pig is dependent upon the activity of the dose being shipped and the distance from the center of the radiopharmaceutical substance to the outside of the shipping container 46. For a dosage of 700 mCi, the end portions of the pig 10 near the lid 52 in the container 46 requires about 1{fraction (9/16)}xe2x80x3 lead and the other end portion requires about 1xe2x85x9exe2x80x3 lead. If 150 mCi are to be shipped, then about 1.20xe2x80x3 lead and 1.39xe2x80x3 lead would be required, respectively. FIG. 7 shows another embodiment of the invention for shipping multiple doses of radioactive substances in a single shipping container 46. FIG. 7 shows two individual pigs 10 each placed inside a respective radiation shield 26 configured to accommodate the two pigs 10. The double radiation shield 26 defines two cavities into which are arranged the two pigs 10 wherein the double radiation shield 26 and pigs 10 limit an amount of radioactivity emanating from the radioactive substances and penetrating the pigs 10 and shield 26 to less than about 50 mRems/hour at the surface of the container 46. This embodiment is particularly convenient for nuclear medical facilities that perform multiple PET imaging studies in a single day. The initial strength of each dose depends on the distance between the facility and on the duration of the multiple image studies. The double radiation shield 26 is supported by a sheet metal bracket 64 or some other suitable material, which may be placed inside a conventional container 46, configured to support the two pigs 10. High density foam 66, as described in connection with the first embodiment of the present invention, is used to keep the pigs 10 in place inside the container 46. Both pigs 10 and the double radiation shield 26 can fit into a standard ammunition can and still weigh less than about 50 lbs. FIG. 8 shows the syringes 32 and plastic liners used in a second embodiment of the present invention. Each syringe 32 is placed into its own pig 10. Each dose of radiation substance in each of the syringes 32 contains up to 150 mCi. The pigs 10 which now contain the two syringes 32 with their corresponding single doses of radiation substances are then placed into a double radiation shield 26 configured to accommodate the two pigs 10. High density foam 66 keeps the pigs 10 in place against moving inside the container 46. Although the above describes particular embodiments of the invention, many other variations and modifications and other uses may become apparent to those skilled in the art. It is preferred, that the present invention not be limited by this specific disclosure herein, but only by the appended claims.
	description	This is an application filed under 35 USC §371 of PCT/EP2014/059828 filed on May 14, 2014 claiming priority to DE 10 2013 104 986.9 filed on May 15, 2013. The present invention relates to a device for applying laser radiation to the outside of a rotationally symmetrical component. In the propagation direction of the laser radiation, the average propagation direction of the laser radiation is identified, in particular when the laser radiation is not a plane wave or is at least partially divergent. Laser beam, light beam, partial beam or beam does not, unless expressly stated otherwise, refer to an idealized beam of the geometrical optics, but to a real light beam, such as a laser beam with a Gaussian profile or a modified Gaussian profile or a top hat profile, which does not have an infinitesimally small, but an extended beam cross-section. Diode lasers are often used when welding rotationally symmetric, in particular circular-cylindrical plastic parts from the outside. Typically, two methods or device types are used. In a first prior art device, a beam is moved around the component, or the component rotates in a laser beam. The disadvantage of such device is that parts have to be moved and welding does not take place simultaneously. This may adversely affect the quality of the weld. In a second prior art device, several for example divergent beam sources illuminate the part from an annular arrangement. FIG. 4 shows schematically such a device where five laser beams 1 are incident on a rotationally symmetrical component 2 from five different directions. Such devices have the disadvantage that the angles at which the component 2 is irradiated are different at the surface of the component 2. Reflection and absorption therefore vary across the component. Furthermore, a defined illumination can be achieved only for a fixed diameter of the component (see FIG. 4). When the diameter of the component 2′ is larger, parts 3 of the surface are not exposed to laser radiation (see FIG. 5). When the diameter of the component 2″ is smaller, a part 4 of the laser radiation bypasses the component 2′ (see FIG. 6). The problem underlying the present invention is to provide a device of the aforementioned type, wherein the exposure to the laser radiation is comparatively independent of the diameter of the component and/or wherein the laser radiation incident on the outside of the component has a homogeneous angular distribution. This is attained by the invention with a generic device having the features of claim 1. The dependent claims relate to preferred embodiments of the invention. According to claim 1, the device has a plurality of lenses which are configured and/or arranged such that the axis of symmetry of the component is at the focal point of each of the lenses. Such an arrangement ensures that laser radiation passing through the lens and incident on the component has a homogeneous angular distribution. This homogeneous angular distribution can, on the one hand, ensure that the outside of the component is homogeneously exposed to laser radiation in the circumferential direction, wherein the absorption and reflection of the laser radiation then also does not change along the periphery due to the identical incident angle. On the other hand, the homogeneous angular distribution of the laser radiation can help to ensure that components having different diameters can be optimally exposed to laser radiation. The device may include homogenizing means capable of homogenizing the laser radiation before passing through the lenses. In this manner, a high degree of homogeneity of the angular distribution incident onto the component of the laser radiation is ensured. For example, when the number of lenses is less than eight, the homogenizing means may be designed in such a way that the laser radiation has a top-hat intensity distribution with an intensity that decreases toward the edges according to cos2 (φ), whereas the homogenizing means may be designed, when the number of the lenses is greater than or equal to eight, in such a way that the laser radiation has a linear top-hat intensity distribution. The homogenizing means may include one, preferably two lens arrays or a light guide. Alternatively, the homogenizing means may include a waveguide with an at least partially cuboidal light-guiding region. A first extent of the light-guiding region which extends between an entrance face and an exit surface of the light-guiding region may be greater than a second and/or a third extent of the light-guiding region perpendicular to the first extent, preferably by a factor of at least 3, particularly by a factor of at least 7, for example by a factor of at least 10 greater, and/or may preferably be greater by a factor of at most 100, especially of at most 50, for example, of at most 40. With this design, for example, a homogeneous intensity distribution that decreases slightly toward the edge, for example as cos2 (φ), can be created. At least two or each of the lenses may have the same focal length. With this measure, the device can be constructed coaxially in relation to the symmetry axis of the component, thereby making it easier to achieve a homogeneous angular distribution of the incident laser radiation on the component. The device may include at least one laser light source, preferably a plurality of laser light sources that can generate laser radiation incident on the component. In particular, a laser light source may be assigned to each of the lenses. Suitable laser light sources are, for example, a laser diode bar or fiber-coupled diode lasers. The device may include optical means, which can apply laser radiation to at least one or each of the lenses, in particular laser radiation emitted by the at least one laser light source. The optical means may include, for example, imaging or focusing lenses. Furthermore, the optical means may include the homogenizing means. For example, the optical means and/or the homogenizing means may be designed such that a homogeneous spatial distribution or a homogeneous spatial intensity distribution of the laser radiation is incident on the entrance face of each of the lenses. By way of the lenses, a homogeneous spatial distribution is converted into a homogeneous angular distribution. Alternatively, the optical means and/or the homogenizing means may be designed such that a spatial distribution that is matched to the design of the lens or a spatial intensity distribution of the laser radiation that is matched to the design of the lens is incident on the entrance face of each of the lenses. For example, spatial intensity distributions that gently decrease toward the edges may be incident on lenses that are similar to ideal lenses, thereby contributing to an even more homogeneous intensity distribution on the component. In other lens designs, for example in real lenses or F-Theta lenses, other suitable spatial intensity distributions or spatial distributions of the laser radiation may be incident on the lenses. The optical means may include collimating means, in particular at least one lens for collimation, that are configured and arranged in the device such that the laser radiation is incident on the lenses with no divergence or with the lowest possible divergence, or at least substantially collimated. The collimation of the laser radiation incident on the lenses contributes to an increase in the homogeneity of the intensity distribution incident on the component. At least one or each of the lenses may be cylindrical lenses with cylinder axes parallel to the symmetry axis of the component. In this way, an annular intensity distribution is obtained on the outside of the component which corresponds to the length of the cylinder axes of the lenses in the direction of the axis of symmetry of the component. This intensity distribution can be moved, for example, as part of a machining process in the direction of the axis of symmetry of the component. Alternatively, at least one or each of the lenses may have a rotationally symmetrical curvature, and more particularly may be spherical lenses. In this way, a very narrow annular intensity distribution is produced on the outside of the component. This intensity distribution can, for example, also be moved in the course of a machining process in the direction of the axis of symmetry of the component. Furthermore, this intensity distribution can also be used to generate a continuous peripheral weld. The lenses may be arranged next to each other, in particular may adjoin each other, in the circumferential direction with respect to the axis of symmetry of the component. In this way, it can be ensured by using simple means that a uniform intensity distribution of the laser radiation is attained over the entire circumference of the component. Furthermore, at least one or each of the lenses may be arranged so that the direction in which the laser radiation propagates after passing through the at least one or each of the lenses has both a radial, as well as an axial component with respect to the axis of symmetry of the component. In this way, none of the laser light sources can be damaged by laser radiation reflected on the component or by laser radiation bypassing the component. Alternatively or additionally, the device may include a beam trap constructed to capture the laser radiation reflected by the component and/or bypassing the component and/or portions of the laser radiation transmitted through the component, wherein the beam trap has in particular an annular shape. With such a beam trap, laser radiation reflected on the component or laser radiation bypassing the component or laser radiation passing through a partially transparent component is prevented from damaging any of the laser light sources. In the figures, identical or functionally identical parts are provided with identical reference numerals. The embodiment of a device according to the invention illustrated in FIG. 1 to FIG. 3 includes five lenses 10. These lenses 10 are only schematically indicated in the figures by a respective line. The lenses 10 may be, for example, piano-convex or bi-convex or concave-convex lenses. Less than five lenses, in particular two or three or four lenses, or more than five lenses may conceivably be provided. The five lenses 10 are arranged on the sides of a regular pentagon parallel to these sides so that the lenses 10 adjoin each other at the corners of the pentagon. The focal length of each of the lenses 10 is identical and is selected so that the focus or the focal point or the focal line of all lenses is located at the same position. When a greater or a smaller number of lenses are used, the lens arrangement is changed accordingly so that for example with four lenses the lenses are arranged on the sides of a square. With only two lenses, the lenses are arranged parallel to each other and opposite from one another and spaced from one another. In the illustrated exemplary embodiment, the lenses 10 may be formed as cylindrical lenses having cylinder axes that are parallel to each other and extend in the plane of drawing. In this case, each of the lenses 10 has a focal line or a focus line. However, the lenses 10 may also each have a rotationally symmetrical curvature, and may in particular be spherical lenses. In this case, each of the lenses 10 a focal point or a focus point. A rotationally symmetrical component 11, in particular a circular cylinder (see FIG. 1) which extends in the drawing plane of FIG. 1 without any change in cross-section, is arranged intermediate between the lenses 10. The component 11 is arranged such that the foci of the lenses 10 are located on the axis of symmetry 12 and the cylinder axis of the component 11. The device may further include at least one laser light source, preferably a plurality of laser light sources corresponding to the number of lenses and optical means constructed to apply the laser radiation 13 emanating from the laser light sources to the lenses. The optical means may include in particular collimation means, for example a plurality of lenses for collimation, which are configured and arranged in the device such that the laser radiation is incident on the lenses 10 with no divergence or with the smallest possible divergence or is at least substantially collimated. FIG. 1 shows as an example five laser beams 13 which are each incident from the outside perpendicular on the entrance faces of the lenses 10 facing away from the component. The laser beams 13 are merely indicated schematically. In particular, the laser beams 13 should each have a homogeneous spatial distribution or a homogeneous spatial intensity distribution on the entrance faces of the lenses 10. The laser beams 13 are each transformed by the lenses 10 so that the laser beams 13 each have a homogeneous angular distribution after exiting from the exit faces of the lenses 10 facing the component. As a result, the same laser power is incident on each peripheral section of the outside of the component 11, whereby the angles of incidence are also identical. FIG. 2 shows the device from FIG. 1, wherein a component 11′ which has an axis of symmetry 12′ and a larger diameter than the component 11 is positioned between the lenses 10. As it turns out, the outside this component 11′ is then also homogeneously illuminated. FIG. 3 shows the device from FIG. 1, wherein, a component 11″ which has an axis of symmetry 12″ and a smaller diameter than the component 11 is arranged between the lenses 10. As it turns out, the outside this component 11″ is then also homogeneously illuminated. Furthermore, in contrast to the embodiment shown in FIG. 6, no laser radiation bypasses the component 11″. The numerical aperture (NA) of the lenses 10 and their illumination can be selected so that with the selected number of lenses 10 the entire angular space of the circumference of the component 11, 11′, 11″ is illuminated. The numerical aperture of the lenses can here be determined as follows:NA=sin(α/2)with α=360°/number of lenses. Therefore, at least four lenses 10 are probably as realistic number in practice, because lenses with very large numerical aperture (NA>0.8) are difficult to produce. In order to ensure a homogeneous angular distribution of the individual laser beams 13 after the passage through the lenses 10, the lenses 10 should be illuminated with a homogeneous spatial distribution. The slow-axis distribution of laser diode bars is particularly suitable for this purpose. Accordingly, laser diode bars can be selected as the laser light sources. The slow-axis distribution can also be homogenized additionally. Corresponding homogenizing means will be described in more detail hereinafter with reference to FIGS. 7 to 12. Another suitable laser light source is a fiber-coupled diode laser. In this example, the fiber near field which is often relatively homogeneous can be imaged onto the lenses 10. Acylindrical lenses can be selected as lenses with a large numerical aperture, in special cases also round aspheres or cylindrical Fresnel lenses. In all variants, antireflection coatings disposed on the lenses should advantageously have an equally good transmission for all angles. The smallest diameter d of the component 11, 11′, 11″ can be deduced from the divergence of the laser radiation 13 incident on the lens 10, wherein all the laser radiation 13 impinges on the surface of the component 11, 11′, 11″. In a good F-Theta-approximation, the smallest diameter d is obtained asd=θ·f, wherein θ corresponds to the full divergence angle of the incident laser radiation and f corresponds to the focal length of the lenses 10. The largest diameter selectable for the component 11, 11′, 11″ is defined by the space available between the lenses 10. The diameter can be selected to be so large that the outside of the component 11, 11′, 11″ abuts the exit faces of the lenses 10. In practice, the maximum diameter can be chosen to be somewhat smaller in order to prevent an excessive amount of dirt from hitting the lenses 10. At least one lens 10 or each of the lenses 10 may be arranged so that the direction in which the laser radiation 13 spreads after passing through the at least one lens 10 or through each of the lenses 10 has with respect to the axis of symmetry 12, 12′, 12″ of the component 11, 11′, 11″ both a radial as well as an axial component. This can be achieved by tilting the lenses 10 relative to the axis of symmetry 12, 12′, 12″, so that the laser radiation 13 does not extend in the drawing plane of FIG. 1 to FIG. 3 after passing through the lenses 10, but is instead tilted upwardly or downwardly by a few angular degrees. This has the advantage that the laser radiation 13 reflected on the component 11, 11′, 11″ or the laser radiation 13 bypassing the component 11, 11′, 11″ cannot damage any of the laser light sources. Furthermore, an unillustrated beam trap may be provided, which may in particular have an annular shape. This beam trap can then capture the laser radiation reflected by the component 11, 11′, 11″ and/or transmitted through the component. FIG. 7 shows an exemplary device according to the invention, wherein the lenses are designed as piano-convex lenses 10. Like in the example shown in FIG. 1, five lenses 10 are arranged on the sides of a regular pentagon. However, as already mentioned above, less than five lenses 10, in particular two or three or four lenses 10, or more than five lenses 10, for example, six, seven, eight, nine or ten or more lenses 10, may be provided, wherein the lenses 10 are arranged in a regular arrangement, for example, on a square, a regular hexagon or a regular octagon. Furthermore, the lenses 10 are arranged so that adjacent lenses 10 contact each other or adjoin one another. FIG. 8 shows a first embodiment of homogenizing means 14, which include two lens arrays 15, 16 as well as a merely schematically indicated lens 17. The lens 17 is arranged in the device so that the exit face of the second lens array 16 is disposed in the input-side focal plane of the lens 17 and the entrance face of the lens 10 is disposed in the exit-side focal plane of the lens 17. Here, the focal lengths f15, 16 of the individual lenses of the lens arrays 15, 16 are significantly smaller than the focal length f17 of the lens 17. The lens arrays 15, 16 may be cylindrical lens arrays with cylinder axes that extend in the drawing plane of FIG. 8. Furthermore, the lens 17 may also be a cylindrical lens with a cylinder axis extending into the drawing plane of FIG. 8. Only one lens of the lenses 10 for exposing the component 11 to laser radiation 13 is shown by way of example. However, a number of homogenizing means 14 corresponding to the number of lenses 10 shall be provided, so for example six lenses 10 and six homogenizing means 14 associated therewith or, for example, eight lenses 10 and eight homogenizing means 14 associated therewith. FIG. 9 shows a second embodiment of homogenizing means 18, which include an optical fiber 19 and an only schematically indicated lens 20. The comparatively homogeneous light from a fiber-coupled laser exits the end of the optical fiber 19. This homogeneous distribution is collimated by the lens 20 and propagates from the latter to the entrance face of the lens 10. The lens 20 may be a cylindrical lens with a cylinder axis extending in the drawing plane of FIG. 9. The distance between the end of the optical fiber 19 and the lens 20 corresponds to the focal length f20 of the lens 20. In FIG. 9, the divergence angle θ of the exiting light is shown somewhat exaggerated for a better illustration. Realistic divergence angles θ are between 12° and 26°. Only one lens of the lenses 10 for exposing the component 11 to laser radiation 13 is shown by way of example. However, the number of homogenizing means 18 should correspond to the number of lenses 10, so for example six homogenizing means 18 should be associated with six lenses 10 or, for example, eight homogenizing means 18 should likewise be associated with eight lenses 10. FIG. 12 shows a third embodiment of homogenizing means 21, which include a schematically indicated waveguide 22 and a telescope composed of two lenses 23, 24. The lenses 23, 24 may be cylindrical lenses with cylinder axes extending into the drawing plane of FIG. 9. The waveguide 22 is shown in FIG. 10 in greater detail and corresponds to a waveguide previously disclosed in WO 2014/001277. WO 2014/001277 is incorporated in the present application by reference. At certain ratios of the dimensions of the waveguide 22 illustrated in FIG. 10, light can emerge from the waveguide 22 with an angular intensity distribution that corresponds to a convex top-hat profile 25 at least in one direction, as shown as an example in FIG. 11, which shows the intensity I as a function of an angle φ, wherein the angle φ=0° corresponds to the average propagation direction of the light. The waveguide 22 has a light-guiding region 26 in the form of a cuboid. However, the light-guiding region 26 may only in sections have a cuboid shape, in particular may have a rectangular shape only in one or more planes perpendicular to the average propagation direction Z of the light. In order to obtain the aforementioned convex top-hat profile 25, in particular the extent D1 of the light-guiding region 26 may be greater than the second and/or the third extent D2, D3 of the light-guiding region 26, preferably by a factor of at least 3, in particular at least 7, for example at least 10, and/or may preferably be greater by a factor of at most 100, in particular at most 50, for example at most 40. FIG. 12 illustrates a lens 27 which transmits the laser light 13 emanating from a laser light source into the light-guiding region 26 of the waveguide 22. The focal lengths f23, f24 of the lenses 23, 24 have a mutual ratio of 1:2, so that the exit surface of the light-guiding region 26 is imaged onto the entry surface of the lens 10 with a magnification of a factor 2. However, other focal length ratios may be selected in order to achieve a different magnification. For example, a ten-fold or a twenty-fold magnification is possible. Only one lens of the lenses 10 for exposing the component 11 to laser radiation 13 is shown by way of example. However, the number of homogenizing means 21 should correspond to the number of lenses 10, so for example six homogenizing means 21 should be associated with six lenses 10 or, for example, eight homogenizing means 21 should likewise be associated with eight lenses 10. The decrease in the angular intensity distribution 25 toward the edges corresponds approximately to a decrease proportional to cos2 (φ). It turns out that with a number of lenses 10 less than eight, such a homogenized spatial intensity distribution or spatial distribution of the light on each of the lenses that decreases towards the edges especially with cos2 (φ), leads to a very uniform intensity distribution on the component 11. It should be noted at this point that the decrease toward the edges occurs in a direction that corresponds to the circumferential direction of the component 11, or occurs in the direction in which the lenses 10 adjoin each other. The reasons for selecting a spatial intensity distribution or spatial distribution of light that decreases towards the edges will now be explained with reference to FIGS. 13 to 15. FIG. 13 illustrates the intensity I of the laser radiation on the component 11 as a function of the angle φ for an ideal lens used as the lens 10, when the lens 10 is illuminated with collimated light and a linear top-hat distribution. φ=0° corresponds here to the light portion incident on the component 11 in the region of the optical axis of the lens 10. The illustrated intensity distribution 28 shows that the incident intensity for the edge regions of the section of the component 11 illuminated by the lens 10 is greater than for the central regions, which are arranged near the optical axis. FIG. 14 shows a spatial intensity distribution 29, or a spatial distribution on the lens 10 in relative units, wherein the magnitude of the intensity I in the region of the optical axis is set to 1. The intensity I decreases to the edges to about 80% of the value at the optical axis. The spatial intensity distribution 29 could be generated, for example, by using the homogenizing means 21 shown in FIG. 12. FIG. 15 illustrates the intensity I of the laser radiation on the component 11 as a function of the angle φ when an ideal lens is used as the lens 10 and when this lens is illuminated with collimated light that not have a linear top-hat distribution, but instead has the distribution 29 shown in FIG. 14. It turns out that the intensity distribution 30 obtained on the component 11 has in this case the same intensity I at all angular ranges. This ensures a very uniform illumination of the component 11 with laser radiation. When the ideal lens used for the representation of the lens 10 is substituted by a real lens or an F-theta lens, the shape of the spatial intensity distribution 29 on the lens 10 must be adapted at its deviation from an ideal lens. A likewise comparatively well homogenized intensity distribution that decreases mainly with cos2 (φ) toward the edges can be achieved with the aforementioned slow-axis distribution of laser diode bars. If the use of homogenizing means is to be dispensed with and the number of lenses 10 is less than eight, it is recommended to illuminate the entrance faces of the lenses 10 with the slow-axis distribution of laser diode bars. Once more, the slow axis should be disposed parallel to the circumferential direction of the component 11 or be arranged parallel to the direction in which the lenses 10 adjoin each other. If the number of lenses 10 is greater than or equal to eight, a uniform intensity distribution on the component 11 can also be achieved with a linear top-hat distribution or with a non-decreasing intensity distribution, which can be obtained, for example, with the homogenizing means 14, 18 shown in FIG. 8 and FIG. 9.
	abstract	The present invention is directed to a CT imaging system utilizing a pre-subject cone-angle dependent filter to optimize dosage applied to the scan subject for data acquisition. The cone angle dependent pre-subject filter is designed to have a shape that is thicker for outer detector rows and thinner for inner detector rows. As a result, x-rays corresponding to the outer detector rows undergo greater filtering than the x-rays corresponding to the inner detector rows.
	description	The invention relates to a beam optical component having a charged particle lens for focussing a charged particle beam. The invention also relates to a charged particle beam device including said beam optical component and a method for aligning said beam optical component. Improvements of charged particle beam devices, like electron microscopes, electron or ion beam inspection or pattern generating tools, e.g. focused ion beam devices (FIB), depend on further improvements of their beam optical components. Beam optical components include, for example, electrostatic or magnetic charged particle lenses, deflectors, beam apertures, charged particle beam sources and the like. Charged particle lenses require a high degree of mechanical precision in order to obtain a focus spot of the smallest possible size, which is a prerequisite for obtaining the highest possible spatial resolution when inspecting or structuring a specimen. High precision focussed charged particle beams are used in charged particle beam devices like electron microscopes, pattern generators for lithographic processes in the semiconductor industry or focused ion beam devices (FIB). Charged particle lenses usually use electrostatic or magnetic fields for focussing the charged particle beam. Charged particle lenses with electrostatic fields are usually composed of two or more electrodes that each have an opening through which the charged particle beam can pass. By applying appropriate voltages to the respective electrodes, the geometric shape of the electrodes and the electric potentials provide for an electrostatic field that can be used to focus an incoming charged particle beam. Charged particle lenses with magnetic fields, in contrast, are composed of two pole pieces with openings through which the charged particle beam can pass. By providing an appropriate magnetic flux to the respective pole pieces, the geometric shape of the pole pieces and the magnetic flux determine a magnetic field that can be used to focus an incoming charged particle beam. For a high focussing quality, it is important that the openings of the multiple electrodes or pole pieces are well aligned with respect to each other and with respect to the charged particle beam axis. For example, in order to obtain an electron or ion beam focus of a size smaller than 100 nm, the openings of the electrodes (or pole shoes) need to be aligned with respect to each other with a precision on a micrometer scale. Further, the smaller the openings, the smaller the alignment tolerances are. A method for producing charged particle lenses with a high alignment precision is disclosed, e.g. by S. Planck and R. Spehr in “Construction and fabrication of electrostatic field lenses for the SMART project” in the Annual Report 1996/1997 of “Licht- und Teilchenoptik”, Institut für angewandte Physik, Technische Unversität Darmstadt, Prof. Dr. Theo Tschudi on page 114. S. Planck and R. Spehr use insulating precision spheres between electrodes to position the openings of the electrodes with respect to each other. However, for further progress in the focussing of charged particle beams, the alignment of the openings to each other and to the charged particle beam is often not sufficient. It is therefore a first aspect of the present invention to provide a beam optical component that is capable of significantly focussing a charged particle beam. It is a further aspect of the present invention to provide a beam optical component that reduces beam optical aberrations due to misalignments of its elements to improve spatial resolution. It is yet a further aspect of the present invention to provide a method that facilitates an easy and precise alignment of the beam optical component. It is a further aspect of the present invention to provide a charged particle beam device that is capable of inspecting or structuring a specimen at the highest spatial resolution possible and, at the same time, provides a high flexibility for different applications. These and other advantages are achieved by the beam optical components according to claim 1, the charged particle beam device according to claim 34 and the method according to claim 39. Further advantages, features, aspects, and details of the invention are evident from the dependent claims, the description and the accompanying drawings. The claims are intended to be understood as a first non-limiting approach of defining the invention in general terms. The beam optical component according to claim 1 includes a charged particle lens whereby the charged particle lens includes a first element having a first opening, a second element having a second opening, and first driving means coupled to at least one out of the first element and the second element for aligning the first opening with respect to the second opening. With the first driving means, it is possible to align the first opening with respect to the second opening during the operation of the inspecting or structuring charged particle beam. It is also possible to align at least one of the first and second openings to a common symmetry axis during the operation of the inspecting or structuring charged particle beam. This way, the alignment can be carried out while observing the effects of alignment adjustments on images of a specimen generated by the charged particle beam. Such alignment can be carried out iteratively to a precision which can be made much higher than the alignment of charged particle lenses whose opening positions have been fixed during the manufacturing of the lens. Further, with the first driving means, it is possible to compensate for geometrical inaccuracies of the charged particle lens that are unavoidable when fabricating beam optical components. The improved alignment leads to reduced aberrational distortions of the beam. Further, the higher the alignment precision, the smaller the openings of the electrodes can be at a given alignment error budget. Further, a superior alignment precision opens up the possibility to use such small first, second and/or third openings that at least one of them can be used as a beam aperture. This way, additional beam aperture elements can be omitted which simplifies the operation of the charged particle beam. In a first preferred embodiment of the invention, first and/or second elements are respective first and/or second pole pieces. In this case, the charged particle lens focuses the charged particle beam by means of a magnetic field. In a second preferred embodiment of the invention, first and/or second elements are respective first and/or second electrodes. In this case, the charged particle lens focuses the charged particle beam by means of an electrostatic field. Further, in this case, it is preferred that the charged particle lens of the beam optical component includes a third element having a third opening for focussing the charged particle beam. This way, the beam optical component can be used as an Einzel-lens that minimizes interfering electric fields in regions outside the lens. Einzel-lenses are characterized by three electrodes where the outer two electrodes are at the same voltage (V1=V3). In this case, the focussing properties of an Einzel-lens are defined by the voltage difference between the middle electrode, which is at a second voltage V2, and the outer two electrodes which are at respective first and third voltages V1, V3. If the difference V2-V3 is positive, the Einzel-lens accelerates an incoming negatively charged particle beam made of, e.g., electrons. In this case, the Einzel-lens is also known as Accel-lens. If the difference V2-V3 is negative, the Einzel-lens decelerates an incoming negatively charged particle beam made of electrons. In this case, the Einzel-lens is also known as Decel-lens. However, the present application also applies to charged particle lenses where the first and third voltages V1, V3 of the outer two electrodes are not the same. In this case, the charged particle lens is known as immersion-lens. Preferably, the beam optical component is capable of aligning first and second elements to a common symmetry axis. In this case, for example, the first driving means may be capable of moving the first element with respect to the second element to the point where the first element is parallel to the second element and where the first opening has the same symmetry axis as the second opening. Such alignment improves the focussing quality of a charged particle beam. Preferably, the alignment of first, second and/or third electrodes includes moving the first, second and/or third electrodes to be parallel to each other. In a further preferred embodiment, the charged particle lens includes second driving means connected with at least one of the second element and the third element for aligning the second opening with respect to the third opening. In this case, first, second and third elements can be aligned in-situ independently from each other to provide for a best possible focussing. Preferably, the beam optical component includes a charged particle beam source. In this case, one of the first, second and third elements can be positioned to serve as an extracting electrode. Since such a design makes a separate extracting electrode obsolete, the number of electrodes that need to be aligned with respect to each other is reduced. Further, with the first and/or second driving means, the openings of the first, second and/or third electrodes can be aligned in-situ with respect to the charged particle beam source. This way, alignment errors can be eliminated from the beginning. In a further preferred embodiment, first, second and/or third elements are shaped and positioned with respect to the charged particle beam source to serve as a beam aperture for the charged particle beam. In this case, first and/or second driving means can be used to align both the beam aperture and the charged particle lens in one. This further reduces the number of elements that need to be aligned, thereby further reducing beam optical defects due to misalignment. Further, with the first, second and/or third elements acting as beam apertures near the charged particle beam source, the charged particle beam current can be adjusted to the required current early on which helps to reduce beam spread due to high current densities (Boersch-Effect). It is further preferred that the charged particle lens includes first, second and/or third measuring means to measure the locations of the respective first and/or second openings with respect to the second and/or third openings. This way, by feeding the information of the measured locations of the first and/or second measuring means back to the respective first and/or second driving means, the precision for aligning the first, second and/or third elements to each other can be drastically improved. In one embodiment, the first, second and/or third openings are rotationally symmetric, i.e. circular. In this case the beam optical component acts as a round lens. In another embodiment, the first, second and/or third openings are rectangular. In this case, the beam optical component acts as a cylinder lens. According to other embodiments of the invention, at least one of the first, second and/or third elements includes at least two openings. In this case, the first and/or second driving means can be used to replace one opening of a given element by another opening of the same element in-situ. If the two openings have a different size or geometry, an exchange of the openings can be used to provide for another beam aperture and/or another focussing lens. Therefore, providing at least one of the first, second and/or third elements with multiple openings opens up the possibility to in-situ adjust the optical behavior of the beam optical component according to the needs of a given application. Of course, it may also be possible that the third electrode, or one of the more than three electrodes of the charged particle lens, includes at least two openings. This way it is possible that the various openings of the first, second and third electrodes can be freely combined to provide for a large set of different beam optical lenses and aperture angles. For example, replacing a small opening of a given first or second element by a large opening can be used to increase the beam current but decrease the spatial resolution. On the other hand, replacing a large opening of a given first or second element by a small opening can be used to decrease the beam current but increase the spatial resolution and/or change the focussing. Further, it is preferred that at least two openings of the multiple openings of at least one of the first, second and/or third electrodes have the same size and geometry. This way, an opening that has been deformed due to extensive exposure to the charged particle beam while serving as a beam aperture, can be replaced by another opening of the same size and geometry in-situ without changing the beam optics. This method effectively enables an in-situ beam aperture replacement that saves time since the vacuum does not need to be broken for the replacement. Of course, the more openings of the same size and geometry an electrode has, the more beam aperture replacements are possible without having to break the vacuum. The present invention is also directed to a charged particle beam device for focussing a charged particle beam onto a specimen including a beam optical component according to the claims 1-33. The charged particle beam device may be used to focus an electron beam, an ion beam or any other charged particle beam. It may be, e.g., an electron microscope, an electron or ion beam inspection or pattern generating tool, or a focussed ion beam device (FIB). In a first preferred embodiment, the beam optical component may be used as an objective lens to focus the charged particle beam onto the specimen. With the first and/or second driving means, the objective lens can be precisely aligned to the charged particle beam while imaging a specimen which makes an alignment easier and more precise. In a second preferred embodiment, the beam optical component is positioned between the objective lens of the charged particle beam device and the charged particle beam source of the charged particle beam device. In this case, the beam optical component may be used as a beam aperture and/or as a condenser to define the beam current and spatial resolution of the charged particle beam device. Further, if the beam optical component is used as a condenser, it is preferred that the condenser is part of the charged particle beam source. In another preferred embodiment, first or second driving means are rigidly connected to at least two of the first, second and third electrodes. In this case, only one of the driving means can be used to align the openings of at least two electrodes to a common symmetry axis (beam axis). The present invention also includes the method according to claim 38. With the method, it is possible to align and adjust the beam optical component in-situ to optimize the focus of the charged particle beam for a given application. Further, if at least one of the first, second and third elements is positioned and shaped to act as a beam aperture, the beam aperture can be aligned in-situ to optimize the aperture angle of the charged particle beam. The beam optical component according to the invention includes a charged particle lens for focussing a charged particle beam. It may be used in charged particle beam devices like a charged particle beam microscope to probe a specimen, e.g. a scanning electron microscope (SEM), a transmission electron microscope (TEM), a scanning transmission microscope (STEM), or a device that uses the charged particle beams to structure a specimen like, e.g., an electron beam pattern generator to structure a lithographic mask. Further, the beam optical component may also be used in focused ion beam devices (FIBs) to slice, mill or inspect a specimen. If the charged particle lens of the beam optical component is a magnetic lens, the first and/or second elements are preferably first and/or second pole pieces having respective first and/or second openings. If the charged particle lens of the beam optical component is an electrostatic lens, the first, second and/or third elements are preferably first second and/or third electrodes having respective first second and/or third openings. The present invention is largely independent of the kind of driving means used for the first, second and or third driving means. Generally, the choice of driving means depends on the aspired spatial resolution of the charged particle beam device, on the charged particle beam energy, on the beam currents, the size of the specimen, and other parameters. Those parameters in turn define the required alignment precision, the required vacuum capability, the permitted electromagnetic interference with the charged particle beam and the like, with which the driving means must comply. Typically, the driving means of the present invention are remotely controllable in order to be able to carry out the alignment without breaking the vacuum within which the charged particle beam is operated. This way, the alignment can be carried out in-situ, i.e. during beam operation. This in turn makes it possible that the alignment is iteratively carried out based on images of a specimen obtained for each alignment position. This way, an alignment of the first, second and/or third openings with respect to each other with a precision of better than 1 micrometer and preferably better than 100 mm is possible. Such an alignment is generally more precise than an alignment carried out during fabrication of the charged particle lens. Further, typically, the first and/or second driving means are rigidly connected with at least one of the respective first, second and/or third elements. This way, the driving means fully define the spatial positions of the respective openings. Further, typically, the driving means are electrically controllable. In this case, the driving means may be stepping motors, piezo-drives, DC-motors or other means. For applications that require a focussing spot size of less than a micrometer, it is preferred that the driving means are capable of moving the electrodes and/or pole pieces with respect to each other at a spatial resolution which is in the sub-micron range, preferably below 100 nm and even more preferred below 20 nm. Generally, for a very high alignment precision, piezo-drives are the preferred means for aligning the first, second and/or third openings to each other. Typically, commercially available piezo-drives are taken that are capable of providing a positioning accuracy of less than 20 nm for each of the three axes (x-y-z-axes), that may provide a travel distance of up to 200 mm and more, that are ultra high vacuum compatible, and that keep the magnetic interference to the charged particle beam at a level of less than 500 nano Tesla. Such piezo-drives may be installed directly to the respective electrode or pole piece within the vacuum chamber. To obtain a superior spatial resolution, piezo-drives may have encoders that measure the actual location of the respective first and/or second openings with respect to the second and/or third openings. Then, the information of the measured locations is fed to the respective driving means to adjust the actual position to the desired locations. Even more preferred, driving means and measuring means are contained within one unit, e.g. DC-motor and encoder, or piezo-drive and encoder. The following figures disclose several embodiments according to the invention. They represent only non-limiting examples. Therefore, it is clear to a person skilled in the art that it is well within the scope of the invention to combine the features of the embodiments in various ways. FIGS. 1a-b depict a beam optical component according to the invention having an electrostatic charged particle lens 1 at two different aligning states. Charged particle lens 1 includes a first electrode 5 having a first opening 7 and a second electrode 9 having a second opening 11 to focus the charged particle beam 3 onto a specimen 17. The charged particle lens 1 of FIGS. 1a-b serves as an objective lens to focus the charged particle beam 3 onto a specimen 17. In the design of FIG. 1a-b, specimen voltage V0 connected with a specimen holder 19, first voltage V1 connected with the first electrode 5 and second voltage V2 connected with the second electrode 9, and shape and positions of the first and second openings 7, 11, define the shape of the electric field that focuses the charged particle beam 3. In FIG. 1a-b, first and second openings 7, 11 are circular in order to provide a highly rotationally symmetric focussing electric field. A highly rotationally symmetric field usually provides for the smallest focussing spot size. The values of the first and second voltages V1, V2, and the value of the specimen voltage V0, depend strongly on the application. However, a person skilled in the art knows which values to choose for a given application. In FIG. 1a, the first opening 7 is not aligned with respect to the second opening 11, i.e. the first central axis 47 of the first opening 7 is not aligned with the second central axis 48 of the second opening 11. In this case, the rotational symmetry of the electrostatic focussing lens 1 with respect to the symmetry axis 15 is distorted. Accordingly, the charged particle beam 3 becomes distorted while passing through the first and second openings 7, 11 and, as a consequence, the focus spot size 4 of the charged particle beam 3 on specimen 17 is increased and off-axis. Such misalignment deteriorates the spatial resolution of a charged particle beam device that uses such charged particle lens 1. In order to correct the misalignment, first driving means 13 move first electrode 5 laterally with respect to the second electrode 9 until first opening 7 is aligned with respect to the second opening 11, as shown in FIG. 1b. In FIG. 1b, first and second openings 7, 11, i.e. first and second central axes 47, 48, are aligned to common symmetry axis 15. Further, common symmetry axis 15 is aligned to the axis of the charged particle beam 3. In this case, the focussing electric field is rotationally symmetric with respect to the charged particle beam 3 which provides for a focus which is on-axis and has a minimum focus spot size 4 on the specimen. In FIG. 1a-b, driving means 13 are included of an x-drive 13x that is capable of moving the first electrode into the x-direction laterally to the beam direction (z-direction), and a y-drive 13y that is capable of moving the first electrode into the y-direction laterally to the beam direction and perpendicular to the x-direction. The independent movements of the two drives provide that the first electrode 5 can be moved into any lateral direction within the respective maximum moving ranges of the two drives. As can be seen in FIG. 1b, the first electrode 5 has been shifted to the right in order to correct the misalignment of the first and second openings 7, 11. In FIGS. 1a-b, first driving means 13 are rigidly connected to the first and the second electrodes 5, 9. However, it is obvious to a person skilled in the art that the alignment of the two electrodes 5, 9 can also be achieved where the first driving means 13 is connected to the first electrode 5, but not to the second electrode 9. In this case, first driving means 13 is connected on one side with the first electrode 5 and on the other side with some other structure that is fixed, e.g. with respect to a beam column or specimen holder 19. If the driving means 13 in FIGS. 1a-b are made of a material that tends to outgas in vacuum, it is difficult to maintain a high quality vacuum that is usually required for operating a charged particle beam. In this case, it is preferred that there is a flexible vacuum wall between the driving means and the respective electrode or pole piece. With a flexible vacuum wall, the driving means can be operated in a normal atmospheric environment while the respective elements (i.e. electrode or pole piece) can be operated in a vacuum. In this case, aligning a first opening with respect to a second opening may be carried out by making the driving means move the flexible vacuum wall, which in turn makes the respective electrode or pole piece move. Often, flexible vacuum walls are realized as bellows made of steel or other vacuum compatible materials. A person skilled in the art knows how to setup a system where an electrode or pole piece within a vacuum chamber is aligned by driving means that are located outside of the vacuum. FIGS. 2a-b depict an example where the beam optical component according to the invention includes a magnetic charged particle lens 1000. As for the electrostatic charged particle lens 1, magnetic charged particle lens 1000 of FIGS. 2a-b serves as an objective lens to focus the charged particle beam 3 onto specimen 17. Charged particle lens 1000 is included of a coil 23 being rotationally symmetric with respect to the symmetry axis 15. Coil 23 is surrounded by yoke 21 that concentrates the magnetic flux to provide for a strong rotationally symmetric magnetic field in the region of the charged particle beam 3 between the first element 1005 (“first pole piece”) and the second element 1009 (“second pole piece”). Note that, in order for the magnetic flux to arrive at the first pole piece 1005, the magnetic field has to cross air gap 22 between yoke 21 and first pole piece 1005. Air gap 22 allows for a movement of the first pole piece 1005 with respect to the second pole piece 1009 in all directions lateral to the symmetry axis 15. Of course, it is preferred that the air gap 23 is as small as possible in order to minimize the loss of magnetic flux. Air gap 22 may even have no gap distance at all provided that the first pole piece 1005 is kept free to slide below yoke 21. First driving means 13 of FIG. 2a-b may be the same as described in FIG. 1a-b. They serve to align first opening 7 of first pole piece 1005 with respect to second opening 11 of second pole piece 1009. As in FIG. 1a-b, first driving means 13 may be included of an x-drive 13x and a y-drive 13y to enable the first pole piece 1005 to freely move laterally in x- and in y-directions with respect to the second pole piece 1009. FIG. 2a illustrates magnetic focussing lens 1000 in a situation where opening 7 of first pole piece 1005 is misaligned with respect to the opening 11 of the second pole piece 1009. In this case, charged particle beam 3 cannot be focussed to the smallest possible focus spot size 4. FIG. 2b illustrates the same magnetic focussing lens 1000 after first driving means 13 have moved first pole piece 1005 to a position where first opening 7 is aligned with respect to second pole piece 1009. Therefore, with first driving means 13, it is possible to compensate for misalignments of the pole piece openings, e.g. due to fabrication tolerances. FIG. 3 represents a third embodiment according to the invention. FIG. 3 depicts a beam optical component having an electrostatic charged particle lens 1 having first, second and third electrodes 5, 9, 25, each having respective first, second and third openings 7, 11, 27. First electrode 5 is connected to third voltage V3, second electrode 9 is connected to second voltage V2 and third electrode 25 to first voltage V1. For many applications, the outer two electrodes, i.e. first and third electrodes 5, 25, are operated at the same voltage. In this case, the electrostatic field within the lens hardly interferes with regions surrounding charged particle lens 1. In this case, charged particle lens 1 is operated as “Einzel-lens”. If first and third voltages V1 and V3 are not the same, charged particle lens 1 is usually referred to as immersion lens. In the example of FIG. 3, first driving means 13 are used to align first opening 7 of first electrode 5 to second opening 11 and third opening 27. Different from FIG. 1a-b, one side of driving means 13 is connected with first electrode 5, while the other side of driving means 13 is connected to a first base plate 36 that is preferably fixed to some structure, e.g. the beam column. First driving means 13 may be the same as the one shown in FIGS. 1a-b or FIGS. 2a-b with the difference that in this case, first driving means 13 include two or three z-drives 13z to move first electrode 5 at two or three different positions into the z-direction, i.e. into the beam direction (see FIG. 9). Since the three z-drives can be operated independently from each other, it is possible to change the orientation of the central axis 47 (not shown) of the first opening 7 with respect to symmetry axis 15. This way, in addition to the lateral alignment within the x-y plane by x-rive 13x and y-drive 13y, first electrode 5 can be aligned to be perfectly parallel with respect to second electrode 9 and/or third electrode 25. Charged particle lens 1 of FIG. 3 also includes first measuring means 30 to measure the actual location of first opening 7. Preferably, measuring means 30 include an x-sensor 30x to measure the location within the x-direction, a y-sensor 30y to measure the location within the y-direction, and a z-sensor 30z to measure the location within the z-direction. The measured values are directed via cable 38a to an x-y-z-encoder which turns the measured values into a position, and from there via cable 38b to an x-y-z-controller 34 which compares the measured location with the desired location. In the case that the x-y-z-controller 34 determines a difference between the measured and the desired locations, it issues a command via cable 38c to x-drive 13x, y-drive 13y and/or z-drive 13z to move the first electrode 5 in a way that eliminates that difference. First measuring means 30, cable 38a,b,c, x-y-z-encoder 32, and x-y-z-controller represent a feedback system that helps to drastically improve the alignment precision which, depending on the types of driving or measuring means, can be as good as 500 nm or better. In FIG. 3, only first electrode 5 is movable by means of a driving means. Second electrode 9 and third electrode 25, in contrast, are aligned with respect to each other by at least three distance pieces 40. Distance pieces 40 are almost perfectly rounded electrically insulating spheres that may have a maximum deviation from a perfect sphere of about 1 or 2 micrometers. The use of such sphere for an alignment of electrodes has been described, for example, in S. Planck and R. Spehr in “Construction and fabrication of electrostatic field lenses for the SMART project” in the Annual Report 1996/1997 of “Licht- und Teilchenoptik”, Institut für angewandte Physik, Technische Unversität Darmstadt, Prof. Dr. Theo Tschudi on page 114, which herewith is enclosed into the description. Due to the very high geometric precision of the spheres, it is possible to align second opening 11 with respect to third opening 27 with a precision of typically 1 micrometer. However, in the design of S. Planck and R. Spehr, the alignment of adjacent electrodes is often hampered by deformations of the electrodes due to the pressure that the screws, which hold the two electrodes together, exert onto the electrodes. It is therefore a further aspect of the invention that in the designs of FIGS. 3 and 5-7, electrode 9 and third electrode 25 are fastened to the spherical distance pieces 40 by notched pins 57 and springs 53 as indicated in the drawings, and explained in more detail in the description for FIG. 9a-c. Using driving means for only one or two electrodes of the three electrodes 5, 9 and 25 simplifies the setup considerably, compared to a design where every electrode is connected to driving means. Further, for many applications, it is sufficient to align only one or two of the three electrodes, since it is often only one or two electrodes whose alignment is particularly critical for a lens performance. For example, generally, the smaller an opening radius of an electrode, the more critical its alignment is for the focussing performance. Therefore, since for Einzel-lenses the middle electrode usually has the largest opening, driving means often contribute to a better focussing only if the outer electrodes are moved. Further, in the case that one of the outer electrodes is used as a beam aperture for a charged particle beam device, it is often mainly the spatial precision of the opening of that electrode that matters for the focussing quality. Therefore, using driving means for only one electrode may turn out to provide the best balance between an achievable focussing quality and complexity of the beam optical component. FIG. 4 discloses a fourth embodiment according to the invention. The charged particle lens 1 of the beam optical component of FIG. 4 is the same as the one of FIG. 3, with the difference that it includes second driving means 42 for aligning second opening 11 with respect to the third opening 27 of the third electrode 25. Note that in FIG. 4, second electrode 9 is connected with first voltage V1, third electrode 25 is connected with second voltage V2, and first electrode 5 is connected with third voltage V3. Further, second driving means 42 are connected on one side to second electrode 9 and on the other side to second base plate 46 whose position is fixed with respect to the symmetry axis 15. With first driving means 13 and second driving means 42, first opening 7 and second opening 11 can be aligned to symmetry axis 15 independently. This makes it possible to align the first and second openings 7, 11 independently to the beam axis 3 which usually coincides with the symmetry axis 15. Since the outer electrodes, i.e. first electrode 5 and second electrode 9 of FIG. 4, have the smallest openings, those two need to be particularly well aligned. Generally, for Einzel-lenses, the outer electrodes tend to have smaller openings than the center electrode in order to provide a good shielding of the electrostatic lens field. For example, with an opening diameter of 1 millimeter, an alignment precision of typically better than 1 micrometer is required in order to render alignment errors irrelevant for the focussing. Note that both first and second driving means 13, 42 are equipped with respective first and second measuring means 30, 43 in order to provide for a feed back loop (not shown for second driving means 42) for improving the spatial resolution of first and second driving means. FIG. 5 discloses a fifth embodiment according to the invention. In FIG. 5, the beam optical component includes an electrostatic charged particle lens 1 of the type as shown in FIG. 3, and a charged particle beam source 62. The charged particle beam source 62 of FIG. 5 is included of an emitter 61 and an extracting electrode 60 to extract charged particles by means of extracting voltage Vext from emitter 61 into a vacuum to form charged particle beam 3. The beam optical component of FIG. 5 represents a compact design of a device that is capable of focussing a charged particle beam. Note that in FIG. 5, first electrode 5 is shaped and positioned with respect to charged particle beam source 62 to provide that first opening 7 serves as a beam aperture 50. Therefore, in order to minimize scattering of the charged particle beam 3 at the wall of the opening, beam aperture 50 is characterized by a knife-like edge that defines the size of opening 7. With first electrode 5 acting as a lens and as an aperture, the number of beam optical elements that need to be aligned with respect to each other can be reduced. First driving means 13, in this case, serve to align the focussing lens 1 and beam aperture 50 to charged particle beam source 62 at the same time. Also note that in FIG. 5, liner tube 52 is coaxially aligned with respect to symmetry axis 15. Liner tube 52 may be part of the beam optical component or not. Liner tube 52 is a conducting tube kept at a liner tube voltage (not shown) to provide a field free region within the tube for the charged particle beam 3 while drifting through liner tube 52 towards a specimen. Liner tube 52 protects the charged particle beam 3 from electric distortions generated from all sorts of electronic components that usually are part of a charged particle beam device, including distortions generated by driving means 13 and measuring means 30. The method for aligning the first opening 7 of first electrode 5 with respect to the second opening 11 of second electrode 9 is preferably carried out by the following steps: (a) providing a specimen that is to be inspected or structured or inspected by the charged particle beam 3; (b) scanning the charged particle beam 3 across the specimen 17 to generate a first image of the specimen 17 with a first set of voltages applied to the first element 5 and the second element 9. Preferably, the first image is generated by scanning the charged particle beam 3 across a first region of the specimen and detecting the particles that are generated on the specimen due to the interaction of the charged particle beam with the specimen at any scanned position; (c) scanning the charged particle beam 3 across the specimen 17 to generate a second image of the specimen 17 with a second set of voltages applied to the first element 5 and the second element 9. Preferably, the operational parameters of the charged particle beam device are the same for the first imaging and the second imaging except for the first set of voltages and the second set of voltages. Preferably, the first and the second set of voltages differ for only one electrode. If the electrostatic focussing lens 1 is included of at least three electrodes, it is preferred that the first set of voltages and the second set of voltages differ only by the voltages of the middle electrode, i.e. the electrode connected to second voltage V2. This is because changes of the second voltage V2 affect the electrostatic fields outside of the electrostatic focussing lens 1 minimally, compared to first and third voltages V1, V3 of the two outer electrodes; (d) moving the first electrode 5 with respect to the second electrode 9. This movement changes the alignment of the first opening 7 with respect to the second opening 11. The movement is preferably carried out by first driving means 13. (e) repeating the steps d), e), f), until at least one structure element of the specimen identified in the first image is identified in the second image. This step is based on the recognition that, the more a movement of the first electrode 5 improves the alignment of the first opening 7 with the second opening 11, the more specimen structure elements identified in the first image can also be identified in the second image. A perfect alignment would correspond to the case where the first image is identical with the second image except for the spatial resolution. On the other hand, if a movement of the first electrode 5 worsens the alignment of the first opening 7 with the second opening 11, the less specimen structure elements identified in the first image can be identified in the second image. This is because usually, the larger the misalignment, the more the region scanned during the first imaging deviates from the region scanned during the second imaging; Preferably, the charged particle beam 3 is generated by switching on the charged particle beam source 62, e.g. by applying a voltage V between emitter 61 and extracting electrode 60 (V=Vext−Vemit). If the charged particle beam source 62 is a thermal electron beam gun, a thermal field emitter cathode, a liquid metal ion source or any other electron or ion beam source known in the art, the generation of the charged particle beam 3 proceeds accordingly; When operating the charged particle beam device with a beam optical component having a charged particle lens 1 with three electrodes 5, 9, 25, it is preferred that the first and third voltages V1, V3, which are connected to the outer two electrodes, have the same value (V1=V3). This way, electrostatic interference of the focussing electrostatic field with the accelerating or deflecting fields outside of the electrostatic focussing lens 1 region (“Einzel-lens”) is minimized. In this case, the focussing length of electrostatic focussing lens 1 performance is essentially controlled by the second voltage V2, i.e. the voltage of the middle electrode, with respect to the first and third voltage V1, V3. Further, it is preferred that the liner tube voltage is equal to the third voltage V3, which is the voltage of the electrode closest to the liner tube 52. This way, the electrostatic interference between liner tube 52 and the focussing field defined by the third voltage V3 is minimized. FIG. 6 discloses a sixth embodiment according to the invention. In FIG. 6, the beam optical component, like in FIG. 5, includes an electrostatic charged particle lens 1 of the type as shown in FIG. 3, and a charged particle beam source 62. However, different from the design of FIG. 5, third electrode 25 of charged particle lens 1 is positioned close to the emitter 61 and connected to the extracting voltage Vext in order to serve both as extracting electrode and as third electrode of focussing lens 1. This further reduces the number of elements that need to be aligned with respect to each other. The design of FIG. 6 therefore provides for a compact beam optical component that helps to minimize beam optical distortions due to misalignments of its elements. FIGS. 7a-b disclose seventh and an eighths embodiments according to the invention. Both embodiments disclose charged particle lenses 1 that are similar to the design of FIG. 3, but have first electrodes 5 with multiple openings 7a, 7b, 7c. Thus, with first driving means 13 moving first electrodes 5 in x-direction, it is possible to replace an active opening of the first electrode 5 by one of the other openings 7a, 7b, 7c during beam operation. The term “active” refers to the opening that has been moved to be in line with the charged particle beam 3. The replacement is carried out by moving first electrode 5 with respect to the other electrodes until the active opening of first electrode 5 has been moved out of the active position and one of the other openings 7a, 7b, 7c of the electrode has been moved into the active position. For example, in FIG. 7a, by moving first electrode 5 in x-direction to the left, it is possible to move first opening 7a out of the active position and move second opening 7b into the active position during operation of the charged particle beam. This way, e.g. by replacing an opening 7a having a large size and a thick rim 8a by an opening 7b having a small opening and a thin rim thickness 8b, it is possible to modify the optical properties of the charged particle lens 1 without having to break the vacuum. For example, changing from a large opening 7a to a small opening 7b can be used to change the focussing length and/or to reduce beam aberration, depending on the application. Further, changing from an opening 7a having a thick rim 8a to an opening 7b having a thin rim 8b, can be used to effectively change the principal plane of the charged particle lens 1, which in turn changes the magnification of the beam optical system. This way, a zoom optic can be realized. Preferably, by replacing an active opening 7a, 7b, 7c by another of the multiple openings, the rim thickness 8a, 8b, 8c can be changed by more than a factor of two, preferably by more than a factor four and even more preferred by a factor of 10. FIG. 7b discloses another charged particle lens 1 that has a movable first electrode 5 with multiple openings 7a, 7b, 7c like in FIG. 7a. However, in FIG. 7b, first electrode 5 includes axially extending element structures 5a to provide that the distance of opening 7b to opening 11 in axial direction is smaller than the distance in axial direction of opening 7c or opening 7a to opening 11 of second electrode 9. This way, by moving opening 7b laterally out of the active position and opening 7c laterally into the active position, not only the thin rim thickness 8b of opening 7b is replaced by thick rim thickness 8c of opening 7c, but also the distances between the respective active openings of the first electrode 5 and the second electrode 9 is changed; for example, by moving first electrode 5 with respect to second electrode laterally to common symmetry axis 15, it is possible to change the distances between active openings of adjacent electrodes without having to use z-driving means 13z. Preferably, the distance between active openings can be changed this way by more than 10 percent, preferably by more than 50 percent, and even more preferred by more than 100 percent. The shapes of the first electrodes 5 of FIGS. 7a and 7b are only examples for many other ways in which first and/or second electrodes with multiple openings 7a, 7b, 7c can be shaped in order to provide for a more flexible beam optic. Generally, the first and/or second electrodes may have multiple openings that facilitate for an “in-situ” replacement the rim thickness, opening size and/or distance between adjacent openings. The more multiple openings of different geometry an electrode has, the larger the flexibility of the beam optical component to perform to a desired beam optical performance for different applications. In particular, if more than one electrode of the beam optical component have multiple openings of different geometries, the number of possible opening combinations increases rapidly. In any case, a skilled person will know how many openings the multiple openings of an electrode should have and what shape and of material they should be made in order to meet desired performances. Further, in the case that electrode 5 with the multiple openings 7a, 7b, 7c is positioned to define a beam aperture, the multiple openings of electrode 5 may be used to determine the beam intensity and spatial resolution. For example, by moving large opening 7a into the charged particle beam 3, the intensity of the charged particle beam is high but the spot is large. Vice versa, by moving a small opening 7b into the charged particle beam 3, intensity of the charged particle beam is low but the spot can be made smaller. Therefore, with the driving means and electrodes having multiple openings, the beam optical component can provide a flexibility that makes a charged particle beam device usable for many different fields of applications. Further, in the case that at least two of the multiple openings 7a, 7b of electrode 5 have the same size, a replacement of an active opening by another opening of the same size by driving means 13 can be used to replace a worn out opening 7a, 7b by a new opening 7a, 7b. Openings that are used as a beam apertures tend to wear out due to intense exposure to the charged particle beam. For example, in an electron beam device, electron beam exposure may lead to a contamination of the opening rim that may narrow the opening size. In an ion beam device, in contrast, ion beam exposure may lead to an increased opening size due to the ion beam sputtering effect that takes away material from the opening rim. In both cases, a regular replacement of one opening by a new one of the same size provides that the aperture angle remains more stable. FIG. 8a-b illustrate two kinds of electrodes 5 that can be used for the beam optical component of the present invention. In FIG. 8a, electrode 5 has a circular opening 7 to provide a rotationally symmetric focus. Central axis 47 of electrode 5 is defined by the symmetry axis of opening 7. In FIG. 8b, in contrast, electrode 5 has a rectangular opening 7 to provide a slit-like focus in only one dimension. Central axis 47 of electrode 5 of FIG. 7b is defined by the center of opening 7. FIG. 9a illustrates an ninth embodiment according to the invention. In this case, the charged particle lens 1 is identical to the one shown in FIG. 3 with the differences being: (a) that first driving means 13 provide for moving first electrode 5 in x- and y-direction but not in z-direction, (b) that first measuring means 30 provide for measuring the position of first electrode 5 in x- and y-direction but not in z-direction, and (c) that there are second driving means 42 connected to first and second electrodes 5, 9 that have three z-drives 13z to adjust the parallelism of the first electrode 5 with respect to the second and third electrodes 7, 25. FIG. 9b illustrates, as an example, possible positions of the three z-drives 13z with respect to second electrode 9 and its opening 11. By positioning three z-drives 13z at three different locations between the first and second electrodes 5, 9, it is possible to define the orientation of the first electrode 5 with the second electrode 9 with a high precision with respect to all three spatial axes. This way, a high degree of parallelism can be obtained. Note that taking three z-drives 13z at three different positions for a parallel alignment of adjacent electrodes is useful since it enables a three axis alignment to obtain a parallel orientation. In principle, however, it is also possible to use only two z-drives 13z at two different positions for a triple axis alignment if there is a distance element that keeps the distance between the adjacent electrodes fixed at a third position. FIG. 10a-c illustrate a way in which adjacent electrodes 5, 9 of a charged particle lens 1 can be aligned with respect to each other with high precision when no driving means are used. This alignment has already been mentioned when referring to the spherical distance pieces 40 of FIGS. 3 and 5-7. FIGS. 10a-c disclose different views on the spherically shaped distance piece 40 having two notched pins 57, i.e. a pin having a notch 55 engraved. Notched pins 57 are attached to spherically shaped distance piece 40 by, e.g., gluing or brazing. As can be seen from FIG. 10a-c, notched pins 57 are used to abut third electrode 25 to the spherically shaped distance piece 40 by means of a spring 53 inserted into notch 57 under the pressure exerted by third electrode 25 onto spring 53. This way, third electrode 25 is pushed down onto spherically shaped distance piece 40 at a pressure that is essentially given by the type of spring. FIG. 10c depicts notched pin 57 with spring 53 in more detail when viewed from the top. In the same way, it is possible to abut a second electrode of the charged particle lens 1 to the spherically shaped distance piece 40 on the opposite side of the sphere, i.e. where the other notched pin 57 is fastened. Due to the high geometrical precision of the spheres, and by using at least three spherically shaped distance pieces 40 to abut two electrodes to the respective spheres, it is possible to align the two adjacent electrodes to each other at high precision without having to glue the electrodes to each other. The use of spheres for aligning adjacent electrodes has been described originally by S. Planck and R. Spehr in “Construction and fabrication of electrostatic field lenses for the SMART project” in the Annual Report 1996/1997 of “Licht- und Teilchenoptik”, Institut für angewandte Physik, Technische Unversität Darmstadt, Prof. Dr. Theo Tschudi on page 114. The present design for aligning two adjacent electrodes is improved over the design of S. Planck and R. Spehr in that, in addition to a first electrode 5 having a first opening 7, a second electrode 9 having a second opening 11, and at least one spherical distance piece 40 positioned between said first electrode 5 and said at least second electrode 9 to provide for a minimum distance between said first electrode 5 and said second element 9, the beam optical component also includes a first holding piece, e.g. notched pin 57 with the spring 53, that is attached to said spherical distance piece 40. With the first holding piece 53, 57 attached to the at least one distance piece, the first electrode 5 can be held to the at least one spherical distance piece 40 at the point of mechanical support defined by the position of the spherical distance piece 40. Therefore, the pressure exerted by the first holding piece 53, 57 onto the first electrode 5 can be counteracted by the spherical distance piece 40 at the position where the first holding piece 53, 57 exerts its force onto the first electrode 5. This eliminates distorting or tilting forces onto the first electrode 5 which otherwise would deteriorate the quality of focussing a charged particle beam. The spherically shaped distance pieces 40 are preferably made of Al2O3. The fabrication of spheres with a geometric precision of typically 1 micrometer, made out of materials like Al2O3, is well known in the art. The diameters of the spheres can be chosen quite freely. For applications in charged particle beam devices, the spheres have typically a diameter between 1 mm to 100 mm. For applications in high energy beams, the diameter of the spheres may even have to exceed 100 mm in order to withstand the high voltages between the electrodes that are required by such high energy. Spherically shaped distance pieces 40 of the kind as shown in FIGS. 10a-c may also be fabricated from materials other than Al2O3, under the conditions that (a) the material is electrically insulating, (b) the material can be shaped to a sphere with a high geometric precision and (c) the material is hard enough to withstand the pressure exerted by an electrode that is pressed onto the sphere by a respective holding piece. For example, the spherically shaped distance piece 40 may be made of materials like insulating ceramics, glass, sapphire etc. The notched pins 57 in FIG. 10a-c are made of, e.g. stainless steel or, for brazing the pins into a spherically shaped distance piece, titanium or Vacon™. However, other electrically conducting or non-conducting materials can be used as well. In FIG. 10a-c, the notched pins 57 are attached to the spherically shaped distance piece 40 by gluing. To do this, two holes are drilled into the spherically shaped distance piece 40 on opposite sides along a same axis of the sphere. Then, the two notched pins 57 are each inserted into the respective holes after some glue has been filled into the holes. The beam optical components disclosed in this description are only specific non-limiting examples to describe one of many ways in which driving means connected to elements like electrodes or pole pieces can be used to improve the focussing quality, beam current control and spatial resolution of beam optical components. A person skilled in the art knows how to combine the various embodiments according to the invention, and how to adjust the embodiments in order to meet special requirements for other given beam focussing application. Those combinations and adjusted embodiments are within the scope of the present invention.
	abstract	A method for manufacturing an anti-scatter grid having a desired height. The method includes positioning a bottom surface of a mask of dielectric material, with a depth at least equal to the desired height of the anti-scatter grid, on a sheet of metal, cutting first and second series of intrinsically focused slots through a top surface of the mask to the sheet of metal, plating the sheet of metal at the bottom of each of the slots of the mask with a radiopaque material to form partition walls of the anti-scatter grid, and continuing to plate the radiopaque material into the slots of the mask until the desired height of the anti-scatter grid is achieved.
	claims	1. A source of photons comprising: a discharge chamber; first and second groups of ion beam sources in the discharge chamber, each electrostatically accelerating a beam of ions of a working gas toward a plasma discharge region, said first group of ion beam sources acting as a cathode and said second group of ion beam sources acting as an anode for delivering a heating current to the plasma discharge region; and a neutralizing mechanism for at least partially neutralizing said ion beams before they enter the plasma discharge region, wherein the neutralized beams and the heating current form a hot plasma that radiates photons. 2. A source as defined in claim 1 , wherein said ion beams precede said heating current. claim 1 3. A source as defined in claim 1 , wherein said heating current is pulsed and wherein said ion beams comprise pulsed ion beams that precede said pulsed heating current. claim 1 4. A source as defined in claim 1 , wherein said ion beam sources comprise continuous ion beam sources and wherein said heating current is pulsed. claim 1 5. A source as defined in claim 1 , wherein said first and second groups of ion beam sources are distributed around opposite halves of the plasma discharge region. claim 1 6. A source as defined in claim 5 , wherein said first and second groups of ion beam sources together comprise a spherical array. claim 5 7. A source as defined in claim 1 , further comprising a transformer having a primary and a secondary, wherein a first terminal of said secondary is coupled to said first group of ion beam sources and wherein a second terminal of said secondary is coupled to said second group of ion beam sources. claim 1 8. A source as defined in claim 7 , wherein the secondary of said transformer has a single turn. claim 7 9. A source as defined in claim 1 , wherein said first and second groups of ion beam sources comprise concentric electrode shells having sets of apertures aligned along axes which pass through the plasma discharge region, a first voltage source for applying a voltage between said electrode shells, and a gas source for supplying the working gas to the sets of apertures in said electrode shells. claim 1 10. A source as defined in claim 9 , further comprising a second voltage source coupled between said first and second groups of ion beam sources for supplying said heating current. claim 9 11. A source as defined in claim 1 , wherein said neutralizing mechanism comprises resonant charge exchange in each of said ion beams. claim 1 12. A source as defined in claim 1 , wherein said photons are in the soft X-ray or extreme ultraviolet wavelength range. claim 1 13. A source as defined in claim 1 , wherein the working gas is xenon and wherein the radiated photons have wavelengths in a range of about 10-15 nanometers. claim 1 14. A source as defined in claim 1 , wherein the working gas is selected from the group consisting of hydrogen, lithium, helium, nitrogen, oxygen, neon, argon and krypton. claim 1 15. A system for generating photons, comprising: a housing defining a discharge chamber; first and second groups of ion beam sources in the discharge chamber, each electrostatically accelerating a beam of ions of a working gas toward a plasma discharge region, said first group of ion beam sources acting as a cathode and said second group of ion beam sources acting as an anode; a first voltage source for applying an accelerating voltage to said first and second groups of ion beam sources; a second voltage source for supplying a heating current through the plasma discharge region between said first and second groups of ion beam sources; a gas source for supplying a working gas to the discharge chamber; a neutralizing mechanism for at least partially neutralizing said ion beams before they enter the plasma discharge region, wherein the neutralized beams enter the plasma discharge region and form a hot plasma that radiates photons; and a vacuum system for controlling the pressure of the working gas in the discharge chamber. 16. A system as defined in claim 15 , wherein said first and second groups of ion beam sources comprise concentric electrode shells having sets of apertures aligned along axes which pass through the plasma discharge region, wherein at least an inner electrode shell of said concentric electrode shells is divided to form said cathode and said anode. claim 15 17. A system as defined in claim 15 , wherein said ion beams precede said heating current. claim 15 18. A system as defined in claim 15 , wherein said first and second voltage sources are pulsed so as to provide pulsed ion beams that precede a pulsed heating current. claim 15 19. A system as defined in claim 15 , wherein said first voltage source produces continuous ion beams and wherein said second voltage source produces a pulsed heating current. claim 15 20. A system as defined in claim 15 , further comprising a transformer having a primary coupled to said second voltage source and a secondary coupled between said first and second groups of ion beam sources. claim 15 21. A method for generating photons, comprising the steps of: electrostatically accelerating a plurality of beams of ions of a working gas toward a plasma discharge region; at least partially neutralizing said ion beams before they enter the plasma discharge region; and supplying a heating current through the plasma discharge region, wherein the neutralized beams and the heating current form a hot plasma that radiates photons. 22. A method as defined in claim 21 wherein the step of electrostatically accelerating a plurality of beams of ions precedes the step of supplying a heating current through the plasma discharge region. claim 21 23. A method as defined in claim 21 wherein the step of supplying a heating current comprises supplying a pulsed heating current and wherein the step of electrostatically accelerating a plurality of beams of ions comprises accelerating a plurality of pulsed ion beams that precede the pulsed heating current. claim 21 24. A method as defined in claim 21 wherein the step of supplying a heating current comprises coupling the heating current to a spherical electrode array through a transformer. claim 21 25. A source of photons comprising: a discharge chamber; a plurality of ion beam sources in the discharge chamber, each electrostatically accelerating a beam of ions of a working gas toward a plasma discharge region; a neutralizing mechanism for at least partially neutralizing said ion beams before they enter the plasma discharge region; and an external electrode spaced from the plasma discharge region and biased with respect to the ion beam sources for delivering a heating current to the plasma discharge region, wherein the neutralized beams and the heating current form a hot plasma that radiates photons. 26. A source as defined in claim 25 wherein said ion beam sources comprise concentric electrode shells having sets of apertures aligned along axes which pass through the plasma discharge region, a first voltage source for applying a voltage between said electrode shells, and a gas source for supplying the working gas to the sets of apertures in said electrode shells. claim 25 27. A source as defined in claim 26 further comprising a second voltage source coupled between said ion beam sources and said external electrode for supplying said heating current. claim 26 28. A source as defined in claim 25 wherein said external electrode has a cylindrical configuration. claim 25 29. A source of photons comprising: a housing that defines a discharge chamber; a first group of ion beam sources directed toward a plasma discharge region in the discharge chamber, wherein a component of said first group of ion sources constitutes a first electrode; a second electrode spaced from the plasma discharge region; a first power supply for energizing the first group of ion beam sources to electrostatically accelerate, from the first group of ion beam sources toward the plasma discharge region, ion beams which are at least partially neutralized before they enter the plasma discharge region; and a second power supply coupled between the first and second electrodes for delivering a heating current to the plasma discharge region, wherein the ion beams and the heating current form a hot plasma that radiates photons. 30. A source of photons as defined in claim 29 , wherein the ion beam sources of said first group of ion beam sources are distributed around the plasma discharge region. claim 29 31. A source of photons as defined in claim 29 , further comprising a second group of ion beam sources directed toward the plasma discharge region, wherein a component of said second group of ion beam sources constitutes said second electrode. claim 29 32. A source of photons as defined in claim 31 , wherein said first and second groups of ion beam sources together comprise a spherical array of ion beam sources. claim 31 33. A source of photons as defined in claim 31 , wherein the ion beam sources of said first and second groups of ion beam sources are distributed around the plasma discharge region. claim 31 34. A source of photons as defined in claim 31 , wherein said first and second groups of ion beam sources comprise inner and outer electrode shells having sets of apertures aligned along axes which pass through the plasma discharge region, and wherein said first power supply is coupled between said inner and outer electrode shells. claim 31 35. A source of photons as defined in claim 34 , wherein said inner shell comprises a first inner shell portion and a second inner shell portion and wherein said second power supply is coupled between said first and second inner shell portions. claim 34 36. A source of photons as defined in claim 31 , wherein said first group of ion beam sources includes a first inner shell portion and said second group of ion beam sources includes a second inner shell portion, and wherein said second power supply is coupled between said first and second inner shell portions. claim 31 37. A source of photons as defined in claim 31 , wherein said first group of ion sources includes a first inner shell portion and said second group of ion sources includes a second inner shell portion, said source further comprising a transformer having a primary and a secondary, wherein said primary is coupled to said second power supply, wherein a first terminal of said secondary is coupled to said first inner shell portion and wherein a second terminal of said secondary is coupled to said second inner shell portion. claim 31 38. A source of photons as defined in claim 37 , wherein the secondary of said transformer has a single turn. claim 37 39. A source of photons as defined in claim 29 , wherein a photon beam is emitted from the plasma discharge region in a beam direction and wherein said second electrode is spaced from the plasma discharge region in a direction opposite the beam direction. claim 29 40. A source of photons as defined in claim 39 , wherein said first group of ion beam sources comprises inner and outer electrode shells having sets of apertures aligned along axes which pass through the plasma discharge region and wherein said second power supply is coupled between said inner electrode shell and said second electrode. claim 39 41. A source of photons as defined in claim 39 , wherein said second electrode comprises a ring. claim 39 42. A source of photons as defined in claim 39 , wherein said second electrode comprises a cathode for delivering a heating current to the plasma discharge region. claim 39 43. A source of photons as defined in claim 29 , wherein the ion beams precede the heating current. claim 29 44. A source of photons as defined in claim 29 , wherein the heating current is pulsed and wherein the ion beams comprise pulsed ion beams that precede the pulsed heating current. claim 29 45. A source of photons as defined in claim 29 , wherein the ion beams are continuous and wherein the heating current is pulsed. claim 29 46. A source of photons as defined in claim 29 , wherein the ion beams are at least partially neutralized by resonant charge exchange. claim 29 47. A source of photons as defined in claim 29 , wherein the radiated photons are in the soft X-ray or extreme ultraviolet wavelength range. claim 29 48. A source of photons as defined in claim 29 , wherein the ion beams comprise xenon ions and wherein the radiated photons have wavelengths in a range of about 10-15 nanometers. claim 29 49. A source of photons as defined in claim 29 , wherein the ion beams comprise ions of a working gas selected from the group consisting of xenon, hydrogen, lithium, helium, nitrogen, oxygen, neon, argon and krypton. claim 29 50. A source of photons as defined in claim 29 , wherein said first group of ion beam sources comprises a first hollow ring electrode and an inner shell that at least partially encloses the plasma discharge region. claim 29 51. A source of photons as defined in claim 50 , wherein said first power supply is connected between said first hollow ring electrode and said inner shell. claim 50 52. A source of photons as defined in claim 50 , further comprising a second group of ion sources, said second group of ion sources comprising a second hollow ring electrode and said inner shell. claim 50 53. A source of photons as defined in claim 52 , wherein said first power supply has a first terminal connected to said first and second hollow ring electrodes and a second terminal connected to said inner shell. claim 52 54. A source of photons as defined in claim 50 , wherein said first hollow ring electrode and said inner shell have a plurality of hole pairs which define plasma channels from the first hollow ring electrode to the plasma discharge region. claim 50 55. A source of photons as defined in claim 52 , wherein said first hollow ring electrode and said inner shell have a plurality of hole pairs which define plasma channels from the first hollow ring electrode to the plasma discharge region and wherein said second hollow ring electrode and said inner shell have a plurality of hole pairs which define plasma channels from the second hollow ring electrode to the plasma discharge region. claim 52 56. A source of photons as defined in claim 29 , wherein said second power supply is triggered to deliver a heating current about 0.1 to 10 microseconds after said first power supply is triggered to energize said first group of ion beam sources. claim 29 57. A source of photons as defined in claim 29 , further comprising a gas source for supplying a working gas to the discharge chamber, wherein the working gas is ionized to form the ion beams. claim 29 58. A source of photons as defined in claim 29 , wherein said first and second electrodes are configured such that the heating current is conducted along the ion beams to the plasma discharge region. claim 29 59. A source of photons comprising: means for accelerating a group of ion beams toward a plasma discharge region in a discharge chamber, wherein the ion beams are at least partially neutralized before they enter the plasma discharge region; and means for supplying a heating current to the plasma discharge region, wherein the ion beams and the heating current form a hot plasma that radiates photons. 60. A method for generating photons, comprising: accelerating a group of ion beams toward a plasma discharge region in a discharge chamber, wherein the ion beams are at least partially neutralized before they enter the plasma discharge region; and supplying a heating current to the plasma discharge region, wherein the ion beams and the heating current form a hot plasma that radiates photons. 61. A system for generating photons, comprising: a housing defining a discharge chamber; a first group of ion beam sources directed toward a plasma discharge region in the discharge chamber, wherein a component of said first group of ion sources constitutes a first electrode; a second electrode spaced from the plasma discharge region; a first power supply for energizing the first group of ion beam sources to accelerate, from the first group of ion beam sources toward the plasma discharge region, beams of ions of a working gas, wherein the ions are at least partially neutralized before they enter the plasma discharge region; a second power supply coupled between the first and second electrodes for delivering a heating current to the plasma discharge region; a gas source for supplying the working gas to the discharge chamber; and a vacuum system for controlling the pressure of the working gas in the discharge chamber.
	description	Referring now to the drawings, particularly of FIGS. 1 and 3, there is illustrated a container, generally designated 10, for shipping unclear fuel assemblies. Container 10 includes a container body 11 containing an interior metal box, not shown, in which a pair of fuel assemblies (also not shown), each including fuel rods and mechanical hardware, are disposed in side-by-side relation to one another. The inner metal box is confined within container 10. The top and sides of the container body 11 include panels 12 and 14, preferably formed of plywood, and a bottom 16 (FIG. 3). The top, bottom and sides are lined along the interior of container 10 by honeycomb structures 18 and foam pads 20 to confine the inner metal box within container 10. Container 10 also includes exterior structural wooden framing elements. For example, elongated wooden 2xc3x974s 22 and 24 are provided along the top and sides, respectively, of the container. Wooden planks 26 preferably form the bottom 16 of the container. Skids 27 (FIGS. 2 and 3) are also located below the container bottom to facilitate lifting the container, e.g., by a forklift. The ends of container 10 also include rectilinear end frames 29 (FIG. 3) formed of wooden framing elements. For example, each rectilinear end frame 29 is preferably formed of a pair of vertical wooden 2xc3x974s 30 spaced from one another and a pair of horizontal 2xc3x974s 32 forming the top and bottom framing elements of the wooden end frame. Additionally, a panel, for example, a plywood panel 34 is secured to the wooden end frame 29 along the inside end surface of the wooden elements 30 and 32. The construction of the container 10 as illustrated including the wooden framing elements, plywood panels, strapping, honeycomb and foam panels and wooden end frames is conventional except for the container end support system which will now be described. An end support system, generally designated 36, is applied in accordance with the present invention to the opposite ends of the container 10 to reinforce the container ends and to ensure sufficient structural integrity to meet the required drop tests of the licensing regulations. Referring to FIGS. 3 and 4, each end support system 36 comprises a metal end member or frame 38 including first and second metal plates 40 and 42 extending generally parallel to and spaced from one another. Each metal end frame 38 also includes third and fourth metal plates 44 and 46 which are generally parallel to and spaced from one another. Plates 44 and 46 are secured at their opposite ends to the metal plates 40 and 42. For example, the third plate 44 may be welded at its ends to the ends of the first and second plates 40 and 42, respectively. The fourth plate 46 may be welded to the opposite ends of the first and second plates 40 and 42, respectively, forming a generally rectilinear end frame lying in a plane. As illustrated, the plates 40 and 42 are horizontal for extending along the top of the container at its end face, while plates 44 and 46 are vertical for extending along the opposite sides of the container 10 at its end face. A metal crosspiece 48 also extends between the two side plates 44 and 46. The metal crosspiece 48 overlies the side plates 44 and 46 and is preferably welded thereto. A reinforcing member 50, preferably in the form of a channel, is secured along the inside face of crosspiece 48 and terminates short of the ends of crosspiece 46, for purposes described hereafter. Metal supports extend in a generally perpendicular direction to said metal end frame for securing said metal end frame to said container end. At least two supports extend along opposite sides of container 10 for this purpose and, preferably, each such support comprises a pair of support arms. For example, four support arms 52, 54, 56 and 58 extend from the corners of the metal end frame 36 in a direction generally perpendicular to the plane of the end support frame. The arms comprise metal plates for extending along the sides of the container 10 in overlying relation to the wooden framing elements forming the sides of container 10. The arms lie in planes parallel to the container sides. As illustrated in FIG. 4, the metal plates 40, 42, 44 and 46 and arms 52, 54, 56 and 58 have a plurality of preformed holes, for example, holes 60, for receiving screws to screw the end support system 36 to the wooden end frames 24, 26, 29, 30 and 32 of the wooden container 10 as illustrated in FIG. 3. To apply an end support system 36 to an end of the container 10, the system 36 is disposed on the container end with the plates 40 and 42 overlying the wooden top and bottom framing elements 32 and plates 44 and 46 overlying the wooden side framing elements 30. The arms 52, 54, 56 and 58 extend along opposite sides of the container overlying portions of the elongated wooden framing elements 16 and 24. Note (in FIG. 2) that the upper edge of the end support assembly 36, i.e., the metal plate 40, lies below the cover for the outer container 10. Additionally, it will be appreciated that the arms 52, 54, 56 and 58 straddle the sides of container 10. With the end support assembly 36 applied to the end of the container, a series of screws are passed through the openings 60 of the metal end support 36 to secure it to the container end. The screws are preferably flathead 8xc3x9780 mm screws with ribs under the screw head. It will be appreciated that the screw openings 60, as illustrated in FIG. 4, along arms 52, 54, 56 and 58, are formed in an alternating pattern of a pair of openings followed by a single opening along the lengths of the arms. This minimizes any tendency to split the wooden framing elements and affords a securement to the wood. Upon review of FIG. 2, it will be appreciated that, in final securement, the reinforcing member 50, i.e., the channel, is disposed between the wooden side framing elements 30 with its opposite ends butting against the inside edges of framing elements 30 to reinforce elements 30. Additionally, the channel has a depth, in the longitudinally direction of the container, the bear against the end panel 34. The channel thus affords reinforcement to both the side wooden framing elements 30 and to the panel 34. Because of the structural relationship of the plates, crosspeice and arms and the plurality of metal screws used to secure the plates and arms of the metal end frame to the end of the container, structural integrity of the end of the container is maintained and assured within the requirements of the drop tests mandated by nuclear regulatory licensing requirements. As illustrated, container 10 not only has the end support assemblies at opposite ends but is banded, e.g., by bands 28, at longitudinally spaced intervals which also assists in maintaining the integrity of the outer container. While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
048511854	abstract	Method and apparatus for shielding an otherwise exposed upper portion of a radioactive reactor component disposed in a refueling pool of water having a depth less than the height of the component. A vessel with a top end wall, a side wall larger than the transverse size of the component is disposed over the exposed upper portion until the lower rim thereof is immersed in the pool and the top end wall and the side wall are in spaced relation to the upper portion of the component. Fluid, mainly air, is evacuated from the vessel to cause water from the pool to enter the vessel and provide a water level therein which is above the water level in the pool and between the component and the walls of the vessel. The vessel is reinforced to withstand the pressures caused by removal of fluid therefrom and is suspended by beams and legs, the latter being engageable with the pool walls. The fluid is evacuated by a pump controlled by a level detector responsive to the water level in the vessel to maintain the desired latter water level.
