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	description	This application is a divisional of U.S. patent application Ser. No. 11/244,088, filed Oct. 4, 2005, which claims the benefit of U.S. Provisional Patent Application Ser. No. 60/620,304 filed by Manoj Prasad, Neal J. Snyderman, and Mark S. Rowland Oct. 19, 2004 and titled “Absolute Nuclear Material Assay.” U.S. Provisional Patent Application Ser. No. 60/620,304 is incorporated herein by this reference. The United States Government has rights in this invention pursuant to Contract No. W-7405-ENG-48 between the United States Department of Energy and the University of California for the operation of Lawrence Livermore National Laboratory. 1. Field of Endeavor The present invention relates to nuclear material assay and more particularly to an absolute nuclear material assay. 2. State of Technology United States Patent Application No. 2005/0105665 by Lee Grodzins and Peter Rothschild for a system of detection of neutrons and sources of radioactive material, published May 19, 2005, provides the following state of technology information: “There is a need to find sources of radiation and other nuclear material that are clandestinely transported across national boundaries. The sources of clandestine nuclear material may be in the form of “dirty bombs” (e.g., a conventional explosive combined with radioactive nuclides designed to spread radioactive contamination upon detonation), fissile material, and other neutron and radiation emitting sources that may present a hazard to the public. During recent years, the United States government has placed mobile vehicles at strategic areas with gamma ray detectors dedicated to the task of finding fissile material. Atomic explosives may be made from 235U, a rare, naturally occurring, isotope of uranium that lives almost 109 years, or 239Pu, a reactor-made isotope that lives more than 104 years. 235U decays with the emission of gamma ray photons (also referred to as ‘gammas’), principally at 185.6 keV and 205.3 keV. 239Pu emits a number of gamma rays when it decays, the principal ones being at 375 keV and 413.7 keV. These gamma rays are unique signatures for the respective isotopes. But fissile material invariably contains other radioactive isotopes besides those essential for nuclear explosives. For example, weapons grade uranium may contain as little as 20% 235U; the rest of the uranium consists of other isotopes. The other uranium and plutonium isotopes reveal their presence by gamma rays emitted by their daughters. For example, a daughter of 238U emits a high energy gamma ray at 1,001 keV; a daughter of 232U, an isotope present in fissile material made in the former USSR, emits a very penetrating gamma ray at 2,614 keV; and a daughter of 241Pu emits gamma rays of 662.4 keV and 722.5 keV.” U.S. Pat. No. 4,201,912 issued May 6, 1980 to Michael L. Evans et al and assigned to The United States of America as represented by the United States Department of Energy, provides the following state of technology information: “A device for detecting fissionable material such as uranium in low concentrations by interrogating with photoneutrons at energy levels below 500 keV, and typically about 26 keV. Induced fast neutrons having energies above 500 keV by the interrogated fissionable material are detected by a liquid scintillator or recoil proportional counter which is sensitive to the induced fast neutrons. Since the induced fast neutrons are proportional to the concentration of fissionable material, detection of induced fast neutrons indicates concentration of the fissionable material.” U.S. Pat. No. 4,617,466 issued Oct. 14, 1986 to Howard O. Menlove and James E. Stewart and assigned to The United States of America as represented by the United States Department of Energy, provides the following state of technology information: “Apparatus and method for the direct, nondestructive evaluation of the .sup.235 U nuclide content of samples containing UF.sub.6, UF.sub.4, or UO.sub.2 utilizing the passive neutron self-interrogation of the sample resulting from the intrinsic production of neutrons therein. The ratio of the emitted neutron coincidence count rate to the total emitted neutron count rate is determined and yields a measure of the bulk fissile mass. The accuracy of the method is 6.8% (1.sigma.) for cylinders containing UF.sub.6 with enrichments ranging from 6% to 98% with measurement times varying from 3-6 min. The samples contained from below 1 kg to greater than 16 kg. Since the subject invention relies on fast neutron self-interrogation, complete sampling of the UF.sub.6 takes place, reducing difficulties arising from inhomogeneity of the sample which adversely affects other assay procedures.” U.S. Pat. No. 3,456,113 issued Jul. 15, 1969 to G. Robert Keepin provides the following state of technology information: “An apparatus and method of detecting, identifying and quantitatively analyzing the individual isotopes in unknown mixtures of fissionable materials. A neutron source irradiates the unknown mixture and the kinetic behavior of the delayed neutron activity from the system is analyzed with a neutron detector and time analyzer. From the known delayed neutron response of the individual fission species it is possible to determine the composition of the unknown mixture. Analysis of the kinetic response may be accomplished by a simple on-line computer enabling direct readout of isotopic assay.” Features and advantages of the present invention will become apparent from the following description. Applicants are providing this description, which includes drawings and examples of specific embodiments, to give a broad representation of the invention. Various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this description and by practice of the invention. The scope of the invention is not intended to be limited to the particular forms disclosed and the invention covers all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the claims. The present invention provides a system of absolute nuclear material assay of an unknown source. The present invention provides a system that relates, in detail, a correlated or uncorrelated chain of neutrons with what appears in an instrument (i.e., relates physical parameter to a measured quantity). How the chain of neutrons is used was traditionally related in a process that connects count sums to physical parameters of interest, such as multiplication. The limitations of prior art start with and are rooted in approximations in the detailed description of the neutron chain. These approximations, in the details of exactly how a chain is described and evolves in time, conspire to make the process of relating chains to physical parameters highly unstable. Prior art therefore relies on a process of calibration. For example, calibration means that of the five parameters needed to describe a physical system, four are determined independent of an assay measurement. The old assay process then proceeds by assuming the four parameters apply and are considered with a measurement of the fifth parameter, to be extracted from the assay measurement. In the present invention, the assay solution comes from the solution of a coupled set of equations where all five parameters are used to solve for a physical parameter of interest, such as multiplication. The present invention benefits from a complete understanding of an arbitrary chain and variously allows the extraction all five parameters, or four parameters given only one, or three parameters given only two, etc. In the present invention neutrons are measured in a neutron detector and five parameters are determine (mass, multiplication, alpha ratio, efficiency, and time constant) that describe the object that is being assayed. The present invention makes an assay for the purpose of determining these five parameters, given that one does not know these five parameters. A neutron is created by a physical process, either fission or an inducing nuclear reaction. The created neutron or neutrons then interact with the environment. If the environment contains more nuclear material (i.e., uranium), the first neutrons may create more neutrons by causing more fission or other nuclear reactions. The first and second and subsequent neutrons are the chain. A chain may start with an alpha particle creating a single neutron that subsequently creates hundreds of fissions. Another chain may start with a spontaneous fission creating three neutrons that go on to create hundreds of fissions. These chains evolve over time and some of the neutrons are absorbed or lost. Finally, some members of the chain are captured in a detector. The final captured neutrons may be counted as a simple sum or observed as a time dependent rate. What may start out as a chain of 1000 neutrons may result in a count of two neutrons during some snippet of time, in a detector. The specific numerical process of relating the relevant physical parameters (mass, multiplication, alpha ratio, efficiency, and time constant) to an observed quantity (how many 2's) is based on approximations in the prior art. Describing these chains, with all the numerical detail requires a way to relate the five physical parameters to how the chains are created. The present invention provides a method of absolute nuclear material assay of an unknown source comprising counted neutrons from the unknown source and uses a model (theory) to optimally fit the measured count distribution. The present invention begins by analytically solving for and efficiently computing the entire fission chain probability distribution for any given set of physical parameters (mass, multiplication, alpha ratio, efficiency, and time constant). This fission chain distribution is then used to simulate a data stream from which time dependent count distributions are constructed. The model randomly initiates fission chains at a rate dependent on the measured source strength and samples from the analytical fission chain probability distributions to artificially create data with statistical fluctuations with finite time counting. This approach allows the most direct modeling of the data as it is actually taken. It also allows complete control in modeling issues related to finite sampling, truncation errors from inherently truncated data, and dead time effects in the detector. Previous art could only compute the first few moments of the full idealized fission chain distribution and relate these to moments of measured data. The previous art is fundamentally flawed in modeling finite sample truncated data with idealized infinite population moments. This flaw manifests itself in an erratic and unstable reconstruction of the unknown physical parameters. The approach of the present invention, based on analytical fission chain probability distribution, is able to robustly and stably reconstruct physical parameters. A far more reaching significance of the present invention is that it provides a complete theoretical framework for modeling the entire neutron count distribution, not just its first few moments. Any measured count distribution and its model made with the five, or even more parameters, may be quantitatively compared for the purpose of optimally reverse engineering the 5 or more parameters that describe the unknown. Previous art based on the first few moments can only get at some small subset of the information contained in the data, and even then is flawed by issues of finite sample size and truncation errors. (Other parameters include, but are not limited to background contributions, external sources adding counts, (n,2n) neutron sources . . . .) The present invention provides a method of absolute nuclear material assay of an unknown source comprising counting neutrons from the unknown source and providing an absolute nuclear material assay utilizing a sampling method to distribute theoretical count distributions over time. The method utilizing a random sampling of a count distribution to generate a continuous time-evolving sequence of event-counts by spreading the count distribution in time. The present invention also provides an apparatus for absolute nuclear material assay comprising a multigate neutron multiplicity counter, a processor that solves three moment equations, a processor that provides fit to actual time dependence of the moments to get proper asymptotic moments, a processor that uses the estimated parameters to compute full count distribution, a processor that compares truncated data moments with untruncated and truncated theoretical moments, and a processor that provides adjustments to reduce bias. The present invention has use in providing an assay of nuclear material. The present invention also has uses in providing the amount of moderator and in providing a neutron lifetime. The present invention can be used to providing an operator a simple system for obtaining the mass, multiplication, detector efficiency, and the alpha-decay-created neutron rate. The invention is susceptible to modifications and alternative forms. Specific embodiments are shown by way of example. It is to be understood that the invention is not limited to the particular forms disclosed. The invention covers all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the claims. Referring to the drawings, to the following detailed description, and to incorporated materials, detailed information about the invention is provided including the description of specific embodiments. The detailed description serves to explain the principles of the invention. The invention is susceptible to modifications and alternative forms. The invention is not limited to the particular forms disclosed. The invention covers all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the claims. Fission is defined as the emission of multiple neutrons after an unstable nucleus disintegrates. For example, Pu240 decays at a rate of about 400 fissions per second per gram of Pu240 atoms. When the fission occurs, multiple neutrons are emitted simultaneously, with the number ranging from zero to eight neutrons. The present invention provides a system that utilizes a set of parameters that describe an unknown mass of fissile material. This simultaneous neutron emission characteristic is unique to fission. The present invention provides a system that utilizes a multiplicity counter and a neutron detector that is set up to see time grouped neutrons. The present invention has use in providing an operator a simple system for obtaining the mass, multiplication, detector efficiency, and the alpha-decay-created neutron rate. The characteristic of fission is that neutrons emit in groups. Random sources of neutrons are emitted with no regard for grouping, however, since the appearance of these neutrons at the detector are randomly spread in time, some may accidentally appear in close temporal proximity. An example is a neutron detector that counts neutrons for short periods of time, say ½ milli-second. This example time corresponds to a typical neutron diffusion time in a typical detector, the choice of which depends on the detector design and is not the subject here. If the ½ msec. period is counted once, the count may be three counts, or some other integer number, including zero. It is desirable to select an appropriate observation time, two to three times the typical neutron diffusion time, and then repeat the sampling of counts period many times to produce a histogram of counts described as the number of occurrences of each multiplet group (i.e., number of times 0,1,2,3. . . were observed, in sum, over say 10,000 repeated detection periods). Fission is unique in that it creates real correlations, while non-fission neutron sources create accidental correlations. The present invention provides a system that utilizes new developments in how fission neutron chains are modeled to simplify and remove problems related to the assay of unknown packages of fissioning material. In general, the present invention provides a system that describes the evolution of fission chains with enough detail that universal procedures can be defined for absolute assay. The absolute assay does not need pre-defined facts or assumptions about the neutron detector efficiency (e), neutron lifetime (L), instrumentation dead-time losses (D), the terrestrial background (B), or the fraction of alpha-decay-induced neutrons (A) while endeavoring to obtain neutron multiplication (M) and mass of fissioning material (m). Counting neutrons by looking for time-correlated groupings is called multiplicity counting. The groupings arise from the fission process where a portion of a fission chain is detected. The analysis of this type of data assists in deriving mass, multiplication, detector efficiency, and alpha ratio (mMeA). Other factors in the analysis include neutron lifetime (L), measurement gate width (T), the maximum size of neutron multiplets observed (n), the background correlation and count rate (B), and the generalized Poisson exponent Λ (Λ). Traditionally, the count rate (singles) and the number of doubles are used to solve for up to two of the parameters, unfortunately with a significant dependence on quantitative knowledge of the other parameters. Measurement of the number of singles and doubles is limited additionally because of the necessity of incomplete sampling of the fission chains (since no one can count for an infinite time). Prior approaches assume a complete sampling of the fission chain. The present invention provides a system that utilizes a process where the partial and full fission chain details are calculated exactly and are used to correctly interpret the measurements. The present invention provides a system that utilizes allows solving for all of the unknown parameters listed above. The premise for (definition) multiplication is that all neutrons in the fission chains are accounted for in the definition of nubar and multiplication (M). Nubar of the fission chain (N) and M must relate exactly (probability of fission=p) M=1/(1−pN). The first moment of the induced fission chain, started from one neutron, is (1−p)M and is what is intended to be measured. In practice the first moment is not actually measured because the populations of neutrons are always sampled incompletely. M is the multiplication defined for the full population. Measurement gives an incomplete sampling of the population and is always biased (incorrect) because of the finite sampling time. When the measured samples are biased, they no longer relate properly to the M derivation, therefore M is usually derived only approximately. The incomplete sampling problem applies to higher moments of the fission chain. These errors propagate to the other derived unknowns, regardless of how many moments are used in an analysis. Other errors arise from mistakes in understanding the matrix of unknown source containers (e.g., errors in L, A, e, and B). The present invention provides a system that utilizes measurements made with a multi-gate neutron multiplicity counter. A fit to the actual time dependence of the moments is used to get the proper asymptotic moments and dead-time losses inherent in the data. Since H-C2 inversion leads to estimates that are biased (wrong) because of the finite sampling problem and dead-time, there are two paths to solve for the rest of the parameters. One is to use the Prasad theory to compute libraries of count distributions that may be used as a lookup table and the other is to use the H-C style estimated parameters to compute the full count distribution that would have been measured if there was no finite sampling error. The present invention provides a system that compares the truncated data moments (measurement) with untruncated and truncated theoretical moments. The present invention provides a system that utilizes extending the moments approach to more unknowns. Also, using moments is the same as using only part of the measured data, in contrast to actually fitting the measured count distribution to a library of count distributions (theory). The present invention provides a system that utilizes furthering the field by fitting the measurement to theoretically calculated count distributions to find the optimal set of parameters that would explain the count distribution. Fitting the full count distribution is a better approach because it uses all the information in the count distribution. The present invention provides a fitting approach that can extract all unknowns, in contrast to the prior situation of deriving at most three unknowns from three moments. The present invention provides a system that extends the H-C approach by adding a new method for dead-time correction most noteworthy for high multiplication, allows for truncation corrections, and allows direct comparison of data to parameter-based (mMea) count distributions that are generated as a proof test. The present invention provides a system that utilizes several new steps, not all required depending on analysis objectives or measurement uncertainties. One is to create a fitting algorithm that preferentially weights the longer T gates in a fitting analysis so the short mode effects minimally alter the resulting assmyptote. This is called a “T-cut” approach that prefers to extract the fundamental mode. Another method is to observe dead-time effects as a function of T, by simulation with Applicants new count distribution calculation method. This results in multi-mode time dependences that may be specified to the data fitting process, so that D may be extracted. With specific time-dependence specification and understanding, the fitting routine is stable as the only free parameter is D. Another method is to specify the time dependence in terms of the fission chain topology. This results in two modes for the second moment time dependence, and three modes for the third moment time dependence. By specifying these constrained sets of time dependences, the fitting routine will be stable as the only free parameter is the assmyptote and Lshort and Llong. The present invention provides a system that utilizes computing the exact fission chain time evolution and count distribution as a function of M, m, e A, L, T, Λ, D, and B so that Applicants can simulate measurements. Regarding dead-time (D), a precursor to using count distributions for assay requires a method to add the dead-time. The present invention provides a system that utilizes distributed theoretical count distributions over time (i.e., time-tagging the count events as they would have been seen during a measurement). This is different from using a monte-carlo transport technique because such a technique can not sample rare events thoroughly enough. The Prasad count distribution generation technique completely fills in all rare events exactly so it can be sampled with uniform weight to form an accurate time-tagged stream of synthetic data. The present invention provides a system that utilizes random sampling of a count distribution to generate a continuous time-evolving sequence of event-counts spreads the count distribution in time, as it would be seen during the measurement. This is done by randomly initiating fission chains at a rate dependent on the source strength and sampling from Applicants analytical theory of fission chain probability distributions to artificially create a stream of realistic data. The final step is to alter the time-tagged data with “coincidence-sum limits” to create dead time in time-tagged data or summed-count distributions. “Coincidence-sum limits” are the removal of selected time-tagged counts based on their being located within a D seconds to another count. Here D would be called the dead-time. The present invention provides a system that utilizes dealing with dead time when using H-C style moments based analysis. Similar to the process of generating a count distribution, the impact of dead-time is a non-linear process at the core of the count distribution generating function. Having identified the impact of dead time on count distributions, the present invention provides a system that parameterized these effects in the form of corrections to the moments.First moment: Dcr=Tcrexp(−DTcr−DLTr2f).Second moment: Dr2f=Tr2fexp(−D[3Tcr−LTr2f+{2LTr3f/Tr2f}].Third moment: Dr3f=Tr3fexp[−D[5Tcr−LTr2f+{(2TcrTr2f2+3LTr4f)/Tr3f}]Term Definition:Dcr, Dr2f, and Dr3f are the dead-time reduced count rate, second moment and third moments.Tcr, Tr2f, and Tr3f are the true, no-dead-time count rate, second moment, and third moments. The process to correct moment-based dead time is to use dead-time afflicted count distributions (Applicants theory or measurements) to observe (fit) the perturbation in time dependence. Time dependences created by this method may be used to fit observed measured data to infer the amount of dead-time D. Then one may sequentially compute corrections to the moments starting with the count rate: Dcr=Tcrexp(−DTcr−DLTr2f). Note the first iteration uses the observed data r2f. Then use Dr2f=Tr2fexp(−D[3Tcr−LTr2f+{2LTr3f/Tr2f}]. This next step uses the observed data r3f. Next, compute Dr3f=Tr3fexp[−D[5Tcr−LTr2f+{(2TcrTr2f2+3LTr4f)/Tr3f}]. Note this last step uses r4f which Applicants set equal to zero the first time through this process. Then one solves the three equations for the three unknowns. Now Applicants have the first estimate of Tcr, Tr2f, and Tr3f. Now Applicants feed them to the H-C algebra to get an estimate of mMeA. Next Applicants compute what Tr4f would be if the H-C algebra were correct. Then Applicants repeat the process started with the count rate data, now using the estimated Tr4f. Iteration continues until Tcr, Tr2f, Tr3f don't change from one iteration to the next. The final feed of Tcr, Tr2f, Tr3f into the H-C theory results in the true mMeA. The present invention provides a system that includes the effects of background. Background comes from cosmic ray interactions in the detector, surrounding structures, the unknowns' non-fissile mass, or fissioning uranium in terrestrial material. The basic idea is to use the generating function to reverse engineer the Λ's in background. The present invention provides a system that measures background with one of Applicants counters, in the presence of large masses of iron, lead, and polyethylene. Specifically, the process is to compute the natural log of the background count distribution generating function and solve for the Λ's. The present invention provides a system that utilizes the background as a free parameter in generating data to develop specific understanding, or to partition an unknown measurement into the fraction of background present at measurement time. This approach is technically superior since fission chains are created from the non-linear process and not simply additive environmental fissioning mass. The present invention provides a system that utilizes hundreds of time dependent gates T, is that a table of T versus L may be measured and used as a lookup to characterize the general state of moderation in an unknown object. The general method allows one to estimate the mass of hydrogenous moderator mixed with fissioning material. This knowledge is useful for waste barrels where hydrocarbons in the presence of alpha-emitting fissile material tend to liberate hazardous gases. The present invention provides a system that utilizes data visualization techniques that give insight into the physics and the impact of statistical fluctuations on derived quantities. The present invention comprises the steps of counting neutrons from the unknown source and providing an absolute nuclear material assay. In one embodiment the step of providing an absolute nuclear material assay comprises utilizing a sampling method to distribute theoretical count distributions over time. In one embodiment the step of providing an absolute nuclear material assay comprises utilizing a random sampling of a count distribution to generate a continuous time-evolving sequence of event-counts by spreading the count distribution in time. In one embodiment the step of providing an absolute nuclear material assay comprises altering time tagged data with “coincidence-sum limits” to create dead-time in time-tagged data or summed-count distributions. In one embodiment the step of providing an absolute nuclear material assay comprises observing fine resolution of T axis data to obtain modal structure. In one embodiment the step of providing an absolute nuclear material assay comprises H-C Point-model extension by using constrained sums of T dependence, to select best L to fit the data which includes T-cut approach to get long-mode asymptotes, multiple mode sums to get asymptotes, and single mode fits to see deviations from single mode behavior. In one embodiment the step of providing an absolute nuclear material assay comprises H-C Point-model extension by using constrained sums of T dependence, to select best L to fit the data which includes T-cut approach to get long-mode asymptotes, multiple mode sums to get asymptotes, and single mode fits to see deviations from single mode behavior and subsequently, use the best fit parameters from the model for analysis. In one embodiment the step of providing an absolute nuclear material assay comprises dead-time correction based on T dependence perturbations/shifts. In one embodiment the step of providing an absolute nuclear material assay comprises using L to estimate moderator mass around the fissioning material. In one embodiment the step of providing an absolute nuclear material assay comprises precomputing lookup tables of real-time computed count distributions for comparison to measured data. Referring to FIG. 1, one embodiment of a system of the present invention is illustrated. This embodiment of the system is designated generally by the reference numeral 100. The system 100 comprises a number of interconnected structural components. The structural components include a multigate neutron multiplicity counter 101, a processor that computes the time dependent moments 102, a processor that provides fits to deadtime, lifetime, biases, and allows the selection of the number of unknown parameters 103, a processor that solves for the unknown parameters 104, a processor that compares truncated data moments with untruncated and truncated theoretical moments 105, and a processor that checks for consistency and stability of solutions 106. The system 100 can be used to provide an assay of nuclear material and/or to provide the amount of moderator, neutron time constant, or other biases. Note that process 104 is described in tables 2 and 3, and process 105 depends on the process in table 1. Alternatively, count distributions may be generated from first principles. Table 3 includes a discussion and process ramp-up about BIGFIT. The present invention provides a system that relates, in detail, a correlated or uncorrelated chain of neutrons with what appears in an instrument (i.e., relates physical parameter to a measured quantity). How the chain of neutrons is used was traditionally related in a process that connects count sums to physical parameters of interest, such as multiplication. The limitations of prior art start with and are rooted in approximations in the detailed description of the neutron chain. These approximations, in the details of exactly how a chain is described and evolves in time, conspire to make the process of relating chains to physical parameters highly unstable. Prior art therefore relies on a process of calibration. For example, calibration means that of the five parameters needed to describe a physical system, four are determined independent of an assay measurement. The old assay process then proceeds by assuming the four parameters apply and are considered with a measurement of the fifth parameter, to be extracted from the assay measurement. In the present invention, the assay solution comes from the solution of a coupled set of equations where all five parameters are used to solve for a physical parameter of interest, such as multiplication. The present invention benefits from a complete understanding of an arbitrary chain and variously allows the extraction of all five parameters, or four parameters given only one, or three parameters given only two, etc. In the present invention neutrons are measured in a neutron detector and five parameters determine (mass, multiplication, alpha ratio, efficiency, and time constant) that describe the object that is being assayed. The present invention makes an assay for the purpose of determining these five parameters, given that one does not know these five parameters. A neutron is created by a physical process, either fission or an inducing nuclear reaction. The created neutron or neutrons then interact with the environment. If the environment contains more nuclear material (i.e., uranium), the first neutrons may create more neutrons by causing more fission or other nuclear reactions. The first and second and subsequent neutrons are the chain. A chain may start with an alpha particle creating a single neutron that subsequently creates hundreds of fissions. Another chain may start with a spontaneous fission creating three neutrons that go on to create hundreds of fissions. These chains evolve over time and some of the neutrons are absorbed or lost. Finally, some members of the chain are captured in a detector. The final captured neutrons may be counted as a simple sum or observed as a time dependent rate. What may start out as a chain of 1000 neutrons may result in a count of two neutrons during some snippet of time, in a detector. The specific numerical process of relating the relevant physical parameters (mass, multiplication, alpha ratio, efficiency, and time constant) to an observed quantity (how many 2's) is based on approximations in the prior art. Describing these chains, with all the numerical detail requires a way to relate the five physical parameters to how the chains are created. This procedure is summarized in Table 1 below. TABLE 1 x = ∫ 0 s ⁢ ⅇ - λ ⁡ ( t ′ - t f ) ⁢ λ ⁢ ⁢ ⅆ t ′ = ⅇ λ ⁢ ⁢ tf ⁡ ( 1 - ⅇ - λ ⁢ ⁢ t ) , ⁢ y = ∫ t f t ⁢ ⅇ - λ ⁡ ( t ′ - t f ) ⁢ λ ⁢ ⁢ ⅆ t ′ = ( 1 - ⅇ - λ ⁡ ( t - t f ) ) , ⁢ Λ j = { ∫ - ∞ 0 ⁢ [ ∑ v = j ∞ ⁢ ⁢ P v ⁡ ( v j ) ⁢ ( ε ⁢ ⁢ x ) j ⁢ ( 1 - ε ⁢ ⁢ x ) v - j ] ⁢ F s ⁢ ⁢ ⅆ t f + ∫ 0 t ⁢ [ ∑ v ≡ j ∞ ⁢ ⁢ P v ⁡ ( v j ) ⁢ ( ε ⁢ ⁢ y ) j ⁢ ( 1 - ε ⁢ ⁢ y ) v - j } ⁢ F s ⁢ ⁢ ⅆ t f } . λ is lifetime, t is time ε is efficiency Fs is n/s (mass) Pv = f(M, v(snm)) A comes from a special case of a single neutron multiplying For example, the number of fives is: b s = ( Λ 5 + Λ 4 ⁢ Λ 1 + Λ 3 ⁢ Λ 2 + Λ 3 ⁢ Λ 1 2 2 ! + Λ 2 2 2 ! ⁢ Λ1 + Λ 2 ⁢ Λ 1 3 3 ! + Λ 1 5 5 ) ⁢ exp ⁡ [ - ( Λ 1 + Λ 2 + … ⁢ ) ] . Bn is the multiplet count in the measurement and is directly related to the five parameters with this calculation process. A multi-gate counter measures Bn as a function of lifetime and neutron number. Since degenerate use of the procedure of the present invention is possible, Applicants made a NMAC procedure. It is similar to the hage-Cifferelli moments approach, but the NMAC procedure extends that procedure by allowing solutions that may be truncated as all measurements are, allows detailed time dependent analysis to better understand time truncated measurements, allows for the inclusion of gamma-rays in the assay process, and allows for dead time correction for the second and higher moments. The NMAC procedure is summarized in Table 2 below. TABLE 2NMAC solves algebra solutions based on the first 3 moments.We always fit λ to determine neutron lifetime and therefore correct forasymptotic saturation.This leaves four unknowns to determine; m, M, A, ε.Case examples:Given one unknown and R1, R2, and R3, we solve for the remainingunknowns (e.g. Given A, we solve for m, M, and ε).Given two unknowns and R1 and R2, we solve for the remaining twounknowns (e.g. Given A and ε. we solve for m and M) A comparison of the NMAC procedure and the BigFit procedure is summarized in Table 3 below. TABLE 3Neutron Multiplicity Analysis Code (NMAC)Mass, Multiplication, Alpha, efficiency, Lambda are unknown.R2 = mass [ε2M2q2(D2s + M − 1(1 + A)D2] F(λt) and describes one of themoments of the count distribution, which is only a piece of the countdistribution information.NMAC solves algebra solutions based on the first 3 moments.We cannot know efficiency if we don't know the geometryWe cannot solve for five unknowns with three equations (e.g. y1, y2, y3)Higher moments algebra (y4, y5) depends too much on the tail, i.e. noisy.Algebra involves ratios of moments, where uncertainties in the momentscause large solution errors.BigFitAlternatively, count distributions may be generated from first principles.Count distributions are the complete realization of the fission chain,related to all of the measured physical parameters and therefore provideall the available information and therefore the most definitive connectionto the assay quantities that we want.As a process, template fitting searches for a match between an unknownmeasurement and a library of variations. It appears that a libraryof ~4,000 variations and about 106 counts is sufficient to provide agood match to the assay of the unknown. Referring to FIG. 2, an embodiment of a system utilizing the present invention is illustrated. This embodiment is designated generally by the reference numeral 200. The system 200 provides a system for absolute nuclear material assay of an unknown source. The system 200 comprises the steps of counting neutrons from the unknown source and providing an absolute nuclear material assay. In one embodiment, the step of providing an absolute nuclear material assay comprises utilizing a sampling method to distribute theoretical count distributions over time. In another embodiment, the step of providing an absolute nuclear material assay comprises utilizing a random sampling of a count distribution to generate a continuous time-evolving sequence of event-counts by spreading the count distribution in time. In another embodiment, the step of providing an absolute nuclear material assay comprises altering time tagged data with “coincidence-sum limits” to create dead-time in time-tagged data or summed-count distributions. In another embodiment, the step of providing an absolute nuclear material assay comprises observing fine resolution of T axis data to obtain modal structure. In another embodiment, the step of providing an absolute nuclear material assay comprises H-C Point-model extension by using constrained sums of T dependence, to select best L to fit the data which includes T-cut approach to get long-mode asymptotes, multiple mode sums to get asymptotes, and single mode fits to see deviations from single mode behavior. In another embodiment, the step of providing an absolute nuclear material assay comprises H-C Point-model extension by using constrained sums of T dependence, to select best L to fit the data which includes T-cut approach to get long-mode asymptotes, multiple mode sums to get asymptotes, and single mode fits to see deviations from single mode behavior and subsequently, use the best fit parameters from the model for analysis. In another embodiment, the step of providing an absolute nuclear material assay comprises dead-time correction based on T dependence perturbations/shifts. In another embodiment, the step of providing an absolute nuclear material assay comprises using L to estimate moderator mass around the fissioning material. In another embodiment, the step of providing an absolute nuclear material assay comprises precomputing lookup tables of real-time computed count distributions for comparison to measured data. Sources of fission neutrons can be statistically distinguished from random neutron sources. A random source produces a Poisson distribution, Equation ⁢ ⁢ ( 1 ) b n = C n n ! ⁢ ⅇ - C for the probability to detect a particular number, n, during a counting window, where C is the average number of counts during that counting time. A fission source produces a distribution with a larger width. Since fission chains produce multiple neutrons in bursts, the larger width, or larger fluctuation, is related to the probability to detect more than one neutron from the same fission chain. The form of the counting distribution for a fission source is a generalized Poisson distribution. Unlike the Poisson distribution that depends on only a single time dependent parameter, C=Rt, where R is the count rate, the generalized Poisson distribution depends on many, in principle even an infinite number, of time dependent parameters, Ak(t), k=1, 2, 3, . . . . If bn(t) is the probability to get n neuron counts in a time gate of length t, then, Equation ⁢ ⁢ ( 2 ) b n = b 0 ⁢ ∑ i 1 + 2 ⁢ i 2 + 3 ⁢ i 3 + ⁢ … ⁢ + ni n = n ⁢ Λ 1 i 1 ⁢ Λ 2 i 2 ⁢ ⁢ … ⁢ ⁢ Λ n i n i 1 ! ⁢ i 2 ! ⁢ ⁢ … ⁢ ⁢ i n ! where ik is the number of independent chains contributing k counts (for k=n, in=0 or 1, while for k=1, i1=0, 1, 2, . . . , n), andb0=exp[−(Λ1+Λ2+ . . . +Λn+ . . . )]. Equation (3) For example, the probability to get 5 counts is Equation ⁢ ⁢ ( 4 ) b 5 = ( Λ 5 + Λ 4 ⁢ Λ 1 + Λ 3 ⁢ Λ 2 + Λ 3 ⁢ Λ 1 2 2 ! + Λ 2 2 2 ! ⁢ Λ 1 + Λ 2 ⁢ Λ 1 3 3 ! + Λ 1 5 5 ! ) ⁢ exp ⁡ [ - ( Λ 1 + Λ 2 + … ) ] . If all the Lk but Λ1 are zero, then b5→Λ15e−Λ1/5!, a Poisson distribution. The term Λ15e−(Λ1+Λ2+ . . . )/5! represents the probability that each of the 5 counts was due to an independent random source, where only a single neutron is counted from each independent chain. The term Λ5e−(Λ1+Λ2+ . . . )L is the probability that all 5 counts arise from a common source, a single chain. The term Λ22Λ1e−(Λ1+Λ2+ . . . )/2!, for example, is the probability that the 5 counted neutrons arise from 3 independent random sources, two pairs of counts each have a different common ancestor, and an additional count arises from a third source. For a weak neutron source in a system of high multiplication, it is likely to get multiple counts from the same chain, but the chains are few and far between. For a strong source in a system of low multiplication, the probability of getting multiple counts from a single chain is small, while the probability of getting many counts, most from independent chains, is high. So clearly information about the source strength and multiplication are encoded in the counting distribution. Applicants would like to have a complete theory relating the material and detector properties to the time dependent counting distribution. This requires a more complete theory of fission chains. In this paper Applicants develop an analytic formula for the t→∞ fission chain, and, in the approximation that at most two neutrons are emitted in an induced fission, a closed form expression for the time evolving fission chain. These formulas apply in the point model approximation, in which spatial dependence and neutron spectrum are neglected. Referring again to FIG. 2, the system 200, comprises step 201 measurements with multigate neutron multiplicity counter, step 202 solve three moment equations, step 203, use fit to actual time dependence of the moments to get proper asymptotic moments, step 204 use the estimated parameters to compute the full count distribution, step 205 compare truncated data moments with untruncated and truncated theoretical moments, and step 206 making adjustments to reduce bias. Measurements are made with the multigate neutron multiplicity counter 101. Three moment equations are solved with the truncated asymptotes to estimate three of the unknowns (MmeA), given one parameter. A fit to the actual time dependence of the moments is used to get the proper asymptotic moments. Since the estimates are biased (wrong) because of the finite sampling problem, Applicants use the estimated parameters to compute the full count distribution that would have been measured if there was no finite sampling error. Then Applicants compare the truncated data moments (measurement) with untruncated and truncated theoretical moments. Adjustments to reduce bias in the moments or count distributions are then possible via a data entry window. 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.