	claims	1. A molten fuel nuclear reactor comprising:a containment vessel and vessel head;a reactor core enclosed within the containment vessel and vessel head, the reactor core having an upper region and a lower region;a heat exchanger enclosed within the containment vessel and vessel head, the heat exchanger fluidly connected to the upper region of the reactor core by an upper channel and fluidly connected to the lower region of the reactor core by a lower channel, the reactor core, heat exchanger and upper and lower channels forming a fuel loop;a reflector defining the lateral extent of the reactor core, the reflector adjacent to the heat exchanger and separating the reactor core from the heat exchanger, wherein the upper channel is above the reflector and the lower channel is below the reflector; andan impeller enclosed within the containment vessel and vessel head, the impeller attached to a shaft that is rotatable by a motor located outside of the containment vessel and vessel head;wherein the impeller is located within the fuel loop such that the impeller, when rotated by the motor, circulates fluid through the fuel loop;wherein the reflector has a top defined by the upper channel and a bottom defined by the lower channel and the impeller is located below the top of the reflector and above the heat exchanger. 2. The molten fuel nuclear reactor of claim 1, wherein the shaft penetrates the vessel head and rotatably connects the impeller to a motor located above the vessel head. 3. The molten fuel nuclear reactor of claim 1, wherein the impeller is located in the upper channel. 4. The molten fuel nuclear reactor of claim 1, wherein the heat exchanger is one of a plurality of independent heat exchangers enclosed within the containment vessel and vessel head. 5. The molten fuel nuclear reactor of claim 4, wherein each independent heat exchanger in the plurality is provided with an impeller. 6. The molten fuel nuclear reactor of claim 1, wherein the heat exchanger is selected from a shell and tube heat exchanger, a plate heat exchanger, a plate and shell heat exchanger, a printed circuit heat exchanger, and a plate fin heat exchanger. 7. The molten fuel nuclear reactor of claim 6, wherein the heat exchanger is a shell and tube heat exchanger having a plurality of tubes within a shell in which the fluid circulating through the fuel loop passes through the plurality of tubes and a coolant passes through the shell. 8. The molten fuel nuclear reactor of claim 1, wherein the heat exchanger is located below the impeller and above the bottom of the reflector. 9. The molten fuel nuclear reactor of claim 1, wherein the heat exchanger has a coolant inlet opposite the reflector and a coolant outlet opposite the reflector. 10. The molten fuel nuclear reactor of claim 1, wherein the reflector is adjacent to the impeller and separates the reactor core from the impeller. 11. A molten fuel nuclear reactor comprising:a containment vessel and vessel head;a reactor core enclosed within the containment vessel and vessel head, the reactor core having an upper region and a lower region;a heat exchanger enclosed within the containment vessel and vessel head, the heat exchanger fluidly connected to the upper region of the reactor core by an upper channel and fluidly connected to the lower region of the reactor core by a lower channel, the reactor core, heat exchanger and upper and lower channels forming a fuel loop;a reflector defining the lateral extent of the reactor core, the reflector adjacent to the heat exchanger and separating the reactor core from the heat exchanger, wherein the upper channel is above the reflector and the lower channel is below the reflector; andan impeller enclosed within the containment vessel and vessel head, the impeller attached to a shaft that is rotatable by a motor located outside of the containment vessel and vessel head;wherein the impeller is located within the fuel loop such that the impeller, when rotated by the motor, circulates fluid through the fuel loop;wherein the reflector has a top defined by the upper channel and a bottom defined by the lower channel and the impeller is located below the top of the reflector and above the heat exchanger and the heat exchanger is located below the impeller and above the bottom of the reflector. 12. The molten fuel nuclear reactor of claim 11, wherein the shaft penetrates the vessel head and rotatably connects the impeller to a motor located above the vessel head. 13. The molten fuel nuclear reactor of claim 11, wherein the impeller is located in the upper channel. 14. The molten fuel nuclear reactor of claim 11, wherein the heat exchanger is one of a plurality of independent heat exchangers enclosed within the containment vessel and vessel head. 15. The molten fuel nuclear reactor of claim 11, wherein the heat exchanger is selected from a shell and tube heat exchanger, a plate heat exchanger, a plate and shell heat exchanger, a printed circuit heat exchanger, and a plate fin heat exchanger. 16. The molten fuel nuclear reactor of claim 15, wherein the heat exchanger is a shell and tube heat exchanger having a plurality of tubes within a shell in which the fluid circulating through the fuel loop passes through the plurality of tubes and a coolant passes through the shell. 17. The molten fuel nuclear reactor of claim 11, wherein the heat exchanger has a coolant inlet opposite the reflector and a coolant outlet opposite the reflector. 18. The molten fuel nuclear reactor of claim 11, wherein the reflector is adjacent to the impeller and separates the reactor core from the impeller.
	description	This application claims the benefit of Chinese Patent Application No. 201010586774.9 filed Dec. 9, 2010, which is hereby incorporated by reference in its entirety. The invention generally relates to the field of an X-ray machine, and in particular relates to a linkage mechanism of a scattered ray inhibition apparatus and a radiation field control apparatus, a collimator, and an X-ray machine. In the field of the X-ray machine, a radiation field control apparatus exists in a collimator for limiting the X-ray Field of View (FOV) of X-rays emitted from a tube, and it is generally composed of two rectangular blades that are oppositely disposed. As is well-known, there is a certain distance between the tube and the collimator, thus a part of the X-rays emitted from the tube will be scattered from the distance, which also may be called off-focal radiation. For a general X-ray machine, the amount of the off-focal radiation thereof normally approaches 15% of the amount of the focal radiation. In addition to the primary X-ray beams, the part of off-focal radiation also will radiate on a patient, which thus increases X-ray dosage to the patient and also affects the quality of imaging, and also makes faint images of the anatomical structures outside the field of interest. Therefore, in order to solve the problem, a scattered ray inhibition apparatus is generally disposed over the distance between the tube and the collimator for inhibiting the X-rays emitted from the tube from being scattered from the distance. The scattered ray inhibition apparatus usually employs a fixed blade disposed in a plane which is as close as possible to the exit of the tube, or a fixed cone. For an X-ray machine, the tube emits cone-shaped X-ray beams, when the FOV changes, the scattered ray inhibition apparatus remains unchanged, thus, in the case of a small FOV, the quality of imaging is rather undesirable. Hence, the scattered ray inhibition apparatus needs to be in linkage with the radiation field control apparatus. At present, at least some known X-ray machines have had the function of linking the scattered ray inhibition apparatus with the radiation field control apparatus. However, they generally have a wheel disc and a shift lever mounted between the scattered ray inhibition apparatus and the radiation field control Apparatus. One end of the shift lever is connected to the radiation field control apparatus while the other end thereof is connected to one end of the wheel disc, and the other end of the wheel disc is connected to one end of the blade (the scattered ray inhibition apparatus). Thus, as the radiation field control apparatus changes, the shift lever drives the wheel disc, the wheel disc further drives the blade, causing the blade to swing. Hence, the inhibition effect in such manner is undesirable and the structure is comparatively complicated. Since the tube of the X-ray machine emits cone-shaped radiation beams, if the blade or the cone is able to translate with the motion of the radiation field control apparatus, the achieved inhibition effect is then ideal. U.S. Pat. No. 4,246,288 also discloses a method of linking a scattered ray inhibition apparatus with a radiation field control apparatus, but the method is complicated in structure. The embodiments described herein provide a linkage mechanism of a scattered ray inhibition apparatus and an radiation field control apparatus, a collimator, and an X-ray machine that may reduce influence of off-focal radiation upon a patient. The linkage mechanism of the scattered ray inhibition apparatus and the radiation field control apparatus described herein includes a first timing belt, a second timing belt and a transmission mechanism between the first timing belt and the second timing belt, wherein, the scattered ray inhibition apparatus is mounted on the first timing belt, the radiation field control apparatus is mounted on the second timing belt, the transmission ratio of the transmission mechanism is equal to the ratio of the moving speed of the scattered ray inhibition apparatus to the moving speed of the radiation field control apparatus. In one embodiment, the transmission mechanism comprises at least two gears. In one embodiment, the transmission mechanism further includes a third timing belt connected to the first timing belt and a fourth timing belt connected to the second timing belt, wherein the at least two gears are disposed between the third timing belt and the fourth timing belt. In one embodiment, the linkage mechanism of the scattered ray inhibition apparatus and the radiation field control apparatus further includes a first linear guideway, the scattered ray inhibition apparatus is connected to the first timing belt through the first linear guideway. Further, the linkage mechanism of the scattered ray inhibition apparatus and the radiation field control apparatus further includes a second linear guideway, the radiation field control apparatus is connected to the second timing belt through the second linear guideway. Further, the linkage mechanism of the scattered ray inhibition apparatus and the radiation field control apparatus further includes an electrical motor for supplying power to the transmission mechanism. In another aspect, the collimator of the includes a linkage mechanism of a scattered ray inhibition apparatus and a radiation field control apparatus, the linkage mechanism includes a first timing belt, a second timing belt and a transmission mechanism between the first timing belt and the second timing belt, wherein the scattered ray inhibition apparatus is mounted on the first timing belt, the radiation field control apparatus is mounted on the second timing belt, the transmission ratio of the transmission mechanism is equal to the ratio of the moving speed of the scattered ray inhibition apparatus to the moving speed of the radiation field control apparatus. In one embodiment, the transmission mechanism includes at least two gears. In one embodiment, the transmission mechanism further includes a third timing belt connected to the first timing belt and a fourth timing belt connected to the second timing belt, wherein, the at least two gears are disposed between the third timing belt and the fourth timing belt. Further, in one embodiment, the transmission mechanism further includes a first linear guideway, and the scattered ray inhibition apparatus is connected to the first timing belt through the first linear guideway. Further, in one embodiment, the transmission mechanism further includes a second linear guideway, the radiation field control apparatus is connected to the second timing belt through the second linear guideway. In another aspect, an X-ray machine includes a linkage mechanism of a scattered ray inhibition apparatus and a radiation field control apparatus, the linkage mechanism includes a first timing belt, a second timing belt and a transmission mechanism between the first timing belt and the second timing belt, wherein the scattered ray inhibition apparatus is mounted on the first timing belt, the radiation field control apparatus is mounted on the second timing belt, the transmission ratio of the transmission mechanism is equal to the ratio of the moving speed of the scattered ray inhibition apparatus to the moving speed of the radiation field control apparatus. In one embodiment, the transmission mechanism includes at least two gears. In one embodiment, the transmission mechanism further includes a third timing belt connected to the first timing belt and a fourth timing belt connected to the second timing belt, wherein the at least two gears are disposed between the third timing belt and the fourth timing belt. Further, the transmission mechanism further includes a first linear guideway, the scattered ray inhibition apparatus is connected to the first timing belt through the first linear guideway. Further, the transmission mechanism further includes a second linear guideway, the radiation field control apparatus is connected to the second timing belt through the second linear guideway. Compared to the prior art, the linkage mechanism of the scattered ray inhibition apparatus and the radiation field control apparatus and the X-ray machine have several advantages. Since the embodiments described herein include a scattered ray inhibition apparatus mounted on the first timing belt, the scattered ray inhibition apparatus may translate, which thus may ensure a reduction of influence of off-focal radiation upon human bodies. Since the transmission ratio of the transmission mechanism is equal to the ratio of the moving speed of the scattered ray inhibition apparatus to the moving speed of the radiation field control apparatus, as such, it may ensure the linkage of the scattered ray inhibition apparatus with the radiation field control apparatus. Moreover, the structure of the embodiments described herein is simple, reliable and easy to realize. Specific embodiments will be described in detail below, however, the invention is not limited to the following specific embodiments stated. As shown in FIG. 1, a linkage mechanism of a scattered ray inhibition apparatus and a radiation field control apparatus includes a first timing belt 1, a second timing belt 2 and a transmission mechanism 3 between the first timing belt 1 and the second timing belt 2, wherein the scattered ray inhibition apparatus 10 (see FIG. 2) is mounted on the first timing belt 1, the radiation field control apparatus 11 (see FIG. 2) is mounted on the second timing belt 2, the transmission ratio of the transmission mechanism 3 is equal to the ratio of the moving speed of the scattered ray inhibition apparatus 10 to the moving speed of the radiation field control apparatus 11. When the FOV changes, that is, when the radiation field control apparatus 11 moves, the scattered ray inhibition apparatus 10 also should move, thus linkage may be realized. For a particular X-ray machine, the ratio of the moving speed of the scattered ray inhibition apparatus 10 to the moving speed of the radiation field control apparatus 11 is determined. As shown in FIG. 3, it illustrates a schematic diagram of the relation of speed between the scattered ray inhibition apparatus and the radiation field control apparatus.Since V0=((d2−d1)/2)/T; V2=((D2−D1)/2)/T; wherein, V0 indicates the moving speed of the scattered ray inhibition apparatus 10, V2 indicates the moving speed of the radiation field control apparatus, T indicates the moving time for the scattered ray inhibition apparatus 10 and the radiation field control apparatus 11 to move from the largest opening to the smallest opening, d1 indicates the minimum distance between the two blades when the scattered ray inhibition apparatus has the smallest opening, d2 indicates the minimum distance between the two blades when the scattered ray inhibition apparatus has the largest opening, D1 indicates the minimum distance between the two blades when the radiation field control apparatus has the smallest opening, D2 indicates the minimum distance between the two blades when the radiation field control apparatus has the largest opening. Therefore the ratio may be obtained through the following formula:V0/V2=(d2−d1)/(D2−D1) As shown in FIG. 2, the linkage mechanism further may include a first linear guideway 12, the scattered ray inhibition apparatus 10 is connected to the first timing belt 1 through the first linear guideway 12. Additionally, the linkage mechanism further may include a second linear guideway 13, the radiation field control apparatus 11 is connected to the second timing belt 2 through the second linear guideway 13. Again as shown in FIG. 2, the linkage mechanism further may include an electrical motor 9 for supplying power to the transmission mechanism 3. The electrical motor 9 may be mounted on the gear shaft of gear 7 and gear 6 (see FIG. 2), and also may be mounted in positions of other gears or timing belt pulleys. As for the transmission mechanism 3, it may be designed in any method that has been known or may be known by those skilled in the art in the future, as long as the transmission ratio of the transmission mechanism 3 is equal to the ratio of the moving speed of the scattered ray inhibition apparatus 10 to the moving speed of the radiation field control apparatus 11. For example, the transmission mechanism 3 may only include two gears, the transmission ratio of the two gears is the ratio of the moving speed of the scattered ray inhibition apparatus 10 to the moving speed of the radiation field control apparatus 11. Of course, the transmission mechanism 3 also may include more than two gears. FIG. 4 illustrates a schematic diagram of one embodiment of a linkage mechanism of a scattered ray inhibition apparatus and a radiation field control apparatus. The transmission mechanism 3 may include a third timing belt 4 connected to the first timing belt 1, a fourth timing belt 5 connected to the second timing belt 2, and a first gear 6 and a second gear 7 disposed between the third timing belt 4 and the fourth timing belt 5 for implementing transmission. In the example, the radiuses of timing belt pulleys of the first timing belt 1, the second timing belt 2 and the third timing belt 4 are all set to be R1, the radius of one timing belt pulley of the fourth timing belt 5 is R1, and the radius of the other timing belt pulley thereof is R3, and the radius of the first gear 6 is set to be R2, the radius of the second gear 7 is set to be R1, V0 indicates the moving speed of the scattered ray inhibition apparatus 10, V2 indicates the moving speed of the radiation field control apparatus 11, I0 indicates the transmission ratio of the electrical motor 9 to the second gear 7, I1 indicates the transmission ratio of the larger pulley of the fourth timing belt 5 to the timing belt pulley of the third timing belt 4, wherein,I0=R2/R1I1=R3/R1V2=I0I1V0=((R2R3)/(R1R1))V0 V2/V0=(R2R3)/(R1R1) For a particular X-ray machine, V2/V0 is constant. As for this embodiment, the value thereof is 6, thus,(R2R3)/(R1*R1)=6 (1) Therefore, in one example, for the values of R1, R2 and R3 satisfy the formula (I), e.g., R1 is 7, R2 is 21, R3 is 14 (length unit). In another aspect, collimator is provided that includes a linkage mechanism of a scattered ray inhibition apparatus and a radiation field control apparatus, the linkage mechanism including a first timing belt 1, a second timing belt 2 and a transmission mechanism 3 between the first timing belt 1 and the second timing belt 2, wherein the scattered ray inhibition apparatus 10 is mounted on the first timing belt 1, the radiation field control apparatus 11 is mounted on the second timing belt 2, the transmission ratio of the transmission mechanism 3 is equal to the ratio of the moving speed of the scattered ray inhibition apparatus 10 to the moving speed of the radiation field control apparatus 11. In one embodiment, the transmission mechanism 3 includes at least two gears, the total transmission ratio between the gears is the ratio of the moving speed of the scattered ray inhibition apparatus 10 to the moving speed of the radiation field control apparatus 11. According to one embodiment, the transmission mechanism 3 may include a third timing belt 4 connected to the first timing belt 1, a fourth timing belt 5 connected to the second timing belt 2 and at least two gears between the third timing belt 4 and the fourth timing belt 5 for implementing transmission. Again as shown in FIG. 2, the transmission mechanism 3 of the collimator further includes a first linear guideway 12, the scattered ray inhibition apparatus 10 is connected to the first timing belt 1 through the first linear guideway 12. Further, the transmission mechanism 3 of the collimator further includes a second linear guideway 13, the radiation field control apparatus 11 is connected to the second timing belt 2 through the second linear guideway 13. In addition, the transmission mechanism 3 of the collimator further includes an electrical motor 9 for supplying power to the transmission mechanism 3. An X-ray machine is provided, which includes a linkage mechanism of a scattered ray inhibition apparatus and a radiation field control apparatus, the linkage mechanism includes a first timing belt 1, a second timing belt 2 and a transmission mechanism 3 between the first timing belt 1 and the second timing belt 2, wherein the scattered ray inhibition apparatus 10 is mounted on the first timing belt 1, the radiation field control apparatus 11 is mounted on the second timing belt 2, the transmission ratio of the transmission mechanism 3 is equal to the ratio of the moving speed of the scattered ray inhibition apparatus 10 to the moving speed of the radiation field control apparatus 11. In one example, the transmission mechanism 3 may include two gears, the ratio of diameters of the two gears is the ratio of the moving speed of the scattered ray inhibition apparatus 10 to the moving speed of the radiation field control apparatus 11. In another example, the transmission mechanism 3 includes a third timing belt 4 connected to the first timing belt 1, a fourth timing belt 5 connected to the second timing belt 2, and a first gear 6 and a second gear 7 disposed between the third timing belt 4 and the fourth timing belt 5 for implementing transmission. In one embodiment, the X-ray machine further includes a first linear guideway 12, the scattered ray inhibition apparatus 10 is connected to the first timing belt 1 through the first linear guideway 12. Further, the X-ray machine further may include a second linear guideway 13, the radiation field control apparatus 11 is connected to the second timing belt 2 through the second linear guideway 13. In addition, the X-ray machine further includes an electrical motor 9 for supplying power to the transmission mechanism 3. Because the linkage mechanism in the collimator and the linkage mechanism in the X-ray machine described herein are similar to the linkage mechanism of a scattered ray inhibition apparatus and a radiation field control apparatus described herein, the linkage mechanism in the collimator and the linkage mechanism in the X-ray machine will not be described in detail herein. Although the embodiments of the present invention are described as above in combination with the figures, those skilled in the art may implement various variation, modification and equivalent substitution to the invention without departing from the spirit and scope of the present invention. Such variation, modification and equivalent substitution are all intended to fall within the spirit and scope defined by the appended claims.
054886430	abstract	In order to eliminate the need to weld, drill or otherwise machine a shroud structure which is used to surround a plurality of fuel assemblies in a nuclear reactor, a plurality of upper hanger rods interconnect a structure above the shroud to a support ring which is clamped about the upper periphery of the shroud. Lower hanger rods interconnect a lower edge or shoulder portion of the shroud with the support ring. Thus, through the upper and lower hanger rods and the support ring, the shroud can be supported within the RPV. The upper support ring is arranged to clamp the lower ends of the upper hanger rods against the upper outer peripheral portion of the shroud while the lower ends of the lower hanger rods are clamped against the lower peripheral wall portion of the shroud by a lower support ring.
042016258	abstract	A target containing vanadium, either of natural isotopic constitution or enriched either with respect to .sup.50 vanadium or .sup.51 vanadium, is bombarded with .sup.3 helium of an energy of about 14 MeV producing .sup.52 manganese by nuclear reaction from both of these isotopes of vanadium. After a waiting period for the disappearance of short-lived intermediates, the target foil is dissolved in acid and the .sup.52 manganese is extracted with a solution of a hydroxychinolin in chloroform. The oxinate complex of .sup.52 manganese thus extracted can be used directly as a source of .sup.52 manganese in the preparation of compositions for radiochemical or radiopharaceutical purposes.
045434883	summary	The present invention relates to an exchangeable basket for a container for the transportation and/or storage of spent nuclear fuel elements. The basket serves as a storage support for the fuel elements disposed in the container and comprises compartments which are shaped to closely conform to the exterior dimensions of the fuel elements. An insertion or storage basket is normally required when spent nuclear fuel is transported or stored in a container in order to simultaneously provide for receiving spent nuclear fuel elements and maintaining them in a desired position in the container for during transportation and also during storage. The respective necessary fuel element positions are formed as compartments in the basket into which the fuel elements are inserted. Each compartment's cross-section is designed in shape and dimensions according to the type of fuel element to be inserted so that the fuel elements can be inserted and removed without difficulty by remote control apparatus. The insertion or storage basket must be sufficiently stable that it can withstand the mechanical and thermal loads experienced during transportation. Also, the containers must be so constructed that the fuel elements to be conveyed will not be damaged during transportation and subsequent handling. In the prior art, such baskets are normally constructed as pure steel supports or, as massive blocks of non-ferrous metal. The compartments of the blocks are produced mechanically and in some cases they are steel clad. Steel frameworks are suitable as storage baskets if there is located in the baskets a corresponding liquid which can carry off from the container walls the residual heat produced from the fuel elements. The steel framework can consist of boron steel wherein the boron serves as a neutron absorber. The massive, non-ferrous constructions having compartments are suitable as storage baskets since they make it possible to draw off the residual heat produced since such material is a good heat conductor and does not require an additional heat transfer medium. Preferably, they consist of aluminum, copper or an alloy thereof. These alloys likewise can include boron or cadmium to act as neutron absorbers. Also the following materials are usable: cast iron, brass, bronze, lead, magnesium, uranium, concrete, argillaceous earth, ceramic, wood, carbon, resin. However, in the previously known storage containers, there have been a number of disadvantages. While the steel frames are stable at the high temperatures involved, they exhibit poor heat conducting properties. On the other hand, the block-type frames, at high temperatures, have low tensile strength but still have good heat conducting properties. Also, the production of these types of baskets has been very expensive since the demands on the compartments are very high in terms of the tolerances, grade of materials used and the surface qualities demanded. It is an object of the present invention to provide a storage basket for containers for transporting and/or storing spent nuclear fuel elements which combine the tensile strength of the steel frames with the good heat conductivity of the block-type frames made of non-ferrous metals. As a result, an insertion basket can be formed which resists both the mechanical and thermal stresses encountered and which makes good use of the heat conductivity of the material to remove the residual heat. SUMMARY OF THE INVENTION According to the present invention, there is provided a storage basket wherein appropriately shaped steel tubes are embedded with connecting elements in a casting of a good heat conductor such as a non-ferrous metal or a non-ferrous alloy. The manufacture is carried out in such a manner that the stainless steel tubes having circular or angular cross-sections are connected by connecting elements in a framework and then the framework and tubes are surrounded by casting with a non-ferrous metal. Preferably aluminum, copper or their alloys is used. The steel and non-ferrous metals can, if it is necessary, be provided with neutron absorbers. The present invention has the advantage that the steel framework, can be supported at the inner wall of the container. This concept insures great mechanical strength at high temperature. The non-ferrous metal block, being a good heat conductor, solves the problem of dealing with the residual heat of the spent fuel elements. Also, in the manufacture, the heat treatment of the inner surfaces of the steel tubes, the centering and the exact alignment of the tubular compartments, all can be carried out before the casting is effected. This is of a special significance if the cross-sections of the compartments are not circular. By pouring in the cast material, any gap formation is avoided between the compartments and the block which would result in poor heat transfer. The heat transfer by radiation from the fuel elements to the lodgements of the basket is substantially better for steel inserts than for non-ferrous untreated materials such as aluminum.
	summary
	abstract	A head assembly for a reactor pressure vessel includes a removable closure head, an array of control rod drive mechanisms, a seismic support platform, a missile shield assembly and a cooling system for drawing atmospheric air across electromagnetic coil stack assemblies. The cooling system includes: a lower shroud surrounding the coil stack assemblies with an end open to the atmosphere around the CRDMs; a plurality of extending internal ducts disposed within the array of CRDMs upwardly to an upper plenum disposed above the seismic support platform and a plurality of fan assemblies disposed on the upper plenum. The missile shield is disposed within the upper plenum. The cooling system effectively cools the coil stack assemblies during fuel cycles and does not hinder access to the CRDMs during an outage. The head assembly has lift legs for transporting either the entire head assembly as an integral unit or the structure above the seismic support platform a subassembly.
	abstract	One or more techniques or systems for incorporating a common template into a system on chip (SOC) design are provided herein. For example, a common template mask set is generated based on a first set of polygon positions from a first vendor and a second set of polygon positions from a second vendor. A third party creates a third party SOC design using a set of design rules generated based on the common template mask set. The common template is fabricated based on the third party SOC design using the common template mask set. Because the common template is formed using the common template mask set and because the common template mask set is based on polygon positions from both the first vendor and the second vendor, a part can be connected to the SOC regardless of whether the part is sourced from the first vendor or the second vendor.
	abstract	A standard component for length measurement includes a first diffraction grating and a second diffraction grating. Each of components of the second diffraction grating is disposed between components of the first diffraction grating.
	description	This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2010-276188, filed on Dec. 10, 2010, the entire content of which is incorporated herein by reference. Embodiments described herein relate generally to a jet pump measurement pipe repair method for repairing a measurement pipe provided in a diffuser of a jet pump in a boiling water reactor. A conventional boiling water reactor adopts a so-called jet pump system obtained by combining recirculation pumps installed outside a reactor pressure vessel and jet pumps installed inside the reactor pressure vessel for the purpose of increasing power density. As illustrated in FIG. 13, a plurality of jet pumps 4 are arranged at equal intervals in the circumferential direction between a rector pressure vessel 1 and a shroud 2 which are vertically installed in a downcomer part 3. As illustrated in FIG. 14 which is an enlarged view of the main part of FIG. 13, the jet pumps 4 each have a riser pipe 5. The riser pipe 5 is fixed to the rector pressure vessel 1 and introduces coolant supplied from a recirculation inlet nozzle 6 of a recirculation pump into the reactor pressure vessel. A pair of elbows 7A and 7B are connected respectively to the upper part of the riser pipe 5 through a transition piece 14. A pair of inlet throats 9A and 9B are connected respectively to the pair of elbows 7A and 7B through a pair of mixing nozzles 8A and 8B. Diffusers 10A and 10B are connected respectively to the pair of inlet throats 9A and 9B. In the following description, the inlet throats 9A, 9B and diffusers 10A, 10B are collectively referred to as “inlet throat 9” and “diffuser 10” when they are not differentiated. Measurement of the flow rate of the jet pumps 4 during normal operation is important for power control of a nuclear power plant. To this end, measurement pipes 11 are provided at the upper and lower parts of each of the diffusers 10A and 10B. The measurement pipes 11 are used to measure the difference in the static pressure between the upper and lower parts of the diffuser 10 during operation, and the obtained measurement value is calibrated with a calibration value that has previously been measured before the use of the plant, whereby the flow rate of the jet pumps 4 are calculated. Each of the measurement pipes 11 is welded to static pressure holes formed at the upper and lower parts of the diffuser 10 and is welded to be supported by blocks 12 and a support 13 (FIG. 15) which are supporting members fixed to the diffuser 10. As illustrated in FIGS. 16A and 16B, the measurement pipes 11 are arranged in the lower part of the jet pumps 4 in a complicated manner and are connected to pipes outside the reactor through jet pump measurement nozzles 15. The jet pump measurement nozzles 15 are provided at two symmetrical positions in a horizontal cross-section of the reactor pressure vessel 1. The jet pumps 4 having the configuration described above are exposed to more severe conditions than other equipment because of a high temperature of about 300° C. and flow of a high speed/large flow rate cooling water pumped from a not-illustrated recirculation pumps. Therefore, a large load is applied to each of the members of the jet pumps 4. Especially, the measurement pipes 11 is subject to sever stress as they are affected, either directly or through the blocks 12 and the supports 13, by the fluid vibration generated by the flow of the high speed/large flow rate cooling water of the diffuser 10 pumped from the recirculation pumps. As a result, several pipe breakages have occurred so far. Such a breakage of the measurement pipes 11 makes it impossible to measure the flow rate of the jet pumps 4, posing a problem for the power control of the reactor, so that repair work must be conducted quickly. As illustrated in FIG. 16B, the measurement pipes 11 are arranged in a narrow annular space 16 between the reactor pressure vessel 1 and the shroud 2. The riser pipes 5, inlet throats 9, and the like are arranged above the measurement pipes 11 as illustrated in FIG. 14. The horizontally extending part (FIG. 15) of the measurement pipe 11 near the supports 13 is closest to the shroud 2, and the interval between the measurement pipe 11 and the shroud 2 at this part is as small as less than 150 mm. Further, the intermediate body part of the shroud 2 overhangs the horizontally extending part of the measurement pipe 11. This limits much the shape and size of a repair tool for the measurement pipe 11 and a repair method applied to the measurement pipe 11, making the repair work difficult to carry out. In addition, the site around the measurement pipes 11 are high-radiation area, so that it is very difficult for workers to access the part to be repaired. Therefore, that under present circumstance, there is no alternative way but to remotely carry out the repair work for the measurement pipes 11 from just above the reactor core underwater. As an example of the repair method for the measurement pipe 11 having the above configuration, there are known a method using a welding machine in an environment obtained by draining reactor water and a method using an underwater laser welding machine (refer to, e.g., Patent Document 1: Japanese Patent No. 4,298,527 and Patent Document 2: Japanese Patent Application Laid-Open Publication No. 2004-209515, the entire contents of which are incorporated herein by reference). Most breakage events in the measurement pipes 11 described above occur at the welded parts between the measurement pipes 11 and the blocks 12, and there have been proposed only several repair methods that target only the measurement pipes 11 arranged in the vertical direction of the jet pumps 4. Further, as illustrated in FIGS. 14 and 15, the installation position of the horizontally extending part of the measurement pipes 11 are so narrow that it is difficult to carry out the repair work for this part with the approaches disclosed in Patent Documents 1 and 2. Furthermore, underwater remote repair work is essential for the horizontally extending part of the measurement pipes 11 due to difficulty in the repair work for positional reasons as described above and further due to the requirement of shortening of the repair process time. Thus, establishment of a repair method that is carried out remotely and underwater has been required for the breakage of the horizontally extending part of the measurement pipes 11. The present invention has been made in view of the above situation, and an object thereof is to provide a jet pump measurement pipe repair method capable of coping with a breakage event occurring at the lower part of a jet pump at which a measurement pipe extends in the horizontal direction underwater. According to one embodiment, a jet pump measurement pipe repair method repairs a breakage part of a measurement pipe horizontally fixed to a lower part of a jet pump provided in reactor water in a reactor pressure vessel. The method includes a cutting/removing step of cutting and removing the measurement pipe including the breakage part; a retaining step of retaining a connection pipe for connecting a remaining measurement pipe on the jet pump by means of a clamp; and a connecting step of connecting ends of the remaining measurement pipe by means of the connection pipe. Embodiments of a jet pump measurement pipe repair method according to the present invention will be described below with reference to the accompanying drawings. In the following embodiments, the same reference numerals are given to the same parts as those in FIGS. 13 to 16. Further, in the following embodiments, a case where a breakage has occurred in the measurement pipe 11 which is horizontally fixed to the diffuser 10 of the jet pump 4 provided in the reactor water in the vertically installed reactor pressure vessel 1 and repair is applied to the breakage part will be described. FIG. 1 is a flowchart illustrating a first embodiment of the jet pump measurement pipe repair method according to the present invention. This flowchart is a repair process flowchart applied upon occurrence of a breakage of the horizontal part of the measurement pipe 11. As illustrated in FIG. 1, the repair method according to the present embodiment roughly includes step S1 of cutting off and removing the measurement pipe 11 and the support 13, step S2 of attaching a clamp, and step S3 of connecting the measurement pipe 11. Next, a cut-away device used in step S1 will be described. FIG. 2 is a perspective view schematically illustrating a cut-away device used in the first embodiment and the measurement pipe whose horizontal part has been broken. FIG. 3A is a side view illustrating the pipe breakage part side of a cut-away device used in the first embodiment. FIG. 3B is a front view of a cutting section of the cut-away device used in the first embodiment. FIG. 3C is a front view of a gripping tool of the cut-away device used in the first embodiment. FIG. 4A is a side view of another cut-away device used in the first embodiment as viewed from the opposite side of the pipe breakage part. FIG. 4B is a front view of another gripping tool of the another cut-away device used in the first embodiment as viewed from the opposite side of the pipe breakage part. FIG. 5A is a front view of a cut-away device for support cut-off used in the first embodiment. FIG. 5B is a front view of a cutting section of the cut-away device for support cut-off used in the first embodiment. FIG. 5C is a front view of a guide of the cut-away device for support cut-off used in the first embodiment. Note that the cut-away devices illustrated in FIGS. 2 and 3 are assumed to be the same although the outer shapes thereof slightly differ from each other on the drawings. As illustrated in FIGS. 2, 3A, 3B, and 3C, a cut-away device 24 has a guide section 25 for guiding the broken measurement pipe 11 to be cut, a gripping tool 26 for gripping the measurement pipe 11 guided by the guide part 25, and a cutting section 27 for cutting the measurement pipe 11 near the portion gripped by the gripping tool 26. The cut-away device 24 is further provided with a hoisting tool 20 capable of moving up and down in the reactor. The hoisting tool 20 is used to move the cut-away device 24 to the breakage part of the measurement pipe 11 with the surrounding around the cut-away device 24 checked with a remote camera, etc. The cut-away device 24 has a thickness of as small as 100 mm or less, making it easy for the cut-away device to move down to the breakage part of the measurement pipe 11, and enabling the cutting work in a narrow portion between the shroud 2 and the diffuser 10. Similarly, as illustrated in FIGS. 4A and 4B, another cut-away device 24a has a guide section 25a for guiding the measurement pipe 11, a gripping tool 26a for gripping the measurement pipe 11 guided by the guide part 25a, and a cutting section 27a for cutting the measurement pipe 11 near the portion gripped by the gripping tool 26a. Further, as illustrated in FIGS. 5A, 5B, and 5C, a cut-away device 24b for cutting the support 13 has a guide section 25b for guiding the support 13, a gripping tool 26b for gripping the support 13 guided by the guide part 25b, and a cutting section 27b for cutting the support 13 near the portion gripped by the gripping tool 26b. That is, the present embodiment has two types of cut-away devices 24 and 24a (FIGS. 3 and 4) for cutting away the measurement pipe 11 and has one cut-away device 24b (FIG. 5) for cutting away the support 13. These cut-away devices 24, 24a, and 24b have the guide sections 25, 25a, and 25b having different shapes from one another and gripping tools 26, 26a, and 26b each formed into a scissor-like shape so as to grip the measurement pipe 11 or the support 13. The use of these cut-away devices 24, 24a, and 24b allows cutting operation to be performed at an accurate position in a stable posture with respect to the measurement pipe 11 or the support 13. Now, the detailed operation of step S1 of cutting the measurement pipe 11 and the support 13 will be described. In step S1a, the cut-away devices 24 or 24b illustrated in FIGS. 2, 5A, 5B, and 5C is set to the support 13 of the measurement pipe 11. Subsequently, in step S1b, the gripping tools 26 or 26b is used to grip the measurement pipe 11 and the support 13. Further, in step S1c, the measurement pipe 11 and the support 13 are cut by the cutting sections 27 or 27b of the cut-away devices 24 or 24b. After that, the cut parts of the measurement pipe 11 and the support 13 are collected. As described above, in step S1, the cut-away devices 24 or 24b is set to the support 13, the gripping tools 26 or 26b of the cut-away device 24 or 24b is used to grip the measurement pipe 11 and the support 13, respectively, and the measurement pipe 11 and the support 13 are cut respectively by the cutting sections 27 or 27b, followed by collection of the cut parts of the measurement pipe 11 and the support 13. That is, after cutting the measurement pipe 11 and the support 13 around the breakage part, the cut-away device 24 or 24b collects the cut samples (measurement pipe 11 and the support 13) while gripping them by the gripping tools 26 or 26b. The gripping tools 26 or 26b, which are normally driven by the air supply, are each provided with an elasticity imparting member such as a spring as an auxiliary function. Thus, even if the air supply is interrupted, the gripping tools can grip the cut samples by the elastic force of the spring for collection without dropping them in the reactor. The cutting section 27 included in the cut-away device 24 may adopt electro-discharge machining or mechanical machining as the cutting method. After the measurement pipe 11 and the support 13 have been cut away by the cut-away device 24 or 24b, a spool piece 28 is used to supplement the cut off part. The spool piece 28 can be deformed so as to match the shape of the breakage part to be repaired of the measurement pipe 11. Further, although the spool piece 28 of the present embodiment may have a similar shape to the measurement pipe 11, it may have a different shape. That is, it is only necessary for the spool piece 28 to have a tubular shape capable of supplementing the cut off part of the measurement pipe 11. Next, the detailed operation of step S2 of attaching a clamp will be described. FIG. 6 is a perspective view illustrating a state before attachment of a clamp used in the first embodiment. FIG. 7 is an enlarged perspective view illustrating a state where a clamp used in the first embodiment has been attached. In step S2a, a clamp 29 retaining the spool piece 28, to both ends of which connection pipes 30 each made of a shape-memory alloy (SMA) are respectively connected, is set to the remaining part of the support 13 using a not-illustrated hoisting tool, as illustrated in FIG. 6. Subsequently, in step S2b, a bolt (not illustrated) of the clamp 29 is tightened to fix the clamp 29 to the remaining part of the support 13, as illustrated in FIG. 7. That is, in step S2, the clamp 29 is set on the support 13 of the diffuser 10 of the jet pump 4 and is then fixed to the same. The spool piece 28 is hoisted up to the breakage part of the measurement pipe 11 while being retained by the clamp 29 as illustrated in FIGS. 6 and 7. The target position of the spool piece 28 in height direction and in circumferential direction is calculated utilizing the remaining part of the support 13. Thus, the spool piece 28 is retained to the clamp 29 capable of securely retaining the spool piece 28, and this spool piece 28 is supplemented to the cut off part of the measurement pipe 11. The connection pipes 30 each made of a shape-memory alloy having characteristics that, when it is heated and reaches a certain temperature, the shape thereof is restored to its original shape are connected respectively to both ends of the spool piece 28, as illustrated in FIG. 6. As described above, step S2 is a retaining step of using the clamp 29 to retain the connection pipes 30 for connecting the cut off ends of the measurement pipe 11 on the jet pump 4. Next, the detailed operation of step S3 of connecting the cut off ends of the measurement pipe 11 will be described. FIG. 8 is a cross-sectional view of the connection pipe made of a shape-memory alloy used in the first embodiment. FIGS. 9A, 9B, and 9C are process views illustrating the expanding order of a driver in the shape-memory alloy connection pipe of FIG. 8. FIG. 10 is a perspective view illustrating a heater for heating the shape-memory alloy connection pipe of FIG. 8. The connection pipes 30 each made of a shape-memory alloy having characteristics that, when it is heated and reaches a certain temperature, the shape thereof is restored to its original shape are connected to both ends of the spool piece 28, and the end of the cut existing measurement pipe 11 is inserted into the end of each connection pipe 30 for connection (step S3a). As illustrated in FIG. 8, the shape-memory alloy connection pipe 30 has a driver 17 and a liner 18 fitted to the inner circumferential surface of the driver 17. As advance preparation, the shape-memory alloy connection pipe 30 is cooled with coolant such as liquid nitrogen or dry ice to a temperature range where the driver 17 is deformable. Then, as illustrated in FIGS. 9A and 9B, in a state where the driver 17 has been cooled, a rod member 19 having a tapered lower part is inserted into the driver 17 while a predetermined load is applied to expand the inner diameter of the driver 17 to a size capable of accommodating the liner 18 having a plurality of claw portions 18a in the inner circumference thereof (refer to FIG. 9C). The inner diameter of the liner 18 is set to a size allowing easy insertion of the measurement pipe 11. Finally, the liner 18 is inserted into the expanded driver 17. Then, the end of the broken measurement pipe 11 is inserted into the each of thus prepared shape-memory alloy connection pipes 30 from both ends of the drivers 17 using a remote control gripping tool or the like. Subsequently, in step S3b, a heater 31 for uniformly heating the outer surface of the shape-memory alloy connection pipe 30 is installed in the reactor as illustrated in FIG. 9 upon completion of the insertion of the end of the broken measurement pipe 11, and the heater 31 is used to heat the driver 17 until the size of the driver 17 is restored to the size before the expansion. As illustrated in FIG. 10, the heater 31 is formed into a shape obtained by cutting a pipe in its axial direction and can thus uniformly heat the shape-memory alloy 30 to be heated by utilizing the radiation and convection of heat from a heating source. This heater 31 is easy to remove, so that it can be used in a narrow portion in the reactor. The driver 17 heated by the heater 31 is contracted to compress the liner 18 in the driver 17. As a result, the claw portions 18a formed in the inner circumference of the liner 18 bite into the measurement pipe 11, thereby increasing the connection strength with the measurement pipe 11 and enhancing sealing property (step S3c). As described above, according to the present embodiment, upon occurrence of a breakage of the measurement pipe 11 which is horizontally arranged at the lower part of the jet pump 4 provided in the reactor water in the reactor pressure vessel 1, the breakage part of the measurement pipe 11 is cut and removed, and then the ends of the cut measurement pipe 11 are connected to each other by the shape-memory alloys 30 with the spool piece 28 interposed between the shape-memory alloys 30. Thus, this method can cope with a breakage event occurring in a narrow portion of the lower part where the measurement pipe 11 is horizontally arranged in the water, improving workability of the connection work for connecting the ends of the cut portion, which enables a reduction in the work periods for repair. Further, according to the present embodiment, the samples cut by the cutting devices 24 and 24b are collected in a state where they are retained by the gripping tools 26 and 26b, allowing the causes of the breakage to be investigated from the breakage surface of each sample. In the present embodiment, after the breakage part of the measurement pipe 11 is cut, the ends of the cut measurement pipe 11 are connected by the shape-memory alloys 30 with the spool piece 28 interposed between the shape-memory alloys 30. Alternatively, the ends of the cut measurement pipe 11 may be connected directly by one shape-memory alloy 30 without intervention of the spool piece 28. FIGS. 11A and 11B are a front view and a partially cross-sectional view illustrating the connection pipe of a biting joint used in a second embodiment. In the present embodiment, the connection pipe used in step S3 of FIG. 1 is not the shape-memory alloy (SMA) connection portion 30 as described in the first embodiment, but a biting joint 40 as illustrated in FIGS. 10A and 10B. Components other than the connection pipe are the same as those of the first embodiment. As illustrated in FIGS. 11A and 11B, the biting joint 40 is constituted by three parts: a joint body 41, a union nut 42; and a sleeve 43. First, when one end of the broken measurement pipe 11 is inserted into one insertion port of the biting joint 40 followed by tightening the union nut 42, a cutting edge of the sleeve 43 bites into the measurement pipe 11 to retain the measurement pipe 11 and seal between the sleeve 43 and measurement pipe 11. The outer circumferential surface of the sleeve 43 is press-bonded to the tapered surface of the joint body 41 to seal between the sleeve 43 and joint body 41. Further, the other end of the broken measurement pipe 11 is inserted into the other insertion port of the biting joint 40 followed by tightening the union nut 42, thereby establishing connection of the broken measurement pipe 11. The tightening of the union nut 42 can be achieved by using a small remote ratchet wrench, allowing the union nut 42 to be tightened in a narrow portion in the reactor. As described above, according to the present embodiment, use of the biting joint 40 as the connection pipe allows a robust repair method having a short preparation time and a short repair time to be provided as in the case of the first embodiment. Although one end and the other end of the broken measurement pipe 11 are directly connected to each other by the biting joint 40 in the present embodiment, the ends of the broken measurement pipe 11 may be connected by using the biting joints 40 respectively with the spool piece 28 interposed between the biting joints 40. FIG. 12 is an enlarged cross-sectional view illustrating the connection pipe of fillet welding used in a third embodiment. In the present embodiment, one end and the other end of the measurement pipe 11 whose horizontal part has been broken are welded through a joint 45 for connection. The welding work of welding one end and the other end of the measurement pipe 11 through the joint 45 will be described. As illustrated in FIG. 12, the joint 45 made of the same material as that of the measurement pipe 11 is introduced inside the reactor using a remote control gripping tool. Subsequently, one end of the broken measurement pipe 11 is inserted into the joint 45 followed by fillet welding in the circumferential direction of the measurement pipe 11 to thereby form a fillet-welded portion 46. After the completion of the connection between one ends of the joint 45 and pipe 11, the other end of the measurement pipe 11 is inserted into the joint 45 followed by the welding to thereby achieve the connection of the measurement pipe 11. At this time, the welding is performed by means of, e.g., underwater laser welding capable of performing welding of the horizontally extending part of the measurement pipe 11. As described above, the repair work of the present embodiment requires only bringing down an underwater laser welding machine, allowing the repair work to be performed in a narrow space. Although one end and the other end of the broken measurement pipe 11 is directly welded by using the joint 45 in the present embodiment, the ends of the broken measurement pipe 11 are welded with the joints 45 with the spool piece 28 interposed between the joints 45. While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.
	description	The following relates to the nuclear reactor arts, electrical power generation arts, nuclear safety arts, and related arts. Nuclear reactors employ a reactor core comprising a mass of fissile material, such as a material containing uranium oxide (UO2) that is enriched in the fissile 235U isotope. Primary coolant water, such as light water (H2O) or heavy water (D2O) or some mixture thereof, flows through the reactor core to extract heat for use in heating secondary coolant water to generate steam or for some other useful purpose. For electrical power generation, the steam is used to drive a generator turbine. In thermal nuclear reactors, the primary coolant water also serves as a neutron moderator that thermalizes neutrons, which enhances reactivity of the fissile material. Various reactivity control mechanisms, such as mechanically operated control rods, chemical treatment of the primary coolant with a soluble neutron poison, or so forth are employed to regulate the reactivity and resultant heat generation. In a pressurized water reactor (PWR), the primary coolant water is maintained in a subcooled state in a sealed pressure vessel that also contains the reactor core. In the PWR, both pressure and temperature of the primary coolant water are controlled. To extract power from the PWR or other nuclear reactor, secondary coolant water is flowed in thermal communication with the primary coolant water. A steam generator device is suitably used for this thermal exchange. In the steam generator, heat (i.e., energy) is transferred from the reactor core to the secondary coolant water via the intermediary of the primary coolant water. This heat converts the secondary coolant water from liquid water to steam. The steam is typically flowed into a turbine or other power conversion apparatus that makes practical use of the steam power. Viewed another way, the steam generator also serves as a heat sink for the primary coolant. The steam generator may, in general, be located external to the pressure vessel, or internal to the pressure vessel. A PWR with an internal steam generator is sometimes referred to as an integral PWR, an illustrative example of which is shown in Thome et al., “Integral Helical Coil Pressurized Water Nuclear Reactor”, U.S. Pub. No. 2010/0316181 A1 published Dec. 16, 2010 which is incorporated herein by reference in its entirety. This publication discloses a steam generator employing helical steam generator tubing; however, other coil geometries including straight (e.g., vertical) steam generator tubes are also known. This publication also discloses an integral PWR in which the control rod drive mechanism (CRDM) is also internal to the pressure vessel; however, external CRDM designs are also known. Some illustrative examples of internal CRDM designs include: Stambaugh et al., “Control Rod Drive Mechanism for Nuclear Reactor”, U.S. Pub. No. 2010/0316177 A1 published Dec. 16, 2010 which is incorporated herein by reference in its entirety; and Stambaugh et al., “Control Rod Drive Mechanism for Nuclear Reactor”, Int'l Pub. WO 2010/144563 A1 published Dec. 16, 2010 which is incorporated herein by reference in its entirety. During normal PWR operation, the primary coolant is subcooled and is at both elevated temperature and elevated pressure. For example, one contemplated integral PWR is designed to operate with the primary coolant at a temperature of greater than 300° C. and a pressure of about 2000 psia. These elevated conditions are maintained by heat emitted by the radioactive nuclear reactor core. In various abnormal event scenarios, this radioactivity can increase rapidly, potentially leading in turn to rapid and uncontrolled increase in primary coolant pressure and temperature. For example, in a “loss of heat sink event” the secondary coolant flow in the steam generator fails, leading to loss of heat sinking provided by the secondary coolant. In a SCRAM failure, the control rod system is compromised such that the control rods may be unable to “SCRAM”, that is, be released to fall into the reactor core, to provide rapid shutdown. While a SCRAM failure may not cause immediate core heating, the loss of this safety system typically calls for immediate shutdown of the reactor. In a loss of coolant accident (LOCA), a rupture in the pressure vessel or a pipe connecting with the pressure vessel allows some of the primary coolant to be released under pressure from the pressure vessel. The released primary coolant generally expands as steam outside of the pressure vessel. A LOCA introduces numerous potential safety issues such as a possible release of radioactivity, emission of hot steam, and so forth. Furthermore, a LOCA can constitute a positive feedback condition as the lost primary coolant causes the reactor core to heat up uncontrollably leading to increased pressure that drives further loss of primary coolant. In view of such concerns, a PWR typically has an external containment structure to contain any release of primary coolant in a LOCA. The PWR also typically has an associated emergency core cooling system (ECCS) that is designed to respond to an abnormal condition by bringing about rapid cooling of the reactor core, suppressing any concomitant pressure increase, and recapturing any released primary coolant steam. One component of the ECCS is typically a condenser (or a redundant set of condensers) that are connected with the pressure vessel to condense steam in the event of a LOCA or loss of heat sinking event. Disclosed herein are improvements that provide various benefits that will become apparent to the skilled artisan upon reading the following. In one aspect of the disclosure, an apparatus comprises: a pressurized water reactor (PWR) including a pressure vessel having a lower portion containing a nuclear reactor core comprising a fissile material and an upper portion defining an internal pressurizer volume; a condenser supported by the upper portion of the pressure vessel; and a steam line connecting the internal pressurizer volume with a condenser inlet of the condenser. In another aspect of the disclosure, an apparatus comprises: a PWR including a pressure vessel having a lower portion containing a nuclear reactor core comprising a fissile material and an upper portion defining an internal pressurizer volume; a condenser; and a single metal forging providing fluid communication between the internal pressurizer volume with a condenser inlet of the condenser, the single metal forging having a first end welded to the pressure vessel and a second end welded to the condenser. In another aspect of the disclosure, an apparatus comprises: a PWR including a pressure vessel having a lower portion containing a nuclear reactor core comprising a fissile material and an upper portion defining an internal pressurizer volume; a condenser secured to the upper portion of the pressure vessel and having a condenser inlet in fluid communication with the internal pressurizer volume; a heat sink in fluid communication with the condenser, the condenser operating as a passive heat exchanger to condense steam from the internal pressurizer volume into condensate while rejecting heat to the heat sink; and a condenser outlet connected with the pressure vessel to flow the condensate back into the pressure vessel. With reference to FIG. 1, an illustrative nuclear reactor of the pressurized water reactor (PWR) type 10 includes a pressure vessel 12, which in the illustrative embodiment is a generally cylindrical vertically mounted vessel. Selected components of the PWR that are internal to the pressure vessel 12 are shown diagrammatically in phantom (that is, by dotted lines). A nuclear reactor core 14 is disposed in a lower portion of the pressure vessel 12. The reactor core 14 includes a mass of fissile material, such as a material containing uranium oxide (UO2) that is enriched in the fissile 235U isotope, in a suitable matrix material. In a typical configuration, the fissile material is arranged as “fuel rods” arranged in a core basket. The pressure vessel 12 contains primary coolant water (typically light water, that is, H2O, although heavy water, that is, D2O, is also contemplated) in a subcooled state. A control rods system 16 is mounted above the reactor core 14 and includes control rod drive mechanism (CRDM) units and control rod guide structures configured to precisely and controllably insert or withdraw control rods into or out of the reactor core 14. The illustrative control rods system 16 employs internal CRDM units that are disposed inside the pressure vessel 12. Some illustrative examples of suitable internal CRDM designs include: Stambaugh et al., “Control Rod Drive Mechanism for Nuclear Reactor”, U.S. Pub. No. 2010/0316177 A1 published Dec. 16, 2010 which is incorporated herein by reference in its entirety; and Stambaugh et al., “Control Rod Drive Mechanism for Nuclear Reactor”, Int'l Pub. WO 2010/144563 A1 published Dec. 16, 2010 which is incorporated herein by reference in its entirety. In general, the control rods contain neutron absorbing material, and reactivity is increased by withdrawing the control rods or decreased by inserting the control rods. So-called “gray” control rods are continuously adjustable to provide incremental adjustments of the reactivity. So-called “shutdown” control rods are designed to be inserted as quickly as feasible into the reactor core to shut down the nuclear reaction in the event of an emergency. Various hybrid control rod designs are also known. For example, a gray rod may include a mechanism for releasing the control rod in an emergency so that it falls into the reactor core 12 thus implementing a shutdown rod functionality. The illustrative PWR 10 is an integral PWR, and includes an internal steam generator 18 disposed inside the pressure vessel 12. In the illustrative configuration, a cylindrical riser 20 is disposed coaxially inside the cylindrical pressure vessel 12. The riser 20 surrounds the control rods system 16 and extends upward, such that primary coolant water heated by the operating nuclear reactor core 14 rises upward through the cylindrical riser 20 toward the top of the pressure vessel, where it discharges, reverses flow direction and flows downward through an outer annulus defined between the cylindrical riser 20 and the cylindrical wall of the pressure vessel 12. This circulation may be natural circulation that is driven by reactor core heating and subsequent cooling of the primary coolant, or the circulation may be assisted or driven by primary coolant pumps (not shown). The illustrative steam generator 18 is an annular steam generator disposed in the outer annulus defined between the cylindrical riser 20 and the cylindrical wall of the pressure vessel 12. Vertically, the lower end of the illustrative steam generator 18 partially overlaps the control rod system 16, and the steam generator 18 extends upward to near the top of the cylindrical riser 20. The steam generator provides independent but proximate flow paths for downwardly flowing primary coolant and upwardly flowing secondary coolant. The secondary coolant enters at a feedwater inlet 22, flows upward through the steam generator 18 where it is heated by the proximate downwardly flowing primary coolant to be converted to steam, and the steam discharges at a steam outlet 24. FIG. 1 does not illustrate the detailed structure of the steam generator. Typically, the steam generator comprises steam generator tubes and a surrounding volume (or “shell”) containing the tubes, thus providing two proximate flow paths that are in fluid isolation from each other. In some embodiments, the primary coolant flows downward through the steam generator tubes (that is, “tube-side”) while the secondary coolant flows upward through the surrounding volume (that is, “shell-side”). In other embodiments, the primary coolant flows downward through the surrounding volume (shell-side) while the secondary coolant flows upward through the steam generator tubes (tube-side). In either configuration, the steam generator tubes can have various geometries, such as vertical straight tubes (sometimes referred to as a straight-tube once-through steam generator or “OTSG”), helical tubes encircling the cylindrical riser (some embodiments of which are described, by way of illustrative example, in Thome et al., “Integral Helical Coil Pressurized Water Nuclear Reactor”, U.S. Pub. No. 2010/0316181 A1 published Dec. 16, 2010 which is incorporated herein by reference in its entirety), or so forth. It will be noticed in FIG. 1 that the illustrative PWR 10 has the steam outlet 24 located at a low position, that is, near the bottom of the steam generator 18. However, the secondary coolant is converted to steam as the secondary coolant flows upwardly through the steam generator 18, such that the hottest steam is expected to be present near the top of the steam generator 18. The placement of the steam outlet 24 located at its illustrated low position reflects the presence of an annular steam jacket (not shown) disposed between the steam generator 18 and the cylindrical wall of the pressure vessel 12. This steam jacketing approach is optional, but has the benefit of providing a higher temperature outer surface for maintaining temperature stability. In an alternative embodiment, the steam jacket is omitted and the steam outlet is located at or near the top of the steam generator 18. The illustrative PWR 10 is an integral PWR including the steam generator 18 disposed inside the pressure vessel 12. In other embodiments, the PWR is not an integral PWR; rather the steam generator is located externally. In these embodiments, the feedwater inlet 22 and steam outlet 24 are suitably replaced by high pressure vessel penetrations flowing primary coolant water out of the pressure vessel, through the external steam generator, and back to the pressure vessel. Moreover, contemplated integral PWR designs may place the steam generator at various locations in the pressure vessel, such as partially surrounding the reactor core, or disposed inside the cylindrical riser, or so forth. The pressure vessel 12 defines a sealed volume that, when the PWR is operational, contains primary coolant water in a subcooled state. Toward this end, the PWR includes an internal pressurizer volume 30 disposed at, and defined in part by, an upper portion of the pressure vessel 12. The internal pressurizer volume 30 contains a steam bubble volume whose pressure controls the pressure of the primary coolant water in the pressure vessel 12. At least one steam pressure control device is provided to adjust or control the pressure of the steam bubble in the internal pressurizer volume 30. By way of illustrative example, the steam pressure control device or devices may include a heater 32 (e.g., one or more resistive heaters) that heats the steam to increase pressure, and/or a sparger 34 that injects cool water or steam into the steam bubble to reduce pressure. A baffle plate 36 separates the internal pressurizer volume from the remainder of the sealed volume of the pressure vessel 10. By way of illustrative example, in some embodiments the primary coolant pressure in the sealed volume of the pressure vessel 12 is at a pressure of about 2000 psia and at a temperature of about 300° C. (cold leg just prior to flowing into the reactor core 14) to 320° C. (hot leg just after discharge from the reactor core 14). These are merely illustrative subcooled conditions, and a diverse range of other operating pressures and temperatures are also contemplated. With continuing reference to FIG. 1, the PWR 10 is disposed in a containment structure 40, which may by way of illustrative example comprise a concrete, steel, steel-reinforced concrete, or other structure. The containment structure 40 is intended to contain any release of primary coolant water from the PWR 10 in the event of a loss of coolant accident (LOCA). In some embodiments the containment structure 40 may be partially or wholly subterranean. In the illustrative embodiment, at least a flood well 42 portion of the containment structure is buried, and the lower portion of the PWR 10 including the nuclear reactor core 14 resides in this flood well 42. FIG. 1 also diagrammatically depicts an emergency core cooling system (ECCS) configured to remediate various abnormal operating conditions such as a LOCA, a loss of heat sinking event, or a SCRAM failure. The ECCS includes a water storage tank 50 disposed inside the containment 40. The water storage tank 50 is also sometimes referred to as a refueling water storage tank (since it may optionally be utilized as a source of make-up primary coolant water during refueling of the PWR 10) or as a reactor water storage tank. The water storage tank 50 is also referred to herein by the acronym “RWST” 50. With continuing reference to FIG. 1, the ECCS also includes a valve assembly comprising valves and piping for selectively interconnecting the RWST 50 and various components of the ECCS with each other and/or with the PWR 10. It is to be appreciated that FIG. 1 shows a schematic diagram of the ECCS for the purpose of illustrating preferred embodiments, and it is to be understood that further additional or substitute features may also or alternatively be included based on considerations of the specific design implementation, applicable government regulations, or so forth. In describing the illustrative ECCS embodiments, the following terminology is used herein. Terms such as “normally open” or “normally closed” refer to the normal condition or state of the valve or other element during normal operation of the PWR 10 for its intended purpose (for example, the intended purpose of generating electrical power in the case of a nuclear power plant). A term such as “abnormal operation signal” refers to a signal generated by a sensor or other device indicating that some metric or aspect of the PWR operation has deviated outside of the normal PWR operational space. By way of illustrative example, an abnormal operation signal may comprise a low reactor water level signal, or an abnormal operation signal may comprise a high reactor pressure signal. A low reactor water level signal may indicate a LOCA, while a high reactor pressure signal may indicate a loss of heat sinking event. Typically, an abnormal operation signal (or a combination of such signals) will automatically trigger an audible, visual, or other alarm to notify reactor operation personnel of the deviation, and/or will trigger an automated response by the ECCS. In some cases and in some embodiments, reactor operation personnel may be able to override or cancel an automated ECCS response. In some cases and in some embodiments, the ECCS response to an abnormal operation signal or a combination of such signals may be initiated manually by reactor operation personnel. To enable automatic alarm triggering and/or automated ECCS response, ECCS control circuitry 54 is provided. In FIG. 1 the ECCS control circuitry 54 is diagrammatically indicated; however, it is to be understood that the ECCS control circuitry 54 includes suitable electronics, analog and/or digital circuitry, digital processor or digital control integrated circuit (IC) chips, or so forth along with suitable sensor devices in order to detect abnormal conditions, generate corresponding abnormal operation signals, activate visual and/or auditory alarms, and perform ECCS operations such as opening valves, closing valves, or so forth in order to implement suitable emergency core cooling operations in response to a detected abnormal condition. Some sensors that may be employed include: a pressure sensor for detecting an abnormally high reactor pressure and generating the high reactor pressure signal; a water level sensor for detecting a low level of primary coolant water in the pressure vessel 12 and generating the low reactor water level signal; an in-core temperature sensor for detecting an abnormally high temperature of the nuclear reactor core 14, or so forth. Optionally, the ECCS control circuitry 54 may include processing capability in the form of a computer, microcontroller, or other digital processing device that is programmed or otherwise configured to process received abnormal operation signals and to generate suitable alarms and or cause the ECCS to perform a suitable automated response. In some embodiments, the ECCS control circuitry 54 is capable of making certain inferences in deciding a suitable response—for example, a combination of a low reactor water level signal and a high reactor pressure signal may be inferred to indicate a LOCA, whereas a low reactor pressure signal occurring without a concomitant low reactor water level signal may be inferred to indicate a loss of heat sink event. In embodiments in which an automated ECCS response is provided, the ECCS control circuitry 54 suitably includes actuation lines for causing selected valves to open or close. The actuation lines are typically wires or other electrical conductors, but other types of actuation such as pneumatic lines are also contemplated. Some types of abnormal events that are to be remediated by the ECCS entail an increase in pressure in the PWR 10. For example, a loss of heat sink event (for example, caused by a loss of feedwater flow into the feedwater inlet 22 of the steam generator 18) will produce heating that in turn increases pressure inside the PWR 10. A LOCA will similarly typically lead to heating and pressure increase. An uncontrolled or excessive pressure increase in the PWR 10 is problematic since it can compromise the sealing integrity of the pressure vessel 12 and can lead to escape of primary coolant water in the form of high pressure steam. To control a pressure increase in the PWR 10, at least one condenser is provided inside the containment structure 40. In the illustrative embodiment, two condensers 60, 62 are provided for redundancy in order to facilitate failsafe ECCS operation. More generally, one, two, three, four, or more condensers are suitably provided. The condensers 60, 62 are designed to operate at high pressure. As shown in FIG. 1, in embodiments disclosed herein the condensers 60, 62 are mounted on the pressure vessel 12 proximate to the internal pressurizer volume 30. It is recognized herein that this arrangement has certain advantages over an arrangement in which the condensers are located further away from the pressure vessel and connected with the pressure vessel via a steam pipe. For example, the condensers 60, 62 have respective high pressure fluid connections 64, 66 with the internal pressurizer volume 30, and more particularly with the steam bubble in the internal pressurizer volume 30. These high pressure steam connections 64, 66 are shortened in length as compared with an arrangement in which the condensers are located further away from the pressure vessel, which reduces the likelihood of a rupture in these connections 64, 66 leading to a LOCA. Moreover, the shortened length of the fluid connections 64, 66 reduces their fluid resistance thus enabling them to be made of smaller diameter as compared with a longer steam pipe leading to a condenser located away from the pressure vessel. A consequence of the smaller diameter of the high pressure steam connections 64, 66 is that if a rupture does occur the resulting LOCA may be less severe. To provide failsafe operation, the condensers 60, 62 are suitably passive heat exchangers that reject heat from the steam admitted at the respective condenser inlets 64, 66 to an external heat sink 70 located outside of the containment structure 40. Each condenser 60, 62 is suitably of a “once-through” design having tube bundles surrounded by a shell (details not shown). In one suitable embodiment, steam from the internal pressurizer volume 30 of the PWR 10 flows on the tube-side and water from the external heat sink 70 flows on the shell-side; however, the reverse configuration is also contemplated in which the steam flows on the shell-side and water from the external heat sink 70 flows tube-side. In the following, the condenser 60 is particularly referred to as an illustrative example. Liquid water from the external heat sink 70 flows via a first pipe 72 into the condenser 60, where heat from the steam transfers to the cooler water from the external heat sink 70 causing the latter to boil or vaporize. The resulting water from the external heat sink 70 (now in a steam phase or mixed steam/water phase) flows via a second pipe 74 back to the external heat sink 70. The flow of water/steam from the external heat sink 70 in the pipes 72, 74 is driven by gravity and density difference between the inflowing water and the outflowing steam or mixed steam/water. In the illustrative embodiment, the pipes 72, 74 have open ends at the external heat sink side that are in fluid communication with water in the external heat sink 70 so that water from the external heat sink 70 flows into the first pipe 72 and the water/steam mixture discharges out of the second pipe 74 into the external heat sink 70. However, in an alternative embodiment, the open ends of the pipes 72, 74 are replaced by a heat exchanger coupling disposed in the external heat sink 70 (not shown) forming closed recirculation path in which the steam/water mixture from the second pipe 74 condenses back into water (rejecting the heat into the external heat sink 70 as before) and the recondensed water flows back into the first pipe 72. Operation of the condenser 62 is the same in order to provide redundancy, but is not illustrated in FIG. 1. The plural condensers 60, 62 may in general be connected with the same external heat sink, or may be connected with different external heat sinks to provide further redundancy. The external heat sink 70 is suitably a body of water disposed outside the containment structure 40, such as a natural or artificial pond, lake, pool, or the like. Such an external heat sink 70 is also sometimes referred to as an “ultimate” heat sink. In some embodiments, the external heat sink 70 is located in a reactor services building or other structure or enclosure. The water volume of the external heat sink 70 should be sufficient to provide an extended period of operation of the high pressure condenser 60. For example, in some contemplated embodiments the external heat sink 70 is designed to have water volume sufficient for 72 hours continuous operation of the condenser 60. Each condenser 60, 62 includes a respective condenser outlet 76, 78 to allow condensed water to flow back into the pressure vessel 12. The illustrative condenser outlets 76, 78 connect back into the pressure vessel 12 at an upper plenum 79 of the pressure vessel 12 located below the baffle plate 36 and above the top of the steam generator 18. Alternatively, the condenser outlets can connect with the pressure vessel 12 at a lower point. By way of illustrative example, an alternative condenser outlet 76′ for the condenser 60 connects with a reactor coolant inventory makeup line 80 that feeds into a vessel penetration 82 of the pressure vessel 12. Although not illustrated, the condenser outlets 76, 76′, 78 optionally include a gas trap to trap gaseous nitrogen (N2) or gaseous oxygen (O2) that exits the condenser 60, 62 at the condenser outlet, in order to prevent these gases from entering into the pressure vessel 12. The condensers 60, 62 may be used in responding to various types of abnormal events, such as LOCA or loss of heat sinking events. In a suitable approach the ECCS control circuitry 54 opens valves (not shown) to initiate operation of the condensers 60, 62 responsive to a low reactor water level signal, a high reactor pressure signal, or the combination of both a low reactor water level signal and a high reactor pressure signal. Various valve configurations are contemplated. For example, in one approach the steam connections 64, 66 are normally open (that is, open during operation of the PWR, with any isolation valve provided for maintenance being open), while a valve at the outlet 76, 76′, 78 (to provide an illustrative example, a valve V1 shown in the alternative condenser outlet 76′ of the condenser 60) is normally closed. To initiate operation of the condensers 60, 62, the condenser outlet valves are opened (e.g., in the alternative embodiment employing the condenser outlet 76′, the valve V1 is opened to initiate operation of the condenser 60). Alternatively, it is contemplated to have the steam connections 64, 66 normally closed and to open valves (not shown) in the steam connections 64, 66 to initiate operation of the condensers 60, 62. In the case of a LOCA response, it is advantageous to reduce pressure in the pressure vessel 12 as quickly as feasible in order to allow for injection of makeup water as soon as practicable. Toward this end, once the pressure in the pressure vessel 12 decreases to below a preselected pressure threshold (e.g., a pressure threshold of 200 psia, although other pressure thresholds are also contemplated), a low pressure vent valve V2 opens to connect a vent line 86 from the condenser outlets 76, 76′, 78 with a sparger 90 discharging into the RWST 50. In some embodiments, the vent line 86 is arranged in parallel with the condensate return path so that the condensers 60, 62 continue to operate while the sparger 90 accelerates depressurization. Once the pressure in the valve assembly lines is sufficiently depressurized by action of the sparger 90, a valve V3 opens to allow water to flow from the RWST 50 into the reactor coolant inventory makeup line 80 and vessel penetration 82 in order to provide makeup water to compensate for primary coolant water lost in the LOCA. Flow of water from the RWST 50 to the pressure vessel 12 via the valve V5, reactor coolant inventory makeup line 80, and vessel penetration 82 starts when the reactor pressure is less than the sum of the pressure in the containment structure 40 and the gravity head provided by the water level in the RWST 50. Toward this end, the RWST 50 is preferably located at an elevated position in the containment structure 40. Optionally, an external water inlet 88 is provided to deliver additional water to the reactor coolant inventory makeup line 80 through a valve V4 in the event that the water supply in the RWST 50 is exhausted. Optionally, the ECCS may include other remedial mechanisms besides the condensers 60, 62 and primary coolant water makeup as provided by the RWST 50. For example, in a SCRAM failure entailing a malfunction of the control rods system 16, also sometimes also referred to as an anticipated transient without SCRAM (ATWS), it is desired to shut down the reactor as quickly as possible without the use of the control rods system 16. Toward this end, a quench tank 901 contains a solution of soluble neutron poison for delivering a high concentration of soluble neutron poison into the primary coolant water in the pressure vessel 12 to quench core reactivity. In the illustrative embodiment, the quench tank 901 is an emergency boron tank 901 containing a concentrated solution of sodium pentaborate or another soluble boron compound; however, the quench tank may in general contain a solution of another species of soluble poison. The boron tank 901 is connected with a steam line 92 via a valve V5 to provide pressurization of the emergency boron tank 901 in the event of a SCRAM failure. The steam line 92 is taken off of the steam connection 64 of the condenser 60 (as illustrated in FIG. 1; however, the steam line 92 may optionally also connect with the steam connection 66 of the condenser 62, or to provide further redundancy a separate emergency boron tank may be pressurized by each respective condenser steam connection 64, 66). The emergency boron tank 901 is also connected with the reactor coolant inventory makeup line 80 that feeds into a vessel penetration 82 of the pressure vessel 12 via a valve V6. The valves V5, V6 are normally closed (that is, are closed during normal operation of the PWR 10). When the ECCS control circuitry 54 detects a SCRAM failure, the valves V5, V6 are opened manually or by an automatic control signal from the ECCS control circuitry 54. Opening the valve V5 places the steam bubble in the internal pressurizer volume 30 into fluid communication with the emergency boron tank 901 to pressurize the emergency boron tank 901, which is suitably located above the RWST 50. The relative pressure head between the pressurized boron tank 901 and the primary coolant water in the pressure vessel 12 allows the boron solution to flow into the pressure vessel 12 through the opened valve V6, reactor coolant inventory makeup line 80 and the vessel penetration 82. The ECCS shown in FIG. 1 is an illustrative example. It is to be understood that various levels of redundancy may be incorporated into the ECCS to facilitate failsafe operation. For example, one or more of the various valves V1, V2, V3, V4, V5 may incorporate various combinations of redundant parallel paths, may include check valves, may include manually operated isolation valves for use during maintenance operations or the like, or so forth. Duplication of the emergency boron tank 901 and/or further duplication of the condensers 60, 62 (e.g., providing three or more condensers), or redundancy of other components may be provided. Moreover, it is to be understood that various combinations of disclosed components or aspects may be employed in various embodiments. For example, in some embodiments the emergency boron tank 901 may be omitted in favor of another auxiliary reactivity control mechanism, or an emergency boron tank pressurized by a dedicated gas nitrogen source may be provided in place of the illustrative arrangement. Having with reference to FIG. 1 provided an overview of an illustrative ECCS system employing condensers 60, 62 secured with an upper portion of the pressure vessel 12, some further aspects of this arrangement are next described. With reference to FIG. 2, an enlarged view of an upper portion of the pressure vessel 12 is shown. FIG. 2 demonstrates that the detailed shape of the upper portion of the pressure vessel 12 can vary amongst different embodiments—for example, the upper portion of the pressure vessel 12 shown in FIG. 2 differs from that shown in FIG. 1 by including a narrowing outer diameter as compared with the lower portion of the pressure vessel 12 in the example of FIG. 2. The condensers 60, 62 shown in FIG. 2 also include respective optional mounting brackets 100, 102 for securing, or contributing to securing, the condensers 60, 62 to the pressure vessel 12. Additionally or alternatively, the high pressure fluid connections 64, 66 of the respective condensers 60, 62 suitably secure, or contribute to securing, the condensers 60, 62 to the pressure vessel 12. The condensers 60, 62 are supported at an elevated position respective to the nuclear reactor core 12 by the pressure vessel 12 via the high pressure fluid connections 64, 66, or the optional mounting brackets 100, 102, or by a combination of these elements. The securing of the condensers 60, 62 should be sufficient that any force reasonably anticipated to act on the securing connection will not cause the condenser to move so as to create a double-ended break. With reference to FIG. 3, the emergency condensers 60, 62 are in fluid communication with the internal pressurizer volume 30 by steam connections 64, 66 that are designed to operate with a low pressure drop during normal operation and include a reduced area section at the inlet connection from the pressurizer (e.g., an internal orifice) that limits flow in the event of a pipe break. If multiple condensers are used (e.g., the illustrated two condensers 60, 62), and if the steam line between the pressure vessel 12 and one of the condensers is broken, then flow through the internal orifice will be the dominant cause of pressure drop and the flow lost through the break will be proportional to the ratio of the pipes broken versus the number of condensers. In some embodiments a pressure drop across the steam line is less than one-third of a pressure drop across orifices of the steam line. The steam connections 64, 66 convey steam from the steam bubble in the internal pressurizer volume 30 into an upper plenum region 110 of the condenser. The steam flows inside the tubes of a tube bundle 112, while water from the heat sink 70 (see FIG. 1) flows into the condenser from the first pipe 72 and flows on the shell side, that is, around the outsides of the tubes of the tube bundle 112. (In an alternative embodiment, the steam from the internal pressurizer volume 30 may flow on the shell-side while water from the heat sink 70 flows through the tubes of the tube bundle 112.) The tubes of the tube bundle 112 can have substantially any configuration, such as straight vertical tubes surrounded by a common shell (forming a once-through straight tube heat exchanger), or horizontal tubes, U-tubes, or coaxial tube heat exchangers (in which the tubes have individual shells). Heat from the steam is rejected to the proximate water from the heat sink to produce heated water, steam, or a mixture of heated water or steam that is returned to the heat sink 70 via the second pipe 74. The condensate formed by condensing the steam from the internal pressurizer volume then flows downward into a lower plenum 114 and drains into the pressure vessel 12 though the condenser outlets 76, 78 (only the condenser outlet 78 of the condenser 62 is visible in the perspective sectional view of FIG. 3). The condensate can be returned to the upper flow plenum 79 above the upper tubesheet of the steam generator 18 as shown in FIG. 3, or can be piped to discharge below the lower tubesheet (e.g., using the alternative condenser outlet 76′ shown in FIG. 1). Each condenser 60, 62 also has a steam line 92 in fluid communication with the lower plenum 114 that can be used to pressurize one or more sodium pentaborate tanks (e.g., emergency boron tank 901 shown in FIG. 1) and provide emergency depressurization through the vent line 86 and sparger 90 during the final phases of a LOCA blowdown. In a contemplated variation (not illustrated), an optional emergency boron supply is integrated with the condensers. In this approach, the lower plenum 114 is modified to include a reservoir for a boron-containing solution. This reservoir can be pressurized by the condensate line leaving the condenser, causing the boron to flow into the reactor to achieve emergency shutdown. In such embodiments the separate emergency boron tank 901 may optionally be omitted. The illustrative condensers 60, 62 are connected to the pressure vessel 12 without isolation valves. Upon condenser startup, a gradual introduction of water from the heat sink 70 (that is, secondary water) is performed to prevent excessive stresses inside the condenser. Alternatively, isolation valves (not shown) can be incorporated on the condenser outlet lines 76, 78 to allow the primary side of the condenser to fill with water during normal operation. If the condensers are insulated from the side of the pressurizer, the secondary side can be left open to the ultimate heat sink tanks with minimal heat loss. Condenser startup in this case would entail opening one or both of the primary isolation valves. With reference to FIG. 4, in some embodiments each steam connection 64, 66 is embodied as a single metal forging having a first end 120 welded to the pressure vessel 12 and a second end 122 welded to the condenser (and more particularly to the condenser inlet). In some embodiments, the single metal forging is suitably a single steel or steel alloy forging. In an alternative embodiment (not illustrated), each steam line is a double wall pipe. The steam connections 64, 66 are designed to exceed the maximum design pressure of the primary coolant system. The disclosed configuration in which the condensers 60, 62 are closely integrated with (e.g., secured with and optionally supported by) the pressure vessel 12 has numerous advantages over approaches in which the condensers are separate from the pressure vessel and connected by relatively longer steam lines. By close coupling multiple condensers 60, 62 to the upper portion of the reactor pressure vessel 12, the likelihood of accident scenarios involving breakage of the pressure vessel/condenser steam linkage is substantially reduced. This in turn reduces the frequency of early core damage as calculated in the probabilistic risk assessment. The disclosed integrated approach substantially reduces the likelihood of a double-ended break of the steam line. Such a double-ended break is further reduced when the optional brackets 100, 102 are employed to prevent shifting of the condensers 60, 62; however, even with such brackets omitted the use of a single steel or steel alloy forging for the steam connections 64, 66 substantially reduces likelihood of a double-ended break. Another advantage of the integrated configuration is that it can allow condensate from the condensers 60, 62 to be discharged upstream of the primary coolant pumps (in embodiments employing assisted or forced primary coolant circulation). This is because the condenser inlets 76, 78 inject the condensate at a high point, e.g. into the upper plenum 79. If the primary coolant pumps are located lower in the pressure vessel 12, then the pumps can optionally continue to operate during operation of the condensers 60, 62. Yet another advantage of the disclosed integrated approach is realized during refueling or other maintenance. At each refueling outage, the upper portion of the pressure vessel 12 is typically removed, together with the steam generator 18, and moved to a steam generator inspection station (not shown). The tubes in the emergency condensers 60, 62 are suitably inspected at the same time. The securing of the condensers 60, 62 with the upper portion of the pressure vessel 12 allows both condensers 60, 62 to be moved with the steam generator 18 to a compartment equipped to perform tube inspection. The preferred embodiments have been illustrated and described. Obviously, modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the invention be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.
	abstract	The invention comprises a method and apparatus for treating a tumor, comprising the steps of: (1) a main controller implementing an initial radiation treatment plan, as a current radiation treatment plan, using positively charged particles delivered from a synchrotron, along a beam transport line, through a nozzle system proximate the treatment room, and into the tumor; (2) concurrent with the step of implementing, imaging the tumor, such as with protons, to generate a current image; (3) upon detection of movement of the tumor relative to surrounding constituents of the patient using the current image, the main controller, using computer implemented code, automatically generating an updated treatment plan, the updated treatment plan becoming the current radiation treatment plan; and (4) repeating the steps of implementing, imaging, and generating an updated treatment plan at least n times, where n is a positive integer of at least one.
055481256	claims	1. A radiation protective glove for surgical and medical use comprising a layer of flexible polymer containing at least 25-90% by volume of particulate tungsten material and having a radiation absorbing capacity equivalent to that of at least 0.13 mm thickness of lead said layer of the glove being of a thickness of 0.1 to 1.3 mm and being sufficiently flexible to enable the wearer to bend finger portions of the glove without undue force, to hold instruments, and to obtain a sense of touch and feel through the walls of the glove. 2. A radiation protective glove according to claim 1 having radiation absorbing capacity equivalent to that of 0.13 mm thickness of lead. 3. A glove as claimed in claim 1 in which the polymer is an elastomeric polymer. 4. A glove as claimed in claims 3 in which the elastomeric polymer comprises an ethylene propylene or ethylene propylene diene copolymer. 5. A glove as claimed in claim 4 in which the elastomeric polymer contains up to 50% by weight of hydrocarbon plasticiser. 6. A glove as claimed in claim 1 which has a radiation capacity equivalent to that of at least 0.25 mm thickness of lead. 7. A glove as claimed in claim 1 which has a radiation capacity equivalent to that of at least 0.35 mm thickness of lead. 8. A glove as claimed in claim 1 in which the polymer layer has a thickness of 0.2 mm to 1.0 mm. 9. A glove as claimed in claim 1 which in the polymer layer contains 30% to 60% by volume of particulate tungsten material. 10. A glove as claimed in claim 1 which is capable of absorbing at least 85% of the incident radiation generated at voltages of 60 to 100 kVp. 11. A glove as claimed in claim 1 which is capable of absorbing at least 90% of the incident radiation generated at voltages of 60 to 100 kVp. 12. A glove as claimed in claim 1 which is capable of absorbing at least 95% of the incident radiation generated at voltages of 60 to 100 kVp. 13. A process for forming a flexible radiation protective glove for surgical and medical use having a radiation absorbing capacity equivalent to that of at least 0.13 mm thickness of lead which comprises forming the glove from a polymer composition comprising a flexible polymer and containing at least 25-90% by volume of a particulate tungsten material, said glove being sufficiently flexible to enable the wearer to bend finger portions of the glove without undue force, to hold instruments, and to obtain a sense of touch and feel through the walls of the glove, and wherein said wall of the glove has a thickness of 0.1 to 1.3 mm. 14. A process as claimed in claim 11 in which the forming step comprises a moulding step.
	claims	1. A method for controlling the reactivity in a solution nuclear reactor, the method comprising the steps of:(a) supplying a solution nuclear reactor having a nuclear reactor vessel therein;(b) placing one or more standpipes located in at least one low worth area of the nuclear reactor vessel, each of the one or more standpipes having a top end and an open bottom end located at a level below a solution level in the solution contained in the nuclear reactor vessel of the solution nuclear reactor;(c) supplying at least one gas system, wherein the at least one gas system is in fluidic communication with one or more of the standpipes; and(d) controlling the fluid level of the solution in the one or more standpipes via the use of the at least one gas system such that the solution nuclear reactor is maintained in a fail-safe mode. 2. The method of claim 1, wherein the at least one gas is selected from nitrogen, helium, air, or combinations of two or more thereof. 3. The method of claim 1, wherein the solution in the solution nuclear reactor remains homogeneous during controlling the reactivity in the solution nuclear reactor. 4. The method of claim 1, wherein the reactivity in the solution nuclear reactor is controlled without the use of any mechanical movement of any design feature within the reactor core. 5. A method for augmenting the control of the reactivity in a solution nuclear reactor, the method comprising the steps of:(i) supplying a solution nuclear reactor having a nuclear reactor vessel therein;(ii) placing one or more standpipes in the nuclear reactor vessel, the one or more standpipes each having an open bottom end located at a level below a solution level in the solution contained in the nuclear reactor vessel of the solution nuclear reactor;(iii) supplying at least one gas system, wherein the at least one gas system is in fluidic communication with one or more of the standpipes; and(iv) controlling the fluid level of the solution in the one or more standpipes via the use of the at least one gas system such that the solution nuclear reactor is maintained in a fail-safe mode. 6. The method of claim 5, wherein the at least one gas is selected from nitrogen, helium, air, or combinations of two or more thereof. 7. The method of claim 5, wherein the solution in the solution nuclear reactor remains homogeneous during the reactivity compensation. 8. The method of claim 5, wherein the reactivity in the solution nuclear reactor is controlled without the use of any mechanical movement of any design feature within the reactor core.
	summary
	claims	1. A method for obtaining an x-ray image of a subject, comprising the steps:irradiating a subject with x-rays produced in an x-ray tube by emitting electrons from a cathode onto a focal spot on a surface of an anode while rotating the anode around a rotation axis to cause an x-ray beam to be emitted from said focal spot, said surface being inclined relative to said rotation axis and thereby causing said x-ray beam to have a varying image resolution/definition within said x-ray beam from a side of said x-ray beam facing said cathode to a side of said x-ray beam facing said anode, with an x-ray beam of highest image resolution/definition being at said side of said x-ray beam facing said anode;gating said x-ray beam to produce a fan-shaped x-ray beam therefrom;moving said fan-shaped x-ray beam through an examination region, containing said subject, substantially in a direction of the rotation axis of said rotary anode by tilting said x-ray tube relative to said focal spot to cause said fan-shaped x-ray beam to always to be gated from said region of highest image resolution/definition during movement of said fan-shaped x-ray beam through the examination region; anddetecting x-rays in said fan-shaped x-ray beam attenuated by said subject and generating an x-ray image of the subject therefrom. 2. A method as claimed in claim 1 comprising gating said x-ray beam with a slit-shaped diaphragm to produce said fan-shaped x-ray beam, and displacing said slit-shaped diaphragm through said examination region in said direction of said rotation axis synchronized with the movement of the fan-shaped x-ray beam through the examination region. 3. A method as claimed in claim 1 comprising gating said x-ray beam with a slit-shaped diaphragm having a displaceable opening therein to produce said fan-shaped x-ray beam, and displacing said opening within said slit-shaped diaphragm in said direction of said rotation axis synchronized with the movement of the fan-shaped x-ray beam through the examination region. 4. A method as claimed in claim 1 wherein said rotary anode has a radial direction associated therewith, and comprising controlling operation of said cathode to selectively enlarge a cross-section of said electron beam to enlarge said focal spot in said radial direction. 5. A method as claimed in claim 1 comprising rotating said x-ray tube around an axis proceeding through said focal spot and perpendicular to said examination region while moving said fan-shaped x-ray beam through said examination region. 6. A method as claimed in claim 5 wherein said axis is a first axis, and additionally rotating said x-ray tube around a second axis disposed in a plane of said fan-shaped x-ray beam and being perpendicular to said rotation axis, said second axis being disposed outside of said focal spot at a side of said focal spot facing away from said examination region. 7. A method as claimed in claim 1 comprising detecting said fan-shaped x-ray beam attenuated by said subject using a radiation detector comprising a detector row extending through only a portion of said examination region transverse to a direction of movement of said fan-shaped x-ray beam through said examination region, by electronically moving said detector row through said examination region. 8. A method as claimed in claim 7 comprising gating said x-ray beam with a slit-shaped diaphragm having a slit-opening with a center point to produce said fan-shaped x-ray beam, and wherein said detector row has a center point, and orienting said x-ray tube, said slit-shaped diaphragm and said detector row relative to each other to place said focal spot, said center point of said opening and said center point of said row detector on a straight line that is moveable through said examination region. 9. A method as claimed in claim 1 comprising gating said x-ray beam with a first slit-shaped diaphragm to produce said fan-shaped x-ray beam before said fan-shaped x-ray beam passes through said examination region, and detecting said fan-shaped x-ray beam attenuated by said subject with a radiation detector, and gating said fan-shaped x-ray beam with a second slit-shaped diaphragm disposed approximate said radiation detector, and moving said second slit-shaped diaphragm through said examination region in said direction of said rotation axis synchronized with the movement of said fan-shaped x-ray beam through said examination region. 10. A method as claimed in claim 1 comprising gating said x-ray beam with a slit-shaped diaphragm, comprising two diaphragm plates disposed opposite each other that define an opening that gates said x-ray beam, to produce said fan-shaped x-ray beam, and selectively moving said diaphragm plates toward and away from each other to selectively define a width of said opening, and thus a width of said fan-shaped x-ray beam. 11. A method as claimed in claim 10 comprising detecting said fan-shaped x-ray beam attenuated by said subject using a radiation detector and, in said radiation detector, converting the attenuated x-rays into an electrical image signal, and also detecting scatter radiation, associated with said fan-shaped x-ray beam, with said radiation detector, and automatically determining a ratio of said scatter radiation to radiation converted into said electrical image signal and controlling displacement of said diaphragm plates relative to each other to widen said opening as said ratio decreases and to narrow said opening as said ratio increases. 12. A method as claimed in claim 1 wherein said fan-shaped x-ray beam has a dose rate associated therewith, and comprising automatically calculating a radiation exposure to the subject in said examination region from said dose rate and comprising detecting said fan-shaped x-ray beam attenuated by said subject with a radiation detector and, in said radiation detector, converting the attenuated radiation into an electronic image signal representing an image having an image contrast associated therewith, and automatically controlling said dose rate dependent on said radiation exposure and said image contrast to increase said dose rate upon a low image contrast and to decrease said dose rate upon a high radiation exposure. 13. A method as claimed in claim 1 wherein said subject is a female breast, and comprising detecting said fan-shaped x-ray beam attenuated by said female breast using a radiation detector disposed in a support plate, and compressing said female breast between said support plate and a compression plate disposed above said support plate while moving said fan-shaped x-ray beam through said examination region.
062263463	summary	BACKGROUND OF THE INVENTION 1. Field of the Invention This invention is related to an optical system for use with short wavelength radiation in photolithography equipment used in the manufacture of semiconductor devices. 2. Background of the Invention Photolithography is a well known manufacturing process used to create devices upon substrates. The process typically involves exposing a patterned mask to collimated radiation, producing patterned radiation, which is passed through an optical reduction system. The reduced patterned radiation or mask image is projected onto a substrate coated with photoresist. Radiation exposure changes the properties of the photoresist allowing subsequent processing. Photolithography machines, or "steppers", use two common methods of projecting a mask image onto a substrate: "step and repeat" and "step and scan". The step and repeat method sequentially exposes portions of a substrate to a mask image. The step and repeat optical system has a projection field which is large enough to project the entire mask image onto the substrate. After each image exposure, the substrate is repositioned and the process is repeated. In contrast, the step and scan method scans a mask image onto a substrate through a slit. Referring to FIG. 1, a ring field lithography system 100 for use in the step and scan method is shown. A moving mask 101 is illuminated by a radiation beam 103, which reflects off the mask 101 and is directed through a reduction ring field optical system 107. Within the optical system 107, the image is inverted and the arcuate shaped ring field 109 is projected onto a moving substrate 111. The arcuate slit shaped reduced image beam 109 can only project a portion of the mask 101, thus the image beam 109 must scan the complete mask 101 onto the substrate 111. Because the mask 101 and substrate 111 move synchronously, a sharp image is scanned onto the substrate 111. Once the complete mask 101 is scanned onto the substrate, the mask 101 and substrate 111 are repositioned and the process is repeated. The dimensions of the slit are typically described by a ring field radius and a ring field width. As manufacturing methods improve, the minimum resolution dimension which can be achieved with reduced pattern radiation decreases allowing more electronic components to be fabricated within a given area of a substrate. The number of devices that can be fabricated within an area of substrate is known as device density. A common measure of device density is the amount of memory that can be fabricated on a single DRAM chip. As resolution dimension decreases, DRAM memory size increases dramatically. With existing technology, 0.25 .mu.m resolution is possible. One well-known means of improving the resolution dimension and increasing device density is to use shorter exposure wavelength radiation during photolithography processes. The relationship between resolution dimension and radiation wavelength is described in the formula: R=(K.sub.1.lambda.)/(NA), wherein R is the resolution dimension, K.sub.1 is a process dependent constant (typically 0.7), .lambda. is the wavelength of the radiation, and NA is the numerical aperture of the optical system projecting the mask image. Either reducing the wavelength or increasing the NA will improve the resolution of the system. Improving the resolution by increasing the numerical aperture (NA) has several drawbacks. The most prevalent drawback is the concomitant loss in depth of focus with increased NA. The relationship between NA and depth of focus is described in the formula: DOF=(K.sub.2.lambda.)/NA.sup.2, wherein DOF is depth of focus, and K.sub.2 is a process dependent constant (typically close to unity). This simple relationship shows the inverse relationship between DOF and NA. For several reasons, including practical wafer flatness and scanning stage errors, a large depth of focus is on the order of .+-.1.0 micrometers is desirable. Immediately, the shortcomings of resolution improvement via numerical aperture increase can be seen. As lithography technologies evolve toward shorter wavelengths, projection systems operate in different regions of wavelength-NA space. For EUV lithography at an operational wavelength of 13.4 nm, 0.1 .mu.m resolution can be achieved with a projection system that has a numerical aperture of 0.10. This low numerical aperture affords a depth of focus of .+-.1 .mu.m. In stark contrast, deep ultraviolet (DUV) lithography at 193 nm requires a projection system with a numerical aperture of 0.75 to achieve 0.18 .mu.m features (assuming K.sub.1 =0.7). At this NA, the depth of focus has been reduced to .+-.0.34 .mu.m. This loss in depth of focus leads to a loss in the available process latitude, requiring tighter process control. As the process latitude shrinks, it becomes more difficult to maintain critical dimension (CD) control that is essential to the lithographic process. As is known in the art, short X radiation (less than about 193 nm) is not compatible with many refractive lens materials due to the intrinsic bulk absorption. To reduce the radiation absorption within an optical system, reflective elements may be used in place of refractive optical elements. State of the art DUV systems use catadioptric optical systems which comprise refractive lenses and mirrors. The mirrors provide the bulk of the optical power and the lenses are used as correctors to reduce the field dependent aberrations. To produce devices with smaller critical dimensions and higher device density than is possible with DUV systems, optical systems compatible with even shorter wavelength radiation are required. Extreme ultraviolet (EUV) radiation (.lambda. less than about 15 nm) cannot be focused refractively. However, EUV radiation can be focused reflectively using optical elements with multilayer coatings. Early EUV lithographic projection optical systems focused on the development of optical systems that project two dimensional image formats. One example of a step and repeat optical system is disclosed in U.S. Pat. No. 5,063,586. The '586 patent discloses coaxial and tilted/decentered configurations with aspheric mirrors which project approximately a 10 mm.times.10 mm image field. The '586 patent system achieves an acceptable resolution of approximately 0.25 .mu.m across the field, but suffers from unacceptably high distortion, on the order of 0.8 .mu.m. The '586 patent optical system is impractical because the mask would have to pre-distorted in order to compensate for the distortion. More advanced step and scan optical systems have been developed due to the unacceptable distortion of the large image fields of step and repeat optical systems. Step and scan systems have inherently less distortion than step and repeat systems due to the reduced field size. The distortion can be readily corrected over the narrow slit width in the direction of scan. Step and scan optical systems typically utilize ring fields. Referring to FIG. 2, in a step and scan optical system an image is projected by the optical system onto the wafer through an arcuate ring field slit 201, which is geometrically described by a ring field radius 203, a ring field width 205 and a length 207. Ring field coverage is limited to 180.degree. in azimuth. One example of a step and scan optical system is disclosed in U.S. Pat. No. 5,315,629. Although the '629 patent optical system has low distortion, the ring field slit width is only 0.5 mm at the wafer. High chief ray angles at mirror M1 make it difficult to widen the ring field width. The 0.5 mm width of the '629 patent limits the speed at which the wafer can be scanned, restricting throughput. Another disadvantage of systems similar to the '629 patent optical system is that it may require the use of graded multilayer coatings on the reflective optics, as opposed to simpler multilayer coatings that have a uniform thickness across the mirror substrate. Uniform thickness multilayer coatings are generally not suitable for high incidence angles when a wide range of incidence angles across an optic are present. FIG. 3 illustrates the potential for non-uniform reflectivity resulting from high and wide ranges of incidence angles from a uniform multilayer optical element 305. In this instance, Beams 301 and 303 have incident angles of 10.degree. and 15.degree., which correspond to multilayer reflectivities of 69% and 40%, respectively. The intensity of reflected beam 309 is less than the intensity of reflected beam 311 because the incidence angle of beam 303 lies in a lower reflectivity region than the incidence angle of beam 301. This difference in the resulting reflectivity creates an apodization in the exit pupil of the imaging system that leads to a loss in line width control in the projected image. Referring again to FIG. 3, if a graded reflective coating is properly applied to optical element 305, the reflectivity at the incidence point of beam 303 is increased so that the reflected beam 309 has an intensity equal to that of beam 311. Although graded reflective optics can address the intensity apodization problem, graded reflective optics are nonetheless undesirable because they are difficult to fabricate and test. Another example of a step and scan optical system is U.S. Pat. No. 5,353,322. The '322 patent discloses 3-mirror and 4-mirror optical systems for EUV projection lithography. An extra fold mirror added to the 3-mirror embodiment creates a 4-mirror system that solves the wafer/mask clearance problem presented by a system with an odd number of reflections. However, this mirror does not provide any reflective power and thus provides no aberration correction. Another drawback of the '322 optical system is that its aperture stop is physically inaccessible. Because these systems have no physically accessible hard aperture stop to define the imaging bundle from each field point in a like manner, the projected imagery could vary substantially across the ring field as the different hard apertures in the system vignette or clip the imaging bundles. This vignetting or clipping can lead to loss of critical dimension (CD) control in the projected image at the wafer. There are a number of other prior art optical systems compatible with EUV wavelength radiation that use reflective optics. These prior art EUV optical systems typically use simple reflective optics which have spherical convex or spherical concave surfaces. The surface of a spherical reflective element is defined by a constant radius of curvature across the surface of the optic. A drawback of all spherical systems is that they can distort projected images by introducing unwanted aberrations (i.e. spherical, coma, astigmatism, Petzval curvature and distortion). These aberrations can be at least partially corrected or even eliminated by using aspheric mirrors. Many prior art EUV optical systems have been designed to minimize static distortion. The disadvantage of optical systems with minimized static distortion is that the dynamic or scanned distortion may not be minimized. Dynamic or scanned distortion is the actual distortion of a projected image in a scanning lithography system and is substantially different than static distortion. In view of the foregoing, there is a need for high resolution optical systems that are compatible with short wavelength radiation, have high numerical apertures, high radiation throughput, use uniform thickness multilayer reflective coating optics, do not require highly aspheric reflective optics, have an accessible aperture stop, and have low dynamic distortion. SUMMARY OF THE INVENTION The present invention is directed to 4-mirror reflective optical systems that have high resolution, high numerical aperture, and balanced distortion. The present invention allows higher device density because resolution is increased. The reflective optics have been configured to improve radiation throughput by improving optical element reflectivity. The optical elements have been configured with radiation beam incidence angles as close as possible to perpendicular. The acceptable ranges of incidence angles have also been minimized to preserve uniform reflectivity and to eliminate the need for graded multilayer optics, which can add significant risk to the system. The inventive optical systems further minimize manufacturing risks by not requiring highly aspheric optical elements. The present invention includes an accessible aperture stop. The present invention also has a balanced centroid distortion curve across the ring field width. More specifically, the centroid distortion levels at the edges of the ring field width are substantially equal and quantitatively higher than the centroid distortion at the center of the ring field width. By balancing the static centroid distortion curve across the ring field width, the dynamic distortion is minimized. Other advantages and features of the present invention will become apparent from a reading of the following description when considered in conjunction with the accompanying drawings.
	description	This application claims the benefit of prior U.S. provisional application Ser. No. 62/095,922, filed Dec. 23, 2014, the contents of which are incorporated by reference. This invention was made with Government support under Cooperative Agreement No. DE-NE0000633 awarded by DOE. The Government has certain rights in this invention. This disclosure generally relates to a light water nuclear reactor and, more particularly, to a self-pressurizing light water reactor (LWR). Light water reactors initiate a nuclear fission reaction to heat a coolant that passes through a core, which contains the nuclear fuel for the reaction. In order to operate correctly, e.g., at the proper pressures within a reactor pressure vessel of the reactor module, a pressurizer and pressurizer heaters are mounted within an upper dome of the reactor pressure vessel of LWRs. Moreover, in both pressurized water reactor (PWR) and boiling water reactor (BWR) versions of LWRs, energy from heated coolant is transferred to generate electrical power. In the case of PWRs, such energy is transferred to a working fluid that circulates in an independent fluid circuit internally and externally to the pressure vessel. In the case of BWRs, such energy in the heated coolant (in the form of radioactive steam) is directly used to power a gas expander, e.g., a turbine, to generate electricity. There is a need, however, for an improved light water reactor that can operate with a condensing steam generator and maintain a reduced reactor pressure. The present disclosure describes a commercial power light water reactor that utilizes circulation (for example, in some implementations it uses natural circulation, not driven by a pump) of a primary coolant at saturation pressure to cool a nuclear core and transfer heat from the core to a secondary coolant through one or more heat exchangers of a condensing steam generator. The secondary coolant, once heated (e.g., to steam, superheated steam or otherwise), can drive power generation equipment, such as steam turbines or otherwise, before being condensed and returned to the one or more heat exchangers. A preferred version of the invention includes a nuclear reactor system (e.g., a nuclear reactor) that includes a power light water reactor (LWR). In some versions, as described more fully below, the LWR utilizes a condensing steam generator onto which a primary coolant (in vapor form) condenses to transfer heat to the secondary coolant. In some versions, the primary coolant may circulate through the LWR at a saturation pressure of the coolant. In some implementations, a top liquid level of the primary coolant, during normal operation of the LWR, is below the condensing steam generator within the reactor. The saturation pressure of the primary coolant may be maintained by a flow of a secondary coolant through the LWR that removes heat from the primary coolant. In some versions, the reactor core 20 is submerged within a liquid primary coolant, such as water. The primary coolant may include boron or other additives; however, other implementations of the LWR may be boron-free. In preferred examples, a liquid level of the liquid primary coolant is located at or just above a top of the core, and below the steam generator. During normal operation, the liquid primary coolant boils in or above the core and vaporizes into vapor primary coolant, which, when heated, rises into a channel formed within the riser positioned above the core. The vapor primary coolant contacts heat exchangers of the steam generator and condenses. In a preferred version, the condensed primary coolant is circulated (e.g., by gravity) down an annulus toward a bottom portion of the reactor vessel. In accordance with some versions, the primary coolant forms a primary coolant circuit that extends from the pool of water in the bottom portion of the reactor pressure vessel, up through the interior of the steam generator (as channeled by the riser), down through a space defined between the steam generator (and/or the riser) and the sidewalls forming the reactor pressure vessel, and finally returning to the pool again at the bottom of the reactor pressure vessel. Various implementations described in this disclosure may include none, one, some, or all of the following features. For example, in some versions of the invention a self-pressurizing LWR may reduce a primary coolant operating pressure to produce superheated steam, which may in turn allow for a reduced reactor pressure vessel thickness for a pressure rating of between about 1,150 psia and about 1,750 psia for a range of operating pressures between about 1,000 psia and 1,550 psia (e.g., 1,650 psia), as vessel thickness is proportional to primary coolant operating pressure. Thus, a cost of the reactor pressure vessel may be reduced. This reduced primary pressure may also result in less stored energy during an accident event when an emergency cooling system actuates, thereby resulting in a reduced peak and design pressures for the containment vessel. As another example, a reduced containment peak pressure may be directly proportional to containment vessel thickness. Thus, a thinner containment vessel may result in cost savings. As another example, the self-pressurizing LWR may utilize a condensing steam generator, which may eliminate (e.g., all or partially) contaminated reactor coolant from exiting the reactor pressure vessel and reaching systems that are typical of steam systems in BWRs. A LWR with a condensing steam generator may have reduced manufacturing costs, as pressure loss of a primary coolant may be reduced in a self-pressurizing LWR. In some examples, the condensing steam generator may be of a variety of shapes to fit within the reactor pressure vessel. For example, the reactor pressure vessel may be shorter and wider, as no significant thermal driving head is needed between the heat source or the core and the heat sink of the condensing steam generator. As a further example, a shorter reactor pressure vessel may significantly reduce seismic accelerations, shorten control rod shafts, reduce a reactor building pool size, reduce the reactor building height, and/or reduce a size of reactor module crane. Further a shorter steam generator and reactor pressure vessel may result in shorter piping and smaller thermal differential expansion, thereby allowing the minimization of welds and inspection requirements. As another example, control systems for the self-pressurizing LWR may be less complex, as pressurizer controls may be eliminated. Furthermore, the self-pressurizing LWR may have reduced fluence on the containment vessel, which can eliminate vessel embrittlement concerns. As a further example, boron may be eliminated (e.g., all or substantially) from a reactor coolant, which may benefit long term operation and reduce costs. The details of one or more implementations of the subject matter described in this specification are set forth in the accompanying drawings and the description below. FIG. 1 is a block diagram illustrating a nuclear reactor system 100 (e.g., a nuclear reactor) that includes a commercial power light water reactor (LWR) 105 that utilizes circulation (e.g., natural) of a primary coolant to cool a nuclear core and transfer heat from the core to a secondary coolant through one or more heat exchangers. The secondary coolant (e.g., water), once heated (e.g., to steam, superheated steam or otherwise), can drive power generation equipment, such as steam turbines or otherwise, before being condensed and returned to the one or more heat exchangers. In some versions, as described more fully below, the LWR 105 utilizes a condensing steam generator 42 onto which the primary coolant (in vapor form) condenses to transfer heat to the secondary coolant. The primary coolant may circulate through the LWR 105 (e.g., by natural convection) at a saturation pressure of the coolant, thereby eliminating or reducing a need for a pressurizer in a top portion (e.g., steam dome) of the LWR 105. In some implementations, a top liquid level 43 of the primary coolant, during normal operation of the LWR 105, is below the condensing steam generator 42 within the reactor. In the illustrated example as in FIG. 1, the top liquid level is below the bottom of the condensing steam generator 42, so that the condensing steam generator is not within the liquid. The saturation pressure of the primary coolant may be maintained by a flow of a secondary coolant (e.g., feedwater) through the LWR 105 that removes heat from the primary coolant. For instance, when heat generated in a core 20 and heat removed by the steam generator 42 are in balance (e.g., approximately equal), the saturation pressure may be maintained. Thus, control of a flow of the secondary coolant (e.g., by pumps, valves, bypass, or otherwise) may be utilized to maintain the balance (e.g., to self-pressurize to a saturation pressure of the primary coolant). With respect to the nuclear reactor system 100, the reactor core 20 is positioned at a bottom portion of a reactor vessel 70 (which, in the illustrated example, is cylinder-shaped or capsule-shaped). Reactor core 20 includes a quantity of nuclear fuel assemblies, or rods (e.g., fissile material that produces, in combination with control rods, a controlled nuclear reaction), and optionally one or more control rods (not shown). In some implementations, nuclear reactor system 100 is designed with passive operating systems (e.g., without a circulation pump for the primary coolant) employing rising heated liquid in the direction of arrow 40 and falling cooled liquid in the direction of arrows 80 to ensure that safe operation of the nuclear reactor 100 is maintained during normal operation or even in an emergency condition without operator intervention or supervision, at least for a period of time that may be predefined or finite. A containment vessel 10 (which, as with the reactor vessel, in the illustrated example is cylinder-shaped or capsule-shaped) surrounds reactor vessel 70. In the illustrated example, the containment vessel is partially or completely submerged in a reactor pool, such as below waterline 90 (which may be at or just below a top surface 35 of the bay 5), within reactor bay 5. The volume between reactor vessel 70 and containment vessel 10 may be partially or completely evacuated to reduce heat transfer from the reactor vessel 70 to the reactor pool. However, in other implementations, the volume between reactor vessel 70 and containment vessel 10 may be at least partially filled with a gas and/or a liquid that increases heat transfer between the reactor and containment vessels. In the illustrated implementation, reactor core 20 is submerged within a liquid primary coolant 80, such as water. In some versions, the primary coolant may include boron or other additives; however, other implementations of the LWR 105 may be boron-free, in that the primary coolant does not include boron (or contains an insignificant amount of boron). A boron-free primary coolant in the LWR 105 may include several advantages. For example, the liquid primary coolant 80 may boil in or just above the core 20 (as described more fully below). Also, cost may be significantly reduced in manufacturing and/or operating the LWR 105. As illustrated, a liquid level 45 of the liquid primary coolant 80 is located at or just above a top of the core 20, and below the steam generator 42. During normal operation, the liquid primary coolant 80 boils in or above the core 20 and vaporizes into vapor primary coolant (represented by arrow 40), which, when heated, rises into channel 30 formed within the riser positioned above the core 20. The vapor primary coolant 40 contacts heat exchangers 50 and 60 of the steam generator 42 and condenses (e.g., changes phase) when in contact with the heat exchangers 50, 60 (e.g., due to a temperature difference between the vapor primary coolant 40 and the secondary coolant in the heat exchangers 50, 60. The condensed primary coolant (e.g., liquid primary coolant 80) is circulated (e.g., by gravity) down an annulus 32 toward a bottom portion of the reactor vessel 70. As illustrated, a liquid level 43 of the liquid primary coolant 80 in the annulus 32 may be slightly above the liquid level 45 but still below the steam generator 42. The condensed primary coolant, when in contact with reactor core 20, is heated and vaporized, which again rises through channel 30. Although heat exchangers 50 and 60 are shown as two distinct elements in FIG. 1, heat exchangers 50 and 60 may represent any number of helical (or other shape) coils that wrap around at least a portion of channel 30. In the illustrated implementation, normal operation of the nuclear reactor module proceeds in a manner wherein boiled or vaporized primary coolant 40 rises through the channel 30 and makes contact with heat exchangers 50 and 60, where it condenses. After condensing, the liquid primary coolant 80 sinks towards the bottom of reactor vessel 70 in a manner that induces a thermal siphoning process. In the example of FIG. 1, primary coolant within reactor vessel 70 remains at a saturation pressure, thus allowing vaporization (e.g., boiling) of the primary coolant in the core 20. In the illustrated implementation, a downcomer region (e.g., annulus 32) between the reflector 15 and the reactor vessel 70 provides a fluid path for the liquid primary coolant 80 to flow between the riser 30 and the reactor vessel 70 from a top end of the vessel 70 and a bottom end of the vessel 70 (e.g., below the core 20). The fluid path channels liquid primary coolant 80 that has yet to be recirculated through the core 20 into convective contact with at least one surface of the reflector 15 in order to cool the reflector 15. In accordance with the above description, the primary coolant forms a primary coolant circuit that extends from the pool of water in the bottom portion of the reactor pressure vessel, up through the interior of the steam generator (as channeled by the riser), down through a space defined between the steam generator (and/or the riser) and the sidewalls forming the reactor pressure vessel, and finally returning to the pool again at the bottom of the reactor pressure vessel. In the illustrated implementation, as secondary coolant (labeled as “feed water”) within heat exchangers 50 and 60 increases in temperature, the secondary coolant may begin to boil. As the feed water within heat exchangers 50 and 60 begins to boil, vaporized feed water (labeled as “steam”) may be used to drive one or more turbines that convert the thermal potential energy of steam into electrical energy. In the illustrated implementation, after condensing, secondary coolant, or feed water, is returned to locations near the base of heat exchangers 50 and 60. The steam is circulated to generate electricity with a turbine 132 and generator 134. For example, the steam may enter the turbine 132 as a high temperature/high pressure superheated vapor (or dry, saturated vapor) to drive the turbine 132 and leave the turbine 132 as a low temperature/low pressure saturated vapor. The generator 134, coupled to the turbine 132, generates electrical power as the turbine 132 rotates. The low temperature/low pressure saturated vapor enters a condenser 136, where it returns to a low temperature/low pressure liquid (feed water) and is circulated by a pump 138 back to the condensing steam generator 42. FIG. 2 illustrates a schematic of an example implementation of a self-pressurizing light water reactor (LWR) 200. In some versions, the LWR 200 may be the same or similar to the LWR 105 shown in FIG. 1. For example, in some versions, the illustrated LWR 200 may include a condensing steam generator on which a primary coolant condenses to transfer heat from the primary coolant to a secondary coolant circulating within the steam generator 230. Further, in some versions, the illustrated LWR 200 may operate (e.g., during normal operation), at a saturation pressure of the primary coolant that is circulated within a reactor pressure vessel of the LWR 200. In some versions, the primary coolant of the LWR 200 may be boron-free (e.g., contain no or negligible amounts of boron or other similar additive). The illustrated example of LWR 200 includes a containment vessel 205 that defines a first volume into which a reactor pressure vessel 210 is positioned. The first volume may be evacuated or contain a fluid, e.g., for transferring heat from the reactor pressure vessel 210 to a heat sink external to the containment vessel 205. A control rod system that includes one or more control rods 250 is positioned near a top 290 of the first volume so that the control rods 250 extend from the first volume, through the reactor pressure vessel 210, and into a second volume defined by the reactor pressure vessel 210. Generally, the control rods 250 may be adjusted (e.g., moved up or down) to control (e.g., start-up, shut-down, or otherwise) operation of the LWR 200. A core 215, comprising one or more nuclear fuel assemblies and a reflector, is positioned on a core support 255 at or near a bottom end 295 of the reactor pressure vessel 255. Generally, the core 215 may be positioned to allow a flow of liquid coolant 270 to circulate through the bottom portion of the reactor pressure vessel 210 and upward through the core 215, as indicated by the arrows 270. A riser 220 extends in the reactor pressure vessel 210 upward from the core 215 through the second volume. As illustrated, an annulus 225 is formed in the second volume that is between the riser 220 and an inner surface of the reactor pressure vessel 210. Liquid coolant 270 may be contained in the annulus 225 to circulate from the annulus 225 to the core 215. In this example, a liquid level 260 of the liquid coolant 270 may be held relatively constant, during normal operation, around the riser 220 between the core 215 and the steam generator 230. The riser 220 extends above the core 215 and up to a steam generator 230, which includes one or more heat exchangers (e.g., tubular, helical, or otherwise). In this example, the steam generator 230 may be a condensing steam generator 230, such that, for instance, during normal operation, the primary coolant experiences a phase change (e.g., from vapor to liquid) on an outer surface of the steam generator 230 to transfer heat from the primary coolant to the secondary coolant. As illustrated, the condensing steam generator 230 includes at least one secondary coolant inlet 235 and at least one secondary cooling outlet 240. In some implementations (and as described more fully below), a feed water supply (as the secondary coolant) may be circulated to the inlet 235, vaporized (e.g., from heat transferred to the feed water from the primary coolant), and circulated from the outlet 240 as steam. The steam secondary coolant may then be circulated to an electrical power generation system (e.g., as described in FIG. 1). In this example, the primary coolant circulates in a flow path that is fully contained in the reactor pressure vessel 210 and fluidly isolated from the secondary coolant. The secondary coolant circulates in a flow path that breaches the LWR 200 (e.g., both the containment vessel 205 and the reactor pressure vessel 210) from an exterior location (e.g., where the power generation system is located) but is still fluidly isolated from the primary coolant. Thus, no radioactive coolant (e.g., the primary coolant) escapes the LWR 200 (during intended normal operation). A portion of the second volume (i.e., defined within the reactor pressure vessel 210) that is located above the condensing steam generator 230 includes a saturated steam dome 245. As illustrated, this portion of the volume of the reactor pressure vessel 210 may be relatively free of structure (e.g., may only include the control rods 250 extending therethrough), such as a pressurizer. For instance, in this example implementation, the LWR 200 does not include a pressurizer (e.g., baffles and/or heaters) mounted in the saturated steam dome 245. Thus, a height of the LWR 200 may be reduced as compared to conventional pressurized water reactors. Indeed, along with the use of the condensing steam generator 230, the absence of a pressurizer may allow for the LWR 200 to be shorter than conventional pressurized water reactors. FIG. 3 is a flowchart that describes an example method 300 for producing electrical power from a nuclear reactor power module. In some implementations, method 300 may describe a normal operating mode for the LWR 200 shown in FIG. 2. Method 300 may begin at step 302, which includes flowing a primary coolant liquid at saturation pressure through a core that comprises a plurality of nuclear fuel assemblies. With reference also to FIG. 2, the primary coolant liquid 270, at saturation pressure, is circulated through the core 215, where heat from nuclear fuel assemblies may be transferred to the primary coolant liquid 270. Method 300 may also include step 304, which includes boiling the flow of primary coolant liquid with heat from the plurality of nuclear fuel assemblies to form a primary coolant vapor. Here, the primary coolant liquid 270 at saturation receives heat from the nuclear fuel assemblies and changes phase (e.g., boils) to a flow of primary coolant vapor 280. In this example, a liquid line 265, maintained at or above the core 215, defines a boiling surface of the primary coolant. Method 300 may also include step 306, which includes circulating the primary coolant vapor from above the core through a riser. In this step, the primary coolant vapor 280 circulates (e.g., naturally due to temperature/pressure differences) from the liquid line 265, through the riser 220, and toward the condensing steam generator 230. Notably, in this example of the LWR 200, no pumps or other mechanical circulation means are used to circulate primary coolant within the reactor pressure vessel 210. Method 300 may also include step 308, which includes transferring heat from the primary coolant vapor to a working fluid in the steam generator through a phase change of the primary coolant vapor to the primary coolant liquid. The primary coolant vapor 280 circulates into contact with an exterior surface of the condensing steam generator 230 (e.g., one or more heat exchangers), through which circulates the secondary coolant from the inlet 235 (e.g., feed water). Based on a temperature difference between the primary coolant vapor 280 and the secondary coolant feed water (e.g., where the secondary coolant feed water is below a condensation temperature of the primary coolant vapor 280), phase change of the primary coolant vapor 280 begins as heat is transferred to the feed water. Method 300 may also include step 310, which includes condensing the primary coolant vapor on a steam generator positioned adjacent the riser to form the primary coolant liquid. As more heat is transferred from the primary coolant vapor 280 to the secondary coolant feed water, the primary coolant vapor 280 near or in contact with the condensing steam generator 230 condenses to the primary coolant liquid 270. Method 300 may also include step 312, which includes circulating the primary coolant liquid, through an annulus defined between the riser and a reactor pressure vessel, to the core. The primary coolant liquid 270 near or in contact with the condensing steam generator 230 condenses and circulates (e.g., by gravity) through the annulus 225 toward the core 215 (e.g., toward a bottom end of the reactor pressure vessel 210). Method 300 may also include step 314, which includes circulating the primary coolant liquid through the annulus to a primary coolant pool within the annulus below the steam generator. In this example implementation, a primary coolant pool 260 is enclosed within the annulus 225 and may be maintained between the core 215 and the condensing steam generator 230, as liquid 270 continually circulates through the core 215 and vapor 280 continually circulates to the pool 260. While the preferred embodiment of the invention has been illustrated and described, as noted above, many changes can be made without departing from the spirit and scope of the invention. Accordingly, the scope of the invention is not limited by the disclosure of the preferred embodiment. Instead, the invention should be determined entirely by reference to the claims that follow.
053135075	claims	1. An apparatus for attaching a key member to a nuclear fuel assembly grid and detaching the same therefrom, said key member having a longitudinal axis and being adapted to be detachably attached to the grid by rotating the same about the longitudinal axis, said apparatus comprising: (a) supply and recovery means for supplying the key member to a prescribed position adjacent to the grid and recovering the same; (b) inserting and removing means disposed between said supply and recovery means and said grid for inserting the key member supplied from said supply and recovery means into the grid and removing the key member from the grid to recover the same to said supply and recovery means; and (c) rotating means disposed adjacent to said inserting and removing means for rotating the key member inserted in the grid in a prescribed direction about said longitudinal axis to attach the same to the grid and rotating the same in a direction opposite to said prescribed direction to detach the same from the grid. 2. An apparatus according to claim 1, wherein said inserting and removing means includes an opposed pair of rollers disposed parallel to each other so as to define a space therebetween, and drive means operably connected to said rollers for rotating the rollers in reverse directions, said space between said rollers being such that when said rollers are rotated, said rollers engage the key member to move the same toward and away from the grid. 3. An apparatus according to claim 2, wherein said inserting and removing means further includes discharging means for moving the key member to bring the same into the space between said rollers. 4. An apparatus according to claim 2, wherein said rollers are disposed movable toward and away from each other between a proximity position, in which the rollers engage the key member to move the same, and a distal position in which the rollers do not engage the key member. 5. An apparatus according to claim 4, wherein said inserting and removing means further includes drive means connected to said rollers for moving said rollers between said proximity position and said distal position. 6. An apparatus according to claim 1, wherein said rotating means includes a worm wheel having an aperture formed therethrough for receiving the key member, a worm gear held in engaged with said worm wheel, and an actuator for rotating said worm gear. 7. An apparatus according to claim 1, wherein said rotating means includes a holding member having an aperture formed therethrough for receiving the key member, a link mechanism connected to said holding member, and an actuator for rotating said holding member through said link mechanism.
	summary
	claims	1. An ion implantation device that implants ions in a substrate,wherein the ion implantation device has:a chamber including a cover having a small cylindrical through-hole;an irradiation means that radiates ions;a retention means that retains at least one substrate;a detection means that detects, in a noncontact state, temperature information pertaining to the temperature of a substrate retained by the aforementioned retention means, wherein the detection means comprises a thermopile located in said small cylindrical through-hole;a supply means that supplies a cooling medium to the aforementioned retention means to enable heat exchange for the substrate retained by the aforementioned retention means;and a control means that calculates the surface temperature of the substrate retained by the aforementioned retention means based on the temperature information detected by the aforementioned detection means and determines whether the calculated substrate surface temperature is within a permissible temperature range. 2. The ion implantation device recorded in claim 1, wherein the aforementioned control means halts the radiation of ions by the aforementioned irradiation means when it is determined that the aforementioned calculated substrate surface temperature is outside of the aforementioned permissible temperature range. 3. The ion implantation device recorded in claim 1, wherein the aforementioned permissible temperature range is a temperature range permitted with the ion implantation process and the aforementioned control means records information related to the permissible temperature range in a memory. 4. The ion implantation device recorded in claim 1, wherein the aforementioned control means controls the aforementioned supply means based on the aforementioned calculated substrate surface temperature. 5. The ion implantation device recorded in claim 4, wherein the aforementioned control means controls at least one of: the temperature of the cooling medium or the amount of cooling medium supplied by the aforementioned supply means. 6. The ion implantation device recorded in claim 1, wherein the aforementioned control means records in a memory a correlation between the temperature information for a dummy silicon substrate and the surface temperature thereof, and the aforementioned control means calculates the surface temperature of a process silicon substrate based on the temperature information for the process silicon substrate and the aforementioned correlation. 7. The ion implantation device recorded in claim 6, wherein the aforementioned detection means includes an infrared sensor and the aforementioned temperature information is a voltage generated by the aforementioned infrared sensor according to the heat radiated from the substrate. 8. The ion implantation device recorded in claim 6, wherein the surface temperature of the dummy silicon substrate included in the aforementioned correlation is a value observed on a thermo label attached to the surface of a dummy silicon substrate. 9. The ion implantation device recorded in claim 1, wherein the aforementioned retention means includes a rotatable disk that retains multiple substrates and is used for batch processing, and the aforementioned disk exchanges heat by means of a cooling medium supplied by the aforementioned supply means. 10. The ion implantation device recorded in claim 1, wherein the aforementioned retention means includes a retention member that retains one substrate and is used for single-substrate processing, and the aforementioned retention member exchanges heat by means of a cooling medium supplied by the aforementioned supply means. 11. An ion implantation device that implants ions in a substrate, wherein the ion implantation device has:a chamber including a cover having a small cylindrical through-hole;an irradiation unit that radiates ions;a retainer that retains at least one substrate;a sensor that detects, in a noncontact state, temperature information pertaining to the temperature of the at least one substrate retained by the retainer, wherein the sensor comprises a thermopile located in said small cylindrical through-hole;a cooling medium supply unit that supplies a cooling medium to the retainer to enable heat exchange for the substrate;and a control unit that calculates the surface temperature of the at least one substrate based on the temperature information detected by the sensor and determines whether the calculated substrate surface temperature is within a permissible temperature range. 12. The ion implantation device recorded in claim 11, wherein the control unit halts the radiation of ions by the irradiation unit when it is determined that the calculated substrate surface temperature is outside of the permissible temperature range. 13. The ion implantation device recorded in claim 11, wherein the permissible temperature range is a temperature range permitted with the ion implantation process and the control unit records information related to the permissible temperature range in a memory. 14. The ion implantation device recorded in claim 11, wherein the control unit controls the cooling medium supply unit based on the calculated substrate surface temperature. 15. The ion implantation device recorded in claim 14, wherein the control unit controls at least one of: the temperature of the cooling medium or the amount of cooling medium supplied by the cooling medium supply unit. 16. The ion implantation device recorded in claim 14, wherein the control unit records in a memory a correlation between the temperature information for a dummy silicon substrate and the surface temperature thereof, and the control unit calculates the surface temperature of a process silicon substrate based on the temperature information for the process silicon substrate and said correlation. 17. The ion implantation device recorded in claim 16, wherein the sensor an infrared sensor and the aforementioned temperature information is a voltage generated by the infrared sensor according to the heat radiated from the substrate. 18. The ion implantation device recorded in claim 17, wherein the surface temperature of the dummy silicon substrate included in the correlation is a value observed on a thermo label attached to the surface of a dummy silicon substrate. 19. The ion implantation device recorded in claim 18, wherein the retainer includes a rotatable disk that retains multiple substrates and is used for batch processing, and the disk exchanges heat by means of a cooling medium supplied by the cooling medium supply unit. 20. The ion implantation device recorded in claim 19, wherein the retainer includes a retention member that retains one substrate and is used for single-substrate processing, and the retention member exchanges heat by means of a cooling medium supplied by the cooling medium supply unit.
	summary
	abstract	The present invention claims UV detectable (λ>210 nm) potassium [18F]fluoride diaryl- and aryl-fused [2.2.2]cryptate complexes suitable for performing radio-labeling reactions to generate [18F] fluorinated species.
051046091	summary	BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an assembly method for a nuclear fuel assembly which simplifies insertion of a plurality of fuel rods into a plurality of grid cells during the assembly of the nuclear fuel assembly. 2. Description of the Prior Art A construction as shown in FIG. 24 of the attached drawings is known as an example of a nuclear fuel assembly which is mounted in a pressurized water reactor. In FIG. 24, top and bottom nozzles 1 and 2 are vertically spaced and arranged in facing relation to each other. A plurality of control-rod guide thimbles 3 are fixed to and extend between the top and bottom nozzles 1 and 2. A plurality of grids 4 are mounted at intermediate portions of the respective control-rod guide thimbles 3 in a vertically spaced relation to each other. As shown in FIG. 25, each of the grids 4 is formed such that a plurality of straps 5, each in the form of a thin plate, are assembled perpendicularly to each other into a grid by a mutual fitting of slits which are formed in the straps 5 in longitudinally equidistantly spaced relation to each other. A plurality of grid cells 6 are defined in each of the grids 4. A pair of dimples 8 and a pair of springs 9 for supporting a fuel rod 7 are mounted on the wall surface of each of the grid cells 6 in facing relation to each other. The fuel rod 7 inserted in the grid cell 6 is supported by being pushed against the dimples 8 by the springs 9. An assembly method for the nuclear fuel assembly constructed above will next be described. First, the grids 4 are arranged in a spaced relation to each other with a predetermined spacing. Then the control-rod guide thimbles 3 are inserted into and fixed to a part of the corresponding grid cells 6 of each of the grids 4. Subsequently, the fuel rods 7 are inserted into corresponding grid cells 6 in each of the grids 4 which are supported by the control-rod guide thimbles 3, with the fuel rod 7 in sliding contact with the dimples 8 and the springs 9. In this manner, the fuel rods 7 are held in fixed arrangement in the grid cells 6 by the dimples 8 and the springs 9. After insertion of all of the fuel rods 7, the top and bottom nozzles 1 and 2 are fixed to respective opposite ends of the control-rod guide thimbles 3. A problem with the aforesaid assembling method of the nuclear fuel assembly is that when the fuel rods 7 are inserted into the respective grid cells 6 in the grids 4, the outer periphery of each of the fuel rods 7 is clamped between the dimples 8 and the springs 9, and insertion of the fuel rod 7 into the corresponding grid cells 6 is restricted by the resilient force of the springs 9. Thus, difficulties arise in the insertion operation detracting from the working or operating efficiency. SUMMARY OF THE INVENTION It is therefore an object of the invention to provide an assembling method for a nuclear fuel assembly, in which, when each of a plurality of fuel rods is inserted into a corresponding one of a plurality of grid cells, this can be done smoothly and easily, and after insertion of the fuel rod, the fuel rod is reliably supported. It is another object of the invention to provide a grid for the above-mentioned nuclear fuel assembly. To achieve these objects, according to the invention, there is provided an assembly method for a nuclear fuel assembly, comprising the steps of: preparing at least a first grid member with springs, wherein the springs are provided on wall sections of the first grid member with springs, and at least a second grid member with dimples, in which the dimples are provided on wall sections of the second grid member; arranging the first grid member with springs and the second grid member with dimples face to face such that a plurality of grid cells of the first grid member with springs and a plurality of grid cells of the second grid member with dimples communicate with each other and that said dimples and said springs are disposed on planes which are opposed to each other; inserting fuel rods respectively into the grid cells of the first grid member with springs and the second grid member with dimples, under such a condition that the springs and the dimples are shifted relative to each other in such a direction that the springs and the dimples move away from each other; subsequently, moving at least one of said first grid member with springs and said second grid member with dimples such that the grid cells in the first grid member with springs and the grid cells in the second grid member with dimples are in alignment with each other; and connecting the first grid member and the second grid member with dimples to each other. According to the invention, there is also provided a grid for a nuclear fuel assembly, comprising: a first grid member with springs having a plurality of straps each in the form of a thin plate, the straps intersecting each other to form a plurality of grid cells; and a second grid member with dimples having a plurality of straps each in the form of a thin plate, the straps of the first grid member with dimples intersecting each other to form a plurality of grid cells, that plane on which the dimples of the second grid member with dimples are disposed being opposed to that plane on which the springs of said grid member with springs are disposed; the first grid member with springs and the second grid member with dimples being connected to each other such that the grid cells in the first grid member with springs and the grid cells in the second grid member with dimples are in alignment with each other. In the assembling method of the nuclear fuel assembly and the grid for the nuclear fuel assembly, the fuel rods are inserted respectively into the grid cells in such a condition that the grid member with springs and the grid members with dimples are shifted relative to each other. With such an arrangement, the difficulty of insertion of the fuel rods with the fuel rods in contact with the springs and the dimples is removed. Thus, it is possible to easily insert the fuel rods into the grid cells. Furthermore, after insertion of the fuel rods, the grid cells in the grid member with springs and the grid cells in the grid member with dimples are aligned with each other. Thus, it is possible to reliably support the fuel rods by the springs and the dimples. A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:
053176111	summary	BACKGROUND 1. Field of the Invention This invention relates to fuel elements and assemblies thereof for nuclear thermal engines. 2. Background of the Invention Nuclear thermal engines utilize fissionable material to heat a propellant, typically hydrogen, which is discharged through a nozzle to generate thrust. A design objective in such engines is to achieve a high thrust-to-weight and specific impulse. This requires a core design featuring a compact configuration with high heat transfer area, a high coefficient of heat transfer and optimum flow rate and flow velocity. An early design for nuclear thermal engines used prismatic fuel elements in the form of hexagonal rods stacked side by side with a pattern of longitudinal bores in each rod through which propellant flowed axially. Such fuel elements were subject to stress induced cracking between the bores as a result of the very high thermal stresses occurring during operation. An experimental particle bed fuel element utilizes small fuel beads packed in an annular support. Propellant flows radially inward through a porous peripheral wall, the particle bed and a porous annular inner wall, and then flows axially out through a central passage. These particle bed fuel elements can develop hot spots causing melting of the fuel beads. Thus, while the particle bed fuel elements have a high heat transfer capability, it is difficult to control propellant flow through them and they have poor mechanical stability. Another proposed design utilizes flat annular plates with radial grooves or holes for propellant flow radially inward to a central discharge passage. However, the very high temperature gradient, for example 100.degree. K at the periphery and 3000.degree. K at the central discharge passage, produces severe stress cracking in the flat, annular plates. A suggestion has been made to utilize fueled truncated conical shells seated on one another with grooves in the contacting confronting shell surfaces for coolant flow. See, also, U.S. Pat. No. 3,150,054 to Fox, which shows a truncated conical reactor design. There is a need therefore for improved fuel elements and assemblies for nuclear thermal engines. SUMMARY OF THE INVENTION It is the primary object of the invention to provide an improved fuel element and assembly for nuclear thermal engines, and in particular for nuclear thermal rocket propulsion engines. It is a more particular object of the invention to provide such improved fuel elements and assemblies having high heat transfer area, high power density without hot spots, and in which the flow is readily controllable. It is also an object of the invention to provide such improved fuel elements and assemblies which are modular so that different engines with different thrust ratings can be easily fabricated. It is another object of the invention to provide such improved fuel elements and assemblies which can be constructed with existing technology. These and other objects are realized in fuel elements of the type having a truncated conical shell tapering inward from a base, typically at an angle of between about 30.degree. to 60.degree. and preferably about 45.degree. to 60.degree.. Conical shell fuel elements embodying the present invention have an unfueled annular lip extends radially outward at the base of the truncated conical shell, and has radial passages through which propellant flows inwardly. The annular lips of multiple fuel elements stack one on top of another to form a stack of fuel elements with frusto-conical flow passages between adjacent elements Angularly spaced, radially extending ribs on one surface, preferably the outer surface, of the truncated conical shells of the fuel elements form propellant flow channels in the frusto-conical flow passages between elements While not sized to contact the adjacent fuel element in the stack, the ribs maintain the spacing between elements distorted by the heat. The truncated open ends of the shells are free to expand and contract independently without creating significant stresses. The stack of truncated conical shell fuel elements is supported in a fuel assembly which comprises a cylindrical housing with a central inlet opening at one end and a central outlet at the opposite end. The stack of fuel elements is mounted in the housing with an annular flow distribution channel between the periphery of the stack and the housing. A central baffle spaced from the inlet opening deflects propellant entering through the inlet opening to the annular flow distribution channel through which it flows axially and then radially inward through the passages in the lips, over the truncated conical shells through the channels formed by the ribs, and then axially out through the centers of the truncated conical shells and the outlet opening. An annular spring maintains alignment of the stack of fuel elements and takes up all axial tolerances in the stack of fuel elements. When mounted at the inlet end, this annular spring has openings through which propellant passes axially into the annular flow distribution channel.
046506373	abstract	A method and apparatus for identifying those fuel rods (32) of a multiple-rod nuclear fuel assembly (30) which contain leaks, are described. The longitudinal position of the leak in the fuel assembly is determined by moving a first test probe (62) longitudinally along the length of the fuel assembly while drawing coolant surrounding the fuel rods into the probe and sampling the radioactive product content of such coolant. The exact position of the leaking fuel rod is then determined by using second (63) and third (64) test probes to logically subdivide the fuel rods of the fuel assembly at such longitudinal position into successively smaller groups while sampling the radioactive content of coolant surrounding the smaller rod groups, until the leaking fuel rod is isolated. A test probe configuration (60) for subdividing and isolating selective groups of the fuel rods for the coolant sampling is disclosed. The test probe assembly includes a plurality of test probes (62, 63, 64) each having a pair of opposed baffle members (62.1, 62.2) secured at one end to a collector (62.3) to define a volumetric test zone (T). The baffles are configured for slidable insertion between adjacent rows of the fuel rods. Means (68, 69) for drawing liquid coolant into the collector, and probe positioning means (66, 67) are also disclosed.
	summary
	abstract	The disclosure relates to a method for manufacturing an object with miniaturized structures. The method involves processing the object by supplying reaction gas during concurrent directing an electron beam onto a location to be processed, to deposit material or ablate material; and inspecting the object by scanning the surface of the object with an electron beam and leading generated backscattered electrons and secondary electrons to an energy selector, reflecting the secondary electrons from the energy selector, detecting the backscattered electrons passing the energy selector and generating an electron microscopic image of the scanned region in dependence on the detected backscattered electrons; and examining the generated electron microscopic image and deciding whether further depositing or ablating of material should be carried out. The disclosure also relates to an electron microscope and a processing system which are adapted for performing the method.
	summary
	description	This application claims the benefit of French Patent Application No. 1350165, filed on Jan. 9, 2013, in the French National Institute of Industrial Property, the entire contents of which is incorporated herein by reference. The invention relates to the treatment of radioactive waste resulting from the operation of nuclear power plants. It more particularly relates to the treatment of carbonaceous waste, particularly graphite used as a material to absorb neutrons in the sleeves around a reactor. The graphite can be treated by combustion and/or by steam reforming. A more general proposal here is a treatment from the extraction of the graphite irradiated in the reactor to the treatment of the gases emitted (by combustion or steam reforming the graphite), all while providing the treatments necessary for conditioning the secondary waste resulting from the overall treatment. The choice of medium for transporting the graphite to the graphite treatment reactor is an important point at this stage because the carrier medium determines the parameters that must be adapted for later treatment of the effluents collected (typically concentrated chlorine 36 (36Cl), carbon 14 (14C), and tritium (3H)), for their subsequent capture or mineralization in order to limit their release into the environment as much as possible. In one possible embodiment, the graphite as such is treated according to the method described in document FR-2943167, which also describes the collection and processing of effluents. However, the best possible medium for transporting the graphite remains to be determined. The present invention aims to improve the situation. For this purpose it proposes a method for treating carbonaceous radioactive waste, comprising the delivery of waste to one or more radioactive isotope separation stations, said isotopes being among at least carbon 14, chlorine 36, and tritium. In one characteristic of the invention, the delivery to each of the stations occurs in wet form. It has been found in the studies and tests of the Applicant that water is a preferred vector for conveying the waste from the entrance of a waste treatment installation to the radioactive isotope separation stations, or even to their conditioning (for example 14C conditioning), according to embodiments presented below in the detailed description. In one embodiment, specific separation stations are provided for each element among the carbon 14, chlorine 36, and tritium, as well as delivery in wet form to each of these stations. This embodiment thus proposes a clearly defined separation for the recovery of chlorine 36 on the one hand and tritium on the other, and achieves this due to the routing in wet form. In one practical implementation, the waste is crushed and mixed with water for delivery in slurry form, before a first isotopic separation, for example separation of the chlorine 36. More particularly, the waste is mixed with water to form a slurry, then mechanically filtered and dried. The drying is preferably conducted by a mild increase of temperature (less than 1000° C. for example) to avoid releasing radionuclides other than chlorine 36 (the other radionuclides 3H, 14C being released in later steps). The water issuing from this drying then contains all or part of the chlorine 36 initially present in the waste prior to drying. In one embodiment, the tritium separation occurs after the chlorine 36 separation. The waste is calcined by roasting, then washed. The water recovered from the wash then contains all or part of the tritium initially present in the waste prior to roasting. In one embodiment, the chlorine 36 and tritium separations precede the treatment of the carbon 14, with the chlorine 36 and tritium being separated from the rest of the carbonaceous waste preferably by leaching. In one embodiment where at least a part of the waste is calcined by roasting, the waste resulting from the roasting is oxidized to carbon dioxide form for dissolution in the conveying water. In one embodiment, carbon 14, oxidized to carbon dioxide form, can then be treated by a carbonation reaction in order to be solidified and stored in solid form. The carbonaceous waste may initially contain graphite. However, the invention applies to other types of carbonaceous waste, such as resins for example. The invention also relates to an installation for treating carbonaceous radioactive waste (an example is illustrated in FIG. 1, which is discussed below). The installation comprises one or more radioactive isotope separation stations, said isotopes being among at least carbon 14, chlorine 36, and tritium, as well as means of delivering the waste to said stations. In one characteristic of the invention, the means of delivery are supplied with water in order to route the wastes in wet form. The treatment installation comprises, for example, supplies of additional water (such as W in FIG. 1, or a supply of water for the conversion into slurry SL, as described below). According to the initiated tests, three possibilities can be envisaged for a medium for collecting carbonaceous waste: a transfer in water, a transfer in gaseous medium in dilute phase, a transfer in gaseous medium and in dense phase. The following table summarizes the advantages and disadvantages related to each technique. WaterPneumaticPneumatic(aqueous slurryDilute phaseDense phasecomposed of(using nitrogen as carrier(using nitrogen as carriergraphite in water)gas)gas)DesignSimpleSimplerMore complexReliability andSimpleEasyMore complexcontrolCost of investmentLowLow, but can increaseGreater than in dilutedue to a need for a highphasecapacity nitrogen (N2)installationCost of operationLowHigh, due to the largeModerate, becauseamount of N2 gassmaller amounts ofrequiredgaseous N2Secondary wasteNeed to treatMinimalMinimalthe volume ofTransferring dryTransferring drywastewater forproduct can eliminateproduct can eliminatetransferring thehaving to dry thehaving to dry thegraphiteproduct (eliminatesproduct (eliminatesdryer and tank A)dryer and tank A)SafetyAcceptableOperates underNot sure of vacuumOperates atvacuumconditionspositiveAbrasion of graphiteCan operate underpressureparticles at high speedpositive pressureproduces dustNeed for safetycontrols due to thedust In the last row of the above table, “positive pressure” is understood to mean a pressure greater than atmospheric pressure, and “vacuum conditions” is understood to mean a pressure lower than atmospheric pressure. Thus, confinement may require some design measures under certain conditions (or an additional confinement barrier). In fact, in a dense pneumatic phase, as with water, it is preferable to be able to pump the graphite to route it. From this study, it is evident that the “water” medium is the choice to be made for all transfers of carbonaceous waste such as irradiated graphite. This medium offers the best guarantees in terms of confinement and radioprotection. In addition, it allows easier management of the interfaces between graphite treatment reactors. According to another result from the study, about 30% (and more generally, a possible range of between 20 and 40%) by weight of graphite in water (as carrier medium) is optimum. A general diagram of the entire treatment in the sense of the invention is represented in FIG. 1. First we will refer to FIG. 1, in which a slurry SL, which is a mixture of graphite and water (approximately 30% graphite) resulting from crushing the graphite in water, is delivered to a mechanical separation station 1, where for example it is separated by filtering with centrifugation. Exiting the station 1, a proportion of 90% wet graphite WG is then brought to a dryer 3, while the waste water WW issuing from the mechanical separation station 1 is brought to an isotope filter 2, for example an ion exchanger. The clean water CW filtered in this way can, for example, be fed back into a water supply circuit of a waste treatment installation as shown in FIG. 1. Exiting from the dryer 3, the water vapor produced from the drying contains most of the chlorine 36 (radioactive isotope) that was initially present in the graphite to be treated. The water vapor Cl containing this isotope 36Cl is first sent to a condenser 4 for liquefaction into water WCl containing chlorine 36, and is then stored in a tank A (at station 5), to await specific treatment of the chlorine 36. The dry graphite DG issuing from the dryer 3 is sent to a heat treatment station 6 where it is roasted. The roasting treatment may be according to the teachings disclosed in document FR 12 60282. For this purpose, there are controlled injections of gases such as hydrogen, carbon monoxide, and carbon dioxide, as well as water vapor. Thus a first high temperature heat treatment (1000-1500° C.) with injection of water vapor can be applied, followed by a second lower heat treatment (800-1200° C.) to utilize the Boudouard reaction with a controlled injection of CO and/or CO2. Such heat treatment sequentially releases first the 14C isotope, then the 12C isotope, in oxide form. Thus the first off-gases OGC from the calcination at station 6 essentially contain carbon 14 (radioactive isotope) that should be treated as secondary waste. In one example embodiment, oxidation of any CO present at the exit from station 6 is conducted at station 7 in order to obtain, preferably, CO2, which is more soluble in water than CO, as we will see below. After exiting the cooler 8, a filter 9 collects the smallest solid particles (“fines”) in order to reinject them into the heat treatment station 6. The residue issuing from the filtration is soaked and washed with additional water W at station 10 in order to collect the tritium (3H isotope of hydrogen). In addition, there can be a demister 11 and a condenser 12 to collect the water loaded with tritium in storage tank B (station 13), to await specific treatment of the tritium 3H. The residual gas issuing from the condenser 12 primarily contains only carbon monoxide or dioxide COx. It can then be sent to a station with absorption 14 and degassing 15 columns. The resulting off-gases OGT are thus treated and the residue from this treatment essentially comprises pure CO2, containing most of the 14C issuing from the graphite. This last can then be treated at a station 16, for example by being solidified by carbonation reaction (into the form CaCO3). FIG. 2 summarizes the main steps of the treatment, as follows. In step S1, a graphite slurry, resulting from crushing graphite in water, is obtained and is transferred by pipes to an installation comprising a heat treatment tank, for a roasting phase. In order to be transportable, this slurry contains about 30% graphite and the rest is water. Step S2 then consists of a first separation (by filtration and/or centrifugation) of the graphite from the water contained in the slurry. Between 5 and 10% w/w of the water remains with the graphite at the end of this step S2. In step S3, the extracted water is filtered. For this purpose, it is mechanically sent to a reactor building for treatment, for example by water filtration means (conventionally used during the dismantling of UNGG caissons). Another means (reference 2 in FIG. 1) can be an autonomous installation of ion exchange resins and filters for performing this filtration. In step S4, the wet graphite is then dried in a dryer at high temperature (between 400° C. and 600° C.) in order to eliminate the residual water. The graphite is preferably dry in order to achieve perfect control of oxidation conditions during the graphite heat treatment phase. The drying temperature is carefully chosen in order to dry the graphite without releasing too many radionuclides during this phase. However, between 400 and 600° C., some of the chlorine 36 is inevitably released with the generated vapor. This is collected in tank ‘A’ of FIG. 1. The proportion of 36Cl released can reach 90% here, and that of the 3H can reach 5%, during this phase. Treatment of the water contained in this tank ‘A’ can be achieved using ion exchange resins in order to capture the 36Cl in step S5. It is possible to use the same water filtration system already present at the site for dismantling the internal elements of the reactor, or to add a dedicated resin-based purification system. Tritium can be stored to allow it to decay on site in dedicated tanks, or trapped on metal hydrides, or recycled for other industrial uses. Preferably, the resins containing chlorine 36 are destined for deep storage. In step S6, the dry graphite is loaded into the calcination installation. This calcination installation and the gases used in it are described in document FR-12 60282. For example this involves heat treatment by roasting, which advantageously obtains the following performances: eliminating the chlorine 36 which was not eliminated during drying (the remaining 10%), release of 95% of the tritium (remaining residual) and the carbon 14, for an associated mass loss of only 5%. It should be noted here that one can make use of catalysts (based for example on special metals such as the noble metals platinum, palladium, etc.) to be combined with graphite in powder form in order to improve and encourage oxidation, in a general manner, in the heat treatment stations (in the roaster in this case). Step S7 concerns the treatment of the generated off-gases. First, they enter a catalytic oxidation device in order to convert the carbon monoxide CO into carbon dioxide CO2. Next the stream of off-gases is cooled, then filtered. Any solid elements present in the off-gases are filtered from the stream and returned to the calcination installation. Step S8 concerns the collection of effluents. The cooled off-gases are then wetted and washed (reverse flow). The vapor that was introduced into the installation then condenses. The tritium and chlorine 36 are eliminated here (step S9). The collected water is transferred to tank ‘B’. This tank then contains the major portion of the tritium and the remainder of the chlorine 36 (10% remaining after drying the graphite). It also contains a small amount of 14C originating from the absorption of CO2 in water. Catalytic oxidation of CO is preferably used here because CO2 is more soluble in water. The treatment for the 36Cl and 3H contained in tank ‘B’ is similar to the treatment for the 36Cl and 3H contained in tank ‘A’ (step S4 above). For example, CO2 at 9.25 10−3 TBQ can be dissolved in 430 m3 of water, while only 1.85 104 for CO can be dissolved in the same amount of water (see solubility curves in FIGS. 3A and 3B). The temperature of these liquids (primarily water but also a mixture with a small amount of sodium hydroxide NaOH in order to improve the CO2 elimination described below) is about 40° C. Elimination of the CO2 containing most of the 14C is conducted in step S10 in the off-gases issuing from the collection of effluents in step S8. The off-gases then circulate to a CO2 elimination system, based for example on a chemical absorption technique, generally using a type of amine to capture the CO2. The absorption tank provides a means of bringing the gas in contact with a chemical solvent, generally an organic amine, which absorbs most of the CO2 by reacting to form a bound compound. The solvent, rich in CO2, is then transferred to another vessel (the degassing column 15 of FIG. 1) where it is heated with steam to reverse the CO2 absorption reactions. The CO2 released in the degassing column can be collected and compressed for storage or to form a solid residue after the mineralization reactions in step S11 (for example forming solid carbonate CaCO3). Recovery levels for the CO2 that exceed 95% can be obtained using current techniques. If needed, more sophisticated solutions of absorbents could be used to improve this ratio. In the following table, a capture rate of 95% is assumed, which means that a fraction (2.25 TBq per year of 14C) exits the system in the off-gases treated as described above. A mass loss related to the entire treatment that is barely above 5% is achieved. The main streams and the inventory of the radionuclides in each stream that must be solidified or treated in order to eliminate them are given in the following table: T/Yr36Cl TBq/Yr3H TBq/Yr14C TBq/YrCalcined950.000.004.755.00graphiteStorage tank233.330.452.500.00A - LiquidsStorage tank431.500.0542.759.25E−03B - LiquidsCompressed3755.760.000.0042.74 CO2 FIGS. 3A and 3B compare the solubility in water of CO to that of CO2, showing in particular that carbon dioxide is much more soluble in water than carbon monoxide, which offers water as a vector of choice for treating carbonaceous waste and particularly graphite, in its oxidized form CO2. The solubility of CO and CO2 in water can then be used as providing an approximation of the amount of C14O2 ultimately absorbed in the water at the end of the treatment. Compressed CO2 can then be mineralized by conventional techniques, for example into carbonates (typically CaCO3) or carbides (for example into silicon carbide SiC), or recycled for use in industry or health care (for hospital examinations for example, as the developer in medical imaging). The example represented in FIG. 1 uses the option of treating the carbon 14 in the form of carbon dioxide CO2. In a first embodiment, this solution may be preferred because of potential safety issues with CO which can generate additional costs and complexity. By converting the CO into CO2 as soon as it exits the roaster, a major problem related to potential hazards concerning safety, explosion, poisoning, or radiotoxicity of the gaseous CO is avoided. The presence of CO as a gas requires a large number of tests which increases the treatment cost. The gas when it exits the treatment illustrated in FIG. 1 thus contains pure CO2, at more than 90%, which can be made to react by a simple chemical reaction to form a carbonate or another product, without excessive costs. On the other hand, it may be advantageous to keep the carbon monoxide if the choice is made to implement solid conditioning in SiC (silicon carbide) or carbon black, for example, as SiC occupies less storage space than CaCO3. One will thus understand that the choice of whether to treat CO or CO2 at the end of the decontamination may depend on an optimization between: the safety of treating CO2 compared to treating CO, the ease of producing a stable compound acceptable for storage, from CO or from CO2, the volume of the final product (silicon carbide, or carbonates). Of course, the invention is not limited to the example embodiments described above; it extends to other variants. For example, a treatment of carbonaceous waste containing graphite has been described. The invention could, however, be applied generally and in the same manner to treating other types of carbonaceous waste, such as resins. Also, storage containers 5, 13, 16 have been described as essentially containing the respective radioactive elements 36Cl, 3H and 14C. However, a small amount of 3H can of course be present in tank A (reference 5 in FIG. 1) or, conversely, a certain amount of 36Cl may be present in tank B (reference 13). The amounts present depend in particular on the thermal conditions of the drying (at station 3) and roasting (station 6). In one example embodiment, they conform to the teachings of documents FR-2943167 (publication number) and FR-12 60282 (application number). However, variants in the thermal conditions for these treatments can be envisaged without any significant impact on the invention.
	claims	1. A neutron therapy apparatus, comprising:a beam shaping assembly including a moderator and a reflector surrounding the moderator, wherein the moderator moderates neutrons to a predetermined energy spectrum and the reflector guides deflected neutrons back to enhance the neutron intensity in the predetermined energy spectrum;a neutron generator embedded inside the beam shaping assembly, wherein the neutron generator generates neutrons after irradiated by an ion beam;at least a tube for transmitting the ion beam to the neutron generator, wherein the tube defines at least an axis, the tube comprises a first tube portion defining a first axis and a second tube portion defining a second axis and connected with the first tube portion, the beam shaping assembly rotates around the first axis of the first tube portion or the second axis of the second tube portion;deflection magnets for changing the transmission direction of the ion beam;a collimator for concentrating neutrons;a supporting frame for holding the beam shaping assembly, wherein the supporting frame comprises a first supporting part and a first track set in the first supporting part, and the beam shaping assembly is retained on the first track of the supporting frame; andan irradiation room for receiving a irradiated object, wherein the first track is recessed in the supporting frame so as to form a containing room connected with the irradiation room, and the collimator extends into the irradiation room through the containing room,wherein the beam shaping assembly rotates around the axis of the tube and/or moves along the supporting frame. 2. The neutron therapy apparatus according to claim 1, wherein a first angle is formed between the first tube portion and the second tube portion, the degree of the first angle is changed to adjust the position of the beam shaping assembly relative to the irradiated object in the irradiation room. 3. The neutron therapy apparatus according to claim 1, wherein both of the first supporting part and the first track are arranged in arc-shape, the first supporting part includes an arc-shaped external surface, the first track is recessed from the arc-shaped external surface of the first supporting part. 4. The neutron therapy apparatus according to claim 1, wherein the tube further comprises a third tube portion connected with the neutron generator, a second angle is formed between the second tube portion and the third tube portion, and the degree of the second angle is changed to adjust the position of the beam shaping assembly relative to the irradiated object in the irradiation room. 5. The neutron therapy apparatus according to claim 4, wherein the deflection magnets are fixed on the supporting frame, the deflection magnets comprise a first deflection magnet located between the first tube portion and the second tube portion and a second deflection magnet located between the second tube portion and the third tube portion, the ion beam in the first tube portion is transmitted into the second tube portion after the transmission direction is changed by the first deflection magnet, the ion beam in the second tube portion is transmitted into the third tube portion after the transmission direction is changed by the second deflection magnet, the ion beam in the third tube portion irradiates on the neutron generator to generate neutron beams. 6. The neutron therapy apparatus according to claim 5, wherein the supporting frame further comprises a second supporting part for supporting the second deflection magnet, the second supporting part comprises a second track, the second supporting part moves in the second track while the beam shaping assembly moves in the first track. 7. The neutron therapy apparatus according to claim 5, wherein the neutron therapy apparatus further comprises an accelerator, and the supporting frame further comprises a third supporting part, the first deflection magnet is fixed on the third supporting part, the first tube portion is fixed between the accelerator and the first deflection magnet, the third tube portion is connected with the beam shaping assembly and the second deflection magnet, the second tube portion is connected with the first deflection magnet and the second deflection magnet. 8. A neutron therapy apparatus, comprising:a beam shaping assembly including a moderator and a reflector surrounding the moderator, wherein the moderator moderates neutrons to a predetermined energy spectrum and the reflector guides deflected neutrons back to enhance the neutron intensity in the predetermined energy spectrum;a neutron generator embedded inside the beam shaping assembly, wherein the neutron generator generates neutrons after irradiated by an ion beam;at least a tube for transmitting the ion beam to the neutron generator;deflection magnets for changing the transmission direction of the ion beam;a collimator for concentrating neutrons; anda supporting frame, wherein the supporting frame comprises a first supporting part for retaining the beam shaping assembly, a first track is set in the first supporting part, the first track is recessed in the supporting frame to form a containing room which is connected with the irradiation room, and the collimator extends into the irradiation room through the containing room,wherein the beam shaping assembly retains on the supporting frame and moves on the supporting frame. 9. The neutron therapy apparatus according to claim 8, wherein both of the first supporting part and the first track are arranged in arc-shape, the first supporting part includes an arc-shaped external surface, the first track is recessed from the arc-shaped external surface of the first supporting part. 10. The neutron therapy apparatus according to claim 8, wherein the deflection magnets are fixed on the supporting frame, the deflection magnets comprise a first deflection magnet and a second deflection magnet, the supporting frame comprises a second supporting part having a second track for supporting the second deflection magnet, the second deflection magnet moves in the second track while the beam shaping assembly moves in the first track. 11. The neutron therapy apparatus according to claim 10, wherein the tube comprises a first tube portion defining a first axis connected to the accelerator and the first deflection magnet, a third tube portion connected to neutron generator, and a second tube portion defining a second axis connects the first tube portion and the third tube portion, the beam shaping assembly rotates around the first axis or the second axis, the ion beam in the first tube portion is transmitted into the second tube portion after the transmission direction has been changed by the first deflection magnet, the ion beam in the second tube portion is transmitted into the third tube portion after the transmission direction has been changed by the second deflection magnet, the ion beam in the third tube portion irradiates on the neutron generator to generate neutron beams. 12. The neutron therapy apparatus according to claim 11, wherein the supporting frame further comprises a third supporting part, the first deflection magnet is fixed on the third supporting part. 13. A neutron therapy apparatus, comprising:a beam shaping assembly including a moderator and a reflector surrounding the moderator, wherein the moderator moderates neutrons to a predetermined energy spectrum and the reflector guides deflected neutrons back to enhance the neutron intensity in the predetermined energy spectrum;a neutron generator embedded inside the beam shaping assembly, wherein the neutron generator generates neutrons after irradiated by an ion beam;at least two tubes for transmitting the ion beam to the neutron generator;deflection magnets for changing the transmission direction of the ion beam, wherein the deflection magnets comprise a first deflection magnet and a second deflection magnet;a collimator for concentrating neutrons; anda supporting frame for fixing the deflection magnets, wherein the supporting frame comprises a first supporting part with a first track for retaining the beam shaping assembly and a second supporting part for supporting the second deflection magnet, the second supporting part comprises a second track, and the second deflection magnet moves in the second track while the beam shaping assembly moves in the first track,wherein a first angle is formed between the two tubes, and the degree of the first angle is changeable. 14. The neutron therapy apparatus according to claim 13, wherein the tubes comprises a first tube portion connects to the accelerator, a third tube portion connects to the neutron generator, and a second tube portion connects the first portion and the third tube portion, the first angle is formed between the first tube portion and the second tube portion, a second angle is formed between the second tube portion and the third tube portion, at least one of the first angel and the second angel is changeable. 15. The neutron therapy apparatus according to claim 13, wherein the supporting frame comprises a third supporting part, the first deflection magnet is fixed on the third supporting part.
039363503	summary	BACKGROUND OF THE INVENTION This invention pertains in general to nuclear reactor fuel assemblies and in particular to a new thermal expansion compensation system for such assemblies. The number of fuel elements which are used to form the reactive region in a nuclear reactor is ordinarily determined by the critically necessary mass of fissile material and by other considerations, such as the desired energy output and the allowable thermal character of the region. Conventionally, the fuel elements are formed into bundles or sub-assemblies, with the sub-assemblies being assembled or combined to form an overall assembly or reactive region. The spaced fuel elements located within the same bundle or sub-assembly can experience varying rates of heat generation resulting in differing rises in temperature. Moreover, such factors as flux peaking in adjacent coolant channels, unequal distribution of coolant flow through the core region, presence of adjacent structural material, xenon-tilt and other flux perturbations, also lead to the same effect. Accordingly, the spaced fuel elements respond with correspondingly different thermal expansions or contractions so that, unless means are provided for offsetting this thermal effect, the bundle will be subjected to deformation or bowing, which, in general, is undesirable since "hot spots" or regions of extreme temperature rise in the fuel elements can than result and removability of the fuel bundle is impaired. An additional undesirable effect arises when peripherally located fuel elements bow to jam or obstruct control rod movement. The aforementioned problems experienced in the boiling water reactors and pressurized water reactors is amplified in the liquid metal fast breeder reactors where the temperature gradients in different parts of the core are even more extreme. The different temperatures expected for the various sections of the liquid metal breeder reactor will cause different thermal expansions among these various sections. Thus, components made of the same material which are aligned at room temperature will not be aligned at operating conditions. For instance, control rods, their drive mechanism and the guide tubes in the reactor core will not remain aligned when the core support plate is exposed to inlet sodium at approximately 750.degree.F, the top of the core assemblies are exposed to outlet sodium at approximately 1000.degree.F and the head, to which the control rod drive mechanism is fastened, is maintained at approximately 400.degree.F. This misalignment causes control rods to bind and not insert when required, thus creating a serious control problem. The heat generated in the fuel is highest in the center of the core and decreases away from the center. This descrease in heat generation causes a corresponding decrease in the temperature of the fuel, the cladding and the assemblies. Thus a given part of the core will have a higher temperature on the side toward the center than on the outside, causing a temperature gradient through the part. This change in temperature through the part causes uneven thermal expansion with the side closest to the center expanding more, because it is hotter. The uneven thermal expansion causes the part to bend or bow as mentioned above. The thermal bowing in turn causes the fuel sub-assemblies to move toward the center of the core, creating an unstable nuclear characteristic, due to the increased concentration of fissile material, which presents control problems. The problem becomes extremely critical when the movement of the fuel sub-assembly towards the center of the core occurs in a short period of time. This might occur if a subassembly is twisted slightly and pushes against a neighboring sub-assembly. The increasing bowing force will sooner or later overcome the friction between the sub-assemblies, or a random vibration will trigger the movement. Then, the sub-assembly will bend very rapidly towards the center. Even worse, a chain reaction could be caused thereby where several subassemblies jump one after the other. This motion of subassemblies towards the center increases the effective heavy metal mass density with a resultant increase in power, possibly to a dangerous level. The prior art has been able to minimize the problems caused by the uneven thermal expansion of the various components within the reactor by utilizing different structural support designs in the fuel assembly as illustrated by application No. 19,851 entitled "FUEL ARRANGEMENT FOR A NUCLEAR REACTOR" filed Apr. 4, 1960, now abandoned, and assigned to the Westinghouse Electric Corporation. Another support method was illustrated in application No. 19,760 entitled "MEANS FOR SUPPORTING FUEL ELEMENTS IN A NUCLEAR REACTOR" filed Apr. 4, 1960, now U.S. Pat. No. 3,182,003, and assigned to the Westinghouse Electric Corporation. While the techniques presented in the aforementioned applications for Letters Patent have been able to overcome the problems caused by the thermal gradients in the pressurized water reactor and boiling water reactor, it is not expected that they will be able to solve problems caused by the extreme temperature graidents anticipated in the liquid metal fast breeder reactors. SUMMARY OF THE INVENTION This invention utilizes materials with different thermal expansion rates to compensate for the varying temperature gradients encountered in reactor operation. For example, when a nuclear reactor core had a top plug, bottom support plate and core bundling device, each laterally supporting the fuel rods in the core and when each of these lateral supports is constructed of the same material, a temperature gradient between the supports causes the supports to expand at different rates and thereby to deform the fuel rods. In order to avoid this problem the present invention provides fuel rod and control rod support means which are constructed from materials having such rates of thermal expansion that under the environmental operating conditions at their respective positions of support, the total expansion of each support member substantially equal the thermal expansion of every other support member, under the environmental operating conditions, thus retaining alignment.