	summary
	summary
	abstract	The invention relates to a motorized manipulator for positioning a TEM specimen holder with sub-micron resolution parallel to a y-z plane and rotating the specimen holder in the y-z plane, the manipulator comprising a base (2), and attachment means (30) for attaching the specimen holder to the manipulator, characterized in that the manipulator further comprises at least three nano-actuators (3a, 3b, 3c) mounted on the base, each nano-actuator showing a tip (4a, 4b, 4c), the at least three tips defining the y-z plane, each tip capable of moving with respect to the base in the y-z plane; a platform (5) in contact with the tips of the nano-actuators; and clamping means (6) for pressing the platform against the tips of the nano-actuators; as a result of which the nano-actuators can rotate the platform with respect to the base in the y-z plane and translate the platform parallel to the y-z plane.
	abstract	A control system allows controlling a nuclear facility in an evacuation area. The control system includes a control device in ordinary use disposed in a non-evacuation area, an emergency control device—for emergency in the evacuation area, a plant control facility connectable to the control device—and the emergency control device, a signal switching unit that switches from a normal coupling to an emergency coupling based on an emergency switch signal, a first selector switch in the non-evacuation area, a second selector switch-in the evacuation area, an AND circuit configured to output the emergency switch signal to the signal switching unit in the case where the emergency switch signal is input from the first selector switch and the emergency switch signal is input from the second selector switch.
	description	The present application claims the benefits of priority to GB 1317016.2, filed on Sep. 25, 2013, and GB 1411005.0, filed on Jun. 20, 2014. The entire content of each of the above referenced applications is incorporated herein by reference. The present invention relates to a collimator, particularly but not exclusively to a collimator for radiotherapy apparatus. Radiotherapy is a form of treatment for tumours and other lesions which involves directing a beam of ionising radiation toward the lesion. The radiation harms the tumour tissue and causes its reduction or elimination. However, the radiation is also harmful to healthy tissue around the lesion; although healthy tissue is slightly less susceptible to the effects of ionising radiation, measures are taken to limit the exposure of healthy tissue to the extent possible. One such measure is to direct the beam toward the lesion from a number of radial directions by mounting the radiation source in a treatment head which is movable with respect to the lesion, such as by being mounted on a rotatable gantry. Thus, the lesion (or part of it) remains in the beam at substantially all times whereas each individual section of healthy tissue around the beam is only exposed to the beam briefly. In this way, the dose delivered to the lesion can be a multiple of the dose delivered to healthy tissue remote from the lesion. Another measure is to collimate the beam so as to limit its lateral extent and avoid the unnecessary irradiation of healthy tissue. Modern collimators for radiotherapy devices are known as “multi-leaf collimators” and comprise an array of adjacent tungsten leaves, each of which is narrow so as to provide a high resolution but deep (in the direction of the beam) so as to provide an effective attenuation of the beam. Each leaf is moveable into and out of the beam, largely independently of those around it, so that the tips of the individual leaves can define a variable shape as required. Two such “banks” of leaves will usually be provided, on opposing sides of the beam aperture, thereby allowing a field to be defined within that aperture, of substantially any shape. An example of a multi-leaf collimator (MLC) is disclosed in our earlier application published as EP-A-0314214. There are however limits to the attenuation that can be provided by a multi-leaf collimator. In particular, rules govern the minimum distance between opposing leaves so as to prevent the leaves from jamming or being damaged. Further, whilst it may be permissible for one leaf to be extended so that its tip touches or very closely approaches the tip of the exactly opposite leaf, those tips are usually rounded so as to provide a small penumbra at the patient, and therefore there will be leakage from the gap between them. For these reasons, there is usually a “block collimator” in series with the multi-leaf collimator, in the form of a substantial block of tungsten that can be extended or retracted in a direction transverse to the movement direction of the leaves. Thus, it can cover a region outside the defined field where the entire width of the aperture needs to be covered. Typically, there will be a pair of block collimators, one either side of the beam, the or each block collimator being substantially square or rectangular, as seen in the direction of the radiation beam to be collimated. The block does impose a substantial weight penalty. The collimators are usually accommodated in the radiation source, which is to be rotated around the patient in order to allow the beam to be directed toward the lesion from a variety of radial directions. Thus, a reduction in this weight would be beneficial. Our earlier application EP2153448A1 described one such way of doing so. The collimator blocks are required to be of the order of 8 cm thick solid tungsten material. This imposes a significant weight burden. Correspondingly, the mechanism required to move a significantly greater mass of collimator block will be correspondingly heavier itself. Both of these increase the overall mass of the treatment head, which in turn causes the structure of the radiotherapy apparatus to deflect more, resulting in further complications for the compensating control systems. It should be borne in mind that most clinical accelerators place the treatment head at the end of a long arm which is mounted on a rotatable support so that the treatment head can be rotated around the patient. Additional mass at the end of that arm causes the arm to deform in a direction which will vary (relative to the treatment head) as the treatment head traverses in an arc around the patient. The present invention therefore seeks to provide an arrangement which is able to offer the necessary blocking of the radiation beam, whilst reducing mass over conventional arrangements. The present invention provides a collimator for a radiotherapy apparatus, comprising a block of radiation-attenuating material for moving into and out of a beam of therapeutic radiation having a depth and a front face forming the leading edge of the block when, in use, it is moved into the beam and one, two or more main rear faces opposite the front face which main rear face(s) together substantially define(s) the trailing edge of the block when, in use, it is moved into the beam, the or each main rear face being substantially planar in the direction of the depth of the block and non-parallel to the front face. Such an arrangement enables the size and therefore weight of the collimator to be reduced as compared to conventional block collimators, as will be further described below. There may be a single rear face, or there may be two rear faces which together form a concave V-shape in the block opposite the front face. The or each rear face is substantially planar and non-parallel to the front face. These arrangements are both simple and enable significant savings in block material and hence weight to be made; single rear face, or “wedge” embodiments, enable greater weight savings than similar implementations having two rear faces (or concave V-shaped embodiments), as will be explained below. Embodiments having three or more rear faces in a concave shape are technically feasible, but these are more complex to manufacture and provide little additional benefit in weight saving. The angle between the or each rear face and the front face is suitably determined so as to match the trajectory the leaves of an MLC take as they move between extremes of positioning with the trajectory of the collimator block, which is dependent on the speeds of movement of the MLC leaves and the collimator block; accordingly, this angle may be between 10 and 80 degrees, and may be between 30 and 60 degrees. There may be two side faces leading from the front face to the rear face (where there is only one rear face); this provides a safety margin when movement of the block collimator and MLC leaves is initiated. The side faces may be substantially parallel. The collimator may have a top and bottom face (as seen in the direction of the radiation beam which is collimated), and these faces may be planar; to the extent that they are planar these faces may be substantially parallel. Additionally or alternatively, these faces may be shaped as described in our EP2153448A1, so as to provide additional weight saving; in particular the edge of the collimator block at its front face (the front edge) may be of greater thickness than at least one region behind the front edge (i.e. towards the rear face(s), between the leading and trailing edges of the block. It is envisaged that the collimator blocks may be mountable in a radiotherapy apparatus so that they may be moved back and forth in a direction transverse to the front face. The collimator blocks may be shaped and configured so as to be moveable through an arc centred on the nominal point source of the radiation beam, as is known in the art. In other aspects, the invention also provides radiotherapy apparatus including such collimators, and methods of operating such radiotherapy apparatus. The present invention is predicated upon the movement of the leaves of an MLC. In one particular arrangement, where the MLC leaves are capable of travelling across the entire width of the aperture formed by the primary collimator edge, we have recognised that it is not necessary to have a collimator block which extends across the aperture for the entirety of its length (i.e. in the direction parallel to the direction of movement of the collimator block—“the movement direction”), because the main source of radiation leakage (the attenuation of which is a main objective of the collimator block) is not between the sides of the leaves but rather through the “gap” between opposing leaf tips. When the leaf tips are outside of the beam of radiation (i.e. extended fully across the aperture, so that the “gap” between the leaf tips is within the penumbra of the primary collimator edge and hence shielded from the radiation source) there is no radiation leakage as such, and the collimator block is not required to attenuate any radiation leakage. Accordingly, the collimator block need only be deep enough in the movement direction to cover the leaf tips while they move across the beam towards the primary collimator edge. Assuming that the leaves move from the centre of the aperture, between the two primary collimator edges, a concave V-shape can be provided (or cut) into the rear edge of the collimator block in such a way that the edge of this V-shape matches the trajectory the MLC leaves will take as the MLC leaves move and as the collimator block moves transversely thereto, and taking account of the speeds of movement of the MLC leaves and of the collimator block—which may be their maximum speeds, and/or may take account of their acceleration and/or deceleration. Depending on which side of the V the MLC leaves were last used, and on which side they are next to be used, a control system can determine which primary collimator edge the leaves next travel to. FIG. 1 is an isometric schematic view of one embodiment of a collimator block 2 which has a leading or front face 4, a main rear face 6 in the form of a V-shaped concave cut out formed by two substantially planar faces (only one, 6a being visible in the drawing). The collimator has two substantially planar side faces (only one 8a being visible in the drawing), and substantially planar faces to the top 10 and bottom (not visible). The collimator is moved in use in the direction of the arrows M. The distance S in the direction M between the front face 4 and the apex of the V-shape provides a safety margin, as will be described below. Note that FIG. 1 shows two small rear surfaces either side of the V-shaped cut-out; such an arrangement, provided the width (parallel to the front face 4 and transverse to the M axis) of these surfaces forms only a minor proportion of the entire width of the block 2, is within the scope of the claims, and the word “main” should be interpreted accordingly. FIG. 2 is a side view, showing the collimator block 2 beneath the opposed leaves 14a, 14b of a multi-leaf collimator, with a gap 16 between the tips of the opposed leaves; with reference to direction M in FIG. 1, in FIG. 2 the direction M is perpendicular to the plane of the drawing. The MLC leaves are movable to left or right in FIG. 2. Radiation beam B (produced by a linear accelerator, for example) is shaped by a primary collimator (not shown) so as to have the outline shown by the dotted lines. As shown in FIG. 2, the MLC leaves are fully withdrawn to one side of the radiation beam B, so that the gap is outside the beam B and therefore the MLC and collimator 2 in combination provide full shielding of the radiation. Referring now to FIG. 3, this top view shows successive positions of the MLC leaves 14a′, 14a″, 14a′″, 14b′, 14b″, 14b′″ as the MLC leaves move from the centre line 20 towards one side of the radiation aperture 20 created by the primary collimator (the aperture being illustrated between areas 18a, 18b, in which areas the radiation is fully shielded by the primary collimator (not shown)). As the MLC leaves move, so does the gap 16 between their tips; combining this movement with simultaneous movement of the collimator block 2, line 22a shows as a single vector line the trajectory of the gap 16 relative to the rear face 6 of the collimator block 2, where the angle of the rear face 6 is sufficient to ensure full shielding (i.e. to ensure that the collimator block 2 shields radiation which might pass through the gap 16). Line 22a is drawn in the case where the speed of movement of the MLC leaves 14a, 14b is approximately the same as that of the collimator block 2, so that line 22a is at an angle of at about 45 degrees to centre line 20 (which corresponds to the angle of the rear face 6 to the direction M). Line 22b illustrates the case where the MLC speed is somewhat slower, so that the angle to the centre line 20, and thus the angle of the rear face 6 to direction M, is decreased, Those skilled in the art will readily understand the geometries suitable for different types of MLC and collimator block movement apparatus. In most commercially available MLC/collimator arrangements, angles between 10 and 80 degrees would be feasible, and angles between 30 and 60 degrees represent a good compromise between the movement capabilities of the apparatus and enabling a significant reduction in weight of the collimator block. It will be appreciated that the above arrangements assume a constant speed of movement of the MLC leaves and of the collimator block. Of course, in practice these elements are normally made of a dense material such as tungsten, which have considerable inertia, and therefore in practice the apparatus must accommodate the necessary acceleration and deceleration of the elements. This could be provided by a suitably programmed controller to control movement of the MLC leaves and/or collimator block appropriately, however the simple approach of providing a length S of collimator block 2 between the leading, front face 4 and the rear face 6 provides a suitable safety margin, thus ensuring that inertial effects do not allow the gap 16 to be unshielded whilst it moves towards a “parked” position, behind the penumbra 18b of the primary collimator. The same applies in the case where the MLC leaves are moving in the opposite direction, towards the penumbra 18a. Referring now to FIG. 4, FIG. 4a shows in plan view the collimator block 2 of FIGS. 1 to 3 (but without two small rear surfaces either side of the V-shaped cut-out in FIG. 1); as explained above, this V-shaped collimator block corresponds to the case where the MLC leaves move from the centre line 20 of the radiation beam to one side of the aperture 20. It is also possible for the MLC leaves to move from one side of the aperture 20 to the other. In this case it will be appreciated that the shape of the collimator block 2″ can be simpler, namely a “wedge” as shown in FIG. 4b. The collimator block 2″ of FIG. 4b is provided with the same safety margin S as in the previous embodiment, however the movement speeds are adjusted to provide the same overall length of collimator block 2″ (in the M direction) as was the case with the previous embodiment—meaning that there is a significant saving of material, and hence weight, compared to the first embodiment, as indicated by the shaded area A in FIG. 4b. 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. For example, although shown as symmetrical in FIG. 4a, the two main rear faces could be of different lengths so as to accommodate different speeds of movement of MLC leaves in different directions, and the apex of the V-shape could be central, as shown, or it could be offset to one or other side. Where there are more than two main rear faces, these will as before define a concave depression in the rear surface of the block, these rear faces may be arranged symmetrically or asymmetrically. As previously mentioned, it may be advantageous in some applications for the depth of the collimator block (i.e. into the plane of FIG. 4) to vary, such as by making the leading edge (adjacent the front face 4) thicker, or by profiling the block between its leading and trailing edges as described in EP2153448A1. Additionally or alternatively, the block may have a web of material, of lesser thickness than the remainder of the block, which is disposed against the rear face(s) so as to fit into the V-shaped space in the first embodiment or to render its appearance in FIG. 4a, or the appearance of the second embodiment in FIG. 4b, substantially rectangular. This web may be of the same material as the remainder of the block, and may be integral with it, and is useful for capturing any stray or scattered radiation; it may be disposed at any position vertically on the block (i.e. as shown in the vertical direction in FIG. 1. Where different variations or alternative arrangements are described above, it should be understood that embodiments of the invention may incorporate such variations and/or alternatives in any suitable combination.
	claims	1. A pattern inspection method for detecting a defect on a semiconductor device comprising:irradiating a beam to a plurality of dies to be inspected on the semiconductor wafer, the plurality of dies being selected arbitrarily in sequence,forming a first image of the plurality of dies to be inspected and a second image of the plurality of dies as reference dies according to an order of the sequence based on signals generated from an irradiation point of the beam,comparing the first image and the second image,detecting a difference between the first image and the second image, anddetermining whether there is a defect in the plurality of dies to be inspected or in the reference dies based on the difference detected. 2. A circuit-pattern inspection apparatus comprising:a beam source,a detector for detecting signals obtained from beam irradiation of a part of a specimen,a memory for storing the signals as an image,an operation unit for selecting an inspection die row scanned in sequence so that a die to be inspected and a separate reference die are consecutive in the sequence, anda processing unit for comparing images of one of the inspection die row stored in the memory with a reference image of one of the separate reference die stored in the memory, comparing images of another of the inspection die row stored in the memory with a reference image of another of the separate reference die stored in the memory, and for identifying defects on the die of the inspection die row. 3. The circuit-pattern inspection apparatus according to claim 2, wherein the operation unit for arbitrarily selecting a die to be inspected and the reference die which is not adjacent to any side of the die to be inspected,a computer program product for controlling a circuit-pattern inspection apparatus comprising a beam source, a detector for detecting signals obtained from beam irradiation of a part of a specimen, a memory for storing the signals as an image. 4. A program product for controlling a circuit-pattern inspection apparatus comprising a beam source, a detector for detecting signals obtained from a beam irradiation of a part of a specimen, a memory for storing the signals as an image, and an operation unit for selecting a plurality of dies in sequence to be inspected on a semiconductor wafer, the product comprising: executable code embodied in a readable medium, the executable code causing the apparatus to perform a sequence of steps comprising:(a) irradiating a beam to a plurality of dies to be inspected according to an order of the sequence,(b) forming a first image of the plurality of dies to be inspected and a second image of the plurality of dies as reference dies according to the order of the sequence based on signals generated from an irradiation point of the beam,(c) comparing the first image and the second image, and(d) detecting a difference between the first image and the second image. 5. A circuit-pattern inspection apparatus comprising:a beam source;a detector for detecting signals obtained from beam irradiation of a part of a specimen;a memory for storing the signals as one or more images;an operation unit for arbitrarily selecting a plurality of dies in sequence to be inspected and storing images of the plurality of dies in memory, anda processing unit for comparing between images of the plurality of dies stored in the memory according to an order of the sequence, and for deteting defects on the plurality of dies to be inspected based on a result of the comparison. 6. The circuit-pattern inspection apparatus according to claim 5, wherein the operation unit sets the plurality of dies only in the circumferencial part of the specimen to be compared at a time. 7. The circuit-pattern inspection apparatus according to claim 5, wherein the beam source is a charged particle beam source and the detector is an electron detector for detecting electrons emitted from the specimen. 8. The circuit-pattern inspection apparatus according to claim 5, wherein the beam source is a light source and the detector is a light detector for detecting a reflection beam reflected from the specimen. 9. The circuit-pattern inspection apparatus according to claim 5, further comprising: a stage for moving the specimen, the stage being controlled by the processing unit. 10. The circuit-pattern inspection apparatus according to claim 9, wherein the processing unit controls the stage according to a selecting of the plurality of dies to be inspected by the operation unit to move ihe plurality of dies to be inspected to an irradiation point of the beam. 11. The circuit-pattern inspection apparatus according to claim 5, wherein the operation unit enables changing of an inspection order of the dies to be inspected after the setting the inspection order. 12. The circuit-pattern inspection apparatus according to claim 5, wherein the operation unit can add or delete a die to be inspected after selecting the dies to be inspected.
	abstract	A device for guiding a charged particle beam comprising a first superconducting nano-channel. In one embodiment, the device comprises a superconducting nano-channel consisting essentially of a superconducting material in the form of a tube having a proximal end, a distal end, and a bend disposed between said proximal end and said distal end. In another embodiment, the device is formed by a substrate, a first area of superconducting material coated on the substrate and having a first edge, a second area of superconducting material coated on the substrate and having a second edge, the first edge of the first area of superconducting material and the second edge of the second area of superconducting material are substantially parallel. In another embodiment, the device comprises a superconducting nano-channel formed by a plurality of nano-scale superconducting rods disposed around a central region.