050135201	summary	The invention relates to an apparatus for the insertion of elongated, mutually parallel fuel rods into an elongated can having a rectangular and in particular square cross section, the apparatus including a holder for the can and a fuel rod positioning arm, the arm having an insertion end for insertion through a lateral transverse slit in the can in an insertion direction at right angles to the longitudinal direction of the can. With such an apparatus, fuel rods, for instance, from irradiated and spent nuclear reactor fuel assemblies, are inserted into the can in the closest possible packing structure and stored in the can until reprocessing. In this way, both storage space and transport costs can be reduced, as compared with temporary storage of the complete spent nuclear reactor fuel elements. However, such an apparatus is difficult to control. It is accordingly an object of the invention to provide an apparatus for inserting fuel rods into a can, which overcomes the hereinafore-mentioned disadvantages of the heretoforeknown devices of this general type and which is simpler to control. With the foregoing and other objects in view there is provided, in accordance with the invention, an apparatus for the insertion of mutually parallel, elongated fuel rods into an elongated can having a rectangular cross section, a longitudinal direction and a lateral transverse slit formed therein, comprising a holder for holding a can, a fuel rod positioning arm having an insertion end for insertion through the slit in the can in an insertion direction at right angles to the longitudinal direction of the can, a support structure attached to the insertion end of the arm for supporting fuel rods, the support structure having a pivot axis at right angles to the insertion direction of the arm and to the longitudinal direction of the can about which the support structure is pivotable back and forth within a given pivot angle, the support structure having a jacket surface with two fuel rod support surfaces being curved outwardly about the pivot axis and offset alongside one another in the direction of the pivot axis, one of the support surfaces merging from a first segment with a relatively shorter radial spacing from the pivot axis than the other of the support surfaces, into a second segment with a relatively greater radial spacing from the pivot axis than the other of the support surfaces, and the radial spacings of the two support surfaces from the pivot axis increasing in infinite graduations within the given pivot angle, as seen in opposite directions. The support structure for the fuel rods of this apparatus can be positioned quickly and simply in the can. Moreover, by a simple swiveling with the support structure, a row of new guide openings for the fuel rods to be inserted is formed in the can, after the row of guide openings formed previous to the swiveling by the support structure, has been filled with fuel rods. In accordance with another feature of the invention, there is provided a resilient restoring element, the support structure and the holder being displaceable relative to one another in a direction parallel to the insertion direction of the arm counter to the resilient restoring element. In accordance with a further feature of the invention, the arm with the support structure and the holder are displaceable relative to one another in the longitudinal direction of the can. In accordance with an added feature of the invention, the can has another lateral transverse slit formed therein, and there is provided a counterpart structure disposed on the holder opposite the support structure for insertion through the other slit in the can, the counterpart structure having toothing defining gaps in the longitudinal direction of the can. In accordance with an additional feature of the invention, the counterpart structure is an elongated, rotatable eccentric shaft disposed transversely to the longitudinal direction of the can, the shaft having an outer jacket surface with grooves formed therein in circumferential direction forming the toothing. In accordance with a concomitant feature of the invention, the counterpart structure has a support surface for retention of the can. Through the use of these features, insertion of the fuel rods into the can is facilitated. Other features which are considered as characteristic for the invention are set forth in the appended claims. Although the invention is illustrated and described herein as embodied in an apparatus for inserting fuel rods into a can, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
	claims	1. A data detection system for an X-ray CT apparatus comprising:a data acquisition circuit, including at least one row of X-ray detection elements arrayed in a channel direction, and configured to acquire data required for generating X-ray CT image data corresponding to the at least one row of the X-ray detection elements; anda connection structure configured to connect said data acquisition circuit with another adjacent data acquisition circuit directly or indirectly in a row direction, the X-ray detection elements installed in said data acquisition circuit shifting from X-ray detection elements installed in the another adjacent data acquisition circuit in the channel direction; andan adjustment structure configured to adjust a shift amount in the channel direction between said data acquisition circuit and the another adjacent data acquisition circuit. 2. The data detection system for the X-ray CT apparatus of claim 1,wherein said data acquisition circuit includes a platy circuit board whose thickness direction is different from a rotation direction of said data acquisition circuit. 3. The data detection system for the X-ray CT apparatus of claim 1,wherein said data acquisition circuit has X-ray detection elements, each having photodiodes arranged in an incident direction of an X-ray. 4. The data detection system for the X-ray CT apparatus of claim 1,wherein said data acquisition circuit includes a platy circuit board,a photodiode installed in each of the X-ray detection elements is on the platy circuit board, anda boundary face between the photodiode and the platy circuit board being perpendicular to the row direction. 5. The data detection system for the X-ray CT apparatus of claim 1,wherein said data acquisition circuit includes plural X-ray detection elements in the row direction. 6. A data detection system for the X-ray CT apparatus of claim 1, including:said data acquisition circuit; andthe another adjacent data acquisition circuit connected with said data acquisition circuit in the row direction by said connection structure. 7. An X-ray CT apparatus comprising:said data detection system of claim 1;an X-ray tube configured to expose an X-ray to an object; anda data processing circuit configured to generate the X-ray CT image data based on projection data of the object acquired by said data detection system.
	summary
056404352	description	DESCRIPTION OF PREFERRED EMBODIMENTS The principle of the present invention will first be described prior to illustrating embodiments of the present invention. FIG. 1 illustrates the structure. Fundamentally, the fuel assembly is provided with a water rod 1 which has a coolant ascending path 2 of which a coolant inlet port 4 is open in a region lower than a resistance menber (such as fuel supporting portion of a lower tie plate) 6 provided at a lower portion of the fuel assembly, and which further has a coolant descending path 3 that downwardly guides the coolant from the coolant ascending path and that has a coolant delivery port 5 open in a region higher than the resistance member 6. The resistance member 6 has a plurality of coolant passage ports 7. The pressure differential .DELTA.P changes between the region lower than the resistance member 6 and the region higher than the resistance member 6 depending upon the change in the flow rate of the coolant (cooling water) that flows through the coolant passage ports 7 formed in the resistance member 6. The differential pressure caused by narrowing or broadening of the coolant path varies nearly in proportion to the square power of the flow rate of the cooling water. Therefore, if the flow rate of the cooling water passing through the resistance body 6 changes from 80% to 120%, the pressure differential .DELTA.P increases by about 2.25 times. FIG. 2 illustrates a relationship between the flow rate of cooling water in the water rod 1 and the pressure differential between the inlet and the outlet of the water rod 1 (pressure differential between the coolant inlet port 4 and the coolant delivery port 5). If the flow rate of the cooling water is increased starting from zero, the pressure differential between the outlet and the inlet of the water rod 1 once reaches a maximum value. As the flow rate of the cooling water is further increased, the pressure differential between the outlet and the inlet of the water rod 1 once drops to a minimum value, and then increases monotonously. This is due to the phenomenon shown in FIGS. 3A to 3C. FIG. 3A shows the condition in the water rod 1 at a point S in FIG. 2, FIG. 3B shows the condition in the water rod 1 at a point T in FIG. 2, and FIG. 3C shows the condition in the water rod 1 at a point U in FIG. 2. Being irradiated with neutrons and gamma rays from the fuel rods around the water rod 1, the cooling water in the water rod 1 generates the heat at a rate of about 0.5 to 2 W/cm.sup.2. When the flow rate of the cooling water flowing through the water rod 1 is very small (condition of point S in FIG. 2), the cooling water in the water rod 1 generates the heat and evaporates being irradiated with neutrons and the like. The upper portions of the coolant ascending path 2 and the coolant descending path 3 are then filled with the vapor as shown in FIG. 3A. A liquid level L.sub.1 is established in the coolant ascending path 2, and the pressure differential between the outlet and the inlet of the water rod 1 is generated by the difference in the static water head between the liquid level L.sub.1 and the liquid level L.sub.2 of the coolant delivery port 5 (outlet of the coolant descending path 3) of the water rod 1. The flow rate of the cooling water that flows into the coolant ascending path 2 maintains balance with respect to the flow rate by which the vapor flows out through the coolant delivery port 5. As the flow rate of the cooling water is further increased from the point S in FIG. 2, the cooling water flows into the coolant ascending path 2 at a rate that is greater than the amount by which the cooling water is vaporized. In such a case (e.g., at the point T in FIG. 2), the cooling water flows down through the coolant descending path 3 as shown in FIG. 3B. At this moment, the static head in the coolant ascending path 2 is partly cancelled by the weight of the cooling water that flows through the coolant descending path 3, and the pressure differential between the outlet and the inlet of the water rod 1 becomes smaller that the maximum value S.sub.0. As the flow rate of the cooling water further increases, however, the unsaturated water introduced through the coolant inlet port 4 is not boiled in the coolant ascending path 2 and the coolant descending path 3 (void fraction is very reduced), and is permitted to flow out through the coolant delivery port 5 (condition of point U in FIG. 2, FIG. 3C). Therefore, the water flows through the coolant ascending path 2 and the coolant descending path 3 almost in the form of a single phase stream. Under the condition of FIG. 3A, therefore, the static water heads at the level of the coolant ascending path 2 and at the level of the coolant delivery port 5 in the coolant descending path 3 are cancelled by each other, so that the difference in the static water head becomes very small. However, since the cooling water flows at a large rate in the water rod 1, the pressure loss increases due to friction and inversion in the flow of the cooling water, and the pressure differential increases again between the outlet and the inlet of the water rod 1. Owing to the above-mentioned phenomenon, the flow rate of the cooling water in the water rod 1 varies greatly and the void fraction varies greatly even though the pressure differential varies little between the outlet port and the inlet port of the water rod 1. Therefore, the void fraction can be changed greatly by changing the flow rate of the cooling water (flow rate in the reactor core) that flows in the fuel assembly, if the resistance of the resistance member 6 is so adjusted that the pressure differential between the outlet and the inlet of the water rod 1 is smaller than a pressure differential between the outlet and the inlet of the water rod 1 that corresponds to the minimum value T.sub.0 of FIG. 2 when the flow rate in the reactor core is 80% and that the pressure differential between the outlet and the inlet of the water rod 1 is in excess of a pressure differential between the outlet and the inlet of the water rod 1 that corresponds to the maximum value S.sub.0 of FIG. 2 when the flaw rate in the reactor core is 120%. In the above example, the flow rate of 80% in the reactor core lies on the left side of the maximum value S.sub.0 and, preferably, lies on the left side of a point Q (pressure differential between the outlet and the inlet same as the minimum value T.sub.0) in FIG. 2, and the flow rate of 120% in the reactor core lies on the right side of the minimum value T.sub.0 and, preferably, lies on the right side of the point R (pressure differential between the outlet and the inlet same as the maximum value S.sub.0) in FIG. 2. An example of a fuel assembly utilizing the above-mentioned principle, i.e., an example of the structure of a fuel assembly to be used in a boiling-water reactor, will now be described in conjunction with FIGS. 4, 5, 6, 7A and 7B. A fuel assembly 10 of this example is comprised of fuel rods 11, an upper tie plate 12, a lower tie plate 13, a fuel spacer 16, a channel box 17, and a water rod 19. The upper and lower ends of the fuel rods 11 are held by the upper tie plate 12 and the lower tie plate 13. The water rod 19, too, is held at its both ends by the upper tie plate 12 and the lower tie plate 13. Several fuel spacers 16 are arranged in the axial direction of the fuel assembly 10 to maintain an appropriate distance among the fuel rods 11. Between the fuel rods 11. Spaces 50 (second cooling water path) of a cooling water path is formed. The fuel spacers 16 are held by the water rod 19. The channel box 17 is mounted on the upper tie plate 12 to surround the outer periphery of a bundle of fuel rods 11 that are held by the fuel spacers 16. The lower tie plate 13 has a fuel rod supporting portion 14 at the upper end and has therein a space 15 under the fuel rod supporting portion 14. The lower ends of the fuel rods 11 and the water rod 19 are supported by the fuel rod supporting portion 14. With reference to FIG. 5, a number of fuel pellets 33 are loaded in a covering tube 30 whose both ends are sealed with an upper end plug 31 and a lower end plug 32. A gas plenum 34 is formed at an upper end of the covering tube 30. The water rod 19 has a diameter (outer diameter of an outer tube 21 that will be mentioned later) which is greater than the diameter of the fuel rod 11, and is arranged at the central portion in the cross section of the fuel assembly 10. Structure of the water rod 19 will now be described in detail with reference to FIGS. 7A and 7B. The water rod 19 consists of an inner tube 20, an outer tube 21 and a spacer 22. The outer tube 21 and the inner tube 20 are arranged in concentric with each other, and the outer tube 21 surrounds the outer periphery of the inner tube 20. The upper end of the outer tube 21 is sealed with a covering portion 23, and the upper end of the covering portion 23 is held by the upper tie plate 12 being inserted therein. The covering portion 23 covers the upper end of the inner tube 20 so as to form a gap with respect to the upper end of the inner tube 20. The upper rod of the inner tube 20 is secured to the inner surface of the outer tube 21 via plate-like spacers 22 that are radially arranged from the axis of the water rod 19. The lower end of the outer tube 21 is sealed with a sealing portion 24. The lower end of the inner tube 20 penetrates through the sealing portion 24 to protrude downwardly. The lower end of the inner tube 20 penetrates through the fuel rod supporting portion 14 of the lower tie plate 13. A coolant inlet port 28 formed in the lower end of the inner tube 20 is open in the space 15 of the lower tie plate 13. The interior of the inner tube 20 forms a coolant ascending path 25. An annular path formed between the inner tube 20 and the outer tube 21 defines a coolant descending path 26. A plurality of cooling water delivery ports 29 are formed in the wall at the lower end of the outer tube 21 in the circumferential direction. The cooling water delivery ports 29 are formed in the circumferential direction maintaining an equal distance and are open in the space 50 over the fuel rod supporting portion 14. In this embodiment, the fuel rod supporting portion 14 exhibits the function of the resistance member 6 of FIG. 1. The cooling water ascending path 25 and the cooling water descending path 26 are communicated with each other through an inverting portion 27 formed at an upper end of the water rod 19. Thus, the water rod 19 contains therein a cooling water path (first cooling water path) of an inverted U-shape which consists of the cooling water ascending path 25, the cooling water descending path 26 and the inverting portion 27. When the fuel assembly 1 of this embodiment is loaded in the reactor core of the boiling-water reactor (the whole fuel assemblies are represented by the fuel assemblies 1) to operate the boiling-water reactor, most of the cooling water is directly introduced into space 80 among the fuel rods 11 of the fuel assembly 10 loaded in the reactor core passing through space 15 of the lower tie plate 13 and penetration holes 18 (FIG. 74) formed in the fuel rod supporting portion 14. The remainder of the cooling water that flows into space 15 in the lower tie plate 13 flows through the coolant inlet port 28 into the coolant ascending path 25 of the water rod 19, and is delivered into the space 80 over the fuel rod supporting portion 14 through the inverting portion 27, the coolant descending path 26 and the coolant delivery ports 29. The cooling water delivered from the cooling water delivery ports 29 may be in the form of a liquid or a gas (vapor) depending upon the flow rate of the cooling water that flows into the water rod 19 through the cooling water inlet port 28 as described earlier. According to this embodiment, the pressure loss by the fuel rod supporting portion 14 and the specifications of the inner tube 20 and the outer tube 21 have been selected in advance, so that the condition of FIG. 3A develops in the water rod 19 when the flow rate in the reactor core is smaller than 100% (flow rate at the maximum value S.sub.0 of FIG. 2 in the water rod 19), and the condition of FIG. 3C develops in the water rod 19 when the flow rate in the reactor core is 110% (flow rate at the point R of FIG. 2 in the water rod 19). Concretely described below is how to operate the boiling-water reactor while changing the void fraction in the water rod 19 under the condition where the fuel assembly 10 is loaded in the reactor core of the boiling-water reactor. This operation method applies for one fuel cycle (operation period of a nuclear reactor from when the fuel in the reactor core is replaced and operation of the nuclear reactor is started to when the nuclear reactor is stopped for renewing the fuel, i.e., usually, one year). In the boiling-water reactor as disclosed in Japanese Patent Publication No. 11038/1982, Col. 8, line 19 to Col. 10, line 31, the control rods are operated and the flow rate in the reactor core is adjusted to raise the atomic output up to 100% (point N in FIG. 7 of the above publication and 80% flow rate in the reactor core in this embodiment) in order to prevent the fuel from breaking. The flow rate in the reactor core is increased to compensate the reduction of reactor output as the nuclear fuel substance is consumed, i.e., to maintain the reactor output at 100%. When the flow rate in the reactor core has reached 100% owing to the compensation operation, the flow rate in the reactor core is decreased to 20% and the control rods are pulled out until the nuclear reactor produces a predetermined output as disclosed in Japanese Patent Publication No. 11038/1982, Col. 11, line 23 to Col. 12, line 40 (Col. 9, line 47 to Col. 10, line 51 of U.S. Pat. No. 4,279,698). Thereafter, the flow rate in the reactor core is increased to 80% to maintain the reactor output at 100%. To maintain the reactor output at 100%, the control operation is repeated. According to this embodiment, the output of the nuclear assembly is flattened in the axial direction by utilizing nuclear characteristics. After the flow rate in the reactor core has been decreased, therefore, the control rods are pulled out; i.e., there is no need of pulling out the control rods or there is no need of inserting other control rods unlike the art disclosed in Japanese Patent Publication No. 11038/1982 Col. 12, lines 19 to 29 (U.S. Pat. No. 4,279,698, Col. 10, lines 21 to 34), and what is needed is to pull out only those control rods that are deeply inserted. As described above, the operation for obtaining 100% of reactor output with the flow rate in the reactor core of smaller than 100% is continued for about 70% of a fuel cycle period. During the period of about 70%, the water rod 19 in the fuel assembly 1 assumes the condition as shown in FIG. 3A. That is, the upper portion of the coolant ascending path 25 and the interior of the coolant descending path 26 are filled with the vapor; i.e., the liquid cooling water does not almost exist in the vapor region which is formed in the water rod 19 in the fuel assembly 1 loaded in the reactor core. Therefore, up to 70% of the fuel cycle, the vapor region is formed in the water rod 19, and the cooling water in the reactor core is partly expelled. It can be said that the fuel assembly 10 according to this embodiment is provided with a water rod that has a vapor reservoir. The coolant descending path 26 works as a vapor reservoir until the flow rate in the reactor core exceeds 100% as will be described later. Formation of the vapor region in the water rod 19 suppresses the effect for decelerating neutrons and promotes the conversion of uranium 238 into plutonium 239 in the nuclear fuel substance. Suppression of the neutron deceleration effect results in the suppression of nuclear fission such as of uranium 235 and results in the decrease in the reactivity. Decrease in the reactivity, however, can be alleviated by pulling out the control rods by an increased amount. During this period, new core materials such as plutonium 239 and the like may be formed, and the core material in the reactor core decreases at a reduced rate. According to this embodiment as described above, the surplus reactivity (surplus neutrons) is absorbed by uranium 238 in the nuclear fuel substances to form a new core material. By the time when the operation period of the boiling-water reactor reaches about 70% of the fuel cycle, the surplus reactivity in the reactor core will have been lowered to a minimum level for maintaining the criticality. In this case, the flow rate in the reactor core is gradually increased in excess of 100%; i.e., the flow rate in the reactor core is increased to 120% at the time when the operation of a fuel cycle is stopped. The recirculation pump does not hinder the operation at all if the flow rate in the reactor core does not exceed 120%. The output of the nuclear reactor is maintained at 100% from when the flow rate in the reactor core exceeds 100% until when it reaches 120%. When the flow rate in the reactor core is greater than 110%, the interior of the water rod 19 assumes the condition of FIG. 3C where the liquid flows in the form of a single-phase stream and no vapor stays in the coolant descending path 26. As the flow rate in the reactor core becomes greater than 110%, therefore, the amount of cooling water (the number of hydrogen atoms) in the reactor core increases remarkably compared with when the flow rate in the reactor core is smaller than 100%, and whereby the effect increases for decelerating the neutrons, and hence nuclear fission of uranium 235 and the like becomes active. Accordingly, the infinite multiplication factor of the fuel assembly increases and it is made possible to effectively utilize the core materials. The fuel assembly 1 experiences the fuel cycle operation four times in the reactor core. Therefore, the conditions of FIG. 3A and 3B are alternatingly repeated four times each. According to the fuel assembly 10 of this embodiment as described above, the water rod is made up of a simply constructed double tube. Therefore, the phase condition of the cooling water in at least the coolant descending path 26 can be successively changed from the gaseous state to the liquid state by means which controls the output of the nuclear reactor (by means which adjusts the flow rate in the reactor core and which may be a recirculation pump). That is, the range in which the average void fraction changes in the fuel assembly 10 can be greatly broadened being added up with the range of void fraction change due to the water rod 19. Concretely speaking, the flow rate in the reactor core in this embodiment is increased to 80 to 120%, so that the average void fraction of the fuel assembly 10 changes as shown in FIG. 8. This is due to the change of void fraction outside the water rod 19. The fuel assembly 10 exhibits an average void fraction change on which is superposed an average void fraction change produced by the water rod 19. Therefore, the nuclear fuel substances can be effectively utilized with a simply constructed structure, and the operation period of a fuel cycle can be greatly extended. Described below is another operation control to substitute for the aforementioned operation control. According to Japanese Patent Publication No. 44237/1983 (U.S. Pat. No. 4,285,769), a fuel cell constituted by four adjoining fuel assemblies is divided into a controlled cell and a noncontrolled cell, the average enrichment of the controlled cell is selected to be smaller than that of the noncontrolled cell, and the output of the nuclear reactor under the ordinary operation condition is controlled by the control rods only that are inserted in the controlled cell. On Col. 27, line 29 to Col. 28, line 43 of Japanese Patent Publication No. 44237/1983 (U.S. Pat. No. 4,285,769, Col. 16, lines 6 to 65), there is described that the control rods inserted in the controlled cell (c cell) are driven by a control rod driving device of the type of fine movement. After the boiling-water reactor is started, the control rods in the controlled cell and the flow rate in the reactor core are adjusted to maintain 100% output of the nuclear reactor with a 80% flow rate in the reactor core. Reduction of the reactor output due to the consumption of the core material is compensated by increasing the flow rate in the core before the flow rate in the core reaches 100% and after the flow rate has reached 100%, by gradually pulling out the control rods from the controlled cell by the Control rod drive device while maintaining the flow rate in the reactor core at 100%. After 70% period of the fuel cycle, operation of the control rods is stopped and the flow rate in the reactor core is gradually increased up to 120%. During the period of up to 70% of the fuel cycle, the water rod 19 is filled with the water vapor as mentioned earlier and after 70% of the fuel cycle, the void fraction in the water rod 19 can be markedly reduced. In the aforementioned embodiment, the inverting portion 27 is arranged at a position over the position of a gas plenum 34 of the fuel rod 11, i.e., over the upper end of the fuel pellet-filled region. The lower end of the coolant descending path 26 is located at a position at least under the upper end (lower end of gas plenum 34) of the fuel pellet-filled region (region filled with fuel pellets 33) of the fuel assembly 1. In other words, the vapor reservoir of the water rod 19 should be located at a position at least lower than the upper end of the fuel pellet-filled region of the fuel assembly. In particular, in order that the vapor region is uniformly distributed in the axial direction of the fuel pellet-filled region where nuclear fission takes place in the nuclear assembly, the cooling water delivery ports 29 (or vapor delivery ports of the vapor reservoir) of the coolant descending path 26 (vapor reservoir) should be located near the lower end of the fuel pellet-filled region or desirably at a position (near the fuel rod supporting portion 14) under the fuel pellet-filled region. Namely, the vapor region under the condition of FIG. 3A is formed over the full length in the axial direction of the fuel pellet-filled region, and the output distribution of the fuel assembly 1 is flattened in the axial direction. In this embodiment in which the coolant descending path 26 surrounds the periphery of the coolant ascending path 25, the neutron deceleration effect of when the coolant ascending path 25 and the coolant descending path 26 are substantially filled with liquid cooling water and the effect of converting into plutonium of at least when the coolant descending path 26 is filled with the vapor, can be uniformly imparted to the fuel rods that surround the water rod 19. By lowering the position of the inverting portion 27 from the upper end of the fuel pellet-filled region, furthermore, there can be employed a short water rod 19 having a length shorter than the fuel rods 11. In this case, pressure loss in the fuel assembly can be decreased. Referring to FIG. 2, difference in the flow rates in the reactor core between the maximum value S.sub.0 and the minimum value T.sub.0, pressure differential between the outlet and the inlet of the water rod 19 for the maximum value S.sub.0, and pressure differential between the outlet and the inlet of the water rod 19 for the minimum value T.sub.0, undergo the change depending upon the sizes of the inner tube 20 and the outer tube 21. This will now be described. FIGS. 9, 11 and 13 illustrate changes of pressure differential between the outlet and the inlet of the water rod 19 for the flow rate of cooling water supplied into the water rod 19 when the outer tube 21 has an inner diameter of 30 mm and when the inner diameter and outer diameter of the inner tube 20 are changed. FIG. 9 shows the characteristics when the inner tube 20 has an outer diameter of 14 mm and an inner diameter of 12 mm, FIG. 11 shows the characteristics when the inner tube 20 has an outer diameter of 17 mm ant an inner diameter of 15 mm, and FIG. 13 shows the characteristics when the inner tube 20 has an outer diameter of 20 mm and an inner diameter of 18 mm. FIGS. 10, 12 and 14 illustrate changes of the average void fraction in the water rod for the flow rate of cooling water supplied into the water rod, that correspond to FIGS. 9, 11 and 13. When the inner tube 20 is thin as will be obvious from FIG. 9, a maximum value is reached with a flow rate of cooling water which is greater than that of the thick inner tube 20 (FIGS. 11 and 13), and the pressure differential thereafter changes suddenly. Therefore, the range for changing the flow rate of the cooling water is small compared with the range for changing the pressure differential. This is due to the fact that since the inner tube 21 is thin, the heat is generated in small amounts in the inner tube 20 and the flow rate of the cooling water decreases, that surpasses the amount of vapor generated in the inner tube 20, and that the fluid flows through the inner tube 20 at such a high speed that the flow resistance increases. When the sectional area of the coolant descending path 26 between the inner tube 20 and the outer tube 21 is great and the flow rate is small, however, the void is almost 100% in the coolant descending path 26. Therefore, the range in which will change the average void fraction of the water rod having a thin inner tube 20 is little different from that of the water rod having a thick inner tube 20. On the other hand, the thicker the inner tube 20 of the water rod, the smaller the variable range of the pressure differential relative to the variable range of the cooling water. In any case, however, the average void fraction decreases sharply as a maximum value of the pressure differential is exceeded as will be obvious from FIGS. 10, 12 and 14. Referring to FIGS. 9, 11 and 13, furthermore, the average void fraction in the water rod for the flow rate of cooling water greater than a point R is conspicuously smaller than the average void fraction for the flow rate of cooling water smaller than the maximum value S.sub.0. FIG. 15 illustrates a relationship between the average void fraction in the water rod 19 and the pressure differential between the outlet and the inlet of the water rod 19, such that the contents of FIGS. 9 to 14 can be easily comprehended. As will be obvious from FIG. 15, the average void fraction of the water rod drops from 76% to 2% when the pressure differential is changed from 0.015 MPa to 0.03 MPa between the outlet and the inlet of the water rod 19 which employs the inner tube having an outer diameter of 20 mm. The pressure loss of the fuel rod supporting portion 14 of the lower tie plate 2 varies nearly in proportion to the square power of the flow rate of cooling water that flows in the fuel assembly 1 as mentioned earlier. Therefore, if the pressure differential between the outlet and the inlet of the water rod is set to be 0.015 MPa when the flow rate of cooling water that flows through the fuel assembly 1 is 80%, the pressure differential becomes 0.034 MPa when the flow rate of cooling water is 120%, and the average void fraction becomes 1% in the water rod. Therefore, the variable range of average void fraction in the water rod 19 is 75%; i.e., the variable range of average void fraction is 7.5% with the fuel assembly 10 as an average. Accordingly, a net variable range of average void fraction of the fuel assembly 10 is 16.5% being added up with 9% by the flow rate in the reactor core of FIG. 8. As shown in FIG. 6, the water rod 19 occupies about one-tenth the sectional area of the coolant path of the fuel assembly 10. Here, the variable range of average void fraction of the fuel assembly can be increased by providing two or more water rods 19 in the fuel assembly. To improve fuel economy, there has been proposed a fuel assembly which is provided with nine water rods. In this case, the water rods as a whole occupy about 30% the sectional area of the coolant path of the fuel assembly. A fuel assembly 35 of this embodiment is shown in FIG. 16. The fuel assembly 35 is the one in which the water rods of the fuel assembly disclosed in Japanese Patent Application No. 167972/1986, page 9, line 4 to page 11, line 5, and FIG. 1 are all replaced by the above-mentioned water rods 19. The fuel assembly 35 of this embodiment further exhibits the effect of the fuel assembly 1 of Japanese Patent Application No. 167972/1986 (effect of reactivity gain shown in FIG. 3 of this prior application). Described below is the operation of the boiling-water reactor in which the fuel assembly 35 of this embodiment is loaded in the reactor core. The whole fuel assemblies in the reactor core is represented by the fuel assembly 35. FIG. 17 illustrates the change of characteristics of the case when the boiling-water reactor loaded with the fuel assembly 35 is operated with two continuous fuel cycles. Broken lines indicate the case of this embodiment and solid lines indicate the case when use is made of the fuel assembly 35 which has conventional rods 19 (without coolant descending path 26). In the former case, the spectrum shift operation is carried out while changing the void fraction and in the latter case, no spectrum shift operation is carried out. The output of the nuclear reactor during the fuel cycle period is controlled by using the method disclosed in Japanese Patent Publication No. 44237/1983. The flow rate in the reactor core should range from 80 to 120% to maintain the output of the nuclear reactor at 100%. According to this embodiment, the inner tube 20 and the outer tube 21 have been so specified that the condition of FIG. 3A is established in the water rod 19 when the flow rate in the reactor core is smaller than 80% and that the condition of FIG. 3C is established in the water rod 20 when the flow rate in the reactor core is 110%. The flow rate of 80% in the reactor core is the one which corresponds to the maximum value S.sub.0 of FIG. 2 at which the cooling water is supplied into the water rod 19, and the flow rate of 110% in the reactor core is the one which corresponds to the point R of FIG. 2 at which the cooling water is supplied into the water rod 19. During the period of up to 70% of both the first fuel cycle and the second fuel cycle, the flow rate in the reactor core is maintained at 80% as shown in FIG. 17(d) and the change in the output of the nuclear reactor due to the consumption of the core material is compensated by gradually pulling out the control rods using a finely-driving control rod driving device. From 70% of the fuel cycle to the end of the fuel cycle, the flow rate in the reactor core is gradually increased from 80% to 120% while halting the operation of the control rods. With the output of the nuclear reactor being controlled as described above, the surplus reactivity in this embodiment is maintained at a minimum level necessary for criticality for a predetermined period of time (FIG. 17(b)) at the end of each of the fuel cycles. Furthermore, the ratio of hydrogen atom density to uranium atom density greatly increases toward the end of each of the fuel cycles (FIG. 17(c)). The core material in the nuclear fuel material loaded in the reactor core is consumed in small amounts during the period B of from the start of the fuel cycle to 70% of the fuel cycle, and is consumed in large amounts during the period E of from 70% of the fuel cycle to the end of the fuel cycle, as shown in FIG. 17(a). In this embodiment which employs nine water rods 19, the whole water rods occupy 30% of the sectional area of the coolant path of the fuel assembly 35 as mentioned above, and the variable range of the average void fraction of the fuel assembly 35 is increased by as great as 22.5% owing to the function of nine water rods 19. In practice, however, to this value is further added 9% of FIG. 8. Therefore, the nuclear fuel substances can be very effectively utilized, the period of a fuel cycle can be markedly extended for operating the nuclear reactor, and the fuel assembly 35 can be simply constructed. It is further possible to change the shape of nine water rods 19 of the fuel assembly 35 (e.g., to differ the inner diameter of the inner tube 20 of nine water rods 19) to vary the transition period from the state of FIG. 3A to the state of FIG. 3C. FIGS. 18A and 19 illustrate further embodiments of the water rod 19 employed for the fuel assembly 10 and the fuel assembly 35. In the water rod 19A of FIGS. 18A and 18B, a coolant ascending tube 40 and a coolant descending tube 41 are coupled together through a coupling tube 42, thereby to form a coolant ascending path 43 and a coolant descending path 44. The water rod 19A exhibits the function same as that of the water rod 19, but presents an advantage in that the metal has a small sectional area with respect to the area occupied by the water rods. In this embodiment, the coolant delivery port 29 is opened downwardly and may be affected by the dynamic pressure of the cooling water that flows upwardly in the fuel assembly. In the similar way as in the embodiment shown in later-appearing FIG. 21, the coolant ascending tube 40 of this embodiment changes from a large diameter tube portion to a small diameter tube portion (the outside diameter of which is smaller than that of the large diameter tube portion) between the fuel spacer located at the lowermost position and the fuel rod supporting portion 14. The small diameter tube portion is positioned below the large diameter tube portion. The cooling water descending tube 41 is coupled to the cooling water ascending tube 40 by a support member 45. Therefore, flow vibration of the cooling water descending tube 41 due to cooling water flowing through the outside of the water rod 19A can be restricted. Further, in the similar way as the embodiment shown in later-appearing FIG. 21, the outer peripheral surfaces of both the cooling water ascending tube 40 and the cooling water descending tube 41 come into contact with cooling water. Therefore, even when these tubes are full of the vapor, the temperature of the cooling water ascending tube 40 and the cooling descending tube 41 can be lowered. In the water rod 19B of FIG. 19, the lower end of the descending tube 16 is closed and delivery ports 29 are formed in the side surface of the descending tube 16 so as not to be affected by the dynamic pressure. Finally, the structure of the boiling-water reactor in which the above-mentioned fuel assembly is loaded will now be described in conjunction with FIG. 20. A boiling-water reactor 60 has a reactor pressure vessel 61, a recirculation pump 70 and a reactor core 67 loaded with the fuel assembly 10. A reactor core shroud 62 is arranged in the reactor pressure vessel 61 and is mounted therein. Jet pumps 68 are arranged between the reactor pressure vessel 61 and the reactor core shroud 62. A lower support plate 63 of the reactor core is mounted on the lower end of the reactor core shroud 62 and is arranged therein. A plurality of fuel support metal fittings 65 penetrate through the lower support plate 63 of the reactor core and are installed on the lower support plate 63 of the reactor core. Upper lattice plates 64 are arranged in the reactor core shroud 62 and are mounted thereon. A plurality of control rod guide tubes 72 are installed in a lower plenum 71 under the lower support plate 63 of the reactor core. Housings 74 of control rod drive devices are mounted on the bottom of the reactor pressure vessel 61. A recirculation conduit 69 which communicates the reactor pressure vessel 61 with the reactor core shroud 62 it open at the upper end of the jet pumps 68. The recirculation conduit 69 is provided with the recirculation pump 70. Control rods 73 are arranged in the control rod guide tubes 72, and are linked to control rod driving devices (not shown) installed in the housings 74 of the control rod drive devices. The lower tie plates 13 of the fuel assembly 10 are inserted in and are held by the fuel support metal fittings 65, and the upper ends thereof are supported by the upper lattice plates 64. Being driven by the control rod drive devices, the control rods 73 are inserted among the fuel assemblies 10 penetrating through the fuel support metal fittings 65. The cooling water is supplied into the reactor core 67 as described below. That is, the recirculation pump 70 is driven, and the cooling water between the reactor pressure vessel 61 and the reactor core shroud 62 is injected to the upper end of jet pump 68 through the recirculation couduit 69. The cooling water between the reactor pressure vessel 31 and the reactor core shroud 62 is further intaken by the jet pump 68 as the cooling water is injected. The cooling water delivered from the jet pump 68 flows into the lower plenum 71 and into the cooling water paths 66 of the fuel support metal fittings 65, and is supplied into the fuel assembly 10 via the lower tie plate 13. When the nuclear reactor is producing the output of a low level, the control rods 72 are pulled out from the reactor core to increase the output of the nuclear reactor. The output of a high level of the nuclear reactor can be controlled by changing the number of revolutions of the recirculation pump 70 and by increasing or decreasing the flow rate in the reactor core. By pulling out the control rods and by adjusting the flow rate in the reactor core, the nuclear reactor produces a rated 100% output with a flow rate in the reactor core of 80%. The operation for compensating the decrease of reactor output due to the consumption of the core material and the poeration for shifting the flow condition in the water rod 19 from the condition of FIG. 3A to the condition of FIG. 3C, are performed by increasing the flow rate in the reactor core, i,e., by increasing the number of revolutions of the recirculation pump 70. With the recirculation pump running at a speed that produces the flow rate of smaller than 100% in the reactor core, the condition of FIG. 3A is established in the water rod 19 whereby the vapor is built up in the coolant descending path 26. With the recirculation pump running at a speed that produces the flow rate of greater than 110% in the reactor core, the condition of FIG. 3C is established in the water rod 19, and no vapor is built up. It can therefore be said that the recirculation pump 70 serves as means that controls the accumulating amount of voids (vapor) in the water rod 19. The fuel assembly 35 may be loaded in the reactor core 67 instead of the fuel assembly 10. Furthermore, the recirculation pump 70 may be replaced by an internal pump that is mounted in the reactor pressure vessel 61. The water rod 19A shown in FIG. 18A has an inverted U shape, and includes the cooling water ascending tube 40 and the cooling water descending tube 41. However, this water rod 19A is not free from the following problems. To assemble the water rod 19A, there is a way to couple the cooling water ascending tube 40 and the cooling water descending tube 41 by welding using the coupling tube 42. When they are welded, the cooling water ascending tube 40 and the coupling tube 42 are welded from outside throughout their entire periphery and then the cooling water descending tube 41 and the coupling tube 42 are welded from outside. However, if the gap between the cooling water ascending tube 40 and the cooling water descending tube 41 is small, welding between the cooling water descending tube 41 and the coupling tube 42 on the cooling water ascending tube side cannot be carried out. The reason is that since the gap between the cooling water ascending tube 40 and the cooling water descending tube 41 is small, a welding torch or a welding rod cannot be inserted into this gap. Accordingly, the cooling water ascending tube 40 and the cooling water descending tube 41 must be spaced apart from each other by a gap large enough to carry out the welding work described above. However, this results in the increase in the distance between the axes at both ends of the coupling tube 42 for individually coupling the cooling water ascending tube 40 and the cooling water descending tube 41. The fuel assembly according to still another embodiment of the present invention which solves this problem will be explained next. The fuel assembly according to still another preferred embodiment of the present invention for the boiling-water reactor will be explained with reference to FIGS. 21 and 22. The fuel assembly 10A of this embodiment includes the water rod 19C, the fuel rod 11, the upper the plate 12A, the lower tie plate 13A and the fuel spacer 16A. The upper and lower end portions of the fuel rod 11 are supported by the upper tie plate 12A and the Lower tie plate 13A, respectively. A plurality of fuel spacers 16A are disposed in the axial direction of the fuel assembly 10 A and keep the gap between the adjacent fuel rods 11 under a suitable condition. The fuel spacer 16A is held by the water rod 19C. The channel box 17 is fitted to the upper tie plate 12A and encompasses the outer periphery of the bundle of the fuel rods 11 held by the fuel spacers 16A. The lower tie plate 13A is equipped with the fuel rod supporting portion 14A at its upper end and moreover has the space 15 thereinside below the fuel rod supporting protion 14A. The fuel rod supporting portion 14A supports the lower end portion of each of the fuel rods 11 and water rod 19C. The water rod 19C includes a lower end plug 49, an ascending tube 46, a coupling portion 47, a descending tube 48 and an upper end plug 52. The water red 19C constituted by these components is made of a zirconium alloy. The ascending tube 46 has a large diameter tube portion 46A, a small diameter tube portion 46B having an outside diameter smaller than that of the large diameter portion 46A and a taper portion 46C. The taper portion 46C has a through-hole 53 therein the outside is tapered. The lower end of the large diameter tube portion 46 is coupled to the upper end of the taper portion 46C by welding. The upper end of the small diameter portion 46B is coupled to the lower end of the taper portion 46C by welding. The lower end of the small diameter tube portion 46B is coupled to the lower end plug 49 by welding. The upper end of the large diameter tube portion 46A is coupled to the coupling portion 47 by welding. The descending tube 48 is disposed in parallel with the ascending tube 46, and its upper end is coupled to the coupling portion 47 by welding. The upper end plug 52 is fitted to the upper end of the coupling portion 47. The lower end plug 49 under the condition where the water rod 19C is supported by the fuel rod supporting portion 14A is shown in magnification in FIG. 23. A path 49A is defined inside the lower end plug 49, and a coolant inlet port 51 is made in the end of the lower end plug 49. The coolant inlet port 51 is made in the side wall of the lower end plug 49 and communicates with the path 49A. The lower end plug 49 includes a projecting portion 49B the upper end of which is sealed. An opening 56 is so made on the side wall of the projecting portion 49B as to be directed sideways. The projecting portion 49B is disposed inside the small diameter tube portion 46B concentrically with the portion 46B and is positioned above the weld portion between the small diameter tube portion 46B and the lower end plug 49. Accordingly, a clad reservoir 54 is annularly formed between the small diameter portion 46B and the lower end plug 49. This clad reservoir 54 is positioned below the opening 56. The lower end plug 49 is fitted into a hole 58 defined in a boss 57 which is disposed on the lower surface of the fuel supporting, portion 14A of the lower tie plate 13A. The lower end of this hole 58 is sealed. In the side wall of the boss 57, an opening 59 directed sideways and leading to the hole 58 is made. The outer diameter of the lower end plug 49 is substantially the same as the inner diameter of the hole 58. The lower end of the path 49A extending inside the lower end plug 49 in the axial direction of the plug 49 is closed by the bottom of the boss 57. When the radiation growth of the water rod 19C due to radiation with the increase in the burnup of the fuel assembly is taken into consideration, it is preferable that the opening 59 has a margin on the higher side than the coolant inlet port 51 of the lower end plug 49 to be of greater size. Furthermore, when the possibility of the change of the positional relationship between the lower end plug 49 and the fuel supporting portion 14A from the relationship at the time of production due to combustion of the nuclear fuel, etc, is taken into consideration, it is preferable that the opening 59 has also a margin on the lower side of the coolant inlet port 51. The cooling water ascending path 25 is defined inside the lower end plug 49 and the ascending tube 46. In other words, it includes the path 49, the opening 56, the space inside the small diameter tube portion 46B, the through-hole and the inside of the large diameter tube portion 46A. The coolant inlet port 51 is positioned below the fuel supportion portion 14A and communicates with the space 15. The lower end of the descending tube 48 is sealed, and a delivery port 55 is formed in the side wall of the lower end portion of this tube 48. The delivery port 55 is positioned above the fuel supporting portion 14A. The cooling water descending path 26 is defined inside the descending tube 48. The delivery port 55 communicates with the descending path 26 and communicates with the coolant path 38 defined between the fuel rods 11 above the fuel supporting portion 14A. The coupling portion 47 has a coupling portion lower part 47A and a coupling portion upper part 47B as shown in FIG. 24. The couping portion lower part 47A and coupling portion upper part 47B are coupled to each other by welding. The large diameter tube portion 46A and the descending tube 48 are welded to the coupling portion lower part 47A. The path 36 defined inside the coupling portion 47 is for communication of the cooling water ascending path 25 with the cooling water descending path 26. Accordingly, the water rod 19C has an inverted U shape as shown in FIG. 22. Reference numeral 37A denotes a weld portion between the coupling portion lower part 47A and the ascending tube 46, 37B denotes a weld portion between the coupling portion lower part 47A and the descending tube 48, and 37C denotes a weld portion between the coupling portion lower part 47A and the coupling portion upper part 47B. The fuel spacer 16A includes a plurality of cylindrical round cells 75 that are arranged in a square grid. The round cells 75 are mutually coupled by welding. Each round cell 75 has two rigid supporting portions 75A that protrude inward. Flexible supporting members 76 are disposed on the adjacent round cells 75. The fuel rod 11 inserted into each round cell 75 is supported at three points by the two rigid supporting portions 75A and the flexible supporting member 76. Two water rods 19C and 19D are inserted into a region formed between the round cells 75 at the center of the fuel spacer 16A. The ascending tube 46 of the water rod 19C and the ascending tube 46a of the water rod 19D are positioned on one of the diagonals of the fuel spacer 16A and adjacent to each other. The descending tube 48 of the water rod 19C is positioned between a round cell 75E and a round cell 75F that are adjacent to the ascending tube 46. Similarly, the descending tube 48a of the water rod 19D is positioned between the two round cells adjacent to the ascending tube 46a and adjacent to each other. Since the descending tubes 48 and 48a are disposed between the adjacent round cells, the outside diameter of the large diameter tube portion 46A of each of the water rods 19C and 19D can be increased within such a range that seven fuel rods 11 can be disposed. This results in the increase in the transverse sectional area of the coolant ascending path 13 inside the large diameter tube portion 46A. The descending tubes 48 and 48a are positioned in mutually opposite directions in the direction of the other diagonal of the fuel spacer 16A perpendicularly crossing the diagonal described above on which the ascending tubes 46 and 46a are positioned. The ascending tube 46 is supported at three points by the rigid supporting members 27A and 27B fitted to a plurality of round cells 25 opposing to the ascending tube 46 or 46a and by the flexible supporting member 78A disposed on a bridging member fitted to the adjacent round cells 75. The ascending tube 46a is supported at three points by the rigid supporting members 27A and 27B and a flexible supporting member 78B disposed on a bridging member fitted to the adjacent round cells 75. The ascending tubes 46 and 46a supported in this manner is not in contact with each other. The descending tube 48 (having an outside diameter of about 5 mm) is supported at the large diameter tube portion 46A of the ascending tube 46 by supporting members (for example, the supporting member 45 shown in FIG. 18A), not shown in the drawings. A narrow gap is defined between the descending tube 48 and the large diameter tube portion 46A. The descending tube 48a is supported similarly by the large diameter portion 46A of the ascending tube 46a. The cross-sectional area of the cooling water descending path 26 inside the water rod 19C and the descending tube 19D is smaller than 1/25 of the cross-sectional area of the cooling water ascending path 25 (at the large diameter tube portion 46A) inside the ascending tube. Therefore, the fuel assembly 10A can have the characteristics shown by the solid line in FIG. 6 and by the single dot and dash line in FIG. 7 of U.S. Pat. No. 5,023,047. When the fuel assemblies 10A are loaded in the core, the boiling-water reactor can operate as shown in FIG. 15 of U.S. Pat. No. 5,023,047 by regulating the flow rate of cooling water supplied to the core. When the quantity of the cooling water supplied into the fuel assembly 10A having the water rods 19C and 19D each equipped thereinside with the cooling water ascending path 25 and the cooling water descending path 26 is changed, the flow condition of the fluid inside the water rods 19C and 19D changes as shown in FIGS. 3A, 3B and 3C. In other words, the fuel assembly 10A is loaded in the core of the boiling-water reactor. The flow rate of the cooling water supplied to the core is regulated by controlling the number of revolutions of a recirculation pump, not shown in the drawing. The cooling water is first guided to the space 15 of the lower tie plate 13A. The major proportion of this cooling water passes through the through-hole 18A bored in the fuel supporting portion 14A, flow into the coolant path 38 above the upper surface of the fuel supporting portion 14A and cool the fuel rod 11. Part of the rest cooling water flows into the coolant ascending path 25 of the water rod 19C through the opening 59 and the coolant inlet port 51. This also holds true for the water rod 19D. The flow of the fluid inside the cooling water ascending path 25 will be explained. The cooling water guided to the path 49A as a part of the cooling water ascending path 25 reaches the large diameter tube portion 46A through the opening 56, the small diameter tube portion 46B and the taper portion 46C. When the flow rate of cooling water supplied into the fuel assembly 10A is low, the cooling water existing inside the cooling water ascending path 25, particulary in the large diameter tube portion 46A, is heated by radiation of gamma rays generated from nuclear fission of the nuclear fuel. When the flow rate of cooling water supplied into the fuel assembly 10A is low, the cooling water turns to vapor, and a vapor region is formed inside the cooling water ascending path 25 as shown in FIG. 3A. Consequently, a liquid surface is formed inside the cooling water ascending path 25. The qenerated vapor is discharged from the coolant delivery port 55 into the cooling water path 38 throuhg the path 36 and cooling water descending path 26. As the flow rate of cooling water increases, the liquid level inside the cooling water ascending path 25 rises and the vapor region decreases. Through the condition shown in FIG. 3C, that is, the condition where the cooling water ascending path 25 and the cooling water descending path 26 are fully filled with cooling water, is finally established. Accordingly, since the change of the voidity inside the fuel assembly 10A can be enlarged between the initial stage and the final stage of the fuel cycle in this way, the effect of the spectrum shift can be increased and the period of one fuel cycle can be drastically lengthened. It is around the final stage of the fuel cycle when the insides of the cooling water ascending path 25 and the cooling water descending path 26 are fully filled with cooling water, and the vapor region is formed inside the cooling water ascending path 25 through the major proportion of the fuel cycle. Accordingly, when the cooling water descending path is so disposed as to encompass the cooling water ascending path as shown in FIG. 7A, the tube wall disposed between the cooling water ascending path and the cooling water descending path comes into contact with the vapor and its temperature becomes high because cooling is not sufficient. In this embodiment, the ascending tube 46 and the descending tube 48 are so arranged as to define the inverted U shape and moreover, the gap exists between these ascending and descending tubes 46, 48 as already described. Accordingly, the peripheries of both of the ascending and descending tubes 46, 48 are cooled by cooling water ascending in the cooling water path 38. Therefore, the temperatures of the ascending tube 46 and the descending tube 48 drop and the problem involved in the water rod and shown in FIG. 7A can be solved. The reason why the condition where the liquid surface is formed inside the water rod 19C shifts to the condition where the liquid surface is not formed by the regulation of the flow rate of cooling water supplied into the fuel assembly 10A is that the fuel supporting portion 14A functions as a resistance to the cooling water path 38 and the total cross-sectional-area of all the through-holes 18A provided in the fuel supporting portion 14A is so determined that the liquid surface can be moved. In other words, the total cross-sectional area of all the through-holes 18A is so determined as to correspond to the static head corresponding to the difference between the level at the upper end of the cooling water ascending path 25 and the level of the coolant delivery port 55. The total cross-sectional area of all the through-holes 18A made in the fuel supporting portion 14A is smaller than the cross-sectional area of the cooling water path 38. The fuel supporting portion 14A having such a construction serves as the resistance to the cooling water path 38. As described above, the cross-sectional area of the cooling water ascending path 25 inside the large diameter tube portion 46A can be increased by disposing the descending tubes 48 and 48a between the adjacent round cells 75. Accordingly, when the vapor region is formed inside the large diameter tube portion 46A, the quantity of plutonium produced increases so much more, and when the insides of the cooling water ascending path 25 and the cooling water descending path 26 are filled with the cooling water (moderator) near the end of the fuel cycle, nuclear fission of plutonium and other fission substances can be activated. Accordingly, the reactivity at the center of the cross-section of the fuel assembly 10A can be much more improved and effective utilization of the nuclear fuel can be accomplished. In other words, the effect of the improvement in fuel economy due to the spectrum shift can be further improved. The descending tubes 48 and 48a are positioned in the mutually opposite directions on the other diagonal crossing perpendicularly the diagonal on which the ascending tubes 46 and 46a are positioned. Therefore, even when the descending tubes 48 and 48a are filled with the vapor, the vapor region does not locally concentrate on the cross-section of the fuel assembly, and the fuel assemblies can be disposed in a good balance. In this way, uneven burnup of the nuclear fuel on the cross-section of the fuel assembly can be prevented. In the water rod shown in FIG. 7A, one coolant inlet port is disposed at the lower end of the cooling water ascending path. For this reason, there is the possibility that the coolant inlet port is clogged by solid matters such as clads that flow with the coolant. The smaller the diameter of the coolant inlet port, the higher becomes this possibility. In this embodiment, the cooling water inlet port 51 is so disposed as to be perpendicular to the axial direction of the cooling water ascending path, and a plurality of such inlet parts 51 are disposed in the circumferential direction of the lower end plug 49. Accordingly, cooling water flowing into the cooling water inlet ports 51 must turn at right angles immediately before the ports 51, and the possibility of clogging of the cooling water inlet port 51 by the clad, etc. is by far smaller than the possibility in the water rod shown in FIG. 7A. Furthermore, since the cooling water inlet port 51 is not disposed in the axial direction of the lower end plug 49, there is no opening in the flowing direction of the core coolant when the lower end is closed. Therefore, the influence of the dynamic pressure due to the flow can be suppressed, and variation of the liquid level inside the water rod due to variation of the dynamic pressure can be remarkably suppressed. As described above, the vapor region is formed inside the cooling water ascending path 25 in the major portion of the fuel cycle, cooling water existing inside the cooling water ascending path 25 is considered to concentrate. Therefore, the clads contained in cooling water may aggregate and settle. The opening 56 is transversely disposed lest it is clogged by the settling clads, and is positioned above the bottom surface of the path formed inside the small diameter tube portion 46B. The settling clads are gradually deposited inside the clad reservoir 54 formed between the small diameter portion and the projecting portion 49B. The capacity of the clad reservoir 54 is determined by estimating the quantity of the clads deposited during the life of the fuel assembly 10A. Next, the assembling process of the ascending tube 46, the coupling portion 47 and the descending tube 48 in this embodiment will be explained with reference to FIGS. 26A to 26D. The lower portion 47A of the coupling portion 47 has through-holes 47E and 47F as shown in FIGS. 26A to 26D, and is lower than the upper end of the lower portion 47A of the coupling portion at which the upper end of the side wall between the through-holes 47E and 47F is formed. The inside diameter of the through-hole 47E is greater than that of the through-hole 47F. FIG. 26D is a sectional view taken along line X--X of FIG. 26C. First of all, the ascending tube 46, that is, the upper end portion of the large diameter tube portion 46A, is fitted to the lower end portion of the side wall encompassing the through-hole 47E of the lower portion 47A of the coupling portion having such a construction by welding over the whole periphery of the large diameter tube portion 46A (FIG. 26A). The lower portion 47A of the coupling portion and the large diameter tube portion 46A are coupled through the weld portion 37A. Thereafter, the upper end portion of the descending tube 48 is fitted into the through-hole 47F of the lower portion 47A of the coupling portion, and the side wall encompassing the through-hole 47F of the lower portion 47A of the coupling portion and the whole periphery of the upper end portion of the descending tube 48 are coupled by welding from above (FIG. 26B). The lower portion 47A of the coupling portion and the descending tube 48 are coupled through the weld portion 37B. The lower portion 47A of the coupling portion is a coupling member for coupling the ascending tube 46 and the descending tube 48 at their upper ends. Finally, the upper portion 47B of the coupling portion is provided on the lower portion 47A of the coupling portion in such a manner as to cover the through-hole 47E of the lower portion 47A of the coupling portion and the cooling water descending path 26 inside the descending tube 48. Under such a condition, the upper end of the lower portion 47A of the coupling portion is fitted to the upper portion 47B of the coupling portion over the whole periphery by welding (FIG. 26C). The lower portion 47A of the coupling portion is integrated with the upper portion 47B of the coupling portion through the weld portion 37C. The upper portion 47B of the coupling portion is a cover member for covering the cooling water ascending path 25 and the cooling water descending path 26 from above. The upper end plug 52 is fitted to the upper portion 47B of the coupling portion by welding. As described above, in the water rod 19C used in this embodiment, the descending tube 48 is fitted into the through-hole 47F and the upper end of the descending tube 48 is fitted to the lower portion 47A of the coupling portion through the weld portion 37C. Accordingly, the whole periphery of the descending tube 48 can be easily welded to the lower portion 47A of the coupling portion. Even when the ascending tube 46 is thin, particularly the gap formed between the large diameter tube portion 46A and the descending tube 48 is thin, the whole periphery of the descending tube 48 can be easily welded to the lower portion 47A of the coupling portion. The descending tube 48 is disposed as shown in FIG. 25, and the width of the gap defined between the descending tube 48 and the large diameter tube portion 46A cannot be much increased. If the width of this gap is increased, the outside diameter of the large diameter tube portion 46A must be reduced. Since this results in the decrease in the cross-sectional area of the cooling water ascending path 25 inside the large diameter tube portion 46A, the effect of the aforementioned spectrum shift is weakened and the degree of improvement in fuel economy drops. In FIG. 25, the descending tubes 48 and 48a cannot be moved further deeply into the gap defined between the round cells 75 from the positions described above because support structural members (not shown) for supporting the descending tubes 48 and 48a on the corresponding large diameter tube portions 46A strike the adjacent round cells 75. By the weld structure of the large diameter tube portion 46A, the descending tube 48 and the lower portion 47A of the coupling portion which is obtained by the assembly method of FIGS. 26A to 26D and is shown in FIG. 24, the width of the gap between the large diameter tube portion 46A and the descending tube 48 can be reduced and the outsider diameter of the large diameter tube portion 46A can be increased. Accordingly, the cross-sectional area of the cooling water ascending path 25 can be increased, and the degree of improvement in fuel economy due to the spectrum shift effect can be increased so much more. Incidentally, since the water rod 19C receives external force through the fuel spacer 16A during earthquake, etc, a bending moment is produced in the water rod 19C. In this embodiment, the structural strength of the water rod 19C is governed by the large diameter tube portion 46A. Accordingly, from the aspect of soundness of the water rod structure, the welding between the large diameter tube portion 46A and the lower portion 47A of the coupling portion is preferably of an ordinary type. Further, the size of the lower portion 47A of the coupling portion can be reduced much more greatly by welding the large diameter tube portion 46A to the lower portion 47A of the coupling portion in the state that the lower end of the lower portion 47A of the coupling portion is inserted into the upper end of the large diameter tube portion 46A as shown in FIG. 26C than by welding contrarily the large diameter tube portion 46A to the lower portion 47A of the coupling portion in the state that the lower portion 47A of the coupling portion encompasses the outside of the large diameter tube portion 46A, as shown in FIGS. 34 and 35. This welding is preferable from the aspect of the reduction of the size of the coupling portion 47, too. In the water rods 19C and 19D used in this embodiment, the lower end plug 49 having a smaller outside diameter than that of the large diameter tube portion 46A and the small diameter tube portion 46B are arranged above the upper surface of the lower tie plate 13A (the upper surface of the fuel supporting portion 14A). Therefore, the outside diameter of the ascending tube 46 near the lower end portion, that is, at the portion which is lower than the fuel spacer 16A at the lowermost level is reduced. The portion having this reduced outside diameter has a length of about 3 to 4% of the full length of the water rods 19C, 19D in the axial direction. Even when the bending stress acts on the ascending tube 46 of each water rod 19C, 19D during an earthquake, etc, excessive stress at the lower end of the ascending tube 46 can be prevented by reducing the outside diameter of the ascending tube 46 of each water rod 19C, 19D over the range of 3 to 4% of the full length of the water rod 19C, 19D in the axial direction upward from the upper surface of the lower tie plate 13A. Besides the assembly method of the ascending tube 46, the coupling portion 47 and the descending tube 48 described above, the ascending tube 46 and the descending tube 48 can be easily welded to the lower portion 47A of the coupling portion over the whole periphery by the following method even when the gap defined between the large diameter portion 46A and the descending tube 48 is small. In this assembly method, the inside diameter of the through-hole 47E of the lower portion 47A of the coupling portion is equal to the outside diameter of the large diameter tube portion 46A of the ascending tube, 46, the large diameter tube portion 46A is inserted into the through-hole 47E, and the upper end of the large diameter tube portion 46A is welded to the lower portion 47A of the coupling portion. The descending tube 48 is welded to the side wall on the lower surface side of the lower portion 47A of the coupling portion under the state where a part of the side wall of the coupling portion encompassing the through-hole 47F is inserted into the descending tube in a manner similar to that as shown in FIG. 26A for insertion of the coupling portion into the ascending tube. The upper end of the lower portion 47A of the coupling portion is welded to the upper portion 47B of the coupling portion over the whole periphery as shown in FIG. 26C. By this second method, as shown in FIGS. 34 and 35, the coupling portion 47 is large and the pressure loss of the fuel assembly increases in comparison with the assembly method shown in FIGS. 26A to 26D. The reason is that since the large diameter tube portion 46A is inserted into the through-hole 47E, the side wall encompassing the through-hole 47E becomes necessary. The inside diameter of the through-hole 47F becomes smaller than that of the descending tube 48. In the assembly method shown in FIGS. 26A to 26D and in the method described above, the weld portions of the large diameter tube portion 46A and the descending tube 48 to the lower portion 47A of the coupling portion are shifted from each other in the axial direction. Accordingly, welding of one of them does not adversely affect welding of the other, and does not either hinder the insertion of the tube used for the other welding into the corresponding through-hole (into the lower portion 47A of the coupling portion). Another embodiment of the lower end plug of the water rod used in the embodiment described above is shown in FIG. 27. This lower end plug 49E is the one in which the lower end of the lower end plug 49 is closed. In other words, the lower end of the passage 49A is closed. The upper structure of the lower end plug 49E, not shown in the drawing, is the same as that of the lower end plug 49. The lower end plug 49E has the same effect as that of the lower end plug 49. Further, by the use of this lower end plug 49E, the boss 57 is not necessary for the fuel supporting portion 14B, and the structure of the lower tie plate 13A can be simplified. It is also possible to use a lower end plug 49F shown in FIG. 28 which is produced by swaging the lower end plug 49 described above. In this case, a round plate member for closing the passage 49 is fitted to the lower end of the lower end plug 49F. The projecting portion 49B formed on the lower end plug 49 is fitted to the upper part of the lower end plug 49F. This lower end plug 49, too, can has the same effect as that of the lower end plug 49F. FIG. 29 shows still another embodiment of the lower end plug. The lower end plug 49 of this embodiment has an opening 51A of the passage 49A. The upper structure of the lower end plug 49G is the same as that of the lower end plug 49. The lower end plug 49G has a tapered part outside the side wall encompassing the passage 49A. The formation of this taper can prevent clogging of the opening 51A by solid matters such as the clads flowing with the cooling water. However, since the opening 51A is directed in the flowing direction of cooling water, the effect of reducing the influence of the dynamic pressure is low like the opening 51 of the lower end plug 49. Another embodiment of the structure at and near the delivery port 55 of the descending tube 48 is shown in FIG. 30. In the embodiment shown in FIG. 21, the delivery port 55 is formed in the side surface of the descending tube 48 so as to suppress the influences of the dynamic pressure due to cooling water flowing outside the water rods. However, from the aspect of the suppression of the influences of the dynamic pressure due to the flow of cooling water, it is preferable to form a plurality of openings 55A in the upper surface of the header 79 in which the lower end portion of the descending tube 48A is enlarged like an inverted corn. The cooling water or the vapor descending inside the cooling water descending passage 26 flows out through the openings 55A in the flowing direction of cooling water inside the cooling water path 38. Since the delivery direction of the fluid through the openings 55A and the flowing direction of the cooling water inside the cooling water path 38 become substantially the same, discharge of the fluid through the openings 55A becomes smooth. FIG. 32 shows another example of the structure at and near the delivery port of the descending tube 48B shown in FIG. 30. This structure includes the header 79A having a slant inclining outward from the descending tube 48B on the upper surface thereof, at the lower end portion of the descending tube 48B. Four openings 55B are made on the upper slant of the header 79A in the same way as in FIG. 31. A water rod 19E as another embodiment of the water rod 19C shown in FIG. 22 is shows in FIG. 33. This water rod 19E includes a supporting portion 81 extending downward at the lower end of the descending tube 48. This supporting portion 81 is inserted into the fuel supporting portion 14A of the lower tie plate 13A. According to such a structure, the supporting force of the descending tube 48 can be increased, and the possibility of flow vibration of the descending tube 48 due to the flow of cooling water flowing inside the cooling water descending tube 38 can be reduced. Since the radiation growth quantity of the fuel rod 11 due to the radiation is greater than that of the water rod 19E, the water rod 19E moves upward through the fuel spacer 16A depending on the difference of the radiation growth quantity between the water rod 19E and the fuel rod 11. The lower end plug 49 of the ascending tube 46 has a sufficient length such that it does not come off the fuel supporting portion 14A due to the upward movement described above.
	description	FIG. 1 is an illustration of a radiographic imaging arrangement. A tube 1 such as an x-ray tube generates and emits x-ray radiation 2 which travels toward a body 3 such as a portion of the body of a patient. Some of the x-ray radiation path 4 is absorbed by body 3, some of the x-ray radiation penetrates and travels along paths 5 and 6 as primary radiation, and still other radiation is deflected and travels along path 7 as scattered radiation. Paths 5, 6, and 7 are exemplary and presented by way of illustration and not limitation. Radiation from paths 5, 6, and 7 travels toward a photosensitive film 8 where it is absorbed by intensifying screens 9 which are coated with a photosensitive material that fluoresces at a wavelength of visible light and thus exposes photosensitive film 8 (the radiograph) with the latent image. Alternatively, instead of a photosensitive film, a detector such as a digital x-ray detector (not shown) may be suitably employed. For example, a suitable detector may include a cesium iodide phosphor (scintillator) on an amorphous silicon transistor-photodiode array having a pixel pitch of about 100 micrometers. Other suitable detectors may include a charge-coupled device (CCD) or a direct digital detector which converts x-rays directly to digital signals. While the photosensitive film is illustrated as being flat and defining a flat image plane, other configurations of the photosensitive film and digital detectors may be suitably employed, e.g., a curved-shaped photosensitive film or digital detector having a curved image plane. An illustrated anti-scatter grid 10 (or collimator) of the present invention is interposed between body 3 and photosensitive film 8 so that radiation paths 5, 6, and 7 intersect anti-scatter grid 10 before reaching film 8. By way of example and not limitation, radiation path 6 travels through one of a plurality of generally non-radiation absorbing elements 11 of anti-scatter grid 10, whereas both radiation paths 5 and 7 impinge upon different ones of a plurality of generally radiation absorbing elements 12 and become absorbed. The absorption of the scattered beam along radiation path 7 eliminates adverse scattered radiation. The absorption of the beam along radiation path 5 eliminates a portion of the primary radiation. Radiation path 6, representing the remainder of the primary radiation, travels toward the photosensitive film 8 (or other detector) and becomes absorbed by the intensifying photosensitive screens 9 that fluoresce at a wavelength of visible light and thus exposes photosensitive film 8 with the latent image. The generally non-radiation absorbing elements 11 exhibit a reduced radiation absorption of the radiation used in radiography compared to the generally radiation absorbing elements 12. Desirably, the generally radiation absorbing elements comprise a material and height (which varies based on the angle of the strip as discussed below) operable to absorb at least 90 percent, and preferably at least 95 percent, of the primary radiation which encounters the generally radiation absorbing elements. The generally non-radiation absorbing elements are sized and configured as discussed below and operable to permit passage of at least 90 percent, and preferably at least 95 percent of the primary radiation which encounters the generally non-radiation absorbing elements. FIG. 2 is an enlarged cross-sectional side view of a portion of anti-scatter grid 10 of the present invention. The plurality of generally radiation absorbing elements 12 comprises, for example, strips of spaced-apart lead foil. Other suitable generally radiation absorbing materials include tungsten or tantalum. Outer protective covers 22 and 24, typically formed from a graphite epoxy composite, are disposed on the top and the bottom surface for protection of the alternating layers of the generally radiation absorbing elements and the generally non-radiation absorbing elements. As best shown in FIG. 3, the plurality of generally non-radiation absorbing elements 11 comprises a composite of moldable epoxy or polymeric material 13 and a plurality of hollow air or gas filled microspheres 15. The plurality of hollow microspheres 15 define a respective plurality of voids 17 in generally non-radiation absorbing element 11. Providing voids in the generally non-radiation absorbing elements reduces the amount of attenuation and scatter caused within the anti-scatter grid compared to solid generally non-radiation absorbing elements. In addition, occupying or filling generally the entire interspace between the spaced-apart generally radiation absorbing elements with the generally non-radiation absorbing elements having a plurality of voids results in anti-scatter grid 10 being structurally robust and capable of absorbing less primary radiation than a conventional anti-scatter grid having solid interspace material and permits a reduction in the amount of radiation necessary to properly expose a photosensitive film or detector during radiography while yielding high resolution and high contrast radiographic images. The hollow microspheres typically are made of plastic or glass. The hollow microspheres are mixed with an epoxy or other polymer binder to form desirably a rigid material for forming the generally non-radiation absorbing elements. For example, the hollow microspheres commonly are used in a volume fraction resulting in the generally non-radiation elements having about one-quarter of the density of the epoxy or binder alone. Desirably, the epoxy or binder is heat curable so that it can be hardened, e.g., using heat, in a short period of time to allow an anti-scatter grid to be quickly built up a layer at a time, as described in greater detail below. The average particle size of the hollow microspheres, e.g., the average outer diameter of the spheres, is between about 20 microns and about 150 micrometers, and desirably about 50 micrometers. Suitable glass hollow microspheres include 3M SCOTCHLITE glass bubbles manufactured by 3M Speciality Materials of St. Paul, Minn. Suitable plastic or polymeric hollow microspheres include PHENOSET phenolic microspheres manufactured by Asia Pacific Microspheres Sdn Bhd of Selangor, Malaysia. The above-noted products are offered as examples. From the present description, it will be appreciated by those skilled in the art that various other materials such as glass, ceramic, or plastic materials or composites thereof may be used for forming the hollow microspheres. In addition, various other epoxy or polymeric materials may be suitably used for the binder or filler interspace material. In addition, from the present description, it will be appreciated by those skilled in the art that other materials having voids also may be used for the generally non-radiation absorbing elements as the voids therein reduce the radiation absorption and scatter of the radiation while exhibiting sufficient structural integrity compared to the material in solid form. For example, such alternative materials include expanded plastics, open cell foam, closed cell foam, or the like. For example, materials used in a large number of expanded or foamed compositions include cellulose acetate, epoxy resins, styrene resins, polyester resins, phenolic resins, polyethylene, polystyrene, silicones, urea-formaldehyde resins, polyurethanes, latex foam rubbers, natural rubber, synthetic-elastomers, polyvinyl chloride, and polytetrafluoroethylene. With reference again to FIG. 2, for medical diagnostic radiography, the grid ratio, which is defined as the ratio between the height h between respective interior surface of protective covers 22, 24 and the average distance d (e.g., taken along a centerline of the grid) between them generally ranges from 2:1 to 16:1. Typical dimensions of the radiation absorbing strips include a height (which varies based on the angle of the strip) and thickness t of about 1.5 millimeters and about 0.02 millimeter, respectively, and a pitch between the strips of about 0.3 millimeter. FIG. 4 illustrates an apparatus 40 for forming an anti-scatter grid for radiography. Advantageously, apparatus 40 is operable to stack the various layers of the generally radiation absorbing elements and the generally non-radiation absorbing elements, as well as angle the generally radiation absorbing elements to align with a radiation source (for example, to align with angles A1, A2, . . . , An, as shown in FIG. 1). Apparatus 40 generally includes a support 42, an elongated arm 50, a stand 60, and positioning means 70. Arm 50 includes a first end portion 52 and an opposite second end portion 54. First end portion 52 of arm 50 is pivotally attached to a pivot 44 of support 42 so that first end portion 52 is pivotable about an axis A (shown extending into the page in FIG. 4) and so that second end portion 54 is movable through an arc C. Second end portion 54 of arm 50 includes a generally planar-shaped surface 56 aligned with axis A. Axis A and stand 60 are spaced apart to correspond with the positioning of a radiation source and the anti-scatter grid during radiography. The operation of apparatus 40 to form an anti-scatter grid 110 is as follows. Initially, a radiation absorbing element 112 such as a lead foil which is sized larger than the desired final anti-scatter grid height, is positioned on an angled surface 62 of stand 60 which desirably corresponds to the angle (e.g., the angle with respect to the path of the center beam of the fan spread of beams emanating from the x-ray source) of an outermost generally radiation absorbing element. A bead of desirably moldable epoxy or polymeric material is deposited on the lead foil to form non-radiation absorbing element 111. Thereafter, the next radiation absorbing element 112, which is also larger than the desired final anti-scatter grid height, is attached to surface 56 of arm 50. Arm 50 is lowered to a spaced-apart position from the first lead foil 112. Desirably, positioning means 70 such as a precision linear actuator can be conventionally controlled to stop arm 50 at a desired position to position the lead foil. Advantageously, surface 56 is heated. For example, heating means 58 for heating surface 56 may include a heater or a heating coil. Use of a heated surface allows heating the lead foil, which heated lead foil in turn, heats the epoxy or polymeric material to reduce the time necessary to sufficiently cure and harden the epoxy or polymeric material before applying the next layers. This process is repeated until the desired overall grid size is achieved (about 1,000 layers). From the present description, it will be appreciated by those skilled in the art that for where the angle of the strips relative to the radiation source is small, e.g., a few degrees, surface 62 may be horizontal. While the outermost strip will not be aligned with the axis or radiation source, the interspace material allows the next and remaining layers to be aligned with a radiation source. It will also be appreciated that stand 60 may include an adjustable vertically positionable surface to accommodate various size anti-scatter grids. The monolithic mass is then machined to the desired anti-scatter grid thickness. As shown in FIG. 5, an anti-scatter grid 110 (or colliminator) formed using apparatus 40 includes alternating layers of generally radiation absorbing elements 112 and solid generally non-radiation absorbing elements 111. Alternatively, an anti-scatter grid having generally non-radiation absorbing elements with voids, as described above, may be formed using apparatus 40. Protective outer layers 122 and 124, typically graphite-epoxy composite, are laminated on both sides to form a protective outer cover to protect the generally radiation absorbing elements and generally non-radiation elements absorbing from scratches. Any of a variety of finishing techniques such as polishing, painting, laminating, chemical grafting, spraying, gluing, or the like, may be employed to clean or encase the grid to provide overall protection or aesthetic appeal to the grid. Furthermore, the protective layer is useful for safety concerns when the radiation absorbing elements include a metal such as lead. From the present description, it will be appreciated by those skilled in the art that the positioning means for adjusting the positioning of the spaced-apart radiation absorbing elements may include servo actuated motors, gears, and other suitable mechanisms. Desirably, the depositing of the curable non-radiation absorbing material, and the depositing and the positioning of the radiation absorbing layers are performed automatically. The attenuation in the anti-scatter grid of the present invention may be made low and without appreciably increasing the amount of radiation used (e.g., the dose experienced by the patient) and a further reduction in the scattered radiation may be achieved by stacking two anti-scatter grids with the radiation absorbing strips of the first anti-scatter grid orientated orthogonally compared to the orientation of the radiation absorbing strips of the second anti-scatter grid. Thus, while various embodiments of the present invention have been illustrated and described, it will be appreciated to those skilled in the art that many changes and modifications may be made thereunto without departing from the spirit and scope of the invention.