044629567	description	DETAILED DESCRIPTION FIG. 1 shows one part of the cylindrical casing skirt 1 of the core the axis of which is vertical, in position in the reactor vessel. This casing skirt 1 is solid with a base plate 2 on which the fuel assemblies 24 constituting the reactor core rest. The base plate 2 is pierced with holes 5 for the cooling water to pass through the reactor core and holes 6 for positioning the partitioning apparatus. The apparatus also includes an upper plate 7 allowing the partitioning apparatus to be fixed. The assemblies 24 are held in fixed positions between the plates 2 and 7 which bound the core at its upper part and its lower part. FIG. 2 shows a part of the partitioning apparatus comprising boxes 8, 9, 10 and 11 juxtaposed with respect to each other at the periphery of the casing skirt 1, so as to provide in the central part of this casing the location for the reactor core constituted by the assemblies 24. The box 9 is constituted by two vertical plates 12 and 13, i.e., disposed in the longitudinal direction of the assemblies. The box 10, a sectional view of which at a vertical plane is represented in FIG. 1, is constituted by two vertical plates 14 and 15, disposed at right angles in accordance with the joint represented in detail in FIG. 4 and by a reinforcing plate 16 perpendicular to the plate 14 which is welded to the latter, at its outer face 17 which is directed towards the casing 1. As FIG. 4 shows, the two plates 14 and 15 have grooves 18a and 18b, respectively, machined in a direction perpendicular to their common joint faces 20 which form an angle of 45.degree. with the inner faces of the plates 14 and 15. A key 19 allows the faces 14 and 15 to be joined to constitute the inner wall of the box 10. The boxes 9 and 10 can also be joined together by means of a key 23 introduced into the grooves 24 and 25 provided in the vertical plates 13 and 14, respectively, over the whole of their length. The boxes 8 and 11 are constituted by very wide plates 27 and 28 respectively, with vertical stiffening plates 29 and 30 respectively welded to the outer face. The set of inner faces of the vertical plates 12, 13, 14, 27 and 28 consitute the bearing faces for the fuel assemblies 24 disposed at the periphery of the core. It is therefore clear that the boxes can be of several types, but in all cases they include at least two vertical plates rigidly joined and perpendicular to each other. FIG. 1 shows the box 10 in a sectional view at a vertical plane. This box 10 is constituted not only of vertical plates like 14 but also of horizontal reinforcing plates 32 pierced with holes 33 for passage of the cooling water. FIG. 2 shows that these reinforcing plates 32 are disposed in the dihedral angles provided between the vertical plates and that their exterior contour consists of a portion of a circle so that they bear on the annular bearing pieces 35 fixed on the interior wall of the casing skirt 1. FIG. 1 shows that the horizontal plates 32 and the annular bearing pieces 35 are disposed level with the brace-gratings 37 of the assembly 24. Orifices 40 are provided in the vertical plate 14 to balance the pressure between the reactor core and the interior of the box 10. The box 10 also includes an upper reinforcing plate 41 and a lower reinforcing plate 42 which are held by screws at the ends of the vertical plate 14. On the lower reinforcing plate 42, a hollow centering piece 43 is fixed which, when the box 10 is positioned, locates in a through hole 6 provided in the lower support plate 2. The lower plate 42 rests on the support plate 2 through a boss 59. The upper reinforcing plate 41 has orifices for passage of the cooling water 44 and an orifice 45 allowing the box to be fixed with respect to the upper plate 7. The apparatus for fixing the box to the upper support plate 7 is constituted by a centering piece in two parts 46 and 47, sliding one inside the other with interposition of a spring 48 borne by the upper reinforcing plate 41 of the box and by a bearing piece 49 solid with the upper plate 7. When the plate 7 is positioned above the boxes, the devices 49 come into position on the centering pieces 46, 47 which has the effect of compressing the spring 48 which allows the box to be fixed in position between the two plates 2 and 7. Each box is thus held in position without its fixing in any way preventing expansion of the box and displacements in the longitudinal direction. The box is not actually connected to the casing skirt 1 by any rigid fixing means, the boxes simply being supported through the reinforcing plates 32 on the bearing rings 35. FIG. 5 shows a variant of the apparatus for fixing the boxes with respect to the plates 2 and 7. In this variant, a centering piece 50 solid with the upper plate 7 engages in an opening 51 provided in the upper reinforcing plate 52 of the box. Leaf springs 54, solid with the reinforcing plate 52 of the box, are compressed by the plate 7 when this plate 7 is positioned above the reactor core. The box is thus held in position by the compression force of the springs, the lower reinforcing plate 53 of the box bearing a centering piece 55 which engages in a blind hole 6 in the support plate 2. The centering piece 55 has a thick median part 58 limiting the position of the box in height. The opening 51 provided in the plate 52 has a profiled shape allowing introduction of a tool for lifting the box to remove or position it. Openings 56 for the passage of water are provided in the lower plate 53 and openings 57 are also provided in the upper plate 52. FIGS. 6 and 7 show a box like the box 10 represented in FIG. 1, in which bars 60 and plates 61 have been inserted, in openings provided in the reinforcing plates 32, to absorb neutrons and limit radiation to the exterior of the core casing and the nuclear reactor vessel, or in addition to produce radioactive elements. FIGS. 6 and 7 also show an apparatus 63 for measuring the neutron power released by the core at the location concerned, for measuring the radiation dose received at this location and if necessary for injecting liquid poison or sampling cooling liquid in the vicinity of the reactor core. The boxes are disposed about the reactor core in the required number and according to a distribution determined to provide the assemblies 24 with a location corresponding exactly to the section of the reactor core. The boxes are assembled as shown in FIG. 3 by keys inserted in grooves cut in each of the vertical plates for contact between the boxes, so that leaking of fluid between the plates such as 13 and 14 is greatly limited. Positioning of the boxes inside the casing skirt 1, which is itself disposed in the reactor vessel, can clearly be carried out very easily since each box need simply be placed in position inside the casing skirt with a handling tool engaged in the opening provided in the upper reinforcing plate of the box. The box is then brought into contact with each of the bearing rings 35 of the casing skirt 1 through its horizontal reinforcing plates 32. When all the boxes have been put in place, the assemblies 24 which are to form the core can be positioned, and then the upper support plate 7 can be put in place. When this plate 7 is correctly oriented, the upper centering pieces come into position at each of the boxes which are themselves centered with respect to the base plate 2 by means of centering pieces solid with the lower reinforcing plates. The boxes are then held in position by compression of the springs the force of which is applied against the upper reinforcing plate of the box and the support plate 7. The principal advantage of the apparatus according to the invention is that it allows the partitioning apparatus to be more simply constructed, by separate, removable elements, so as to facilitate positioning of this partitioning apparatus and to allow the partitioning to move under the effect of expansion or stresses of mechanical origin or due to radiation. It is possible to fix the position of the boxes with respect to the casing 1 not only by means of centering pieces solid with the lower reinforcing plate of the box, but also by means of keys engaged in grooves provided in the horizontal reinforcing plates of the box and in the bearing rings of the casing skirt which are brought into coincidence when the box is positioned. It is also possible to provide devices for connecting the vertical plates of the boxes other than by the groove-and-key devices which have been described. It is also possible to provide means for fixing the vertical stiffening plates of these boxes other than by welded joints, e.g., by screw fixing means. It is also possible to envisage flexible coupling means between the boxes and the upper or lower support plates other than the spring apparatuses described. Connecting apparatuses of the pneumatic or hydraulic type are conceivable, for example. Also, the type of box which has been described has two vertical plates disposed at right angles, two vertical plates disposed at right angles and a reinforcing plate or a very wide vertical plate associated with the reinforcing plates welded to one of its faces. Very evidently other shapes of boxes are conceivable as a function of the arrangement of the core, as long as these boxes always include at least two vertical plates disposed at right angles. The horizontal reinforcing plates in the apparatus described are disposed so as to occur at a level corresponding to the brace-grating level of the fuel assemblies, but these horizontal reinforcing plates can obviously be arranged in a different distribution. Lastly, the partitioning apparatus described is applicable not only to pressurized water nuclear reactors but also to all water nuclear reactors and also to any other type of reactor with a core constituted by juxtaposed prismatic assemblies inside a casing bounding a space surrounding the core.
	description	The present invention concerns ion implanters and more particularly concerns serial ion implanters that process workpieces such as semiconductor wafers one at a time. Ion implanters of different designs are currently commercially available from a number of sources including Axcelis Technologies, Inc., assignee of the present invention. Two commercially available implanters are sold under the model designations MC3 and 8250. These tools create an ion beam that operates on batches of workpieces or on individual workpieces, one at a time. One typical application of an ion implanter is used to dope a semiconductor wafer with an ion impurity to produce a semiconductor material in the region treated by the ion beam. Although not limited to such wafers the invention has particular utility in such a doping process and the term workpiece and wafer are used interchangeably henceforth in this application. Single wafer ion implanters currently available for semiconductor device manufacturing are designed for implanting an entire surface of the wafer. It is desirable to be able to implant different regions of the wafer with different implant species or dose or energy to enable a multiple split, split lot device experiment to be conducted on a single wafer. Conducting multiple implants on different regions of the same wafer offers the opportunity to reduce process development costs and also improves control of the experiment since all process steps are carried out on the same wafer. U.S. Pat. No. 6,750,462 to Iwasawa et al concerns an ion implanting method that both scans an ion beam in an X direction and mechanically drives a substrate in a Y direction. An implanting step is featured for implanting ions separately for two implanted regions with different dose amounts of the substrate is executed plural times by changing at the center of the substrate a driving speed of the substrate. The present invention concerns an ion implanter having structure for serially implanting workpieces such as silicon wafers. Serial in this context means implanting one workpiece at a time. One exemplary embodiment of the invention includes a source that is spaced from an implantation chamber by an evacuated region. The source provides ions and in the region between the source and the implantation chamber the ions are accelerated to an appropriate energy for treatment of a workpiece such as a semiconductor wafer. An exemplary embodiment of an implanter provides a thin ribbon beam of ions that enter the implantation chamber. A workpiece support positions a workpiece within the implantation chamber and a drive moves the workpiece support back and forth through the thin beam of ions to perform controlled beam processing of the workpiece. A control provides a first control output coupled to limit an extent of the ribbon beam to less than a maximum amount and thereby limit ion processing of the workpiece to a specified region of the workpiece. The control provides a second control output coupled to the drive to control back and forth movement of the workpiece support. This results in the ion beam impacting a controlled portion of the workpiece. A typical control will include a programmable controller and an ability to program different recipes into the control. This flexibility allows, for example, non uniform ion implantation as a means of evaluating implanter performance. These and other aspects and features of the invention are described in greater detail in conjunction with the accompanying drawings. FIG. 1 is a schematic depiction of an ion implanter 10 such as Axcelis model MC-3 medium current ion implanter sold by the assignee of the present invention. Such an implanter is used for ion beam treatment of work-pieces such as silicon wafers for selective doping of those wafers. In such an implanter positive ions strike the work-piece after traversing a beam path from a source to an implanter station. Although the ion implanter 10 depicted in FIG. 1 is a medium current ion implanter other types of implanters including high energy implanters having a linac for accelerating ions are also within the scope of the invention. The exemplary ion implanter 10 includes an ion source 12 for emitting ions generated from a source material. Typical source materials are either gases injected into a source housing 14 or solids that are vaporized to produce a plasma of ions within the source housing. As is well known in the prior art such a source 12 typically includes an extraction electrode for causing ions to exit the housing 14 along a beam path away from the source. The implanter 10 depicted in FIG. 1 also includes a mass discriminating magnet 20 for bending ions away from an initial trajectory along a path of ion travel downstream from the ion source. Different species of the same ion are produced in the source 12 and the magnet discriminates between theses species. Ions of an undesirable mass are filtered by the magnet so that ions exiting the mass analyzing magnet 20 are of a single species of the ion used in beam treatment of a workpiece. The ion implanter 10 also includes a beam scanning structure 30 which is positioned to intercept ions subsequent to the mass discriminating magnet 20 and scan ions from side to side in a controlled manner to form a ribbon like ion beam having a width. In one known design the scanning structure uses an electrostatic field that is created between two scan plates that are approximately 15 cm long and spaced apart by 5 cm. This separation expands outwardly to a separation of about 7.5 cm at an exit end of the two scanning electrodes. Time varying voltages of up to +/−5 kilovolts of a controlled magnitude are applied to suitable amplifiers coupled to each plate to achieve a total plate voltage separation of 10 kv. Suitable sawtooth waveforms are applied by control electronics 26 (FIG. 5) to sweep the ions from side to side at a controlled frequency. Alternate means of creating a ribbom beam are use of time varying magnetic fields and use of structure that defines the beam exiting the source prior to species discrimination. Returning to the exemplary structure shown in FIG. 1, the system includes lens structures 40 that accept ions moving along diverging paths from the scanning structure 30 and bends them as they are accelerated across a gap between curved electrodes to create substantially parallel ion trajectories for ions leaving the lens structures 40. Subsequent to leaving the lens structures 40, the ions that make up the beam are moving in generally parallel directions and form a thin ribbon or ribbon-like beam 42. (See FIG. 2) The beam 42 passes through an energy filter 44 which deflects ions downward due to their charge. This downward deflection removes neutral particles that have entered the beam during the upstream beam shaping before entering the filter 44. A wafer 24 is moveably supported within an ion implantation chamber 50 by a workpiece support structure 100. Workpieces 24 (typically wafers) are inserted into the chamber 50 by means of a load lock 54 and moved to a wafer clamp 102 by an in vacuum robot 53. Outside the chamber 50 the wafers are manipulated by a robot 56 which extracts untreated wafers from a storage cassette 58 and returns treated wafers to a second cassette 60 or alternatively can return the treated wafers from the same cassette from which they were withdrawn. Generally, the extent of the ribbon ion beam 42 is sufficient to implant an entire implantation surface of the workpiece 24. That is, if the workpiece 24 has a diameter of 300 mm, control electronics 26 will appropriately energize the scanning electrodes 30 such that a horizontal extent or width, W (FIG. 2) of the ribbon ion beam 42 entering the implantation chamber will be at least 300 mm. As described below, the extent of the beam 42 is selectively limited to a narrower dimension for specialized implant control. As will be explained below, the workpiece support assembly 100 both supports and moves the workpiece 24 with respect to the ribbon ion beam 42 during implantation such that a desired implantation surface of the workpiece 24 is controllably implanted with ions. As mentioned previously, in addition to the scanning technique described above, those of skill in the art will recognize that the ribbon shape of the ribbon ion beam 42 within the implantation chamber 50 can be created in a number of alternate ways. A more detailed description of a prior art ion implanter adapted for serial implantation of workpieces is disclosed in U.S. Pat. No. 4,975,586, issued to Ray. et al. on Dec. 4, 1990 and U.S. Pat. No. 4,761,559, issued to Myron on Aug. 2, 1988. The '586 and '599 patents are assigned to the assignee of the present invention and are incorporated herein in their respective entireties by reference. The structure of these patents can achieve the scan patterns contained in FIGS. 12A-12 D of the '462 prior art patent to Iwasawa et al. Prior to implantation, the workpiece support assembly 100 rotates the workpiece 24 from the horizontal orientation it assumes after transfer from the robot 53, to a vertical or near vertical position for implantation. If the workpiece 24 is vertical, that is, normal with respect to the ion beam 42, the implantation angle or angle of incidence is 0 degrees. It has been found that to minimize undesirable channeling effects, typically, a small but nonzero implantation angle is selected. As seen in FIG. 10, the workpiece can be rotated as indicated by the arrow 101 through different angles. One characteristic of the structure shown in the drawings is an ability to scan along a linear path (indicated by the arrows 103 in FIG. 10) so that a distance the ion beam 42 travels through the implantation chamber 50 before striking the workpiece is approximately the same for all regions of the workpiece. The support assembly 100 also optionally may include structure including a motor 105 (FIG. 11) which is able to rotate the workpiece through approximately 360 degrees about an axis 107 passing through the center of the workpiece normal to the wafer support. This allows the control electronics 26 to apply a specified amount of twist to the workpiece to re-orient the wafer. The structure for applying such a twist is described in greater detail below in conjunction with the FIG. 11 depiction. A single wafer is placed into the load lock 54 and the implantation chamber is pumped down to a desired vacuum. Within the implantation chamber a robot 53 grasps the workpiece 24, brings it within the implantation chamber 50 and places it on an electrostatic clamp or chuck 102 of the workpiece support structure 100. The electrostatic clamp 102 is energized to hold the workpiece 24 in place as it is re-oriented inside the chamber 50. Suitable electrostatic clamps are disclosed in U.S. Pat. No. 5,436,790, issued to Blake et al. on Jul. 25, 1995 and U.S. Pat. No. 5,444,597, issued to Blake et al. on Aug. 22, 1995, both of which are assigned to the assignee of the present invention. Both the '790 and '597 patents are incorporated herein in their respective entireties by reference. After ion implantation of the workpiece 24, the workpiece support structure 100 returns the workpiece 24 to a horizontal position and the electrostatic clamp 102 is de-energized to release the workpiece for removal by the in vacuum robot 53 back through the load lock 54. The workpiece support structure 100 is operated by the control electronics 26. (FIG. 5) The workpiece support structure 100 supports the workpiece 24 during implantation while providing both rotational (tilt and twist) and translational movement of the workpiece 24 with respect to the ribbon ion beam within the implantation chamber 22. By virtue of its rotational capability, the workpiece support structure 100 advantageously permits selection of a desired implantation angle or angle of incidence between the ion beam and the implantation surface of the workpiece. By virtue of its translational or linear movement capability, the workpiece support structure 100 permits the implantation surface of the workpiece 24 to be moved within a plane fixed with respect to the desired implantation angle during implantation thereby both maintaining the desired implantation angle and additionally maintaining a distance that the ribbon ion beam travels from its entry into the interior of the implantation chamber 50 to the region where it impacts the implantation surface of the workpiece. Additional details concerning the wafer support structure are contained in issued U.S. Pat. No. 6,740,894 which is assigned to Axcelis Technologies and is incorporated in its entirety herein by reference. During implantation of the workpiece 24, the workpiece support structure 100 moves the workpiece 24 in a direction transverse to the ribbon ion beam 42 such that an entire implantation surface is appropriately impacted and implanted with desired ions. As can be seen in the schematic depiction in FIG. 2, the ribbon ion beam 42 at a point of impact with the workpiece 24 has a maximum width W in the “x” direction (FIG. 2) which is greater than the diameter of the workpiece 24, thus, no translation of the workpiece in the “x” direction is required for full implantation of the workpiece. As can best be seen in FIGS. 2 and 3, the workpiece support structure 100 is affixed to a side wall 50a of the implantation chamber 50. The workpiece support structure 100 includes a rotation member 110 to control implant angle (tilt) and an integral translation member 150. The workpiece support structure rotation member 110 comprises a rotary turntable assembly affixed to the implantation chamber 50. In one preferred embodiment, the rotation member 110 includes a spindle bearing support housing 112 affixed to the implantation chamber and a rotary drive mechanism 120 rotatably affixed to the support housing 112. The support housing 112 is affixed to the implantation chamber and, preferably, to the implantation chamber side wall 50a and extends into the opening of the implantation chamber side wall. The rotation member 110 includes a spindle bearing system disposed in the support housing 112 and a hollow tilt axis shaft 123 rotatably supported by the spindle bearing systems. As can be seen in FIG. 2, the tilt axis shaft 123 extends into the implantation chamber interior region. The rotation member 110 also includes a ferrofluidic rotary vacuum seal system 130 also disposed between spaced apart sets of bearings 116a, 116b of the spindle bearing system. The rotary drive mechanism 120 includes a rotational servomotor 122 which, in response to control signals from the control electronics 26, precisely rotates the tilt axis shaft 123 and, thereby, rotates the workpiece 24 to the desired implantation angle. The angular position of the shaft 123 is monitored and reported to the control electronics 26 by a suitable rotary encoder 126. The servo-motor 122 is of conventional design and may, for example, be a direct drive servomotor or a gear-reduced servomotor. A central opening or bore 124 extends through the tilt axis shaft 123 to permit facilities, such as electrical wiring, to be routed to the translation member 150. The central bore 124 is at atmospheric pressure, unlike the evacuated implantation chamber interior region. The tilt axis shaft 123 is rotatably supported within the support housing 112 by means of the bearing assembly which includes two spaced apart bearings 116a, 116b, each of which comprises a conventional mechanical bearing assembly such as ball or roller bearings supported within a bearing cage and disposed between and inner and outer races. Alternately, the bearing assembly 116 may be a different type of bearing assembly such as, for example, a non-contact gas bearing assembly or other type of bearing assembly as would be recognized by one of skill in the art. A ferrofluidic seal of the magnetic fluid seal system 130 provides a hermetic seal under both static and dynamic conditions against gas, vapor and other contaminants from entering the implantation chamber 50. Further, since the sealing medium is a fluid, there is a low friction between the rotatable shaft 123 and the stationary portions of the seal system 130. Suitable hollow shaft cartridge mount vacuum feedthroughs and hollow shaft flange mount vacuum feedthroughs for the magnetic fluid seal system 130 are commercially available from Ferrotec (USA) Corporation, 40 Simon Street, Nashua, N.H. 03060-3075 (web site: http://www.fero.com/usa/sealing). A magnetic fluid seal system is disclosed in U.S. Pat. No. 4,293,137, issued Oct. 6, 1981 to Ezekiel. The '137 patent is incorporated in its entirety herein by reference. The workpiece support structure 100 further includes the translation or reciprocating member 150 which is disposed within an interior region of the implantation chamber. As can best be seen in FIG. 4, the translation member 150 includes a support frame 152 that attaches to the rotatable tilt axis shaft 123 and a carriage 154 mechanically coupled to the support frame 152 via a linear bearing assembly 160 for linear movement with respect to the support frame 152. The translation member 150 provides for linear translational movement of the workpiece 24 along a plane coincident with the selected implantation angle. As can best be seen in FIG. 2, the carriage 154 includes two flanges 155 that support the workpiece holder assembly 200. The workpiece holder assembly 200 includes a support arm 206, attached at one end to the carriage 154. At its opposite end, the support arm 206 supports a workpiece holder 208 of the workpiece holder assembly 200. The workpiece holder 208 supports the electrostatic clamp 102 which, in turn, supports the workpiece 24 for movement through the ribbon ion beam 42. Returning to FIG. 4, the carriage 154 is supported for linear movement with respect to the support frame 152 by means of the linear bearing assembly 160. The bearing assembly 160 preferably includes a pair of spaced apart, parallel linear rail supports 162, 164 affixed to an outward face 166 of the stationary support 152 and four bearing ways 168, 170, 172, 174 (FIG. 4) affixed to an inward face 176 of the carriage 154. A plurality of ball or roller bearings are disposed in each of the four bearing ways 168, 170, 172, 174. The bearings of the two spaced apart ways 168, 170 bear against and roll along the rail support 162 and the bearings of the two spaced apart ways 172, 174 bear against and roll along the rail support 164 to provide for linear movement of the carriage 154 with respect to the stationary support 152 and the implantation chamber 50. Linear motion of the carriage 154 with respect to the support frame 152 in FIGS. 3 and 4, is achieved by a linear motor assembly including a linear servomotor 180 disposed between an inwardly facing stepped portion 182 of the carriage 154 and the support frame 152. Additional details concerning the motor 190 are disclosed in the aforementioned '894 patent. A motor such as the motor 190 is used on prior art ion implanters and it is known to those skilled in the art the manner and size of signals that must be output from the control electronics to energize the motor to achieve both speed control and direction control for the so called slow scan movement. FIG. 11 depicts optional structure for selectively applying a twist to the wafer 24 on the chuck. In this depiction a shaft 220 mounted within bearings 221 is coupled to a pulley 222 which rotates in response to a rotational output from a shaft 224 of the motor 105 which rotates a pulley 226 and moves a belt 230. The motor can rotate the wafer 24 approximately one full rotation. The region of the belt 330 and pulleys is at atmosphere and the shaft 220 passes through a seal to the evacuated region inside the chamber 50. As the ions move from the source to the ion implantation chamber, they are scanned in a controlled manner by the scanning electrodes 30 under the control of the control electronics 26. This controlled deflection of ions produces a side to side scanning of ions emitting by the source to provide a thin beam of ions moving into the implantation chamber. Upon reaching the ion implantation chamber the ions strike a workpiece, typically a wafer on the workpiece support that is movably positioned within the implantation chamber. Simultaneous with the scanning provided by the electrodes 30, the control electronics moves the workpiece support assembly 200 up and down through the thin beam of ions to effect controlled beam processing of the workpiece. The control electronics 26 includes a first control output 26a coupled to the scanning electrodes 30 to limit an extent of side to side scanning of the ion beam to less than a maximum amount. Turning to FIG. 6, this aspect of the invention can be used to limit ion processing of the workpiece to a specified sub region, for example, the left half, quadrants A and C of the workpiece 24. A second control output 26b coupled to the drive motor 190 co-ordinates back and forth movement of the workpiece as side to side scanning of the beam is controlled to cause the ion beam to impact a specified sub region on the workpiece 24. As an example, FIG. 7 shows a sub region 210 in quadrant A implanted by the ion beam 42. This region of implant is achieved by limiting both scanning of the ions that make up the beam and mechanical slow scan movement. A similar implant can be achieved in quadrant with the exact same scan pattern (perhaps with different energy) by making use of the twist capability of the implanter. Alternately, without using the twist, a similar region in quadrant B can be implanted by adjusting the scan voltage while maintaining the slow scan movement. The system can implant different doses in each quadrant by implanting each half of the wafer (A+B and C+D) with different doses in the slow scan direction, scanning full width horizontally. By then twisting the workpiece wafer 90 degrees about an axis 107 normal to the center of the wafer, it can superimpose two more doses to the new top and bottom half (A+C and B+D). The accumulated dose in each quadrant is different for these combined implants. The limiting of the scan dimension (in geometric terms limiting the start and end points of the x scan direction) is implemented in conjunction with controlling process parameters to assure acceptable dose and uniformity of the implant within a specified sub-region of an implant area of the workpiece. An alternate approach for enabling multiple implants on a single wafer consists of implementing a selectable slow scan speed velocity profile. Slow scan in this instance refers to the motor drive movement of the support structure 100 up and down. The dose implanted monotonically increases from one end of the slow scan direction to the other according to selectable specified dose limits which form a part of the implant recipe. This is achieved by varying the scan speed of the motor 190. To increase the dose, the scan speed is slowed (allowing more time for a portion of the wafer to pass through the beam) and to decrease the dose the scan speed is increased. Additionally, one could hold the beam at the end of each fast scan a small time increment, which increment decreases as the wafer scans at a linear velocity in the slow scan direction. This presumes that the wafer does not move far between each fast scan sweep compared to the height of the beam even with the additional time increments. That is easily achieved in systems such as presently in use where the fast, horizontal scan frequency is about 1000 Hz while the mechanical, vertical scan frequency is of the order of 1 Hz. The dose would again increase monotonically or by another preprogrammed pattern based on the spacing or delays imposed between the generally horizontal fast scan sweeps. The continuously varied dose from the implants described above would allow one to select the dose that yields optimum device performance more accurately than can be done with a few discrete dose increments as is currently practiced in the art. To perform such evaluations a mask is used to create semiconductor devices at different regions of the workpiece. One could test performance of the completed device after doses of different strength are implanted onto the workpiece and just which dose gives the best or optimum performance. As a straightforward example, different doses could be implanted to each quadrant and fabricated devices in each quadrant then evaluated for their performance. Selection of Start and End Points for Slow and Fast Scan Directions. The system tunes the beam and generates uniform flux by modifying the scan waveform with “correction factors”. The waveform applied to the scan electrodes is truncated to consist of just the portion from center to left (or right) side of the scan pattern. Dose is monitored by one of two dose cups 230, 232 on an appropriate side. FIG. 9 shows the dose monitoring equipment located in the end station just in front of the wafer 24 and consisting of two small cups 230, 232 on each side of the scanned beam 42 to monitor overscan current during the implant. An energy shield 234 is inserted into the beam 42 from the side to block off a portion (top to bottom) of the beam to control the energy of the implant. Cup calibration is done for each of the cups 230, 232 on the left and right sides of the wafer independently while scanning the full width instead of summing the amplitudes as is presently done on prior art implanters. The flux measured by one cup would roughly double, since the scanned area is reduced by half, so the implant time would be reduced compared to implanting the whole wafer. Dose calculation would follow the normal routine based on the flux measured by a single dose cup. The control electronics software has a field in the recipe to specify an implant on just the left or just the right side of the wafer. Slow Scan Direction The motor 190 causes the workpiece to scan from one end of the scan until the beam reaches the center of the wafer, and then reverses direction. The region of non-uniform dose would depend on beam height and distance required to stop scanning in one direction and energize the motor 190 to move the workpiece at the desired scan speed in the opposite direction. Both dose cups are used and the implant takes the same number of slow scans as required for the whole wafer, at the same nominal slow scan velocity. Software executing in the programmable controller of the control electronics 26 includes a field in the recipe to specify an implant into just the top or just the bottom half of the wafer. Selectable Dose Profile Use Fast Scanner to Control Profile: If the nominal fast scan frequency is 1000 Hz, then each stripe across the wafer is spaced at 500 usec intervals. A delay of 500 microseconds at each end of the scan would reduce the dose by a factor of two if the slow scan velocity is unchanged. This would still allow for closely spaced scans so there is not a risk of striping. One exemplary recipe operates open loop at a constant Y-scan velocity as the delay at each end of scan increases from 0 to 500 microseconds linearly across the wafer. The dose then changes linearly from the nominal dose to one half the nominal from top to bottom. Non-linear dose distribution functions are also produced. Use Slow Scan Velocity to Control Profile: The process of implant setup calculates a nominal slow scan velocity and the total number of scans required to achieve the specified dose. Software can be used to vary the speed of the motor 190 to set a scan velocity at the middle of the wafer to a nominal value and let the values at the top and bottom be the nominal value +X % at the top and −X % at the bottom. This would give a linear dose variation of 2X % across the wafer. Again the implant could run open loop with this slow scan velocity profile. Alternatively, one could specify a dose profile in the recipe and the mechanical or slow scan velocity changes as a function of Y-position to achieve that dose profile while using the dose cup current as a closed loop control. Chaining Multiple Implants The implants discussed above allow various parts of the wafer to receive a different dose, implant angle, energy, or species. In the case where dose or angle is the only difference between scans, it is efficient to chain the recipes so that the various segments of the wafer can be implanted without removing the wafer from the wafer chuck 102. For a species or energy change it may not be efficient to retune the beam if the same series of implants are done on many wafers. Energy changes can be implemented by changing a position of an energy shield 234 and species changes are made by substitution of different source materials. In these, instances it may be more efficient to process the whole batch of wafers and then change the species or energy of the implant. FIG. 8 is a flowchart of a method of for controlling workpiece implantation in accordance with the exemplary embodiment of the invention. The method is initiated 250 by control electronics 26, typically in the form of a programmable controller getting a recipe or recipes for implanting one or more workpieces. The ion beam is set up or calibrated 260 to create ions of a specified current and energy for movement along an initial trajectory. The flux density across the ribbon is made uniform by an iterative process of monitoring beam dose at the plane of the wafer using a moving faraday profiler 231 and modifying the scan waveform electronics with “correction factors.” The two faraday cups 230, 232 are used to monitor beam current during the implant. The recipes will indicate if normal (uniform whole wafer) implanting is performed or if multiple regions are implanted differently. At a decision 270 the method determines if normal processing is performed and if so that processing 280 occurs and the method ends 360. If different regions are implanted with different doses a decision is made 290 whether the implantation will be variable or uniform. If variable, a scan profile of the back and forth workpiece movment is set up 300 and the side to side scanning is set 310 to full range scanning. Finally the implantation is performed 320. If uniform scanning is chosen the control electronics sets 330 the tilt, twist and scan ranges in the x and y directions for each of the multiple regions. The implantation 340 then occurs and a determination is made 350 whether additional implants into a next subsequent of the multiple implants are to be made. If so, the implant parameters are adjusted, and if not the process ends 360. The present invention has been described with a degree of particularity. It is the intent, however, that the invention include all modifications and alterations from the disclosed design falling within the spirit or scope of the appended claims.
052873951	description	DETAILED DESCRIPTION OF THE INVENTION Depicted in FIG. 1a is a conventional diffracting single crystal 12 which has been symmetrically cut so that diffraction planes 22a are parallel to crystal surface 20a. Assuming that at angle .theta..sub.B the Bragg condition is satisfied, monochromatic x-ray beam 10 is symmetrically diffracted by crystallographic planes 22a. Assuming that beam 10 has a circular footprint in the plane normal to the direction of beam 10, then the footprint 24a of beam 10 on surface 20a will be oval. Because the incident beam 10 and the diffracted beam 10 make the same angle with respect to the surface normal, diffraction is symmetric. Crystal 14 of FIG. 1b has been asymmetrically cut so that when compared to the conventional crystal the surface 20b is rotated about an axis which is normal to the scattering plane 11 which contains the incident beam 10 and diffracted beam 10. Again assuming that at angle .theta..sub.B the Bragg condition is satisfied, beam 10 is diffracted by planes 22b. Footprint 24b of beam 10 on surface 20b will be oval, and more elongated in the direction of beam 10 than footprint 24a. Because the incident beam 10 and the diffracted beam make unequal angles with respect to the surface normal, diffraction is asymmetric. FIG. 1c exemplifies the principles of the present invention. Crystal 16 has been cut so that the normal to the diffraction planes 22c makes an angle close to but less than 90 degrees with the normal to crystal surface 20c. Again assuming that at angle .theta..sub.B the Bragg condition is satisfied, beam 10 is diffracted by planes 22c. Footprint 24c of beam 10 on surface 20c is spread both in the direction of the beam and horizontally. FIGS. 2a, 2b, and 2c are schematic drawings depicting beams which are incident upon and diffracted by the Bragg diffraction planes of the crystals in FIGS. 1a, 1b, and 1c, respectively. In each of FIGS. 2a, 2b and 2c, beam 10 is incident upon the diffraction planes at angle .theta..sub.B to diffract photons of the desired energy. In the symmetrically cut crystal 12 of FIG. 2a, crystal surface 20a is parallel to diffraction planes 22a. In asymmetrically cut crystal 14 of FIG. 2b, crystal surface 20b is rotated about an axis which is normal to the scattering plane 11 shown in FIG. 1b. In the symmetrically cut crystal 16 of FIG. 2c, crystal surface 20c has been rotated so that the normal to the diffraction planes 22c makes an angle close to but less than 90 degrees with the normal to crystal surface 20c. The extent to which the horizontal dimension of the footprint is increased by use of the inclined crystal can be calculated. As shown in FIG. 3, beam 10 is incident at an angle .theta..sub.B on the surface of the inclined crystal represented by the dark shade on plane 22c. The crystallographic planes of interest are at an angle .beta. with respect to the surface of the crystal, and are parallel to the plane 20c, as shown. (In the crystal of FIG. 1a, planes 20c and 22c coincide and .beta.=0.) Assume that at normal incidence, beam 10 has a rectangular footprint, and the height (in the vertical) and width (in the horizontal) of the footprint are v and h unit lengths respectively. If the beam is incident at a Bragg angle .theta..sub.B, the beam footprint on a conventional crystal (shown by the lightly shaded area in the horizontal plane 20c in FIG. 3) is increased by a factor of 1/sin .theta..sub.B. This is due to the spread in the vertical dimension of the beam. The beam footprint on the surface of the inclined plane (represented in FIG. 3 by the plane 22c) making an angle .beta. with plane 20c is a parallelogram. The height of the beam footprint is identical to that of the conventional crystal and equal to v/sin .theta..sub.B. Referring now to FIG. 3, the width of the footprint is evaluated as follows: ##EQU1## The area of the inclined footprint is then EQU Area=(AG) (AE) sin .gamma.=vh/(sin .theta..sub.B cos .beta.) (4) Therefore, in comparison with the conventional crystal, area of the beam footprint is increased by a factor of 1/cos .beta., or by a factor of 1/sin .theta..sub.B cos .beta. as compared with the normal incidence footprint. FIG. 4 plots magnification of an incident beam footprint on an inclined crystal as compared to the incident beam footprint on a conventional crystal as a function of the inclination angle .beta.. It is seen, for example, that for an inclination angle of 85 degrees the area of the footprint is increased by a factor of 10 compared to the area of the normal incident footprint on a conventional crystal. Thus the incident flux is reduced by a factor of 10. The inclination angle .beta. may have any value in the range 90.degree.>.beta..gtoreq.0.degree.. As one gets closer to 90.degree., the footprint of the beam will get larger and larger. The monochromator size will then be large. The size and quality of available single crystal blocks are thus two determinant factors in choosing the inclination angle .beta.. However, since the powerful x-ray beams generated by undulators have very small sizes, the crystal size necessary to intercept the beam is reasonable. Furthermore, slits can be used to let only the central part of the x-ray beam hit the crystal. There is an additional consideration with regard to the inclination angle. For a given material, in this case a single crystal, the angle that an x-ray beam makes with the surface must remain above some critical angle .alpha..sub.c to avoid total reflection, which is calculated as follows. In the inclined geometry, the angle that an incident beam makes with the surface of a single crystal monochromator is given by EQU sin .phi.=sin .theta..sub.B cos .beta. (6) where .theta..sub.B is the Bragg angle and .beta. is the inclination angle. The angle .phi. must remain larger than critical angle .alpha..sub.c to avoid total reflection. The critical angle for total reflection (see W. B. Yun and J. M. Bloch, "X-ray near total external fluorescence method: Experimental and analysis," J. Appl. Phys. 68(4), 1990) is approximately ##EQU2## where (1-.delta.) is the real part of the index of refraction of the material, and ##EQU3## where r.sub.e is the classical electron radius, C is the number of molecules per unit volume, F is the number of electrons per molecule, and .lambda. is the incident x-ray wavelength. From Equations 6-8, the condition for total reflection is EQU sin .phi..ltoreq.sin .alpha..sub.c (9) where ##EQU4## If the monochromator is to be used in the Bragg regime, then the Bragg equation given by EQU .lambda.=2d sin .theta..sub.B (10) must also apply. In Eqn. 10, d is the diffracting plane lattice spacing, .lambda. is the wavelength and .theta..sub.B is the Bragg angle. Substituting for Sin .theta..sub.B from Eqn. 10 into Eqns. 6, we have: ##EQU5## where .beta..sub.c is defined as the critical inclination angle. A crystal cut at smaller inclination angles than .beta..sub.c avoids total reflection at all wavelengths. Substituting for small angles .alpha..sub.c from Eqns. 7-8 in Eqn. 11, one gets ##EQU6## For Si(111) , Equation 12 gives .beta..sub.c =89.1.degree.. For Ge(111) and diamond (400), the critical inclination angles are 88.7.degree. and 89.71.degree. respectively. FIG. 5 is a schematic drawing of a double crystal monochromator of the present invention. In first crystal 30, plane 32 is inclined at angle .beta. to surface 34. Beam 100 is incident upon crystal 30, forming footprint 36, and is diffracted from planes parallel to plane 32. Cooling channels 38 provide means for cooling crystal 30. A second crystal 40 identical to crystal 30 positioned in parallel with crystal 30 will recollect beam 10, and diffract it in a direction parallel to the incident beam 100. An additional advantage of the inclined crystal of the present invention is that thermal distortions are not as detrimental as in the case of conventional single-crystal monochromators. Because of the orientation of the diffraction planes with respect to the surface of the crystal, thermal distortion of the surface contributes only partially to the misorientation and thus the slope errors of the diffraction planes. In first crystal 30 of FIG. 5, a pure bending of the crystal along its horizontal dimension (i.e., width of the crystal 34) will not affect the Bragg angle .theta..sub.B. For the bending along the length of the crystal, consider the case of .beta. approaching 90 degrees. There is only a minor change in the Bragg angle .theta..sub.B as a result of this bend (which can be thought of as a major component of the thermal distortion in the crystal) because to a first approximate the crystal diffraction planes remain almost parallel. Now, as the inclination angle is decreased from 90 degrees to 0 degrees (as in conventional monochromators), the effect of such a bend will become progressively more pronounced. From this point of view the conventional monochromator is the worst choice. An additional advantage of the invention is that the spreading of the beam over a large surface area makes a several kill cryogenically cooled monochromator system feasible and more practical by (a) requiring far fewer vertical layers of cooling channels to provide the needed surface area for heat removal, thereby reducing the complexity of the design, (b) making the critical heat flux problem more manageable, (c) providing a more uniform temperature field on the surface of the crystal and thus more efficient cooling, and (d) producing a lower overall temperature in the system leading to better cooling efficiency, reduced thermal strains, and more managable thermal cycling of the system. FIG. 6 is a schematic drawing depicting an alternate embodiment of an inclined crystal of the present invention. Crystal 40 is symmetrically cut so that diffraction planes 42 are parallel to each of many crystal surfaces 44. Surfaces 44 are cooled by cooling channels 48. Beam 10 is simultaneously incident upon surfaces 44, and footprint 46 is spread over each of the surfaces 44. Cooling through channels 48 is enhanced because of the break up of the powerful incident power or beam onto smaller, spatially separated footprints when compared to the conventional crystal. FIG. 7 is a graph depicting test results using the present invention. Experiments were conducted at CHESS (Cornell High Energy Synchrotion Source) with the undulator placed in the Cornell electron storage ring (CSER). With CSER in dedicated operation at 5.433 GeV, the undulator first harmonic occurred at 5.14 keV with a gap of 1.7 cm. The first crystal in a double-crystal arrangement was placed 18 m from the undulator source. The dimensions of the incident beam in a plane 18 m from the source and transverse to direction of the beam in terms of the horizontal and vertical FWHM (full width and half maximum) are 4.6 mm and 2.0 mm respectively. Calorimetric measurement of the incident beam at 49.4 mA ring current showed a value of 195 W for total power. It is estimated that the peak normal incident heat flux be about 50 W/mm.sup.2. Inclined crystal data in FIG. 7 was derived using the (111) reflection from a (111) silicon crystal. The value of .beta. for this case is 70.529 degrees. The crystal was symmetrically cut and measurements for both the inclined and conventional geometry were made with the same crystals (because there is a set of (111) planes at 70.529.degree. with respect to the surface (111) planes). As shown in FIG. 7, the intensity of the beam diffracted from the inclined crystal measured in arbitrary units continued to increase even as currents approached 100 mA, indicating that the effects of increasing heat generation were negligible. (For a detailed analytical comparison of the performance of an inclined and a conventional monochromator, see Ali M. Khounsary, "A novel monochromater for high heat load synchrotron radiation," Rev. Sci. Instrum., Vol. 63, No. 1, January 1992, which is incorporated herein by reference.) The foregoing description of a preferred embodiment of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments described explain the principles of the invention and practical applications and should enable others skilled in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto.
047537744	description	DETAILED DESCRIPTION OF THE INVENTION In the following description, like reference characters designate like or corresponding parts throughout the several views of the drawings. Also in the following description, it is to be understood that such terms as "forward", "rearward", "left", "right", "upwardly", "downwardly" and the like are words of convenience and are not to be construed as limiting terms. In General Referring now to the drawings, and particularly to FIGS. 1 to 4, there is shown a nuclear fuel assembly, generally designated 10 for a boiling water nuclear power reactor (BWR), in which the improvement of the present invention is incorporated. The fuel assembly 10 includes an elongated tubular outer flow channel member 12 (hereinafter outer channel member 12) that extends along substantially the entire length of the fuel assembly 10 and interconnects an upper support fixture or top nozzle 14 with a lower base or bottom nozzle 16. The bottom nozzle 16 serves as an inlet for coolant flow into the outer channel member 12 of the fuel assembly 10, and includes a plurality of legs 18 for guiding the bottom nozzle 16 and the fuel assembly 10 into a reactor core support plate (not shown) or into fuel storage racks, for example in a spent fuel pool. The outer channel member 12 (FIG. 4) is generally of rectangular cross-section, is made up of four interconnected vertical walls 20 each being displaced about ninety degrees one from the next. A plurality of inwardly facing structural ribs 22 are formed in the walls 20 of the outer channel member 12. The ribs 22 are formed in a spaced-apart relationship in the inner surface of each wall 20 of the outer channel member 12. Above the upper ends of the structural ribs 22, a plurality of upwardly-extending attachment studs 24 (FIG. 2) are fixed on the walls 20 of the outer channel member 12 and are used to interconnect the top nozzle 14 to the outer channel member 12. Fuel rods 40 are supported in an exemplary 8.times.8 array in a bundle within the outer channel member 12. Upper and lower tie plates 42 and 44, secured in the outer channel member 12, support opposite ends of the fuel rods. A plurality of grids 48 secure the rods laterally in a known manner. For improving neutron moderation and economy, a hollow water cross 26, as seen in FIGS. 1, 2, 4 and 5, extends axially through the outer channel member 12 so as to provide an open inner channel 28 for subcooled moderator flow through the fuel assembly 10 and to divide the fuel assembly into four separate, elongated compartments 30. The water cross 26 has a plurality of four radial panels 32 composed by a plurality of four elongated, generally L-shaped metal angles or sheet members 34 that extend generally along the length of the outer channel member 12. The sheet members 34 of each panel 32 are interconnected and spaced apart by a series of elements in the form of dimples 36 (FIGS. 4 and 5) as shown. Opposed pairs of contacting dimples 36 are connected together such as by welding to insure that the spacing between confronting sheet members 34 forming the panels 32 of the central water cross 26 is accurately maintained. Upper and lower closures 54 and 52 (FIG. 5) seal or close the respective upper and lower ends 38 and 39 of the water cross 26. Outlets 66 are provided in the upper closure 54. The hollow water cross 26 is mounted to the angularly displaced walls 20 of the outer channel member 12. Preferably, the outer elongated, lateral ends of the panels 32 of the water cross 26 are connected such as by welding to the structural ribs 22 along the lengths thereof in order to securely retain the water cross 26 in its desired central position within the fuel assembly 10. Further, inner surfaces of the sheet members 34 together with the outer ends thereof define the inner central cruciform channel 28 which extends the axial length of the hollow water cross 26. The bundle of fuel rods 40 which, in the illustrated embodiment, number sixty-four in an 8.times.8 array, are separated by the water cross 26 into the four compartments 30, each housing a fuel mini-bundle or subassembly 46. The fuel rods 40 of each mini-bundle, such being sixteen in number in a 4.times.4 array, extend in laterally spaced-apart relationship between upper and lower tie plates 42 and 44. The fuel rods 40 in each mini-bundle are connected to the upper and lower tie plates 42, 44 and together therewith comprise a separate fuel rod subassembly 46 within each of the compartments 30 of the outer channel member 12. The grids 48, axially spaced along the fuel rods 40 of each fuel rod subassembly 46, maintain the fuel rods 40 in laterally spaced relationship. The lower and upper tie plates 44, 42 of the respective fuel rod subassemblies 46 have flow openings 50 defined therethrough for allowing the low of the coolant/moderator fluid into and from each separate fuel rod subassembly 46. Also, coolant flow paths provide flow communication between the fuel rods subassemblies 46 in the respective separate compartments 30 of the fuel assembly 10 through a plurality of openings 53 formed between each of the structural ribs 22 along the lengths thereof. Coolant flow through the openings 53 serves to equalize the hydraulic pressure between the four separate compartments 30, thereby minimizing the possibility of thermal hydrodynamic instability between the separate fuel rod subassemblies 46. Openings 68 in the sheet members 34 may be provided to supply subcooled moderator fluid to the central portion of each fuel rod subassembly 46. Cross Flow Inlet Means at Fuel Bundle Entrance Referring now to FIGS. 1, 4 and 5, there is seen the feature incorporated in the BWR fuel assembly 10 which provides an inlet to the water cross 26 and allows cross flow of fluid near the lower ends of the respective fuel rod mini-bundles of the separate fuel rod subassemblies 46 and in such manner minimizes maldistribution of flow between the mini-bundles. Referring again to FIG. 5, the water cross 26 shown in perspective includes the aforementioned respective bottom and top closure means 52 and 54. The improvement comprises side entry cross flow inlet means 58 in the form of holes in the water cross sheet members 34 at a lower end 38 thereof. The top closure 54 at the upper end 39 of the water cross 26 has its outlet holes 66 sized so as to limit the outlet of the water cross 26 to an open area less than the open area of the cross flow inlet means 58. In such manner, a positive pressure gradient is maintained in the subcooled moderator flow through the water cross inner flow channel 58 relative to the coolant/moderator flow through the fuel rod subassemblies 46 in outer flow channel 12. Specifically, the outlet holes 66 in the top closure means 54 are each of a predetermined diameter size which is less than the predetermined diameter size of each of the holes forming cross flow inlet means 58 in the sheet members 34. Such relationship distributes the hydraulic losses such that greater loss is experienced at the outlet than at the inlet of the water cross 26. Also, the arrangement reduces the static pressure loads at the inlet and the risk of failure of dimple welds which interconnect the pairs of sheet members 34 of the water cross 26. The holes 58 are preferably located in opposition to each other in confronting sheet members 34 and are generally axially aligned as shown. The holes 58 are preferably within a few centimeters above the respective lower ends of the mini-bundles 46 and the lower tie plate 44. In the current conventional design, inlet pressure drives the coolant/moderator into the water cross 26 through openings below the lower tie plate 44, and coolant/moderator enters the mini-bundle through openings the lower tie plate 44. In the proposed design, the inlet pressure drives coolant/moderator into the mini-bundle through resized lower tie plate holes 50, and coolant/moderator is driven into the water cross 26 through the side entry cross flow inlet means 58 therein above lower tie plate 44. The driving force for coolant into the water cross 26 in the current design is the pressure gradient or difference in inlet pressure P1 less the resulting water cross pressure P3 (or P1-P3). In the invention, the driving force is the difference between the water cross pressure P3 and the mini-bundle pressure P2 (or P2-P3), which is less than (P1-P3). In order to achieve a certain selected flow W.sub.C to the water cross for a given pressure drop .DELTA.P the following expression is used: EQU .DELTA.P=KW.sub.C.sup.2 where K denotes the effective loss coefficient. If .DELTA.P is to be reduced for a selected W.sub.C, then K must necessarily be decreased. In the present invention, the pressure gradient P2-P3 driving the coolant/moderator into the water cross is less than the pressure gradient (P1-P3) in the current design. Therefore, the effective loss coefficient at the inlet to the water cross can be decreased. This is accomplished by increasing the flow area at the water cross inlet. Thus, in FIG. 6, the reduced loss coefficient allows the operation in the shallow part of the curve at S.sub.2. In the proposed design, the lower tie plate loss coefficient is also decreased in order to achieve the same pressure drop P1-P2 between the inlet and mini-bundle. This occurs because the total flow W.sub.T, although the same in both designs, is rerouted through the mini-bundles in the proposed design by closure of the inlets to the water cross below the lower tie plates. The low to the mini-bundles is thus increased by about 10%, by upwardly resizing the holes in the lower tie plates to produce a lower loss coefficient according to the following expression: EQU K'W.sub.T.sup.2 =K(W.sub.T -W.sub.C).sup.2 where K' is the new loss coefficient for the lower tie plate, W.sub.T is total flow through the tie plates, and K is the original loss coefficient for the lower tie plate. Hole size determination may be made by relatively straightforward and simple experiments based on known parametric data. The important feature of the present invention is to determine the apppropriate loss coefficients which achieve improved results. Thereafter, hole sizing is implemented to achieve the desired loss coefficients. The proposed improvement provides for better control and lesser uncertainty in the amount of flow entering the water cross 26. This has direct bearing on the amount of voids formed and consequent degradation in nuclear performance. Again, crud buildup effects are also subdued. The opposed axial alignment of holes 58 provides for direct communication between the minibundles and helps minimize flow maldistribution, consequently also minimizing any degradation in bundle CHF performance which might result from the flow maldistribution. About 4% to 7% improvement in bundle CHF margin can be expected from total elimination of inlet flow maldistribution. Reducing the possibility of generating voids in the water cross also improves the transient thermal hydraulic performance, especially the hydrodynamic stability of the assembly. It is felt that the proposed modification should prove largely beneficial from the standpoint of structural characteristics. For example, the proposed side entry cross flow inlet means reduces the pressure gradient across each of the four water cross panels. This pressure gradient reduction consequently improves the fatigue-related performance of the fuel bundles 10 and water cross structure 26. This disclosure has focused on an invention to minimize water cross flow rate uncertainties and related undesirable effects. The proposed design modification involves closing off the water cross inlet and diverting liquid into the water cross from above the minibundle lower tie plates via holes or slots machined into the water cross walls. This simple modification miminizes uncertainties in the amount of flow entering the water cross and the flow maldistribution between the minibundles. The modification also provides direct benefits by reducing any crud buildup-related penalties. The present invention also has some important safety implications in the context of a so-called loss of coolant accident (LOCA). The repositioning of the water cross entry inlet flow holes 58 to the side of the water cross panels 34 and above the lower tie plates 44 is expected to provide benefits during a loss of coolant accident. In the early stages of such an accident, coolant is sprayed into the top of each fuel assembly 10 to provide cooling heat transfer. The coolant spray may be unable to penetrate into the assembly, however, because it is resisted by the steam produced from the residual heat in the fuel. This condition is referred to as being counter-current flow limited (CCFL). Later in the accident, water is injected from the safety injection systems (not shown) at the bottom of the fuel assemblies in the same manner that coolant normally enters the fuel bundles 10. This is called the reflood portion of the accident. The holes 58 in the water cross 26 situated above the lower tie plates 44 provide benefits during both the CCFL and reflood portions of the accident. During the CCFL portion, spray coolant can travel down through the water cross 26, exit through the holes 58 and flow up through the fuel mini-bundles. This helps to more quickly quench the steam and allow the coolant spray, restricted to the top of the bundle, to penetrate throughout the bundle. With the entry holes 58 located above the lower tie plates 44, the downwardly directed water cross flow does not have to overcome the resistance of the lower tie plate 44 as in the current design where the watercross flow holes are located below the lower tie plate. Therefore, more flow is available from the water cross 26 to travel up the fuel mini-bundles and help quench the steam. The CCFL condition is therefore more quickly overcome. In the current design, with the flow holes located below the lower tie plate, during the reflood portion of the accident, a certain fraction of the injected water is diverted to the water cross 26. Consequently, that flow is not available to provide heat transfer cooling of the fuel rods. In the proposed invention, the holes 58 are moved instead to the side of the water cross sheet members 34 and above the lower tie plates 44. With this design, all of the injected water flows up through the lower tie plates 44 and most of that injected water continues to travel up through the fuel mini-bundles to provide cooling. Only after sufficient coolant pressure is re-established within the fuel mini-bundles does some of the injected water get diverted up through the water cross instead of up through the mini-bundles. Thus, the invention results in a design which has safety advantages not available with prior arrangements. The pressure drop across the tie plate of the improved fuel bundle without water cross inlets shall be adjusted to be less than the pressure drop across a conventional tie plate having inlets to the water cross because the tie plate orifice losses associated with the water cross inlets have been eliminated. Thus, in the present invention the loss coefficient shown in FIG. 6 is reduced from S.sub.1 to S.sub.2. As the slope of the curve in FIG. 6 becomes shallow in the S.sub.2 portion, uncertainties in the inlet area result in lower uncertainties in the loss coefficient. Therefore, the embodiment of the present invention is less sensitive to crud buildup and the flow to the water cross is less uncertain. It is thought that the invention and many of its attendant advantages will be understood from the foregoing description, and it will be apparent that various changes may be made in the form, construction and arrangement thereof without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the form hereinbefore described being merely a preferred or exemplary embodiment thereof.