	description	This application is a continuation of now pending U.S. patent application Ser. No. 13/710,172, filed on Dec. 10, 2012 and titled “APPARATUSES AND METHODS EMPLOYING MULTIPLE LAYERS FOR ATTENUATING IONIZING RADIATION” (“the '172 Application”), which is a continuation-in-part of U.S. patent application Ser. No. 13/663,467, filed on Oct. 29, 2012 and titled “NUCLEAR RADIATION SHIELDS, SHIELDING SYSTEMS AND ASSOCIATED METHODS” (“the '467 Application”), and a continuation-in-part of U.S. patent application Ser. No. 12/897,611, filed on Oct. 4, 2010 and titled “RADIO-OPAQUE FILMS OF LAMINATE CONSTRUCTION” (“the '611 Application”), which is a continuation-in-part of U.S. patent application Ser. No. 12/683,727, filed on Jan. 7, 2010 and titled “RADIATION PROTECTION SYSTEM” (“the '727 Application”), each of which is incorporated herein by reference in its entirety. This disclosure relates generally to the attenuation of ionizing radiation and, more specifically, to compositions, structures and methods for attenuating ionizing radiation. More specifically, this disclosure relates to the use of multiple layers of materials for attenuating ionizing radiation and, even more specifically, to the concurrent use of multiple layers that attenuate different energies of the spectrum of ionizing radiation together to limit a subject's exposure to ionizing radiation. Ionizing radiation includes particles (e.g., neutrons, electrons, positrons, neutrinos, photons, etc.) that individually carry enough energy to liberate an electron from an atom or a molecule, ionizing the atom or molecule. Examples of ionizing radiation include, but are not limited to, neutrons travelling at any speed, alpha rays, beta rays, gamma rays and x-rays. When living tissues are exposed to high doses of ionizing radiation over a relatively short period of time, the ionizing radiation is likely to cause damage to those tissues. There are a number of environments in which individuals may be exposed to the potentially harmful effects of ionizing radiation. Physicians and allied clinical personnel, collectively referred to as “healthcare providers,” are commonly involved in medical procedures on patients in which fluoroscopic and other types of radiation systems (such as computer tomography, or CT, systems) are used. These radiation systems allow the healthcare providers to peer into the body systems of a patient and view a portion of the anatomy of a subject (e.g., a patient, an individual, etc.) with minimal invasiveness. The images generated may be in the form of a single image, or a video feed, both of which may be viewed in real-time. Radiation systems enable diagnosis, as well as the guidance of medical devices, such as catheters and surgical devices, to desired locations within the body of a subject and, in some cases, use of the medical devices at the desired locations. One of the concerns arising from the increased use of fluoroscopic radiation systems in medical procedures is the amount of radiation exposure to both healthcare providers and patients. Epidemiological data suggest that exposure to as “little” as 5 rem to 10 rem over an individual's lifetime increases the risk that the individual will develop cancer. Literature also suggests that there is no lower threshold on the amount of radiation that could be considered acceptable. Further, studies have shown that elevated radiation exposure levels can be expected when larger body parts of a subject are imaged, or when parts of a healthcare provider's body, such as his or her extremities, are positioned closer to the source of ionizing radiation or directly in the field of ionizing radiation (as opposed to scattered ionizing radiation outside of the field). While there is constant debate about levels of ionizing radiation to which a subject may be exposed before suffering tissue damage, and these levels are occasionally revised as more information is gathered, the cumulative effects of consistent exposure to ionizing radiation are still unknown. That is, while the selected dose of radiation used in any one imaging sequence may normally be well below an exposure limit that is considered to be safe, repeated exposure of healthcare providers and/or patients to even low levels of ionizing radiation may be cumulatively unsafe. Recent investigations in medical diagnostics practices suggest that the dose and exposure of an individual to ionizing radiation should follow the “As Low As Reasonable” approach. For instance, members of the surgical team using fluoroscopic imaging techniques may be unnecessarily exposed to x-rays when performing surgery on a patient. As an example, in diagnostic procedures using x-rays or computed tomography (CT) scans, a radiologist may have to hold a patient such as an infant, or an animal in the case of veterinary work, to restrain the movement of the patient in order to obtain satisfactory image resolution. In these cases, at a minimum, the hands of the radiologist or other healthcare providers may be exposed to harmful ionizing radiation. Additionally, repeated exposure across multiple procedures on one or more patients may also increase the risk of radiation exposure to the healthcare providers. Healthcare providers are not the only ones in healthcare settings who may be subjected to high levels of ionizing radiation over time. The exposure of patients to ionizing radiation is also ever-increasing, as the use of ionizing radiation in healthcare becomes more common. For example, mobile C-arm image intensifiers, as fluoroscopic imaging systems, are increasingly used in operating rooms, outpatient clinics, and emergency departments to image larger, denser areas of a subject's body (e.g., the pelvis, the spine, etc.). Images are taken during both non-elective surgical procedures and elective surgical procedures, and often result in the exposure of nontargeted tissues (e.g., bones; muscles; other, more sensitive visceral organs; etc.) to ionizing radiation. Further, the number of times to which a subject will be exposed to ionizing radiation during his or her lifetime has increased, resulting in higher accumulated doses, which increases the risk of harm to the subject. In an effort to minimize exposure to potentially harmful ionizing radiation in healthcare settings, lead aprons are used, when possible, to protect both healthcare providers and patients. A lead apron effectively prevents ionizing radiation incident to an outside of the apron from passing through to and exiting the inside of the apron and, as such, protects whatever is on the inside of the apron from the ionizing radiation. For instance, when imaging a targeted body part of a patient, one or more lead aprons may be arranged on one or more non-targeted body parts of the patient to enable a targeted body part to be exposed to ionizing radiation while minimizing exposure of each covered, non-targeted body part to the ionizing radiation. As another example, healthcare providers may wear lead aprons to protect themselves from the ionizing radiation to which they subject their patients. Nevertheless, lead aprons are typically heavy and, to enable healthcare providers to freely use their arms and hands to conduct medical procedures, are usually not configured to cover arms or hands; thus, lead aprons usually provide only limited protection from ionizing radiation. In recognition of the desirability for additional protection, gloves that attenuate ionizing radiation have been developed. Conventionally, such radiation attenuating gloves have included a heavy metal (e.g., lead (Pb), cadmium (Cd), tungsten (W), bismuth (Bi), etc.) or a heavy metal compound, such as bismuth oxide. Some radiation attenuating gloves are made of a flexible polymer through which the heavy metal or heavy metal compound is dispersed. Alternatively, a flexible glove may be dipped into a mixture containing a heavy metal or heavy metal compound. Although these gloves block ionizing radiation, they expose a wearer to toxic heavy metals. Furthermore, heavy metal-based gloves that attenuate ionizing radiation are typically cumbersome and inflexible, which may restrict agile hand movements that may be necessary for delicate procedures and reduce dexterity and the tactile sensation upon which healthcare providers often rely as a secondary source of information while viewing images obtained with the ionizing radiation (e.g., while guiding medical instruments, as fingers or hands are inside of a patient or otherwise hidden from direct view, etc.). Heavy metal-based gloves that attenuate ionizing radiation may also be prone to breaking or tearing, as heavy metals are often incorporated in concentrations that may compromise the tear resistance of the glove. When such a glove is broken or torn, the individual wearing the glove is exposed to ionizing radiation, and to even further amounts of the toxic heavy metals that are used to make the glove. Unfortunately, healthcare providers do not typically wear radiation attenuating gloves. As a result, a healthcare provider's hands and arms may be cumulatively subjected to unacceptably high levels of ionizing radiation. Ionizing radiation is also common in environments where radioactive materials are typically present, such as in nuclear power facilities or nuclear recycling or waste facilities. Because of likelihood that individuals who work in such environments will be exposed to ionizing radiation, they are typically required to carry dosimeters. A dosimeter measures the quantity of nuclear radiation, or radioactivity, to which an individual is exposed. Knowledge of an individual's exposure to nuclear radiation is important, particularly in environments where individuals are not provided with protective suits or other protective garments and since governmental and/or private regulations often limit the dosage of nuclear radiation to which an individual may be exposed over a given period of time. Typically, the maximum annual dosage of radiation for individuals who routinely work around radioactive materials and other types of ionizing radiation is 5,000 millirems (mrem). Radiation blankets are often used to limit an individual's exposure to nuclear radiation in environments where relatively high levels of radioactivity are present. More specifically, one or more radiation blankets may be positioned over areas where exposure to nuclear radiation is most likely. The use of radiation blankets is intended to decrease the cumulative dosage of nuclear radiation to which an individual is exposed, as measured by a dosimeter used by the individual. Thus, when radiation blankets and other radiation shields are properly used, the total amount of time each individual may work in that environment over a given period of time may be increased, which may reduce employee downtime and, thus, improve worker efficiency. Radiation blankets are often formed from a single material such as lead plate or lead wool. Another form of a radiation blanket made from a single attenuating material is in the form of a polymer that is impregnated with particles of tungsten, iron ore, some combination of tungsten and iron ore, heavy metals, or heavy metal compounds. Lead plate is typically dense and provides an effective barrier to the ionizing particles of nuclear radiation, or radioactivity, emitted by radioactive materials. Although lead is flexible for a metal, lead plate is still relatively rigid and somewhat brittle and, thus, subject to cracking and/or breaking. Lead wool, in contrast, includes fine strands of lead (e.g., strands having diameters of 0.005 inch to 0.015 inch) of varying lengths that are woven, or interlaced, with one another and pressed together, or compacted. While lead wool is much less dense that lead plate, it is much more flexible. Nonetheless, the flexibility of compacted lead wool is still limited, and lead wool is very friable, easily subject to cracking or breakage and unraveling of the compacted lead strands. Such cracking may lead to gaps in radiation protection, resulting in leakage of harmful radiation. Further, broken particles and strands of lead settle to the bottom of the blanket over time, leading to non-uniform attenuation across the surface of the blanket, which may then require users to add extra shielding, in turn leading to higher stresses on structures and potentially requiring costly modifications of shielded structures. Tungsten or iron based radiation blankets are more flexible and less susceptible to cracking or damage than lead wool radiation blankets. However, these radiation blankets are often relatively thick and, as a result, lack a desirable degree of flexibility. Furthermore, over time, particularly when exposed to high temperatures and nuclear radiation, the polymer of tungsten-based radiation blankets hardens, which may render it less flexible and more prone to cracking. Another problem associated with employing a single material such as tungsten or iron ore for attenuating radiation is that such materials release additional photons by themselves due to the photoelectric effect. Regardless of the construction of a radiation blanket, cracks or breaks in its radioactivity-attenuating materials provide additional passages through which ionizing particles may pass. Furthermore, since the blanket is made from a toxic material such as lead, after use, the radiation blanket becomes a mixed waste, or waste that contaminated with both radioactivity and toxic materials, regardless of whether the blanket was intact or cracked or broken. In view of the toxicity of lead, its release from a radiation blanket is considered to be highly undesirable and requires prohibitively expensive remedial actions. As a radiation blanket that employs a single attenuating material, such as lead or tungsten, attenuates nuclear radiation, the photo-electric effect may cause that attenuating material to generate additional photons. Since these additional photons may also be harmful, the ability of radiation blankets that rely on a single material to attenuate radioactivity and, thus, to minimize the doses of radioactivity or other ionizing radiation to which personnel may be exposed may be less than ideal. A “radiation shield,” as that term is used herein, is a film, coating, layer or other structure that includes one or more attenuating elements. An “attenuating element” is a feature of a radiation shield that includes an attenuating material. An “attenuating material” is a material that attenuates ionizing radiation, or a so-called “radio-opaque material.” “Ionizing radiation” is radiation composed of particles (e.g., neutrons, electrons, positrons, neutrinos, photons, etc.) that individually carry enough to liberate an electron from an atom or a molecule, ionizing the atom or molecule. Examples of ionizing radiation include, but are not limited to, neutrons travelling at any speed, alpha rays, beta rays, gamma rays and x-rays. The term “multiple,” as used in this disclosure, refers to two or more occurrences of an element. Thus, the phrase “multiple attenuating elements” is indicative of two or more attenuating elements. Similarly, the phrase “multiple layers” signifies two or more layers. A radiation shield according to this disclosure includes two or more attenuating elements that may be organized in a manner that increases the efficiency with which ionizing radiation is attenuated and, in some embodiments, minimizes one or more of the weight or thickness of the radiation shield or improves the flexibility of the radiation shield. The attenuating materials that different attenuating elements include may be based upon elemental species having different atomic numbers. Two or more attenuating elements of a radiation shield may attenuate ionizing radiation of different energies or different ranges of energy. The radiation shield may include a first side, or an outside, and an opposite second side, or inside. The outside of the radiation shield may be configured to be positioned closest to, or to face, a source of ionizing radiation, while the inside of the radiation shield may be configured to face away from the source of ionizing radiation, and to be positioned closest to one or more subjects or objects that are to be shielded from the ionizing radiation. In such an embodiment, an attenuating element at or near the outside of the radiation shield may be configured to attenuate relatively high energy ionizing radiation, while an attenuating element at or nearer to the inside of the radiation shield may be configured to lower energy ionizing radiation, which may result from attenuation of the relatively high energy ionizing radiation, and which may be more damaging to living tissues than the relatively high energy ionizing radiation. In more specific embodiments, a first attenuating element located closer to the outside of the radiation shield may comprise a relatively low atomic number, or “low Z,” attenuating material, while a second attenuating element located closer to the inside of the radiation shield may comprise a relatively high atomic number, or “high Z,” attenuating material. A radiation shield may be configured to be assembled with and secured to one or more other radiation shields to provide a radiation shield with a larger area. In some embodiments, features that enable a radiation shield to be assembled with and secured to another radiation shield may also be configured to enable disassembly of the radiation shields. A variety of means for assembly may be employed, including, without limitation, quick-connect latches, complementary hook and loop elements (e.g., VELCRO®, etc.), magnets and/or magnetically attractable elements, snaps, zippers, adhesive elements, and the like. In a specific embodiment, the attenuating elements of a radiation shield may comprise two or more superimposed layers, each of which includes an attenuating material. In embodiments where a radiation shield includes more than two attenuating layers, the layers may be arranged progressively; for example, based on the atomic numbers of the elements upon which their attenuating materials are based, based on the energies of ionizing radiation that they will attenuate, etc. Alternatively, the attenuating layers of a radiation shield may be arranged in a repetitive, alternating order (e.g., A, B, A, B, . . . ; A, B, C, A, B, C, . . . ; A, A, A, B, B, B, . . . ; etc.). Any of the foregoing teachings may be applied to a variety of embodiments of radiation shields. Without limitation, a radiation shield may include a structure (e.g., a garment, drape, blanket, etc.) that includes a two or more superimposed layers, a plurality of films resulting from separately applied topical compositions, a combination of different single layer and/or multiple layer attenuating elements (e.g., a film, layer or structure including a first attenuating material and at least one other film, layer or structure including a second attenuating material, etc.). A method for attenuating ionizing radiation includes positioning a shield between a source of ionizing radiation and a subject to be shielded from the ionizing radiation. The shield is positioned in such a way that a first attenuating element that includes a first attenuating material is located nearer to the source of ionizing radiation and a second attenuating element that includes a second attenuating material is located nearer to the subject to be shielded. In such an arrangement, the first attenuating material may be based an element that has a lower atomic number (i.e., a relatively low Z material) than the atomic number of an element upon which the second attenuating material is based (i.e., a relatively high Z material). Other aspects, as well as features and advantages of various aspects, of the disclosed subject matter will become apparent to those of ordinary skill in the art through consideration of the ensuing description, the accompanying drawings and the appended claims. A variety of embodiments of radiation shields that include multiple attenuating elements are within the scope of this disclosure. In some embodiments, such as that depicted by FIG. 1, a radiation shield 30 may include attenuating elements 32a and 32b (collectively, “attenuating elements 32”), such as the depicted layers or other structures (e.g., coatings, stratified structures, graded structures, etc.) that have different properties from one another. The attenuating elements 32 of such an embodiment may be arranged in any order. For example, the attenuating elements 32 may be arranged vertically relative to one another (i.e., in at least partially superimposed relation), in a more horizontal manner (i.e., laterally adjacent to one another) (e.g., in matrices, into quasi-random structures, into random structures, etc.) or in a combination of vertical and horizontal relations. In some implementations, the order and/or positioning of (e.g., spacing between, etc.) attenuating elements 32 that have different physical characteristics from one another may be designed or configured to impart the radiation shield 30 with one or more desired characteristics. As an example, attenuating elements 32 with different properties may be arranged in a way that increases the range or ranges of energies of ionizing radiation that may be attenuated by the radiation shield 30. Each attenuating element 32a that includes a first type of attenuating material may be configured to attenuate ionizing radiation of a first energy or a first range of energies, while each attenuating element 32b that includes a second type of attenuating material may be configured to attenuate ionizing radiation of a second energy or a second range of energies. More specifically, each attenuating element 32a that includes the first type of attenuating material may be configured to attenuate relatively high energy ionizing radiation, while each attenuating element 32b that includes the second type of attenuating material may be configured to attenuate relatively low energy ionizing radiation. Depending on the source of ionizing radiation, the energy spectrum and/or other factors, other arrangements may be utilized, including, without limitation, a reverse configuration to that disclosed by this paragraph. As a more specific example, the attenuating elements 32 may be arranged in a manner that attenuates incident ionizing radiation, as well as lower energy, secondary ionizing radiation that may result from attenuation of the incident ionizing radiation. In a specific embodiment, the attenuating elements 32a and 32b of a radiation shield 30 may have at least two different ionizing radiation-attenuating characteristics. In an even more specific embodiment, the radiation shield 30 may include attenuating elements 32a and 32b with two different ionizing radiation-attenuating characteristics. The attenuating elements 32a and 32b may be organized so that the atomic number(s) of the element(s) or elemental specie(s) upon which the attenuating material of each attenuating element 32a, 32b, etc., is based may increase across the thickness of the radiation shield 30; i.e., each attenuating element 32a may comprise a relatively low Z material, while each attenuating element 32b may comprise a relatively high Z material. A radiation shield 30 that includes an attenuating element 32a with a relatively low Z attenuating material and another attenuating element 32b with a relatively high Z attenuating material may be used in a manner that optimizes the attenuation of radiation, such as nuclear radiation or other ionizing particles. As an example, when a radiation shield 30 that includes one or more attenuating elements 32a of relatively low Z attenuating material 45 and one or more attenuating elements 32b of relatively high Z attenuating material 46 is used to decrease the amount of radiation present at a particular location, as illustrated by FIG. 1, the radiation shield 30 may be positioned between a source S of radioactivity in an orientation that places at least one attenuating element 32a including the relatively low Z attenuating material 45 closer to the source S than at least one attenuating element 32b that includes the relatively high Z attenuating material 46. When incident ionizing radiation X1 passes through the attenuating element 32a that includes the relatively low Z attenuating material 45, the relatively low Z attenuating material 45 absorbs and, thus, attenuates at least some of the incident ionizing radiation X1. As the low Z attenuating material 45 absorbs the incident ionizing radiation X1, the atoms, or elemental species, of the relatively low Z attenuating material 45 may be excited to a state that causes them to release further, secondary ionizing radiation X2. The secondary ionizing radiation X2 may have a lower energy than the incident ionizing radiation X1. As a consequence, the relatively low Z attenuating material 45 of attenuating element 32a may not attenuate the secondary ionizing radiation X2 as well as it attenuates the incident ionizing radiation X1, if it attenuates the secondary ionizing radiation X2 at all. Moreover, the relatively low energy secondary ionizing radiation X2 is more likely than the incident ionizing radiation X1 to be absorbed by the tissues of an individual's body and, thus, be more damaging to the individual. Nevertheless, before that secondary ionizing radiation X2 can reach the individual, it must pass through at least one attenuating element 32b that includes a relatively high Z attenuating material 46, which includes ionizing radiation-attenuating species that may attenuate the secondary ionizing radiation X2 better than the relatively low Z attenuating material 45 of layer 32a. Thus, the relatively high Z attenuating material 46 of attenuating element 32b may reduce the amount of secondary ionizing radiation X2 that reaches the individual, if not totally prevent exposure of the individual to the secondary ionizing radiation X2. FIGS. 2 through 4 depict embodiments of radiation shields 30′, 30″ and 30′″, respectively, that include more than two layers, or attenuating elements 32a, 32b, etc. The radiation shield 30′ shown in FIG. 2 includes attenuating elements 32a, 32b, 32c, etc., with one or more characteristics that differ from one attenuating element 32 to another. The attenuating elements 32a, 32b, 32c, etc.) are arranged in such a way that at least one characteristic progresses from one side 38′ of the radiation shield 30′ to the opposite side 39′ of the radiation shield 30′. As a non-limiting example, the attenuating elements 32 may be arranged in an order that corresponds to an atomic number of an elemental species upon which an attenuating material of each attenuating element 32 is based. As another non-limiting example, the order in which the attenuating elements 32 are arranged may be based on an energy of ionizing radiation attenuated by each of the attenuating elements 32. Of course, other bases for progressively arranging the attenuating elements 32 of a radiation shield 30′ are also within the scope of this disclosure. As depicted by FIG. 3, a radiation shield 30″ may also include attenuating elements 32 that are arranged in an alternating, repetitive manner. In the embodiment depicted by FIG. 3, the radiation shield 30″ includes two different types of radiation shields 32a and 32b, which are repetitively arranged from one side 38″ of the radiation shield 30″ to the opposite side 39″ of the radiation shield 30″ (i.e., 32a, 32b, 32a, 32b, etc.). FIG. 4 illustrates an embodiment of radiation shield 30″ in which attenuating elements 32a, 32b, 32c are organized progressively from one side 38 of a radiation shield to an internal location 37 within the radiation shield 30 in a first manner (e.g., 32a, 32b, 32c, etc.), then progressively in an opposite, second manner (e.g., 32c, 32b, 32a) from the internal location 37 to the opposite side 39 of the radiation shield 30′. Of course, other arrangements of attenuating elements 32 in a radiation shield 30 are also within the scope of the disclosed subject matter, including, without limitation, random arrangements and pseudo-random (i.e., non-progressive, non-repetitive, etc.) arrangements. In some embodiments, as illustrated by FIG. 5, a radiation shield 30″ may include two or more different types of attenuating elements 32, but include two or more directly adjacent attenuating elements 32a, 32b of the same type. In the depicted embodiment, first and second attenuating elements 32a and 32a′ comprise the same attenuating material, while a third attenuating element 32b comprises a different attenuating material. This concept of adjacent attenuating elements 32 of the same type may be applied to any other arrangement of attenuating elements 32, including progressive, repetitive and pseudo-random arrangements. With returned referenced to FIG. 1, the foregoing teachings may be applied to a variety of different types of radiation shields 30. A variety of materials and structures may also be used to form one or more of the attenuating elements 32 of a radiation shield 30. An attenuating element 32 of a radiation shield 30 may be formed from any material that will attenuate ionizing radiation in the desired manner. Without limitation, the attenuating material of the attenuating element 32 may comprise a non-toxic material that comprises or is based upon an element or elemental species or compound having an atomic number of 56 or greater. Non-limiting examples of such elements or elemental species include barium (Ba) species, bismuth (Bi) species and lanthanum (La) species. Specific examples of such inorganic salts include, but are not limited to, barium sulfate (BaSO4) and bismuth oxide (Bi2O3). Non-limiting examples of attenuating elements 32 include layers, films (e.g., films formed by different topical compositions, such as those disclosed by the '611 Application and the '727 Application, etc.), foils, interlocking panels, strands, mesh, threads, fabrics, mesh, webs, tubes, pipes, or other structures. In some embodiments, one or more attenuating elements 32 of a radiation shield 30 may include particles of an attenuating material that are held together by or dispersed throughout a polymer. In a specific embodiment, one or more attenuating elements 32 of a radiation shield 30 may comprise layers having the construction disclosed by the '467 Application. As depicted by FIG. 6, such an attenuating element 32 may include particles 42 of an attenuating material that are held together by or dispersed throughout a polymer 44. A number of factors, such as the type(s) of polymer(s) used, the size(s) and/or morphologies of the particles 42 of the attenuating material(s), the relative proportions of the attenuating material(s) and the polymer(s), and/or the thickness of the attenuating element 32, may affect the flexibility, durability, and/or other characteristics of the attenuating element 32. While FIG. 6 shows an attenuating element 32 throughout which the particles 42 of attenuating material are dispersed homogeneously or substantially homogeneously, attenuating elements with non-homogeneous particle 42 distributions (e.g., gradients, random distributions, etc.) are also within the scope of this disclosure. Without limiting the possible scope of materials, proportions, characteristics and other features of an attenuating element 32 of a radiation shield 30, the polymer 44 may comprise a flexible polymer. The polymer 44 may comprise a material that retains its flexibility when exposed to heat and/or ionizing radiation, and may retain its flexibility when exposed to heat and/or ionizing radiation repeatedly or for prolonged periods of time. In some embodiments, the particles 42 of attenuating material may be held together with the polymer 44. In embodiments where the attenuating element 32 includes a sufficient amount of the polymer 44, the particles 42 of attenuating material may be dispersed throughout the polymer 44. Also without limitation, the particles 42 of attenuating material of the layer 32 may comprise a non-toxic material that comprises or is based upon an element or elemental species or compound having an atomic number of 56 or greater. The attenuating element 32 may have a percent solids loading (by weight) that imparts it with a desired distribution, a desired particle 42 density and, thus, while also considering the thickness of the attenuating element 32, with the ability to attenuate nuclear radiation or other ionizing radiation by a desired amount, or extent. While virtually any percent solids loading that will impart the attenuating element 32 with desired properties may be used (e.g., at least 50%, by weight, at least 70%, by weight, etc.), in some embodiments, the percent solids loading of the attenuating element 32 may be eighty percent (80%), by weight, to about ninety percent (90%), by weight. In one example, with continued reference to FIG. 6 and renewed reference to FIG. 1, a radiation shield 30 may include an attenuating element 32a that comprises a layer formed by a polymer 44 throughout which particles 42 of a relatively high z material are dispersed and another attenuating element 32b that comprises a layer formed by a polymer 44 throughout which particles 42 of a relatively low z material are dispersed. The polymer 44 of the attenuating element 32a may comprise vinyl, while the particles 42 of the attenuating element 32a may be formed from barium sulfate, and the percent solids loading of particles 42 of the attenuating element 32a may be about eighty percent (80%), by weight, to about eighty-two percent (82%), by weight. The attenuating element 32b may also include a vinyl polymer 44, throughout which particles 42 of bismuth oxide are dispersed in a percent solids loading of about eighty-five percent (85%), by weight, to about eighty-seven percent (87%), by weight. Such attenuating elements 32a and 32b may have thicknesses (or average thicknesses) of about 0.6 mm. FIGS. 7 through 9 illustrate other embodiments of attenuating elements 32 that may be used in a radiation shield 30 according to this disclosure. In FIG. 7, an embodiment of attenuating element 32′ is depicted that includes a radio-opaque layer 140 sandwiched between a pair of containment layers 120 and 130. Each containment layer 120, 130 may comprise a thin, flexible film. The material of each containment layer 120, 130 may conform somewhat to the shape of an object, such as the body part of a patient, over which a radio-opaque film 10 that includes the containment layers 120 and 130 is positioned. In some embodiments, the containment layers 120 and 130 may be configured in such a way as to enable folding of the radio-opaque film of which they are a part. In some embodiments, one or both containment layers 120 and 130 may include at least one surface with features, such as patterned or random texturing, that increase its effective surface area and/or enhance adhesion between that containment layer 120, 130 and the adjacent radio-opaque layer 140. By way of example, and not by way of limitation, each containment layer 120 and 130 may have a thickness of about 15 mils (0.015 inch, or about 0.375 mm) or less. Of course, embodiments of radio-opaque films 10 that include containment layers 120, 130 of other thicknesses are also within the scope of the present invention. A variety of different materials are suitable for use as containment layers 120, 130, including, without limitation, polymers, papers, ceramic based materials and fabrics. The material used as each containment layer 120, 130 may be selected on the basis of a number of factors, including, without limitation, temperature resistance, abrasion resistance, ability to withstand contact with oils, the porosity of the material, water-resistance (which may be a function of porosity, the material itself, etc.), bacterial resistance (which may be a function of porosity, incorporation of antibacterial agents into the material, etc.), flexibility, feel and any other factors. In some embodiments, each containment layer 120, 130 may comprise a polymer or a polymer-based material. More specifically, one or both containment layers 120, 130 may comprise a polymer film or a sheet of woven or non woven polymer fibers with paper-like or fabric-like characteristics. In other embodiments, one or both containment layers 120, 130 may comprise a polymer, but have a structure (e.g., fibers arranged in a way) that resembles paper (e.g., for use as a surgical drape, etc.) or fabric (e.g., for use in a gown, etc.). In some embodiments, one or both of the containment layers may have some opacity to ionizing radiation, or radio-opacity. The radio-opaque layer 140 of the attenuating element 32′ may include an attenuating material that may, in some embodiments, be in a particulate or powdered form. In such embodiments, the radio-opaque layer 140 may include a binder that holds particles of the radio-opaque material together. Without limitation, the attenuating material of the radio-opaque layer 140 may comprise a non-toxic material that comprises or is based upon an element or elemental species or compound having an atomic number of 56 or greater. Non-limiting examples of such elements or elemental species include barium (Ba) species, bismuth (Bi) species and lanthanum (La) species. Specific examples of such inorganic salts include, but are not limited to, barium sulfate (BaSO4) and bismuth oxide (Bi2O3). In embodiments where the radio-opaque layer 140 includes a binder, any material that will hold particles of the radio-opaque material together without causing a substantial decrease in the density of the radio-opaque material may be used as the binder. The binder may hold particles of radio-opaque material together loosely, it may provide a stronger bond between adjacent particles, and/or it may enable the formation of a smooth uniform coating, or film. Examples of such materials include, but are not limited to, polyvinyl alcohol (PVA), polyvinyl butyrol (PVB), polyvinyl chloride (PVC), polyethylene glycol (PEG), silicones, polyurethanes and combinations of any of these materials. In a radio-opaque layer 140 with particles of radio-opaque material held together with a binder, the radio-opaque material may, in some embodiments, comprise at least about 50% of the weight of the radio-opaque layer 140, with the binder comprising about 50% or less of the weight of the radio-opaque layer 140. Other embodiments of radio-opaque layers 140 include about 75% or more of the radio-opaque material, by weight, and about 25% or less of the binder, by weight. In still other embodiments, the radio-opaque material may comprise about 97% or more of the weight of the radio-opaque layer 140, while the binder comprises only up to about 3% of the weight of the radio-opaque layer 140. In some embodiments, a radio-opaque layer 140 of an attenuating element 32′ has a thickness of about 40 mils (0.040 inch, or 1 mm) or less. In other embodiments, an attenuating element 32′ may include a radio-opaque layer 140 with a thickness of about 25 mils (0.020 inch, or about 0.6 mm) or less. In still other embodiments, the radio-opaque layer 140 of an attenuating element 32′ may have a thickness of about 15 mils (0.015 inch, or about 0.375 mm) or less, about 10 mils (0.010 inch, or about 0.25 mm) or less, or about 5 mils (0.005 inch, or about 0.125 mm) or less. The ability of the radio-opaque layer 140 to attenuate ionizing radiation depends upon a number of factors, including, without limitation, the attenuating ability of each radio-opaque material from which the radio-opaque layer 140 is formed, the relative amounts of radio-opaque material and binder in the radio-opaque layer 140, and the thickness of the radio-opaque layer 140. The containment layers 120 and 130 may be secured to the radio-opaque layer 40, and to one another, in a number of different ways. As an example, in embodiments where the radio-opaque layer 140 includes a particulate or powdered radio-opaque material and a binder, the binder may adhere or otherwise secure the containment layers 120 and 130 to the radio-opaque layer 140 and, thus, to one another. In other embodiments, the containment layers 120 and 130 may be directly or indirectly seemed to one another at a plurality of spaced apart locations (e.g., in a matrix of spaced apart points, a grid of spaced apart row lines and column lines, etc.) with the radio-opaque layer 140 occupying substantially all other areas (i.e., substantially all of the area) between the containment layers 120 and 130. For example, the containment layers 120 and 130 may be directly fused to one another (e.g., by thermal bonding, solvent bonding, etc.). As another example, adhesive material may be disposed between a plurality of spaced apart locations on the containment layers 120 and 130. Known processes may be used to manufacture an attenuating element 32′. In some embodiments, the radio-opaque material and binder may substantially homogeneously mixed in a solvent. The solvent may comprise a carrier solvent within which the binder is provided, or a separately added solvent. In more specific embodiments, the resulting slurry may have a solids content, or solids loading, of about 75% w/w to about 80% w/w. The slurry may then be applied to one of the containment layers 120 in a manner that will result in the formation of a thin film of radio-opaque material over the containment layer 120. In specific embodiments, a doctor blade or simulated doctor blade technique may be employed to form the radio-opaque layer 140. In other embodiments one or more rollers may be employed to form and disperse the radio-opaque layer 140 between the containment layers 120 and 130. The other containment layer 130 may then be applied over the radio-opaque layer 140. In a specific embodiment suitable for mass production, roll calendaring techniques may be used. Turning now to FIG. 8, another embodiment of attenuating element 32″ is shown. Like the attenuating element 32′ depicted by FIG. 7, attenuating element 32″ includes a pair of oppositely facing containment layers 120 and 130 with a radio-opaque layer 140′ between the containment layers 120 and 130. Radio-opaque layer 140′ differs from radio-opaque layer 140, however, in that radio-opaque layer 140′ includes two (as depicted) or more sublayers 142′, 144′, etc. Each sublayer 142′, 144′, etc., includes a different radio-opaque material or mixture of radio-opaque materials than each adjacent sublayer 144′, 142′, etc. In some embodiments, each sublayer (e.g., sublayer 142′) may be based upon an elemental species (e.g., barium, bismuth, lanthanum, etc.) with an atomic number that is less than the atomic number of the elemental species of the radio-opaque material upon which the next successive sublayer (e.g., sublayer 144′) is based. By way of non-limiting example, sublayer 142′ may comprise barium sulfate (barium, or Ba, has an atomic number of 56), while sublayer 144′ may comprise bismuth oxide (bismuth, or Bi, has an atomic number of 83). Of course, other arrangements of sublayers 142′, 144′, etc., are also within the scope of the present invention. The use of multiple sublayers 142′, 144′, etc., may provide a radio-opaque layer 140′ an increased attenuation over the use of a single layer of radio-opaque material of the same thickness as radio-opaque layer 140′. When superimposed sublayers 142′, 144′, etc., of different radio-opaque materials are used, selection of the radio-opaque material for each sublayer 142′, 144′ may be based upon the arrangements of their attenuating species (e.g., lattice structures, the distances their attenuating species are spaced apart from one another, etc.), as sublayers 142′ and 144′ with differently arranged attenuating species may attenuate ionizing radiation differently. The material or materials of each sublayer 142′, 144′ may be selected on the basis of their ability to attenuate ionizing radiation over different bandwidths (or ranges) of frequencies or wavelengths, which may impart the radio-opaque layer 140′ with the ability to attenuate a broader bandwidth of frequencies of ionizing radiation than the use of a single layer of radio-opaque material that has the same thickness as radio-opaque layer 140′. Suitable processes, such as those described in reference to the embodiment of radio-opaque film 32′ shown in FIG. 7, may be used to manufacture an attenuating element 32″ with two or more adjacent sublayers 142′, 144′, etc. Of course, the use of a plurality of sublayers 142′, 144′, etc., to form the radio-opaque film 140′ requires slight modification of the above-described process, as only the first sublayer 142′ is formed directly on the containment layer 120; each successively formed sublayer 144′, etc., is formed on a previously formed sublayer 142′, etc. Once all of the sublayers 142′, 144′, etc., are formed, the other containment layer 130 may then be positioned over and applied to the uppermost sublayer 144′, etc. FIG. 9 illustrates another embodiment of attenuating element 32″, in which adjacent sublayers 142′, 144′, etc., of the radio-opaque layer 140′ are physically separated from one another by way of an isolation layer 150. Isolation layer 150 may comprise a polymer, such as a low density polyethylene, or any other suitable material. Isolation layer 150 may itself have radio-opaque properties, or it may be substantially transparent to ionizing radiation. Attenuating element 32′″ may be manufactured by processes similar to those used to form attenuating element 32′, with each isolation layer 150 being positioned over and secured to a sublayer 142′, etc. (e.g., by roll calendaring, etc.), then forming each successive sublayer 144′, etc., on an isolation layer 150. After defining the uppermost (or outermost) sublayer 144′, etc., a containment layer 130 is positioned over and secured to that sublayer 144′, etc. Optionally, one or more attenuating elements 32 may include a polymer film that carries an attenuating material (e.g., in the form of particles, films, foils, etc.) on its surface. A study was performed to determine the extent to which a radiation shield with two different attenuation elements (layers) will attenuate ionizing radiation. In that study, the attenuation of different amounts of ionizing radiation by a variety of different attenuating elements was determined. Four different types of radiation shields were prepared and tested for comparative, or reference, purposes. These radiation shields included lead foil, a lead radiation shield, a lead-free radiation shield and a bismuth oxide radiation shield. The lead foil used in the study was 99.9% pure foil available from Alfa Aesar. The lead shield, which had a thickness of 1.5 mm, was a 0.5 mm lead-equivalent STARLITE radiation shield (Lot #10166) available from Bar Ray Products of Littlestown, Pa. The lead-free shield, which included particles of elemental antimony (Sb) embedded in an elastomeric material at a weight ratio of about 1:1 and had a thickness of 1.9 mm (equivalent to 0.5 mm thick lead foil), was a TRUE LITE radiation shield (Lot#10467) available from Bar Ray Products. The bismuth oxide radiation shield included a 0.75 mm thick layer of bismuth oxide captured between two sheets, each about 0.1 mm thick, of TYVEK® flashspun polyethylene fibers. Three sets of five irradiations were performed, with a first set including 60 kVp of x-ray irradiation, a second set including 90 kVp of x-ray irradiation and a third set including 120 kVp of x-ray irradiation. NANODOT® dosimeters, available from Landauer, Inc., of Glendale, Ill., were used to detect the amount of x-ray radiation that passed through each of the tested products. In each irradiation, five dosimeters were placed on a surface within an anticipated field of exposure having a diameter of about 250 mm. A sample of each of the four radiation shields (i.e., the lead film, the lead shield, the lead-free shield and the bismuth oxide shield) was placed over one of the dosimeters (a total of four dosimeters having been covered). Another dosimeter remained uncovered. A National Institute of Standards and Technology (NIST)- and ISO-calibrated x-ray source available at Landauer's laboratory was used to simultaneously expose the radiation shields and the exposed dosimeter to x-ray radiation. One of the predetermined x-ray energies was then generated, with the tested radiation shields, as well as the bare dosimeter, within the field of exposure. An ion chamber was used to measure the radiation dosage at the beginning of each of the tests (i.e., different energies). Ion chamber counts were obtained three times to verify reproducibility of the measurements. In each test (i.e., for each energy of x-ray radiation), exposure to the x-ray radiation lasted for 60 seconds. Following each irradiation, the dosimeters were removed and stored carefully to maintain traceability. Data was then obtained from the dosimeters to determine the measured incident dosages of x-ray radiation (the control provided by the bare dosimeters) and the transmitted dosages of x-ray radiation (the amounts of x-ray radiation attenuated by each product, as measured by the covered dosimeters). FIGS. 10-12 show the x-ray energy spectra at 60 kVp, 90 kVp and 120 kVp, respectively. In TABLE 1, data corresponding to the dosage of x-ray radiation, measured in mrad, to which each dosimeter (i.e., the bare dosimeter, the dosimeter under the 0.75 mm test product (“Drape”), the dosimeters under the three comparative products “Lead Foil,” “Lead Free,” “Lead Shield”) was exposed is set forth. Each value comprises an average of the five replicate tests at each energy (kVp) of x-ray radiation. TABLE 1StdDev ofEnergyEnergyRead AveStdDev ofAdjustedAdjustedKVpShieldingmradRead mradDose (mrem)Dose60Bare25372437Bismuth Oxide282271Lead Foil9181Lead Free171161Lead Shield11110190Bare5331053710Bismuth Oxide10041014Lead301301Lead Foil191191Lead Free571581120Bare85088248Bismuth Oxide20351975Lead Foil311301Lead Free12931253Lead Shield612592 From these data, the amount of attenuation by each radiation shield was calculated using attenuation by the 0.5 mm lead foil (“Lead Foil”) as a baseline. Specifically, the transmitted mrad values for the other radiation shields were divided by the transmitted mrad values for the 0.5 mm lead foil. The percent (%) attenuation was then calculated as the complement of the quotient. The 0.5 mm lead foil attenuates x-ray radiation better than the other radiation shields. In decreasing order of x-ray attenuation ability were the 1.5 mm lead shield (98%), the 1.9 mm lead-free shield (92%) and the much thinner 0.75 mm bismuth oxide radiation shield (about 85%). The same irradiation tests were performed using a radiation shield that included a 0.7 mm thick bi-layer made of two radio-opaque materials: a 0.35 mm thick bismuth oxide layer (80% w/w bismuth oxide, 20% w/w binder (see EXAMPLE 1); and a 0.35 mm thick bismuth-bismuth oxide layer (80% w/w bismuth-bismuth oxide, including 50% w/w bismuth and 50% w/w bismuth oxide, with the balance comprising a binder including PVB, PEG, PVC, silicone and polyurethane. Both radio-opaque films included two sheets (about 0.1 mm thick) of TYVEK® flashspun polyethylene fibers with a radio-opaque layer therebetween. The ability of that radiation shield, which is designed as “2L BB” in TABLE 2 below, to attenuate ionizing radiation at each of the 60 kVp, 90 kVp and 120 kVp x-ray energy spectra, is set forth in TABLE 2. TABLE 2StandardReadDeviation of EnergyAverageDeliveredAdjustedStd DeviationkVpShieldingmradmradDose (mrem)of mrem602L BB130.68120.73Bare25410.524410.08902L BB491.95501.97Bare54213.9154614.021202L BB1145.311115.15Bare83614.7381114.29 FIG. 13 illustrates the ability of the 0.7 mm radiation shield, which includes two attenuating elements (e.g., layers) to attenuate ionizing radiation relative to the 0.5 mm thick lead foil, the 1.5 mm thick lead-based radio-opaque layer, and the 1.9 mm thick lead-free radio-opaque layer. Based on the data illustrated in FIG. 13, the estimated weight of a frontal radiation shield (based on the 5,000 cm2 area of radio-opaque material used in some commercially available frontal radiation shields) made from a 0.7 mm radio-opaque film was calculated, and compared with the known weight of lead frontal radiation shield of the same size. In FIG. 14, the weight savings that would be provided by a frontal radiation shield made from a 0.7 mm thick radiation shield including two attenuating elements (e.g., layers) is depicted in terms of a percent weight savings, as is the amount of weight savings of a lead-free frontal radiation shield over a lead frontal radiation shield. FIG. 15 shows that a complete gown (about 10,000 cm2 total area) made from the 0.7 mm radio-opaque film would still weight significantly less (about 35% less) than the combined weights of a lead frontal radiation shield and sterile gown made from sheets of TYVEK® flashspun polyethylene fibers. In contrast, a gown fashioned from the 1.9 mm lead-free radio-opaque material would weight significantly more (about 20% more) than the combined weights of a lead frontal radiation shield and sterile gown. From the foregoing, it is apparent that a radiation shield that incorporates teachings of this disclosure may attenuate ionizing radiation to an extent comparable to the extents to which existing radiation shields attenuate ionizing radiation, but at a significantly reduced thickness and weight. A dose attenuation study was performed to determine the extent to which a radiation shield with two different attenuation elements (layers) will attenuate ionizing radiation in an operating nuclear power plant. The radiation shield used in the study included twenty-five (25) superimposed layers of barium sulfate particles dispersed in vinyl with a percent solids loading of about eighty percent (80%), by weight, to about eighty-two percent (82%), by weight. In addition, that radiation shield included one (1) layer of bismuth oxide particles dispersed in vinyl with a percent solids loading of about eighty-five percent (85%), by weight, to about eighty-seven percent (87%), by weight. The bismuth oxide layer was superimposed over the stack of twenty-five (25) barium sulfate layers, on a side of the stack intended to face away from a source of ionizing radiation. The performance of the barium sulfate-bismuth oxide radiation shield was compared with the abilities of a conventional lead wool shield and of a conventional shield made with tungsten particles to attenuation ionizing radiation. These radiation shields (in the form of shielding blankets) were approximately of the same size and weight as one another. In this study, two different types of radiation sources were used: (i) a low dose rate source of mixed radiation of a type that may be present in certain locations at a nuclear power plant; and (ii) a high dose rate source comprised essentially of a Cobalt-60 isotope. Two different types of dose detectors were also used: (i) a survey meter using a Geiger-Muller type detector was used to obtain data from a first series of tests using a low dose rate source; and (ii) a more accurate ion chamber detector was used to obtain data from a second series of tests using a low dose rate source and to obtain data from a third series of tests using a high dose rate source. Each radiation shield was tested by placing it on a source and measuring the amount of ionizing radiation that passed through the shield. The results are tabulated in TABLE 3. TABLE 3Geiger Muller detector(Survey Meter)Ion Chamber detectorlow doselow dosehigh doserate,Atten-rate, Atten-rate,Atten-mRem/uationmRem/uationmRem/uationHr%Hr%Hr%No shielding39—18—600—Lead wool1074%761%26057%blanketTungsten2146%1233%38037%blanketBaSO4/Bi2O31172%856%30050%layeredBlanketThe data clearly show that the dose reduction achieved by the layered low Z/high Z blanket greatly surpasses that of the tungsten shielding blanket and is, in fact, close to that of lead blankets. The data also show this holds true regardless of whether employed in a low or high dose rate environment, and whether measured by a survey meter or an ion chamber detector. Teachings of this disclosure are not only applicable to radiation shields 30 (FIG. 1) that include two or more attenuating elements 32 that include different attenuating materials from one another, that attenuate different energies or different energy ranges from one other or that have different characteristics from each other, they are also applicable to situations where two or more radiation shields having different characteristics are used together. Without limitation, such a radiation shielding system may include two or more separate layers that are used together to provide the benefits of the disclosed arrangements. Alternatively, a radiation shielding system may include the use of a radiation shield that comprises a tape, a film or the like in conjunction with a pliable or flowable radiation shield (e.g., a resin, putty, paint, etc.). A radiation shielding system may also include two or more layers of different pliable or flowable radiation shields that are used together and are superimposed over one another. Of course, other combinations of radiation shields that attenuate radiation in the disclosed manner are also within the scope of this disclosure. Although the foregoing description includes many specifics, these should not be construed as limiting the scope of any of the appended claims, but merely as providing information pertinent to some specific embodiments that may fall within the scopes of the appended claims. Other embodiments may also be devised which lie within the scopes of the appended claims. Features from different embodiments may be employed in combination. The scope of each claim is, therefore, indicated and limited only the language of that claim and its legal equivalents. All additions, deletions and modifications to the disclosed embodiments that fall within the meanings and scopes of the appended claims are to be embraced thereby.
048067695	summary	BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion implantation system used for manufacturing semiconductor devices. More particularly, it relates to a cooling of an ion target mechanism in the ion implantation system using a high ion dosage. 2. Description of the Related Art There is an urgent need for a high-speed throughput in an ion implantation (injection) process. The throughput speed is generally defined by the following times: an ion implantation time T.sub.I , a handling time T.sub.H for exchanging a target disk having semiconductor wafers thereon and mounted on a mechanism, and a time T.sub.P for pumping a vacuum chamber. An improvement of the throughput speed can be achieved by shortening these times. The ion implantation time T.sub.I can be reduced by increasing an ion beam current from approximately 10 mA to 30 mA, which will provide a high ion dosage, approximately 10.sup.15 cm.sup.-2 to 10.sup.16 cm.sup.-2. On the other hand, the reduction of the handling time T.sub.H and the pumping time T.sub.P can be realized by applying a method in which dual end stations are used; a method in which a system has two end stations and the wafer handling and the vacuum pumping for one end station are carried out during the ion implantation of the other end station. Another method for reducing the pumping time T.sub.P is a direct-exchange of the semiconductor wafers. The dual end station method, however, requires the use of a bulky facility, and the direct wafer exchange method in the vacuum chamber involves a difficult operation, and the quality of a semiconductor wafer may be reduced because dust may be generated from movable portion of the target disk in the vacuum chamber. Therefore, a target disk exchange method has been proposed ("A high-throughput mechanically scanned target chamber", G. Ryding and A. Armstrong, on pp. 319 to 325, "Nuclear Instruments and Methods", No. 189, by North Holland Publishing Company, 1981). The prior art ion implantation system using the disk exchangeable target mechanism has a low implantation reliability due to heat generated during subjecting the semiconductor wafers on the disk to high ion dosages. This will be described in more detail with reference to a specific example. SUMMARY OF THE INVENTION An object of the present invention is to provide an ion implantation system using a disk exchangeable target mechanism which can be effectively cooled even when semiconductor wafers on the disk are being subjected to a high ion dosage. Another object of the present invention is to improve the throughput speed of ion implantation by using the above ion implantation system. Still another object of the present invention is to improve the reliability of ion implantation when using a high ion dosage. According to the present invention, there is provided a disk exchangeable target mechanism of an ion implantation system including an exposure chamber for inserting the disk exchangeable target mechanism and introducing accelerated ion beams directed to a semiconductor wafer on the disk exchangeable target mechanism, having: a metal target disk on which a semiconductor wafer(s) to be ion-implanted can be mounted on a first face thereof, a support including a metal base having the target disk mounted thereon, and a shaft incorporated with the base. The support is rotatable in the exposure chamber by a force applied to the shaft during a ion-implantation process, and the target disk is detachable from the support when to be taken out of the exposure chamber. The target mechanism further includes a medium, provided between a second face of the target disk opposing the first face and the base, for providing a thermal contact therebetween. The thermal contact medium may have a high contactability with metal, and the thermal contact medium may also have a high thermal conductivity. The thermal contact medium further may be stable in a vacuum. The base of the support may be provided with a cavity, and the shaft may be provided with holes communicated with the cavity. A cooling medium is inserted into the cavity through a hole and the inserted cooling medium is drained from the cavity through another hole. The target disk may be provided with a thermal transportation unit transporting thermal energy at a portion(s) where the temperature is high by applying ion implantation energy to another portion(s) where the temperature is low. The thermal transportation unit may include a heat pipe(s), and the heat pipe(s) may include a cooling medium having a low boiling temperature. The heat pipes may be radially provided with respect to a rotation center of the target disk. Note, any combinations of the above may be used.
052296164	description	Description of the Preferred Embodiments Referring to FIGS. 1 and 2, an exposure light source 10 according to a first embodiment of this invention is included in an illuminator 11 which comprises a reflection mirror 13 at the rear of the exposure light source 10 with a spacing left between the reflection mirror 13 and the exposure light source 10. The reflection mirror 13 may have a half elliptic configuration (as shown in FIG. 2), a half spherical configuration, a half circular configuration, or the like in cross section and it partially surrounds the exposure light source 10, as illustrated in FIG. 2. At any rate, the reflection mirror 13 is operable to converge the light beam emitted from the exposure light source 10 onto a semiconductor wafer (not shown in this figure). In FIG. 1, the illustrated exposure light source 10 comprises an exposure lamp 15 which further comprises a lamp tube, first and second connectors 16 and 17, and first and second electrodes 18 and 19. The lamp tube has first and second open end portions and an intermediate portion of a meandering configuration between the first and the second end portions. The intermediate portion of the lamp tube is composed of straight portions and curved portions, as illustrated in FIG. 1. The lamp tube is formed of quartz and may therefore be called a quartz discharge tube. The first and the second connectors 16 and 17 are hermetically or airtightly fitted to the first and the second end portions. The first and the second electrodes 18 and 19 are inserted into an internal space of the lamp tube through the first and the second connectors 16 and 17, respectively. Although not shown in FIG. 1, a vaporizable metal is enclosed within the internal space of the lamp tube, as will be described later in detail. The electrical discharge between the first and the second electrodes 18 and 19 serve to heat and vaporize the vaporizable metal in the internal space of the lamp tube. In order to enclose the vaporizable metal within the internal space, the lamp tube is first evacuated by a vacuum pump (not shown) and the vaporizable metal is thereafter introduced within the internal space of the lamp tube together with inert gas, such as an argon neon, or the like. In this event, the amount of the vaporizable metal is selected so that a partial pressure of the vaporizable metal is lower than 1 atmosphere when the vaporizable metal is vaporized within the internal space of the lamp tube. Specifically, the partial pressure of the vaporizable metal may be as low as several Torrs. In this connection, the exposure lamp 15 may be referred to as a low pressure lamp. Subsequently, the first and the second connectors 16 and 17 are airtightly fitted to the first and the second end portions of the lamp tube. Moreover, the illustrated illuminator 11 further comprises a pair of source terminals 21 and 22 connected to the first and the second connectors 16 and 17 and to a power source 23. With this structure, it is possible to emit light rays from the exposure light source 10 when an electric voltage is impressed between the source terminals 21 and 22 with the source terminals 21 and 22 electrically connected to the first and the second connectors 16 and 17 in a manner to be described later in detail. It is mentioned here that each element is given an atomic number and the mass number equal to a sum of the numbers of protons and neutrons. When a plurality of isotopes having different mass numbers, are used a spread of an emission spectrum depends on the number of the isotopes of the element because such isotopes which have different mass numbers cause an isotope shift to occur. In other words, such an isotope shift results from subtle displacements of emission spectra of isotopes having different mass numbers and spreads a bandwidth of each emission spectrum. Now, the vaporizable metal may be, for example, mercury, and substantially consists of a single isotope of the mercury. Herein, it is known that mercury has, in nature, seven stable isotopes which are specified by .sub.80 Hg.sup.196, .sub.80 Hg.sup.198, .sub.80 Hg.sup.199, .sub.80 Hg.sup.200, .sub.80 Hg.sup.201, .sub.80 Hg.sup.202, and .sub.80 Hg.sup.204. In the example being illustrated, one of the seven isotopes is selected and enclosed in the lamp tube. Herein, Table 1 shows a nuclear spin and an abundance ratio of each isotope. The nuclear spin may be replaced by a nuclear magnetic moment. TABLE 1 ______________________________________ isotopes nuclear spin abundance ratio (%) ______________________________________ .sub.80 Hg.sup.196 0 0.15 .sub.80 Hg.sup.198 0 10.0 .sub.80 Hg.sup.199 not 0 16.8 .sub.80 Hg.sup.200 0 23.1 .sub.80 Hg.sup.201 not 0 13.2 .sub.80 Hg.sup.202 0 29.8 .sub.80 Hg.sup.204 0 6.9 ______________________________________ In general, isotopes are readily obtained with an increase of the abundance ratio. Taking this into consideration, a selected one of the isotopes may be selected from a specific isotope group of .sub.80 Hg.sup.199, .sub.80 Hg.sup.200, and .sub.80 Hg.sup.202 as the single isotope of the mercury. The selected isotope of the mercury is excited and vaporized into metal vapor in the lamp tube by supplying an electric voltage of, for example, an a.c. voltage of 10 kilovolts from the power source 25 across the first and the second connectors 16 and 17. If .sub.80 Hg.sup.199 is selected as the selected isotope, light rays are emitted from the exposure lamp 15 having a pair of emission spectra which are subtly split from each other with a wavelength distance of 0.005 nm therebetween and which fall within a wavelength band of 253.7 nm. At any rate, the light rays are ultraviolet in the far region. Herein, such split emission spectra appear on the basis of the nuclear spin, as will become clear as the description proceeds, and may be called a hyper fine line structure. In other words, use of .sub.80 Hg.sup.199 brings about the hyper fine line structure. From this fact, it is apparent that the emission spectra are determined in dependence upon the single isotope of the mercury. With this structure, it is possible to prevent the emission spectra from being spread over a bandwidth of 0.005 nm. This is because only the single isotope of the mercury is enclosed within the lamp tube and can avoid a nuclear shift which occurs from coexistence of a plurality of isotopes of the mercury. Therefore, the light rays exhibits a very narrow emission spectrum when the single isotope is enclosed within the lamp tube even when .sub.80 Hg.sup.199 is used as the single isotope, although the emission spectrum shows the hyper fine line structure. This exposure lamp can be used as an exposure lamp source for manufacturing 16 MDRAM, although the exposure lamp can not be suitable for an exposure lamp source of 64 MDRAM. Alternatively, assume either .sub.80 Hg.sup.200 or .sub.80 Hg.sup.202 is selected as the single or selected isotope. As tabulated in Table 1, the selected isotope, such as .sub.80 Hg.sup.200 or .sub.80 Hg.sup.202, has a nuclear spin equal to 0. When either .sub.80 Hg.sup.200 or .sub.80 Hg.sup.202 is enclosed in the lamp tube, it is also possible to avoid occurrence of the hyper fine line structure which appears when a single isotope has a nuclear spin which is not equal to 0, as mentioned before. Practically, .sub.80 Hg.sup.200 is selected as the single or selected isotope and enclosed in the lamp tube in consideration of the abundance ratio of .sub.80 Hg.sup.200. When the lamp tube has a length equal to 1 meter, several tens of milligrams of .sub.80 Hg.sup.200 are enclosed in the lamp tube. In this case, the selected isotope .sub.80 Hg.sup.200 can emit an optical beam when vaporized and excited. The optical beam has a single emission spectrum which has a wavelength of 253.7 nm and a spectrum bandwidth narrower than 0.002 nm. This shows that the optical beam has a wavelength of a far ultraviolet band and the spectrum bandwidth is very narrow without a spread of the spectrum based on the isotope shift and without the hyper fine line structure. An isotope, such as .sub.80 Hg.sup.200, is produced and sold by Nippon Sanso Corporation (Tokyo, Japan) and can be readily obtained for use in the exposure lamp 15. Referring to FIG. 3, an exposure apparatus comprises the illuminator 11 which is illustrated in FIGS. 1 and 2 and which is symbolized by the reflection mirror 13 and the exposure light source 10. The illuminator 11 emits, from the exposure light source 10, the far ultraviolet light which has the narrow bandwidth, as mentioned in conjunction with FIG. 1. The far ultraviolet light is reflected by a mirror 25 and thereafter sent through an optical integrator 26 to an additional mirror 27 as reflected far ultraviolet light. The reflected far ultraviolet light is projected through a condenser lens 28 onto a photomask 29 on which an enlarged circuit pattern is delineated. An image of the enlarged circuit pattern is passed to a reduction projection lens 30 to be sent to a semiconductor wafer 31 as a reduced image pattern. The semiconductor wafer 31 may be a wafer of silicon, GaAs, or the like. Thus, the enlarged circuit pattern on the photomask 30 is transcribed onto the semiconductor wafer 30 in the form of a reduced circuit pattern. The optical integrator 26, the condenser lens 28, and the lens 30 may be composed of quartz. Thus, only the single isotope of the mercury is enclosed within the exposure lamp 15. This enables prevention of occurrence of the isotope shift and produces a narrow spectrum bandwidth. Furthermore, when a isotope which has the nuclear spin equal to zero is enveloped within the lamp tube, it is possible to avoid occurrence of the hyper fine line structure. This makes it possible to make the spectrum bandwidth narrower. Therefore, when such an exposure light source is applied to an exposure apparatus for manufacturing a semiconductor device, it is possible to manufacture a very large scale integrated memory, such as a 64 MDRAM, without using any supplementary equipment, which differs from conventional exposure apparatus comprising the excimer laser. This means that the exposure light source according to this invention can accomplish the line and space which is necessary for the 64 MDRAM and is inexpensive in comparison with the conventional exposure apparatus. In the above-mentioned embodiment, mercury alone is used as the vaporizable metal. However, such a vaporizable metal is not restricted to mercury but may be, for example, lead, cadmium, or zinc. An element, such as lead, cadmium, or zinc, also enables emission of a far ultraviolet region like mercury. When the above-enumerated elements are used as the selected metal, the exposure lamp 15 is formed as a hollow cathode lamp which has a cathode and anode instead of the first and the second electrodes 18 and 19 illustrated in FIG. 1. In addition, the cathode may be composed of the selected metal. Tables 2, 3, and 4 show isotopes, nuclear spins, abundance ratios of lead (Pb), zinc (Zn), and cadmium (Cd), respectively. As known in the art, lead (Pb), zinc (Zn), and cadmium (Cd) have four, five, and eight isotopes, as tabulated in Tables 2, 3, and 4, respectively. TABLE 2 ______________________________________ isotopes nuclear spin abundance ratio (%) ______________________________________ .sub.82 Pb.sup.204 0 1.4 .sub.82 Pb.sup.206 0 24.1 .sub.82 Pb.sup.207 not 0 22.1 .sub.82 Pb.sup.208 0 52.4 ______________________________________ TABLE 3 ______________________________________ isotopes nuclear spin abundance ratio (%) ______________________________________ .sub.30 Zn.sup.64 0 48.6 .sub.30 Zn.sup.66 0 27.9 .sub.30 Zn.sup.67 not 0 4.1 .sub.30 Zn.sup.68 0 18.8 .sub.30 Zn.sup.70 0 0.6 ______________________________________ TABLE 4 ______________________________________ isotopes nuclear spin abundance ratio (%) ______________________________________ .sub.48 Cd.sup.106 0 1.25 .sub.48 Cd.sup.108 0 0.89 .sub.48 Cd.sup.110 0 12.49 .sub.48 Cd.sup.111 not 0 12.80 .sub.48 Cd.sup.112 0 24.13 .sub.48 Cd.sup.113 not 0 12.22 .sub.48 Cd.sup.114 0 28.73 .sub.48 Cd.sup.116 0 7.49 ______________________________________ Practically, the metal may be selected from the enumerated isotopes of Pb, Zn, and Cd in consideration of the abundance ratio of the isotopes, as mentioned in conjunction with mercury. In the illustrated example, the exposure apparatus is used for transcribing the circuit pattern onto the semiconductor wafer. The semiconductor wafer may be replaced either by a photomask blank having a shading layer of chromium or the like coated on a glass substrate or by a photoluminescent panel having a transparent film of indium-tin-oxide or the like coated on a glass substrate. At any rate, a single isotope of a specific metal element is enveloped within a lamp tube and vaporized into metal vapor to emit far ultraviolet light. Thus, it is possible to remove an isotope shift by enveloping the single isotope and to thereby reduce a spectrum bandwidth. Such a reduction of the spectrum bandwidth is helpful in the manufacture of a very large scale integrated memory, such as 4 MDRAM, 16 MDRAM, or the like, although a hyper fine line structure may appear in a spectrum in dependence upon a nuclear spin of the selected isotope. In addition, when selection is made of an isotope which has a nuclear spin equal to zero, the hyper fine line structure can also be removed together with the isotope shift. Therefore, selection of such an isotope is effective for making the spectrum bandwidth narrow. From this fact, it is readily understood that the desired line and space necessary for a very large scale integrated memory can be accomplished by merely selecting the isotope to be enclosed within the exposure lamp. This dispenses with any supplementary equipment and makes the exposure apparatus inexpensive. While this invention has thus far been described in conjunction with several embodiments thereof, it will readily be possible for those skilled in the art to put this invention into practice in various other ways. For example, the exposure lamp may have a wide variety of configurations in lieu of the meandering configuration, as illustrated in FIG. 1. In addition, the exposure lamp may be a microwave excitation lamp. Various kinds of isotopes may be used to emit far ultraviolet light.
056235291	claims	1. An SOR exposure system, comprising: a synchrotron radiation source; and a plurality of X-ray exposure apparatuses, connected to said synchrotron radiation source by a plurality of beam lines, for manufacturing semiconductor devices, wherein one of said plurality of exposure apparatuses comprises a duplicating exposure apparatus for duplicating an original mask to form a duplicated mask by exposing the original mask and a substrate disposed proximate to each other with the synchrotron radiation to transfer a pattern of the original mask to the substrate to form the duplicated mask, and wherein a divergence angle of illumination radiation introduced into said duplicating exposure apparatus for duplicating the original mask is less than that introduced into the other exposure apparatuses. X-ray intensity adjusting means, provided on the beam line to which said duplicating exposure apparatus is connected, for adjusting the intensity of the synchrotron radiation supplied to said duplicating exposure apparatus. an illumination optical system including an X-ray mirror having a reflecting surface provided on each of said beam lines, the reflecting surface of said X-ray mirror provided on the beam line to which said duplicating exposure apparatus is connected having a greater surface roughness than that of other beam lines of said plurality of beam lines. an illumination optical system including an X-ray mirror provided on each of said beam lines, the illumination optical system on the beam line to which said duplicating exposure apparatus is connected exhibiting a large angle of incidence of a beam of the synchrotron radiation on the X-ray mirror as compared with the angle of incidence of beams of synchrotron radiation on the X-ray mirrors of other beam lines of said plurality of beam lines. a synchrotron radiation source; and a plurality of X-ray exposure apparatuses, connected to said synchrotron radiation source by a plurality of beam lines, for manufacturing semiconductor devices, wherein one of said plurality of exposure apparatuses comprises a duplicating exposure apparatus for duplicating an original mask to form a duplicated mask by exposing the original mask and a substrate disposed proximate to each other with the synchrotron radiation to transfer a pattern of the original mask to the substrate to form the duplicated mask, and wherein an intensity of illumination radiation introduced into said duplicating exposure apparatus for duplicating the original mask is less than that introduced into the other exposure apparatuses. X-ray intensity adjusting means, provided on the beam line to which said duplicating exposure apparatus is connected, for adjusting the intensity of the synchrotron radiation supplied to said duplicating exposure apparatus. an illumination optical system including an X-ray mirror having a reflecting surface provided on each of said beam lines, the reflecting surface of said X-ray mirror provided on the beam line to which said duplicating exposure apparatus is connected having a greater surface roughness than that of other beam lines of said plurality of beam lines. an illumination optical system including an X-ray mirror provided on each of said beam lines, the illumination optical system on the beam line to which said duplicating exposure apparatus is connected exhibiting a large angle of incidence of a beam of the synchrotron radiation on the X-ray mirror as compared with the angle of incidence of beams of synchrotron radiation on the X-ray mirrors of other beam lines of said plurality of beam lines. 2. An SOR exposure system according to claim 1, wherein the beam line to which the duplicating exposure apparatus is connected to said synchrotron radiation source is longer than other beam lines of said plurality of beam lines. 3. An SOR exposure system according to claim 1, further comprising: 4. An SOR exposure system according to claim 1, wherein a wavelength of the synchrotron radiation supplied to said duplicating exposure apparatus is longer than a wavelength of the synchrotron radiation supplied to other exposure apparatuses of said plurality of exposure apparatuses. 5. An SOR exposure system according to claim 1, further comprising: 6. An SOR exposure system according to claim 1, further comprising: 7. An SOR exposure apparatus according to claim 1, wherein said duplicating exposure apparatus includes a proximity gap between an original mask and a substrate to be exposed which is smaller than that in other exposure apparatuses of said plurality of exposure apparatuses. 8. An SOR exposure system comprising: 9. An SOR exposure system according to claim 8, wherein the beam line to which the duplicating exposure apparatus is connected to said synchrotron radiation source is longer than other beam lines of said plurality of beam lines. 10. An SOR exposure system according to claim 8, further comprising: 11. An SOR exposure system according to claim 8, wherein a wavelength of the synchrotron radiation supplied to said duplicating exposure apparatus is longer than a wavelength of the synchrotron radiation supplied to other exposure apparatuses of said plurality of exposure apparatuses. 12. An SOR exposure system according to claim 8, further comprising: 13. An SOR exposure system according to claim 8, further comprising: 14. An SOR exposure apparatus according to claim 8, wherein said duplicating exposure apparatus includes a proximity gap between an original mask and a substrate to be exposed which is smaller than that in other exposure apparatuses of said plurality of exposure apparatuses.
047088427	description	DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1 of the drawings, there is depicted threin a portion of the core and the reactor lower internals. A fuel assembly generally designated by the numeral 10 includes a plurality of fuel rods 11, an upper outlet flow nozzle 12, and a lower inlet flow nozzle 13. Fuel rods 11 are parallel arranged and may be held in spaced relationship to each other by Inconel grids (not shown) as is well known in the art. A plurality of moderator control tubes 14 are interspersed among fuel rods 11. The Inconel grids (not shown) also support and are attached to the moderator control tubes 14. Upper outlet flow nozzle 12 is fixedly attached to the upper end 15 of the moderator control tubes 14 as by welding. A manifold 16, within upper outlet nozzle 12, flow connects the upper ends 15 of moderator control tubes 14. Similarly, the lower inlet flow nozzle 13 is seal welded to the lower end 17 of the moderator flow tubes 14. A lower manifold 18 flow connects the lower end 17 of all but one of the moderator flow tubes 14. Fuel assembly 10, as described, is of a type used with a light water, pressurized nuclear reactor which utilizes the spectral shift concept by varying the amount of deuterium oxide or heavy water within the fuel assembly, thereby varying the amount of light water moderator within the core. The deuterium oxide enters the fuel assembly via the channels 19 in the lower core support plate 20, through inlet seal connector 21, to lower nozzle manifold 18. The deuterium oxide is then distributed to the moderator control tubes 14 which, upon rising to the upper nozzle manifold 16, displaces the light water therein. The deuterium oxide then flows down the return flow moderator tube 22 to outlet seal connector 23 to the outlet channel 24 in the lower core support plate 20. A more complete description of fuel assembly 10, lower core support plate 20 and the flow path of the deuterium oxide may be found in copending U.S. patent application Ser. No. 626,847, filed Feb. 7, 1984, by R. K. Gjertsen, et al., entitled "Fuel Assembly" and assigned to Westinghouse Electric Corporation. It is to be noted, however, that once the desired amount of deuterium oxide is achieved within the moderator control tubes 14 and 22, the flow of deuterium oxide is reduced to the extent necessary to provide for any makeup heavy water required as a result of internal leakage and more importantly to provide a controlled continuous flow to remove radiation energy and to maintain the temperature of the heavy water below the boiling point. Hence, each seal connector 21 and 23 experiences the substantially same internal pressure. Moreover, since each seal connector 21 and 23 are located at the same axial core station, they each experience the same external pressure. Therefore, the inlet seal connector 21 is exposed to virtually the same environment as the outlet seal connector 23, and, by adjusting the internal pressure of the deuterium oxide to that of the coolant moderator at the inlet to the fuel assembly 10, there is substantially no pressure differential between the internal portion and the external portion of the seal connectors 21 and 23. Because of the substantially similar operating environment of the seal connectors 21 and 23, each seal connector may be made precisely the same and can be interchangeable. Details of seal connector 21 or 23 are shown in FIG. 2. Notwithstanding the near zero pressure differential internal and external of the seal connector, they are made to be leak free in the unlikely event of the existence of a negative or a positive pressure differential. A positive pressure differential coupled with a leaking seal connector could result in an inadvertent increase in moderation by an unplanned reintroduction of moderator within the fuel assembly 10. Obviously, such a condition is undesirable. On the other hand, a negative pressure differential coupled with a leaking seal connector could result in an unplanned decrease in moderator which is also undesirable. Seal connector 21 or 23 in general comprises a static upper portion 30 which is connected to the inlet end of fuel assembly 10, a movable lower portion 31 which is inserted within an insert 32, the lower core support plate 20, a bellows 33 connecting the upper 30 and lower 31 portions and a skirt 34 connected to upper portion 30 and which encircles bellows 33. Flow channels 35 and 36 are provided within upper portion 30 and lower portion 31, respectively, for purposes of introducing deuterium oxide or any other fluid (liquid or gas) which is less effective in slowing down neutrons than light water into the fuel assembly 10 or reintroducing the light water reactor coolant into said fuel assembly 10. Since the bottom or the moderator inlet end of fuel assembly 10 is inaccessible during the initial placement of fuel assemblies within the core, during fuel shuffling operations or during core refueling, a fixed or permanent mechanical connection between fuel assembly 10 and the lower core support plate 20 is not practical. Hence, seal connector 21 or 23 may be integral with or permanently affixed only at one end ot either the lower nozzle 13 or the core support plate 20. In the embodiment illustrated in FIG. 2, the static upper portion 30 of seal connector 21 or 23 is integral with flow nozzle 13 while the movable lower portion 31 comprises a slip fit which is spring loaded within and against core support plate 20 by a combination of fuel assembly hold down spring forces, the weight of the fuel assembly and a bellows spring force to be described hereinafter. The sealed fit between lower portion 31 and core support plate 20 is effectuated upon placement of fuel assembly 10 within the reactor core and is disconnected upon removal of fuel assembly 10. It is to be noted that an integral connection at the lower core support plate 20 with a slip fit at the flow nozzle 13 would be equally satisfactory and such alternative is intended to be included within the scope of the invention described herein. Still referring to FIG. 2, upper static portion 30 may be connected by a rolled bulge joint 37 within a boss or cylindrical extension 38 which is an integral part of lower nozzle 13. A plurality of rolled bulge joints 37 are provided so that a substantially leak free joint obtains between upper portion 30 and boss 38. In this type of joint, the thin cylindrical portion 39 of static portion 30 is rolled into grooves 40 in the internal surface of boss 38. Another equally satifactory and adequate mechanical connection may comprise a "Swage-lok" or other similar type of tube to housing connection. Still another type of seal joint may comprise threading upper portion 30 into boss 38 and seal welding around the periphery thereof provided the materials used are capable of being welded. One method to effectuate the seal between the movable portion 31 of seal connector 21 or 23 and the lower core support plate 20 comprises a ball and cone seal 50 in combination with a plurality of "piston ring" seals 51. In this regard, insert 32 is inserted within an opening 53 in core support plate 20 and is welded 54 thereto. Weld 54 serves as a mechanical and a sealing joint, with the latter being necessitated because of the need for opening 53 to be flow connected to either flow channel 19 or 24 in core support plate 20, which in turn provides flow communication between the flow channels 35 and 36 in seal connector 21 or 23. Ball and cone seal 50 employs principles which are well known in the art. A truncated conical surface 56 is provided at the upper end of insert 32. Surface 56 may be directly machined in insert 32 or may comprise a conical insert 57 made of a material substantially harder than the material from which lower portion 31 of seal connector 21 or 23 is made which is welded to lower portions 31 and then machined to final dimensions. While being slightly more complicated, the conical insert 57 is preferable in that it negates the probability of damage to the insert 32 integral with the lower core support plate 20. Movable portion 31 of the seal connector 21 or 23 includes a machined truncated spherical surface 58 which sealingly mates with conical surface 56. A plunger 59 extends from movable portion 31 and has a plurality of piston ring seals 51 fitted to grooves 60 machined in the periphery thereof. Ring seals 51 are of any design which is well known in the art and serve as a backup seal to limit any leakage into or out from the moderator control tubes 14 in the event that the main ball and cone seal 50 is damaged or otherwise fails to operate properly. A bellows 33 sealingly connects lower portion 31 to upper portion 30 of seal connector 21 or 23. Bellows 33 is made of metal and is welded at 52 and 55 to a cylindrical extension 61 from upper portion 30 and a cylindrical extension 62 from lower portion 31. Clearance space 63 is provided between upper 30 and lower 31 portions of the seal connector. Clearance space 63 allows for relative axial motion between the upper 30 and lower portions 31 which motion allows for a compressive load to be applied to fuel assembly 10 when installed in the reactor core and assures positive sealing of spherical surface 58 within conical surface 56. As illustrated, bellows 33 comprises a spring which transmits its compressive force, the compressive spring force applied to fuel assembly 10 and the weight of the fuel assembly to the lower portion 31 of seal connector 21 or 23. Metallic bellows 33 and clearance space 63 also allows for proper sealing notwithstanding any slight misalignment perpendicular to the axial centerline of the seal connector 21 or 23. Skirt 34 provides protection for bellows 33 and serves as an additional stop to limit the compressive travel of the movable lower portion 31 relative to the upper portion 30. Skirt 34 comprises a cylindrical tube 64 welded at 65 to an enlarged cylindrical portion 66 of the static upper portion 30. Skirt 34 extends down from said weld 65 covering the bellows 33 and terminates at end 67 which is spaced from insert 32 by a predetermined amount 68. Corresponding overlapping flanges or tabs 69 and 70 on movable portion 31 and skirt 34, respectively, limit the extension of space 63 when seal connector 21 or 23 is not fitted between nozzle 13 and core support plate 20. As described, seal connector 21 or 23 comprises a mechanically connected extension of a fuel assembly 10. Insert 32 is fixedly connected to core support plate 20. In the event seal connector 21 or 23 is damaged, it may be removed from fuel assembly 10 and replaced with a new seal connector. During such replacement, fuel assembly 10 is of course not assembled within a reactor core. When assembling a fuel assembly 10 equipped with seal connectors 21 and 23, normal procedures and precautions are utilized. Guide pins (not shown) as are commonly known in the art are used to guide the installation of fuel assembly 10 in its attachment to the core support plate 20. In this manner, the fuel assembly is properly aligned prior to any fit up between the seal connectors 21 and 23 and insert 32 so as to assure that the seal connectors 21 and 23 are not damaged during the installation procedure. Plunger 59 is further provided with a tapered entrance end 71 in the unlikely event of any misalignment of the fuel assembly 10 relative to core support plate 20. Taper 71 even further provides for minor misalignment, if any, of plunger 59 relative to opening 72 within insert 52. The transverse motion permitted by bellows 33, as previously described, then assures full sealing along the length of plunger 59. Contact between spherical surface 58 and conical surface 56 is effectuated after plunger 59 is substantially fully fitted within opening 72. Since bellows 33 exerts an extending force between upper 30 and lower 31 portions of the seal connectors 21 and 23, where contact is first made between the spherical 58 and conical 56 sealing surfaces, space 63 is greater than that shown in FIG. 2 by an amount approximately equal to the space 73 between flanges or tabs 69 and 70. The spring force on the exit end of fuel assembly 10 (not shown) as is commonly used in pressurized water nuclear reactors plus the weight of fuel assembly 10 serves to compress bellows 33 which then loads the spherical 58 and conical 56 surfaces. Upon completion of installation and the initiation of reactor operation, flow channels inthe core support plate 20 are in flow communication with the aligned flow channels 35 and 36 in seal connectors 21 and 23 which permit flow into and out of the moderator control tubes 14 and 15. Another embodiment of a seal connector 80 is shown in FIG. 3. In general, this embodiment differs from that of FIG. 2 by the provision of one or more ring seals 81 between the static portion 82 and the movable portion 83 of the seal connector 80. Ring seals 81 provide a backup seal in the unlikely event of failure of bellows 84. Ring seals 81 are fitted to grooves within end 85 of static portion 82; end 85 fits within an extension 86 of movable portion 83 which has an opening 87 therein and overlaps end 85. Further illustrated in FIG. 3 is an alternate method of attaching the static portion 82 to the lower nozzle 13. A flow connector 88 is inserted within an opening 89 in the lower nozzle 13. Opening 89 is in flow communication with either the lower nozzle manifold 18 and moderator control tube 22 (FIG. 1) depending upon whether seal connector 80 comprises an inlet connector or an outlet connector, rspectively. Flow connector 88 is welded 90 to lower nozzle 13. An extension 91 of the flow connector 88 fits within the upper end 92 of the static portion 83 of seal connector 80. As shown, static portion 83 is integrally seal connected to flow connector 88 by a plurality of rolled joints 93. As previously discussed, such connection may also comprise a "Swage-lok" type of connection. While the invention has been described, disclosed, illustrated and shown in certain terms or certain embodiments or modifications which it has assumed in practice, the scope of the invention is not intended to be nor should it be deemed to be limited thereby and such other modifications or embodiments as may be suggested by the teachings herein are particularly reserved especially as they fall within the breadth and scope of the claims here appended.
	abstract	A tokamak plasma vessel. The tokamak plasma vessel comprises a toroidal plasma chamber, a plurality of poloidal field coils, an upper divertor assembly, and a lower divertor assembly. The plurality of poloidal field coils are configured to provide a poloidal magnetic field having a substantially symmetric plasma core and an upper and lower null, such that ions in a scrape off lay outside the plasma core are directed by the magnetic field past one of the upper and lower nulls to divertor surfaces of the respective upper and lower divertor assembly. Each of the upper and lower divertor assembly comprises a liquid metal inlet and a liquid metal outlet located below the liquid metal inlet. Each of the upper and lower divertor assembly is configured such that in use liquid metal flows from the liquid metal inlet to the liquid metal outlet over at least one divertor surface of the divertor assembly.