056235267	abstract	In order to support a shroud against bending, shear, stress and torsion, straps which are preferably formed of the same material as the shroud, are placed in strategic positions with respect to cracks or the like type of weaknesses which have been detected, and fastened in place using a suitable fastening technique. In the preferred embodiments of the invention holes a formed using an EDM technique and bolt units which have an expanding portion are inserted into the holes, torqued and expanded in a manner which fastens the strap to the shroud. Welding and the like type of fastening techniques are not excluded and may used alternatively or in combination with the bolting technique as required.
	summary
	summary
052895092	summary	BACKGROUND OF THE INVENTION The present invention relates to an improved comb-line antenna structure that may be used to launch magnetosonic waves into a plasma for plasma heating or current drive in a plasma device, e.g., a tokamak. More particularly, the invention relates to an improved comb-line antenna structure suitable for use in a tokamak that, in one embodiment, eliminates the need for discrete loading capacitors at the end of each current strap used in the comb-line antenna, and provides Faraday shielding between the antenna and plasma in a way compatible with a traveling wave. Tokamaks are devices that are used in connection with the study and generation of thermonuclear fusion energy. Fusion is the energy source of the sun and other stars. While science has not yet advanced sufficiently far to allow fusion to be used as a practical energy source, scientists and engineers, working at laboratories around the world, are making great strides relative to fusion research and to the engineering development of fusion for electrical power and other applications. Advantageously, fusion fuel is in abundant supply, and the generation of fusion energy provides a safe and clean energy source. In generating fusion energy, the atoms of two or more fuels, typically deuterium (.sup.2 H) and tritium (.sup.3 H), heavy hydrogen isotopes, are exposed to extremely high temperatures. Such high temperatures separate the positively charged nuclei of the hydrogen isotopes from their normally tightly bound negatively charged electrons, forming a plasma. (A plasma is a hot ionized gas.) When this separation occurs, the neutrons and protons of the nuclei recombine to form a heavier element, such as .sup.4 He, and a neutron or other small nuclear particle. Energy from this reaction is released as kinetic energy of the fast moving reaction products, and it can be converted to heat. The heat thus created provides the high temperature needed to sustain the fusion reaction, and portions thereof can be extracted and used as a useful energy source, e.g., to generate electricity. The conditions for the fusion reaction are very difficult to achieve. For example, in order to kindle a deuterium-tritium fusion fire, the temperature of the fuel must be heated to over 50,000,000.degree. C. Moreover, to sustain the fusion fire, i.e., to keep the fusion reaction going, it is necessary to confine the normally chaotic mass of fast moving, superheated nuclei (the plasma) long enough for the fuel to react and produce energy beyond that necessary to sustain the temperature. To produce enough fusion reactions to make the process worthwhile, the heat losses from the fuel must be low enough so that the fuel can sustain a temperature of around 150,000,000.degree. C. Once such a self-sustaining reaction is achieved, it is possible to use the heat thus produced to generate electricity, or for other purposes. Achieving such high temperatures requires supplying energy to the fuel and raising its temperature to a level where the internal fusion reactions can provide further heating. Various techniques are currently used to accomplish such heating, e.g., heating with an internal electric current, heating by various waves, and/or heating by the injection of energetic neutralized hydrogen atoms ("neutral beam injection"). The present invention relates to a particular type of antenna structure, referred to as a "comb-line antenna" structure, that may be used to launch a particular type of fast electromagnetic wave, referred to as a "magnetosonic wave", into the forming plasma for plasma heating and current drive. Unlike the sun and stars, where the massive plasma ball is confined by gravity, fusion reactors require some type of container for holding the 150,000,000.degree. C. plasma fireball in a way that prevents it from touching the container walls. (Plasma, which has a density approximately 100,000 times lower than atmospheric pressure, is a mere puff of gas that would quickly cool if it touched the container walls.) Fortunately, because plasma is an ionized gas, it can be confined with a magnetic field. That is, the otherwise random motion of the charged particles that are found within plasma may be converted to an orderly form of motion that follows the magnetic field lines of an applied magnetic field. Thus, various types of "magnetic bottles" have been developed in the art to create the appropriate magnetic field lines to confine the plasma to a desired volume. One of the most highly developed magnetic bottles is a toroidal bottle known as the "tokamak". Tokamaks were first developed during the 1960s in the then-existing USSR, and have subsequently been adopted as the leading magnetic confinement device. A tokamak includes both external toroidal-field coils and poloidal-field coils that generate magnetic fields, as well as means for generating a toroidal electrical current that flows through the plasma itself. The magnetic fields created by such toroidal- and poloidal-field coil currents, as well as by the plasma electric current, all combine to confine the plasma to a general toroidal shape that encircles a major axis of the tokamak. The poloidal-field coils are also used to magnetically shape the general cross section of the plasma. Tokamaks are well documented in the literature. See, e.g., Artsimovich, L. A., Nuclear Fusion, Vol. 12, pp. 215 et seq. (1972); and Furth, H. P., Nuclear Fusion, Vol. 15, pp. 487 et seq. (1975). The fast magnetosonic wave is a preferred wave for noninductive current drive in tokamaks containing high temperature plasmas. See, Fisch et al., Phys. Fluids, Vol. 24, p. 27 (1981). Note, the term "magnetosonic" wave is used herein and in the art to describe a "fast wave" or a compressional "Alfen wave." The launching structure used to launch such a magnetosonic wave into the plasma has typically consisted of several (typically four) poloidal straps that are individually fed through external matching networks and phase shifters to an appropriate power source (a high power rf generator). Disadvantageously, such a launching configuration does not present a matched load to the generator when the plasma position and edge density vary. Further, the mutual coupling between the current straps causes unbalanced loading of the straps. Such unbalanced loading greatly complicates the phasing and matching of the structure to the generator. Hence, what is needed is a launching structure for use in a tokamak (or similar plasma-confining device) that presents a matched load to the generator even though the plasma position and edge density of the plasma may vary, and wherein any mutual coupling between the current straps may be used to an advantage rather than a disadvantage. A "comb-line" structure is a structure that includes an array of antenna loops, or equivalent current straps, where only one of such loops or straps is driven with an input signal, while the others are coupled through mutual inductance. Comb-line structures have long been used as band-pass filters having a narrow or moderate bandwidth. See, e.g., Matthaei, George L., "Comb-line Band-Pass Filters of Narrow or Moderate Bandwidth:, Microwave Journal, pp. 82-91 (August 1963). A few years ago, the comb-line structure was identified as a possible launching structure for launching the ion cyclotron range of frequencies (ICRF) into the plasma of a fusion tokamak for plasma heating and current drive. See, Chiu et al., "Study of the Slow-Wave Structure as an ICRF Launcher", Nuclear Fusion, Vol. 24, No. 6, p. 717-723 (1984). The comb-line structure is a good candidate for current drive because it can easily be made to produce a traveling wave spectrum, and the principle of its operation requires that it be only weakly coupled to the plasma. Weak coupling is plausible for reactor applications because it allows the structure to be recessed from the plasma. Despite the potential benefits to be derived from using a comb-line structure to launch magnetosonic waves into a plasma, the comb-line structure has not heretofore been used for such application. Such non-use can be attributed, in large part, to practical considerations associated with the dimensions of the various elements of the comb-line structure. For example, discrete capacitors have heretofore been used with each current strap in order to allow each current strap, which must function as a resonant circuit, to be of a manageable length. The physical size of such capacitors, while having a capacitance value of only tens of picofarads for most frequencies, must nonetheless be quite large so that the capacitors can hold off the extremely high voltages in the plasma environment. Such large physical size restricts the spacing of the current straps. Hence, what is needed is either a physically smaller capacitor that can hold off the extremely high voltages in the plasma environment, or a comb-line antenna structure that eliminates the need for discrete capacitors. An additional problem associated with using a comb-line structure as a launching structure with a plasma device, such as a tokamak, is that of providing shielding of the plasma from the electrostatic fields emanating from the current straps. An electrostatic field is ever present around the current carrying straps of a comb-line structure. Such electrostatic field must be confined to the region near the current straps in order to avoid its penetration into the plasma, which penetration can cause an influx of impurities into the plasma. The appropriate magnetic fields associated with the current straps, on the other hand, need to encircle the adjoining straps so that the desired mutual coupling between the straps can occur, and so that the requisite magnetosonic wave can be launched into the plasma. Thus, there is a need when using a comb-line structure as a magnetosonic launcher for establishing an effective electrostatic shield between the current straps and the plasma that blocks electrostatic fields, yet passes traveling magnetic fields. SUMMARY OF THE INVENTION The present invention advantageously addresses the above and other needs by utilizing a comb-line structure that includes a multiplicity of parallel current straps through which an appropriate rf electrical current passes in order to launch a desired magnetosonic wave into an adjacent plasma mass. The current straps are mounted within a conductive, shallow, open box that faces the plasma mass. The current straps are inductively coupled, thereby requiring only a single rf input port at one end of the comb-line structure. Advantageously, the single rf input port, in combination with the inductive coupling between the current straps, provides a substantially constant impedance to an rf power source if the structure is sufficiently long or properly terminated. A single rf output port at the other end of the comb-line structure allows for the recirculation of the rf power, if needed. A multiplicity of U-shaped wickets loop over and enclose each current strap. The wickets advantageously eliminate capacitive coupling between the straps, yet allow inductive coupling to occur. The elimination of capacitive coupling between the straps eliminates the need for the discrete capacitors. Such wickets further function as a Faraday shield to shield the plasma from electrostatic fields, yet readily allow magnetic fields to pass into the plasma. In accordance with one aspect of the invention, the comb-line antenna structure is mounted on the inside of the outer wall of a tokamak so as to front the plasma. The magnetosonic waves are launched into the plasma so as to propagate in the direction of a minor axis of the tokamak, and such magnetosonic waves thus provide plasma heating and/or current drive in the tokamak. Advantageously, the single rf input port allows a good impedance match to be made with a high power rf generator, which impedance match is maintained despite variations in the plasma position and edge density. Further, the rf output port allows any rf power remaining at the output port to be recirculated back to the input port, thereby enhancing the efficiency of the launching structure. In accordance with another aspect of the invention, the Faraday shield is mechanically configured to be somewhat flexible, (i.e., not absolutely rigid). Thus, the wicket structure is able to flex, as needed, to accommodate thermal stresses that develop as the structure is used in close proximity to a high temperature plasma. The present invention may thus be broadly described as a comb-line antenna structure useful for launching fast magnetosonic waves in tokamaks, or equivalent "magnetic bottle" structures, containing high temperature plasma. The comb-line antenna structure includes a plurality of parallel current straps, with each current strap being enclosed within a multiplicity of wickets. Each of the wickets are grounded to a conductive ground plane, which conductive ground plane is a prescribed stand-off distance from the plurality of parallel current straps. Input power means apply rf input power to a first one of the plurality of parallel current straps. Each of the current straps is spaced a specified distance apart from an adjacent current strap so that some of the rf input power applied to the power input means is inductively coupled from one current strap to an adjacent current strap, with each of the current straps receiving some rf power. When positioned adjacent a conductive medium, such as a plasma, some of the rf power present at each current strap is launched from the respective current strap to produce a traveling magnetosonic wave within the conductive medium. It is thus a feature of the invention to provide a comb-line launching structure for use in a tokamak (or similar plasma-confining device) that efficiently launches a magnetosonic wave into a plasma mass from a location adjacent the plasma mass. It is another feature of the invention to provide such a comb-line launching structure, utilizing a plurality of parallel, inductively coupled current straps, wherein the mutual coupling between the current straps is used to an advantage rather than a disadvantage; and more particularly wherein such mutual coupling allows the launching structure to present a matched load to an rf input generator, even though the plasma position relative to the current straps, and the density of the plasma at its edge, may vary. It is a further feature of the invention, in accordance with one embodiment thereof, to provide a comb-line antenna structure that eliminates the need to use discrete capacitors with each of the current straps. It is still another feature of the invention to provide an effective Faraday shield for use with a comb-line launching structure in a tokamak, or other plasma-forming device, that shields the plasma from electrostatic fields, yet readily passes magnetic fields. It is yet an additional feature of the invention to provide a magnetosonic wave launching device for use with a tokamak, or other high operating temperature device, that is sufficiently bendable and pliable and able to react to thermal stresses without breakage or excessive movement towards the plasma.
	claims	1. A method of controlling a nuclear reactor during a load rejection transient, the nuclear reactor including a Reactor Coolant System having a hot leg with a temperature, Thot, and a cold leg with a temperature, Tcold, a turbine having an impulse chamber and a steam dump system having steam dump valves, comprising the steps of:generating a first temperature error signal based on an amount by which a reactor coolant average temperature exceeds a reference temperature, said reactor coolant average temperature determined from an average of Thot and Tcold, and said reference temperature determined from a pressure measured in the impulse chamber of the turbine;generating a second temperature error signal based on a power error signal provided when power level of the turbine is reduced and power level of the reactor exceeds the power level of the turbine;summing said temperature error signals to generate a valve control signal for the steam dump valves;actuating the steam dump system in response to said valve control signal. 2. The method of claim 1 wherein said turbine power is based on steam pressure measured inside the impulse chamber of the turbine. 3. The method of claim 1 wherein said load rejection is about fifty percent (50%). 4. The method of claim 1 wherein said valve control signal controls a valve positioner. 5. The method of claim 4 wherein said valve positioner enables opening of steam dump valves in said steam dump system. 6. The method of claim 5 wherein said steam dump valves are selected from the group consisting of condenser dump valves and atmospheric steam dump valves. 7. The method of claim 5 wherein said steam dump valves comprise at least four banks of valves. 8. The method of claim 1 further comprising converting said power mismatch error signal into a temperature error signal.
	claims	1. A group management apparatus configured to manage, as a plurality of groups, numerous installation devices installed in a plurality of buildings, the group management apparatus comprising:an acquiring component configured to acquire operating data of the numerous installation devices via controllers, the operating data being indicative of at least current operating conditions, each of the current operating conditions being one of energy-intensive consumption and temperature deviation, the controllers being placed in the buildings and controlling the numerous installation devices inside the buildings;a summarizing component configured tosummarize collective operating data values of the plurality of groups of installation devices, each collective operating data value being indicative of a collective current operating condition of each respective group,compare the collective operating data values of the plurality of groups with each other, andjudge whether or not the collective operating data value of each group meets a predetermined condition, the predetermined condition being met by one of the collective operating data values of a respective group being equal to or greater than a threshold value; anda screen generating component configured to generate a screen in which results, with respect to the plurality of groups, of the collective operating data values having been summarized by the summarizing component are juxtaposed. 2. The group management apparatus according to claim 1, whereinthe summarizing component is further configured to compareindividual operating data values that are operating data values of individual installation devices belonging to single groups with individual operating data values of other groups. 3. The group management apparatus according to claim 2, whereinthe summarizing component is further configured to judge whether or not the individual operating data values meet the predetermined condition. 4. The group management apparatus according to claim 3, whereinthe summarizing component is further configured to compare, per group, the individual operating data values or the collective operating data values with a predetermined reference value, and to judge whether or not the individual operating data values or the collective operating data values meet the predetermined condition based on the comparison. 5. The group management apparatus according to claim 4, further comprisinga reference value setting component configured to set the predetermined reference value based on the operating data that have been acquired from the numerous installation devices by the acquiring component. 6. The group management apparatus according to claim 3, whereinthe screen generating component is further configured to generate a screen in which magnitude relations of installation devices meeting the predetermined condition in each of the groups can be compared. 7. The group management apparatus according to claim 6, whereinthe screen generating component is further configured to generate a screen in which specific values that are the individual operating data values of installation devices meeting the predetermined condition can be compared with overall values that are the operating data values of all installation devices. 8. The group management apparatus according to claim 7, whereinthe summarizing component is further configured to determine numbers of installation devices meeting the predetermined condition in each of the groups, andthe screen generating component is further configured to include the numbers in the screen. 9. The group management apparatus according to claim 6, whereinthe magnitude relations are displayed graphically. 10. The group management apparatus according to claim 6, whereinthe comparison of magnitude relations includes graphically juxtaposing the magnitude of a first of the collective operating data values that exceeds a threshold value against the magnitude of a second of the collective operating values indicative of total operation, the total operation including operation corresponding to collective operating data values exceeding the threshold value and operation corresponding to collective operating data values which do not exceed the threshold value. 11. The group management apparatus according to claim 2, whereinthe collective operating data values are mean values of the individual operating data values of installation devices belonging to single groups. 12. The group management apparatus according to any one of claims 2, whereinthe collective operating data values are totals of the individual operating data values of installation devices belonging to single groups. 13. The group management apparatus according to claim 2, further comprisinga classification information storage area configured to store classification information used to classify the numerous installation devices into the groups,the summarizing component being further configured to summarize the individual operating data values or the collective operating data values per each group into which the numerous installation devices have been classified by the classification information. 14. The group management apparatus according to claim 1, further comprisingan evaluation item storage area configured to store a plurality of items for evaluating the current operating conditions of the numerous installation devices,the summarizing component being further configured to evaluate the current operating conditions based on several items of the plurality of items or all items of the plurality of items, andthe screen generating component being further configured to generate a screen in which evaluation results based on the plurality of items can be checked en bloc. 15. The group management apparatus according to claim 1, wherein.the plurality of buildings are included in a single management domain. 16. A group management system configured to manage, as a plurality of groups, numerous installation devices installed in a plurality of buildings, the group management system comprising:controllers placed in the buildings and controlling the numerous installation devices installed inside the buildings; anda group management apparatus connected to the controllers and managing the numerous installation devices as groups via the controllers, the group management apparatus includingan acquiring component configured to acquire operating data of the numerous installation devices via the controllers, the operating data being indicative of at least current operating conditions, each of the current operating conditions being one of energy-intensive consumption and temperature deviation,a summarizing component configured tosummarize collective operating data values of the plurality of groups of installation devices, each collective operating data value being indicative of a collective current operating condition of each respective group,compare the collective operating data values of the plurality of groups with each other, andjudge whether or not the collective operating data value of each group meets a predetermined condition, the predetermined condition being met by one of the collective operating data values of a respective group being equal to or greater than a threshold value, anda screen generating component configured to generate a screen in which results, with respect to the plurality of groups, of the collective operating data values having been summarized by the summarizing component are juxtaposed. 17. A group management method of managing, as a plurality of groups, numerous installation devices installed in a plurality of buildings, the group management method comprising:acquiring operating data of the numerous installation devices via controllers, the operating data being indicative of at least current operating conditions, each of the current operating conditions being one of energy-intensive consumption and temperature deviation, the controllers being placed in the buildings and controlling the numerous installation devices inside the buildings;summarizing collective operating data values of the plurality of groups of installation devices, each collective operating data value being indicative of a collective current operating condition of each respective group;comparing the collective operation data values of the plurality of groups with each other;judging whether or not the collective operating data value of each group meets a predetermined condition, the predetermined condition being met by one of the collective operating data values of a respective group being equal to or greater than a threshold value; andgenerating a screen in which results, with respect to the plurality of groups, of the collective operating data values having been summarized are juxtaposed. 18. A group management program configured to be executed in a computer to manage, as a plurality of groups, numerous installation devices installed in a plurality of buildings, the group management program comprising:acquiring operating data of the numerous installation devices via controllers, the operating data being indicative of at least current operating conditions, each of the current operating conditions being one of energy-intensive consumption and temperature deviation, the controllers being placed in the buildings and controlling the numerous installation devices inside the buildings;summarizing collective operating data values that are values of the plurality of groups of installation devices, each collective operating data value being indicative of a collective current operating condition of each respective group;comparing the collective operating data values of the plurality of group with each other;judging whether or not the collective operating data value of each group meets a predetermined condition, the predetermined condition being met by one of the collective operating data values of a respective group being equal to or greater than a threshold value; andgenerating a screen in which results, with respect to the plurality of groups, of the collective operating data values having been summarized are juxtaposed.
053848179	abstract	X-ray dispersive elements comprise a stacked array of layer pairs of boron nitride and either nickel, tungsten, chromium, vanadium, iron, manganese, cobalt and combinations thereof. The boron nitride is preferably deposited through a planar magnetron sputtering process.
	abstract	A lighting system, particularly for use in extreme ultraviolet (EUV) lithography, comprising a projection lens for producing semiconductor elements for wavelengths ≦193 nm is provided with a light source, an object plane, an exit pupil, a first optical element having first screen elements for producing light channels, and with a second optical element having second screen elements. A screen element of the second optical element is assigned to each light channel that is formed by one of the first screen elements of the first optical element. The screen elements of the first optical element and of the second optical element can be configured or arranged so that they produce, for each light channel, a continuous beam course from the light source up to the object plane. The angles of the first screen elements of the first optical element can be adjusted in order to modify a tilt. The location and/or angles of the second screen elements of the second optical element can be adjusted individually and independently of one another in order to realize another assignment of the first screen elements of the first optical element to the second screen elements of the second optical element by displacing and/or tilting the first and second screen elements.
	abstract	A system for storing exothermic materials to enhance heat removal is provided that includes a first canister and a second canister. Preferably, the first canister incorporates a canister wall defining a first storage volume that is adapted to receive exothermic material therein. The second canister incorporates an inner wall and an outer wall, with the inner wall defining a canister-receiving, volume that is adapted to receive at least a portion of the first canister therein. Additionally, the outer wall and the inner wall may define a second storage volume which is adapted to receive exothermic material therein.
	description	The present invention relates to nuclear fuel assemblies. By way of example, it applies to fuel assemblies for pressurized water nuclear reactors. Generally, nuclear fuel assemblies comprise nuclear fuel rods and a support skeleton having two nozzles, guide tubes interconnecting the nozzles, and spacer grids for holding the rods. Each spacer grid comprises two sets of crossed plates and an outer belt, thus defining cells, some of which have guide tubes passing through them and others have fuel rods passing through them. The plates are provided with means for holding the rods at the nodes of a substantially regular array and they are secured to at least some of the guide tubes. At least one of the spacer grids also serves to support the rods. For this purpose, it is usually provided with springs that are cut out in the plates or that are fitted to the plates, and that serve to press the rods against dimples stamped in the plates and forming the opposite faces of the cells. The other grids serve only to hold the rods at the nodes of the array. To do this, they present dimples on each of the faces of a cell having a rod passing therethrough, the dimples serving to press against the rod. French patent No. 2 665 291 also discloses additional mixer grids for interposing between the spacer grids and having fins for improving the mixing of the cooling fluid flowing through the assemblies. Once manufactured, such assemblies extend rectilinearly and vertically along a direction that is referred to as being “axial”. Once in place in a reactor, these assemblies deform because of the irradiation and can take on C-shapes, S-shapes, or W-shapes. Such deformations lead to numerous problems. In operation, they make it more difficult to insert control and shutdown clusters into the guide tubes. During handling, these deformations increase the risk of assemblies catching on one another, e.g. during operations of loading or unloading the core of the reactor. An object of the invention is to solve this problem by limiting the deformation of nuclear fuel assemblies under irradiation. To this end, the invention provides a nuclear fuel assembly of the type comprising nuclear fuel rods and a supporting skeleton having two nozzles, guide tubes interconnecting the nozzles, and spacer grids for holding the rods, which grids are secured to the guide tubes, the assembly being characterized in that it further comprises at least one lattice reinforcing device for reinforcing the support skeleton, the lattice reinforcing device being disposed between two spacer grids and being secured to the guide tubes. In particular embodiments, the assembly may further comprise one or more of the following characteristics taken singly or in any technically feasible combination: the nuclear fuel rods are disposed in a substantially regular array and the lattice reinforcing device does not extend between the peripheral rods; the lattice reinforcing device does not extend between the peripheral layer of rods and the adjacent layer of rods; the lattice reinforcing device does not have means for mixing a cooling fluid that is to flow through the nuclear fuel assembly; the lattice reinforcing device does not have an arrangement for holding nuclear fuel rods; the lattice reinforcing device comprises two sets of crossed plates that are secured to one another, the plates defining between them cells for receiving guide tubes and cells for receiving nuclear fuel rods; and the cells for receiving nuclear fuel rods are of dimensions greater than the dimensions of the rods so as to receive them with clearance. The invention also provides the use of a nuclear fuel assembly comprising nuclear fuel rods and a support skeleton, the assembly having: two nozzles; guide tubes interconnecting the nozzles; and spacer grids for holding the rods;at least one lattice reinforcing device for reinforcing the support skeleton, the lattice reinforcing device being disposed between two spacer grids and being secured to the guide tubes. In particular implementations: the lattice reinforcing device does not have an arrangement for mixing a cooling fluid that is to flow through the nuclear fuel assembly; the lattice reinforcing device does not have an arrangement for holding nuclear fuel rods; the lattice reinforcing device comprises two sets of crossed plates that are secured to one another, the plates defining between them cells for receiving guide tubes and cells for receiving nuclear fuel rods; and the cells for receiving nuclear fuel rods are of dimensions greater than those of the rods, so as to receive them with clearance. FIG. 1 is a diagram of a nuclear fuel assembly 1 for a pressurized water reactor. The assembly 1 extends vertically and in rectilinear manner along a longitudinal direction A. The assembly 1 mainly comprises nuclear fuel rods 3 and a structure or skeleton 5 for supporting the rods 3. In conventional manner, the rods 3 extend vertically and are disposed in a substantially regular, square-based array, as can be seen in FIG. 3 where the rods 3 are shown in dashed lines. In the example shown, the assembly 1 comprises a group of 264 rods 3 and, seen from above, the array forms a square having a side of 17 rods. The group of rods 3 thus possesses four side faces 6 each having 17 rods. The supporting skeleton 5 essentially comprises: a bottom nozzle 7 and a top nozzle 9; guide tubes 11 for receiving the rods of a control or shutdown cluster; and spacer grids 13 for holding the rods 3 at the nodes of the array. The nozzles 7 and 9 are secured to the longitudinal ends of the guide tubes 11. As can be seen in FIG. 3, in which a spacer grid 13 is drawn in dashed lines, each spacer grid 13 comprises, for example, two sets of crossed plates 15 and a peripheral belt 17 surrounding the peripheral layer 19 of rods 3. The grid 13 defines cells 20, most of which receive a respective rod 3. Bosses (not shown) are provided in the plates 15 to press against the rods 3 and hold them at the nodes of the array. Each of the other cells 20 receives a guide tube 11. Also in conventional manner, the spacer grids 13 are secured to the guide tubes 11 and are distributed along the height of the rods 3. The rods 3 can be held axially by a single spacer grid 13, e.g. the top gird 13, which is then provided for this purpose with springs for thrusting the rods 3 against dimples cut out in the plates 15 or fitted thereto. In the invention, between the spacer grid 13, the assembly 1 includes intermediate devices 21 for reinforcing the skeleton 5. For reasons explained below, these reinforcing devices 21 are not visible from outside the assembly 1, and they are therefore shown in dashed lines in FIG. 1. In the example shown, an intermediate reinforcing device 21 is provided between each pair of spacer grids 13. Since the structure of the intermediate reinforcing devices 21 is similar, only one device 21 is described with reference to FIGS. 2 and 3. It should be observed that only segments of the guide tubes 11 are shown in FIG. 2. In FIG. 3, the guide tubes 11 and the intermediate reinforcing device 21 are drawn in continuous lines. The device 21 comprises two sets of crossed plates 23 that are secured to one another, e.g. by welding at their points of intersection. By way of example, the plates 23 are about 0.425 millimeters (mm) thick and of a height lying in the range about 18 mm to about 28 mm. They are preferably made of zirconium alloy. Between them, the plates 23 define cells 25, each for receiving a respective guide tube 11, and cells 27 for receiving the rods 3. As can be seen in FIG. 3, some of the cells 27 are individual cells that receive only one rod 3, whereas others receive two or four rods 3. The plates 23 of the intermediate reinforcing device 21 form a lattice structure extending solely between the guide tubes 11. This lattice structure thus forms an openwork structure. Thus, the transverse extent of the plates 23, and thus of the reinforcing device 21, is limited. In particular, the plates 23 do not extend between the rods 3 of the outer peripheral layer 19 of rods 3, nor between said layer 19 and the intermediately adjacent layer 29 which, in the example shown, comprises 15 rods per side. The intermediate reinforcing device 21 stops in the vicinity of this layer 29. The plates 23 do not have any arrangement for holding the rods 3, and as a result the cells 27 are of dimensions that are greater than the dimensions of the rods 3, thereby surrounding them with clearance. Furthermore, the intermediate reinforcing device 21 has no arrangement for mixing cooling fluid flowing through the fuel assembly 1, e.g. no fins. The intermediate reinforcing device 21 is secured to the guide tubes 11, e.g. by welding in slightly bulging zones 31 (FIG. 2) of the plates 23. Such welding may be applied to the tops and/or the bottoms of the plates 23. In a variant shown in FIG. 4, the plates 23 may be welded to the guide tubes 11 via welding tabs 33 which project from the plates 23, e.g. upwards. If the assembly 1 includes an instrumentation tube instead of the central guide tube 11, then the intermediate reinforcing devices 21 can be welded thereto. Because of the presence of the intermediate reinforcing devices 21, both the skeleton of the support 5 and thus the entire assembly 1 are more rigid. This is confirmed by FIG. 5 which shows the result of simulations of lateral deformations to nuclear fuel assemblies before irradiation. In this figure lateral displacement D in mm is plotted along the abscissa and the force E in daN necessary for obtaining this deformation is plotted up the ordinate. Curve 35 corresponds to a prior art assembly immediately after manufacture, i.e. prior to irradiation. Curve 37 corresponds to the assembly 1 of FIG. 1 immediately after manufacture. Thus, the presence of the intermediate reinforcing devices 21 enables the stiffness or lateral rigidity of the assembly 1 to be increased by about 60% at the beginning of its lifetime compared with a conventional assembly. FIG. 6 corresponds to analogous simulations performed after irradiation. Curve 39 corresponds to a conventional assembly and curve 41 to the assembly 1 of FIG. 1. The increase in the lateral rigidity of the assembly 1 thus remains after irradiation, with this increase continuing to be about 60%. Thus, the assembly 1 presents stiffness at the end of its lifetime equivalent to that of a conventional assembly at the beginning of its lifetime. The use of intermediate reinforcing devices 21 for reinforcing the support skeleton 5 makes it possible to compensate for the effect of irradiation. It has been found that the reduction in rigidity of conventional assemblies after irradiation is due to the guide tubes creeping and to changes to the conditions whereby rods 3 are held by the skeleton 5, such that the rods 3 contribute about 65% of the rigidity of an assembly prior to irradiation but contribute no more than about 40% of the stiffness after irradiation. The stiffening of the skeleton 5 by the intermediate reinforcing devices 21 thus makes it possible to increase the lateral stiffness thereof, including after irradiation. As a result the openwork structure of the reinforcing devices 21, which are also of small transverse extent, ensures that head losses in the cooling fluid remain limited. In the variant shown in FIG. 7, the reinforcing device 21 may be constituted by a lattice structure that is more dense such that all of the cells 27 are individual cells each receiving no more than a single rod 3. This variant makes it possible to further increase the lateral rigidity of the assembly 1 but also increases head loss in the cooling fluid passing through the assembly 1. In yet another variant, the intermediate reinforcing device 21 can extend laterally beyond the guide tubes 11, possibly as far as the peripheral layer 19 of rods 3, and may also include an outer belt. Thus, the device 21 forms a lattice structure analogous to a spacer grid 13. The outer belt can improve the ability of the assembly 1 to withstand impacts during handling and under accident conditions. In the above-described example, the number of plates in the device 21 would then be 36. More generally, the intermediate reinforcing devices 21 can be secured to the guide tubes by arrangement other than welding, e.g. by tube expansion, by sleeving, etc. . . . Similarly, the assembly 1 need not include an intermediate reinforcing device 21 between each pair of spacer grids 13. In certain variants, the intermediate reinforcing devices 21 may also have an arrangement for holding the rods 3 and/or an arrangement for mixing the cooling fluid flowing through the assembly. Naturally, intermediate reinforcing devices 21 could be sold on their own.
047587261	claims	1. In a system for exchanging a plurality of collimators between a measuring position and a storage position, a measuring means being at said measuring position for measuring radiation, a structure comprising storage means for individually storing a plurality of separated collimators, cart means for selecting one collimator from said storage means and for placing said one collimator relative to said measuring means, said cart means returning said one collimator from said measuring means to said storage means, wherein said one collimator is transferred by said cart means between said storage means and said measuring means only in a given orientation relative to said storage means and said measuring means. 2. A structure according to claim 1, wherein each of said storage means, said measuring means, and said cart means has locking pins, and wherein said collimators have catching sockets for cooperating with said locking pins. 3. A structure according to claim 2, wherein said locking pins are mushroom-shaped pins, and each of said storage means, said measuring means, and said cart means has at least three pins. 4. A structure according to claim 2 or claim 3, wherein each of said collimators includes a rotatable catching socket for each of said pins, said socket having an opening cooperating with each of said pins at both a top and a bottom portion of said socket. 5. A structure according to claim 1, claim 2, or claim 3, wherein said cart means includes means for protected height adjustment to provide collision free access to said storage means and said measuring means. 6. A structure according to claim 1, claim 2, or claim 3, wherein each of said plurality of collimators includes resilient clamping means for cooperating with said measuring means, said resilient clamping means being activated upon coupling. 7. A structure according to claim 1, claim 2, or claim 3, wherein each of said collimators includes a collimator ring surrounding a collimator periphery, said collimator ring having a plurality of openings at both sides of said ring, said plurality of openings at one side of said ring being shifted along an arc of a circle of said ring relative to said plurality of openings at an opposite side of said ring, and wherein said openings cooperate with pins on each of said storage means, said measuring means, and said cart means.
046613048	summary	BACKGROUND OF THE INVENTION This invention relates generally to a method and apparatus for transferring energy to a plasma immersed in a magnetic field, and relates particularly to an apparatus for heating a plasma of low atomic number ions to high temperatures by transfer of energy to plasma resonances, particularly the fundamental and harmonics of the ion cyclotron frequency of the plasma ions. This invention transfers energy from an oscillating radio-frequency field to a plasma resonance of a plasma immersed in a magnetic field. Research devices have been devised for studying the properties of high temperature plasmas, and for the production therein of thermonuclear ractions. In such devices, it is necessary that the plasma, a gas comprising approximately equal numbers of positively charged ions and free electrons, be raised to a high temperature. One general type of device for plasma confinement, the Tokamak, comprises an endless, closed tube, such as a toroid, with a geometrically co-extensive, externally imposed magnetic field (e.g., a toroidal magnetic field) in which magnetic lines of induction extend around the toroid generally parallel to its minor axis. Such a magnetic field is conventionally provided by electrical currents in one or more conductive coils encircling the minor axis of the toroid. The combination of a poloidal magnetic field produced by the plasma current, with the toroidal magnetic field produced by the toroidal coil current, is suitable for providing helix-like magnetic field lines that generally lie on closed, nested magnetic surfaces. The plasma is accordingly subjected to confining, constricting forces generated at least in part, by the current flowing in the plasma. The resulting magnetic field provides for a diffused pinching in the confining magnetic field which may be substantially greater than the outward pressure of the plasma. The steady state operation of toroidal plasma systems is a recognized goal in the development of plasma technology, and substantial effort has been directed to non-inductive plasma current forming and heating methods which might provide the capability for steady-state operation. Techniques currently being considered for providing auxiliary heating in toroidal plasma apparatus include high energy neutral beam injection, radio frequency wave heating, adiabatic compression, and several other less developed techniques including relativistic electron beam injection, cluster injection, plasma-gun injection, and laser-pellet hot plasma formation. This invention is directed to radio frequency wave heating. The excitation and damping of waves is a heating method similar in many ways to the injection and thermalization of energetic ions; the efficiencies of power transfer to the plasma are at least roughly comparable. Wave heating has an advantage of relatively rapid thermalization of the wave energy; this means that the energy density of the waves in the plasma can remain small compared with the plasma thermal energy density. If the high energetic-ion pressures associated with neutral-beam heating were to give rise to problems of equilibrium or stability, wave heating might circumvent these problems. In hot dense plasmas, the closest rival method, neutral beam injection, requires very high beam energies if power is to be deposited deep in the plasma interior. Attention is therefore being directed to wave heating techniques. Due to long-range electromagnetic interactions between charged particles and external electromagnetic fields, there exists a host of collective motions (waves) the plasma (see for example. T. H. Stix, "The Theory of Plasma Waves", McGraw-Hill, New York (1962). The existence of these waves provides a means for coupling of external electromagnetic energy such as radio frequency (r-f) electromagnetic wave energy into the plasma. With conventional vacuum vessels, an rf antenna coil generates an oscillating magnetic field at the edge of the plasma. The oscillating magnetic field causes a fast magnetosonic wave to be formed in the plasma. When the frequency of this wave matches the ion cyclotron frequency (or a multiple of that frequency), the wave will be damped by the plasma particles. The wave will transfer its energy to the ions, causing them to spiral at a faster velocity and in a helical path of greater radius. Through collisions with other plasma particles, these more energetic ions will transfer their energy to other plasma particles, thus heating the plasma. The ion cyclotron range of frequencies is about 10 MHz to 200 MHz in present devices. Plasma waves which may have utilization in respect to plasma heating, in ascending frequency, are: Alfven waves, ion cyclotron waves, lower hybrid waves, and electron cyclotron waves. In connection with Alfven wave heating i.e., for frequencies below the io cyclotron frequency, <ci, there are two modes of heating: EQU .omega..sup.2 =k.vertline..vertline..sup.2 V.sub.A.sup.2 EQU .omega..sup.2 =k.sup.2 V.sub.A.sup.2. For typical fusion grade plasmas, the frequency of the first mode of the shear Alfven wave is less than 1.0 MHz and the vacuum wave length, 2.pi./k.vertline..vertline. is the order of several meters. Disadvantages of conventional Alfven wave utilization include the requirement for protection and cooling of the coils within the metallic vessel, and possible large impurity production. Furthermore, because the frequency range is below the ion cyclotron frequency range, Alfven wave excitation may include enhanced plasma loss. Conventional Alfven wave heating techniques have not been thoroughly tested on tokamaks, although low-power experiments have been conducted. As the excitation frequency, .omega. approaches the ion cyclotron frequency .omega.ci, the shear Alfven wave becomes an ion cyclotron wave with frequency .omega.ci. The term "ion cyclotron wave" refers to a natural oscillation or wave in a plasma which is immersed in a confining magnetic field, where the motion of the plasma ions taking part in the natural oscillation or wave is primarily transverse to the lines of force of the confining magnetic field, where the wave length (measured along a line of force) is relatively short, and where the frequency is slightly below the ion cyclotron frequency for the ions. Plasma heating in tokamaks by means of fast Alfven waves in the Ion-Cyclotron Range of Frequencies (ICRF) has achieved notable experimental successes which are understood in terms of theory. As a result, ICRF plasma heating has become the preferred option for heating first-generation tokamak reactors to ignition. (W. M. Stacey et al., U.S. FED-INTOR Activity and U.S. Contribution to the International Tokamak Reactor Phase-2A Workshop," Georgia Institute of Technology Report USA FED-INTOR/82-1 (1982); P. H. Rebut, "JET Joint Undertaking: March 1982," in Proceedings of the Third Joint Varenna-Grenoble International Symposium Heating in Toroidal Plasmas, Grenoble, 1982, Vol. III, pp. 989-998). In all the experiments to date, the couplers (i.e., the antennas) which radiate the fast Alfven waves into the plasma have been induction loops located within the vacuum vessel. In addition, the coupling loops in the PLT tokamak are covered with a ceramic insulator. Such antennas are unsatisfactory for use in a fusion reactor, where engineering considerations require a modular, easily replaced antenna. The potential radiation damage to insulators from fusion neutrons calls for an all-metal coupler design, D. Q. Hwang, G. Grotz, and J. C. Hosea, "Surface Physics Problems During CRF Heating of Tokamak Plasma," J. Vac. Sci. Technol. 20, 1273 (1982). Further, the launching coils may perhaps be a significant source of plasma impurities. This is a drawback in high-powered present day experiments, and will become more so in an operating tokamak reactor environment. Also, difficulties arise since the loop antenna is directly fed through a transmission line, and the large inductance of the loop causes high voltages at the vacuum feed throughs. This in turn, imposes a serious limitation on the power handling capability of the coupler. Waveguide wave lauchers are conceptually more desirable, but in practice, waveguide approaches are found to launch spectra that are far from optimal. One common antenna (or coupler) in use today is the box-type cavity which includes radiator members having a length approximately equal to one-half the free space wavelength of the rf output of the radio frequency generator driving the cavity. In many applications, resonators of this type are too bulky, and are difficult to service in a working machine. Due to limited availability of space on research plasma devices, and an expected similar limitation on operational fusion reactors, it is desirable to provide a launcher arrangement which is as small as possible, especially in the poloidal direction. Given the present state of the art, practical coupler designs must be proved on research devices such as the "Big-Dee" Doublet III, JET and TFTR tokamaks. These tokamaks have magnetic field strengths that are the same as (or smaller than) the fields envisioned for a reactor. Since most reactor ICRF heating schemes utilize second harmonic heating, the impressed frequencies are similar in reactor and research tokamaks, while the actual size of a research tokamak is roughly a factor-of-two smaller than that of a fusion reactor. Resonant cavities must be able to accomomodate the smaller research tokamaks with no change in their basic configurations. It is therefore an object of the present invention to provide a resonant cavity launcher that is much shorter in the polodial direction than arrangements presently available. Current estimates of energy levels needed for successful higher-density reactor operations requires still higher wave coupling efficiencies than those presently available. The primary role that ICRF heating will play in the tokamak reactor will be in the heating of the plasma at the fundamental and second harmonic regimes. For the first commercial-scale fusion reactor, the mode of heating will require rf power levels in the 100 megawatt range. At the present time, existing rf systems for plasma machines are capable of delivering only 5 megawatts. It is therefore an object of the present invention to provide an rf launcher system that efficiently couples greater levels of rf energy to the plasma at the ion-cyclotron resonant frequency. More specifically, it is another object of the present invention to provide a resonant cavity antenna which provides an orientation of the confinement and radiating magnetic fields to effectively radiate fast Alfven waves. A related object of the present invention is to provide a higher-power resonant cavity launcher of more compact size, and which operates at a substantially higher power flux than previous antenna designs. A high power flux (.about.10 kW/cm.sup.2) is desirable in a reactor to reduce the fraction of the wall area devoted to heating. Another object of the present invention is to provide within the resonant cavity antenna, magnetic insulation in the regions of high energy electric fields. More specifically, it is an object of the present invention to provide a coupler which impresses oscillating magnetic fields having a strong toroidal component, on the plasma, and to have the strong electric field associated with the high Q antenna circuit directed orthogonal to a main toroidal magnetic field of the plasma confinement device, to thereby provide the magnetic insulation effect required to achieve higher voltage breakdown conditions. It is another object of the present invention to provide an arrangement for launching fast Alfven waves which circumvents impurity problems by avoiding an intrusion into the vacuum vessel, beyond the first wall. SUMMARY A resonant coil cavity launches fast Alfven waves for efficient coupling to plasmas which are immersed in a strong magnetic field. The cavity includes frequency-determining reactive circuit components which are located within a one-quarter wavelength of the plasma containment chamber. Waves launched by the cavity energize plasma components within the Ion-Cyclotron Range of Frequencies. The strong electric fields associated with the reactive energy are entirely contained within the cavity, and are oriented perpendicular to the strong magnetic field surrounding the plasma. A first embodiment of the present invention is comprised of first and second chambers. The first chamber contains a vertical current rod having two ends. One of which is joined to a wall of the first chamber. The second chamber contains a horizontally directed capacitor plate which is joined to the other end of the current rod. A portion of the current rod, adjacent the other end, penetrates the second chamber through an elongated wall which is common to the first and second chambers. A capacitive gap is formed between the horizontal plate and the common wall. A second embodiment of the present invention comprises a single chamber having two parallel spaced-apart plates joined to a first wall of the chamber. A third plate is parallel to, and interposed between the first two plates. The third plate is joined to another, opposing wall of the chamber. Capacitive gaps are formed between the first and third plates and between the second and third plates. In a third embodiment of the present invention two coextensive, overlying spaced-apart plates are mounted within a plasma chamber. The plates are joined together at one end to a first end wall. A second endwall is joined to the plates and to the chamber wall. A capacitive gap is formed between the chamber wall and the plates positioned adjacent thereto. A second gap is formed between the two plates. In each embodiment, the cavity is oriented such that the plates are tangential to the strong magnetic field, so as to take advantage of the resulting magnetic insulation effect. Also, in each embodiment, the reactive circuit elements of the cavity are spaced no further than one-quarter wavelength from the plasma containment vessel. Correspondingly, all other dimensions of the cavity are less than one-quarter wavelength.
050013548	claims	1. A glove for use in medical procedures having an average wall thickness between about 6 to 20 thousands of an inch, said glove comprising at least one layer comprising a mixture of dried rubber latex and high specific gravity metal particles, said at least one layer being pin-hole free and being capable of absorbing between about 50 and 80 percent of incident radiation of between about 60 to 100 KVP, and said glove being sufficiently flexible to permit it to be used with dexterity during a medical procedure. 2. A glove according to claim 1 wherein the thickness of the glove distal to the first knuckle of the finger sections and the thumb section is thinner than the thickness of the remainder of the glove. 3. A glove according to any one of claims 1 or 2 wherein said high specific gravity metal particles are formed out of tungsten. 4. A glove according to any one of claims 1 or 2 wherein said glove comprises multiple layers wherein at least one layer comprises dried rubber latex free of high specific gravity metal particles and at least one layer contains said high specific gravity metal particles. 5. A glove according to any one of claims 1 or 2 wherein said surgical glove comprises multiple layers wherein at least one layer comprises dried rubber latex free of high specific gravity metal particles and at least one layer which contains tungsten particles. 6. A glove for use in medical procedures having an average wall thickness between about 6 to 20 thousands of an inch, said glove comprising at least one layer comprising a mixture of dried rubber latex and high specific gravity metal particles, said at least one layer having a substantially even outer surface, said at least one layer being pin-hole free, and said glove being capable of absorbing between about 50 and 80 percent of incident radiation of between about 60 to 100 KVP, and said glove being sufficiently flexible to permit it to be used with dexterity during a medical procedure. 7. A glove according to claim 6 wherein the thickness of the glove distal to the first knuckle of the finger sections and the thumb section is thinner than the thickness of the remainder of the glove. 8. A glove according to any one of claims 6 or 7 wherein said high specific gravity metal particles are formed out of tungsten. 9. A glove according to any one of claims 6 or 7 wherein said glove comprises multiple layers wherein at least one layer comprises dried rubber latex free of high specific gravity metal particles and at least one layer contains said high specific gravity metal particles. 10. A glove according to any one of claims 6 or 7 wherein said surgical glove comprises multiple layers wherein at least one layer comprises dried rubber latex free of high specific gravity metal particles and at least one layer which contains tungsten particles. 11. A glove for use in medical procedures having an average wall thickness between about 6 to 20 thousands of an inch, said glove comprising at least one layer comprising a mixture of dried rubber latex and high specific gravity particles, said mixture being formed by suspending natural rubber latex particles and said high specific gravity particles in a liquid suspension medium so as to create a latex-particle suspension, with said high specific gravity particles comprising between about 5 and 10 volume percent of the latex-particle suspension, said at least one layer being pin-hole free, and said glove being capable of absorbing between about 50 to 80 percent incident radiation of between 60 to 100 KVP, and said glove being sufficiently flexible to permit it to be used with dexterity during a medical procedure. 12. A glove according to claim 11 wherein the thickness of the glove distal to the first knuckle of the finger sections and the thumb section is thinner than the thickness of the remainder of the glove. 13. A glove according to any one of claims 11 or 12 wherein said high specific gravity metal particles are formed out of tungsten. 14. A glove according to any one of claims 11 or 12 wherein said glove comprises multiple layers wherein at least one layer comprises dried rubber latex free of high specific gravity metal particles and at least one layer contains said high specific gravity metal particles. 15. A glove according to any one of claims 11 or 12 wherein said surgical glove comprises multiple layers wherein at least one layer comprises dried rubber latex free of high specific gravity metal particles and at least one layer which contains tungsten particles. 16. A glove for use in medical procedures having an average wall thickness of between about 6 to 20 thousands of an inch, said glove comprising at least one layer comprising a mixture of dried rubber latex and tungsten particles, said mixture being formed by suspending natural rubber latex particles and said tungsten particles in a liquid suspension medium so as to create a latex-particle suspension, with said tungsten particles comprising between about 3 to 20 volume percent of the latex-particle suspension, with said at least one layer being pin-hole free. 17. A glove according to claim 16 wherein said tungsten particles comprise between about 5 and 10 volume percent of the latex-particle suspension. 18. A glove according to claim 17 wherein said average wall thickness does not exceed 15 thousands of an inch. 19. A glove according to claim 16 wherein said average wall thickness does not exceed 15 thousands of an inch.
040452875	summary	BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel assembly with easily detachable components, which assembly comprises a bundle of fuel rods with a plurality of substantially parallel, vertical fuel rods, which are provided with extended upper and lower end plugs, a bottom plate and a grid-formed top plate provided with attachment holes for said upper end plugs, a predominant number of upper end plugs being each surrounded by a compressible spring, a number of fuel rods being screwed by their lower end plugs in threaded holes in said bottom plate, the upper end plugs of these fuel rods having a portion, located above said top plate, which is provided with a nut. 2. The Prior Art A fuel assembly of this type is known from U.S. Pat. No. 3,741,868. The fuel rods shown in this patent, which are passed through the top plate and provided with nuts on the upper side of said top plate, have no locking device for the nuts which is suitable when slacking off the nut by a remote-controlled tool. SUMMARY OF THE INVENTION This deficiency is remedied by a fuel assembly according to the invention. According to the invention, nuts on the top plate have downward projections which can engage against the side of the grid of the top plate. The length of the projection is such that, when the top plate is pressed down by a downwardly directed spring compressing force, the projection is cleared so that the nut can be unscrewed.
042008646	abstract	A process control installation has means for sensing a plurality of physical conditions connected to means for comparing the condition to a reference. A differential signal is fed to a corresponding reproduction circuit which in turn feeds it to inputs of a plurality of majority decision circuits. The majority decision circuits are in turn connected to pairs of logic circuit trains which in turn are connected to other logic circuitry for intrinsic security.