	description	This invention was made with Government support under Contract No. DE-NE0000633 awarded by the Department of Energy. The Government has certain rights in this invention. This application claims priority to U.S. Provisional Application No. 61/922,541 entitled MANAGING DYNAMIC FORCES ON A NUCLEAR REACTOR SYSTEM and filed on Dec. 31, 2013, which is herein incorporated by reference in its entirety. This disclosure generally relates to systems, devices and methods for attenuating dynamic forces and/or seismic forces on a nuclear reactor system or other structure. Seismic isolation may be utilized to control or reduce the response of a component or structure to vertical and horizontal ground-input motions or accelerations. Seismic isolation may accomplish this by decoupling the motion of the component/structure from the driving motion of the substructure. In some instances, hardware (e.g., springs) may be positioned between the substructure and superstructure. Use of such hardware may minimize the dynamic response of the structure by increasing the fundamental period of vibration for the component or structure, resulting in lower in-structure accelerations and forces. To further reduce spectral response amplitudes (e.g., deflections, forces, etc.), other mechanisms may be employed that effectively reduce the peak amplitude to manageable levels. Piping and other connections may be provided between a nuclear reactor and a secondary cooling system or other systems in the power generation facility. In the event of an earthquake or other seismic activity, significant forces or vibration may be transferred to, or by, the connections, which can place great stress on the connections. Forces resulting from thermal expansion also place stress on the connections. Maintaining integrity of these connections helps discourage the inadvertent release of radioactive or other materials from the various systems, and reduces maintenance or damage that might otherwise occur if one or more of the connections fail. During a seismic event, dynamic and/or seismic forces may be transmitted from the ground, support surface, or surrounding containment building to a reactor module. The seismic forces which are transferred to the reactor module may experience a cumulative increase and/or amplification in amplitude and/or frequency depending on the number and/or length of intervening structures and/or systems that the seismic forces travel in reaching the reactor module. If the seismic forces become large enough, the reactor core and/or fuel elements may be damaged. The present invention addresses these and other problems. FIG. 1 is a block diagram illustrating a nuclear reactor system 100 (e.g., a nuclear reactor) that includes one or more seismic isolation assemblies 25. In some aspects, the nuclear reactor system 100 is a commercial power pressurized water reactor that utilizes natural circulation of a primary coolant to cool a nuclear core and transfer heat from the core to a secondary coolant through one or more heat exchangers. The secondary coolant (e.g., water), once heated (e.g., to steam, superheated steam or otherwise), can drive power generation equipment, such as steam turbines or otherwise, before being condensed and returned to the one or more heat exchangers. With respect to the nuclear reactor system 100, a reactor core 20 is positioned at a bottom portion of a cylinder-shaped or capsule-shaped reactor vessel 70. Reactor core 20 includes a quantity of nuclear fuel assemblies, or rods (e.g., fissile material that produces, in combination with control rods, a controlled nuclear reaction), and optionally one or more control rods (not shown). As noted above, in some implementations, nuclear reactor system 100 is designed with passive operating systems (e.g., without a circulation pump for the primary coolant) employing the laws of physics to ensure that safe operation of the nuclear reactor 100 is maintained during normal operation or even in an emergency condition without operator intervention or supervision, at least for some predefined period of time. A cylinder-shaped or capsule-shaped containment vessel 10 surrounds reactor vessel 70 and may be partially or completely submerged in a reactor pool, such as below waterline 90 (which may be at or just below a top surface 35 of the bay 5), within reactor bay 5. The volume between reactor vessel 70 and containment vessel 10 may be partially or completely evacuated to reduce heat transfer from reactor vessel 70 to the reactor pool. However, in other implementations, the volume between reactor vessel 70 and containment vessel 10 may be at least partially filled with a gas and/or a liquid that increases heat transfer between the reactor and containment vessels. In the illustrated implementation, reactor core 20 is submerged within a liquid, such as water, which may include boron or other additives, which rises into channel 30 after making contact with a surface of the reactor core. The upward motion of heated coolant is represented by arrows 40 (e.g., primary coolant 40) within channel 30 (e.g., riser 30). The coolant travels over the top of heat exchangers 50 and 60 and is drawn downward by density difference along the inner walls of reactor vessel 70 thus allowing the coolant to impart heat to heat exchangers 50 and 60. After reaching a bottom portion of the reactor vessel 70, contact with reactor core 20 results in heating the coolant, which again rises through channel 30. Although heat exchangers 50 and 60 are shown as two distinct elements in FIG. 1, heat exchangers 50 and 60 may represent any number of helical (or other shape) coils that wrap around at least a portion of channel 30. Normal operation of the nuclear reactor module proceeds in a manner wherein heated coolant rises through channel 30 and makes contact with heat exchangers 50 and 60. After contacting heat exchangers 50 and 60, the coolant sinks towards the bottom of reactor vessel 70 in a manner that coolant within reactor vessel 70 remains at a pressure above atmospheric pressure, thus allowing the coolant to maintain a high temperature without vaporizing (e.g., boiling). As coolant within heat exchangers 50 and 60 increases in temperature, the coolant may begin to boil. As the coolant within heat exchangers 50 and 60 begins to boil, vaporized coolant, such as steam, may be used to drive one or more turbines that convert the thermal potential energy of steam into electrical energy. After condensing, coolant is returned to locations near the base of heat exchangers 50 and 60. In the illustrated implementation, a downcomer region between the reflector 15 and the reactor vessel 70 provides a fluid path for the primary coolant 40 flowing in an annulus between the riser 30 and the reactor vessel 70 from a top end of the vessel 70 (e.g., after passing over the heat exchangers 50, 60) and a bottom end of the vessel 70 (e.g., below the core 20). The fluid path channels primary coolant 40 that has yet to be recirculated through the core 20 into convective contact with at least one surface of the reflector 15 in order to cool the reflector 15. As illustrated, the containment vessel 10 may be coupled to the reactor bay 10 through one or more seismic isolation assemblies 25. As shown in FIG. 1B, each seismic isolation assembly 25 may be mounted in or on an embedment 29 that extends from an interior surface 27 of the reactor bay 5. Although four seismic isolation assemblies 25 are shown in FIG. 1B (one per wall of the interior surface 27 of the bay 5), there may be more or fewer seismic isolation assemblies 25 to support the containment vessel 10, as necessary. The containment vessel 10, in this implementation, includes support lugs 33 that rest on the embedments 29 adjacent the seismic isolation assemblies 25. In some implementations, the seismic isolation assemblies 25, embedments 29, and support lugs 33 may be positioned at or near an axis through the containment vessel 10 that intersects an approximate center of gravity (CG), or slightly above the CG, of the vessel 10. The containment vessel 10 (and components therein) may be supported by the seismic isolation assemblies 25, embedments 29, and support lugs 33 in combination with a buoyancy force of the pool of liquid 90 acting on the containment vessel 10. Generally, the illustrated seismic isolation assemblies 25 (shown in more detail in FIGS. 2A-2B and 3A-3B) may include one or more components that experience plastic deformation in response to a seismic event (or other motion-causing event) that results in a force on the containment vessel 10. For example, in the case of a seismic event, seismic energy may be dissipated through one or more portions of the assemblies 25 (e.g., a series of conical, or other shapes bounded by convex surfaces, elements) by penetrating and contracting such portions to plastically deform the one or more portions of assemblies 25. Energy may be absorbed by plastic deformation and friction between moving elements of the assemblies 25. In some implementations, stiffness of the assembly 25 may be controlled by sizing the plastically deformable elements. For example, a multiple of cones, dies, and cylinders (as the plastically deformable elements) can be arranged in an enclosure as shown in more detail in FIGS. 3A-3B. The enclosure of the assembly 25 may move relative to the support lugs 29 (or other reactor bay embedment). In the case of a seismic event such as an earthquake, the seismic isolation assemblies 25 may contribute to a safe shut down of the nuclear reactor system 100, while maintaining coolable geometry. In some implementations, the seismic isolation assemblies 25 may be sized for a sliding force above forces associated with an operating basis earthquake (OBE). An OBE may be typically one third to one half of forces associated with a safe shutdown earthquake (SSE). The SSE event is classified as a faulted condition, service Level D. The OBE event is classified as an Upset condition, service Level B. When the reactor system 100 is subject to an earthquake below the intensity of an OBE, operations may resume shortly after the event without any major repairs or inspections. As a result, during an OBE, the seismic isolation assemblies 25 may not undergo any plastic deformation. For instance, if the seismic isolation assemblies 25 may remain linear (e.g., experience no or negligible plastic deformation) during an OBE, replacement of the isolation assemblies 25 may not be necessary. When the reactor system 100 is subject to an SSE, the isolation assemblies 25 may be plastically exercised and may be removed and/or replaced. Replacement of the seismic isolation assemblies 25, may be much less costly, however, than replacement of other components (e.g., of the reactor system 100). FIGS. 2A-2B illustrate an example implementation of a seismic isolation assembly 200. In some aspects, the seismic isolation assembly 200 may be used as the seismic isolation assembly 25 shown in FIGS. 1A-1B. FIG. 2A shows an isometric view of several seismic isolation assemblies 200 mounted in an embedment 29, while FIG. 2B shows a top view of the seism isolation assemblies 200 mounted in the embedment 29, with several internal components exposed for detail. As shown in FIG. 2A, several (e.g., three) seismic isolation assemblies 200 may be mounted against vertical surfaces of the embedment 29, thereby defining a pocket (e.g., for receiving a support lug of the containment vessel 10). Each seismic isolation assembly 200 may affixed to one of the vertical surfaces or may simply rest in the embedment 29 in contact with the vertical surface. In this example implementation, an enclosure 205 of the seismic isolation assembly 200 includes a rectangular cuboid portion that has a tapered, or ramped, top portion. Other shapes are contemplated by the present disclosure however. In some aspects, one or more plastically deformable elements may be mounted and/or contained, at least partially, within the cuboid portion 201. FIG. 2B illustrates one or more internal components of each seismic isolation assembly 200. As shown, each seismic isolation assembly 200 may include a conical stretching element 210, a contracting die 215, and a cylindrical plasticity element 220. In some aspects, as illustrated in FIG. 2B, there may be several (e.g., between two and five) sets of the conical stretching element 210, contracting die 215, and cylindrical plasticity element 220. Other numbers of sets are also contemplated by the present disclosure and may depend, at least in part, on a size (e.g., dimension in the x or z direction shown in FIG. 2A) of the particular seismic isolation assembly 200. In the illustrated implementation, a portion of the cylindrical plasticity element 220 may extend from the enclosure 205 and attach (e.g., rigidly or semi-rigidly, for example, by welding) to the embedment 29 (and by extension to the reactor bay 5). Thus, in some aspects, dynamic forces (e.g., seismic forces) that transmit through the reactor bay 5 may be borne by the seismic isolation assembly 200, through the cylindrical plasticity element 220. In some aspects, an overall stiffness of each seismic isolation assembly 200 may be based, at least in part on the number of sets of the conical stretching element 210, contracting die 215, and cylindrical plasticity element 220, as well as the relative size of one or more of the conical stretching element 210, contracting die 215, and cylindrical plasticity element 220 within the enclosure 205. For example, turning briefly to FIG. 4, an example idealized representation 400 of the example implementation of the seismic isolation assembly 200. As shown in FIG. 4, a spring-slider and damper are positioned in parallel. Representation 400 includes an “I” node that represents a reactor building wall embedment (e.g., the embedment 29) and a “J” node that represents the enclosure 205 of the seismic isolation assembly 200. The stiffness of the plasticity elements (e.g., the conical stretching element 210, contracting die 215, and cylindrical plasticity element 220) is represented by K1 (shown as a resistance element). In some aspects, other “resistant” elements may also be accounted for, as shown in FIG. 4. For example, a hydraulic damping feature is represented by the damping coefficient, C. Additional stiffness elements (e.g., springs, Belleville washers, or otherwise) may also be used in the nuclear reactor system 100 (e.g., mounted within the enclosures 205 or mounted between the enclosures 205 and the embedments 29) to dissipate seismic forces (e.g., in parallel with the seismic isolation assembly 200) and are generally represented by K2. A gap is also shown that represents a space (e.g., filled with a gas or fluid) between the seismic isolation assembly 200 and the embedment 29 (e.g., between nodes J and I). The FSLIDE value, as shown, represents an absolute value of a spring force that must be exceeded before sliding occurs. This sliding force may result from plastic deformation (e.g., of one or more of the conical stretching element 210, contracting die 215, and cylindrical plasticity element 220) and friction forces. In some aspects, K1 may be chosen, and in some cases chosen in parallel with K2 and/or C, to attain a particular FSLIDE. The particular FSLIDE may be large enough so that seismic forces acting at node I from an event (e.g., an OBE or SSE event, or other event) do not exceed FSLIDE and, therefore, are completely or mostly borne by the elastic deformation that occurs in K1 (as well as, in some examples, spring and dampening of K2 and C, respectively). Turning briefly to FIG. 5, a force-deflection diagram 500 illustrates the relationship (without effects of K2 and C) between seismic force on the seismic isolation assembly 200 and deflection. As illustrated, below the FSLIDE force, the system is linear (assuming that there is no gap between the seismic isolation assembly 200 and the embedment 29). When sliding occurs, the absorbed energy is proportional to the sliding force times the sliding distance. In this illustration, the K1 and K2 springs are shown as linear (proportional) springs, but it can be generalized to any type of non-linear (inelastic, non-proportional) spring. For example, in other representations, the number of spring-damper-slider elements can be in any number and combination. Returning to FIG. 2A, the illustrated seismic isolation assemblies 200 are attached to the embedment 29 through the cylindrical plasticity elements 220. As illustrated, there may be multiple sets of the conical stretching element 210, contracting die 215, and cylindrical plasticity element 220 arranged vertically within the enclosures 205. Contact between the embedment 29 and the cylindrical plasticity elements 220 may drive the relative movement of the enclosures 205 with respect to the bay 5 (and thus any structure that contains and is in contact with the bay 5). The number of plasticity mechanisms inside each enclosure 205 (e.g., sets of the conical stretching element 210, contracting die 215, and cylindrical plasticity element 220) may be a function of an amount of dissipative energy needed to achieve adequate damping of the structure (e.g., the bay 5 or other structure) during a seismic event. The size of the enclosure 205 may be determined by an allowable relative displacement of the nuclear reactor system 100 with respect to the structure (e.g., about 4 inches as a maximum allowable displacement). The size of each isolation assembly 200 can be rather compact. In some aspects, the conical stretching elements 210 and the cylindrical plasticity elements 220 may work together to dissipate forces in the X and Z directions as shown in FIG. 2A. For example, the conical stretching elements 210 may dissipate energy by plastically deforming the cylindrical plasticity elements 220 (e.g., by moving into the elements 210 toward the embedment 29) in response to forces in the X and Z directions. In some aspects, the contracting dies 215 may move with the movement of the conical stretching elements 210. In other aspects, the contracting dies 215 may simply be bores in the enclosures 205 through which the cylindrical plasticity elements 220 extend to contact the embedment 29, rather than separate components. Based on a sufficient seismic force, movement of the conical stretching elements 210 into the cylindrical plasticity elements 220 (e.g., into the bores 230 as shown in FIG. 3A) may result in semi-permanent or permanent plastic deformation of the cylindrical plasticity elements 220. Further, during (and after) plastic deformation of the cylindrical plasticity elements 220, seismic forces may also be dissipated through friction, and associated heat, between the conical stretching elements 210 and the cylindrical plasticity elements 220. FIGS. 3A-3B illustrate portions of example implementations of the seismic isolation assembly 200. FIG. 3A shows a close-up view of the plastically deformable elements mounted in the enclosure 205. As further shown in FIG. 3A, portions of the enclosure 205 and the plastically deformable elements may be surrounded by the pool of liquid 90 (e.g., water or other fluid). As described above, the liquid 90 may be a hydraulic damping feature (e.g., represented by the damping coefficient, C, in FIG. 4) that helps dissipate seismic forces, as well as heat generated by frictional forces of the plastically deformable elements as they slide/deform in response to the seismic forces. In some aspects, a bore 230 of the cylindrical plasticity element 220 may enclose a working fluid (e.g., a gas such as air, or a liquid such as water). The working fluid may provide further dissipative affects for any seismic forces received by the seismic isolation assembly 200. For example, the working fluid may dissipate some of the energy of the seismic event by compressing within the bore 230 as the conical stretching element 210 is forced into the bore 230 of the cylindrical plasticity element 220. Turning to FIG. 3B, another implementation is shown that includes a fluid orifice 225 that fluidly connects the bore 230 and the reactor pool 90. In this aspect, the working fluid may be a portion of the pool 90. The working fluid, in both implementations shown in FIGS. 3A-3B, may provide further hydraulic damping to dissipate the seismic forces and movement due to such forces. For example, expelling the working fluid from the bore 230 during movement of the conical stretching element 210 into the bore 230 of the cylindrical plasticity element 220 may further dissipate seismic energy through hydraulic damping. A number of implementations related to FIGS. 1-5 have been described. Nevertheless, it will be understood that various modifications may be made. For example, the steps of the disclosed techniques may be performed in a different sequence, components in the disclosed systems may be combined in a different manner, and/or the components may be replaced or supplemented by other components. Accordingly, other implementations are within the scope of the following examples. A nuclear reactor seismic isolation assembly may include one or more deformable elements that, in response to energy generated by a seismic event and transmitted to the assembly through a structure that houses a nuclear reactor containment vessel, plastically deform to at least partially dissipate the seismic energy. In some aspects, portions of the energy are dissipated through the plastic deformation while other portions of the energy are dissipated through friction between two or more components of the assembly. In still other aspects, a working fluid may be compressed within the assembly to dissipate some of the seismic energy. A nuclear reactor system may include one or more seismic isolation assemblies according to the present disclosure may limit a reaction force (or forces) on a structure (e.g., a containment pool structure or building structure) to a sliding force. The disclosed seismic isolation assemblies may be geographically neutral and thus be used world-wide in nuclear reactor systems. As another example, the seismic isolation assemblies may be passive isolators rather than active isolators, thereby reducing maintenance and inspection complexities (e.g., by limiting to visual inspection or otherwise). As another example, the disclosed seismic isolation assemblies may accommodate or promote a modular building design for nuclear reactor system structures. A nuclear reactor seismic isolation assembly may comprise an enclosure that defines a volume and a plastically-deformable member mounted, at least in part, within the volume. A stretching member may be moveable within the enclosure to plastically-deform the plastically deformable member in response to a dynamic force exerted on the enclosure. The enclosure may be attachable to a portion of a nuclear reactor containment vessel. The dynamic force may comprise a seismically generated force. In some examples, the plastically deformable member may comprise a first portion mounted within the enclosure and a second portion that extends through a die member to an exterior of the enclosure. The second portion may comprise a weldable portion. Additionally, the die member may be moveable with the stretching member in response to the dynamic force exerted on the enclosure. The stretching member may be mounted within a portion of a bore that extends through the plastically-deformable member. The portion of the bore may comprise a first diameter approximately equal to an outer dimension of the stretching member, the bore comprising another portion that comprises a second diameter smaller than the first diameter. Additionally, the second diameter may be stretched to approximately equal the first diameter based on movement of the stretching element through the bore in response to the dynamic force exerted on the enclosure. In some examples, the bore may at least partially enclose a working fluid that dissipates at least a portion of energy generated by the dynamic force exerted on the enclosure based on movement of the stretching element through the bore in response to the dynamic force exerted on the enclosure. The working fluid may comprise a portion of a fluid enclosed in a nuclear reactor bay. A method for managing dynamic forces and/or for attenuating seismic forces may comprise receiving a force on a seismic isolation assembly in contact with a nuclear reactor pressure vessel, wherein the force may be generated at least in part by a seismic event. The received force may be transmitted through an enclosure of the seismic isolation assembly to a stretching member, and the stretching member may be moved within the enclosure based on the received force. The method may further comprise plastically deforming a deformable member, that is at least partially enclosed in the enclosure, with the stretching member, and dissipating at least a portion of the received force based on plastically deforming the deformable member. Additionally, the method may comprise generating friction between the deformable member and the stretching member based on repeated movement of the stretching member into the deformable member based on the received force, and dissipating another portion of the received force based on the generated friction. In some examples, a working fluid enclosed in a chamber of the deformable element may be compressed based on movement of the stretching member into the deformable member based on the received force, and another portion of the received force may be dissipated based on the compression of the working fluid. The working fluid may be expelled to a reactor bay that encloses a liquid, through a fluid passageway that fluidly couples the chamber and the reactor bay. Additionally, another portion of the received force may be dissipated through the liquid enclosed in the reactor bay. One or more spring members may be compressed based on movement of the stretching member into the deformable member based on the received force, and another portion of the received force may be dissipated based on the compression of the one or more spring members. In some examples, the received force may be transmitted through the deformable member that is in contact with a structure that houses the nuclear reactor pressure vessel. A nuclear reactor system may comprise a reactor bay that encloses a liquid and a nuclear reactor containment vessel that is mounted within the reactor bay with lugs positioned in embedments of the reactor bay. Additionally, the system may comprise seismic isolation assemblies mounted in the embedments and between the lugs and walls of the embedments. Each of the seismic isolation assemblies may comprise an enclosure that defines a volume, a plastically-deformable member mounted, at least in part, within the volume, and a stretching member moveable within the enclosure to plastically-deform the plastically-deformable member in response to a dynamic force exerted on the reactor bay. The plastically-deformable member may comprise a first portion mounted within the enclosure and a second portion that extends through a die member to a wall of one of the embedments. The second portion may be anchored to the wall. In some examples, the die member may be moveable with the stretching member in response to the dynamic force exerted on the reactor bay. Additionally, the stretching member may be mounted within a portion of a bore that extends through the plastically deformable member. The portion of the bore may comprise a first diameter approximately equal to an outer dimension of the stretching member, and another portion that comprises a second diameter smaller than the first diameter. In some examples, the second diameter may be stretched to approximately equal the first diameter based on movement of the stretching element through the bore in response to the dynamic force exerted on the reactor bay. The bore may at least partially enclose a working fluid that dissipates at least a portion of energy generated by the dynamic force exerted on the enclosure based on movement of the stretching element through the bore in response to the dynamic force exerted on the reactor bay. The nuclear reactor system may further comprise a passage that fluidly couples the bore to a volume defined by the reactor bay. The working fluid may comprise a portion of a fluid enclosed in the volume. FIG. 6 illustrates an example power module assembly comprising a containment vessel 624, reactor vessel 622 and a support structure 620. The containment vessel 624 may be cylindrical in shape, and may have ellipsoidal, domed or hemispherical upper and lower ends 626, 628. The entire power module assembly 625 may be submerged in a pool of liquid 636 (for example, water) which serves as an effective heat sink. In other examples, the power module assembly 625 may be partially submerged in the pool of liquid 636. The pool of liquid 636 is retained in reactor bay 627. The reactor bay 627 may be comprised of reinforced concrete or other conventional materials. The pool of liquid 636 and the containment vessel 624 may further be located below ground 609. In some examples, the upper end 626 of the containment vessel 624 may be located completely below the surface of the pool of liquid 636. The containment vessel 624 may be welded or otherwise sealed to the environment, such that liquids and gas do not escape from, or enter, the power module assembly 625. The containment vessel 624 is shown suspended in the pool of liquid 636 by one or more support structures 620, above a lower surface of the reactor bay 627. The containment vessel 624 may be made of stainless steel or carbon steel, and may include cladding. The power module assembly 625 may be sized so that it can be transported on a rail car. For example, the containment vessel 624 may be constructed to be approximately 4.3 meters in diameter and 17.7 meters in height (length). Refueling of a reactor core may be performed by transporting the entire power module assembly 625 by rail car or overseas, for example, and replacing it with a new or refurbished power module assembly which has a fresh supply of fuel rods. The containment vessel 624 encapsulates and, in some conditions, cools the reactor core. The containment vessel 624 is relatively small, has a high strength and may be capable of withstanding six or seven times the pressure of conventional containment designs in part due to its smaller overall volume. Given a break in the primary cooling system of the power module assembly 625 no fission products are released into the environment. The power module assembly 625 and containment vessel 624 are illustrated as being completely submerged in the pool of liquid 636. All sides, including the top and bottom, of the containment vessel 624 are shown as being in contact with, and surrounded by, the liquid 636. However in some examples, only a portion of containment vessel 624 may be submerged in the pool of liquid 636. The one or more support structures 620 are located at an approximate midpoint of the containment vessel 624. In some examples, the one or more support structures 620 are located at an approximate center of gravity (CG), or slightly above the CG, of the power module 625. The power module 625 is supported by the support structure 620 in combination with a buoyancy force of the pool of liquid 636 acting on the containment vessel 624. In some examples, the power module assembly 625 is supported by two support structures 620. The first support structure may be located on a side of the power module assembly 625 opposite the second support structure. The one or more support structures 620 may be configured to support both the containment vessel 624 and the reactor vessel 622. In s, the one or more support structures 620 are located at an approximate CG, or slightly above the CG, of the reactor vessel 622. FIG. 7 illustrates a side view of the power module assembly 625 of FIG. 6. The containment vessel 624 as well as the reactor vessel 622, may be configured to pivot about the support structure 620, due to a rotational force RF acting on the power module 625. In some examples, the support structure 620 is located slightly above the CG of the power module 625, so that the lower end 628 tends to return to a bottom facing position within the reactor bay 627 due to gravity after the rotational force RF has subsided. The rotation of the containment vessel 624 also allows for greater maneuverability during installation or removal of the power module assembly 625 from the reactor bay 627. In some examples, the containment vessel 624 may be rotated between a vertical and a horizontal orientation or position of the power module assembly 625. The power module 625 is further illustrated as comprising a base support, such as a base skirt 730, located at the lower end 628 of the containment vessel 624. The base skirt 730 may be rigidly mounted to, welded on, and/or form an integral part of, the containment vessel 624. In some examples, the base skirt 730 may be designed to support the weight of the power module 625 if the base skirt 730 is placed on the ground, on a transport device, or in a refueling station, for example. During normal operation (e.g. power operation) of the power module 625, the base skirt 730 may be suspended off the ground or positioned above the bottom of the reactor bay 627, such that the base skirt 730 is not in contact with any exterior component or surface. When the power module 625 rotates about the support structure 620, the lower end 628 of the containment vessel 625 tends to move in a lateral or transverse direction Lo. The base skirt 730 may be configured to contact an alignment device 375 located in the pool of liquid 636 when the containment vessel 624 pivots a predetermined amount about the support structure 620. For example, the alignment device 735 may be sized so that the power module 625 is free to rotate within a range of motion or particular angle of rotation. The alignment device 735 may comprise an exterior diameter that is smaller than an interior diameter of the base skirt 730. The alignment device 735 may be sized to fit within the base skirt 730, such that the base skirt 730 does not contact the alignment device 735 when the power module 625 is at rest. In some examples, the base skirt 730 may be configured to contact the alignment device 735 when the containment vessel 624 pivots about the support structure 620. The base skirt 730 may not inhibit a vertical range of motion of the containment vessel 623, in the event that a vertical force acts upon the power module 625. The alignment device 735 may be rigidly mounted (e.g. bolted, welded or otherwise attached) to the bottom of the reactor bay 627. In some examples, one or more dampeners 638 are located between the base skirt 730 and the alignment device 735 to attenuate a contact force between the base skirt 730 and the alignment device 735 when the power module 625 pivots or rotates. The one or more dampeners 738 may be mounted to or otherwise attached to either the alignment device 735 (as illustrated) or the base skirt 730. FIG. 8 illustrates a partial view of an example support structure 840 for a power module assembly comprising a seismically isolated containment vessel 824. The support structure 840 comprises a support arm 845 and a mounting structure 847. The support arm 845 may be located at an approximate midpoint of the containment vessel 824. The mounting structure 847 may be submerged in liquid (for example water). Additionally, the mounting structure 847 may be an extension of, mounted to, recessed in, or integral with, the wall of the reactor bay 627 (FIG. 6). A damping device 846 may be disposed between the support arm 845 and the mounting structure 847. At least a portion of the weight of the containment vessel 824 may be transferred to the support structure 847 through the damping device 846. Damping device 846 may be elastic, resilient or deformable, and may comprise a spring, pneumatic or hydraulic shock absorber, or other vibration or force attenuating device known in the art. In some examples, the damping device 846 comprises natural or synthetic rubber. The damping device 846 may comprise an elastic material that is manufactured from petroleum or other chemical compounds and that is resistant to material breakdown when exposed to radiation or humidity. In yet another example, the damping device 846 comprises soft deformable metal or corrugated metal. The damping device 846 may be configured to attenuate dynamic or seismic forces transferred by and between the support arm 845 and the mounting structure 847. For example, a vertical or longitudinal force FV, acting along a longitudinal or lengthwise direction of the containment vessel 824, may act through the damping device 846. Additionally, a horizontal or transverse force FH may be exerted on the damping device 846 in any direction perpendicular to the longitudinal force FV. Transverse force FH may be understood to include a direction vector located in the plane defined by the X and Z coordinates of illustrative coordinate system 48, whereas the longitudinal force FV may be understood to include a direction vector oriented in the Y coordinate, the Y coordinate being perpendicular to the X-Z plane of the illustrative coordinate system 848. In some examples, by placing the support arm 845 at an approximate center of gravity of the containment vessel 824, a transverse force FH acting on the power module 625 tends to cause the containment vessel 824 to slide rather than rotate. Locating the support arm 845 on the containment vessel 824 at a particular height or position provides for controllability for how the containment vessel 824 will behave when it is subjected to one or more forces FH, FV, or RF. The damping device 846 may compress in a vertical direction to absorb or attenuate the longitudinal force FV. In some examples, the damping device 846 may be configured to compress or flex in a horizontal direction to attenuate the transverse force FH. Additionally, the damping device 846 may be configured to slide along the mounting structure 847 within the X-Z plane during a seismic activity, such as an earthquake or explosion. Forces FV and FH may also be understood to result from thermal expansion of one or more components of the power module 625, including containment vessel 824, in any or all of the three dimensions X, Y, Z. As a result of the compression or movement of the damping device 846, less of the forces FV and FH are transferred from the mounting structure 847 to the containment vessel 824, or from the containment vessel 824 to the mounting structure 847. The containment vessel 824 experiences less severe shock than what might otherwise be transferred if the support arm 845 were rigidly mounted to, or in direct contact with, the mounting structure 847. The containment vessel 824 may be configured to rotate about the horizontal axis X, due to a rotational force RF acting on the power module 625 (FIG. 7). Support arm 845 may be rigidly attached to the containment vessel 824. The one or more elastic damping devices 846 may be located between, and in contact with, both the support arm 845 and the mounting structure 847 located in the liquid 636 (FIG. 6). The elastic damping device 846 may provide a pivot point between the support arm 845 and the support structure 847, wherein the containment vessel 24 pivots or rotates about the elastic damping device 846, similar to that illustrated by FIG. 7. The weight of the containment vessel 824 may be supported, in part, by a buoyancy force of the liquid 636. The surrounding liquid 636 (FIG. 6) also serves to attenuate any of the transverse force FH, longitudinal force FV, and rotational force RF acting on the containment vessel 824. In some examples, the support arm 845 comprises a hollow shaft 829. The hollow shaft 829 may be configured to provide a through-passage for an auxiliary or secondary cooling system. For example, piping may exit the containment vessel 824 via the hollow shaft 829. FIG. 9 illustrates a partial view of a support structure 950 for a seismically isolated containment vessel 924 comprising a support arm 955 and multiple elastic damping devices 952, 954. The first elastic damping device 952 may be located between the support arm 955 and a lower mounting structure 957. The second elastic damping device 954 may be located between the support arm 955 and an upper mounting structure 958. In some examples, the first and second elastic damping devices 952, 954 are mounted to or otherwise attached to the support arm 955. In other examples, one or both of the first and second elastic damping devices 952, 954 are mounted to the lower and upper mounting structures 957, 958, respectively. At least a portion of the weight of the containment vessel 924 may be transferred to the lower support structure 957 through the first elastic damping device 952. The first elastic damping device 952 may be under compression when the containment vessel 924 is at rest. The first elastic damping device 952 may be understood to attenuate longitudinal force acting between the support arm 955 and the lower mounting structure 957. The second elastic damping device 952 may also be understood to attenuate longitudinal force acting between the support arm 955 and the upper mounting structure 958. A longitudinal or vertical movement of the containment vessel 924 may be constrained by the lower and upper mounting structures 957, 958 as they come into contact with, or cause a compression of, the first and second elastic damping devices 952, 954, respectively. First and second elastic damping devices 952, 954 may provide similar functionality as a snubber or pair of snubbers in a conventional shock absorber. In some examples, the lower mounting structure 957 comprises a recess 956. The recess 956 may be sized such that it has an interior dimension or diameter that is larger than an exterior dimension or diameter of the first elastic damping device 952. The first elastic damping device 952 is illustrated as being seated or located in the recess 956. The recess 956 may operate to constrain a movement of the containment vessel 924 in one or more lateral or transverse directions. The first elastic damping device 952 may be configured to compress or flex when it presses up against a wall of the recess 956. In some examples, the recess 956 may restrict an amount or distance that the first elastic damping device 952 is allowed to slide on the lower mounting structure 957 when the containment vessel 924 experiences lateral or transverse force. FIG. 10 illustrates a partial view of an elastic damping and retaining structure 1060 for a seismically isolated containment vessel 1024. The damping and retaining structure 1060 comprises a deformable portion 1066. The deformable portion 1066 may be dome shaped, elliptical or hemispherical in shape. Mounting structure 1067 may comprise a recess 1068, and the deformable portion 1066 may be seated or located in the recess 1068. The deformable portion 1066 and recess 1068 may be understood to function similarly as a ball joint, wherein the deformable portion 1066 rotates or pivots within the recess 1068. The recess 1068 is illustrated as being concave in shape. The mounting structure 1067 may be configured to constrain a movement of the containment vessel 1024 as a result of transverse force FH being applied in a lateral plane identified as the X-Z plane in the illustrative coordinate system 1048. Additionally, the mounting structure 1067 may be configured to constrain a longitudinal movement of the containment vessel 1024 as a result of a longitudinal force FV being applied in a direction Y perpendicular to the X-Z plane. The containment vessel 1024 may be configured to rotate about the horizontal axis X, due to a rotational force RF acting on the power module 625 (FIG. 7). In some examples, the recess 1068 forms a hemispherical, domed or elliptical bowl. A base support, such as base skirt 630 (FIG. 6), located at the bottom end of the containment vessel 1024 may be configured to constrains a rotation of the containment vessel 1024 as the deformable portion 1066 pivots or rotates in the recess 1068. The mounting structure 1067 may be configured to support some or all of the weight of the power module. In some examples, a buoyancy force of the liquid 636 supports substantially all of the weight of the power module, such that the recess 1068 of the mounting structure 1067 may primarily operate to center or maintain a desired position of the power module. FIG. 11 illustrates a partial view of the elastic damping and retaining structure 1060 of FIG. 10 responsive to a longitudinal force FV. The recess 1068 in the mounting structure 1067 may comprise a radius of curvature R2 that is greater than a radius of curvature R1 of the deformable portion 1066 of the damping and retaining structure 1060 when the containment vessel 1024 is at rest. Longitudinal force FV may be applied to support arm 1065 (FIG. 10) as a result of vertical movement of the containment vessel 1024, or as a result of force transmitted from the mounting structure 1067 to the containment vessel 1024. The longitudinal force may result from an earthquake or explosion for example. When a dynamic longitudinal force FV is applied to the support arm 1065, the damping device may be configured to compress from a static condition illustrated in solid lines by reference number 1066, to a dynamic condition illustrated in dashed lines by reference number 1066A. The radius of curvature of the deformable portion 1066 temporarily approximates the radius of curvature R2 of the recess 1068 in the dynamic condition 1066A. As the effective radius of the deformable portion 1066 increases, this results in an increased contact surface to form between the deformable portion 1066 and the recess 1068. As the contact surface increases, this acts to resist or decrease additional compression of the deformable hemispherical portion 1066, and attenuates the longitudinal force FV. In some examples, the effective radius of curvature of the deformable hemispherical portion 1066 increases with an increase in longitudinal force FV. When the dynamic longitudinal force FV has attenuated, the deformable portion 1066 may be configured to retain its original radius of curvature R1. FIG. 12 illustrates a partial view of the elastic damping and retaining structure 1060 of FIG. 10 responsive to a transverse force FH. The recess 1068 may be configured to constrain a movement of the deformable portion 1066 in at least two degrees of freedom. For example, the movement of the deformable portion 1066 may be constrained in the X and Z directions of the illustrative coordinate system 1048 of FIG. 10. The deformable portion 1066 may be configured to compress or flex when it presses up against a wall of the recess 1068. The compression or deformation of the deformable portion 1066 attenuates the horizontal force FH. In some examples, the recess 1068 may restrict an amount or distance that the deformable portion 1066 is allowed to slide on the mounting structure 1067 when the containment vessel 1024 experiences transverse force FH. When a transverse force FH is applied to the support arm 1065, the damping device moves or slides from the static condition illustrated in solid lines by reference number 1066, to the dynamic condition illustrated in dashed lines by reference number 1066B. Whereas the recess 956, 1068 are illustrated in FIGS. 9 and 10 as being formed in the mounting structure 957, 1067, other examples may include where the recess 956, 1068 is formed in the support arm 955, 1065, and wherein the damping device 952, 1066 is mounted to the mounting structure 957, 1067. These alternate examples may otherwise operate similarly as the examples illustrated in FIG. 9 or 10, to constrain movement of the containment vessel 924, 1024 in one or both of the transverse and longitudinal directions. FIG. 13 illustrates a partial view of an elastic damping and retaining structure 1370 for a seismically isolated power module 1380. The power module 1380 comprises a reactor vessel 1322 and a containment vessel 1324. The elastic damping and retaining structure 1370 comprises one or more support arms, or trunnions, and one or more mounting structures. A first trunnion 1375, protrudes or extends from the reactor vessel 1322. The reactor vessel trunnion 1375 provides similar functionality as one or more of the support arms described above with respect to FIGS. 6-10. A second trunnion 1385 protrudes or extends from the containment vessel 1324. The reactor vessel trunnion 1375 lies along the same, single axis of rotation as the containment vessel trunnion 1385. The axis of rotation X is shown in illustrative coordinate system 1348. One or both of the reactor vessel 1322 and containment vessel 1324 may rotate about the axis of rotation X when a rotational force RF acts on the power module 1325. The reactor vessel 1322 and containment vessel 1324 may rotate in the same or in opposite rotational directions from each other. Reactor vessel trunnion 1375 is shown supported on a first mounting structure 1377. The mounting structure 1377 protrudes or extends from the containment vessel 1324. The reactor vessel trunnion 1375 may be configured to move or slide along the mounting structure 1377 when horizontal force FH1 or FH2 acts on the power module 1380. A first damping element 1376 may be configured to attenuate or reduce the impact of horizontal force FH2 transmitted by or between the reactor vessel 1322 and containment vessel 1324. The first damping element 1376 also helps to center or maintain a respective position or distance between the reactor vessel 1322 and containment vessel 1324 when the power module 1380 is at rest or in a static condition. Containment vessel trunnion 1385 is shown supported on a second mounting structure 1387. In some examples, the mounting structure 1387 protrudes or extends from a reactor bay wall 1327. The containment vessel trunnion 1385 may move or slide along the mounting structure 1387 when horizontal force FH1 or FH2 acts on the power module 1380. A second damping element 1386 may be configured to attenuate or reduce the impact of horizontal force FH1 transmitted by or between the containment vessel 1324 and the reactor bay wall 1327. The second damping element 1386 also helps to center or maintain a respective position or distance between the containment vessel 1324 and the reactor bay wall 1327 when the power module 1380 is at rest or in a static condition. The first damping element 1376 is shown housed in the reactor vessel trunnion 1375. A reactor vessel retaining pin 1390 is located in the reactor vessel trunnion 1375 to provide a contact surface for the first damping element 1376. The reactor vessel retaining pin 1390 may be an extension of the containment vessel 1324 or the containment vessel trunnion 1385, for example. In some examples, the reactor vessel retaining pin 1390 is rigidly connected to the containment vessel 1324. The reactor vessel retaining pin 1390 may extend through both sides of the containment vessel 1324. Horizontal force FH2 may be transmitted by or between the reactor vessel 1322 and the containment vessel 1324 via the reactor vessel retaining pin 1390 and the first damping element 1376. Vertical movement of the reactor vessel 1322 and containment vessel may be constrained by the interaction between the reactor vessel trunnion 1375, reactor vessel retaining pin 90, and the mounting structure 1377. Vertical movement of the reactor vessel 1322 and containment vessel 1324 may be further constrained by the interaction between the containment vessel trunnion 1385 and the mounting structure 1387. The elastic damping and retaining structure 1370 may further be configured to provide a thermal buffer for the power module 1380. In addition to attenuating, damping, or otherwise reducing dynamic and seismic forces from being transferred to or between the components of the power module 1380, the elastic damping and retaining structure 1370 may reduce the thermal heat transfer between the reactor vessel 1322 and the containment vessel 1324. For example, one or both of the first and second mounting structures 1377, 1387 may be lined with thermal insulation. FIG. 14 illustrates an example process 1400 for seismically isolating a power module. The system 1400 may be understood to operate with, but not limited by, means illustrated or described with respect to the various examples illustrated herein as FIGS. 1-13. At operation 1410, a power module is supported on a support structure. The support structure may be located at or slightly above an approximate midpoint, or an approximate center of gravity, of the power module. At operation 1420, rotation of the power module is constrained. The support structure may serve as a pivot for the rotation. At operation 1430, seismic forces transmitted through the support structure to the power module are damped or attenuated. In some examples, the seismic forces are attenuated by a damping device comprising an elastic material. At operation 1440, movement of the power module in one or more transverse directions is constrained within a fixed range of motion. Upon an attenuation of a transverse force, the power module returns to its original at-rest position. In some examples, the damping device comprises a rounded surface, and the support structure comprises a rounded recess configured to house the rounded surface. At operation 1450, movement of the power module in a longitudinal direction is constrained within a fixed range of motion. Upon an attenuation of a longitudinal force, the power module returns to its original at-rest position. The longitudinal directional is perpendicular to the one or more transverse directions of operation 1440. A number of examples related to FIGS. 1-14 have been described. Nevertheless, it will be understood that various modifications may be made. For example, the steps of the disclosed techniques may be performed in a different sequence, components in the disclosed systems may be combined in a different manner, and/or the components may be replaced or supplemented by other components. Accordingly, other implementations are within the scope of the following examples. A power module may comprise a containment vessel completely submerged in a pool of liquid, a reactor vessel housed in the containment vessel, and a support structure that comprises support arms coupled to opposed sides of the containment vessel. The pool of liquid may be disposed below a terranean surface, i.e., the pool may be subterranean. Additionally, the containment vessel may be configured to slide in a substantially lateral direction in response to a lateral force acting on the containment vessel. The support structure may be located at an approximate midpoint of the containment vessel and configured to rotate at least one of the reactor vessel or the containment vessel about an axis that extends between the support arms and through the approximate midpoint of the containment vessel. Additionally, the power module may be supported by the support structure in combination with a buoyancy force of the pool of liquid acting on the containment vessel. The support structure may comprise a first support structure disposed on a first side of the containment vessel, and the power module may further comprise a second support structure disposed on a second side of the containment vessel opposite the first side. In some examples, the support structure may be located at or slightly above the approximate center of gravity of the power module. In some examples, the support structure may comprise an elastic damping device. The support arms may be rigidly attached to the containment vessel. Additionally, the elastic damping device may be located between and in contact with one of the support arms and a mounting structure in the pool of liquid. The elastic damping device may be configured to compress in response to the support arm and the mounting structure being pressed together. Additionally, the elastic damping device may be configured to exert a reactionary force against at least one of the support arm and the mounting structure in response to the support arm and the mounting structure being pressed together In some examples, the mounting structure may be rigidly coupled to a reactor bay at least partially enclosing the pool of liquid, and the mounting structure may extend from a substantially vertical wall of the reactor bay to a location in the pool of liquid between the substantially vertical wall and the containment vessel. The support arm may comprise a hollow shaft. Additionally, the mounting structure may comprise a recess configured to receive a portion of the elastic damping device. A pivot may be located at an interface between the support structure and the mounting structure. For example, the pivot may be located at or near the elastic damping device, and the containment vessel may be configured to rotate about the pivot in response to a rotational force acting on the containment vessel. The power module may further comprise a base support or a base skirt located at a lower end of the containment vessel. The containment vessel may be configured to pivot about the support arm, and the base support may be configured to contact an alignment device in the pool of liquid if the containment vessel pivots about the support arm. The base support may be rigidly coupled to the lower end of the containment vessel around a circumference of an outer surface of the containment vessel. The alignment device may extend into the pool of liquid from a bottom surface of a reactor bay at least partially enclosing the pool of liquid, and a top portion of the alignment devices may be disposed within a volume defined by the base support. Additionally, the power module may comprise at least one dampener disposed between the top portion of the alignment device and the base support, and within the volume of the base support. The dampener may be configured to compress in response to contact between the alignment device and the base support, and the dampener may be configured exert a reactionary force against at least one of the alignment device or the base support, in response to the contact. The power module may further comprise a first damping device interposed between the reactor vessel and the containment vessel, and a second damping device interposed between the containment vessel and a pool wall. The first and second damping devices may be configured to attenuate a dynamic force and/or seismic force acting on the power module. FIG. 15 illustrates an example reactor pressure vessel (RPV) 1500 comprising a top head 1510 and a bottom head 1520 mounted on either end of a substantially cylindrical shaped body 1550. Bottom head 1520 may be removably attached to body 1550 during assembly, installation, refueling, and/or other modes of operation of RPV 1500. Bottom head 1520 may be attached to body 1550 by a bolted flange. Additionally, RPV 1500 may comprise one or more support structures 1530 located about a circumference of body 1550. In some examples, RPV 1500 comprises four support structures 1530 located at ninety degree increments around body 1550. Support structures 1530 may comprise a support member 1535 attached to RPV 1500 and one or more mounting bases 1532. Support member 1535 may be configured to extend away from body 1550 at an angle in order to provide a clearance between body 1550 and the one or more mounting bases 1532. For example, the one or mounting bases 1532 may be positioned so that they are radially located farther away from body 1550 than any other component of RPV 1500. Support structures 1530 may be configured to support RPV 1500 in a generally vertical, or longitudinal direction. In some examples, support structure 1530 may also be configured to support RPV 1500 in a generally horizontal direction, transverse direction, radial direction, and/or lateral direction. Support structure 1530 may be configured to provide a thermal “anchor” for RPV 1500. For example, during thermal expansion of RPV 1500, there may be assumed to be no thermal expansion at the portion of RPV 1500 adjacent to support structure 1530, at least in a vertical or longitudinal direction. Rather, RPV 1500 may be understood to expand in a generally longitudinal direction as a function of the distance from support structure 1530. A top head of RPV 1500 may move upwards and a bottom head of RPV 1500 may move downwards, with respect to support structure 1530. One or more radial mounts 1540 may also be mounted to body 1550. In some examples, RPV 1500 may comprise four radial mounts 1540 located at ninety degree increments around body 1550. Radial mounts 1540 may be configured to provide lateral and/or rotational support of RPV 1500. In some examples, radial mounts 1540 may be configured as radial links or lugs that project from body 1550. Radial mounts 1540 may be made operable with one or more of the seismic isolation and/or damping systems illustrated in FIGS. 1-14. FIG. 16 illustrates a partial cut-away view of an example reactor module 1650 comprising a containment vessel (CNV) 1600 and an RPV assembly, such as RPV 1500 of FIG. 15. CNV 1600 may be configured to support RPV 1500 at one or both of support structures 1530 and radial mounts 1540. CNV 1600 may comprise a platform 1630 which projects inward toward RPV 1500 and serves as a base for support structures 1530 to rest on. Support structures 1530 may be constrained in the vertical direction by platform 1630 and in the transverse or radial direction by the inner wall of CNV 1600. In other examples, a bolted interface may be used to transfer lateral loads from support structure 1530 to platform 1630. CNV 1600 may be configured to support the support structures 1530 of RPV 1500 at a steam generator plenum level of CNV 1600. CNV 1600 may comprise a top head 1610 and a bottom head 1620. In some examples, bottom head 1620 may be removably attached to CNV 1600 at a bolted flange 1640. CNV 1600 may be configured to support radial mounts 1540 of RPV 1500 near flange 1640. Radial mounts 1540 may be constrained in a longitudinal direction, a radial direction, and/or a circumferential direction within CNV 1600. Radial mounts 1540 may be configured to allow for thermal expansion between RPV 1500 and CNV 1600. In some examples, radial mounts 1540 may be horizontally pinned between RPV 1500 and CNV 1660, at the bottom half of RPV 1500. The seismic and/or dynamic loadings experienced by reactor module 1650 may result in fuel acceleration and/or fuel impact loads. Fuel accelerations in particular may be significantly decreased by the provision of supports, such as radial mounts 1540, located at or near the bottom half of RPV 1500. CNV 1600 may be configured to contain and support RPV 1500. Additionally, CNV 1600 may house a reactor cooling system, internal piping, internal valves, and other components of reactor module 1650. Support structures 1530, in combination with radial mounts 1540, may be configured within reactor module 1650 to withstand loads due to thermal transients and expansion and to support lateral loads due to seismic and other dynamic loadings. For example, reactor module 1650 may be configured to withstand and/or respond to at least two types of seismic conditions, including a Safe Shutdown Earthquake (SSE) event and an Operating Basis Earthquake (OBE) event, as previously discussed. Bottom head 1620 may comprise and/or be attached to a base support, such as a base skirt 1670. The base skirt 1670 may be rigidly mounted to, welded on, and/or form an integral part of, the CNV 1600. Base skirt 1670 may be configured to rest on the ground and/or on a lower surface of a reactor bay. In some examples, substantially all of the weight of reactor module 1650 may be supported by base skirt 1670. One or more radial mounts 1645 may be mounted to CNV 1600. In some examples, CNV 1600 may comprise four radial mounts 1645 located at ninety degree increments. Radial mounts 1645 may be configured to primarily provide lateral and/or rotational support of CNV 1600. In some examples, radial mounts 1645 may be configured as radial links or lugs that project from CNV 1600. Radial mounts 1645 may be made operable with one or more of the seismic isolation and/or damping systems illustrated in FIGS. 1-14. FIG. 17 illustrates a cross-sectional view of an example reactor module 1700 comprising an RPV 1750 and a CNV 1760. RPV 1750 may be associated with a first diameter D1 and similarly CNV 1760 may be associated with a second diameter D2 larger than first diameter D1. A bottom head 1755 of RPV 1750 may be separated or spaced apart from bottom head 1765 of CNV by a distance 1790. Distance 1790 may provide space for a thermal insulation to substantially envelop RPV 1750. In some examples, the thermal insulation may comprise a partial vacuum. The space provided by distance 1790 may further be configured to provide for thermal expansion and/or thermal transients of RPV 1750 within CNV 1760. CNV 1760 may be at least partially submerged in water, and the amount of thermal expansion of RPV 1750 may be considerably larger than that of CNV 1760 based on the differences in operating temperature. Additionally, distance 1790 may provide clearance between RPV 1750 and CNV 1760 during a seismic event to keep the vessels from contacting each other. A reactor core 1710 may be housed within RPV 1750. Reactor core 1710 may be spaced apart from RPV 1750 by a distance 1720. The space formed by distance 1720 may be configured to promote circulation of coolant within RPV 1750 to pass through reactor core 1710. Additionally, distance 1720 may provide clearance between RPV 1750 and reactor core 1710 during a dynamic event or a seismic event or to account for thermal expansion and/or thermal transients. During a seismic event, seismic forces generated from within the ground 1775 and/or from below a support surface 1740, such as a floor of a surrounding containment building, may be transmitted to a base support, such as a base skirt 1770 of CNV 1760. The seismic forces may follow up through the container wall of CNV 1760 through a transmission path 1705 which may be transferred to RPV 1750 via one or more points of attachment, such as support structures 1530 and/or radial mounts 1540 (FIG. 15). Transmission path 1705 may represent at least a portion of an overall example path through which the seismic forces are transmitted, beginning with the source of the seismic forces and ultimately continuing on to the fuel assemblies located within RPV 1750. Other components may experience different example transmission paths. A bottom surface 1730 of CNV 1760 may be located some distance above the ground 1775 and/or support surface 1740. In some examples, the space located between CNV 1760 and the support surface 1740 may provide room for surrounding water to cool the exterior surface of CNV 1760. FIG. 18 illustrates an example system 1800 comprising seismic attenuation devices configured as radial keys 1840. Radial keys 1840 may comprise one or more posts that extend outwardly from an RPV 1850 about its radius and engage one or more brackets, such as a first bracket 1810 and a second bracket 1820. The brackets may extend inwardly from a surrounding CNV 1860. Radial keys 1840 may be located at or near a bottom head 1855 of RPV 1850. Each of the radial keys 1840 may be inserted between a pair of brackets, such as first bracket 1810 and second bracket 1820. The brackets may be located at or near a bottom head 1865 of CNV 1860. In some examples, three or more radial keys may be spaced about the circumference of RPV 1850 to engage a corresponding number of bracket pairs located within the periphery of CNV 1860. Radial keys 1840 may be configured to stabilize, dampen, attenuate, reduce, or otherwise mitigate any dynamic or seismic force experienced by RPV 1850. During a seismic event, radial keys 1840 may be configured to contact one or both of first bracket 1810 and second bracket 1820, to limit or prohibit movement/rotation of RPV 1850 in a circumferential direction 1830. Contact with one or more of the brackets may also impart friction force to resist or dampen movement of RPV 1650 in a transverse or radial direction 1880, e.g., towards the inner wall of CNV 1860. In some examples, the inner wall of CNV 1860 may inhibit the movement of RPV 1850 in the radial direction 1880. A base support, such as a base skirt 1870 attached to the bottom of CNV 1860, may be configured to support the weight of the reactor module comprising CNV 1860 and RPV 850. During a seismic event, seismic forces may be transmitted from base skirt 1870 up through the container wall of CNV 1860 through a transmission path 1805 which may transfer the seismic forces to the radial keys 1840 of RPV 1850 via the one or more brackets, such as first bracket 1810 and/or second bracket 1820. Transmission path 1805 may represent at least a portion of an overall example path through which the seismic forces are transmitted, beginning with the source of the seismic forces and ultimately continuing on to the fuel assemblies located within RPV 1850. By transmitting seismic forces to the RPV 1850 near the bottom head, transmission path 1805 may be considerably shorter than transmission path 1705 (FIG. 17). In some examples, decreasing the transmission path may result in a smaller amount of dynamic and/or seismic force that would otherwise be imparted to RPV 1750 and to any internal components, such as the reactor core and/or fuel rods. The amplitude and/or size of the dynamic/seismic forces may be amplified as a function of the length of the transmission path as the forces are transmitted from the ground or support surface to an RPV via one or more intermediate structures. FIG. 19 illustrates an example system 1900 comprising seismic attenuation devices configured as radial bumpers 1910. Radial bumpers 1910 may extend from an inner wall of a CNV 1960. A base support, such as a base skirt 1970 attached to the bottom of CNV 1960, may be configured to support the weight of the reactor module comprising CNV 1960. Radial bumpers 1910 may be attached to CNV 1960 at or near a bottom head 1920 of CNV 1960. In some examples, radial bumpers 1910 may be attached to a cylindrical wall 1950 of CNV 1960 located above base skirt 1970. FIG. 20 illustrates the example system 1900 of FIG. 19 together with an RPV 2050. Radial bumpers 1910 may be configured to stabilize, dampen, attenuate, reduce, or otherwise mitigate any dynamic or seismic force experienced by RPV 1950. During a seismic event, radial bumpers 1910 may be configured to contact the outer surface of RPV 1950, and to limit or prohibit movement of RPV 1950 in a transverse or radial direction. Contact with one or more of the bumpers 1910 may also impart friction force to resist or dampen movement/rotation of RPV 1950 in a circumferential direction. During a seismic event, seismic forces may be transmitted from base skirt 1970 up through the container wall of CNV 1960 through a transmission path 2005 which may transfer the seismic forces to RPV 2050 via the one of more radial bumpers 1910. In some examples, radial bumpers 1910 and/or radial keys 1840 (FIG. 18) may be configured to operate with and/or to comprise one or more of the seismic isolation and/or damping systems illustrated in one or more of FIGS. 1-14. FIG. 21 illustrates an example system 2100 comprising a seismic attenuation device configured as a vertical key 2155. In some examples, vertical key 2155 may be configured as a round or conical post located on the bottom head 2110 of an RPV 2150. Vertical key 2155 may be configured to fit into a recess 2165 located at the bottom head 2120 of a CNV 2160. Recess 2165 may comprise a round hole sized to receive vertical key 2155. Vertical key 2155 may be configured to provide lateral support of RPV 2150 in a transverse or radial direction 2135. Additionally, a gap 2130 may be provided between vertical key 2155 and recess 2165 to allow for thermal expansion of RPV 2150 in a longitudinal direction 2115. In some examples, gap 2130 may be approximately four to six inches in the longitudinal direction. During thermal expansion of RPV 2150, a larger portion of vertical key 2155 may be inserted into recess 2165, and effectively decrease gap 2130 by two or more inches. In some examples, RPV 2150 may expand due to an increase in internal pressure. Vertical key 2155 may remain at least partially inserted within recess 2165 when RPV 150 is at ambient temperature, e.g., at some nominal operation condition or at a minimum amount of thermal expansion. The diameter associated with vertical key 2155 may be sufficiently less than the diameter of recess 2165 to provide for a clearance and/or tolerance during fit-up. In some examples, the diameter of vertical key 2155 may be between one and two feet and the clearance between vertical key 2155 and a contact point 2125 within recess 2165 may be approximately one eighth of an inch, one sixteenth of an inch, or less. In still other examples, the relative diameters may be only slightly different such that vertical key 2155 may be pressure-fit into recess 2165 with virtually no clearance. The reactor module assembly may experience varying differential thermal growth depending if the reactor module is in shut down (i.e., cold) operating conditions, or in full power (i.e., hot) operating conditions. Accordingly, one or more of the seismic attenuation devices described above may be configured to stabilize, dampen, attenuate, reduce, or otherwise mitigate any dynamic or seismic force experienced by the RPV and/or the reactor core in both the hot and cold operating conditions. A radial gap and/or spacing between the one or more seismic attenuation devices and the adjacent vessel surface may be provided to accommodate the differential radial growth. In some examples, the radial gap between vertical key 2155 and contact point 2125 may be provided to allow for thermal expansion of vertical key 2155 in the radial direction 2135. The distance of the radial gap may vary according to the diameter of the vertical key. Vertical key 2155 may be inserted and/or removed from recess 2165 during assembly, installation, refueling, and/or other modes of operation. The system 2100 illustrated in FIG. 21 may be configured to assemble RPV 2150 together with CNV 2160 independently of circumferential alignment. For example, vertical key 2155 may be configured to be installed into recess 2165 regardless of the rotational orientation of RPV 2150. Additionally, the lower corner(s) of vertical key 2155 may be tapered to facilitate alignment and/or entry into recess 2165. Vertical key 2155 may be configured to stabilize, dampen, attenuate, reduce, or otherwise mitigate any dynamic or seismic force experienced by RPV 2150. During a seismic event, vertical key 2155 may be configured to contact recess 2165 at one or more lateral contact points 2125, to limit or prohibit movement/rotation of RPV 2150 in the radial direction 2135. In some examples, contact between vertical key 2155 and recess 2165 may also impart friction force to resist rotational movement of RPV 2150 within CNV 2160 and/or to resist vertical movement of RPV 2150 in the longitudinal direction 2115. A base support, such as a base skirt 2170 attached to the bottom of CNV 2160, may be configured to support the weight of the reactor module comprising CNV 2160 and RPV 2150. During a seismic event, seismic forces may be transmitted from base skirt 2170 through a transmission path 2105 which may transfer the seismic forces to the vertical key 2155 of RPV 2150 via the one or more lateral contact points 2125 within recess 2165. Vertical key 2155 may extend downward from the RPV 2150 at the longitudinal centerline of the bottom head 2110. The bottom head 2120 of CNV 2160 may be reinforced, such as by adding material or increasing the thickness of the wall of bottom head 2120. In some examples, recess 2165 may be machined out of the inner surface of the bottom head 2120 of CNV 2160. Locating a seismic attenuation device, such as vertical key 2155, at the bottom head 2110 of RPV 2150 may significantly reduce the seismic acceleration and impact load on the fuel assemblies (e.g. by six times or more) as compared to using radial mounts 1540 as illustrated in FIG. 15. A relatively shorter transmission path may effectively eliminate or lower the transmissibility of forces as compared to a transmission path which passes through one or more sub-systems that are located between the source (ground motion) and the fuel assemblies. In some examples, vertical key 2155 may be forged as an integral part of the bottom head 2110 of RPV 2150. In examples where vertical key 2155 is attached, e.g., welded, to bottom head 2110, vertical key 2155 may be made out of the same material as bottom head 2110. For example, RPV 2150, bottom head 2110, and/or vertical key 2155 may be made from SA-508, Grade 3, Class 1 steel forgings or other suitable materials. A suction line 2190 may be configured to remove fluid located within recess 2165. In some examples, an annular space 2175 between RPV 2150 and CNV 2160 may be evacuated during operation of the reactor module. The removal of fluid and/or gases through suction line 2190 may facilitate creating and/or maintaining an evacuation chamber which substantially surrounds RPV 2150. FIG. 22 illustrates a further example system 2200 comprising a seismic attenuation device configured as a vertical key or post 2265. In some examples, vertical key 2265 may be configured as a round or conical post located on the bottom head 2220 of a CNV 2260. Vertical key 2265 may be configured to fit into a recess 2255 located at the bottom head 2210 of an adjacent RPV 2250. Recess 2255 may comprise a round hole sized to receive vertical key 2265. Vertical key 2265 may be configured to provide lateral support of RPV 2250 in a transverse or radial direction 2235. Additionally, a gap 2230 may be provided between vertical key 2265 and recess 2255 to allow for thermal expansion of RPV 2250 in a longitudinal direction 2215. The diameter associated with vertical key 2265 may be sufficiently less than the diameter of recess 2255 to provide for a clearance and/or tolerance during fit-up. In some examples, the clearance may be approximately one sixteenth of an inch or less. In still other examples, the relative diameters may be only slightly different such that vertical key 2265 may be pressure-fit into recess 2255 with virtually no clearance. Vertical key 2265 may be inserted and/or removed from recess 2255 during assembly, installation, refueling, and/or other modes of operation. The system 2200 illustrated in FIG. 22 may be configured to assemble RPV 2250 together with CNV 2260 independently of circumferential alignment. For example, vertical key 2265 may be configured to be installed into recess 2255 regardless of the rotational orientation of RPV 2250. Additionally, the lower corner(s) of vertical key 2265 may be tapered to facilitate alignment and/or entry into recess 2255. Vertical key 2265 may be configured to stabilize, dampen, attenuate, reduce, or otherwise mitigate any dynamic or seismic force experienced by RPV 2250. During a seismic event, vertical key 2265 may be configured to contact recess 2255 at one or more lateral contact points 2225, to limit or prohibit movement/rotation of RPV 2250 in the radial direction 2235. In some examples, contact between vertical key 2265 and recess 2255 may also impart friction force to resist rotational movement of RPV 2250 within CNV 2260 and/or to resist vertical movement of RPV 2250 in the longitudinal direction 2215. Vertical key 2230 may extend upward from CNV 2260 at a longitudinal centerline 2290 of the bottom head 2220. The bottom head 2210 of RPV 2250 may be reinforced, such as by adding material or increasing the thickness of the wall of bottom head 2210. In some examples, recess 2255 may be machined out of the outer surface of the bottom head 2220 of RPV 2250. A base support, such as a base skirt 2270 attached to the bottom of CNV 2260, may be configured to support the weight of the reactor module comprising CNV 2260 and RPV 2250. During a seismic event, seismic forces may be transmitted from base skirt 2270 through bottom head 2220 to RPV 2250 via the transmission of forces from vertical key 2230 to one or more lateral contact points 2225 within recess 2255. Base skirt 2270 may rest on a floor 2240 comprising reinforced concrete. Additionally, base skirt 2270 may comprise an annular shaped structure connected to the circumference of bottom head 2220. Base skirt 2270 may be configured to be placed next to one or more stops 2280. In some examples, the one or more stops 2280 may comprise an annular ring-shaped structure attached to the floor 2240. The one or more stops 2280 may be configured to align RPV 2250 when it is placed on the floor 2240. Additionally, the one or more stops 2280 may be configured to restrict and/or prohibit lateral movement of CNV 2260 in the radial direction 2235. The bottom head 2220 of CNV 2260 may be located some distance 2245 above the floor 2240 upon which base skirt 2270 is placed on. In some examples, distance 2245 may be between six inches and one foot. The space located between CNV 2260 and the floor 2240 may provide room for surrounding water to cool the exterior surface of CNV 2260. Additionally, base skirt 2270 may comprise one or more through holes 2275 to allow the water to enter the space within base skirt 2270 in order to cool bottom head 2220. In some examples, vertical key 2265 may be forged as an integral part of the bottom head 2220 of CNV 2260. In examples where vertical key 2265 is attached, e.g., welded, to bottom head 2220, vertical key 2265 may be made out of the same material as bottom head 2220. For example, CNV 2260, bottom head 2220, and/or vertical key 2255 may be made from SA-508, Grade 3, Class 1 steel forgings, or other suitable materials. Providing radial spacing and/or clearance about vertical key 2265 may provide for some slight lateral movement of RPV 2250 within CNV 2260 to provide a flexible, or non-rigid stability system. While RPV 2250 may be allowed to move, it may nevertheless be constrained by recess 2255 to limit the amount of lateral movement. A flexible stability system may impart and/or transmit less force than a rigidly connected system. One or more of the a seismic attenuation devices described above may be configured to stabilize, dampen, attenuate, reduce, or otherwise mitigate any dynamic or seismic forces, such as in the lateral or radial direction, without restraining the differential thermal growth between the RPV and the CNV. For example, the thermal growth of the RPV, such as RPV 2250, may be based on a temperature change between ambient conditions and the design temperature of the reactor module, which in some examples may be approximately 650° F. On the other hand, the thermal growth of the CNV, such as CNV 2260 may be essentially non-existent when the CNV is submerged in, or at least partially surrounded by, a pool of water that is near ambient temperature. By attaching vertical key 2265 to CNV 2260, the thermal expansion of RPV 2250 may result in the internal diameter of recess 2230 increasing, whereas the external diameter of vertical key 2265 may remain essentially constant, independent of operating temperatures within RPV 2250. Accordingly, the lateral clearance between vertical key 2265 and recess 2230 could be made just large enough to facilitate assembly and/or fit-up, but would not necessarily need to account for thermal expansion of RPV 2250 and/or vertical key 2265 in the radial direction 2235. In some examples, RPV 2250 and CNV 2260 may be considered essentially thermally isolated from each other, regardless of any incidental contact between vertical key 2265 and recess 2230. FIG. 23 illustrates an example system 2300 comprising a seismic attenuation device configured as a vertical key or post 2365 with an alternative force transmission path 2305. During a seismic event, seismic forces may be transmitted from one or more stops 2380 and/or the ground 2305 to a base support such as a base skirt 2370. Laterally transmitted forces from the one or more stops 2305 to base skirt 2370 may travel through transmission path 2305 and continue along a bottom head 2320 of a CNV 2360 before being transferred to RPV 2250 via the one or more lateral contact points 2325 between recess 2255 of RPV 2250 and the radial surface of vertical key 2365. By locating base skirt 2370 closer to a longitudinal centerline 2390 of RPV 2250 and/or CNV 2360, where vertical key 2365 and or recess 2255 may be aligned, the transmission path 2305 between the one or more stops 2380 and RPV 2250 may be made shorter as compared to a transmission path associated with system 2200 (FIG. 22). FIG. 24 illustrates a further example system 2400 comprising a seismic attenuation device configured as a vertical key or post 2465 with an alternative force transmission path 2405. During a seismic event, lateral forces may be transmitted from one or more stops 2470 to a base support such as a base skirt 2470. Transmission path 2405 may continue from base skirt 2470 in a substantially linear direction both through a bottom head 2420 of CNV 2460 and through vertical key 2465 before being transferred to RPV 2250 via the one or more lateral contact points 2425 between recess 2255 of RPV 2250 and the radial surface of vertical key 2465. By locating base skirt 2470 closer to a longitudinal centerline 2490 of RPV 2250 and/or CNV 2460, the transmission path 2405 associated with system 2400 may be made shorter as compared to the transmission path 2305 associated with system 2300 (FIG. 23). In some examples, base skirt 2470 may be located directly below at least a portion of radial key 2465. In other examples, base skirt 2470 may be located directly below at least a portion of recess 2255. Transmission path 2405 may be understood to provide an essentially direct, linear path from the ground, or support surface, to RPV 2250. In some examples, recess 2255 may be formed in a boss 2450 which extends from bottom head 2210 into the interior of RPV 2250. Boss 2450 may comprise one or more curved or sloped surfaces 2252 which are configured to direct coolant flow 2256 in an upward direction to facilitate uniform mass flow distribution of coolant entering the reactor core. In some examples, boss 2450 may be configured to direct at least a portion of coolant flow 2256 to a periphery of the reactor core. FIG. 25 illustrates an example system 2500 comprising a seismic attenuation device configured as an integrated vertical key 2565 and lateral support 2575. Vertical key 2565 may extend upward in a substantially vertical direction from the inner surface of a CNV 2560 into the adjacent recess 2255 of RPV 2250 contained within CNV 2560. Lateral support 2575 may extend downward in a substantially vertical direction from the outer surface of CNV 2560 towards a support surface 2540. In some examples, both vertical key 2565 and lateral support 2575 may be vertically aligned along a longitudinal centerline 2590 of one of both of CNV 2560 and RPV 2250. The weight of RPV 2250 may be primarily supported by a base support such as base skirt 2570, similar to base skirt 1970 of FIG. 19. System 2500 may comprise a force transmission path 2505. During a seismic event, lateral forces may be transmitted from one or more stops 2580 to lateral support 2575. Transmission path 2505 may continue from lateral support 2575 in a substantially linear direction both through a bottom head 2520 of CNV 2560 and through vertical key 2565 before being transferred to RPV 2250 via one or more lateral contact points between recess 2255 of RPV 2250 and a radial surface of vertical key 2565. In some examples, lateral support 2575 may be located directly below at least a portion of radial key 2565 and/or recess 2255. Transmission path 2505 may be understood to provide an essentially direct, linear path from support surface 2540 to RPV 2250. Lateral support 2575 may be configured to contact the one or more stops 2580 without directly contacting support surface 2540. In some examples, neither vertical key 2565 nor lateral support 2575 are configured to support any of the weight of RPV 2250 or CNV 2560. FIG. 26 illustrates an example system 2600 comprising an attenuation device configured as a vertical key 2680 having a conical shaped surface 2685. Key 2680 may be configured to fit within a recess 2670 having a complimentary shaped conical inner surface 2675. The sloped or angled contour of conical surfaces 2675, 2685 may provide for a lateral clearance 2690 between key 2680 and recess 2670. Additionally, the conical surfaces 2675, 2685 may facilitate fit-up and/or assembly of a reactor module comprising an RPV 2650 and a surrounding CNV 2660. In some examples, FIG. 26 may be considered as illustrating a reactor module comprising RPV 2650 and/or CNV 2660 in a nominal or non-expanded state. FIG. 27 illustrates an enlarged partial view of the example system 2600 of FIG. 26 with RPV 2650 undergoing thermal expansion. The thermally expanding RPV 2750 is shown in dashed lines, indicating thermal expansion in both a longitudinal direction and radial direction. For example, a first length 2710 associated with RPV 2650 may increase to a second length 2720 associated with thermally expanding RPV 2750. Similarly, RPV 2650 may expand in the radial direction as illustrated by the enlarged diameter 2730 associated with a thermally expanded recess 2770 including an enlarged conical shaped surface 2775. FIG. 28 illustrates an enlarged partial view of the example system 2600 of FIG. 26 in an expanded state. The sloped or angled contour of conical surfaces 2685, 2775 may provide for a lateral clearance 2890 between key 2680 of CNV 2660 and thermally expanded recess 2770. The lateral clearance 2890 associated with a thermally expanded RPV 2750 may be approximately equal to the lateral clearance 2690 associated with RPV 2650 (FIG. 26) in the nominal or non-expanded state. In some examples, lateral clearance 2890 may be approximately one sixteenth of an inch or less. In other examples, lateral clearance 2890 may be approximately one eighth of an inch or less. Other and/or larger dimensions are also contemplated herein. Maintaining a lateral clearance at less than some predetermined dimension may effectively make any lateral movement between key 2680 and recess 2670 negligible with respect to determining dynamic impact forces between RPV 2650 and CNV 2660. FIG. 29 illustrates a further example system 2900 comprising an attenuation device configured as a conical shaped key 2980 having a conical shaped surface 2985. Key 2980 may be configured to fit within a recess 2970 having a complimentary shaped conical inner surface 2975. Key 2980 may extend downward in a substantially vertical direction from the outer surface of an RPV 2950 into the adjacent recess 2970 of a surrounding CNV 2960. The sloped or angled contour of conical surfaces 2975, 2985 may provide for a lateral clearance 2990 between key 2980 and recess 2970. Additionally, the conical surfaces 2975, 2985 may facilitate fit-up and/or assembly of a reactor module comprising RPV 2950 and CNV 2960. FIG. 30 illustrates an example operation 3000 for transmitting dynamic or seismic forces through a reactor module structure. The reactor module structure may comprise a containment vessel that houses a reactor pressure vessel. The reactor vessel may be spaced apart from the containment vessel by an annular containment volume. In some examples, the annular containment volume may be evacuated to provide thermal insulation between the containment vessel and the reactor pressure vessel. At operation 3010, some or substantially all of the weight of the reactor pressure vessel within the containment vessel may be supported by a support structure. The support structure may pass through the annular containment volume. At operation 3020, a seismic force may be transmitted to the containment vessel. The containment vessel may be supported by a base support located near a bottom head of the containment vessel. In some examples, the base support may comprise a base skirt. At operation 3030, the seismic force that is received by the reactor pressure vessel may be attenuated by an attenuation device. In some examples, the attenuation device may not be configured to support any of the weight of the reactor pressure vessel. The attenuation device may pass through the annular containment volume. In some examples, the attenuation device may be located along a longitudinal centerline of the reactor pressure vessel and/or a longitudinal centerline of the containment vessel. The attenuation device may be configured to attenuate the seismic force in a direction transverse to the longitudinal centerline(s). Additionally, the attenuation device may form part of a seismic force attenuation path which transfers the seismic force from the containment vessel to the reactor pressure vessel. The seismic force attenuation path may comprise a vertical portion that passes through a base support located near the bottom head of the containment vessel. The attenuation device may be configured to attenuate the seismic force in direction that is substantially transverse to the vertical portion of the seismic force attenuation path. FIG. 31 illustrates an example system 3100 comprising an attenuation device configured as a stair-step shaped key 3180. Key 3180 may be configured to fit within a recess 3170 having a complimentary shaped stair-step inner surface. Key 3180 may extend upward in a substantially vertical direction from the inner surface of a CNV 3160 into the adjacent recess 3170 of an RPV 3150. The stair-step shape of key 3180 may comprise a first step 3182 having a first diameter and a second larger step 3184 having a second diameter. In some examples, FIG. 31 may be considered as illustrating a reactor module comprising RPV 3150 and/or CNV 3160 in a nominal or non-expanded state, in which a lateral clearance is provided between first step 3182 and recess 3170. FIG. 32 illustrates an enlarged partial view of the example system 3100 of FIG. 31 with RPV 3150 in an enlarged or expanded state. A lateral clearance 3250 between key 3180 and recess 3170 in the expanded state may be approximately equal to the lateral clearance associated with RPV 3150 in the nominal or non-expanded state, as illustrated in FIG. 31. Although at least some of the examples provided herein have primarily described a pressurized water reactor and/or a light water reactor, it should be apparent to one skilled in the art that the examples may be applied to other types of power systems. For example, one or more of the examples or variations thereof may also be made operable with a boiling water reactor, sodium liquid metal reactor, gas cooled reactor, pebble-bed reactor, and/or other types of reactor designs. It should be noted that examples are not limited to any particular type of fuel employed to produce heat within or associated with a nuclear reaction. Any rates and values described herein are provided by way of example only. Other rates and values may be determined through experimentation such as by construction of full scale or scaled models of a nuclear reactor system. Having described and illustrated various examples herein, it should be apparent that other examples may be modified in arrangement and detail. We claim all modifications and variations coming within the spirit and scope of the following claims.
	description	The present invention relates to a particle beam therapy system used for medical use or research use, and in particular, relates to a particle beam therapy system which can transport a beam to a plurality of treatment rooms as if simultaneously by time-sharing. Heretofore, among particle beam therapy systems, there have been reported those with the presence of a plurality of treatment rooms. In such conventional particle beam therapy systems, beam paths are each configured to guide a beam to selected one of the treatment rooms by way of electromagnets of a beam transport system referred to as an HEBT (High Energy Beam Transport) system. Thus, it is basically unable to perform treatment simultaneously in the plurality of treatment rooms. Meanwhile, it is general to perform switching of the beam path by use of a bending magnet. In Patent Document 1, there is described a particle beam therapy system that, for the purpose of improving throughput of the treatment in the case with the presence of a plurality of treatment rooms, performs treatment as if simultaneously in the plurality of treatment rooms, exceptionally by shifting respiratory phases of the patients in the respective treatment rooms from each other by way of respiratory navigation (breathing guidance). Patent Document 1: International Patent Publication No. WO2012/032632A1 (Paragraph 0036 to Paragraph 0038, FIG. 1) According to the particle beam therapy system of Patent Document 1, it is able to perform treatment as if simultaneously in the plurality of treatment rooms byway of respiratory navigation; however, because of the assumption that respiratory navigation has to be applied, it is unable to meet a demand for performing treatment simultaneously in the plurality of treatment rooms without using respiratory navigation. This invention has been made to solve the problem as described above, and an object thereof is to provide a particle beam therapy system which can transport a beam to a plurality of treatment rooms as if simultaneously by time-sharing, even without using respiratory navigation. A particle beam therapy system of the invention comprises: a plurality of treatment rooms; a plurality of particle beam irradiation apparatuses placed respectively in the plurality of treatment rooms; an accelerator that accelerates a charged particle beam; a beam transport system that transports the charged particle beam accelerated by the accelerator to the plurality of particle beam irradiation apparatuses; and a treatment management device that controls the accelerator, the beam transport system and the plurality of particle beam irradiation apparatuses. It is characterized in that: the beam transport system includes a beam-path changer for changing a beam path so as to transport the charged particle beam to any one of the plurality of particle beam irradiation apparatuses; the treatment management device includes a beam-path controller that generates an emitter control signal for controlling an emitter of the accelerator and a beam-path changer control signal for controlling the beam-path changer so that, with respect to the plurality of particle beam irradiation apparatuses in which treatment is performed at a same treatment period of time, the charged particle beam is transported to each one of the plurality of particle beam irradiation apparatuses for each time period allocated thereto. And it is characterized in that with respect to a plurality of respiration gate signals for permitting radiation of the charged particle beam that are generated, from individual monitoring of respiratory states of a plurality of patients to be irradiated with the charged particle beam by the plurality of particle beam irradiation apparatuses, respectively for the plurality of patients, when at least two of them become simultaneously “ON”, the beam-path controller generates the emitter control signal and the beam-path changer control signal so that the charged particle beam is transported, without depending on the plurality of respiratory gate signals, to the particle beam irradiation apparatus in the treatment room designated by a time-sharing signal for cyclically selecting each one of the plurality of particle beam irradiation apparatuses, on the basis of the plurality of respiratory gate signals and the time-sharing signal. According to the particle beam therapy system of the invention, the beam-path changer of the beam transport system and the emitter of the accelerator are controlled based on the plurality of respiratory gate signals and the time-sharing signal so that, with respect to the plurality of particle beam irradiation apparatuses in which treatment is performed at the same treatment period of time, the charged particle beam is transported to each one of the plurality of particle beam irradiation apparatuses for each time period allocated thereto. Thus, it is possible to transport the beam to the plurality of treatment rooms as if simultaneously by time-sharing, even without using respiratory navigation. FIG. 1 is a configuration diagram showing a particle beam therapy system according to Embodiment 1 of the invention. FIG. 2 is a schematic configuration diagram of a particle beam irradiation apparatus in FIG. 1. A particle beam therapy system 51 includes a beam generation apparatus 52, a beam transport system 59 and a plurality of particle beam irradiation apparatuses 58a, 58b. The particle beam irradiation apparatus 58b is placed in a rotary gantry (not shown) provided in a treatment room 29b. The particle beam irradiation apparatus 58a is placed in a treatment room 29a including no rotary gantry. Note that, in FIG. 1, for simplification's sake, description will be made assuming that the number of treatment rooms is two; however, this does not mean that the number of treatment rooms is limited to two in the invention. The beam generation apparatus 52 includes an ion source 56, a linear accelerator 53 and a circular accelerator (hereinafter, referred to simply as “accelerator”) 54 that is a synchrotron. The role of the beam transport system 59 is to communicate between the accelerator 54 and the particle beam irradiation apparatuses 58a, 58b. The beam transport system 59 includes: a beam-path changer 16 for changing a beam path directed toward each of the particle beam irradiation apparatuses 58a, 58b, of a charged particle beam 81 (see, FIG. 2) emitted from an emitter 62 of the accelerator 54; an upstream beam-transport system 23 that is from the emitter 62 of the accelerator 54 up to the beam-path changer 16; a downstream beam-transport system 24a that is from the beam-path changer 16 up to the particle beam irradiation apparatus 58a; and a downstream beam-transport system 24b that is from the beam-path changer 16 up to the particle beam irradiation apparatus 58b. The downstream beam-transport system 24b is partly placed in the rotary gantry (not shown) and includes, at that part, a plurality of bending magnets 55a, 55b and 55c. The beam generation apparatus 52, the beam transport system 59 and the particle beam irradiation apparatuses 58a, 58b are controlled in their cooperative manner by a treatment management device 95. The charged particle beam 81 that is a particle beam, such as a proton beam, a carbon beam (heavy particle beam), etc., generated by the ion source 56, is accelerated by the linear accelerator 53 and entered into the accelerator 54 through an injector 61. The charged particle beam 81 is accelerated up to a given energy. In the accelerator 54, it is accelerated by a high-frequency electric field up to approx. 70 to 80% of the light velocity while being bent by magnets. The charged particle beam 81 emitted from the emitter 62 of the accelerator 54 is transported through the beam transport system 59 to the particle beam irradiation apparatuses 58a, 58b. In the beam transport system 59, the charged particle beam 81 having been sufficiently given with energy is guided to the particle beam irradiation apparatus 58a or 58b in the designated treatment room, through a passage formed of vacuum ducts (a main duct 20, a downstream duct 22a, a downstream duct 22b) in such a manner that its trajectory is changed as necessary by a plurality of bending magnets 12a to 12h. The particle beam irradiation apparatus 58a or 58b, while forming an irradiation field according to the size and depth of an diseased site that is an irradiation target 31 of a patient 30, radiates the charged particle beam 81 to the irradiation target 31 (see, FIG. 2). The charged particle beam 81 accelerated by the linear accelerator 53 is guided, while changing its trajectory by bending magnets 12i, 12j, to the injector 61 of the accelerator 54. The downstream duct 22a branched from the main duct 20 is connected to the particle beam irradiation apparatus 58a, and the downstream duct 22b branched from the main duct 20 is connected to the particle beam irradiation apparatus 58b. A portion indicated by a broken line circle is a duct branching section 21 in which the downstream ducts 22a, 22b are branched from the main duct 20. Here, as is stated as “the designated treatment room”, a particle beam therapy system generally includes a plurality of treatment rooms as described previously, from a viewpoint of treatment efficiency. Namely, it is necessary to provide the particle beam irradiation apparatuses 58 as many as the number of the treatment rooms. Generally, a large and complex system formed of such a plurality of sub-systems comprises sub-control devices for exclusively controlling the respective sub-systems and a main control device for supervising and controlling the entire system, in many cases. With respect also to the particle beam therapy system 51 shown in Embodiment 1 of the invention, description will be made citing a case where a configuration with a main control device and sub-control devices is applied. For simplification's sake, here, a sub-system including the beam generation apparatus 52 and the beam transport system 59 will be totally referred to as an acceleration system. The particle beam irradiation apparatus 58, or the particle beam irradiation apparatus 58 and the rotary gantry will be referred to as an irradiation system. The treatment management device 95 includes a main management device 120 for controlling the whole of the particle beam therapy system 51, an accelerator-system control device 121 for controlling the accelerator system, an irradiation management device 88a for controlling the particle beam irradiation apparatus 58a, and an irradiation management device 88b for controlling the particle beam irradiation apparatus 58b. The accelerator-system control device 121 includes a beam-path controller 18 for controlling the emitter 62 and the beam-path changer 16. On a treatment table 25a in the treatment room 29a, a patient 30a is laid. In the treatment room 29a, there is placed a respiratory signal generator 26a for detecting a respiratory state of the patient 30a using a patient sensor 27a to thereby generate a respiratory signal psig1. On a treatment table 25b in the treatment room 29b, a patient 30b is laid. In the treatment room 29b, there is placed a respiratory signal generator 26b for detecting a respiratory state of the patient 30b using a patient sensor 27b to thereby generate a respiratory signal psig2. The diseased site of the patient 30a is an irradiation target 31a, and the diseased site of the patient 30b is an irradiation target 31b. For the particle beam irradiation apparatuses, numeral 58 is used collectively, and numerals 58a, 58b are used when they are to be described distinctively. With respect to the treatment rooms, the treatment tables, the patients, the irradiation targets, the patient sensors and the respiratory signal generators, numerals 29, 25, 30, 31, 27 and 26 are collectively used, respectively, and these numerals are each used as being suffixed with “a” or “b” when its corresponding objects are to be described distinctively. In FIG. 2, the particle beam irradiation apparatus 58 includes: an X-direction scanning electromagnet 82 and a Y-direction scanning electromagnet 83 which scan the charged particle beam 81, respectively in an X-direction and a Y-direction that are directions perpendicular to the charged particle beam 81; a position monitor 84; a dose monitor 85; a dose-data converter 86; a beam-data processing device 91; and a scanning-electromagnet power source 87. The irradiation management device 88 for controlling particle beam irradiation apparatus 58 in the treatment management device 95 includes an irradiation control computer 89 and an irradiation control device 90. The dose-data converter 86 includes a trigger generator 92, a spot counter 93 and an inter-spot counter 94. Note that in FIG. 2, the travelling direction of the charged particle beam 81 is a direction of −Z. The X-direction scanning electromagnet 82 is a scanning electromagnet for scanning the charged particle beam 81 in the X-direction, and the Y-direction scanning electromagnet 83 is a scanning electromagnet for scanning the charged particle beam 81 in the Y-direction. With respect to the charged particle beam 81 scanned by the X-direction scanning electromagnet 82 and the Y-direction scanning electromagnet 83, the position monitor 84 detects beam information for calculating a passing position (gravity center position) and a size of the beam that passes therethrough. The beam-data processing device 91 calculates the passing position (gravity center position) and the size of the charged particle beam 81 on the basis of the beam information that comprises a plurality of analog signals detected by the position monitor 84. Further, the beam-data processing device 91 generates an abnormality detection signal indicative of a position abnormality and/or a size abnormality of the charged particle beam 81, and outputs the abnormality detection signal to the irradiation management device 88. The dose monitor 85 detects the dose of the charged particle beam 81. The irradiation management device 88 controls the irradiation position of the charged particle beam 81 in the irradiation target 31 of the patient 30 on the basis of treatment plan data prepared by an unshown treatment plan device, and moves the charged particle beam 81 to a next irradiation position when the dose having been measured by the dose monitor 85 and converted by the dose-data converter 86 into digital data, reaches a desired dose. The scanning-electromagnet power source 87 changes setup currents for the X-direction scanning electromagnet 82 and the Y-direction scanning electromagnet 83 on the basis of control inputs (commands) outputted from the irradiation management device 88 for the X-direction scanning electromagnet 82 and the Y-direction scanning electromagnet 83. Here, the scanning irradiation method of the particle beam irradiation apparatus 58 is assumed to be a raster-scanning irradiation method in which the charged particle beam 81 is not stopped when the irradiation position of the charged particle beam 81 is changed, and in which the beam irradiation position moves between spot positions successively like a spot-scanning irradiation method. The spot counter 93 serves to measure an irradiation dose during when the beam irradiation position of the charged particle beam 81 is staying. The inter-spot counter 94 serves to measure an irradiation dose during when the beam irradiation position of the charged particle beam 81 is moving. The trigger generator 92 serves to generate a dose completion signal when the dose of the charged particle beam 81 at a beam irradiation position reaches the desired irradiation dose. The abstract of beam-path switching in the particle beam therapy system 51 of Embodiment 1 will be described in comparison with the particle beam therapy system of Patent Document 1 (Comparative Example). FIG. 3 is a schematic diagram illustrating a main part in the beam transport system in FIG. 1, and FIG. 4 is a schematic diagram illustrating a main part in a beam transport system in Comparative Example. In Comparative Example, switching is made using a bending magnet 100 between a charged particle beam 101 and a charged particle beam 102. In contrast, the particle beam therapy system 51 of Embodiment 1 differs from that of Comparative Example in using the beam-path changer 16 whose deflection angle is smaller than the deflection angle θ1 of the bending magnet 100 but whose switching speed is faster than the switching speed of the bending magnet. The beam-path changer 16 of Embodiment 1 is a kicker electromagnet 10. From the kicker electromagnet 10 as a beginning point, the beam path is branched into two paths. At a position that is sufficiently and linearly downstream in the beam traveling direction from the kicker electromagnet 10, there is placed the bending magnet 12e for guiding the beam path to the treatment room 29. A charged particle beam 13 is a beam traveling linearly from the kicker electromagnet 10. A charged particle beam 14 is a beam that is entered by the kicker electromagnet 10 into the bending magnet 12e by a deflection angle of θ2 relative to the charged particle beam 13, and then guided to the treatment room 29a. In a particle beam therapy, it is wanted to give a dose according to a treatment plan to a diseased site that is the irradiation target 31, and to avoid unwanted radiation to the surrounding normal tissues as much as possible. Thus, respiratory gated irradiation is performed, in particular, in the case where the irradiation target 31 is such a site that moves with the breathing of the patient 30. More specifically, it is generally said that the movement of an organ due to breathing becomes most steady in a breathing-out state; thus, for the patient 30, his/her abdominal region or the like is subjected to measurement using a patient sensor 27, such as a laser displacement meter, etc., to thereby perform monitoring of his/her breathing state in real-time. As shown in FIG. 1, the respiratory signals psig1 and psig2, that are signals measured by the patient sensors 27 and each indicative of a breathing state, are inputted to the beam-path controller 18 that controls the emitter 62 and the beam-path changer 16. A shown in FIG. 6, when the respiratory signal psig1 falls below a predetermined certain threshold value Th1, namely, in the case where it is determined to be in a breathing-out state, a respiratory gate signal gsig1 for permitting radiation becomes “ON”. When the respiratory gate signal gsig1 is “ON”, the beam-path controller 18 controls the emitter 62, so that the charged particle beam 81 is emitted. FIG. 6 is a diagram illustrating the respiratory signal and the respiratory gate signal of the invention. In FIG. 6, a relationship between the respiratory signal psig1 and the respiratory gate signal gsig1 is shown. Shown at the upper side is the respiratory signal psig1 and at the under side is the respiratory gate signal gsig1. The abscissa represents time t, and the ordinate represents a signal value of the respiratory signal psig1 or the respiratory gate signal gsig1. In the figure, indicated by BL is a base line of the respiratory signal psig1. Note that, in FIG. 6, the “ON” state of the respiratory gate signal gsig1 for permitting radiation is represented as a signal-value H state (high signal-value state). The relationship between the respiratory signal psig2 and the respiratory gate signal gsig2 is also similar to in FIG. 6, so that, when the respiratory signal psig2 falls below a predetermined certain threshold value Th2, namely, in the case where it is determined to be in a breathing-out state, a respiratory gate signal gsig2 for permitting radiation becomes “ON”. The accelerator-system control device 121 in the treatment management device 95 controls the accelerator 54 and the beam transport system 59 so that, with respect to the plurality of particle beam irradiation apparatuses 58 in which treatment is performed at the same treatment period of time, the charged particle beam 81 is transported to each one of the plurality of particle beam irradiation apparatuses 58 for each time period allocated thereto. In the case where the charged particle beam 81 is to be transported to only one of the plurality of treatment rooms 29a, 29b, the beam-path controller 18 in the accelerator-system control device 121 causes the beam-path changer 16 to switch the beam path to the corresponding one and then not to change the beam path until the irradiation treatment by the charged particle beam 81 is completed. Next, description will be made about the case where irradiation treatment is performed in the plurality of treatment rooms 29a, 29b, etc. in the same period of time, namely, about the case where requests for radiation of the charged particle beam 81 to the plurality of treatment rooms 29a, 29b, etc. are overlapping. FIG. 5 is a timing chart illustrating a beam distribution to the plurality of treatment rooms according to the particle beam therapy system of Embodiment 1 of the invention. In FIG. 5, there are illustrated: a beam waveform in the accelerator 54; a time-sharing signal ssig; the respiratory gate signal gsig1; an irradiation current Ibem1 for the treatment room 29a (treatment room 1); the respiratory gate signal gsig2; an irradiation current Ibem2 for the treatment room 29b (treatment room 2); a respiratory gate signal gsig3; and an irradiation current Ibem3 for another treatment room (treatment room 3). The time-share signal ssig is a predetermined cyclic signal for the beam-path changer 16, which is a signal for designating one from the plurality of treatment rooms 29 (particle beam irradiation apparatuses 58 in the plurality of treatment rooms). Specific example of the time-share signal ssig will be described later. The respiratory gate signal gsig3 is a respiratory gate signal for permitting radiation to the other treatment room (treatment room 3). The abscissa represents time t, and the uppermost ordinate for “Beam” represents energy. Each ordinate for the time-sharing signal ssig and the respiratory gate signals gsig1, gsig2, gsig3, represents a signal value of each of these signals, and each ordinate for the irradiation currents Ibem1, Ibem2, Ibem3 represents a current value. According to the invention, in the plurality of treatment rooms 29, the respective patients 30 are each subjected to monitoring of his/her breathing state. FIG. 5 shows distribution examples of the charged particle beam 81 in the three treatment rooms, and thus, for each treatment room designated by the time-sharing signal ssig and when the respiratory gate signal for that treatment room becomes “ON”, the particle beam therapy system 51 of the invention transports the charged particle beam 81 time-divisionally to that treatment room so as to radiate the charged particle beam 81 to the patient in that treatment room for a specified time to thereby supply the irradiation current Ibem to him/her. For the irradiation currents, a symbol of Ibem is used collectively, and the symbol is used as being suffixed with a number, such as Ibem1, Ibem2, Ibem3 or the like, when they are to be described distinctively. In the beam shown uppermost in FIG. 5, the charged particles are accelerated to provide a flat-top form (a highly-energized stable state of the beam with the energy of a predetermined value), and are decelerated thereafter. In this manner, in the accelerator 54, the charged particles repeatedly fall in an under-acceleration state, a flat-top state, an under-deceleration state and a low-energy state. In the periods T1 and T4 where the time-sharing signal ssig designates the treatment room 1, when the respiratory gate signal gsig1 is “ON”, it is controlled so that the charged particle beam 81 is emitted from the emitter 62 of the accelerator 54 and the beam-path changer 16 guides the charged particle beam 81 to the treatment room 1. By such controlling, in each of the periods T1, T4, the irradiation current Ibem1 is supplied to the irradiation target 31 of the patient 30. In the periods T2 and T5 where the time-sharing signal ssig designates the treatment room 2, when the respiratory gate signal gsig2 is “ON”, it is controlled so that the charged particle beam 81 is emitted from the emitter 62 of the accelerator 54 and the beam-path changer 16 guides the charged particle beam 81 to the treatment room 2. By such controlling, in each of the periods T2, T5, the irradiation current Ibem2 is supplied to the irradiation target 31 of the patient 30. Likewise, in the periods T3 and T6 where the time-sharing signal ssig designates the treatment room 3, when the respiratory gate signal gsig3 is “ON”, it is controlled so that the charged particle beam 81 is emitted from the emitter 62 of the accelerator 54 and the beam-path changer 16 guides the charged particle beam 81 to the treatment room 3. By such controlling, in each of the periods T3, T6, the irradiation current Ibem3 is supplied to the irradiation target 31 of the patient 30. FIG. 7 is a diagram illustrating the time-sharing signal of the invention. In FIG. 7, there are shown three examples, namely, three time-sharing signals of ssig-1, ssig-2 and ssig-3. The time-sharing signal ssig-1 is exemplified for the case of selecting each treatment room depending on a voltage-value difference in a single signal. For example, the treatment room 1, the treatment room 2 and the treatment room 3 are selected when the voltage values of the time-sharing signal ssig-1 are V1, V2 and V3, respectively. The time-sharing signal ssig-2 is exemplified for the case of selecting each treatment room depending on a combination of voltage values of two signals pb0 and pb1. For example, when the voltage value of the signal pb0 is at a high level and the voltage value of the signal pb1 is at a low level, the treatment room 1 is selected. When the voltage value of the signal pb0 is at a low level and the voltage value of the signal pb1 is at a high level, the treatment room 2 is selected. When the voltage value of the signal pb0 is at a high level and the voltage value of the signal pb1 is at a high level, the treatment room 3 is selected. The time-sharing signal ssig-3 is exemplified for the case of selecting each treatment room depending on a combination of voltage values of three signals pc1, pc2 and pc3. For example, when the voltage values of the signals pc1, pc2 and pc3 are at a high level, a low level, and a low level, respectively, the treatment room 1 is selected. When the voltage values of the signals pc1, pc2 and pc3 are at a low level, a high level, and a low level, respectively, the treatment room 2 is selected. When the voltage values of the signals pc1, pc2 and pc3 are at a low level, a low level, and a high level, respectively, the treatment room 3 is selected. The beam-path controller 18 will be described in detail. FIG. 8 is a diagram showing the beam-path controller in FIG. 1, and FIG. 9 is a timing chart illustrating a beam distribution to the plurality of treatment rooms according to Embodiment 1 of the invention. In FIG. 9, the abscissa represents time t. Each ordinate for the time-sharing signal ssig, the respiratory gate signals gsig1, gsig2, an emitter control signal csiga, and a kicker control signal csigb represents a signal value of each of these signals, and each ordinate for the irradiation currents Ibem1, Ibem2 represents a current value. The beam-path controller 18 includes: a time-sharing signal generator 33 for generating the time-sharing signal ssig; a respiratory gate-signal generator 34 for generating the respiratory gate signals gsig1, gsig2; an emitter control-signal generator 36 for generating the emitter control signal csiga; and a kicker control-signal generator (beam-path changer control-signal generator) 37 for generating the kicker control signal csigb that is a beam-path changer control signal. The time-sharing signal generator 33 and the respiratory gate-signal generator 34 constitute a control signal generator 35. The time-sharing signal generator 33 generates the time-sharing signal ssig that corresponds to the treatment rooms in which irradiation treatment is performed in the same period of time. In FIG. 9, there is shown a case where irradiation treatment is performed in the two treatment rooms 29a, 29b in the same period of time. The time-sharing signal ssig is a cyclic signal and in FIG. 9, its one cycle is from the time t1 to the time t5. The cycle of the time-sharing signal ssig is Tc1. The time-sharing signal ssig shown in FIG. 9 is a signal that, in the first cyclic period, selects the treatment room 1 during the time t1 to the time t3 and selects the treatment room 2 during the time t3 to the time t4. In the second cyclic period, the time-sharing signal ssig is a signal that selects the treatment room 1 during the time t5 to the time t7 and selects the treatment room 2 during the time t7 to the time t9. The cycle Tc1 of the time-sharing signal ssig and an increase/decrease cycle in energy of the charged particle beam 81 in the accelerator 54, are controlled to be nearly matched to each other by the accelerator-system control device 121. The accelerator 54 is controlled so that the flat-top state is established at least in a period (from t1 to t4, and from t5 to t9) where the charged particle beam 81 is distributed to the plurality of treatment rooms. A distribution time for each of the treatment room 1 and the treatment room 2 may be determined arbitrarily. When the total irradiation time for a patient in the treatment room 1 and that for a patient in the treatment room 2 are largely different to each other, it suffices to make longer the distribution time for the patient with the longer total irradiation time. When the total irradiation time for the patient 30a in the treatment room 29a (treatment room 1) is longer than the total irradiation time for the patient 30b in the treatment room 29b (treatment room 2), it suffices to make the distribution time (t3−t1) for the treatment room 1 longer than the distribution time (t4−t3) for the treatment room 2. In this manner, the distribution time for the treatment room 1 is varied according to the total irradiation time for the patient, so that, even though the energy is required to be changed at the time of slice change, if each hit rate is nearly equal, each irradiation completion time for the plurality of treatment rooms can be matched to each other. Thus, it is possible to efficiently utilize the charged particle beam 81 without wastefully shutting off the charged particle beam 81. The respiratory gate-signal generator 34 generates the respiratory gate signal gsig1 from the respiratory signal psig1 transmitted from the respiratory signal generator 26a, and generates the respiratory gate signal gsig2 from the respiratory signal psig2 transmitted from the respiratory signal generator 26b. How to generate the respiratory gate signals gsig1, gsig2 is just as described previously. The emitter control-signal generator 36 receives the respiratory gate signals gsig1, gsig2 to thereby generate the emitter control signal csiga as follows. In FIG. 9, when the time-sharing signal ssig designates the treatment room 1 and the respiratory gate signal gsig1 for the treatment room 1 is “ON” (signal-value H state), the emitter control-signal generator 36 outputs an emission command (signal-value H state) for ordering the emitter 62 to emit the charged particle beam 81. Further, when the time-sharing signal ssig designates the treatment room 2 and the respiratory gate signal gsig2 for the treatment room 2 is “ON” (signal-value H state), the emitter control-signal generator 36 outputs an emission command (signal-value H state) for ordering the emitter 62 to emit the charged particle beam 81. The emitter control-signal generator 36, when the condition for outputting the emission command becomes unsatisfied, places the emitter control signal csiga in an emission stopped state and outputs an emission stop command (signal-value L state) for ordering the emitter 62 to stop emission of the charged particle beam 81. In FIG. 9, a period from the time t2 to the time t4 in the first cyclic period, and periods from the time t6 to the time t7 and from the time t8 to the time t9 in the second cyclic period are the periods where the emission command of the charged particle beam 81 is outputted. The kicker control-signal generator 37 receives the time-sharing signal ssig to thereby generate the kicker control signal csigb as follows. In FIG. 9, when the time-sharing signal ssig designates the treatment room 1, the kicker control-signal generator 37 outputs a path-1 command (signal-value Ib1 state) for ordering switching of the path so that the charged particle beam 81 is guided to the treatment room 1 (treatment room 29a). When the time-sharing signal ssig designates the treatment room 2, the kicker control-signal generator 37 outputs a path-2 command (signal-value Ib2 state) for ordering switching of the path so that the charged particle beam 81 is guided to the treatment room 2 (treatment room 29b). The kicker control-signal generator 37 outputs, in the case of the path-1 command, a control current of the signal value Ib1 to the kicker electromagnet 10, and outputs, in the case of the path-2 command, a control current of the signal value Ib2 to the kicker electromagnet 10. Note that, in FIG. 9, such a case is shown where, when the time-sharing signal ssig does not designate anyone of the treatment rooms (neither the treatment room 1 nor the treatment room 2), the signal value of the kicker control signal csigb is at a signal level of other than Ib1 and also other than Ib2, for example, at zero level. During the time t2 to the time t3 in the first cyclic period, the emitter control signal csiga provides the emission command (signal-value H state) and the kicker control signal csigb provides the path-1 command (signal-value Ib1 state), so that, in the particle beam therapy system 51 of Embodiment 1, the charged particle beam 81 is emitted and the irradiation current Ibem1 is supplied to the irradiation target 31a of the patient 30a in the treatment room 1 (treatment room 29a). During the time t3 to the time t4, the emitter control signal csiga provides the emission command (signal-value H state) and the kicker control signal csigb provides the path-2 command (signal-value Ib2 state), so that, in the particle beam therapy system 51 of Embodiment 1, the charged particle beam 81 is emitted and the irradiation current Ibem2 is supplied to the irradiation target 31b of the patient 30b in the treatment room 2 (treatment room 29b). During the time t6 to the time t7 in the second cyclic period, the emitter control signal csiga provides the emission command (signal-value H state) and the kicker control signal csigb provides the path-1 command (signal-value Ib1 state), so that, in the particle beam therapy system 51 of Embodiment 1, the charged particle beam 81 is emitted and the irradiation current Ibem1 is supplied to the irradiation target 31a of the patient 30a in the treatment room 1 (treatment room 29a). During the time t8 to the time t9, the emitter control signal csiga provides the emission command (signal-value H state) and the kicker control signal csigb provides the path-2 command (signal-value Ib2 state), so that, in the particle beam therapy system 51 of Embodiment 1, the charged particle beam 81 is emitted and the irradiation current Ibem2 is supplied to the irradiation target 31b of the patient 30b in the treatment room 2 (treatment room 29b). According to the particle beam therapy system 51 of Embodiment 1, the beam path is switched using the beam-path changer 16 whose deflection angle is smaller than that of the bending magnet 100 but whose switching speed is faster than that of the bending magnet. Thus, unlike the conventional one, it is possible to transport the beam to the plurality of treatment rooms 29 as if simultaneously by time-sharing, even without using respiratory navigation. According to the particle beam therapy system 51 of Embodiment 1, it is not required to perform respiratory navigation, so that a patient can be subjected to a particle beam therapy in a relaxed state specific to the patient. According to the particle beam therapy system 51 of Embodiment 1, since a respiratory cycle is not forcibly induced by respiratory navigation, the patient feels relief and thus can promptly enter his/her respiration stable state. This makes it possible to reduce the occupation time of the treatment room, to thereby improve throughput of the treatment as compared with the conventional case. According to particle beam therapy system 51 of Embodiment 1, since a patient can be subjected to a particle beam therapy in a relaxed state specific to the patient, the breathing-out state of the patient in one respiration cycle can be made longer than the conventional case, and thus, it is possible to make longer a time period where each of the respiratory gate signals gsig1, gsig2 is made “ON”. When the time period where each of the respiratory gate signals gsig1, gsig2 is made “ON” becomes longer, the number of irradiation interruption processes of the charged particle beam in one irradiation treatment becomes reduced, so that an irradiation time period where the charged particle beam 81 is intermittently radiated, namely, the irradiation time period from the start of irradiation to the completion of irradiation, can be reduced. This makes it possible to reduce the occupation time of the treatment room 29a, 29b, to thereby improve throughput of the treatment as compared with the conventional case. It should be noted that the respiratory gate signal (gsig1, gsig2, gsig3 or the like) may be generated by a device other than the beam-path controller 18, and if this is the case, such a configuration may be applied in which an externally-generated respiratory gate signal is inputted to the beam-path controller 18. The same applies to other embodiments to be described later. The particle beam therapy system 51 of Embodiment 1 comprises: the plurality of treatment rooms 29; the plurality of particle beam irradiation apparatuses 58 placed respectively in the plurality of treatment rooms 29; the accelerator 54 that accelerates the charged particle beam 81; the beam transport system 59 that transports the charged particle beam 81 accelerated by the accelerator 54 to the plurality of particle beam irradiation apparatuses 58; and the treatment management device 95 that controls the accelerator 54, the beam transport system 59 and the plurality of particle beam irradiation apparatuses 58. According to the particle beam therapy system 51 of Embodiment 1, it is characterized in that: the beam transport system 59 includes the beam-path changer 16 for changing a beam path so as to transport the charged particle beam 81 to any one of the plurality of particle beam irradiation apparatuses 58; the treatment management device 95 includes the beam-path controller 18 that generates the emitter control signal csiga for controlling the emitter 62 of the accelerator 54 and the beam-path changer control signal (kicker control signal csigb) for controlling the beam-path changer 16 so that, with respect to the plurality of particle beam irradiation apparatuses 58 in which treatment is performed at the same treatment period of time, the charged particle beam 81 is transported to each one of the plurality of particle beam irradiation apparatuses 58 for each time period allocated thereto; and the beam-path controller 18 generates the emitter control signal csiga and the beam-path changer control signal (kicker control signal csigb) on the basis of: the plurality of respiration gate signals gsig1, gsig2 for permitting radiation of the charged particle beam 81 that are generated, from individual monitoring of respiratory states of the plurality of patients 30 to be irradiated with the charged particle beam 81 by the plurality of particle beam irradiation apparatuses 58, respectively for the plurality of patients 30; and the time-sharing signal ssig for cyclically selecting each one of the plurality of particle beam irradiation apparatuses 58. Thus, it is possible to transport the beam to the plurality of treatment rooms 29 as if simultaneously by time-sharing, even without using respiratory navigation. FIG. 10 is a configuration diagram showing a particle beam therapy system according to Embodiment 2 of the invention, and FIG. 11 is a diagram showing a beam-path controller in FIG. 10. FIG. 12 is a diagram showing a damper placed near a duct branching point in FIG. 10, and FIG. 13 is a timing chart illustrating a beam distribution to a plurality of treatment rooms according to Embodiment 2 of the invention. The particle beam therapy system 51 of Embodiment 2 differs from the particle beam therapy system 51 of Embodiment 1 in that a damper 11 for shutting off the charged particle beam 81 is provided in a duct branching section 21 placed at the downstream side of the beam-path changer 16, and in that the treatment management device 95 includes a beam-path controller 19 for outputting to the beam-path changer 16, a kicker control signal csigd that is a beam-path changer control signal. The beam-path controller 19 includes, in place of the emitter control-signal generator 36 and the kicker control-signal generator 37 in Embodiment 1, an emitter control-signal generator 39 for generating an emitter control signal csiga and a kicker control-signal generator (beam-path changer control-signal generator) 40. The kicker control-signal generator 40 receives the respiratory gate signals gsig1, gsig2 and the time-sharing signal ssig to thereby output the kicker control signal csigd generated therein. The emitter control-signal generator 39 receives the respiratory gate signals gsig1, gsig2 and the time-sharing signal ssig to thereby generate the emitter control signal csiga corresponding to the kicker control signal csigd, and outputs it to the emitter 62. Operations of the particle beam therapy system 51 of Embodiment 2 will be described using FIG. 13. Description will be made about part of operations which differs from Embodiment 1. The emitter control-signal generator 39 receives the respiratory gate signals gsig1, gsig2 and the time-sharing signal ssig, to thereby generate the emitter control signal csiga as follows. In each cyclic period of the time-sharing signal ssig, when the time-sharing signal ssig designates the treatment room 1 that is the first treatment room and the respiratory gate signal gsig1 for the treatment room 1 is “ON” (signal-value H state), the emitter control-signal generator 39 outputs an emission command (signal-value H state) for ordering the emitter 62 to emit the charged particle beam 81. The emitter control signal csiga, once becomes in an emission-ordering state, maintains the emission-ordering state until the designation of the treatment room 2 that corresponds to the last treatment room is removed in the time-sharing signal ssig. Namely, when the designation of the treatment room 2 that corresponds to the last treatment room is removed in the time-sharing signal ssig, the emitter control-signal generator 39 places the emitter control signal csiga in an emission stopped state and outputs an emission stop command (signal-value L state) for ordering the emitter 62 to stop emission of the charged particle beam 81. In FIG. 13, a period from the time t2 to the time t4 in the first cyclic period, and a period from the time t6 to the time t9 in the second cyclic period are the periods where the emission command of the charged particle beam 81 is outputted. The kicker control-signal generator 40 receives the respiratory gate signals gsig1, gsig2 and the time-sharing signal ssig to thereby generate the kicker control signal csigd as follows. In FIG. 13, when the time-sharing signal ssig designates the treatment room 1 and the respiratory gate signal gsig1 is “ON”, the kicker control-signal generator 40 outputs a path-1 command (signal-value Id1 state) for ordering switching of the path so that the charged particle beam 81 is guided to the treatment room 1 (treatment room 29a). When the time-sharing signal ssig designates the treatment room 2 and the respiratory gate signal gsig2 is “ON”, the kicker control-signal generator 40 outputs a path-2 command (signal-value Id3 state) for ordering switching of the path so that the charged particle beam 81 is guided to the treatment room 2 (treatment room 29b). When the time-sharing signal ssig designates either one of the treatment rooms (treatment room 1, treatment room 2) and the respiratory gate signal corresponding to that treatment room (gsig1, gsig2) is “OFF”, the kicker control-signal generator 40 outputs a path-3 command (signal-value Id2 state) for ordering switching of the path so that the charged particle beam 81 is guided to the damper 11. The path-3 command differs from the path command for transporting the charged particle beam 81 to the designated treatment room 29 in the plurality of treatment rooms 29, and can be also said to be a path shutoff command for shutting off the transportation of the charged particle beam 81 to the plurality of treatment rooms 29. The kicker control-signal generator 40 outputs, in the case of the path-1 command, a control current of the signal value Id1 to the kicker electromagnet 10, outputs, in the case of the path-2 command, a control current of the signal value Id3 to the kicker electromagnet 10, and outputs, in the case of the path-3 command, a control signal of the signal value Id2 to the kicker electromagnet 10. Note that, in FIG. 13, such a case is shown where, when the time-sharing signal ssig does not designate anyone of the treatment rooms (neither the treatment room 1 nor the treatment room 2), the signal value of the kicker control signal csigd is at a signal level of other than Id1, Id2 and Id3, for example, at zero level. During the time t2 to the time t3 in the first cyclic period, the emitter control signal csiga provides the emission command (signal-value H state) and the kicker control signal csigd provides the path-1 command (signal-value Id1 state), so that, in the particle beam therapy system 51 of Embodiment 2, the charged particle beam 81 is emitted and the irradiation current Ibem1 is supplied to the irradiation target 31a of the patient 30a in the treatment room 1 (treatment room 29a). During the time t3 to the time t4, the emitter control signal csiga provides the emission command (signal-value H state) and the kicker control signal csigd provides the path-2 command (signal-value Id3 state), so that, in the particle beam therapy system 51 of Embodiment 2, the charged particle beam 81 is emitted and the irradiation current Ibem2 is supplied to the irradiation target 31b of the patient 30b in the treatment room 2 (treatment room 29b). During the time t1 to the time t2, the emitter control signal csiga provides the emission stop command (signal-value L state), so that, in the particle beam therapy system 51 of Embodiment 2, the charged particle beam 81 is not emitted. During the time t6 to the time t7 in the second cyclic period, the emitter control signal csiga provides the emission command (signal-value H state) and the kicker control signal csigd provides the path-1 command (signal-value Id1 state), so that, in the particle beam therapy system 51 of Embodiment 2, the charged particle beam 81 is emitted and the irradiation current Ibem1 is supplied to the irradiation target 31a of the patient 30a in the treatment room 1 (treatment room 29a). During the time t8 to the time t9, the emitter control signal csiga provides the emission command (signal-value H state) and the kicker control signal csigd provides the path-2 command (signal-value Id3 state), so that, in the particle beam therapy system 51 of Embodiment 2, the charged particle beam 81 is emitted and the irradiation current Ibem2 is supplied to the irradiation target 31b of the patient 30b in the treatment room 2 (treatment room 29b). During the time t5 to the time t6, the emitter control signal csiga provides the emission stop command (signal-value L state), so that, in the particle beam therapy system 51 of Embodiment 2, the charged particle beam 81 is not emitted. During the time t7 to the time t8, although the emitter control signal csiga provides the emission command (signal-value H state), the kicker control signal csigd provides the path-3 command (signal-value Id2 state), so that, in the particle beam therapy system 51 of Embodiment 2, the charged particle beam 81 is shut off by the damper 11. Note that in FIG. 13, such a case is shown where, during the time t1 to the time t2 and the time t5 to the time t6, the kicker control signal csigd provides the path-3 command (signal-value Id2 state); however, the kicker control signal csigd may be in another signal-value state, such as the signal-value Id1 state, the signal-value Id3 state or the like, because the emitter control signal csiga provides the emission stop command (signal-value L state) during the time t1 to the time t2 and the time t5 to the time t6. Further, the description has been made using the case where the damper 11 for shutting off the charged particle beam 81, which is single, is provided in the duct branching section 21 placed at the downstream side of the beam-path changer 16; however, as shown in FIG. 14, dampers 11a, 11b may be provided individually for each downstream beam-transport system. FIG. 14 is a diagram showing other dampers placed near a duct branching point in FIG. 10. The particle beam therapy system 51 of Embodiment 2 achieves the same effect as in Embodiment 1. The particle beam therapy system 51 of Embodiment 2 includes the damper 11 or the dampers 11a, 11b, wherein in each cyclic period of the time-sharing signal ssig, the emitter control signal csiga, once becomes in an emission-ordering state, maintains the emission-ordering state until the designation of the treatment room 2 that corresponds to the last treatment room is removed in the time-sharing signal ssig, and wherein, when the charged particle beam 81 is to be shut off in the middle of the emission-ordering state, it is shut off by the damper 11, 11a or 11b. Thus, it is possible to shut off the charged particle beam 81 more rapidly than in Embodiment 1, so that the irradiation current with a time width shorter than that in Embodiment 1 can be supplied to the irradiation target 31 of the patient 30. FIG. 15 is a configuration diagram showing a particle beam therapy system according to Embodiment 3 of the invention, and FIG. 16 is a diagram showing a beam-path controller in FIG. 15. FIG. 17 is a timing chart illustrating a beam distribution to a plurality of treatment rooms according to Embodiment 3 of the invention. When irradiation requests from the plurality of treatment rooms 29 are overlapping, for example, when the respiratory gate signal gsig1 for the treatment room 1 is in “ON” state and the respiratory gate signal gsig2 for the treatment room 2 is in “ON” state, the particle beam therapy system 51 of Embodiment 3 controls so as to make switching of the charged particle beam 81 between toward the respective corresponding treatment rooms 1, 2 (treatment rooms 29a, 29b) in a short time, as shown below. The treatment management device 95 in Embodiment 3 differs from that in Embodiment 1 in including a beam-path controller 63 that outputs a kicker control signal csigb whose signal value varies in a time period shorter than in Embodiment 1. The beam-path controller 63 includes: an emitter control-signal generator 46 for generating the emitter control signal csiga; a kicker control-signal generator (beam-path changer control-signal generator) 47 for generating the kicker control signal csigb; and a control signal generator 35 for outputting a plurality of control signals to the emitter control-signal generator 46 and the kicker control-signal generator 47. The control signal generator 35 includes: a time-sharing signal generator 45 for generating a time-sharing signal ssiga with a cycle of Tc2 that is shorter than that in Embodiment 1; a respiratory gate-signal generator 34 for generating the respiratory gate signals gsig1, gsig2; and a mask signal generator 44 for generating a mask signal msig for masking a treatment-room selection by the time-sharing signal ssiga. The time-sharing signal ssiga has the cycle Tc2 that causes the treatment-room designation to change two or more times in a period where the respiratory gate signals gsig1 and gsig2 keep “ON” states. Operations of the particle beam therapy system 51 of Embodiment 3 will be described using FIG. 17. In FIG. 17, the abscissa represents time t. Each ordinate for the time-sharing signal ssiga, the respiratory gate signals gsig1, gsig2, the mask signal msig, the emitter control signal csiga, and the kicker control signal csigb represents a signal value of each of these signals, and each ordinate for the irradiation currents Ibem1, Ibem2 represents a current value. Note that, in order not to complicate the figure, illustrated here is a case where the time-sharing signal ssiga selects the treatment room 1 and the treatment room 2 at its H level and L level, respectively. When the time-sharing signal ssiga is at H level, the treatment room 1 is designated, and when the time-sharing signal ssiga is at L level, the treatment room 2 is designated. Note that the time-sharing signal ssiga can be constituted in a form of the time-sharing signals ssig-1, ssig-2 and ssig-3 shown in FIG. 7. As shown in FIG. 17, the time-sharing signal generator 45 generates the time-sharing signal ssiga with the cycle Tc2 that is shorter than the cycle Tc1 in Embodiment 1. The mask signal generator 44 receives the respiratory gate signals gsig1, gsig2, to thereby generate the mask signal msig. The mask signal msig is, for example when its output signal value is in H state, a masking command for masking (for making ineffective) a treatment-room selection by the time-sharing signal ssiga. The mask signal msig is, when its output signal value is in L state, a mask cancelling command for making effective a treatment-room selection by the time-sharing signal ssiga. The mask signal generator 44 outputs the mask signal msig as the mask cancelling command when at least two respiratory gate signals in the plurality of respiratory gate signals, are “ON” simultaneously. The mask signal generator 44 outputs the mask signal msig as the masking command when there is no plural respiratory gate signals being simultaneously “ON”, namely, when all of the respiratory gate signals are “OFF” or only one of the respiratory gate signals is “ON”. The respiratory gate signal gsig1 is “ON” during the time t1 to the time t8, and the respiratory gate signal gsig2 is “ON” during the time t3 to the time t10, so that the mask signal generator 44 outputs the mask signal msig as the masking command (signal-value H state) in a time period from the time t3 to the time t8 (Period A), and outputs the mask signal msig as the mask cancelling command (signal-value L state) during other than the time period of Period A. The emitter control-signal generator 46 receives the respiratory gate signals gsig1, gsig2, the time-sharing signal ssiga and the mask signal msig, to thereby generate the emitter control signal csiga as follows. First of all, with respect to the emission command (signal-value H state) for ordering the emitter 62 to emit the charged particle beam 81, the following three cases arise. When the mask signal msig provides the masking command (signal-value H state) and one of the respiratory gate signals (respiratory gate signal gsig1 or respiratory gate signal gsig2) is “ON” (signal-value H state) (First Case), the emitter control-signal generator 46 outputs the emission command (signal-value H state) for ordering the emitter 62 to emit the charged particle beam 81. When the mask signal msig provides the mask canceling command (signal-value L state), the time-sharing signal ssiga designates the treatment room 1, and the respiratory gate signal gsig1 for the treatment room 1 is “ON” (signal-value H state) (Second Case), the emitter control-signal generator 46 outputs the emission command (signal-value H state) for ordering the emitter 62 to emit the charged particle beam 81. When the mask signal msig provides the mask canceling command (signal-value L state), the time-sharing signal ssiga designates the treatment room 2, and the respiratory gate signal gsig2 for the treatment room 2 is “ON” (signal-value H state) (Third Case), the emitter control-signal generator 46 outputs the emission command (signal-value H state) for ordering the emitter 62 to emit the charged particle beam 81. In other than the above three cases, the emitter control-signal generator 46 outputs an emission stop command (signal-value L state) for ordering the emitter 62 to stop emission of the charged particle beam 81. In FIG. 17, the period from the time t1 to the time t8 and the period from the time t9 to the time t10, are each a period where the emission command of the charged particle beam 81 is outputted. The kicker control-signal generator 47 receives the respiratory gate signals gsig1, gsig2, the time-sharing signal ssiga and the mask signal msig, to thereby generate the kicker control signal csigb as follows. In FIG. 17, when the mask signal msig provides the masking command (signal-value H state) and the respiratory gate signal gsig1 is “ON” (signal-value H state), the kicker control-signal generator 47 outputs a path-1 command (signal-value Ib1 state) for ordering switching of the path so that the charged particle beam 81 is guided to the treatment room 1 (treatment room 29a). Further, when the mask signal msig provides the mask cancelling command (signal-value L state), the time-sharing signal ssiga designates the treatment room 1, and the respiratory gate signal gsig1 for the treatment room 1 is “ON” (signal-value H state), the kicker control-signal generator 47 outputs the path-1 command (signal-value Ib1 state) for ordering switching of the path so that the charged particle beam 81 is guided to the treatment room 1 (treatment room 29a). When the mask signal msig provides the masking command (signal-value H state) and the respiratory gate signal gsig2 is “ON” (signal-value H state), the kicker control-signal generator 47 outputs a path-2 command (signal-value Ib2 state) for ordering switching of the path so that the charged particle beam 81 is guided to the treatment room 2 (treatment room 29b). Further, when the mask signal msig provides the mask cancelling command (signal-value L state), the time-sharing signal ssiga designates the treatment room 2, and the respiratory gate signal gsig2 for the treatment room is “ON” (signal-value H state), the kicker control-signal generator 47 outputs the path-2 command (signal-value Ib2 state) for ordering switching of the path so that the charged particle beam 81 is guided to the treatment room 2 (treatment room 29b). The kicker control-signal generator 47 outputs, in the case of the path-1 command, a control current of the signal value Ib1 to the kicker electromagnet 10, and outputs, in the case of the path-2 command, a control current of the signal value Ib2 to the kicker electromagnet 10. Note that, in FIG. 17, such a case is shown where, when neither the path-1 command nor the path-2 command is outputted, the signal value of the kicker control signal csigb is at a signal level of other than Ib1 and also other than Ib2, for example, at zero level. In each of periods from the time t2 to the time t4, from the time t5 to the time t6, and from the time t7 to the time t8, the emitter control signal csiga provides the emission command (signal-value H state) and the kicker control signal csigb provides the path-1 command (signal-value Ib1 state), so that, in the particle beam therapy system 51 of Embodiment 3, the charged particle beam 81 is emitted and the irradiation current Ibem1 is supplied to the irradiation target 31a of the patient 30a in the treatment room 1 (treatment room 29a). In each of periods from the time t4 to the time t5, from the time t6 to the time t7, and from the time t9 to the time t10, the emitter control signal csiga provides the emission command (signal-value H state) and the kicker control signal csigb provides the path-2 command (signal-value Ib2 state), so that, in the particle beam therapy system 51 of Embodiment 3, the charged particle beam 81 is emitted and the irradiation current Ibem2 is supplied to the irradiation target 31b of the patient 30b in the treatment room 2 (treatment room 29b). The particle beam therapy system 51 of Embodiment 3 achieves the same effect as in Embodiment 1. The particle beam therapy system 51 of Embodiment 3 includes the beam-path controller 63 that generates the kicker control signal csigb and the emitter control signal csiga, by use of the time-sharing signal ssiga with a cycle shorter than that of the time-sharing signal ssig in Embodiment 1 and the mask signal msig for masking the treatment-room selection by the time-sharing signal ssiga; and can supply the irradiation current with a short time width to the irradiation target 31 of the patient 30 with respect to the treatment room from which an irradiation request is issued and which is designated by the time-sharing signal ssiga, when the mask signal msig provides the mask canceling command (signal-value L state). Describing more specifically, as shown from the time t3 to the time t8 in FIG. 17, when the mask signal msig provides the mask cancelling command (signal-value L state) and the respiratory gate signal gsig1 and the respiratory gate signal gsig2 are simultaneously in “ON” state, the beam-path controller 63 causes the path command provided in the kicker control signal csigb to change plural times in a short time period, so that the irradiation current with a short time width can be supplied to the irradiation target 31 of the patient 30. The particle beam therapy system 51 of Embodiment 3 can supply the irradiation current with a time width shorter than that in Embodiment 1 to the irradiation target 31 of the patient 30; such a method of rapidly switching the beam path as in Embodiment 3 is profitable in the case, like repainting irradiation, where irradiation is performed plural times while decreasing each irradiation dose (the number of particles subjected to irradiation per a specified time period), namely, in the case of irradiation in a manner like that, in pictorial art, a light-colored paint is repeatedly painted. It is noted that, in FIG. 17, such a case is shown where the number of the respiratory gate signals is two; instead, in the case where the number of the respiratory gate signals is three, the mask signal msig will be given as follows. The mask signal msig provides the masking command in a case where all of the respiratory signals are “OFF” and in each of three cases where only one of the respiratory gate signals becomes “ON”, that is, in total four cases. The mask signal msig provides the mask cancelling command in a case where the three respiratory gate signals gsig1, gsig2, gsig3 are simultaneously “ON” and in each of cases (three cases) where two respiratory gate signals in the three respiratory gate signals are simultaneously “ON”, that is, in total four cases. Thus, the particle beam therapy system 51 of Embodiment 3 can be applied also in a case where the number of the respiratory gate signals is three or more. Meanwhile, in the case where the number of the respiratory gate signals is three or more, the number of treatment rooms for which the charged particle beam 81 is controlled to be switched in a short time may be limited to two. Further, in the cycle Tc2 of the time-sharing signal ssiga, a time period allocated to each of the treatment rooms 29 for its selection is not limited to the case where it is evenly set, and may be set arbitrarily. In Embodiment 3, such a case has been shown where, when irradiation requests from the plurality of treatment rooms 29 are overlapping, the charged particle beam 81 is controlled to be switched between toward the respective corresponding treatment rooms 1, 2 (treatment rooms 29a, 29b) in a short time, by use of the time-sharing signal ssiga with the cycle Tc2 that is shorter than that in Embodiment 1 and the mask signal msig for masking the treatment-room selection by the time-sharing signal ssiga. In Embodiment 4, such a case will be described where, in the particle beam irradiation system 51 provided with a damper 11 in the beam transport system 59, the charged particle beam 81 is controlled to be switched between toward the plurality of treatment rooms 29 in a short time. FIG. 18 is a configuration diagram showing a particle beam therapy system according to Embodiment 4 of the invention, and FIG. 19 is a diagram showing a beam-path controller in FIG. 18. FIG. 20 is a timing chart illustrating a beam distribution to a plurality of treatment rooms according to Embodiment 4 of the invention. The treatment management device 95 in Embodiment 4 differs from that in Embodiment 2 in including a beam-path controller 64 that outputs a kicker control signal csigd whose signal value varies in a time period shorter than in Embodiment 2. The beam-path controller 64 includes: an emitter control-signal generator 57 for generating an emitter control signal csiga; a kicker control-signal generator (beam-path changer control-signal generator) 60 for generating the kicker control signal csigd; and a control signal generator 35 for outputting a plurality of control signals to the emitter control-signal generator 57 and the kicker control-signal generator 60. The control signal generator 35 includes: a time-sharing signal generator 45 for generating a time-sharing signal ssiga with a cycle of Tc2 that is shorter than that in Embodiment 2; a respiratory gate-signal generator 34 for generating the respiratory gate signals gsig1, gsig2; and a mask signal generator 44 for generating a mask signal msig for masking a treatment-room selection by the time-sharing signal ssiga. When irradiation requests from the plurality of treatment rooms 29 are overlapping, for example, when the respiratory gate signal gsig1 for the treatment room 1 is in “ON” state and the respiratory gate signal gsig2 for the other treatment room 2 is in “ON” state, the particle beam therapy system 51 of Embodiment 4 controls so as to make switching of the charged particle beam 81 between toward the respective corresponding treatment rooms 1, 2 (treatment rooms 29a, 29b) in a short time. Further, at a time of switching between a period where irradiation requests from the plurality of treatment rooms 29 are given and a period where an irradiation request only from one of the treatment rooms 29 is given, the particle beam therapy system 51 of Embodiment 4 controls, depending on a situation, so as to switch in a short time between the beam path toward the corresponding treatment room 29 and the beam path toward the damper 11. First, description will be made on how to control the charged particle beam 81 to be switched between toward the respective corresponding treatment rooms 1, 2 (treatment rooms 29a, 29b) in a short time, when irradiation requests from the plurality of treatment rooms 29 are overlapping. Operations of the particle beam therapy system 51 of Embodiment 4 will be described using FIG. 20. In FIG. 20, the abscissa represents time t. Each ordinate for the time-sharing signal ssiga, the respiratory gate signals gsig1, gsig2, the mask signal msig, the emitter control signal csiga, and the kicker control signal csigd represents a signal value of each of these signals, and each ordinate for the irradiation currents Ibem1, Ibem2 represents a current value. Note that, in order not to complicate the figure, illustrated here is a case where the time-sharing signal ssiga selects the treatment room 1 and the treatment room 2 at its H level and L level, respectively. When the time-sharing signal ssiga is at H level, the treatment room 1 is designated, and when the time-sharing signal ssiga is at L level, the treatment room 2 is designated. Note that the time-sharing signal ssiga can be constituted in a form of the time-sharing signals ssig-1, ssig-2 and ssig-3 shown in FIG. 7. As shown in FIG. 20, the time-sharing signal generator 45 generates the time-sharing signal ssiga with the cycle Tc2 that is shorter than the cycle Tc1 in Embodiment 2. The mask signal generator 44 receives the respiratory gate signals gsig1, gsig2, to thereby generate the mask signal msig. The mask signal msig is, for example when its output signal value is in H state, a masking command for masking (for making ineffective) a treatment-room selection by the time-sharing signal ssiga. The mask signal msig is, when its output signal value is in L state, a mask cancelling command for making effective a treatment-room selection by the time-sharing signal ssiga. The mask signal generator 44 outputs the mask signal msig as the mask cancelling command when at least two respiratory gate signals in the plurality of respiratory gate signals, are “ON” simultaneously. The mask signal generator 44 outputs the mask signal msig as the masking command when there is no plural respiratory gate signals being simultaneously “ON”, namely, when all of the respiratory gate signals are “OFF” or only one of the respiratory gate signals is “ON”. The respiratory gate signal gsig1 is “ON” during the time t1 to the time t8, and the respiratory gate signal gsig2 is “ON” during the time t3 to the time t10, so that the mask signal generator 44 outputs the mask signal msig as the masking command (signal-value H state) in a time period from the time t3 to the time t8 (Period B), and outputs the mask signal msig as the mask cancelling command (signal-value L state) during other than the time period of Period B. The emitter control-signal generator 57 receives the respiratory gate signals gsig1, gsig2 and the time-sharing signal ssiga, to thereby generate the emitter control signal csiga as follows. When at least one of the respiratory gate signals (respiratory gate signal gsig1 or respiratory gate signal gsig2) is “ON” (signal-value H state) (First Case), the emitter control-signal generator 57 outputs the emission command (signal-value H state) for ordering the emitter 62 to emit the charged particle beam 81. In FIG. 20, the period from the time t1 to the time t10 is a period where the emission command of the charged particle beam 81 is outputted. FIG. 20 differs from FIG. 17 in Embodiment 3 in that, in a period from the time t8 to the time t9, the emitter control signal csiga is kept in the emission-ordering state. The kicker control-signal generator 60 receives the respiratory gate signals gsig1, gsig2, the time-sharing signal ssiga and the mask signal msig, to thereby generate the kicker control signal csigd as follows. In FIG. 20, when the mask signal msig provides the masking command (signal-value H state) and the respiratory gate signal gsig1 is “ON” (signal-value H state), the kicker control-signal generator 60 outputs a path-1 command (signal-value Id1 state) for ordering switching of the path so that the charged particle beam 81 is guided to the treatment room 1 (treatment room 29a). Further, when the mask signal msig provides the mask cancelling command (signal-value L state), the time-sharing signal ssiga designates the treatment room 1, and the respiratory gate signal gsig1 for the treatment room 1 is “ON” (signal-value H state), the kicker control-signal generator 60 outputs the path-1 command (signal-value Id1 state) for ordering switching of the path so that the charged particle beam 81 is guided to the treatment room 1 (treatment room 29a). When the mask signal msig provides the masking command (signal-value H state) and the respiratory gate signal gsig2 is “ON” (signal-value H state), the kicker control-signal generator 60 outputs a path-2 command (signal-value Id3 state) for ordering switching of the path so that the charged particle beam 81 is guided to the treatment room 2 (treatment room 29b). Further, when the mask signal msig provides the mask cancelling command (signal-value L state), the time-sharing signal ssiga designates the treatment room 2, and the respiratory gate signal gsig2 for the treatment room is “ON” (signal-value H state), the kicker control-signal generator 60 outputs the path-2 command (signal-value Id3 state) for ordering switching of the path so that the charged particle beam 81 is guided to the treatment room 2 (treatment room 29b). When the mask signal msig provides the mask cancelling command (signal-value L state), the time-sharing signal ssiga designates either one of the treatment rooms (treatment room 1, treatment room 2), and the respiratory gate signal (gsig1, gsig2) corresponding to that treatment room is “OFF”, the kicker control-signal generator 60 outputs the path-3 command (signal-value Id2 state) for ordering switching of the path so that the charged particle beam 81 is guided to the damper 11. Such a case occurs at a time of switching between the period where irradiation requests from the plurality of treatment rooms 29 are given, and the period where an irradiation request only from one of the treatment rooms 29 is given. The kicker control-signal generator 60 outputs, in the case of the path-1 command, a control current of the signal value Id1 to the kicker electromagnet 10, outputs, in the case of the path-2 command, a control current of the signal value Id3 to the kicker electromagnet 10, and outputs, in the case of the path-3 command, a control current of the signal value Id2 to the kicker electromagnet 10. Note that, in FIG. 20, such a case is shown where, when none of the path-1 command, the path-2 command and the path-3 command is outputted, the signal value of the kicker control signal csigd is at a signal level of other than Id1, Id2 and Id3, for example, at zero level. During the time t2 to the time t4, the time t5 to the time t6, and the time t7 to the time t8, the emitter control signal csiga provides the emission command (signal-value H state) and the kicker control signal csigd provides the path-1 command (signal-value Id1 state), so that, in the particle beam therapy system 51 of Embodiment 4, the charged particle beam 81 is emitted and the irradiation current Ibem1 is supplied to the irradiation target 31a of the patient 30a in the treatment room 1 (treatment room 29a). During the time t4 to the time t5, the time t6 to the time t7, and the time t9 to the time t10, the emitter control signal csiga provides the emission command (signal-value H state) and the kicker control signal csigd provides the path-2 command (signal-value Id3 state), so that, in the particle beam therapy system 51 of Embodiment 4, the charged particle beam 81 is emitted and the irradiation current Ibem2 is supplied to the irradiation target 31b of the patient 30b in the treatment room 2 (treatment room 29b). During the time t8 to the time t9, although the emitter control signal csiga provides the emission command (signal-value H state) the kicker control signal csigd provides the path-3 command (signal-value Id2 state), so that, in the particle beam therapy system 51 of Embodiment 4, the charged particle beam 81 is shut off by the damper 11. The particle beam therapy system 51 of Embodiment 4 achieves the same effect as in Embodiment 2. The particle beam therapy system 51 of Embodiment 4 includes the beam-path controller 64 that generates the kicker control signal csigd and the emitter control signal csiga, by use of the time-sharing signal ssiga with a cycle shorter than that of the time-sharing signal ssig in Embodiment 2; and can supply the irradiation current with a short time width to the irradiation target 31 of the patient 30 with respect to the treatment room from which an irradiation request is issued and which is designated by the time-sharing signal ssiga, when the mask signal msig provides the mask canceling command (signal-value L state). Describing more specifically, as shown from the time t3 to the time t8 in FIG. 20, when the mask signal msig provides the mask cancelling command (signal-value L state) and the respiratory gate signal gsig1 and the respiratory gate signal gsig2 are simultaneously in “ON” state, the beam-path controller 64 causes the path command provided in the kicker control signal csigd to change plural times in a short time period, so that the irradiation current with a short time width can be supplied to the irradiation target 31 of the patient 30. The particle beam therapy system 51 of Embodiment 4 an supply the irradiation current with a time width shorter than that in Embodiment 2 to the irradiation target 31 of the patient 30; such a method of rapidly switching the beam path as in Embodiment 4 is profitable in the case, like repainting irradiation, where irradiation is performed plural times while decreasing each irradiation dose (the number of particles subjected to irradiation per a specified time period), namely, in the case of irradiation in a manner like that, in pictorial art, a light-colored paint is repeatedly painted. It is noted that, in FIG. 20, such a case is shown where the number of the respiratory gate signals is two; instead, in the case where the number of the respiratory gate signals is three, the mask signal msig will be given as follows. The mask signal msig provides the masking command in a case where all of the respiratory signals are “OFF” and in each of three cases where only one of the respiratory gate signals becomes “ON”, that is, in total four cases. The mask signal msig provides the mask cancelling command in a case where the three respiratory gate signals gsig1, gsig2, gsig3 are simultaneously “ON” and in each of cases (three cases) where two respiratory gate signals in the three respiratory gate signals are simultaneously “ON”, that is, in total four cases. Thus, the particle beam therapy system 51 of Embodiment 4 can be applied also in a case where the number of the respiratory gate signals is three or more. Meanwhile, in the case where the number of the respiratory gate signals is three or more, the number of treatment rooms for which the charged particle beam 81 is controlled to be switched in a short time may be limited to two. Further, in the cycle Tc2 of the time-sharing signal ssiga, a time period allocated to each of the treatment rooms 29 for its selection is not limited to the case where it is evenly set, and may be set arbitrarily. In Embodiment 3, such a case has been shown where, when irradiation requests from the plurality of treatment rooms 29 are overlapping, the charged particle beam 81 is controlled to be switched between toward the respective corresponding treatment rooms 1, 2 (treatment rooms 29a, 29b) in a short time, by use of the time-sharing signal ssiga with the cycle Tc2 that is shorter than that in Embodiment 1 and the mask signal msig for masking the treatment-room selection by the time-sharing signal ssiga. In Embodiment 5, such a case will be described where the charged particle beam 81 is controlled to be switched between toward the plurality of treatment rooms 29 in a short time without using the mask signal msig, and an irradiation current with a short time width is supplied to one of the treatment rooms 29. FIG. 21 is a configuration diagram showing a particle beam therapy system according to Embodiment 5 of the invention, and FIG. 22 is a diagram showing a beam-path controller in FIG. 21. FIG. 23 is a timing chart illustrating a beam distribution to a plurality of treatment rooms according to Embodiment 5 of the invention. When irradiation requests from the plurality of treatment rooms 29 are overlapping, for example, when the respiratory gate signal gsig1 for the treatment room 1 is in “ON” state and the respiratory gate signal gsig2 for the other treatment room 2 is in “ON” state, the particle beam therapy system 51 of Embodiment 5 controls so as to make switching of the charged particle beam 81 between toward the respective corresponding treatment rooms 1, 2 (treatment rooms 29a, 29b) in a short time. Further, when an irradiation request from only one of the treatment rooms 29 is issued, the particle beam therapy system 51 of Embodiment 5 controls to make ON-OFF switching of the emitter control signal csiga in a short time, to thereby make switching of the charged particle beam 81 for the corresponding treatment room 29 in a short time. In other words, the particle beam therapy system 51 of Embodiment 5 is a particle beam therapy system that performs switching in a short time between emission of the beam from the emitter 62 and stopping of that beam, and performs switching of the path between toward the respective treatment rooms 29 in a short time by the beam-path changer 16. The treatment management device 95 in Embodiment 5 includes, like in Embodiment 3, a beam-path controller 65 that outputs a kicker control signal csigb whose signal value varies in a time period shorter than in Embodiment 1. The beam-path controller 65 includes: an emitter control-signal generator 57 for generating an emitter control signal csiga; a kicker control-signal generator (beam-path changer control-signal generator) 50 for generating the kicker control signal csigb; and a control signal generator 35 for outputting a plurality of control signals to the emitter control-signal generator 57 and the kicker control-signal generator 50. The control signal generator 35 includes: a time-sharing signal generator 45 for generating a time-sharing signal ssiga with a cycle of Tc2 that is shorter than that in Embodiment 1; and a respiratory gate-signal generator 34 for generating the respiratory gate signals gsig1, gsig2. As shown in FIG. 23, the time-sharing signal generator 45 generates the time-sharing signal ssiga with the cycle Tc2 that is shorter than the cycle Tc1 in Embodiment 1. Operations of the particle beam therapy system 51 of Embodiment 5 will be described using FIG. 23. In FIG. 23, the abscissa represents time t. Each ordinate for the time-sharing signal ssiga, the respiratory gate signals gsig1, gsig2, the emitter control signal csiga, and the kicker control signal csigb represents a signal value of each of these signals, and each ordinate for the irradiation currents Ibem1, Ibem2 represents a current value. Note that, in order not to complicate the figure, illustrated here is a case where the time-sharing signal ssiga selects the treatment room 1 and the treatment room 2 at its H level and L level, respectively. When the time-sharing signal ssiga is at H level, the treatment room 1 is designated, and when the time-sharing signal ssiga is at L level, the treatment room 2 is designated. Note that the time-sharing signal ssiga can be constituted in a form of the time-sharing signals ssig-1, ssig-2 and ssig-3 shown in FIG. 7. The emitter control-signal generator 57 receives the respiratory gate signals gsig1, gsig2 and the time-sharing signal ssiga, to thereby generate the emitter control signal csiga as follows. First of all, with respect to the emission command (signal-value H state) for ordering the emitter 62 to emit the charged particle beam 81, the following four cases arise. When only one of the respiratory gate signals (respiratory gate signal gsig1 or respiratory gate signal gsig2) is “ON” (signal-value H state), the time-sharing signal ssiga designates the treatment room 1, and the respiratory gate signal gsig1 for the treatment room 1 is “ON” (signal-value H state) (First Case), the emitter control-signal generator 57 outputs the emission command (signal-value H state) for ordering the emitter 62 to emit the charged particle beam 81. Further, when only one of the respiratory gate signals (respiratory gate signal gsig1 or respiratory gate signal gsig2) is “ON” (signal-value H state), the time-sharing signal ssiga designates the treatment room 2, and the respiratory gate signal gsig2 for the treatment room 2 is “ON” (signal-value H state) (Second Case), the emitter control-signal generator 57 outputs the emission command (signal-value H state) for ordering the emitter 62 to emit the charged particle beam 81. Further, when the plurality of respiratory gate signals (respiratory gate signal gsig1 and respiratory gate signal gsig2) are “ON” (signal-value H state), the time-sharing signal ssiga designates the treatment room 1, and the respiratory gate signal gsig1 for the treatment room 1 is “ON” (signal-value H state) (Third Case), the emitter control-signal generator 57 outputs the emission command (signal-value H state) for ordering the emitter 62 to emit the charged particle beam 81. Further, when the plurality of respiratory gate signals (respiratory gate signal gsig1 and respiratory gate signal gsig2) are “ON” (signal-value H state), the time-sharing signal ssiga designates the treatment room 2, and the respiratory gate signal gsig2 for the treatment room 2 is “ON” (signal-value H state) (Fourth Case), the emitter control-signal generator 57 outputs the emission command (signal-value H state) for ordering the emitter 62 to emit the charged particle beam 81. In other than the above four cases, the emitter control-signal generator 57 outputs the emission stop command (signal-value L state) for ordering the emitter 62 to stop emission of the charged particle beam 81. In FIG. 23, the period from the time t2 to the time t3, the period from the time t4 to the time t5, the period from the time t6 to the time t7, the period from the time t8 to the time t13, the period from the time t14 to the time t15, the period from the time t16 to the time t17 and the period from the time t18 to the time t19 are each a period where the emission command of the charged particle beam 81 is outputted. The kicker control-signal generator 50 receives the respiratory gate signals gsig1, gsig2, and the time-sharing signal ssiga, to thereby generate the kicker control signal csigb as follows. In FIG. 23, when only one respiratory gate signals is “ON” (signal-value H state), namely, only the respiratory gate signal gsig1 is “ON” (signal-value H state), the kicker control-signal generator 50 outputs a path-1 command (signal-value Ib1 state) for ordering switching of the path so that the charged particle beam 81 is guided to the treatment room 1 (treatment room 29a). Further, when only the other one respiratory gate signal is “ON” (signal-value H state), namely, only the respiratory gate signal gsig2 is “ON” (signal-value H state), the kicker control-signal generator 50 outputs a path-2 command (signal-value Ib2 state) for ordering switching of the path so that the charged particle beam 81 is guided to the treatment room 2 (treatment room 29b). Meanwhile, when the plurality of respiratory gate signals (respiratory gate signal gsig1 and respiratory gate signal gsig2) are “ON” (signal-value H state), the time-sharing signal ssiga designates the treatment room 1, and the respiratory gate signal gsig1 for the treatment room 1 is “ON” (signal-value H state), the kicker control-signal generator 50 outputs the path-1 command (signal-value Ib1 state) for ordering switching of the path so that the charged particle beam 81 is guided to the treatment room 1 (treatment room 29a). Further, when the plurality of respiratory gate signals (respiratory gate signal gsig1 and respiratory gate signal gsig2) are “ON” (signal-value H state), the time-sharing signal ssiga designates the treatment room 2, and the respiratory gate signal gsig2 for the treatment room 2 is “ON” (signal-value H state), the kicker control-signal generator 50 outputs the path-2 command (signal-value Ib2 state) for ordering switching of the path so that the charged particle beam 81 is guided to the treatment room (treatment room 29b). The kicker control-signal generator 50 outputs, in the case of the path-1 command, a control current of the signal value Ib1 to the kicker electromagnet 10, and outputs, in the case of the path-2 command, a control current of the signal value Ib2 to the kicker electromagnet 10. Note that, in FIG. 23, such a case is shown where, when neither the path-1 command nor the path-2 command is outputted, the signal value of the kicker control signal csigb is at a signal level of other than Ib1 and also other than Ib2, for example, at zero level. In each of periods from the time t2 to the time t3, from the time t4 to the time t5, from the time t6 to the time t7, from the time t8 to the time t9, from the time t10 to the time 11 and from the time t12 to the time t13, the emitter control signal csiga provides the emission command (signal-value H state) and the kicker control signal csigb provides the path-1 command (signal-value Ib1 state), so that, in the particle beam therapy system 51 of Embodiment 5, the charged particle beam 81 is emitted and the irradiation current Ibem1 is supplied to the irradiation target 31a of the patient 30a in the treatment room 1 (treatment room 29a). In each of periods from the time t9 to the time t10, from the time t11 to the time t12, from the time t14 to the time t15, from the time t16 to the time t17 and from the time t18 to the time t19, the emitter control signal csiga provides the emission command (signal-value H state) and the kicker control signal csigb provides the path-2 command (signal-value Ib2 state), so that, in the particle beam therapy system 51 of Embodiment 5, the charged particle beam 81 is emitted and the irradiation current Ibem2 is supplied to the irradiation target 31b of the patient 30b in the treatment room 2 (treatment room 29b). The particle beam therapy system 51 of Embodiment 5 achieves the same effect as in Embodiment 1. The particle beam therapy system 51 of Embodiment 5 includes the beam-path controller 65 that generates the kicker control signal csigb and the emitter control signal csiga, by use of the time-sharing signal ssiga with a cycle shorter than that of the time-sharing signal ssig in Embodiment 1; and can supply the irradiation current with a short time width to the irradiation target. 31 of the patient 30 with respect to the treatment room from which an irradiation request is issued and which is designated by the time-sharing signal ssiga. Describing more specifically, as shown from the time t8 to the time t13 in FIG. 23, when the respiratory gate signal gsig1 and the respiratory gate signal gsig2 are simultaneously in “ON” state, the beam-path controller 65 causes the path command provided in the kicker control signal csigb to change plural times in a short time period; and, as shown from the time t2 to the time t8 and from the time t13 to the time t19, when only one respiratory gate signal is “ON” (signal-value H state), the emitter control signal csiga is subjected to ON-OFF switching with the same cycle Tc2 as that of the time-sharing signal ssiga; so that the irradiation current with a short time width can be supplied to the irradiation target 31 of the patient 30. Like Embodiment 3, the particle beam therapy system 51 of Embodiment 5 can supply the irradiation current with a time width shorter than that in Embodiment 1 to the irradiation target 31 of the patient 30; such a method of rapidly switching the beam path as in Embodiment 5 is profitable in the case, like repainting irradiation, where irradiation is performed plural times while decreasing each irradiation dose (the number of particles subjected to irradiation per a specified time period), namely, in the case of irradiation in a manner like that, in pictorial art, a light-colored paint is repeatedly painted. Because of no use of the mask signal msig, the particle beam therapy system 51 of Embodiment 5 has such a merit that the control signal generator 35 is simplified in its control as compared to Embodiment 3. It is noted that, in FIG. 23, such a case is shown where the number of the respiratory gate signals is two; however, the particle beam therapy system 51 of Embodiment 5 can be applied also in a case where the number of the respiratory gate signals is three or more. Further, in the cycle Tc2 of the time-sharing signal ssiga, a time period allocated to each of the treatment rooms 29 for its selection is not limited to the case where it is evenly set, and may be set arbitrarily. In Embodiment 5, such a case has been shown where, in the particle beam therapy system 51 not provided with the damper 11 in the beam transport system 59, the charged particle beam 81 is controlled to be switched between toward the plurality of treatment rooms 29 in a short time without using the mask signal msig, and an irradiation current with a short time width is supplied to one of the treatment rooms 29. In Embodiment 6, such a case will be described where, in the particle beam therapy system 51 provided with the damper 11 in the beam transport system 59, the charged particle beam 81 is controlled to be switched between toward the plurality of treatment rooms 29 in a short time without using the mask signal msig, and an irradiation current with a short time width is supplied to one of the treatment rooms 29. FIG. 24 is a configuration diagram showing a particle beam therapy system according to Embodiment 6 of the invention, and FIG. 25 is a diagram showing a beam-path controller in FIG. 24. FIG. 26 is a timing chart illustrating a beam distribution to a plurality of treatment rooms according to Embodiment 6 of the invention. When irradiation requests from the plurality of treatment rooms 29 are overlapping, for example, when the respiratory gate signal gsig1 for the treatment room 1 is in “ON” state and the respiratory gate signal gsig2 for the other treatment room 2 is in “ON” state, the particle beam therapy system 51 of Embodiment 6 controls so as to make switching of the charged particle beam 81 between toward the respective corresponding treatment rooms 1, 2 (treatment rooms 29a, 29b) in a short time. Further, when an irradiation request from only one of the treatment rooms 29 is issued, the particle beam therapy system 51 of Embodiment 6 controls to make switching between the path toward the corresponding treatment room 29 and the path toward the damper 11 in a short time. In other words, the particle beam therapy system 51 of Embodiment 6 is a particle beam therapy system that performs switching between the paths toward the plurality of treatment rooms 29 and switching between the paths toward the one treatment room 29 and toward the damper 11, in a short time by the beam-path changer 16. The treatment management device 95 in Embodiment 6 includes a beam-path controller 66 that outputs a kicker control signal csigd whose signal value varies in a time period shorter than in Embodiment 2. The beam-path controller 66 includes: an emitter control-signal generator 57 for generating an emitter control signal csiga; a kicker control-signal generator 69 for generating the kicker control signal csigd; and a control signal generator 35 for outputting a plurality of control signals to the emitter control-signal generator 57 and the kicker control-signal generator 69. The control signal generator 35 includes: a time-sharing signal generator 45 for generating a time-sharing signal ssiga with a cycle of Tc2 that is shorter than that in Embodiment 2; and a respiratory gate-signal generator 34 for generating the respiratory gate signals gsig1, gsig2. As shown in FIG. 26, the time-sharing signal generator 45 generates the time-sharing signal ssiga with the cycle Tc2 that is shorter than the cycle Tc1 in Embodiment 2. Operations of the particle beam therapy system 51 of Embodiment 6 will be described using FIG. 26. In FIG. 26, the abscissa represents time t. Each ordinate for the time-sharing signal ssiga, the respiratory gate signals gsig1, gsig2, the emitter control signal csiga, and the kicker control signal csigd represents a signal value of each of these signals, and each ordinate for the irradiation currents Ibem1, Ibem2 represents a current value. Note that, in order not to complicate the figure, illustrated here is a case where the time-sharing signal ssiga selects the treatment room 1 and the treatment room 2 at its H level and L level, respectively. When the time-sharing signal ssiga is at H level, the treatment room 1 is designated, and when the time-sharing signal ssiga is at L level, the treatment room 2 is designated. Note that the time-sharing signal ssiga can be constituted in a form of the time-sharing signals ssig-1, ssig-2 and ssig-3 shown in FIG. 7. The emitter control-signal generator 57 receives the respiratory gate signals gsig1, gsig2 and the time-sharing signal ssiga, to thereby generate the emitter control signal csiga as follows. When at least one of the respiratory gate signals (respiratory gate signal gsig1 or respiratory gate signal gsig2) is “ON” (signal-value H state) (First Case), the emitter control-signal generator 57 outputs the emission command (signal-value H state) for ordering the emitter 62 to emit the charged particle beam 81. In FIG. 26, the period from the time t1 to the time t20 is a period where the emission command of the charged particle beam 81 is outputted. The kicker control-signal generator 69 receives the respiratory gate signals gsig1, gsig2, and the time-sharing signal ssiga, to thereby generate the kicker control signal csigd as follows. As shown from the time t2 to the time t8 and from the time t14 to the time t20 in FIG. 26, when one treatment room 29 for which the respiratory gate signal is being “ON”, is selected by the time-sharing signal ssiga, the kicker control-signal generator 69 outputs a path command (radiation-permissive path command) for ordering switching of the path so that the particle beam 81 is guided to the corresponding treatment room 29, while, when the other treatment room 29 is selected by the time-sharing signal ssiga, the kicker control-signal generator 69 outputs another path command (path shutoff command) for ordering switching of the path so that the particle beam 81 is guided to the damper 11. Further, this similarly applies also to the case where the plurality of respiratory gate signals are “ON” (signal-value H state), so that, when the treatment room 29 for which the respiratory gate signal is being “ON”, is selected by the time-sharing signal ssiga, the kicker control-signal generator 69 outputs a path command (radiation-permissive path command) for ordering switching of the path so that the particle beam 81 is guided to the corresponding treatment room 29, while, when the other treatment room 29 is selected by the time-sharing signal ssiga, the kicker control-signal generator 69 outputs another path command (radiation-permissive path command) for ordering switching of the path so that the particle beam 81 is guided to the corresponding treatment room 29. When such a situation continues where, even for any one of the different treatment rooms, the respiratory gate signal is “ON” (signal-value H state) and the corresponding treatment room 29 for which the respiratory gate signal is “ON” (signal-value H state) is selected by the time-sharing signal ssiga, the kicker control-signal generator 69 outputs the path command (irradiation-permissive path command) for ordering switching of the path so that the charged particle beam 81 is guided to change from toward one treatment room 29 to toward the other treatment room 29, as shown from the time t8 to the time t12 in FIG. 26. The kicker control signal csigd in FIG. 26 will be described specifically. As shown from the time t1 to the time t8, when only the respiratory gate signal gsig1 is “ON” (signal-value H state), if the time-sharing signal ssiga designates the treatment room 1, the kicker control-signal generator 69 outputs a path-1 command (signal-value Id1 state) for ordering switching of the path so that the charged particle beam 81 is guided to the treatment room 1 (treatment room 29a). Further, when only the respiratory gate signal gsig1 is “ON” (signal-value H state), if the time-sharing signal ssiga designates the other treatment room 2, the kicker control-signal generator 69 outputs a path-2 command (signal-value Id3 state) for ordering switching of the path so that the charged particle beam 81 is guided to the damper 11. During the time t8 to the time t13, irradiation requests from the plurality of treatment rooms 29 are overlapping, and thus, the plurality of respiratory gate signals (respiratory gate signal gsig1 and respiratory gate signal gsig2) are “ON” (signal-value H state). In this overlapping situation of the irradiation requests, when the time-sharing signal ssiga designates the treatment room 1 and the respiratory gate signal gsig1 for the treatment room 1 is “ON” (signal-value H state), the kicker control-signal generator 69 outputs the path-1 command (signal-value Id1 state) for ordering switching of the path so that the charged particle beam 81 is guided to the treatment room 1 (treatment room 29a). Further, in the overlapping situation of the irradiation requests, when the time-sharing signal ssiga designates the treatment room 2 and the respiratory gate signal gsig2 for the treatment room 2 is “ON” (signal-value H state), the kicker control-signal generator 69 outputs the path-2 command (signal-value Id3 state) for ordering switching of the path so that the charged particle beam 81 is guided to the treatment room 2 (treatment room 29b). During the time t13 to the time t20, there is shown a case where only the respiratory gate signal gsig2 is “ON” (signal-value H state). When only the respiratory gate signal gsig2 is “ON” (signal-value H state), if the time-sharing signal ssiga designates the treatment room 2, the kicker control-signal generator 69 outputs the path-2 command (signal-value Id3 state) for ordering switching of the path so that the charged particle beam 81 is guided to the treatment room 2 (treatment room 29b). Further, when only the respiratory gate signal gsig2 is “ON” (signal-value H state), if the time-sharing signal ssiga designates the other treatment room 1, the kicker control-signal generator 69 outputs the path-3 command (signal-value Id2 state) for ordering switching of the path so that the charged particle beam 81 is guided to the damper 11. The kicker control-signal generator 69 outputs, in the case of the path-1 command, a control current of the signal value Id1 to the kicker electromagnet 10, outputs, in the case of the path-2 command, a control current of the signal value Id3 to the kicker electromagnet 10, and outputs, in the case of the path-3 command, a control current of the signal value Id2 to the kicker electromagnet 10. Note that, in FIG. 26, such a case is shown where, when none of the path-1 command, the path-2 command and the path-3 command is outputted, the signal value of the kicker control signal csigd is at a signal level of other than Id1, Id2 and Id3, for example, at zero level. In each of periods from the time t2 to the time t3, from the time t4 to the time t5, from the time t6 to the time t7, from the time t8 to the time t9, from the time t10 to the time t11 and from the time t12 to the time t13, the emitter control signal csiga provides the emission command (signal-value H state) and the kicker control signal csigd provides the path-1 command (signal-value Id1 state), so that, in the particle beam therapy system 51 of Embodiment 6, the charged particle beam 81 is emitted and the irradiation current Ibem1 is supplied to the irradiation target 31a of the patient 30a in the treatment room 1 (treatment room 29a). In each of periods from the time t9 to the time t10, from the time t11 to the time t12, from the time t14 to the time t15, from the time t16 to the time t17 and from the time t18 to the time t19, the emitter control signal csiga provides the emission command (signal-value H state) and the kicker control signal csigd provides the path-2 command (signal-value Id3 state), so that, in the particle beam therapy system 51 of Embodiment 6, the charged particle beam 81 is emitted and the irradiation current Ibem2 is supplied to the irradiation target 31b of the patient 30b in the treatment room 2 (treatment room 29b). In each of periods from the time t1 to the time t2, from the time t3 to the time t4, from the time t5 to the time t6, from the time t7 to the time t8, from the time t13 to the time t14, from the time t15 to the time t16, from the time t17 to the time t18 and from the time t19 to the time t20, although the emitter control signal csiga provides the emission command (signal-value H state), the kicker control signal csigd provides the path-3 command (signal-value Id2 state), so that, in the particle beam therapy system 51 of Embodiment 6, the charged particle beam 81 is shut off by the damper 11. The particle beam therapy system 51 of Embodiment 6 achieves the same effect as in Embodiment 2. The particle beam therapy system 51 of Embodiment 6 includes the beam-path controller 66 that generates the kicker control signal csigd and the emitter control signal csiga, by use of the time-sharing signal ssiga with a cycle shorter than that of the time-sharing signal ssig in Embodiment 1; and can supply the irradiation current with a short time width to the irradiation target 31 of the patient 30 with respect to the treatment room from which an irradiation request is issued and which is designated by the time-sharing signal ssiga. Describing more specifically, as shown from the time t1 to the time t20 in FIG. 26, when at least one of the respiratory gate signals (gsig1, gsig2) is in “ON” state, the beam-path controller 66 performs switching of the beam path by changing plural times the path command (path-1 command, path-2 command, path-3 command) provided in the kicker control signal csigd in a short time; so that the irradiation current with a short time width can be supplied to the irradiation target 31 of the patient 30. According to the particle beam therapy system 51 of Embodiment 6, at the time of supplying the irradiation current with a short time width to the irradiation target 31 of the patient 30 in the designated treatment room, switching of the beam path is made by changing only the beam-path changer 16 plural times in a short time period, without changing the emitter 62 that is slower in ON-OFF switching than the kicker electromagnet 10 in a short time by use of the emitter control signal csiga, so that the irradiation current with a time width shorter than that in Embodiment 5 can be supplied to the irradiation target 31 of the patient 30. Like Embodiment 4, the particle beam therapy system 51 of Embodiment 6 can supply the irradiation current with a time width shorter than that in Embodiment 1 to the irradiation target 31 of the patient 30; such a method of rapidly switching the beam path as in Embodiment 6 is profitable in the case, like repainting irradiation, where irradiation is performed plural times while decreasing each irradiation dose (the number of particles subjected to irradiation per a specified time period), namely, in the case of irradiation in a manner like that, in pictorial art, a light-colored paint is repeatedly painted. Because of no use of the mask signal msig, the particle beam therapy system 51 of Embodiment 6 has such a merit that the control signal generator 35 is simplified in its control as compared to Embodiment 4. It is noted that, in FIG. 26, such a case is shown where the number of the respiratory gate signals is two; however, the particle beam therapy system 51 of Embodiment 6 can be applied also in a case where the number of the respiratory gate signals is three or more. Further, in the cycle Tc2 of the time-sharing signal ssiga, a time period allocated to each of the treatment rooms 29 for its selection is not limited to the case where it is evenly set, and may be set arbitrarily. In Embodiments 1 to 6, the description has been made using the case where the kicker electromagnet 10 is used as the beam-path changer 16; however, in place of the kicker electromagnet 10, a beam deflector 15 to be described later may be used. Here, since the kicker electromagnet 10 includes a small deflectable angle for deflecting the charged particle beam 81, such a requirement is imposed that the bending magnet 12e for constituting the beam path has to be placed to stay away from the kicker electromagnet 10 at the downstream side thereof. This requirement may become a bottleneck when the particle beam therapy system is to be designed compact. Accordingly, in Embodiment 7, such a case will be shown where the beam deflector 15 is used, thereby to achieve rapid switching of the beam path and to allow the particle beam therapy system to be designed compact. FIG. 27 is a configuration diagram showing a particle beam therapy system according to Embodiment 7 of the invention, and FIG. 28 is a diagram showing a beam-path controller in FIG. 27. FIG. 29 is a side view showing a beam deflector in FIG. 27, and FIG. 30 is a top view of the beam deflector in FIG. 27, viewed from its upper side. FIG. 31 is a diagram illustrating a micro-strip line in the beam deflector in FIG. 27, and FIG. 32 is a diagram illustrating a beam control by the beam deflector in FIG. 27. FIG. 33 is a timing chart illustrating a beam distribution to a plurality of treatment rooms according to Embodiment 7 of the invention. The particle beam therapy system 51 of Embodiment 7 differs from that of Embodiment 1 in that the beam deflector 15 is used as the beam-path changer 16 and the treatment management device 95 includes a beam-path controller 67 that outputs a beam-deflector control signal csigc (beam-path changer control signal) for controlling the beam deflector 15. The beam-path controller 67 includes: a time-sharing signal generator 33 for generating the time-sharing signal ssig; a respiratory gate-signal generator 34 for generating the respiratory gate signals gsig1, gsig2; an emitter control-signal generator 36 for generating the emitter control signal csiga; and a beam-deflector control-signal generator (beam-path changer control-signal generator) 48 for generating the beam-deflector control signal csigc. The time-sharing signal generator 33 and the respiratory gate-signal generator 34 constitute a control signal generator 35. The beam-deflector control-signal generator 48 includes a pulse controller 41, a high-speed switch 42 and a deflector power source 43. Configurations of the beam deflector 15 and the beam-deflector control-signal generator 48 are disclosed in Japanese Patent Application Laid-open No. 2012-024254. Before describing them in detail using FIG. 28 to FIG. 32, a summary thereof will be described. A beam deflector 15 disclosed in Japanese Patent Application Laid-open No. 2012-024254 includes, for the purpose of suppressing a transient dose at the time of shutting off the beam in a scanning irradiation method to thereby improve an accuracy in irradiation dose: a line electrode plate 74 in which a plurality of conductive plates 77a to 77f are placed so that a traverse direction of each of them is arranged along the beam traveling direction; and an electrode plate 76 placed in parallel to the line electrode plate 74. In the beam deflector 15 disclosed in Japanese Patent Application Laid-open No. 2012-024254, there is included a passing region between the line electrode plate 74 and the electrode plate 76 through which the charged particle beam 81 passes. The plurality of the conductive plates 77a to 77f are serially connected in their longitudinal directions and are subjected to impedance matching. A beam-deflector control device (beam-deflector control-signal generator 48) is configured to output a voltage pulse 97 whose transmission base time is synchronized with a particle-movement base time, said transmission base time being a transmission cycle in which the voltage pulse is transmitted through each of the plurality of conductive plates 77a to 77f in the longitudinal direction, and said particle-movement base time being a passing cycle in which the charged particle beam 81 passes through each of the plurality of conductive plates 77a to 77f in the traverse direction. The voltage pulse 97 corresponds to the beam-deflector control signal csigc. For the conductive plates, numeral 77 is used collectively, and this numeral is used as being suffixed with each of “a” to “f” when they are to be described distinctively. The beam deflector 15 includes the line electrode plate 74 and the electrode plate 76 opposite to the line electrode plate 74. The line electrode plate 74 is an electrostatic electrode plate of a micro-strip line type. The line electrode plate 74 is provided by placing the plurality of conductive plates 77, such as copper plates or the like, in parallel on a front face of a base plate 78, such as a GFRP (glass fiber reinforced plastics) plate or the like, and by placing a backside conductor 75, such as a copper plate or the like, on a back face of the base plate 78. The backside conductor 75 is placed at a ground level (connected to GND), the electrode plate 76 is connected to a DC power source (direct-current power source) 79, and the voltage pulse 97 is transmitted through each of the conductive plates 77a to 77f of the line electrode plate 74. The electrode plate 76 and the line electrode plate 74 are placed in parallel relative to an incident beam axis of the charged particle beam 81. The beam deflector 15 includes a passing region between the line electrode plate 74 and the electrode plate 76 through which the charged particle beam 81 passes. When the voltage pulse 97 is not inputted to the line electrode plate 74, namely, when a voltage at the ground level is applied thereto, the charged particle beam 81 is deflected due to the respective electric fields E1 to E6 established between the electrode plate 76 and the line electrode plate 74 (the direction is from the electrode plate 76 to the line electrode plate 74). When the voltage pulse 97 is inputted to the line electrode plate 74, this acts to cancel the respective electric fields E1 to E6 otherwise established between the electrode plate 76 and the line electrode plate 74, so that the charged particle beam 81 goes straightforward. The electric field E1 is an electric field between the conductive plate 77a and the electrode plate 76. Likewise, the electric fields E2 to E6 are electric fields respectively between the conductive plates 77b to 77f and the electrode plate 76. Note that in FIG. 29, the line electrode plate 74 and the electrode plate 76 are each shown as its cross section. A deflection angle at which the charged particle beam 81 is deflected by the beam deflector 15, is determined by the respective electric fields E1 to E6 established between the electrode plate 76 and the line electrode plate 74. Let's assume the case where a voltage of Vb is applied by the DC power source 79 to the electrode plate 76. When the voltage Vp of the voltage pulse 97 applied to the line electrode plate 74 is Vb (Vp=Vb), the charged particle beam 81 is not deflected, so that the charged particle beam 81 results in a straightforward beam 71, thus passing through the beam deflector 15 along the incident beam axis. When the voltage Vp of the voltage pulse 97 applied to the line electrode plate 74 is a voltage at the ground level (0 V) (Vp=0), the charged particle beam 81 is deflected, so that the charged particle beam 81 results in a deflection beam 70, thus passing through the beam deflector 15 while being deflected from the incident beam axis. When the voltage Vp of the voltage pulse 97 applied to the line electrode plate 74 is more than 0 V but less than Vb (0<Vp<Vb), the charged particle beam 81 passes through the beam deflector 15 on a path between the deflection beam 70 and the straightforward beam 71. Note that, when the voltage Vp of the voltage pulse 97 applied to the line electrode plate 74 is a voltage higher than Vb, the charged particle beam 81 passes through the beam deflector 15 on a path deflected upward from the straightforward beam 71. As described above, by transmitting the voltage pulse 97 with an arbitrary voltage Vp to the line electrode plate 74, it is possible to deflect the charged particle beam 81 at an arbitrary deflection angle. In the line electrode plate 74, as shown in FIG. 31, the conductive plates 77a to 77f, each having a width of W, a length of L1 (see, FIG. 30) and a thickness of h1, are placed in an exposed manner on the base plate 78 having a thickness of h2. Since the line electrode plate 74 is provided with a micro-strip line structure, based on a principle of impedance matching (impedance matching adjustment) between micro-strip lines, the conductive plates 77a to 77f have each a predetermined impedance (for example, 50Ω). Further, as shown in FIG. 30, the conductive plates 77a to 77f are placed as being spaced apart to each other by an interval S. Here, assuming that the dielectric constant of the base plate 78 is ∈r, the characteristic impedance Z0 of the micro strip line is represented as shown in a formula (1).Z0=87/(∈r+1.41)1/2×In(A/B) (1) Note that A and B are represented as shown in a formula (2) and a formula (3), respectively.A=5.98×(h2−h1) (2)B=0.8×W×h1 (3) By making selection on the dielectric constant ∈r, the width W, the thickness h1 and the thickness h2, a given impedance (for example, 50Ω) can be obtained. As shown in FIG. 30, the six conductive plates 77a to 77f of the line electrode plate 74 are connected to each other via respective delay lines 99 (99a to 99e) so that they are serially connected to constitute a single transmission line. For the delay lines, numeral 99 is used collectively, and this numeral is used as being suffixed with each of “a” to “e” when they are to be described distinctively. To the conductive plate 77a, an input line 98 for introducing the voltage pulse 97 thereto is connected, and to the terminal end of the conductive plate 77f, a terminal resistance 103 with its one end being grounded is connected. The respective conductive plates 77a to 77f of the line electrode plate 74 have each a given impedance (for example, 50Ω) and are grounded at the terminal end via the terminal resistance 103 for impedance matching, so that the voltage pulse 97 resulting from switching and inputted to the line electrode plate 74 can be transmitted in the line electrode plate 74 without causing reflection. Note that the impedance of each of the delay lines 99 (99a to 99e) and the terminal resistance 103 is made equal to the impedance of each of the conductive plates 77a to 77f. Meanwhile, the delay lines 99a to 99e may be formed, like a printed wiring, on the base plate 78 using a lithography technology or a multi-layer interconnection technology. When the delay lines 99a to 99e are formed on the base plate 78, a soldering work, etc. for bonding the delay lines 99a to 99e becomes unnecessary, so that it is possible to easily perform adjustment of impedance in the line electrode plate 74. How to control traveling of the charged particle beam 81 by the beam deflector 15 will be described in detail. Since the charged particle beam 81 is a flux of plural charged particles 96 (referred to as particle (s) 96, as appropriate), the line electrode plate 74 is configured so that a predetermined synchronous relationship to be described later is established between a time period in which one of the particles 96 passes through the conductive plate 77 in its traverse direction (shorter-side length) and a time period in which the voltage pulse 97 passes through the conductive plate 77 in its longitudinal direction (longer-side length), and thus, only a particle group influenced by the voltage pulse 97 at the first conductive plate 77a is to be influenced also by the voltage pulse 97 at each of the next conductive plates 77b to 77f. This makes the particle group corresponding to the width (time width) of the voltage pulse resulting from switching by the voltage Vb, not to be influenced by the electric field E at the time the particle group is incident to the line electrode plate 74, so that it is possible to cause the beam to go straightforward. Further, when the voltage Vp of the voltage pulse 97 is set to other than Vb, it is possible to deflect the beam. Let's assume the case where the particle 96 passes through the center along the line electrode plate 74. This is because, while paying attention to a center component of the beam, the beam is put in use after being adjusted so that the center component passes through the line electrode plate 74. When the velocity of the particle 96 is defined as v1, a time period in which the particle 96 passes through the conductive plate 77 is W/v1. A time period (particle-movement base time) TP0 in which the particle 96 passes through the conductive plate 77 in the traverse direction (shorter-side length) to reach the next conductive plate 77, is (W+S)/v1. When the velocity of the voltage pulse 97 transmitted through the conductive plate 77 having a predetermined transmission characteristic is defined as v2, a time period in which the voltage pulse 97 passes through the conductive plate 77 in the longitudinal direction (longer-side length) is L1/v2. Meanwhile, based on a propagation delay time TD of the delay line 99, its effective length L2 that corresponds to the longitudinal length of the conductive plate 77 is adopted here. The effective length L2 can be calculated by v2×TD. A time period in which the pulse passes through the first conductive plate 77 and then passes through the delay line 99, namely, a time period (transmission base time) TV0 in which the pulse passes through the first conductive plate 77 to reach the next conductive plate 77, is given as (L1+L2)/v2. The line electrode plate 74 is configured so that the particle-movement base time TP0 and the transmission base time TV0 are matched to each other. This achieves the above predetermined synchronous relationship, so that, as described above, the particle group corresponding to the width (time width) of the voltage pulse resulting from switching by the voltage Vb, is not influenced by the electric field E at the time it is incident to the line electrode plate 74, thus making it possible to cause the beam to go straightforward. Note that the particle-movement base time TP0 is a passing cycle in which the charged particle beam 81 passes through each of the plurality of conductive plates 77a to 77f in the traverse direction, and the transmission base time TV0 is a transmission cycle in which the pulse passes through each of the conductive plates 77a to 77f in the longitudinal direction. Description will be made about the velocity v1 of the particle 96 and the transmission velocity v2 of the voltage pulse 97 that are required to achieve the above predetermined synchronous relationship in which the particle-movement base time TP0 and the transmission base time TV0 are matched to each other. The velocity v1 of the particle 96 and the transmission velocity v2 of the voltage pulse 97 are represented as shown in a formula (4) and a formula (5), respectively.v1=c×√(1−(Es/(Es+K))2) (4)v2=1/√(L×C) (5) Here, “K” represents energy (MeV) of the particle 96, “c” represents the light velocity, “Es” represents the static energy of a proton, “L” represents the inductance of the conductive plate 77 and “C” represents the electric capacitance of the conductive plate 77. Description will be made about the electric field E to be applied using the beam deflector 15 to the charged particle beam 81. FIG. 32 is a diagram illustrating a condition for calculating the electric field E. Indicated at 72 is a straightforward-beam parallel axis that is parallel to the straight beam 71 that is the charged particle beam 81 passing through the beam deflector 15. A point “P” is an evaluation point at which a deflected distance d of the charged particle beam 81 is evaluated, and which corresponds, for example, to an entrance point into the bending magnet 12e in the downstream beam-transport system 24a. The length of the line electrode plate 74 is defined as L4, and the distance on the straightforward-beam parallel axis from the front end of the line electrode plate 74 to the evaluation point P is defined as L3. At the terminal end of the line electrode plate 74, although the charged particle 96 has a velocity component of v1 in the direction of the straightforward-beam parallel axis, the charged particle beam 96 affords, upon being influenced by the electric field E, a component vertical to the line electrode plate 74. The vertical component (vertical velocity component) in the velocity of the charged particle 96 is defined as vb. Further, an angle by a deflection beam trajectory 73 and the straightforward-beam parallel axis 72 is defined as α. The vertical velocity component vb of the charged particle 96 is v1×tan α, so that it is represented as shown in a formula (6).vb=v1×d/(L3−L4) (6) Let's assume a potential difference Vd required for the charged particle 96 to have the vertical velocity component vb at the terminal end of the line electrode plate 74. When the mass of proton is defined as m1 and an electric charge thereof is defined as q, the kinetic energy is ½×m1×vb2 at the terminal end of the line electrode plate 74 and the energy afforded by the charged particle 96 due to the potential difference Vd is q×Vd, so that the potential difference V is represented as shown in a formula (7).Vd=(½×m1×vb2)/q (7) The potential difference Vd required at the terminal end of the line electrode plate 74 is to be shared by an n1 number of the respective conductive plates 77 in the line electrode plate 74. Namely, it suffices to develop the electric field E between the n1 number of the conductive plates 77 in the line electrode plate 74 and the electrode plate 76 so that the charged particle 96 is subjected to a potential difference of Vd/n1 per one of the conductive plates 77. When the particle passes through the width W of the conductive plate 77, the time period taken to pass through the width W is v1/W, so that a moving distance da in the direction vertical to the line electrode plate 74 is represented as shown in a formula (8).da=(vb/n1)×(W/v1) (8) Accordingly, since the electric field E to be applied to the charged particle beam 81 in the beam deflector 15 is (Vd/n1)/da, when the formulae (7), (8) are assigned thereto followed by being subjected to arrangement, it is represented as shown in a formula (9).E=(½×m1×vb×v1)/(q×W) (9) When the formula (6) is assigned to the formula (9) followed by being subjected to arrangement, the electric field E is represented as shown in a formula (10).E=m1×d×v12/(2×q×W×(L3−L4)) (10) Operations of the particle beam therapy system 51 of Embodiment 7 will be described using FIG. 33. Description will be made about part of operations which differs from Embodiment 1. In FIG. 27, a beam transport system 59 is configured so that the charged particle beam 81 to be transported to the treatment room 1 (treatment room 29a) is deflected by the beam deflector 15 so as to be directed toward the bending magnet 12e, while the charged particle beam 81 to be transported to the treatment room 2 (treatment room 29b) goes straightforward without being deflected by the beam deflector 15 so as to be directed toward the bending magnet 12g. When the time-sharing signal ssig designates the treatment room 1 (treatment room 29a), the beam-path controller 67 outputs a path-1 command (signal-value Vc1 state) for ordering switching of the path so that the charged particle beam 81 is guided to the treatment room 1 (treatment room 29a). When the time-sharing signal ssig designates the treatment room 2 (treatment room 29b), the beam-path controller 67 outputs a path-2 command (signal-value Vc2 state) for ordering switching of the path so that the charged particle beam 81 is guided to the treatment room 2 (treatment room 29b). Here, the signal value Vc2 (voltage Vc2) is the voltage Vb applied to the electrode plate 76, and the signal value Vc1 (voltage Vc1) is a voltage lower then Vc2. Although the magnitude relationship between the signal values Vc1, Vc2 of the beam-deflector control signal csigc is reversed from the magnitude relationship between the signal values Ib1, Ib2 of the kicker control signal csigb in Embodiment 1, as described above, the path-1 command is provided when the beam-deflector control signal csigc has the signal value Vc1 and the path-2 command is provided when the beam-deflector control signal csigc has the signal value Vc2. Accordingly, the particle beam therapy system 51 of Embodiment 7 operates similarly to in Embodiment 1. According to the beam deflector 15, the deflection angle can be made larger than that by the kicker electromagnet 10, so that it is possible to make the distance from the beam deflector 15 to the bending magnet 12e shorter than that in Embodiment 1. In the particle beam therapy system 51 of Embodiment 7, the beam transport system 59 that is more compact than that in Embodiment 1 can be configured. The particle beam therapy system 51 of Embodiment 7 achieves the same effect as in Embodiment 1. Further, the particle beam therapy system 51 of Embodiment 7 is configured to use the beam deflector 15 in place of the kicker electromagnet 10 in Embodiment 1. With such a configuration, it is possible to switch the beam path faster and to make the deflection angle larger, than that by the kicker electromagnet 10, so that the particle beam therapy system can be designed compact while achieving rapid switching of the beam path. In Embodiment 8, such a case will be shown where, in the particle beam therapy system 51 of Embodiment 2 provided with the damper 11 in the beam transport system 59, the beam deflector 15 is used, thereby to achieve rapid switching of the beam path and to allow the particle beam therapy system to be designed compact. FIG. 34 is a configuration diagram showing a particle beam therapy system according to Embodiment 8 of the invention, and FIG. 35 is a diagram showing a beam-path controller in FIG. 34. FIG. 36 is a timing chart illustrating a beam distribution to a plurality of treatment rooms according to Embodiment 8 of the invention. The particle beam therapy system 51 of Embodiment 8 differs from that of Embodiment 2 in that the beam deflector 15 is used as the beam-path changer 16 and the treatment management device 95 includes a beam-path controller 68 that outputs a beam-deflector control signal csige (beam-path changer control signal) for controlling the beam deflector 15. The beam-path controller 68 includes: a time-sharing signal generator 33 for generating the time-sharing signal ssig; a respiratory gate-signal generator 34 for generating the respiratory gate signals gsig1, gsig2; an emitter control-signal generator 39 for generating the emitter control signal csiga; and a beam-deflector control-signal generator (beam-path changer control-signal generator) 49 for generating the beam-deflector control signal csige. The time-sharing signal generator 33 and the respiratory gate-signal generator 34 constitute a control signal generator 35. The beam-deflector control-signal generator 49 includes a pulse controller 41, a high-speed switch 42 and a deflector power source 43. The pulse controller 41 in Embodiment 8 receives the respiratory gate signals gsig1, gsig2 and the time-sharing signal ssig, and outputs a generated control signal to the high-speed switch 42. The high-speed switch 42 generates the beam-deflector control signal csige according to the control signal from the pulse controller 41. Operations of the particle beam therapy system 51 of Embodiment 8 will be described using FIG. 36. Description will be made about part of operations which differs from Embodiment 2. When the time-sharing signal ssig designates the treatment room 1 (treatment room 29a) and the respiratory gate signal gsig1 is “ON”, namely, when the condition for transporting the charged particle beam 81 to the treatment room 1 (treatment room 29a) is established, the beam-path controller 68 outputs a path-1 command (signal-value Ve1 state) for ordering switching of the path so that the charged particle beam 81 is guided to the treatment room 1 (treatment room 29a). When the time-sharing signal ssig designates the treatment room 2 (treatment room 29b) and the respiratory gate signal gsig2 is “ON”, namely, when the condition for transporting the charged particle beam 81 to the treatment room 2 (treatment room 29b) is established, the beam-path controller 68 outputs a path-2 command (signal-value Ve3 state) for ordering switching of the path so that the charged particle beam 81 is guided to the treatment room 2 (treatment room 29b). When the time-sharing signal ssig designates either one of the treatment rooms (treatment room 1, treatment room 2), and the respiratory gate signal (gsig1, gsig2) corresponding to that treatment room is “OFF”, namely, the condition for guiding the charged particle beam 81 to the damper 11 is established, the beam-path controller 68 outputs a path-3 command (signal-value Ve2 state) for ordering switching of the path so that the charged particle beam 81 is guided to the damper 11. Here, the signal value Ve3 (voltage Ve3) is the voltage Vb applied to the electrode plate 76, and the signal value Ve1 (voltage Ve1) and the signal value Ve2 (voltage Ve2) are each a voltage lower than Ve3. Although the magnitude relationship between the signal values Ve1, Ve3 of the beam-deflector control signal csige is reversed from the magnitude relationship between the signal values Id1, Id3 of the kicker control signal csigd in Embodiment 2, as described above, the path-1 command is provided when the beam-deflector control signal csige has the signal value Ve1, the path-2 command is provided when the beam-deflector control signal csige has the signal value Ve3, and the path-3 command is provided when the beam-deflector control signal csige has the signal value Ve2. Accordingly, the particle beam therapy system 51 of Embodiment 8 operates similarly to in Embodiment 2. The particle beam therapy system 51 of Embodiment 8 achieves the same effect as in Embodiment 2. Further, the particle beam therapy system 51 of Embodiment 8 is configured to use, in place of the kicker electromagnet 10 in Embodiment 2, the beam deflector 15 that is able to switch the beam path faster and to make the deflection angle larger, than the kicker electromagnet 10, so that the particle beam therapy system can be designed compact while achieving more rapid switching of the beam path than that in Embodiment 2. In Embodiment 9, such a case will be shown where, in the particle beam therapy system 51 in Embodiment 3 in which, when irradiation requests from the plurality of treatment rooms 29 are overlapping, the charged particle beam 81 is controlled to be switched between toward the respective corresponding treatment rooms 1, 2 (treatment rooms 29a, 29b) in a short time, a beam deflector 15 is used, thereby to achieve rapid switching of the beam path and to allow the particle beam therapy system to be designed compact. FIG. 37 is a configuration diagram showing a particle beam therapy system according to Embodiment 9 of the invention, and FIG. 38 is a diagram showing a beam-path controller in FIG. 37. FIG. 39 is a timing chart illustrating a beam distribution to a plurality of treatment rooms according to Embodiment 9 of the invention. The particle beam therapy system 51 of Embodiment 9 differs from that of Embodiment 3 in that the beam deflector 15 is used as the beam-path changer 16 and the treatment management device 95 includes a beam-path controller 113 that outputs a beam-deflector control signal csigc for controlling the beam deflector 15. The beam-path controller 113 includes: an emitter control-signal generator 46 for generating an emitter control signal csiga; abeam-deflector control-signal generator (beam-path changer control signal generator) 105 for generating a beam-deflector control signal csigc; and a control signal generator 35 for outputting a plurality of control signals to the emitter control-signal generator 46 and the beam-deflector control-signal generator 105. The control signal generator 35 includes: a time-sharing signal generator 45 for generating a time-sharing signal ssiga with a cycle of Tc2 that is shorter than the cycle Tc1; a respiratory gate-signal generator 34 for generating respiratory gate signals gsig1, gsig2; and a mask signal generator 44 for generating a mask signal msig for masking a treatment-room selection by the time-sharing signal ssiga. The beam-deflector control-signal generator 105 includes a pulse controller 41, a high-speed switch 42 and a deflector power source 43. The pulse controller 41 in Embodiment 9 receives the respiratory gate signals gsig1, gsig2, the time-sharing signal ssiga and the mask signal msig, and outputs a generated control signal to the high-speed switch 42. The high-speed switch 42 generates the beam-deflector control signal csigc according to the control signal from the pulse controller 41. Operations of the particle beam therapy system 51 of Embodiment 9 will be described using FIG. 39. Description will be made about part of operations which differs from Embodiment 3. When the condition for transporting the charged particle beam 81 to the treatment room 1 (treatment room 29a) is established, the beam-path controller 113 outputs a path-1 command (signal-value Vc1 state) for ordering switching of the path so that the charged particle beam 81 is guided to the treatment room 1 (treatment room 29a). When the condition for transporting the charged particle beam 81 to the treatment room 2 (treatment room 29b) is established, the beam-path controller 113 outputs a path-2 command (signal-value Vc2 state) for ordering switching of the path so that the charged particle beam 81 is guided to the treatment room 2 (treatment room 29b). Here, the signal values Vc1, Vc2 are just as described in Embodiment 7. The particle beam therapy system 51 of Embodiment 9 operates similarly to in Embodiment 3. The particle beam therapy system 51 of Embodiment 9 achieves the same effect as in Embodiment 3. Further, the particle beam therapy system 51 of Embodiment 9 is configured to use, in place of the kicker electromagnet 10 in Embodiment 3, the beam deflector 15 that is able to switch the beam path faster and to make the deflection angle larger, than the kicker electromagnet 10, so that the particle beam therapy system can be designed compact while achieving more rapid switching of the beam path than that in Embodiment 3. In Embodiment 10, such a case will be shown where, in the particle beam therapy system 51 in Embodiment 4 which is provided with the damper 11 in the beam transport system 59 and in which, when irradiation requests from the plurality of treatment rooms 29 are overlapping, the charged particle beam 81 is controlled to be switched between toward the respective corresponding treatment rooms 1, 2 (treatment rooms 29a, 29b) in a short time, a beam deflector 15 is used, thereby to achieve rapid switching of the beam path and to allow the particle beam therapy system to be designed compact. FIG. 40 is a configuration diagram showing a particle beam therapy system according to Embodiment 10 of the invention, and FIG. 41 is a diagram showing a beam-path controller in FIG. 40. FIG. 42 is a timing chart illustrating a beam distribution to a plurality of treatment rooms according to Embodiment 10 of the invention. The particle beam therapy system 51 of Embodiment 10 differs from that of Embodiment 4 in that the beam deflector 15 is used as the beam-path changer 16 and the treatment management device 95 includes a beam-path controller 114 that outputs a beam-deflector control signal csige for controlling the beam deflector 15. The beam-path controller 114 includes: an emitter control-signal generator 57 for generating an emitter control signal csiga; a beam-deflector control-signal generator (beam-path changer control-signal generator) 106 for generating a beam-deflector control signal csige; and a control signal generator 35 for outputting a plurality of control signals to the emitter control-signal generator 57 and the beam-deflector control-signal generator 106. The control signal generator 35 includes: a time-sharing signal generator 45 for generating a time-sharing signal ssiga with a cycle of Tc2 that is shorter than the cycle Tc1; a respiratory gate-signal generator 34 for generating respiratory gate signals gsig1, gsig2; and a mask signal generator 44 for generating a mask signal msig for masking a treatment-room selection by the time-sharing signal ssiga. The beam-deflector control-signal generator 106 includes a pulse controller 41, a high-speed switch 42 and a deflector power source 43. The pulse controller 41 in Embodiment 10 receives the respiratory gate signals gsig1, gsig2, the time-sharing signal ssiga and the mask signal msig, and outputs a generated control signal to the high-speed switch 42. The high-speed switch 42 generates the beam-deflector control signal csige according to the control signal from the pulse controller 41. Operations of the particle beam therapy system 51 of Embodiment 10 will be described using FIG. 42. Description will be made about part of operations which differs from Embodiment 4. When the condition for transporting the charged particle beam 81 to the treatment room 1 (treatment room 29a) is established, the beam-path controller 114 outputs a path-1 command (signal-value Ve1 state) for ordering switching of the path so that the charged particle beam 81 is guided to the treatment room 1 (treatment room 29a). When the condition for transporting the charged particle beam 81 to the treatment room 2 (treatment room 29b) is established, the beam-path controller 114 outputs a path-2 command (signal-value Ve3 state) for ordering switching of the path so that the charged particle beam 81 is guided to the treatment room 2 (treatment room 29b). When the condition for guiding the charged particle beam 81 to the damper 11 is established, the beam-path controller 114 outputs a path-3 command (signal-value Ve2 state) for ordering switching of the path so that the charged particle beam 81 is guided to the damper 11. Here, the signal values Ve1, Ve2, Ve3 are just as described in Embodiment 8. The particle beam therapy system 51 of Embodiment 10 operates similarly to in Embodiment 4. The particle beam therapy system 51 of Embodiment 10 achieves the same effect as in Embodiment 4. Further, the particle beam therapy system 51 of Embodiment 10 is configured to use, in place of the kicker electromagnet 10 in Embodiment 4, the beam deflector 15 that is able to switch the beam path faster and to make the deflection angle larger, than the kicker electromagnet 10, so that the particle beam therapy system can be designed compact while achieving more rapid switching of the beam path than that in Embodiment 4. In Embodiment 11, such a case will be shown where, in the particle beam therapy system 51 of Embodiment 5 in which, when irradiation requests from the plurality of treatment rooms 29 are overlapping, the charged particle beam 81 is controlled to be switched between toward the respective corresponding treatment rooms 1, 2 (treatment rooms 29a, 29b) without using the mask signal msig in a short time, a beam deflector 15 is used, thereby to achieve rapid switching of the beam path and to allow the particle beam therapy system to be designed compact. FIG. 43 is a configuration diagram showing a particle beam therapy system according to Embodiment 11 of the invention, and FIG. 44 is a diagram showing a beam-path controller in FIG. 43. FIG. 45 is a timing chart illustrating a beam distribution to a plurality of treatment rooms according to Embodiment 11 of the invention. The particle beam therapy system 51 of Embodiment 11 differs from that of Embodiment 5 in that the beam deflector 15 is used as the beam-path changer 16 and the treatment management device 95 includes a beam-path controller 115 that outputs a beam-deflector control signal csigc for controlling the beam deflector 15. The beam-path controller 115 includes: an emitter control-signal generator 57 for generating an emitter control signal csiga; a beam-deflector control-signal generator (beam-path changer control-signal generator) 107 for generating a beam-deflector control signal csigc; and a control signal generator 35 for outputting a plurality of control signals to the emitter control-signal generator 57 and the beam-deflector control-signal generator 107. The control signal generator 35 includes: a time-sharing signal generator 45 for generating a time-sharing signal ssiga with a cycle of Tc2 that is shorter than the cycle Tc1; and a respiratory gate-signal generator 34 for generating respiratory gate signals gsig1, gsig2. The beam-deflector control-signal generator 107 includes a pulse controller 41, a high-speed switch 42 and a deflector power source 43. The pulse controller 41 in Embodiment 11 receives the respiratory gate signals gsig1, gsig2 and the time-sharing signal ssiga, and outputs a generated control signal to the high-speed switch 42. The high-speed switch 42 generates the beam-deflector control signal csigc according to the control signal from the pulse controller 41. Operations of the particle beam therapy system 51 of Embodiment 11 will be described using FIG. 45. Description will be made about part of operations which differs from Embodiment 5. When the condition for transporting the charged particle beam 81 to the treatment room 1 (treatment room 29a) is established, the beam-path controller 115 outputs a path-1 command (signal-value Vc1 state) for ordering switching of the path so that the charged particle beam 81 is guided to the treatment room 1 (treatment room 29a). When the condition for transporting the charged particle beam 81 to the treatment room 2 (treatment room 29b) is established, the beam-path controller 115 outputs a path-2 command (signal-value Vc2 state) for ordering switching of the path so that the charged particle beam 81 is guided to the treatment room 2 (treatment room 29b). Here, the signal values Vc1, Vc2 are just as described in Embodiment 7. The particle beam therapy system 51 of Embodiment 11 operates similarly to in Embodiment 5. The particle beam therapy system 51 of Embodiment 11 achieves the same effect as in Embodiment 5. Further, the particle beam therapy system 51 of Embodiment 11 is configured to use, in place of the kicker electromagnet 10 in Embodiment 5, the beam deflector 15 that is able to switch the beam path faster and to make the deflection angle larger, than the kicker electromagnet 10, so that the particle beam therapy system can be designed compact while achieving more rapid switching of the beam path than that in Embodiment 5. In Embodiment 12, such a case will be shown where, in the particle beam therapy system 51 in Embodiment 6 which is provided with the damper 11 in the beam transport system 59 and in which, when irradiation requests from the plurality of treatment rooms 29 are overlapping, the charged particle beam 81 is controlled to be switched between toward the respective corresponding treatment rooms 1, 2 (treatment rooms 29a, 29b) in a short time without using the mask signal msig, a beam deflector 15 is used, thereby to achieve rapid switching of the beam path and to allow the particle beam therapy system to be designed compact. FIG. 46 is a configuration diagram showing a particle beam therapy system according to Embodiment 12 of the invention, and FIG. 47 is a diagram showing a beam-path controller in FIG. 46. FIG. 48 is a timing chart illustrating a beam distribution to a plurality of treatment rooms according to Embodiment 12 of the invention. The particle beam therapy system 51 of Embodiment 12 differs from that of Embodiment 6 in that the beam deflector 15 is used as the beam-path changer 16 and the treatment management device 95 includes a beam-path controller 116 that outputs a beam-deflector control signal csige for controlling the beam deflector 15. The beam-path controller 116 includes: an emitter control-signal generator 57 for generating an emitter control signal csiga; a beam-deflector control-signal generator (beam-path changer control-signal generator) 108 for generating the beam-deflector control signal csige; and a control signal generator 35 for outputting a plurality of control signals to the emitter control-signal generator 57 and the beam-deflector control-signal generator 108. The control signal generator 35 includes: a time-sharing signal generator 45 for generating a time-sharing signal ssiga with a cycle of Tc2 that is shorter than the cycle Tc1; and a respiratory gate-signal generator 34 for generating respiratory gate signals gsig1, gsig2. The beam-deflector control-signal generator 108 includes a pulse controller 41, a high-speed switch 42 and a deflector power source 43. The pulse controller 41 in Embodiment 12 receives the respiratory gate signals gsig1, gsig2 and the time-sharing signal ssiga, and outputs a generated control signal to the high-speed switch 42. The high-speed switch 42 generates the beam-deflector control signal csige according to the control signal from the pulse controller 41. Operations of the particle beam therapy system 51 of Embodiment 12 will be described using FIG. 48. Description will be made about part of operations which differs from Embodiment 6. When the condition for transporting the charged particle beam 81 to the treatment room 1 (treatment room 29a) is established, the beam-path controller 116 outputs a path-1 command (signal-value Ve1 state) for ordering switching of the path so that the charged particle beam 81 is guided to the treatment room 1 (treatment room 29a). When the condition for transporting the charged particle beam 81 to the treatment room 2 (treatment room 29b) is established, the beam-path controller 116 outputs a path-2 command (signal-value Ve3 state) for ordering switching of the path so that the charged particle beam 81 is guided to the treatment room 2 (treatment room 29b). When the condition for guiding the charged particle beam 81 to the damper 11 is established, the beam-path controller 116 outputs a path-3 command (signal-value Ve2 state) for ordering switching of the path so that the charged particle beam 81 is guided to the damper 11. Here, the signal values Ve1, Ve2, Ve3 are just as described in Embodiment 8. The particle beam therapy system 51 of Embodiment 12 operates similarly to in Embodiment 6. The particle beam therapy system 51 of Embodiment 12 achieves the same effect as in Embodiment 6. Further, the particle beam therapy system 51 of Embodiment 12 is configured to use, in place of the kicker electromagnet 10 in Embodiment 6, the beam deflector 15 that is able to switch the beam path faster and to make the deflection angle larger, than the kicker electromagnet 10, so that the particle beam therapy system can be designed compact while achieving more rapid switching of the beam path than that in Embodiment 6. It should be noted that, in Embodiments 1 to 12, the description has been made citing the irradiation method in which the charged particle beam 81 is stopped at the time of changing the slice but the charged particle beam 81 is continued to be radiated at the time of irradiation within the same slice; however, the invention is not limited thereto, and may be applied to another method of, such as a spot scanning in which the charged particle beam 81 is stopped on each irradiation-spot basis, a raster scanning, or the like. Further, in the present invention, any combination of the respective embodiments and any appropriate modification or omission in the embodiments may be made without departing from the scope of the invention. 10: kicker electromagnet, 11, 11a, 11b: damper, 15: beam deflector, 16: beam-path changer, 18, 19: beam-path controller, 29, 29a, 29b: treatment room, 30, 30a, 30b: patient, 33: time-sharing signal generator, 36: emitter control-signal generator, 37: kicker control-signal generator (beam-path changer control-signal generator), 39: emitter control-signal generator, 40: kicker control-signal generator (beam-path changer control-signal generator), 41: pulse controller, 42: high-speed switch, 43: deflector power source, 44: mask signal generator, 45: time-sharing signal generator, 46: emitter control-signal generator, 47: kicker control-signal generator (beam-path changer control-signal generator), 48, 49: beam-deflector control-signal generator (beam-path changer control-signal generator), 50: kicker control-signal generator (beam-path changer control-signal generator), 51: particle beam therapy system, 54: circular accelerator (accelerator), 57: emitter control-signal generator, 58, 58a, 58b: particle beam irradiation apparatus, 59: beam transport system, 60: kicker control-signal generator (beam-path changer control-signal generator), 62: emitter, 63, 64, 65, 66, 67, 68: beam-path controller, 69: kicker control-signal generator (beam-path changer control-signal generator), 74: line electrode plate, 75: backside conductor, 76: electrode plate, 77, 77a, 77b, 77c, 77d, 77e, 77f: conductive plate, 81: charged particle beam, 95: treatment management device, 97: voltage pulse, 105, 106, 107, 108: beam-deflector control-signal generator (beam-path changer control-signal generator), 113, 114, 115, 116: beam-path controller, csiga: emitter control signal, csigb: kicker control signal (beam-path changer control signal), csigc: beam-deflector control signal (beam-path changer control signal, csigd: kicker control signal (beam-path changer control signal), csige: beam-deflector control signal (beam-path changer control signal), gsig1, gsig2, gsig3: respiratory gate signal, msig: mask signal, ssig, ssiga: time-sharing signal, TV0: transmission base time, TP0: particle-movement base time.