	description	This subject matter disclosed herein relates generally to diagnostic imaging systems, and more particularly to detector collimation in Nuclear Medicine (NM) imaging systems. In NM imaging, radiopharmaceuticals are taken internally and then detectors (e.g., gamma cameras), typically mounted on a gantry, capture and form images from the radiation emitted by the radiopharmaceuticals. The NM images primarily show physiological function of, for example, a patient or a portion of a patient being imaged. In some types of scans, such as when scanning the whole body or with large patients, the portion of the patient being imaged may require the entire field of view of a conventional large size imaging detector. However, when imaging a structure that is smaller than the field of view of the imaging detector, such as the heart, liver, kidney, brain, breast or a tumor, portions of the imaging detector will acquire patient data outside of the structure of interest. Therefore, an effective sensitivity is decreased that is unrelated to collimator geometrical sensitivity, but results from the opportunity lost by not collecting useful information. Collimation may be used to focus the field of view. In particular, a converging collimator can be used to improve the sensitivity of the detector over a limited field of view. For example, conventional converging fan beam collimators may be used wherein the lines of responses converge along a line. However, because the focal line is beyond the region of interest, the imaging volume decreases with decreasing distance to the focus such that objects of interest may be outside of the field of view and not imaged. Thus, multiple image scans may need to be performed or different types of collimators may be needed for different scans. In accordance with an embodiment, a collimator for a radiation imaging detector is provided that includes a plurality of adjustable segments and a plurality of collimator holes within each of the plurality of adjustable segments. The plurality of adjustable segments are configured to move independently of a detector to adjust a field of view of the collimator holes. In accordance with another embodiment, a nuclear medicine (NM) imaging system is provided that includes a gantry and at least one imaging detector supported on the gantry configured to rotate about the gantry defining an axis of rotation. The NM imaging system further includes a segmented collimator connected to the at least one imaging detector, wherein the segmented collimator has a plurality of movable segments configured to move independently of the at least one imaging detector such that the movable segments are independently controllable. The NM imaging system also includes a controller configured to control movement of the movable segments. In accordance with yet another embodiment, a method for collimating a detector of an imaging system is provided. The method includes configuring a segmented collimator to provide movement of each of a plurality of segments independently of a detector to adjust a field of view of collimator holes of the plurality of segments and coupling the segmented collimator to the detector of the imaging system. The method further includes providing a controller to control the imaging system to move at least one of the plurality of segments, the detector or a gantry of the imaging system to which the detector is coupled. The foregoing summary, as well as the following detailed description of certain embodiments, will be better understood when read in conjunction with the appended drawings. To the extent that the figures illustrate diagrams of the functional blocks of various embodiments, the functional blocks are not necessarily indicative of the division between hardware circuitry. Thus, for example, one or more of the functional blocks (e.g., processors, controllers or memories) may be implemented in a single piece of hardware (e.g., a general purpose signal processor or random access memory, hard disk, or the like) or multiple pieces of hardware. Similarly, the programs may be stand alone programs, may be incorporated as subroutines in an operating system, may be functions in an installed software package, and the like. It should be understood that the various embodiments are not limited to the arrangements and instrumentality shown in the drawings. As used herein, an element or step recited in the singular and proceeded with the word “a” or “an” should be understood as not excluding plural of said elements or steps, unless such exclusion is explicitly stated. Furthermore, references to “one embodiment” are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. Moreover, unless explicitly stated to the contrary, embodiments “comprising” or “having” an element or a plurality of elements having a particular property may include additional such elements not having that property. Various embodiments provide a system and method for collimation in diagnostic imaging systems, such as a Nuclear Medicine (NM) imaging system. For example, a collimator arrangement may be provided for use in a Single Photon Emission Computed Tomography (SPECT) imaging system. The collimator arrangement is adaptive or dynamic such that the field of view is adjustable for different patients and organs to be imaged. By practicing at least one embodiment, and at least one technical effect is that enhanced or optimized imaging can be provided. Additionally, by practicing at least one embodiment, a conventional Sodium Iodide (NaI) SPECT camera can be used for organ specific imaging with improved performance. Some embodiments provide a segmented parallel-hole collimator that includes adjustable collimator segments. For example, the collimator segments are adjustable to swivel about an axis parallel to the axis of rotation of the detectors of the SPECT system. Alternatively, collimator segments may swivel about an axis normal to the axis of rotation of the detectors of the SPECT system. An NM imaging system 20 may be provided as illustrated in FIG. 1 having an NM camera configured as a SPECT detector 22. It should be noted that the various embodiments are not limited to the NM imaging system 20 having a single detector 22 operable to perform SPECT imaging. For example, the NM imaging system 20 optionally may include one or more additional detectors 22 (an additional detector 22 is illustrated in dashed lines) such that a pair of detectors 22 is provided having a central opening 24 therethrough. An object, such as a patient 26, is positioned in proximity to the one or more detectors 22 for imaging. It should be noted that number of detectors 22 may be greater than two, for example three or more. In a multi-detector camera, the position of the detectors 22 may be substantially at 90 degrees to each other as illustrated in FIG. 1, or in different configurations as known in the art. It also should be noted that in a multi-detector camera configuration, some of the collimators may optionally be a standard collimator, for example a parallel hole collimator or a standard fan-beam collimator, or a cone-beam collimator, while at least one of the collimators is a segmented collimator according to one or more of the various embodiments. Alternatively, all of the collimators may be segmented collimators according to one or more of the various embodiments. The detectors 22 may be pixelated detectors that may operate, for example, in an event counting mode. The pixelated detectors 22 may be configured to acquire SPECT image data. The detectors 22 may be formed from different materials, particularly semiconductor materials, such as cadmium zinc telluride (CdZnTe), often referred to as CZT, cadmium telluride (CdTe), and silicon (Si), among others. In some embodiments, a plurality of detector modules are provided, each having a plurality of pixels. In other embodiments, the detector 22 may be made of a scintillation crystal such as NaI coupled to an array of Photo-Multiplier Tubes (PMTs). However, it should be noted that the various embodiments are not limited to a particular type or configuration of detectors, and any suitable imaging detector may be used. The detectors 22 are fitted with (e.g., have coupled thereto) collimators 28 that include a plurality of adjustable segments 30, which may be adjusted independently, in groups or all together. For example, four adjustable segments 30 are illustrated that define four independently and individually movable portions that can be used to adjust the field of view of the respective detector 22 as described in more detail herein. The detectors 22 may be provided in different configurations, for example, in single planar imaging mode (illustrated in FIG. 1), a two detector 22 “L” mode configuration (illustrated in FIG. 1 with the dashed line detector 22), an “H” mode configuration, or a three headed camera, among others. Additionally, a gantry (not shown) supporting the detectors 22 may be configured in different shapes, for example, as a “C” and the detectors 22 may be arranged in different configurations, for example, in an “H” or “L” arrangement. The imaging system 20 also includes a collimator/detector controller 32 that operates to control the movement of the collimators 28 and/or the detectors 22. For example, the collimator/detector controller 32 may control movement of the detectors 22, such as to rotate the detectors 22 around a patient, and which may also include moving the detectors closer or farther from the patient 26 and pivoting the detectors 22. The collimator/detector controller 32 may also control the movement of the adjustable segments 30 of the collimators 28, such that the segments 30 are moved individually or in groups. Thus, the collimator/detector controller 32 may also control movement of each of the segments 30, separate from the movement of the entire collimator 28. For example, the collimator/detector controller 32 may control pivoting movement of the segments 30 or the entire collimator 28. It should be noted that the collimator/detector controller 32 may be a single unit controlling movement of both the collimators 28 and the detectors 22, or may be separate units. The imaging system 20 also includes an image reconstruction module 34 configured to generate images from acquired image information 36 received from the detectors 22. For example, the image reconstruction module 34 may operate using NM image reconstruction techniques, such as SPECT image reconstruction techniques to generate SPECT images of the patient 26, which may include an object of interest, such as the heart 38 of the patient. In some embodiments, the reconstruction of the image information 36 is performed using an appropriate system matrix in an iterative reconstruction calculation. In an exemplary embodiment, the reconstruction process treats data from every strip/detector/gantry angle combination as a separate projection, and computes the probability of image voxels being “seen” by this combination. These determined probabilities are then used to perform an iterative reconstruction, such as using a SPECT iterative construction method. Other methods of reconstructing complex datasets of emission imaging also may be used. For example, reconstruction methods disclosed in U.S. Published Patent Application 20080011954A1 entitled “Apparatus and methods for processing imaging data from multiple detectors”, and other references disclosed therein may be used for reconstruction of data acquired by the various embodiments. Variations and modifications to the various embodiments are contemplated. For example, in a dual headed system, namely one with two detectors 22, one detector 22 may include the collimator 28 with the movable segments 30 while the other detector 22 includes a parallel hole collimator with non-moving segments or a single segment. In this embodiment, the detector 22 with the non-moving parallel hole collimator can obtain information for the entire FOV, while the detector 22 with the collimator 28 with the movable segments 30 focuses on a smaller region of interest (ROI) to provide higher quality information (e.g., more accurate photon counting). Accordingly, the collimator 28 with the movable segments 30 provides a virtual fanbeam that can focus on a smaller ROI. The image reconstruction module 34 may be implemented in connection with or on a processor 40 (e.g., workstation) that is coupled to the imaging system 20. Optionally, the image reconstruction module 34 may be implemented as a module or device that is coupled to or installed in the processor 40. The image information 36 received by the processor 40 may be stored for a short term (e.g., during processing) or for a long term (e.g., for later offline retrieval) in a memory 42. The memory 42 may be any type of data storage device, which may also store databases of information. The memory 42 may be separate from or form part of the processor 40. A user input 44, which may include a user interface selection device, such as a computer mouse, trackball and/or keyboard is also provided to receive a user input, such as to change a position of the movable segments 30. Thus, during operation, the output from the detectors 22, which may include the image information 36, such as projection data from a plurality of segment/detector/gantry angles is transmitted to the processor 40 and the image reconstruction module 34 for reconstruction and formation of one or more images. As illustrated in FIG. 2, the collimator 28 may include four adjustable segments 30 (S1-S4), with each being movable. The movement of the segments 30 may include swiveling movement as illustrated by the M arrows. In some embodiments, the movable segments 30 move independently or together or in sub-groups. Moreover, the angle of the holes 50 in each of the segments 30 may be different with each directed towards a ROI. However, two or more of the segments 30 may have segments 30 angled inwardly (toward the middle of the detector 22) to the same degree. For example, segments S1 and S4 may be angled the same while segments S2 and S3 are angled the same, such as six degrees and four degrees, respectively, as illustrated in FIG. 3. Thus, the holes 50 may define different projection angles in the different segments 30. It should be noted that the rectangular shape of the holes 50 in FIG. 2 is for illustration only, and other shapes, for example hexagonal or round collimator bores may be used. Additionally, it should be noted that the segments 30 need not be shaped as strips and may be arranged in a two-dimensional configuration. For example, a 3×3 array of 9 segments 30 may be used. Further, some segments 30 may be wedge shaped, have a curved outline, or may be provided in different shapes. It should be noted that the segments 30 and holes 50 may be formed from any suitable collimator material, for example, lead or tungsten. It also should be noted that different segments 30 may be formed having different parameters such as bore size, shape, angulations and length. The segments 30 may be moved using any suitable driving mechanism such that the segments 30 move either independently or together to adjust the field of view of the detector 22. For example, as illustrated in FIG. 4, a drive arrangement 58 having a gear arrangement 60 may be provided in connection with each of the segments 30. Each gear arrangement 60 may be separately powered by a corresponding motor 62 (as illustrated) or optionally by a single common motor. The motor 62 and gear arrangement 60 are controlled by a collimator controller 64, which may form part of the collimator/detector controller 32. Thus, in various embodiments, the movement of the segments 30 may be driven by one or more motors 62 via the gear arrangements 60, which may be, for example, a rack/pinion, belt, screw and nut, or crankshaft/drive gear arrangement, among others. The segments 30 may swivel (e.g., pivot) about a pivot axis, with the pivot axis for each of the plurality of segments 30 being parallel. It should be noted that although the holes 50 are illustrated as defining generally parallel holes 52, namely openings through the collimator 28, the various embodiments are not limited to parallel hole 52 arrangements. For example, the holes 50 may define a fanbeam arrangement wherein the holes 52 are not parallel, but have a different relative angle and/or different focal lengths. Additionally, the holes 52 in some embodiments may have a degree of pre-slanting or may be perpendicular to the surface of the detector 22. For example, in the pre-slanting arrangements, the holes 50 may be slanted such that the holes 50 are pre-focused to a typical point of offset. Thus, the collimator 28 formed in accordance with various embodiments may have different configurations. The collimator 28, thus, may define one of a parallel, slant, diverging fanbeam or converging fanbeam arrangement, among others. In some embodiments, the holes 50 define a slant-hole collimator 28. Modifications and variations are contemplated to the various embodiments. For example, each of the segments 30 may different sizes of holes 52. In some embodiments, the holes 50 that are usually further from the ROI (near the edge of the detector 22) may be longer holes to compensate for the greater distance to the ROI (at the expense of sensitivity, but maintaining some resolution). In other embodiments, the segments 30 may be converging or diverging along the axis rotation of the imaging system 20 (shown in FIG. 1), which effectively reduces or increases, respectively, the FOV in the direction along the axis of rotation and increases the sensitivity. When the FOV is known to be quite small (e.g., in the heart) this additional convergence can provide additional improvement in sensitivity. In still other embodiments, the holes 50 in each of the segments 30 may be angled different from one segment 30 to another along the short or long axis of the segment 30. Shielding also may be provided in the region between the collimator segments 30 (or behind the segments) to reduce or prevent high count rates caused by radiation penetrating through the gap between adjacent segments 30. As illustrated in FIG. 5, a generally planar shielding member 70 may be provided between adjacent segments 30. In some embodiments, the collimator segments 30 have curved or rounded ends as shown in FIG. 6 to provide for motion of the segments 30. In this embodiment, a complementary shielding member 72 is provided between adjacent segments 30. For example, the ends of the segments 30 may be convex, while the shielding member 72 has a concave middle portion in an hour-glass shape or configuration. It should be noted that the amount of spacing between the segments 30 may be varied based on the amount of rotation desired or needed for the segments 30. It also should be noted that the shielding members 70 and 72 may be formed from any type of collimator or photon blocking material, such as lead or tungsten. In embodiments wherein one or more of the segments 30 are stationary, the shielding members 70 and/or 72 may be removed or not provided and the segments 30 configured to fit closely or snugly to (e.g., abut) each other, to reduce or minimize radiation leaks. Alternatively, radiation leaks may be reduced or prevented by applying a material with a high stopping power such as an epoxy glue mixed with lead or tungsten powder. In operation, each of the segments 30 and the corresponding holes 50 may be in a fixed position for the entire exam, with only the detector 22 (or detectors 22) moving around (rotating around) the patient 26 (both shown in FIG. 1). In other embodiments, the segments 30 may move to a new position for every detector position, such as to keep the FOV “in focus”. In still other embodiments, the segments 30 may move to multiple positions for each position of the detector so as to “sweep” a larger area of the FOV. Thus, the segments 30 can swivel or rotate through an angle range, for example, +/−10 degrees, which allows the FOV to move. The amount of movement of the FOV may be changed based on the amount of angular motion provided and the distance from the collimator 28 to the FOV. Using the various embodiments, both the size and location of the FOV may be changed. Additionally, the detectors 22 may be tilted to provide an additional level of adjustment. Image data may be acquired by one or more different movements in accordance with various embodiments. For example, collimator swivel, detector tilt and/or gantry rotation may be used separately or in combination in accordance with various embodiments. It should be noted that the positioning of the segments 30 can be automatic based on prior information (e.g., CT information), emission information (adapting during the scan), atlas-based information (e.g., all hearts are roughly in a particular location), user interaction (e.g., concentration defined at a particular location), information based on the reconstructed image (another form of adaptive), among other information or factors. In some exemplary embodiments, the direction of at least one of the segments 30 is dynamically adjusted during data acquisition based on the acquired data. In some embodiments, segment direction may be automatically adjusted such that the FOV defined by the segment 30 is centered on an organ-of-interest (OOI). For example, segment direction may be adjusted to increase or maximize the count rate in the FOV defined by the segment 30. In some embodiments, the segment 30 may perform slow undulation to determine the angle of highest count rate. Alternatively, image processing methods or software may be used for determining the center of the OOI and to aim the segment 30 towards the OOI. In other embodiments, a 3D image may be reconstructed using partial data acquired during part of the acquisition. The location of the OOI is determined from the reconstruction and is used for aiming at least some of the segments 30 thereafter, which may be used, for example, in a multi-rotation imaging. Different types of movement will now be described. As shown in FIG. 7, each of the segments 30 is stationary and generally parallel to the front surface of the detector 22. In this embodiment, each segment 30 may be independently swiveled (e.g., rotated or pivoted) to focus the FOV 78 of each on an ROI 80. The holes 50 in different ones of the segments 30 may be angled differently such that each set of holes 50 corresponding to different segments 30 are focused on the ROI 80 by tilting each set of segments 30 differently. It should be noted that at least two sets of the different segments 30 (e.g., segments 30a and 28d, and 28b and 28c) may be tilted the same amount. As another example, the detector 22 may be tilted as shown in FIG. 8. In this embodiment, the holes 50 of the segments 30 may also be angled as described above. The detector 22 is tilted, for example, relative to an axis of rotation such that a different portion of the ROI may be imaged and not just the center of rotation. The detector 22 may be tilted using any suitable drive mechanism and as described in more detail herein. As still another example, the individual segments 30 may be tilted. For example, as illustrated in FIG. 9, one or more of the segments 30 may be tilted such that the segments are no longer generally parallel to the front surface of the detector. In this embodiment, the holes 50 of the segments 30 may also be angled as described above. The segments 30 may be tilted using any suitable drive mechanism and as described in more detail herein. It should be noted that although the axis of rotation of each of the segments 30 is illustrated at a middle of the each of the segments 30, the axis of rotation may be changed for one or more of the segments 30. For example, axis of rotation can be offset, particularly at the end segments 30, such that the segments 30 rotate about a point closer to an end, such as an inner end (closer to the middle of the detector 22) of the segment 30. Using this segment swivel movement, the sensitivity may cover or “paint” a larger area of the FOV such that image data is acquired from a larger overall region. As yet another example, the detector 22 may be moved as illustrated in FIG. 10. For example, the detector may rotate around a gantry (not shown) and about the ROI 80 (such as rotated relative to the gantry position illustrated in FIG. 8). Again, in this embodiment, the holes 50 of the segments 30 may also be angled as described above. It should be noted the one movement is not exclusive of other movements. Accordingly, one or more of the movements described herein may be performed simultaneously, concurrently, consecutively, or otherwise. Accordingly, as shown in FIG. 11, each of the segments 50 (and also the holes 50 of each segment 30) may be provided at different angles to provide a near FOV. A far FOV may be provided as shown in FIG. 12, wherein the segments 30 are not tilted and are parallel to the front surface of the detector 22. It should be noted that an even farther FOV may be provided if the segments 30 are outwardly tilted (opposite to the direction indicated in FIG. 11). It should be noted that although an even number of segments 30 are illustrated, namely four, a different number, such as an odd number of segments may be provided. For example, as shown in FIG. 13, five segments 30a-e may be provided. In this embodiment, the center segment 30e may have a parallel hole positioning or arrangement with no slant, while the outer segments 30a-d have holes 50 that are angled as described herein. Other variations and modifications may be provided, such as moving some, but not all of the segments 30. For example, as shown in FIG. 14, only one segment 30a may be tilted relative to the front surface of the detector 22, with the other segments 30b-d remaining parallel to the front face. In this embodiment, the holes 50 of the segments 30 may also be angled as described above. Thus, an asymmetric arrangement may be provided, for example, which may be used for brain imaging. A dedicated collimator also may be constructed with asymmetric fixed segment angulations for specific imaging applications such as brain imaging. In operation, prior to acquiring or during acquiring an image of a structure of interest, the detector(s) 22, collimators 28, segments 30 and/or other members may be adjusted to focus the FOV on a structure or object of interest. Additionally, a patient table or gantry also may be moved. With a collimator with fixed segments, the patient table may be moved during acquisition such that the OOI is adequately or sufficiently imaged by the plurality of segments. Image data is then acquired by each of the detectors 22, which may be combined and reconstructed into a composite image that may comprise two-dimensional (2D) images, a three-dimensional (3D) volume or a 3D volume over time (4D). In addition to the collimator movement, the detectors 22 may be moved to also adjust the effective field of view for one or more of the detectors 22, such that the FOV is reoriented or decreased/increased, such as by pivoting one or more of the detectors 22, translating one or more of the detectors 22 and/or adjusting one or more of the collimators 28 as described herein. Referring specifically to FIG. 15, movement of one of the detectors 22 is illustrated, for example, to change the direction from which the respective detecting face of the detectors 22 senses gamma emissions or radiation separate from the movement of the collimator 28. It should be noted that in this embodiment, the collimator 28 may move as described in more detail herein. The one or more detectors 22 may be mounted on a pivot 106 that is at the end of a support member 108 (e.g., a leg) mounted to a support structure 90 of an image detector, for example, of a gamma detector. Other pivoting mechanisms may be used. In this embodiment, the collimator/detector controller 32 includes a pivot controller 100 that can command the pivot 106 to move along arrow A, along arrow B (which is orthogonal to arrow A), or any position between the arrows A and B. The pivoting motion may be used together with one or more of the other movements as described herein. A pivot range 108 for each of the detectors 22 may be provided. For example, when imaging a structure that is larger than the actual FOV of the detectors 22 or to focus on a different object, the pivot range 108 may have a start point 110 at one end wherein the FOV images one outer edge of the structure or is pointed toward a particular object. Optionally, a predefined amount of surrounding tissue may be imaged. An end point 112 of the pivot range 108 may be set to image an opposite outer edge of the structure as well as a predefined amount of surrounding tissue. Therefore, a pivot range 108 may be defined for each of the detectors 22 that may be specific to a particular scan. Alternatively, one or more of the detectors 22 may be moved through a fixed, predetermined pivot range 108. A rate or speed of pivoting may also be predetermined, set by an operator, or determined based on the anatomy being scanned, size of the structure, level of radiation detected, and the like. It should be noted that rate of pivoting need not be constant throughout the pivot range 108, may be different for a different axis of pivoting, and may be different for different imaging detectors or throughout the duration of the acquisition. For example, the rate of pivoting may be higher during parts of the pivoting range 108 wherein the detectors 22 are aimed at the surrounding tissue. Thus, the detectors 22 collect more data from the structure of interest than from the surrounding tissue. It should be noted that the pivoting operation can take the form of a series of angular steps, wherein either the step size or the time per step (or both) can be changed to change the rate of pivoting. Additionally, alternative motion can be continuous (but with variable speed) in which case a frequent readout of the actual position of the collimator (e.g., every millisecond or every time an event is detected) is provided and the information about the collimator location is communicated along with the event for subsequent processing. Moreover, the detectors 22 may remain focused on a particular area or may be adjusted or moved. For example, the detectors 22 may acquire image data at a first position 114 corresponding to the start point 110 of the pivot range 108. The actual FOV 116 of the detectors 22 is dependent in part upon the adjustment of the collimator 28 as described herein. The detectors 22 are pivoted through the pivot range 108 along the direction of arrow A to a second position 118 corresponding to the end point 112 with an actual FOV 120. An effective FOV 122 that is larger than either of the actual FOVs 116 and 120 is formed. The detectors 22 may continuously acquire data while pivoting from the first position 114 to the second position 118. Alternatively, the detectors 22 may acquire a series of images as the pivot controller 100 moves the detectors 22 through the pivot range 108. Alternatively, the pivot controller 100 may move the detectors 22 to one or more predetermined positions within the pivot range 108, and the detectors 22 acquire images at each of the one or more positions. Although the example is illustrated in a single dimension, it should be understood that the effective field of view may be increased by pivoting the detectors 22 or collimators 28 in other directions. The support member 108 may be commanded by a radius controller 102 to move the detectors 22 toward and away from a patient along arrow C. A distance 124 may thus be changed to increase or decrease the distance from the patient. The support member 108 may be piston driven, spring loaded, chain driven, or any other type of actuator. Alternatively, the support member 108 may be mounted on a portion (not shown) of the gantry, and thus the portion may also be driven in the direction of arrow C. The radius may be changed while acquiring data or between acquisitions, and may be used in combination with other motions. Anti-collision software and/or sensors (not shown) may also be used to ensure that the patient does not collide with the detectors 22. In various embodiments, the adjustable collimators 28 are also provided as described herein and shown in FIG. 16. As illustrated, the radius controller 102 may move each of the detectors 22 closer to and further from a surface of the patient, and the pivot controller 100 may move the detectors 22 axially with respect to the patient 76. Additionally, in this embodiment, the collimator controller 104 may adjust a position of the adjustable collimator 28, which may be a collimator with adjustable segments 30 as described in more detail herein. By changing the geometry of the adjustable collimators 28, the effective FOV may be changed or increased to be greater than the actual FOV. In a configuration wherein the collimators 28 include a plurality of segments 30, the collimator controller 104 can move all or a sub-set of the segments 30 through a range of motion. The collimator controller 104 may move the segments 30 predetermined distances, stop, and then acquire an image before moving the segments 30 to a next imaging position. Alternatively, the collimator controller 104 may move the segments 30 in a smooth sweeping motion, acquiring a single image across the effective FOV. The detectors 22 with adjustable collimators 28 of the various embodiments may be provided as part of different types of imaging systems, for example, NM imaging systems such as SPECT imaging systems having different detector configurations. For example, FIG. 17 is a perspective view of an exemplary embodiment of a medical imaging system 210 constructed in accordance with various embodiments, which in this embodiment is a SPECT imaging system. The system 210 includes an integrated gantry 212 that further includes a rotor 214 oriented about a gantry central bore 232. The rotor 214 is configured to support one or more NM cameras 218 (two cameras 218 are shown). The NM cameras 218 may be provided similar to the detectors 22 with the adjustable collimators 28. It should be noted that the detectors, for example, the detectors 22 or NM cameras 218 are generally equipped with interchangeable collimators. For example, the detector 22 or NM camera 218 is supplied with a plurality of collimators (or collimator pairs for a dual head cameras) wherein each collimator type is used for one type or a few different types of medical imaging procedures. According to some embodiments, at least one fixed-segment collimator is supplied with the detector 22 or NM camera 218 to be used for imaging an OOI having a size smaller than the entire FOV of the detector 22 or NM camera 218 when fitted with a standard parallel hole collimator. In other embodiments, a set of fixed-segment collimators is supplied with the detector 22 or NM camera 218. In still other embodiments, a plurality of different fixed-segment collimators or fixed-segment collimator sets is provided. In some embodiments, the fixed-segment collimator or collimators are used for applications where more expensive fan-beam or cone beam collimators can be used. In operation, in some embodiments, at least one of the standard collimators is replaced with a collimator according to one of the various embodiments. In various embodiments, the cameras 218 may be formed from pixelated detectors or a single detector material (e.g., NaI). The rotors 214 are further configured to rotate axially about an examination axis 219. A patient table 220 may include a bed 222 slidingly coupled to a bed support system 224, which may be coupled directly to a floor or may be coupled to the gantry 212 through a base 226 coupled to the gantry 212. The bed 222 may include a stretcher 228 slidingly coupled to an upper surface 230 of the bed 222. The patient table 220 is configured to facilitate ingress and egress of a patient (not shown) into an examination position that is substantially aligned with examination axis 219. During an imaging scan, the patient table 220 may be controlled to move the bed 222 and/or stretcher 228 axially into and out of a bore 232. The operation and control of the imaging system 200 may be performed in any suitable manner. It should be noted that the various embodiments may be implemented in connection with imaging systems that include rotating gantries or stationary gantries. Thus, various embodiments provide synthetic fanbeam or adaptive fanbeam collimation that allows adjustment of both the location and size of the FOV of an imaging detector. Additionally, various embodiments provide a method 300 as illustrated in FIG. 18 for collimating a detector of an imaging system, such as an NM imaging system. The method 300 includes configuring at 302 a segmented collimator to move a plurality segments (independently or in groups) such that, for example, synthetic or adaptive fanbeam collimation is provided. In particular, a plurality of segments of a collimator is configured to move as described in more detail herein. For example, each of the segments may pivot or swivel about a pivot axis, with the pivot axis for each of the plurality of segments being parallel. Thereafter, the segmented collimator is coupled to an imaging detector of an imaging system at 304. For example, the segmented collimator may be coupled to a front surface of one or more NaI SPECT gamma cameras. With the segmented collimator coupled to the imaging detector, a controller is provided at 306 to move the plurality of segments to adjust a location and/or size of the detector FOV. The movement may also include movement of the detector as described herein. The control of the movement of the segmented collimator may be based on different types of information, such as a priori information or current scan acquisition information. Additionally, this information may be used to control other components of the imaging system, such as movement of the imaging detector (e.g., rotation of the imaging detector or tilting of the imaging detector) or movement of the patient table. In various embodiments, the control of movement may be based on a priori information to determine or define a scan pattern for scanning an ROI or OOI. For example, prior information about general anatomy for a particular organ, the specific anatomy of a patient, prior scan data for the patient, or other data, may be used to determine or define movement of the segmented collimator. The movement may include a defined scan pattern based on the prior information such that an optimized scan of a particular organ is performed. Additionally the control of movement may be based on current scan acquisition information, such that movement is controlled on-the-fly. In various embodiments, based on acquired scan data, which may include determining the location of an OOI after an initial scanning period, the movement of the segmented collimator, such as the defined scan pattern, may be changed to optimize scanning for the OOI of the patient. For example, adjustments in the scan pattern may be made based on acquired raw data counts (e.g., emission photon counts) or an initial image reconstruction to provide for the same number of counts to be acquired from each scan angle, a predetermined amount of counts (e.g., 80% of the counts) to be acquired from an OOI determined from the initial image reconstruction, or other desired or required imaging or scanning characteristics or operating parameters. It should be noted that providing the controller may include providing hardware, software or a combination thereof to control the segmented collimator. The hardware and/or software may be integrated as part of the imaging system or provided separately therefrom, for example, as part of an upgrade installation. In other embodiments, an assembly is provided such that the assembly may be mounted or unmounted from the imaging system such that all of the parts (e.g., motors, segments, etc.) can be attached to the front of the imaging cameras and removed when not needed. Accordingly, a collimator assembly formed in accordance with various embodiments may be installed and removed from the imaging system. The various embodiments and/or components, for example, the modules, or components and controllers therein, also may be implemented as part of one or more computers or processors. The computer or processor may include a computing device, an input device, a display unit and an interface, for example, for accessing the Internet. The computer or processor may include a microprocessor. The microprocessor may be connected to a communication bus. The computer or processor may also include a memory. The memory may include Random Access Memory (RAM) and Read Only Memory (ROM). The computer or processor further may include a storage device, which may be a hard disk drive or a removable storage drive such as an optical disk drive, solid state disk drive (e.g., flash RAM), and the like. The storage device may also be other similar means for loading computer programs or other instructions into the computer or processor. As used herein, the term “computer” or “module” may include any processor-based or microprocessor-based system including systems using microcontrollers, reduced instruction set computers (RISC), application specific integrated circuits (ASICs), logic circuits, and any other circuit or processor capable of executing the functions described herein. The above examples are exemplary only, and are thus not intended to limit in any way the definition and/or meaning of the term “computer”. The computer or processor executes a set of instructions that are stored in one or more storage elements, in order to process input data. The storage elements may also store data or other information as desired or needed. The storage element may be in the form of an information source or a physical memory element within a processing machine. The set of instructions may include various commands that instruct the computer or processor as a processing machine to perform specific operations such as the methods and processes of the various embodiments of the invention. The set of instructions may be in the form of a software program, which may form part of a tangible non-transitory computer readable medium or media. The software may be in various forms such as system software or application software. Further, the software may be in the form of a collection of separate programs or modules, a program module within a larger program or a portion of a program module. The software also may include modular programming in the form of object-oriented programming. The processing of input data by the processing machine may be in response to operator commands, or in response to results of previous processing, or in response to a request made by another processing machine. As used herein, the terms “software” and “firmware” are interchangeable, and include any computer program stored in memory for execution by a computer, including RAM memory, ROM memory, EPROM memory, EEPROM memory, and non-volatile RAM (NVRAM) memory. The above memory types are exemplary only, and are thus not limiting as to the types of memory usable for storage of a computer program. It is to be understood that the above description is intended to be illustrative, and not restrictive. For example, the above-described embodiments (and/or aspects thereof) may be used in combination with each other. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the various embodiments of the invention without departing from their scope. While the dimensions and types of materials described herein are intended to define the parameters of the various embodiments of the invention, the embodiments are by no means limiting and are exemplary embodiments. Many other embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the various embodiments of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. In the appended claims, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.” Moreover, in the following claims, the terms “first,” “second,” and “third,” etc. are used merely as labels, and are not intended to impose numerical requirements on their objects. Further, the limitations of the following claims are not written in means-plus-function format and are not intended to be interpreted based on 35 U.S.C. §112, sixth paragraph, unless and until such claim limitations expressly use the phrase “means for” followed by a statement of function void of further structure. This written description uses examples to disclose the various embodiments of the invention, including the best mode, and also to enable any person skilled in the art to practice the various embodiments of the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the various embodiments of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if the examples have structural elements that do not differ from the literal language of the claims, or if the examples include equivalent structural elements with insubstantial differences from the literal languages of the claims.