048620050	summary	BACKGROUND OF THE INVENTION This invention generally relates to devices for detecting radioactive contamination in hand-holdable objects, such as the tools that are used to service a nuclear power facility. Devices for detecting radioactive contamination in small objects are known in the prior art. Such devices are generally known in the art as "friskers," and are often used to check whether or not a tool or other object which has been subjected to a decontamination process has in fact been rendered completely free of such radioactive contaminants. Generally, such devices comprise a radiation detector (which may be either a gas-flow proportional detector or a scintillation-type detector) mounted on a short, table-like structure. The tools or other hand-held objects to be tested are placed over the radiation detector, which scans them for radioactive contaminants. In some such devices, a second radiation detector is disposed over the first detector, so that radiation readings from both the bottom and top surfaces of the tool or other object may be taken simultaneously. Such a dual-detector configuration has the advantage of detecting contaminants which emit radiation from only one side of the tool, as can happen when a radioactive particle is lodged within a crevice of the tool. The successful operation of such radiation detection devices is important, since the failure of such a device to detect the presence of radioactive contaminants could result in the lodgment of radioactive particles in the skin of one of the facility operators. While there are frisker-type radiation detectors in the prior art which are generally capable of satisfactorially determining whether or not a particular tool or other object emits an unacceptably high amount of radioactivity, the applicants have observed a number of shortcomings in these prior art devices. One such shortcoming is the manner in which these devices solve the problem of preventing the radiation alarm circuits from being spuriously actuated by background radiation. This is a serious problem as such frisker-type detectors are often operated in or adjacent to the decontamination rooms of nuclear facilities, where tools and other objects awaiting decontamination radiate a significant amount of gamma radiation throughout the room. To prevent such spurious triggering of radiation alarm circuitry, some of these devices exclusively rely upon a microprocessor which has been programmed to periodically sample the background gamma radiation, and to subtract the sampled background radiation value from the readings obtained from the frisker-type radiation detector as the objects are being examined thereby. While exclusive reliance upon "background subtraction" obviates the need for providing a thick and heavy lead shield around the radiation detector to block out the background radiation, it can also cause the device to give inaccurate or false readings since background gamma radiation in a nuclear facility is very much subject to considerable, moment-to-moment fluctuations caused by the movement of contaminated equipment in or around the detector of the device. To overcome the shortcomings associated with the exclusive reliance upon background subtraction, a few prior art designs provide partial shielding around the radiation detector. However, the shielding in the hoods of every such detector that the applicants are aware of affords such incomplete protection so as to only marginally reduce the dependency upon "background subtraction." Other shortcomings associated with many of the prior art frisker-type radiation detector devices are the result of the type of radiation detectors used in such devices. Single-zone gas-flow proportional detectors are incapable of informing the operator whether the radiation emitted by the tool or other object is the result of a single, localized "hot particle," or is the result of a contaminant that is uniformly spread over the surface of the tool. Still another problem associated with single-zone gas-flow proportional detectors is the relatively low signal to noise ratio that such detectors yield when placed in a substantial field of background radiation. Some prior art designs have attempted to remedy the deficiencies associated with single-zone detection by providing a bank of separate, scintillation-type detectors. However, such detector banks are apt to have "dead zones" in certain areas between adjacent detectors which are blind to radiation, thereby affording an opportunity for a "hot particle" to escape detection. Additionally, the fragility of the thin plastic "windows" used in such detectors makes them very easy to break when a hard, heavy and sharp object is placed on them. Attempts have been made to solve the fragility problem by using thicker windows of plastic. However, the use of such thick plastic panes desensitizes the detectors to beta radiation, thereby forcing the detector to rely exclusively upon its sensitivity to gamma radiation in making its measurements. Such exclusive reliance upon gamma radiation disadvantageously decreases the signal to noise ratio of the detector and greatly increases the time necessary for the detectors to determine the amount of radiation emitted by the tool being scanned. Finally, many of the frisker-type detectors of the prior art must be manually actuated prior to and during operation by the manipulation of buttons on a control panel. Applicants have observed that the button configurations in such control panels often provides a situs where radioactive debris and airborne particles can contaminate the device. Clearly, what is needed is a frisker-type radiation detector apparatus which is capable of accurately, reliably and consistently detecting the presence of radioactive material on tools and other objects. Ideally, such a radiation detector should have a plurality of mutually-contiguous or overlapping radiation-sensitive zones so that the existence and location of one or more "hot particles" in a particular tool or other object may be reliably determined. Additionally, the device should have some sort of means for cancelling out the effects of background radiation on the detector which minimizes reliance upon computerized "background subtraction." Finally, it would be desirable if such a device could be easily operated without the need for manipulating manual controls which, as pointed out previously, can afford a situs of potential radiation contamination. SUMMARY OF THE INVENTION Generally speaking, the invention is an apparatus which overcomes the shortcomings associated with prior art frisker-type radiation detector devices. The apparatus comprises a radiation detector assembly including a detector having a top side that is sensitive to both beta and gamma radiation throughout substantially all of its area, and a platform screen disposed over the topside of the detector for both supporting the hand-holdable object being examined and for uniformly spacing the object from the detector. A shielding cabinet is further provided for shielding the detector from a large part of the ambient background radiation, thereby reducing the dependency of the detector assembly on background subtraction. The shielding cabinet is provided with an access opening for allowing an operator to deposit and withdraw an object onto and off of the platform screen. The detector is preferably a gas-flow proportional detector having a plurality of mutually adjacent radiation detecting zones, each of which is independently sensitive to radioactivity. The division of the topside of the detector from a single to a plurality of radiation sensitive zones advantageously desensitizes the detector to the effects of background radiation, and further assists the operator in ascertaining whether the contamination is localized or uniformly spaced, and if localized, the particular portion of the object that is contaminated with radioactive particles. In the preferred embodiment, the gas-flow proportional detector is formed from a single conductive housing that forms the cathode, and a plurality of parallel, fork-shaped electrodes disposed within the housing, each of which forms an individually powered and individually monitored anode. To minimize downtime in the event of a malfunction in the detector, the apparatus may include a spare gas-flow proportional detector that is fluidly connected to the same source of pressurized counting gas as the main detector so as to provide a fully-purged and readily operable backup detector at all times. The platform screen is preferably formed from a sheet of perforated and structurally strong material, such as a sheet of perforated stainless steel. The area of the openings in the sheet may take up at least 60 percent of the area of the sheet to render the platform substantially conductive to beta radiation. Additionally, a removable protective screen may be disposed between the platform means and the radiation detector. The protective screen may include a film of thin, strong and flexible plastic material, such as Mylar.RTM. having a thickness of between about 0.2 and 0.8 mg/cm.sup.2. The protective screen may further include a support grid that defines a number of small individual "window panes" in the sheet plastic and uniformly supports it across the top side of the detector. The sheet of perforated stainless steel and the support grid coact to form a single, strong platform capable of both supporting heavy hand tools and preventing any sharp edges or corners of these tools from puncturing the thin plastic sheet material disposed over the top side of the detector. The shielding cabinet preferably includes a sheet of shielding material, which may be a lead plate, for shielding the detector from background radiation and for "back scattering" a portion of the gamma radiation that the top side of the detector is exposed to in order to increase the gamma radiation sensitivity of the detector. The walls of the shielding cabinet are preferably hollow so as to define pockets capable of removably receiving one or more sheets of lead shielding material. The pocket-like interior of these walls advantageously allows the amount of shielding afforded by a particular wall to be increased when the background radiation is particularly high or completely removed if the background radiation is very low. The shielding cabinet also includes cabinet doors on opposing sides, which, when opened, form a shelf surface that is substantially parallel with the top side of the detector so that objects longer than the width of the cabinet may be easily drawn over the detector and scanned for radioactive material. The apparatus may further include a shallow support table that is manually positionable within the interior of the shielding cabinet for supporting and spacing a second detector over the first detector. Spaces are provided between the legs of the shallow table so that elongated objects, such as scaffolding members, may be passed through openings provided by the opposing side cabinet doors between the two detectors. Finally, the apparatus may include a mat-like foot switch for automatically actuating the detector within the radiation detector assembly when the operator steps up to the access opening in the shielding cabinet. The provision of such a mat-style foot switch obviates the need for the operator to depress buttons or to manipulate other controls to actuate and operate the device, thereby eliminating a situs of possible radioactive contamination.
	description	The United States Government has rights in the following invention pursuant to Contract No. DE-AC07-99ID13727 between the U.S. Department of Energy and Bechtel BWXT Idaho, LLC. The present invention relates to separating cesium and strontium from an acidic solution. More specifically, the present invention relates to simultaneously separating cesium and strontium from the acidic solution using a mixed extractant solvent. Cesium-137, strontium-90, and actinides account for a significant amount of the radioactivity of liquid wastes, such as high level liquid wastes from nuclear fuel reprocessing. Cesium-137 and strontium-90 account for over 99.9% of the relative toxicity of the liquid waste once the actinides have been removed. Cesium-137 has a halflife (“t1/2”) of 30 years and strontium-90 has a t1/2 of 29 years. This liquid waste is extremely hazardous and expensive to dispose of. To increase safe handling of the majority of the liquid waste and to significantly reduce its storage and disposal cost, the liquid waste is separated into two portions: one containing the majority of the radioactive components and one containing the bulk of the non-radioactive components. Removing the radioactive components allows the liquid waste to be decategorized and disposed of in geological formations after vitrification. Currently, separate technologies are used to remove the actinides and fission products from the liquid waste and, often times, separate processes are used to remove specific radionuclides, such as cesium and strontium. The ability to remove and recover cesium and strontium from spent nuclear fuel waste represents a significant issue regarding short term heat loading in a geological repository. Cesium and strontium are major heat generators in the liquid waste and produce gamma and beta radiation. Removing the cesium-137 and strontium-90 would enable these radionuclides to be stored in a short-term waste facility, enabling long-term storage facilities to store waste closer together by eliminating some of the heat load. Liquid extraction, sorption, and coprecipitation methods have been used to remove cesium or strontium from nuclear acidic waste solutions or related alkaline wastes. Numerous extractants have been identified that extract cesium or strontium from alkaline solutions or acidic solutions. The extractants are typically separate solvents that are designed to remove one of these radionuclides. For instance, crown ether compounds or calixarene crown ether compounds have been used to extract cesium. U.S. Pat. No. 6,174,503 to Moyer et al., U.S. Pat. No. 6,566,561 to Bonnesen et al., Duchemin et al., Solvent Extr. And Ion Exch., 19(6):1037-1058 (2001), Leonard et al., Solvent Extr. And Ion Exch., 21(4):505-526 (2003), Leonard et al., Sep. Sci. and Technol., 36(5-6):743-766 (2001), White et al., Sep. Sci. and Technol., 38(12-13):2667-2683 (2003), and Norato et al., Sep. Sci. and Technol., 38(12-13):2647-2666 (2003) disclose extracting cesium from alkaline solutions using calix[4]arene-crown ether compounds. The calix[4]arene-crown ether compounds and modifiers are dissolved in a diluent. The calixarene is calix[4]arene-bis-(tert-octylbenzo)-crown-6 (“BOBCalixC6”). Strontium is removed from the alkaline solutions in a separate process using monosodium titanate. One specific extractant includes 0.007M BOBCalixC6, 0.750M 1-(2,2,3,3-tetrafluoro-propoxy)-3-(4-sec-butylphenoy)-2-propanol (“Cs-7SB”), 0.003 M trioctylamine (“TOA”), and Isopar® L and is referred to herein as the caustic-side solvent extraction (“CSSX”) solvent. The CSSX solvent provides a forward distribution ratio or coefficient for cesium (“DCs”) of 8.0 from a 1M nitric acid solution. Another specific extractant includes 0.01M BOBCalixC6, 0.5M Cs-7SB, 0.001 M TOA, and Isopar® L. U.S. Pat. No. 5,926,687 to Dozol et al. and Bonnesen et al., “Development of Process Chemistry for the Removal of Cesium from Acidic Nuclear Waste by Calix[4]arene-crown-6 ethers,” ACS Sym. Ser. 757 (Calixarenes for Separations), 26-44 (2000) disclose extracting cesium from acidic solutions using calix[4]arene-crown ether compounds. While the tested calix[4]arene-crown ether compounds have high distribution coefficients for cesium, they have low distribution coefficients for strontium. Various calix[4]arene-crown ether compounds and modifiers were tested because the stability of the calix[4]arene-crown ether compounds and modifiers differed in each of these solutions. In Dozol et al., Sep. Sci. and Technol., 34(6&7):877-909 (1999), monocrown or biscrown calix[4]arenes in a 1,3 alternative cone conformation are disclosed to remove cesium from acidic or alkaline solutions. U.S. Pat. No. 5,888,398 to Dietz et al. discloses using an 18-crown-6-ether to extract cesium from acidic solutions. The 18-crown-6-ether selectively extracts cesium over other ions, such as hydrogen, aluminum, calcium, boron, and strontium. U.S. Pat. Nos. 5,344,623 and 5,346,618 to Horwitz et al., U.S. Pat. No. 6,511,603 to Dietz et al., Lamb et al., “Novel Solvent System for Metal Ion Separation: Improved Solvent Extraction of Strontium(II) and Lead (II) as Dicyclohexano-18-crown-6 Complexes,” Sep. Sci. and Technol., 34(13):2583-2599 (1999), Chiarizia et al., “Composition of the Organic Phase Species in the Synergistic Extraction of Sr2+ by Mixtures of Di(2-Ethylhexyl)Alkylenediphosphonic Acids and Dicyclohexano-18-crown-6,” Solvent Extr. And Ion Exch., 21(2):171-197 (2003), and Tanigawa et al., Chem. Eng. J. 39:157-168 (1988) disclose extracting strontium from an acidic solution using crown ethers. One specific extractant includes a mixture of 0.15M 4′,4′,(5′)-di-(t-butyldicyclo-hexano)-18-crown-6 (“DtBu18C6”) and 1.2M tri-n-butyl phosphate (“TBP”) in Isopar®L and is referred to herein as the strontium extraction (“SREX”) solvent, as described in Horowitz et al., Solvent Extr. And Ion Exch., 9(1):1-25 (1991). The SREX solvent provides a distribution ratio or coefficient for strontium (“DSr”) of 0.7 from a 1M nitric acid solution. However, using separate extractants to remove the cesium and strontium is disadvantageous in regard to environmental concerns, safety, simplicity and effectiveness of processing, and undesirable generation of secondary waste. Methods of extracting both cesium and strontium have also been disclosed. In U.S. Pat. No. 4,749,518 to Davis et al., cesium is extracted from acidified nuclear waste with bis 4,4′(5) [1-hydroxy-2-ethylhexyl]benzo 18-crown-6 and a cation exchanger. The strontium is then extracted using bis 4,4′(5′) [1-hydroxyheptyl]cyclohexo 18-crown-6 and a cation exchanger. In U.S. Pat. No. 5,393,892 to Krakowiak et al., a method of removing alkali metal and alkaline earth metals is disclosed. A solid inorganic support having a ligand covalently bonded thereto is contacted with a solution including the alkali metal and alkaline earth metals. The ligand is an oxygen donor macrocyclic polyether cryptand that selectively removes the alkali metal and alkaline earth metals. In U.S. Pat. No. 5,666,641 to Abney et al., a polymeric material including a polymer and a plasticizer is used to extract cesium and strontium. In U.S. Pat. No. 5,666,642 to Hawthorne et al., metal dicarbollide ion complexes are used to remove cesium and strontium from an aqueous fission product waste solution. The metal dicarbollide ion complexes are used to sequentially remove the cesium and then the strontium. In Horwitz et al., International Solvent Extraction Committee '96, “A Combined Cesium-Strontium Extraction/Recovery Process,” p. 1285-1290 (1996), an extraction process using di-t-butylcyclohexano-18-crown-6 and a macrocyclic polyether are disclosed to simultaneously extract cesium and strontium. In addition, a large scale demonstration of concurrent cesium and strontium partitioning from defense-related nuclear waste was performed in Russia using a cobalt dicarbollide extraction process. In U.S. Pat. No. 6,270,737 to Zaitsev et al., a composition of a complex organoboron compound and polyethylene glycol in an organofluorane diluent is used to extract cesium and strontium. The complex organoboron compound is a halogenated cobalt dicarbollide. In U.S. Pat. No. 6,258,333 to Romanovskiy et al., a composition of a complex organoboron compound, polyethylene glycol, and a neutral organophosphorus compound in a diluent is used to simultaneously extract cesium and strontium. The complex organoboron compound is a halogenated cobalt dicarbollide. However, this extraction process uses multiple chemicals and, therefore, adds significant volume to the waste volume produced by the extraction process. It is desirable to develop an extraction process that simultaneously removes or extracts cesium and strontium from an acidic solution. Such a development would improve capacity of long-term storage facilities and reduce the need to create new storage facilities. In order to be useful in large-scale processing applications, the solvent used in such an extraction process would desirably be highly selective, cost effective, produce reduced waste volume, and be relatively nonhazardous. The present invention comprises a mixed extractant solvent that includes calix[4]arene-bis-(tert-octylbenzo)-crown-6 (“BOBCalixC6”), 4′,4′,(5′)-di-(t-butyldicyclo-hexano)-18-crown-6 (“DtBu18C6”), and at least one modifier dissolved in a diluent. The BOBCalixC6 may be present in the mixed extractant solvent from approximately 0.0025M to approximately 0.025M. The DtBu18C6 may be present in the mixed extractant solvent from approximately 0.01M to approximately 0.5M, such as from approximately 0.086 M to approximately 0.108 M. At least one modifier may be 1-(2,2,3,3-tetrafluoropropoxy)-3-(4-sec-butylphenoxy)-2-propanol (“Cs-7SB”), which may be present in the mixed extractant solvent from approximately 0.2M to approximately 1.0M. The diluent may be an isoparaffinic hydrocarbon. The mixed extractant solvent may further include trioctylamine, tri-n-butyl phosphate, or mixtures thereof. In one embodiment, the mixed extractant solvent may include approximately 0.15M DtBu18C6, approximately 0.007M BOBCalixC6, and approximately 0.75M Cs-7SB modifier dissolved in an isoparaffinic hydrocarbon. The present invention also comprises an extraction system that includes an organic phase and an aqueous phase. The organic phase includes the mixed extractant solvent as referenced above. The aqueous phase includes an acidic solution, such as a dissolved spent nuclear fuel. The acidic solution may have from approximately 0.01M to approximately 3M nitric acid. The acidic solution may also include cesium and strontium. The present invention also comprises a method of separating cesium and strontium from an acidic solution. The method includes providing an acidic solution that has cesium and strontium. The acidic solution is contacted with a mixed extractant solvent as referenced above. The acidic solution may include from approximately 0.01M to approximately 3M nitric acid. After contacting the acidic solution with the mixed extractant solvent, a first organic phase and a first aqueous phase may be formed. The cesium and strontium may be extracted into the first organic phase. The first organic phase and the first aqueous phase may be separated, removing the cesium and strontium from the acidic solution. The extraction of the cesium and strontium may be conducted at a temperature ranging from approximately 1° C. to approximately 40° C., such as from approximately 10° C. to approximately 15° C. The cesium, strontium, and mixed extractant solvent may be recovered by contacting the first organic phase with a second aqueous phase. The cesium and strontium may be extracted into the second aqueous phase, which is separated from the first organic phase. The cesium and strontium may be recovered at a temperature ranging from approximately 10° C. to approximately 60° C., such as from approximately 20° C. to approximately 40° C. The present invention also comprises a method of extracting strontium from an acidic solution. The acidic solution includes strontium and is contacted with a solvent that includes DtBu18C6, Cs-7SB, and an isoparaffinic hydrocarbon. A mixed extractant solvent for extracting cesium and strontium from an acidic solution is disclosed. The mixed extractant solvent simultaneously or concurrently extracts cesium and strontium from the acidic solution. The cesium and strontium are collectively referred to herein as “radionuclides.” The mixed extractant solvent includes a crown ether compound, a calixarene compound, and at least one modifier dissolved in a diluent. The crown ether compound and the calixarene compound are collectively referred to herein as “extractants.” The mixed extractant solvent may form a first organic phase of a first extraction system that also includes a first aqueous phase. The extractants may be sufficiently soluble in the first organic phase so that a high concentration of the extractants is achieved. The concentration of the extractants in the first organic phase may be sufficiently high to effectively remove the radionuclides from the acidic solution. The extractants may also be relatively insoluble in the first aqueous phase. The crown ether used in the mixed extractant solvent may be 4′,4′,(5′)-di-(t-butyldicyclo-hexano)-18-crown-6 (“DtBul18C6”). DtBu18C6 is available from Eichrom Industries Inc. (Darien, Ill.) and has a molecular weight of 484.72 g/mol. The crown ether may be present in the mixed extractant solvent from approximately 0.001M to approximately 0.5M. In one embodiment, the crown ether is present from approximately 0.086 M to approximately 0.108 M. DtBu18C6 has the following structure: The calixarene used in the mixed extractant solvent may be calix[4]arene-bis-(tert-octylbenzo)-crown-6 (“BOBCalixC6”). BOBCalixC6 is available from IBC Advanced Technologies, Inc. (American Fork, Utah) and has a molecular weight of 1149.52 g/mol. The calixarene may be present in the mixed extractant solvent from approximately 0.0025M to approximately 0.025M. BOBCalixC6 has the following structure: The modifier may be an alcohol modifier, trioctylamine (“TOA”), tri-n-butyl phosphate (“TBP”), or mixtures thereof. The modifier may increase the extractants' ability to extract the radionuclides and may enable a lower concentration of the extractants to be used in the mixed extractant solvent. Since many crown ether and calixarene compounds have limited solubility in diluents, the modifier may keep the extractants dissolved in the diluent. The modifier may also prevent the formation of a third phase during the extraction. In addition, the modifier may improve stripping efficiency of the radionuclides, enabling the cesium and strontium to be effectively removed or stripped from the mixed extractant solvent. The alcohol modifier may have a general structure of where R and R′ are as described in Leonard et al., Sep. Sci. and Technol., 36(5-6):743-766 (2001), Leonard et al., Solvent Extr. And Ion Exch., 21(4):505-526 (2003), and Duchemin et al., Solvent Extr. And Ion Exch., 19(6):1037-1058 (2001). For instance, the alcohol modifier may be 1-(2,2,3,3-tetrafluoropropoxy)-3-(4-sec-butylphenoxy)-2-propanol (“Cs-7SB”), which has the following structure: The Cs-7SB may be present in the mixed extractant solvent from approximately 0.2M to approximately 1.0M. The diluent may be an inert diluent, such as a straight chain hydrocarbon diluent. For instance, the diluent may be an isoparaffinic hydrocarbon diluent, such as Isopar® L or Isopar® M. Isopar® L includes a mixture of C10-C12 isoparaffinic hydrocarbons and is available from Exxon Chemical Co. (Houston, Tex.). Isopar® M includes a mixture of C12-C15 isoparaffinic hydrocarbons and is available from Exxon Chemical Co. (Houston, Tex). The mixed extractant solvent may include other combinations of cesium extractants and strontium extractants besides DtBu18C6 and BOBCalixC6. For instance, combinations of other crown ethers and calixarenes that are capable of concurrently extracting cesium and strontium may be used. In general, crown ethers having a dicyclohexano structure may provide selectivity for strontium and those having a dibenzo structure may provide selectivity for cesium. Additional crown ethers are known in the art and include, but are not limited to, cis-dicyclohexano-18-crown-6 (“DCH18C6”), dimethyl derivatives thereof, and di-t-butyl derivatives thereof. Additional calixarenes are known in the art and may be used in the mixed extractant solvent, such as derivatives of calix[4]arene-crown-6 ether including, but not limited to, mono- and bis-crown-6-derivatives of 1,3 calix[4]arenes. The calixarenes may be in cone, partial cone, 1,2 alternate, or 1,3 alternate conformations. The mixed extractant solvent may also include other alcohol modifiers, such as derivatives of 2-(4-tert-octylphenoxy)-1-ethanol or derivatives of 1-(4-tert-octylphenoxy)-3-(1,1,2,2-tetrafluoroethoxy)-2-propanol. The alcohol modifiers may have fluorine containing substituents on the alcohol carbon. In addition, other diluents, such as 1-octanol, may be used. In one embodiment, the mixed extractant solvent includes 0.15M DtBu18C6, 0.007M BOBCalixC6, and 0.75M Cs-7SB modifier in Isopar® L. The mixed extractant solvent may extract cesium and strontium from a 1M nitric acid solution with a DSr of approximately 10 and a DCs of approximately 8 at ambient temperature. In contrast, the SREX solvent used alone had a substantially lower DSr of 0.7 while the CSSX solvent used alone had a similar DCs of 8.0. The mixed extractant solvent may provide improved cesium and strontium extraction compared to a 1:1 volume ratio of the SREX and CSSX solvents. When the SREX and CSSX solvents were mixed in a 1:1 volume ratio, the DSr decreased to 1.5 and the DCs dropped significantly to 0.64. These results indicate that the mixed extractant solvent may provide substantially improved extraction of the cesium and strontium compared to using the SREX and CSSX solvents alone or in a 1:1 volume ratio. The distribution of cesium and strontium between the organic phase and the aqueous phase may be determined by conventional techniques. The distribution ratio for strontium (“DSr”) was calculated as the ratio of organic phase activity to the aqueous phase activity at equilibrium. High values for the DSr indicate that the strontium is present in the organic phase while low values for the DSr indicate that the strontium is present the aqueous phase. Similarly, the distribution ratio for cesium (“DCs”) was calculated as the ratio of organic phase activity to the aqueous phase activity at equilibrium. High values for the DCs indicate that the cesium is present in the organic phase while low values for the DCs indicate that the cesium is present the aqueous phase. The mixed extractant solvent may be prepared by combining the crown ether, the calixarene, and the modifier with the diluent to form a mixture. Initially, a portion of a final volume of the diluent may be added to the extractants and the modifier to lower the viscosity of the mixture. The mixture may be stirred overnight and the remainder of the diluent may then be added. The mixed extractant solvent may be used to simultaneously extract cesium and strontium from the acidic solution, such as from an acidic nuclear waste solution. The acidic solution may include from approximately 0.001M to approximately 3M nitric acid (“HNO3”). Since these nitric acid levels are similar to the levels typically present in dissolved spent nuclear fuel, the mixed extractant solvent may be used to effectively remove cesium and strontium from dissolved spent nuclear fuel solutions. For instance, the mixed extractant solvent may remove cesium and strontium from an acidic solution having from approximately 0.5M to approximately 3M nitric acid. In one embodiment, the mixed extractant solvent simultaneously extracts cesium and strontium from a 1M nitric acid solution with a DSr of approximately 10 and a DCs of approximately 8 at ambient temperature. The mixed extractant solvent may remove substantially all of the cesium and strontium from the acidic solution after four sequential extractions. By removing the radionuclides, the mixed extractant solvent may be used to lower the radioactive waste volume and heat load of the acidic solution. In addition, the radionuclides and the mixed extractant solvent may be recovered and the mixed extractant solvent may be recycled. The extraction method of the present invention may also produce less secondary waste than in conventional techniques. Furthermore, since the cesium and strontium may be removed simultaneously, the extraction system of the present invention may be advantageous over conventional techniques, which require multiple, separate steps to remove the cesium and strontium. As discussed in detail below, the mixed extractant solvent may provide improved levels of extraction of cesium and strontium compared to the level of extraction achieved when the SREX and CSSX solvents are combined. In other words, the mixed extractant solvent provides synergistic results for the removal of the strontium while coextracting the cesium. The mixed extractant solvent may be used to selectively extract cesium and strontium over additional components in the acidic solution. In addition to cesium and strontium, the acidic solution may include other ions or radioactive elements. Typical components of dissolved spent nuclear fuel solutions are shown in Table 1. Simulants having various combinations of the components shown in Table 1 may be prepared to test the mixed extractant solvent. TABLE 1Typical major components of dissolved, highburn-up spent nuclear fuel solutions.ComponentAmountComponentAmountAcid (M)0.8Pr g/l0.63Tc g/l0.41Nd g/l2.34Ba g/l1.59Zr g/l0.42Ce g/l1.37Sm g/l0.47Cs g/l1.43Np g/l0.43La g/l0.70Pu g/l4.76Pd g/l1.03Am g/l0.62Mo g/l2.09Sn g/l1.39Sr g/l0.44Rb g/l0.20Pd g/l1.03Rb g/l0.20 The cesium and strontium may be removed or forward extracted from the acidic solution by mixing the acidic solution with the mixed extractant solvent. As used herein the terms “forward extract,” “forward extracted,” or “forward extraction” refer to removing or extracting the cesium and strontium from the first aqueous phase of the first extraction system. As such, the first extraction system may include the acidic solution (the first aqueous phase) and the mixed extractant solvent (the first organic phase). The first organic phase and the first aqueous phase may be agitated with one another to extract the cesium and strontium into the first organic phase. The distribution of the cesium and strontium between the first organic phase and the first aqueous phase may heavily favor the first organic phase. The acidic solution may be mixed with the mixed extractant solvent for an amount of time sufficient to form complexes between the cesium and strontium and the extractants. For instance, complexes may be formed between the cesium and the calixarene and between the strontium and the crown ether. After mixing the mixed extractant solvent and the acidic solution for an amount of time sufficient for the complexes to form, two phases may be formed in the first extraction system: the first organic phase and the first aqueous phase. The cesium and strontium may be present in the first organic phase while the first aqueous phase may be substantially depleted of cesium and strontium. The first aqueous phase may include any other ions or radioactive elements that were present in the acidic solution. The first organic phase and the first aqueous phase may then be separated, effectively removing the cesium and strontium from the acidic solution. Once separated, the first organic phase and the first aqueous phase may be further processed. For instance, the first aqueous phase may be extracted multiple times with the mixed extractant solvent to remove substantially all of the cesium and strontium. The first aqueous phase may also be further extracted to remove the additional ions or radioactive elements that may have been present in the acidic solution, such as by using conventional techniques. The radionuclides may be stripped or back extracted from the first organic phase to recover the cesium, strontium, and the mixed extractant solvent. As used herein, the terms “back extract,” “back extracted,” or “back extraction” refer to removing or extracting the cesium and strontium from the mixed extractant solvent. During recovery and recycling conditions, the distribution of the cesium and strontium between the first organic phase and a second aqueous phase may heavily favor the second aqueous phase. The cesium and strontium may be removed from the first organic phase by contacting the first organic phase with the second aqueous phase. The second aqueous phase and the first organic phase may form a second extraction system. The second aqueous phase may be a dilute acidic solution, such as a nitric acid solution having from approximately 0.001M HNO3 to approximately 0.5M HNO3. In addition, water or other dilute mineral acids may be used as the second aqueous phase. The first organic phase may be mixed with the second aqueous phase for an amount of time sufficient for the cesium and strontium ions to dissociate from the complexes of the cesium and strontium with the extractants. Once dissociated, the cesium and strontium may be extracted into the second aqueous phase. The second aqueous phase, having substantially all of the cesium and strontium, may be separated from the first organic phase, which is substantially depleted of cesium and strontium. The radionuclides in the second aqueous phase may then be used or stored. For instance, the cesium and strontium may be solidified for storage. Alternatively, the recovered cesium and strontium may be used as gamma sources, beta sources, or heat sources. The recovered mixed extractant solvent may be reused or recycled into subsequent extractions. The acidic solution may also be processed to remove the additional ions and radioactive elements before the cesium and strontium are removed by the method of the present invention. The additional ions and radioactive elements may be removed by exposure to conventional extraction processes. The extraction and recovery of the cesium and strontium may be performed at a temperature ranging from approximately 1° C. to approximately 40° C. To provide optimal extraction of the cesium and strontium, the forward extraction may be conducted at low temperatures within this range, such as at a temperature ranging from approximately 10° C. to approximately 15° C. However, the forward extraction may also be conducted at ambient temperature, such as from approximately 20° C. to approximately 25° C. The backward extraction of the cesium and strontium may be conducted at a wider range of temperatures, such as from approximately 10° C. to approximately 60° C. For instance, the backward extraction may be performed at a temperature ranging from approximately 20° C. to approximately 40° C. A solvent mixture having the DtBu18C6 extractant, the Cs-7sB modifier, and a diluent may also be used to extract strontium from an acidic solution. The solvent mixture may improve the forward distribution of strontium. For instance, the DSr from a 1M nitric acid solution may be increased from approximately 0.7 using the SREX solvent to a range of approximately 5 to approximately 7 using the solvent mixture having DtBu18C6, Cs-7sB, and the diluent. The following examples serve to explain embodiments of the present invention in more detail. These examples are not to be construed as being exhaustive or exclusive as to the scope of this invention. All solvents used in the extraction process were reagent grade and were used as received. Deionized water was used to prepare all aqueous acid solutions. The nitric acid was reagent grade and was obtained from Sigma-Aldrich Chemical Co. (St. Louis, Mo.). Isopar® L isoparaffinic diluent was obtained from Exxon Chemical Co. (Houston, Tex.). The 85Sr and 137Cs radiotracers used to spike the simulants were obtained as 85SrCl2 in 1M HCl and 137CsCl in 1M HCL from Isotope Products (Burbank, Calif.). Both radiotracers were converted to the nitrate form prior to use. The DtBu18C6 was purchased from Eichrom Industries Inc. (Darien, Ill.). The BOBCalixC6 and the Cs-7SB modifier were obtained from Oak Ridge National Laboratory and were used as received. The SREX solvent was prepared using a mixture of 0.1 5M DtBu18C6, 1.2M TBP, and Isopar® L as described in Horowitz et al., Solvent Extr. And Ion Exch., 9(1):1-25 (1991). The mixture was stirred for approximately 1 hour, until the DtBu18C6 and TBP went into solution. The CSSX solvent included 0.007M BOBCalixC6, 0.750M Cs-7SB modifier, 0.003M TOA, and Isopar® L as described in Bonnesen et al., “Extraction of Cesium from Savannah River Tank Waste Using a Calixarene Crown Ether Extractant,” Report ORNL/TM-13704, Oak Ridge National Laboratory: Oak Ridge, Tenn. (December 1998) and was received already prepared. The 85Sr and 137Cs radiotracers were diluted to 7.3 μCi/ml and heated to incipient dryness. Concentrated HNO3 was then added to convert the radiotracers to the nitrate salts. After three such cycles, 10 ml of varying concentrations of HNO3 (from 0.01M to 10M) were added to the radiotracers to redissolve the salts in preparation for the extraction studies. Carrier free 85Sr in varying concentrations of HNO3 was mixed in equal proportions with the SREX solvent and shaken for 1 minute. The sample was then centrifuged for 1 minute and the resulting organic and aqueous phases sampled for analysis. Aliquots of the organic and aqueous phases were γ-ray counted using a Princeton Gamma-Tech (“PGT”) detector having a bias of +3500V. As shown in FIG. 1, the SREX solvent had a DSr of 0.70 in 1M HNO3 at ambient temperature. The mean of this data (N=3) has an experimental uncertainty of ±5% in the distribution ratio and is consistent with previous work. In all additional testing, carriers were used for both the strontium and cesium except when stated otherwise. The carrier concentrations included 0.001M Sr(NO3)2 and 0.0001M CsNO3. During the initial nitric acid dependency testing, it was discovered that the 8M and 10M HNO3 samples exhibited third phase formation when mixed with the SREX solvent. Therefore, testing was performed to determine the acidity at which a third phase started to occur. Concentrations of 1M, 2M, 3M, 4M, and 5M HNO3 were tested and it was observed that the third phase formed in extraction contacts having greater than or equal to 3M HNO3. A DCs nitric acid dependency test was also performed for the CSSX solvent, the results of which are shown in FIG. 2. The CSSX solvent had a DCs of 8.0 in 1M HNO3 at ambient temperature. The DCs nitric acid dependency is linear and at unity with respect to the distribution ratio when plotted on a log-log basis. The slopes of the nitric acid dependency for both cesium and strontium showed that Sr2+ was charge balanced by 2NO3− and Cs+ was balanced by one NO3−, which concurred with previous work. It was also determined that no coextraction of the cesium into the SREX solvent and no extraction of the strontium into the CSSX solvent occurred when the SREX solvent and the CSSX solvent were evaluated separately. When the SREX and CSSX solvents were mixed in a 1:1 volume ratio, the DSr increased slightly to 1.5 but the DCs dropped significantly to 0.64. In contrast, the SREX solvent when used alone had a DSr of 0.70 and the CSSX solvent when used alone had a DCs of 8.0, as described in Comparative Example 2. Since the DCs dropped significantly, these results indicate that simply combining the SREX and the CSSX solvents in a 1:1 volume ratio did not effectively coextract both cesium and strontium. Neat DtBu18C6, the extractant used in the SREX solvent, was added in varying concentrations to the CSSX solvent. Unexpectedly, an increased forward distribution for strontium was observed. In fact, the DSr increased dramatically to 9.8 while the DCs remained approximately the same (DCs=8.0) as obtained with the CSSX solvent alone. To attain high distribution coefficients for both cesium and strontium, simultaneously, an optimum mixture for the DtBu18C6 and the BOBCalixC6 was found. A plot of the cesium and strontium distribution coefficients as a function of the ratios of DtBu18C6 to 0.007M BOBCalixC6 is shown in FIG. 3. Distribution coefficients for the cesium and strontium diverged at high and low concentrations of the DtBu18C6. However, favorable forward extraction of the cesium and strontium was obtained at DtBu18C6 concentrations ranging from 0.053M to 0.378M. The distribution coefficients were almost equal at DtBu18C6 concentrations ranging from 0.086 M to 0.108 M. At these DtBu18C6 concentrations, the mixed extractant solvent extracted approximately six times more cesium and strontium in a single contact than remained in the nitric acid solution. This level of extraction provides a cesium and strontium removal of 99.9% in four sequential contacts with the mixed extractant solvent. In order to determine which component or components of the mixed extractant solvent were causing the synergy, the two main components used in the CSSX solvent (BOBCalixC6 and Cs-7SB modifier) and the DtBu18C6 from the SREX solvent were procured. Different concentrations of these components in various combinations were mixed and tests were conducted on the different variations. Since it was determined that 1M HNO3 gave favorable combined forward distributions for cesium and strontium, 1M HNO3 was used as the aqueous phase acidity unless otherwise specified. All solvents used were preequilibrated with 1M HNO3. The first combination of tested solvents included 0.15M DtBu18C6 and 0.75M Cs-7SB modifier in Isopar®L. In this solvent extraction system, the DSr was 6.36 and the DCs was 0.046 at 24° C. Since the DCs value was low, these results indicated that no cesium extraction occurred with the DtBu18C6 but that enhanced strontium extraction occurred due to the Cs-7SB modifier. The second combination of solvents included 0.15M DtBu18C6 and 0.007M BOBCalixC6, which were the same concentrations used in the CSSX and SREX solvents, while the Cs-7SB modifier concentration was varied. The results of these extractions are shown below in Table 2. TABLE 2Cesium and Strontium Distribution Ratios as aFunction of Varying Cs-7SB Concentration.Concentration OfCs-7SB (M)DCsDSr0.017.7E−30.010.100.170.230.753.514.040.803.801.92The data in Table 2 indicated that although the DCs increased with increasing Cs-7SB concentration, the DSr peaked at or near a concentration of 0.75M of the Cs-7SB. Thus, for the remainder of the extraction tests, the concentration of the Cs-7SB remained at 0.75M. An extraction of strontium with DtBu18C6, TBP, and TOA in Isopar® L was performed as well as an extraction of DtBu18C6 and TOA in Isopar® L. The DSr was 0.56 and 0.01 at 20° C., respectively. These results, coupled with the results from the mixture of SREX and CSSX described earlier, indicated that the TBP could be removed from the mixed extractant solvent. The results also indicated that the TOA was optional under the experimental extraction conditions. The distribution ratios showed that when the TOA was added to the SREX solvent, it extracted strontium no better than in the SREX solvent alone. A study also determined that using a solvent including only the Cs-7SB modifier in Isopar® L exhibited no extraction of cesium and strontium from 1 M nitric acid solutions. While the TBP of the SREX solvent was originally used in the mixed extractant solvent to enhance the solubility of the strontium in the organic phase, the TBP was found to provide no additional benefit to the coextraction of the cesium and strontium with the mixed extractant solvent. Rather, it was determined that the TBP possibly hindered forward strontium extraction. The TOA, which was added to the CSSX process to aid in cesium stripping by preventing undesired complexation of cesium with organic impurities dissolved during continuous processing, did not interfere with strontium forward distributions in the tests using neat DtBu18C6 added to the CSSX solvent. However, TOA was not used in the mixed extractant solvent so that the testing could be performed under controlled conditions. Therefore, when this extraction method is employed on an industrial scale, it may be necessary to add TOA to the mixed extractant solvent. Tests conducted to determine the component responsible for the elevated strontium distributions indicated that the Cs-7SB modifier provided the increased strontium distribution. The forward distribution of strontium from 1M HNO3 solutions was increased from 0.7 at ambient temperature using SREX (DtBu18C6 and TBP in Isopar®L) to between 5 and 7 using a mixture of DtBu18C6, the Cs-7SB modifier, and the Isopar L ® diluent. As such, the Cs-7SB modifier provided a significant improvement over the SREX extractant for processes where selective strontium removal from acidic solutions is desired. While the positive effect of fluorinated modifiers is known for the extraction of cesium using crown ethers or calixarenes, these modifiers have not been used instead of TBP in the SREX solvent for enhancing strontium extraction. When a second round of testing was performed to reproduce the data presented in FIG. 3, the ambient temperature had dropped from 24° C. to 20° C. At 20° C., the DSr from a 1M HNO3 solution was found to be higher, with a DSr of 11.3 instead of a DSr of 9.8 at 24° C. (as described in Example 1). Since high distribution ratios are desired, the increase in DSr with decreasing temperature was of interest since it has been noted in the literature that the forward distributions of cesium in BOBCalixC6 are similarly temperature dependent. To further elucidate the effect of temperature, temperature dependence tests were performed on the SREX solvent, the CSSX solvent, and the mixed extractant solvent. Tests performed at 10° C. showed that the DSr for the SREX solvent was 2.2 and the DCs for the CSSX solvent was 46.0. In contrast, the distribution ratios at 24° C. were lower, with a DSr of 0.70 and a DCs of 8.0. The temperature dependence tests on the mixed extractant solvent showed that very favorable distributions were achieved at 10° C., as shown in FIG. 4. The DSr and DCs with the mixed extractant solvent were approximately 16 and approximately 20, respectively. The non-linear shape seen in FIG. 4 is due to an enthalpy effect, which indicates that this is an exothermic and, thus, favorable reaction. The lower the temperature, the more excess energy is removed from the system, driving the equilibrium and raising the forward distributions of the cesium and strontium. Nitrate dependency tests were performed on the SREX solvent (0.15M DtBu18C6 and 1.2M TBP in the Isopar L diluent) and on the solvent mixture (0.15M DtBu18C6 and 0.75M Cs-7SB modifier in the Isopar L diluent) using Al(NO3)3 in an effort to compare and determine the effect of nitrate ions on the forward distribution of strontium. The nitrate concentrations were varied by adding Al(NO3)3 to 0.5M HNO3 to yield 0.6M, 0.7M, 0.9M, 1.0M, and 2.5M total NO3. The results from these tests are shown in FIG. 5 and indicate an increase in strontium distribution with increasing nitrate concentrations, giving a slope of approximately 2 for both solvents. These slopes indicate a charge balance of the Sr2+ with 2NO3− ions, which concurs with previous work. In addition, the data in FIG. 5 shows that the solvent mixture (DtBu18C6 and Cs-7SB modifier in Isopar® L) gives a factor of 4 higher distribution than the SREX solvent. Concentrations of 2.5M NO3 yielded a forward distribution for the solvent mixture (DtBu18C6 and Cs-7SB modifier in Isopar L) of DSr=46, while the distribution for the SREX solvent was DSr=12 at ambient temperature. To develop a complete extraction process, the ability to sequentially extract and back extract the cesium and strontium and to recover and reuse the mixed extractant solvent was studied. A combination of solvents that included 0.15M DtBu18C6, 0.007M BOBCalixC6, and 0.75M Cs-7SB modifier in Isopar®L was prepared by adding neat DtBu18C6, BOBCalixC6, and the Cs-7SB modifier to a mixing vessel. Approximately 10% of the required final Isopar®L volume was added to lower the viscosity and the mixture was left to stir overnight. The remainder of the Isopar®L was then added as a diluent the next morning to form the mixed extractant solvent. Sequential extractions of fresh aliquots of the mixed extractant solvent with the same aliquot of radioactive traced carrier solution gave the following forward distribution ratios for cesium and strontium: TABLE 3Forward Distribution Ratios for Cesium and Strontium.Contact #DCsDSr18.19.5211.1 11.6 37.68.44*** The level of cesium and strontium remaining in the acidic solution were below detection limits in extraction contact #4. Efficient stripping of most of the cesium and strontium from the organic phase was demonstrated in two stages by repeatedly contacting equal volumes of the organic phase with 0.01M HNO3. The results of two typical back extractions (strips) at 20° C. are shown in Table 4. TABLE 4Backward Distribution Ratios for Cesium and Strontium.DCsDSrStrip #10.330.02Strip #20.170 Nitric acid dependency tests were performed at ambient temperature (approximately 23° C.) on the mixed extractant solvent described in Example 5. Varying concentrations of HNO3, from 0.01M to 2M, were mixed in equal proportions with the mixed extractant solvent. The nitric acid dependency test was performed in a manner similar to that described in Comparative Example 2. The results of the nitric acid dependency are shown in FIG. 6 and Table 5. TABLE 5Forward Distribution Ratios for Cesium and Strontiumin Varied HNO3 Concentrations.HNO3Concentration (M)DCsDSr0.010.190.010.11.140.230.53.441.981.05.667.372.09.2620.8 The crossover point, the molarity at which both the forward distribution of cesium and strontium is equal to or greater than approximately 1, is approximately 0.3M. The forward distribution of cesium is equal to or greater than approximately 1 at a lower molarity of 0.1 M. In summary, the mixed extractant solvent has been shown to simultaneously remove cesium and strontium from acidic solutions. The distribution ratios (DCs and DSr) achieved using the mixed extractant solvent are significantly higher than the distribution ratios of the SREX solvent or the CSSX solvent used alone or in a 1:1 volume ratio. While the invention may be susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. However, it should be understood that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the following appended claims.
047016230	claims	1. In a charged particle beam apparatus comprising first means for generating a beam of charged particles, second means for directing said beam toward a target, a tube having a longitudinal bore, said bore forming a vacuum envelope, and said beam traveling through said bore, and third means disposed outside said tube for generating a variable magnetic beam deflection field for said beam within said tube, the improvement comprising said tube including a first metal section, a second metal section, and a non-conductive section containing a grounded, helically wound conductive filament disposed between said first and said second sections, said filament being closely wound, wherein eddy currents induced in said helically wound conductive filament by said variable magnetic beam deflection field are impeded between adjacent turns of said helically wound filament, and wherein said helically wound conductive filament is connected respectively at opposite ends to said first section and said second section. 2. A charged particle beam apparatus according to claim 1, wherein said helically wound filament has a thin film resistive coating for impeding said eddy currents. 3. A charged particle beam apparatus according to claim 2, wherein said helically wound finalment is nichrome, and said resistive coating is an oxide of nichrome. 4. A charged particle beam apparatus according to claim 1 or claim 2 or claim 3, wherein said helically wound filament is a removable insert within said non-conductive section. 5. A charged particle beam apparatus according to claim 4, wherein said third means include deflection coils for deflecting said beam within said tube. 6. A charged particle beam apparatus according to claim 5, wherein said deflection coils are disposed about said helically wound conductive filament. 7. A charged particle beam apparatus according to claim 1 or claim 2 or claim 3, wherein said third means include deflection coils for deflecting said beam within said tube. 8. A charged particle beam apparatus according to claim 7, wherein said deflection coils are disposed about said helically wound conductive filament. 9. A charged particle beam apparatus according to claim 1 or claim 2 or claim 3, wherein said helically wound conductive filament includes a single wire in a helix configuration.
	abstract	A detection apparatus for detecting the surface of a specimen by means of a cantilever having a probe and a piezo resistance element, which comprises a first circuit for detecting an electric current flowing through the piezo resistance element and a second circuit for detecting an electric current flowing through the probe. The electric current flowing through the piezo resistance element and the electric current flowing through the probe are detected by way of a common current path.
	summary
	summary
043572090	abstract	A nuclear divisional reactor including a reactor core having side and top walls, a heat exchanger substantially surrounding the core, the heat exchanger including a plurality of separate fluid holding and circulating chambers each in contact with a portion of the core, control rod means associated with the core and external of the heat exchanger including control rods and means for moving said control rods, each of the chambers having separate means for delivering and removing fluid therefrom, separate means associated with each of the delivering and removing means for producing useable energy external of the chambers, each of the means for producing useable energy having separate variable capacity energy outputs thereby making available a plurality of individual sources of useable energy of varying degrees.
042973040	claims	1. Method for solidifying high radioactivity aqueous waste concentrates, medium radioactivity aqueous waste concentrates, actinide containing aqueous waste concentrates, or suspensions of fine-grained solid wastes suspended in water, which concentrates or suspensions contain a metal ion and/or metal oxide, for final noncontaminating storage in which the waste concentrates or the suspensions are subjected together with an absorbing and/or hydraulically binding inorganic material, to a ceramic firing process so as to produce a solid sintered body, comprising the steps of: (a) treating the waste concentrates or suspensions by evaporation, to form an evaporate, to a water content in the range between 40 and 80 percent by weight and a solid content whose metal ion and/or metal oxide concentration lies between 10 and 30 percent by weight of the evaporate being formed, and adjusting the pH of the evaporate to between 5 and 10; (b) kneading the evaporate obtained from step (a) with a clay-like substance containing a small quantity of cement or mixture of a clay-like substance with a small quantity of cement containing an additive for suppressing the volatility of alkali metals or alkaline earth metals which may be present in the evaporate and/or an additive for suppressing the volatility of any decomposable anions which may be present in the evaporate selected from the group consisting of sulfate, phosphate, molybdate and uranate ions, at a weight ratio range of evaporate to clay-like substance of 1:1 to 2:1, said clay-like substance being at least one substance selected from the group consisting of pottery clays, stoneware clays, porcelain clay mixtures and kaolins; (c) producing molded bodies from the kneaded mass obtained from step (b); (d) heat treating the molded bodies, including drying at temperatures between room temperature and 150.degree. C., calcining at temperatures of about 150.degree. to 800.degree. C., and subsequently firing at temperatures between 800.degree. and 1400.degree. C. to form practically undissolvable mineral phases having a chemical composition corresponding approximately to that of natural, stable minerals or rocks; and (e) enclosing the molded bodies containing the fired mineral phases on all sides in a dense, continuous ceramic or metallic matrix. (a) treating the waste concentrates or suspensions by evaporation, to form an evaporate, to a water content in a range between 40 and 80 percent by weight and a solid content whose metal ion and/or metal oxide concentration lies between 10 and 30 percent by weight of the evaporate being formed, and adjusting the pH of the evaporate to between 5 and 10; (b) kneading the evaporate obtained from step (a) with a clay-like substance containing an additive for suppressing the volatility of alkali metals or alkaline earth metals which may be present in the evaporate and/or an additive for suppressing the volatility of any decomposable anions which may be present in the evaporate selected from the group consisting of sulfate, phosphate, molybdate and uranate ions, at a weight ratio range of evaporate to clay-like substance of 1:1 to 2:1, said clay-like substance being at least one substance selected from the group consisting of pottery clays, stoneware clays, porcelain clay mixtures and kaolins; (c) producing molded bodies from the kneaded mass obtained from step (b); (d) heat treating the molded bodies, including drying at temperatures between room temperatures and 150.degree. C., calcining at temperatures of about 150.degree. to 180.degree. C., and subsequently firing at temperatures between 800.degree. and 1400.degree. C. to form practically undissolvable mineral phases having a chemical composition corresponding approximately to that of natural, stable minerals or rocks; and (e) enclosing the molded bodies containing the fired mineral phases on all sides in a dense, continuous ceramic or metallic matrix. 2. The method as defined in claim 1, in which the molded bodies of step (d) are comminuted to a grain size range of about 1 to 10 mm before being enclosed in the matrix of step (e). 3. The method as defined in claim 1 wherein the kneading of step (b) is effected with a mixture of 10 parts by weight of a clay-like substance and 1 to 2 parts by weight of a cement containing 20 to 30 weight percent SiO.sub.2 and 40 to 70 weight percent CaO, and said molded bodies of step (c) are allowed to harden, and are subsequently surface decontaminated with water before step (d). 4. The method as defined in claim 1 wherein said clay-like substance contains SiO.sub.2 in a range from about 45 to 70 percent by weight and Al.sub.2 O.sub.3 in a range from about 15 to 40 percent by weight and has a loss due to heating which lies in the range from about 5 to 15 percent by weight. 5. The method as defined in claim 1 wherein the additive for suppressing the volatility of the alkali metals and alkaline earth metals comprises about 1 to 3 parts by weight TiO.sub.2 powder compared to 20 parts by weight clay-like substance. 6. The method as defined in claim 1 wherein the additive for suppressing the volatility of the alkali metals and alkaline earth metals comprises about 1 to 5 weight percent TiO.sub.2 with respect to the kneaded mass obtained from process step (b). 7. The method as defined in claim 1 wherein the additive for suppressing the volatility of sulfate, molybdate and/or uranate comprises 1 to 5 weight percent BaO with respect to the kneaded mass obtained from step (b). 8. The method as defined in claim 1 wherein the additive for suppressing the volatility of phosphate comprises about 2 to 10 weight percent MgO with respect to the kneaded mass obtained from step (b). 9. The method as defined in claim 1 wherein the additive for suppressing the volatility of phosphate comprises about 2 to 10 weight percent BeO or ground natural beryllium with respect to the kneaded mass of step (b). 10. The method as defined in claim 1 wherein the continuous matrix comprises at least one cement selected from the group consisting of portland cement, iron portland cement, shaft furnace cement, trass cement, oil shale cement, alumina cement and mixtures thereof. 11. The method as defined in claim 1 wherein the continuous matrix comprises a fired ceramic produced from (1) at least one clay-like substance selected from the group consisting of pottery clays, stoneware clays, porcelain clay mixtures, and kaolin and (2) at least one cement selected from the group consisting of portland cement, iron portland cement, shaft furnace cement, trass cement, oil shale cement, and alumina cement in a weight ratio range of clay-like substance to cement of 10:1 to 4:1. 12. The method as defined in claim 1 wherein the continuous matrix is made of a copper-zinc alloy. 13. The method as defined in claim 1 wherein the continuous matrix is made of a copper-tin alloy. 14. The method as defined in claim 1 wherein the continuous matrix is made of lead or a lead alloy having a lead content of more than 50 percent by weight. 15. The method as defined in claim 1 wherein the adjusting of the pH is effected by the addition of a strongly alkali solution. 16. The method as defined in claim 1 which comprises adjusting the pH of said evaporate by denitrating. 17. The method as defined in claim 16 wherein the denitrating is effected with formaldehyde. 18. The method as defined in claim 1 which comprises adjusting the pH of the evaporate by denitrating with formic acid. 19. The method as defined in claim 1 which further comprises measuring the water and NO.sub.x content of gases given off during the drying and calcining stages of step (d) and varying the time and temperature of the drying and calcining stages as a function of the measured water and NO.sub.x content. 20. Method for solidifying high radioactivity aqueous waste concentrates, medium radioactivity aqueous waste concentrates, actinide containing aqueous waste concentrates, or suspensions of fine-grained solid wastes suspended in water, which concentrates or suspensions contain a metal ion and/or metal oxide, for final noncontaminating storage in which the waste concentrates or the suspensions are subjected together with an absorbing and/or hydraulically binding inorganic material, to a ceramic firing process so as to produce a solid sintered body, comprising the steps of: 21. The method as defined in claim 1, wherein said natural, stable mineral is nepheline. 22. The method as defined in claim 1, wherein said natural, stable mineral is anorthite. 23. The method as defined in claim 1, wherein said natural, stable mineral is noselite. 24. The method as defined in claim 1, wherein said natural, stable mineral is sodalite.
062263412	abstract	A neutronic reactor comprising an active portion containing material fissionable by neutrons of thermal energy, means to control a neutronic chain reaction within the reactor comprising a safety device and a regulating device, a safety device including means defining a vertical channel extending into the reactor from an aperture in the upper surface of the reactor, a rod containing neutron-absorbing materials slidably disposed within the channel, means for maintaining the safety rod in a withdrawn position relative to the active portion of the reactor including means for releasing said rod on actuation thereof, a hopper mounted above the active portion of the reactor having a door disposed at the bottom of the hopper opening into the vertical channel, a plurality of bodies of neutron-absorbing materials disposed within the hopper, and means responsive to the failure of the safety rod on actuation thereof to enter the active portion of the reactor for opening the door in the hopper.
	summary
	abstract	A reflective mask (e.g., an EUV reflective mask) and a method of making such a mask are disclosed. The mask includes an absorbent substrate and a reflective coating overlying the substrate. The reflective coating is patterned to include a circuit design that is to be transferred onto one or more wafers, and more particularly onto one or more die on the wafers, during semiconductor fabrication processing. The mask includes no other radiation absorbent material, and the occurrence and severity of dead zones, which commonly occur in conventional reflective masks and which degrade the fidelity of pattern transfers, are thereby mitigated. A methodology for inspecting the mask via the transmission of visible, UV or deep-UV radiation through the mask is also disclosed.
	claims	1. A method of lowering the electrochemical corrosion potential of metal alloy cooling tubes in a water-cooled nuclear reactor, said tubes having a surface exposed to an aqueous liquid containing hydrogen peroxide, comprising the step of injecting matter into said liquid, wherein said matter is selected from the group consisting of elemental manganese, elemental copper, elemental cadmium, oxides thereof, and mixtures thereof. 2. The method as claimed in claim 1 wherein said metal alloy is selected from the group consisting of carbon steel, alloy steel, zirconium stainless steel, nickel-based alloys, cobalt-based alloys and mixtures thereof. claim 1 3. The method as claimed in claim 1 wherein said matter is capable of adsorbing said hydrogen peroxide. claim 1 4. The method as claimed in claim 3 , wherein said metal alloy is a zirconium alloy and said matter is selected from the group consisting of elemental manganese, oxides thereof, and mixtures thereof. claim 3
	abstract	A TIP monitoring control equipment has: a process computer, a TIP control panel, and data transmitting unit. The process computer includes a operation input unit, a TIP scanning unit, a first TIP level data transmitting and receiving unit, and a TIP level data storage unit. To a first TIP level data transmitting and receiving unit, an LPRM level signal, an APRM level signal and TIP level data accumulated in the TIP control panel are input in synchronization with a TIP position signal. The TIP control panel includes a TIP driving control unit, a TIP level processing unit, a TIP position processing unit, a TIP level data accumulation unit and a second TIP level data transmitting and receiving unit. The second TIP level data transmitting and receiving unit transmits TIP level data accumulated in the TIP level data accumulation unit to the process computer via the data transmission unit.
	summary
	abstract	A neutron source rodlet assembly having a separate source capsule assembly that is not encapsulated within the neutron source rodlet assembly. The neutron source rodlet assembly is made up, at least in part, of a neutron source positioning rodlet assembly and the source capsule assembly configured such that assembly together is feasible at a remote site and they can be shipped separately. The source capsule assembly has outer and inner capsules with the outer capsule having a threaded stud at one end that mates with a complimentary threaded recess on the neutron source positioning rodlet assembly. The inner capsule contains a neutron source. The neutron source positioning rodlet assembly and the source capsule assembly are locked together at their interface when the threaded joint is completely tightened. A secondary neutron source material may also be encapsulated within a hollow portion of the neutron source positioning rodlet assembly.
047626470	claims	1. A method for reducing the volume of radioactive material comprising between about 30 w% to about 60 w% spent ion exchange resin and between about 40 w% to about 70 w% of a filter aid, said filter aid reactive therewith at an elevated temperature said method comprising: dewatering the spent ion exchange resin, heating the dewatered resin to the elevated temperature, and compressing the dewatered resin heated to the elevated temperature with a force of at least about 2000 psi for a period of time sufficient to cause the resin to sinter and become rewet stable. dewatering the spent ion exchange resin, heating the dewatered resin to at least about 230.degree. C., and compressing the dewatered resin heated to at least about 230.degree. C. with a force of at least about 2000 psi for a period of time sufficient to cause the resin to sinter and become rewet stable. 2. The method of claim 1 wherein said ion exchange resin contains acidic reactive groups. 3. The method of claim 2 wherein said acidic reactive groups are carboxylic acid. 4. The method of claim 2 wherein said acidic groups are sulfonic acid. 5. The method of claim 1 wherein said ion exchange resin contains basic groups. 6. The method of claim 5 wherein said basic group is selected from the group consisting of primary amine, secondary amine, tertiary amine, quaternary ammonium and mixtures thereof. 7. The method of claim 5 wherein said basic group is hydroxyl. 8. The method of claim 1 wherein said filter aid contains hydroxyl groups. 9. The method of claim 1 wherein said filter aid is cellulose based. 10. A method for reducing the volume of radioactive material comprising substantially between about 30 w% to about 60 w% spent ion exchange resin and between about 40 w% to about 70 w% cellulose filter aid, said method comprising: 11. The method of claim 1 wherein said compressing is to at least about 4300 psi. 12. The method of claim 1 wherein said compressing is performed by a ram press. 13. The method of claim 1 wherein said compressing is performed by an extrusion press. 14. The method of claim 1 wherein said heating and compressing is performed by using heated inert gas to apply isostatic pressure to the resin. 15. The method of claim 10 wherein said heating and compressing are performed for a period of at least 20 minutes. 16. The method of claim 1 wherein said compressing is performed by a plurality of compression steps.
	abstract	A method is provided for fabricating precision x-ray collimators including precision focusing x-ray collimators. Fabricating precision x-ray collimators includes the steps of using a substrate that is electrically conductive or coating a substrate with a layer of electrically conductive material, such as a metal. Then the substrate is coated with layer of x-ray resist. An intense radiation source, such as a synchrotron radiation source, is utilized for exposing the layer of x-ray resist with a pattern of x-ray. The pattern delineates a grid of apertures to collimate the x-rays. Exposed parts of the x-ray resist are removed. Regions of the removed x-ray resist are electroplated. Then remaining resist is optionally removed from the substrate. When exposing the layer of x-ray resist with a pattern of x-ray for non-focusing collimators, the substrate is maintained perpendicular to impinging x-rays from the synchrotron radiation source; and the substrate is scanned vertically. For precision focusing x-ray collimators, the substrate is scanned vertically in the z-direction while varying the angle of inclination of the substrate in a controlled way as a function of the position of the z-direction during the scan.

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