058621954	claims	1. A transport, storage, monitoring, and retrieval system for spent nuclear fuel storage canisters, comprising three or more rows of trackage, dry pools between rows of trackage for canister storage, a canister transporter, transporter tracks for carrying the transporter adjacent to or between pools, bridge crane carrying tracks, the transporter tracks being between a set of bridge crane carrying tracks, and the dry-pools being between the bridge crane carrying tracks. 2. The system of claim 1 and further having the dry-pools being equipped with an integral cooling air ventilation manifold system bringing in outside air into the dry-pools under the stored canisters. 3. The system of claim 2 having the dry-pools being constructed water tight such that the pools can be filled with water for shielding and cooling. 4. The system of claim 1 and further having an access corridor shielded for radiation, a lifting transport conveyance with an associated elevation chase to transfer a canister between a shielded transport system and storage locations at the floor of the dry-pool, the elevation chase limiting a potential dropping of the canister should it release from the lifting transport. 5. The system of claim 4 and further having strategically placed vertical radiation shielding preventing radiation from exiting the storage area. 6. The system of claim 5 and further having a radiation shield roof. 7. The system of claim 1 having the bridge crane tracks being capable of carrying a transporter. 8. The system of claim 7 having one or more bridge cranes, each spanning over one or more rows of trackage. 9. The system of claim 1 having a system of RR-transfer tables such that a bridge crane may be moved so it can engage more than one set of off loading tracks enabling more than one track capable for off-loading canisters to more than one dry-pool. 10. The system of claim 1 having seismic bracing for supporting vertically standing canister casks. 11. The system of claim 1 where the system is operationally controlled from an off-site control station. 12. The system of claim 1 where the dry-pools are themselves casks for the storage to one or more canisters. 13. The system of claim 8 having the transporter comprise canister carrying transport cars which can be off-loaded or loaded under a bridge crane. 14. The system of claim 1 wherein each of said dry-pools include a dry radiation shielding material.
	abstract	An apparatus comprising a variable aperture for controlling electromagnetic radiation and related systems and methods are described. In one aspect, a variable aperture to control electromagnetic radiation comprises a first substrate, a second substrate, an attenuation fluid, at least one charging electrode, and at least one displacing electrode. The second substrate is located opposite the first substrate and spaced apart from the first substrate to form a gap between the first substrate and the second substrate. The attenuation fluid is located in the gap and configured to absorb electromagnetic radiation of a predetermined wavelength. The at least one charging electrode is in electrical contact with the attentional fluid. The at least one displacing electrode is located on a surface of the first substrate facing the gap or on a surface of the second substrate facing the gap.
047643366	description	DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The de-activation pool of a nuclear station shown in FIG. 4 comprises a fluidtight inner covering 1 formed by metal sheets, for example of stainless steel, supported in a manner which will be described in more detail hereinafter, by a structure comprising a grid system of beams 2. The walls of this pool have a structure similar to that diagrammatically illustrated in FIG. 1. In the latter, the wall has in succession,from the exterior toward the interior of the pool, an outer part 3 formed from a hard and dense material such as, for example, concrete and defining a roughly planar inner surface, an inner part 4 formed from a hardenable material such as, for example, concrete poured into a space between said outer part 3 and an embedded lining comprising slabs 5 for example of fibrocement disposed in adjoining relation between the beams 2 so as to define with the latter a planar inner surface adapted to receive the metal sheets 6 of the fluidtight inner covering of the pool. The beams 2 are each fixed, before the pouring of the corresponding inner part, to the outer part of the wall by means of L-shaped fixing lugs 7 disposed on each side of the beam, preferably in an alternating arrangement, one of their branches being welded to the beam and the other being fixed, for example, by means of a bolt 8 screwed into said outer part 3 of the wall. These lugs moreover permit an adjustment of the distance of the beams from the outer part of the wall by compensating for unevennesses of its rough inner surface. Further, a spacer block 9, for example of rigid plastics material, is provided in contact with each fixing lug 7 on which it is maintained by means of a foil 10 which extends under the lug and the corresponding block. These blocks 9 each have a planar surface facing the interior of the pool and cooperate with a longitudinal flange 11 of the neighbouring beam extending in facing relation to and a distance from said planar surfaces of the blocks 9 so that a peripheral part 12 of reduced thickness of the slabs 5 can be inserted between the blocks and said flange of the neighbouring beam 2. The part 12 of reduced thickness of the slabs 5 is defined by a shoulder 13 whose thickness corresponds to that of the flanges 11 and facing toward the interior of the pool so that the inner surfaces of the slabs 5 and the beams 3 are contained in a common plane. The metal sheets 6 of the fluidtight inner covering of the pool bear on said inner surfaces of the slabs 5 of the lost coffering and of the beams 2. In this respect, each beam 2 defines a planar bearing surface 14 at the level of which two metal sheets 6 are supported and interconnected by one of their edges by a weld bead 15 which extends longitudinally along the beam 2 and roughly in the middle of the latter, the weld bead being connected to the bearing surface 14 of said beam 2. According to a first embodiment of the invention, the beam 2 illustrated in FIG. 1 comprises a first section element 16 and a second section element 17 each respectively having a cross-section roughly in the shape of a U and an omega the branches of which are roughly parallel to each other and of the same length. The first section element 16, incorporated in the concrete of the inner part of the corresponding wall, forms the outer part of the beam on which the lugs 7 are fixed and opens toward the interior of the pool. The second section element 17 is substantially narrower than the first and is fixed by the edge of each of its branches 18 to the bottom of the latter and thus defines three longitudinal channels. An inspection channel 20 having a closed cross-section, adapted to receive a device for the radiography of the welds of the sheets 6, is formed between the branches 18 of the second section element l7,and two draining channels 21 having a cross-section which is open toward the interior of the pool are formed on each side of the inspection channel 20 between said branches 18 of the second section element and the branches 22 of the first element 16. Further, the second section element 17 is fixed by the welding of two flanges 23 provided at the end of each of its branches 18, to the bottom 19 of the first section element 16, said flanges 23 extending outside the inspection channel 20. Further, the bearing surface 14 for the sheets 6 on the beams 2 is formed at the region of each of the latter by the surface of the intermediate part of the second section element 17 facing toward the interior of the pool, this bearing surface 14 being contained in the same plane as the inner surface of the flanges 11 provided at the end of each of the branches 22 of the first section element 16. This inner surface of the flanges 11 thus advantageously completes the bearing surface 14 by jointly supporting the sheets with the latter. With reference again to FIG. 4, it can be seen that access may be had to the vertical beams 2 from above the pool and that each of their lower endsis connected to a respective alignment of beams 2 disposed horizontally in the bottom of the pool. This connection may be achieved, as shown in FIG. 4, by means of a hollow T-shaped connector 26 which permits, on one hand, the communication between the channels of each vertical beam and those of the horizontally aligned corresponding beams and, on the other hand, the communication between the channels of the latter and a beam which extends outside the pool if this is possible. This connection may also be ensured by a bent beam, having a cross-section similar to that of the beam 2 described hereinbefore and bent longitudinally in an arc of a circle so that its end portions make a right angle therebetween. Further, in the region of each crossing of two alignments of beams 2, the latter are connected by means of a hollow X-shaped connector 27 so as to permit the communication between the channels of the beams which cross each other. This arrangement of the structure which supports the metal sheets of the covering 1 inside the pool, in a network of channels accessible from the exterior through the upper edges and optionally through the bottom of the pool, permits the introduction of a radiography device throughout the length of the inspection channels 20 and the piping for the leakage liquid drained by the beams, throughout the network. By way of a modification, the structure of beams may, of course, form a plurality of networks which are independent from each other. Such a beam 2 according to the invention permits, on one hand, radiographing the whole of the weld disposed on its bearing surface by means of the longitudinal inspection channel 20 having a closed cross-section, capable of receiving a suitable device, and, on the other hand, ensuring the draining of 100% of the leakages in the region of this weld owing to the presence of a longitudinal draining channel 21 provided on each side of the latter. Moreover, this beam perfectly performs its supporting function for the sheets 6 by providing a flat bearing surface 14 on which the latter may bear, and transmit to the concrete of the corresponding wall, through the beam, the pressure forces exerted by the water of the pool and the shear forces due to thermal stresses. Further, the presence of the flanges 11 of the first section element 16 advantageously increases the area of contact of the beam with the sheets while avoiding at the same time the piercing of the latter which would occur if they were directly applied against the end of straight branches. The parts of the second embodiment of the invention shown in FIGS. 2 and 3, which are distinguished from those of the first embodiment illustrated in FIG. 1, will now be described, the similar parts of these two embodiments carrying the same reference characters. The beam 2a shown in FIG. 2 is obtained directly by a cold drawing operation. This beam 2a differs from that previously described in that the second section element 17 is replaced by a second section element l7a which has in cross-section roughly the shape of an L and is in one piece with the first section element 17. A branch 24 of this second section element l7a is rigid at one end with the bottom 19 of the first section element 16 and extends in facing relation to and in the vicinity of a branch 22 of the latter so as to define therewith a longitudinal draining channel 2la having a cross section which is open toward the metal sheets 6 of the fluidtight inner covering of a de-activation pool. The other branch 25 of this L-section element extends transversely in a direction away from the draining channel 2la and defines a space between its free end and the corresponding branch 22 of the first section element 16, its surface facing toward said metal sheets 6 forming the bearing surface 14 of the latter on the beam 2a. Thus, a longitudinal inspection and draining channel 2Oa having an open cross-section and capable of receiving a device for radiographing welds, is formed between the branch 22 of the first section element 16 opposed to the draining channel 2la, and the branch 24 of the second section element l7a fixed to the first section element. By way of a modification (FIG. 3), the second section element 17a constructed separately from the first section element, includes a flange 23a which is welded to the bottom of the latter and extends in the draining channel 2la. Apart from the interest of directly obtaining a beam by a cold drawing operation, this beam 2a is advantageously narrower than the beam 2 of the first embodiment of the invention for a given width allowed for the respective visiting channel.
051174472	description	DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is characterized in that a beam deflecting means partially scans the area beyond the restricted scanning area which is determined by the structures of a photoconductive layer, an electrode and the like in spite of the corresponding scanning area within which the image quality is ensured for the camera tube in the standard broadcasting system such as an NTSC system, for example, 6.6 mm.times.8.8 mm in the case of a 2/3-inch camera tube, 9.5 mm.times.12.7 mm in the case of a 1-inch camera tube, and 15.2 mm.times.20.3 mm in the case of a 1.5-inch camera tube. In this case, it is necessary that the input image formed on the surface of the camera tube or the region of interest in the input image is within the restricted scanning area which is determined by the structure of the camera tube, and that the quality of the image obtained is suitable for practical use. FIG. 1A shows an example of the structure of the vicinity of the input surface of an electromagnetic focusing and electromagnetic deflection type (hereinunder referred to as "M--M type") 1-inch camera tube with a target ring A is used as the camera tube in FIG. 1A. The reference numeral 51 represents a glass envelope, 52 a glass face plate, 53 a transparent signal electrode layer, 54 a photoconductive layer, 55 a mesh electrode, and 56 a target ring. In this example, the restricted scanning area which is determined by the structure of the camera tube is determined not by the photoconductive layer 54 having a diameter of 20.2 mm, but by the frame of the mesh electrode 55 having a diameter of 19 mm. In this example, the diameter of the transparent signal electrode layer 53 is 21.4 mm, but in the case of a camera tube with a target pin 57 such as that shown in FIG. 1B, since the diameter of the effective transparent signal electrode layer 53 is 18.8 mm, which is smaller than the diameter of the actual photoconductive layer, due to the position of the target pin 57, the scanning area is determined by the positions of the transparent signal electrode layer 53 and the target pin 57. In the structure of the camera tube shown in FIG. 1B, the same reference numerals are provided for the elements which are the same as those shown in FIG. 1A. In FIGS. 1A and 1B, the symbol .phi. represents a diameter. FIGS. 2B and 2C show examples of a scanning area proposed in the present invention. A conventional scanning area 61 is 9.5 mm.times.12.7 mm, as shown in FIG. 2A. In the conventional scanning area 61, the scanning area A.sub.s is small. For example, if a circular image such as the image output from an X-ray II is taken into consideration, it is necessary that the circular image 62 is within the scanning area, so that the diameter of the image forming surface is 9.5 mm and the area A.sub.c thereof is 70.9 mm.sup.2. Even if the scanning area is restricted to the diameter of the mesh, namely, 19 mm, in other words, even if the maximum restricted scanning area which is determined by the structure of the camera tube is used for square scanning, the scanning domain is 13.4 mm.times.13.4 mm and is limited to 13 mm.times.13 mm in consideration of a slight margin. In this case, the diameter of the image forming surface for a circular image is 13 mm, and the area A.sub.c thereof is 132.7 mm.sup.2. On the other hand, in the present invention, a square 63 is scanned by an electron beam beyond the restricted scanning area (the range equivalent to the mesh diameter 19 mm in FIG. 2B) which is determined by the structure of the camera tube, as shown in FIG. 2B. If the circular image of the X-ray II is projected onto the maximum area which corresponds to the mesh diameter and scanned, the necessary domain for beam scanning is 19 mm.times.19 mm. However, the suitable scanning domain 63 for the beam deflecting means is 15 mm.times.15 mm to 16 mm.times.16 mm in consideration of the image quality obtained. In the following explanation, the scanning domain 63 is assumed to be 15 mm.times.15 mm (diagonal: 21.2 mm). In this case, the circle 64 (diameter: 15 mm) inscribed in the square scanning area 63 constitutes the useful image input area, and the area A.sub.c thereof is 176.7 mm.sup.2. This useful image input area is substantially the same as the useful image input area obtained in the above-described scanning area within which the image quality is ensured for a 1.5-inch camera tube and having a diameter of 15.2 mm. This fact means that a 1-inch camera tube is capable of inputting an image of substantially the same degree as a 1.5-inch camera tube does. The image forming area of a circular image obtained within the scanning area within which the image quality is ensured for a 1-inch camera tube is 70.9 mm.sup.2 in the prior art. In contrast, the image scanning area in the present invention is 176.7 mm.sup.2, which is about 2.5 times as large as that in the prior art. This means that the scanning area proposed in the present invention greatly contributes to the improvement of the resolution, the dynamic range and the signal-to-noise ratio. The above-described enlargement of the scanning area is easily achieved by increasing the output of a deflecting and amplifying system and there is almost no need to change a conventional television camera for DR. When the scanning area is enlarged to 15 mm.times.15 mm as described above, an electron beam passes a control electrode G.sub.1, an accelerating electrode G.sub.2, a focusing electrode G.sub.3 and a mesh electrode G.sub.4 (see FIG. 5) and reaches the surface of the target in an M--M type Saticon, but the electron beam does not reach the surface of the target in the vicinity of the four corners which are beyond the diameter of the mesh, namely, 19 mm, and collides against the frame of the the mesh electrode. Since a retarding electric field is generally generated between the mesh electrode and the surface of the target, the energies of the electrons which reach the surface of the target are so controlled as to become very small, namely, to make a soft landing on the surface of the target. However, the electrons which collide against the frame of the mesh electrode have a certain degree of energy when colliding, thereby emitting secondary electrons from the frame of the mesh electrode and possible breaking the electrode. To prevent this, the present invention also provides a means for controlling the voltage E.sub.c1 (see FIG. 5) applied to the control electrode G.sub.1 so as to prevent the electron beam from reaching an unnecessary area on the mesh electrode G.sub.4 or the surface of the target. The controlling method is as follows. In the scanning area 63 shown in FIG. 2B, a signal is output for controlling the voltage so as to cut the electron beam, for example, in the area s.sub.1 which is defined by the mesh electrode or the area s.sub.1 +s.sub.2 which is outside the scanning area necessary for inputting a circular image. This method is realized by preparing a two-dimensional memory with information indicating the scanning area stored therein in advance, reading the data synchronously with the scanning, as shown in FIG. 5 and controlling a switch for the voltage E.sub.c1 so as to change over between a voltage bE.sub.c1 for cutting the electron beam and a voltage aE.sub.c1 for turning on the electron beam in accordance with the output of the memory. In the case of a Saticon tube, however, according to the experiments of the present inventors, even if the electron beam collided against the frame of the mesh electrode, the mesh electrode was not broken. In this case, the means for on/off control of the electron beam is dispensed with, and an increase in the capacity of the mesh electrode current source suffices. When a television camera for DR has a multiplicity of scanning modes, a real-time DR apparatus which effectively utilizes the television camera sometimes needs to change the scanning area of the electron beam in each mode. This is easily realized either by preparing the memory with the data for controlling the voltage E.sub.c1 stored therein for each mode or by changing the contents of the memory in correspondence with the current scanning mode. In the case of square scanning by a 1-inch camera tube, the scanning area is (1) 9.5 mm.times.9.5 mm in a scanning area within which the image quality is ensured, (2) 13 mm.times.13 mm in the maximum restricted scanning area which is determined by the structure of the camera tube, and (3) 15 mm.times.15 mm to 19 mm.times.19 mm in the scanning area proposed in the present invention. In the following explanation, the scanning area is assumed to be 15 mm.times.15 mm. The circular images inscribed in the respective scanning areas have diameters of 9.5 mm, 13 mm and 15 mm, respectively, so that the areas A.sub.c thereof are 70.9 mm.sup.2, 132.7 mm.sup.2, and 176.7 mm.sup.2, respectively. The effect of the enlargement of the scanning area proposed in the present invention will now be described. If the amplitude response (hereinunder referred to as "AR") of a television camera for DR is improved, the resolution is enhanced FIG. 3 shows the AR of a television camera which has scanned the three kinds of scanning areas (1) to (3) described above in a 1,000-line scanning mode (number of scanning lines: 1,050, number of repetitive frames 7.5/sec, progressive scanning). The AR values in the respective scanning areas (1) to (3) at 800 TV lines are 41%, 59% and 67%, respectively. It is observed that by adopting the means in accordance with the present invention, the AR value is improved to such a great extent as about 1.63 times the AR value obtained by scanning the scanning area of 9.5 mm.times.9.5 mm. That is, the resolution is improved to that extent. The dynamic range is a ratio of the dark current and the maximum signal current obtainable in a camera tube, and the signal to noise-ratio is the ratio of a signal current to a noise current which is the synthesis of the electronic circuit noise in a frequency band and the shot noise due to the signal current. That is, if the maximum signal current obtainable from the camera tube is increased, the improvement of the dynamic range and the signal-to-noise ratio is achieved. If it is assumed that the static capacitance of the photoconductive layer is C.sub.s, the target voltage is V.sub.T, the number of repetitive frames is n.sub.f, and the ratio of the scanning time t.sub.f required for repeating one frame and the scanning time t.sub.c required for scanning the above-described scanning area is .alpha..sub.c (=t.sub.c /t.sub.f), the maximum signal current i.sub.smax is represented by the following formula: EQU i.sub.smax .alpha.C.sub.s V.sub.T .multidot.n.sub.f /.alpha..sub.c (1) If it is assumed that the thickness of the photoconductive layer is d, the dielectric constant is .epsilon..sub.s and the area of the square scanning area is A.sub.s, the following formula holds: EQU C.sub.s =.epsilon..sub.o .epsilon..sub.s A.sub.s /d (2) wherein .epsilon..sub.o =8.84.times.10.sup.-12 F/m. Therefore, the following formula holds: EQU i.sub.smax .alpha..epsilon..sub.o .epsilon..sub.s A.sub.s V.sub.T .multidot.n.sub.f /(d.multidot..alpha..sub.c (3) If the camera tube and the scanning system adopted are determined, .epsilon..sub.s, d, n.sub.f and .alpha..sub.c in the formula (3) are given, so that the following formula holds: EQU i.sub.smax .alpha.A.sub.s V.sub.T (4) Since V.sub.T is determined by the conditions for using the camera tube, the formula (4) becomes as follows: EQU i.sub.smax .alpha.A.sub.s (5) Since the static capacitance of the circular image area inscribed in the square scanning area is represented by the following formula (the area of the circular image area is A.sub.c): EQU C.sub.c =.epsilon..sub.o .epsilon..sub.s A.sub.c /d (6) the maximum signal current i.sub.cmax obtainable from the circular image area is represented by the following formula similar to the formula (5): EQU i.sub.cmax .alpha.A.sub.c (7) That is, according to the present invention, the maximum signal current obtainable from a circular image area is about 2.5 times the value obtained when scanning the area of 9.5 mm.times.9.5 mm, and the dynamic range and the signal-to-noise ratio are improved to that extent. The present invention in which the area beyond the scanning area determined by the structure of a camera tube is scanned involves a fear of producing a deleterious influence such as emission of a large amount of secondary electrons or the damage of the structure at the peripheral portions of the surface of the target or the mesh electrode depending upon the type and the structure of the camera tube used. To prevent such a deleterious influence in the present invention, the voltage E.sub.c1 applied to the control electrode G.sub.1 for controlling the electron beam of the camera tube is controlled in correspondence with the scanning position. In other words, there is provided a means for normally applying a deflection signal for the electron beam to the camera tube but lowering the voltage E.sub.c1 slightly before the scanning position at which the electron beam exerts the deleterious influence so as to cut off the electron beam. FIG. 4 is a block diagram of the structure of an embodiment of the present invention, a real-time DR apparatus, namely, an X-ray fluoroscopic and radiographic apparatus. In FIG. 4, the reference numeral 1 represents an X-ray controller for controlling the generation of an X-ray, 2 an X-ray tube for generating and radiating an X-ray, 3 an object to be inspected (body to be inspected), 4 an X-ray sensor (e.g., an X-ray II) for converting the X-ray projection of the object 3 into an optical image, 6 a television camera for DR for imaging the output image from the sensor 4 for television, 5 an image input controller for controlling the television camera 6, 7 an image processor for processing, displaying and memory controlling the output signal from the television camera 6 after the output image is subjected to A/D conversion, 8 a display for displaying the image, 9 an image memory for storing the output image of the image processor 7, 10 a total controller for synthetically controlling the X-ray controller 1, the image input controller 5 and the image processor 7, and 11 a console for inputting various commands of the operator to the total controller 10. When a command for starting fluoroscopic monitoring and radiographic imaging is input to the console 11, the total controller 10 outputs an X-ray generation instruction to the X-ray controller 1, an image input start instruction to the image input controller 5, and an image read start instruction to the image processor 7, respectively. When the X-ray controller 1 receives the X-ray generation instruction, the X-ray controller 1 instructs the X-ray tube to generate an X-ray in accordance with the content of the instruction, whereby the X-ray tube 2 radiates an X-ray onto the object 3. Various X-ray projections of the object 3 are formed on the X-ray sensor 4 in correspondence with the condition of the body. The X-ray sensor 4 converts an X-ray image in real time and outputs an optical image every time an X-ray projection is input. When the image input controller 5 receives the image input start instruction, the image input controller 5 outputs an operation mode instruction and an image input start instruction to the television camera 6 in accordance with the content of the instruction. The television camera 6 has a mode corresponding to the X-ray fluoroscopic monitoring mode and a mode corresponding to the radiographic imaging mode. In a fluoroscopic monitoring mode, the television camera 6 operates in a 500- or 1,000-line scanning mode at 30 frames per second. In this case, since the X-ray radiation exposure per frame is small and the amount of incident light to the television camera 6 is small, the television camera 6 is operated with the gain of the amplifier thereof increased. In contrast, in a radiographic imaging mode, the television camera 6 operates in not less a 1,000-line scanning mode. For example, in a 1,000-line scanning mode, the television camera operates at 7.5 frames per second. In this case, since the X-ray radiation exposure per frame is as large as about 1,000 times the radiation exposure in a fluoroscopic monitoring mode and the amount of incident light to the television camera 6 is also large, the gain of the amplifier of the television camera 6 is set at the optimum value, so that the signal-to-noise ratio of the image obtained is good and a good image quality is also obtained. When the television camera 6 receives an image input instruction from the image input controller 5, the television camera 6 starts to image the output image of the sensor for television and to input the television image to the image processor 7 in the controlled operation mode. When the image processor 7 receives the image read start instruction from the total controller 10, the image processor 7 reads from the instruction whether or not processing is necessary, what the content of the instruction and the displaying conditions are, and whether or not storage is necessary, executes the necessary processings in accordance with the instruction, and outputs instructions to the display 8 and the image memory 9. The display 8 displays the image under the displaying conditions instructed by the image processor 7. It is also possible to manually control the displaying conditions to a certain extent. The image memory 9 stores the image data only when it receives a storage instruction from the image processor 7. The image memory 9 can naturally store both an analog image and a digital image by appropriately selecting a memory medium and a memory system. FIG. 5 is a block diagram of an example of the television camera 6 used for the apparatus shown in FIG. 4. The reference numeral 21 represents an electromagnetic focusing and electromagnetic deflection type 1-inch camera tube with a tripole electron gun 49 , 22 a mesh electrode G.sub.4, 23 a beam focusing electrode G.sub.3, 24 an accelerating electrode G.sub.2, 25 a beam control electrode G.sub.1, 26 a cathode, 27 a focusing coil, 28 an alignment coil, 29 a horizontal deflection coil, 30 a vertical deflection coil, 31 a preamplifier, 32 a high voltage generator, 33 a deflection current generator, 34 a main amplifier and 35 a controlling signal and synchronizing signal generator. Tripole electron gun 49 comprises cathode 26, beam control electrode G.sub.1 (25), and accelerating electrode G.sub.2 (24). In this embodiment, the high voltage generator 32 adjusts the voltage E.sub.c4 applied to the mesh electrode G.sub.4 to not less than 1,400 V and the voltage E.sub.c3 applied to the beam focusing electrode G.sub.3 to about 1,000 V. The reference numeral 36 represents a beam current controller. The beam current controller 36 generally generates a control voltage bE.sub.c1 for cutting off the beam during the retracing period of the electron beam, or a blanking period which is a period from the end of the retracing period until the beam scanning is stabilized on on the basis of the timing signal applied to a terminal 361 from the controlling signal and synchronizing signal generator 35, and generates a control voltage aE.sub.c1 applied to a terminal 362 so that a predetermined current flows during the imaging period, namely, the period during which the beam scans a predetermined square image portion. In this embodiment, however, the control voltage aE.sub.c1 with the value adjusted by a variable resistor 38 is not applied directly to the terminal 362, but a voltage selected by a switch 37 which is controlled by the data read out of memories 39-1 to 39-n is applied, whereby the beam is generated only while the image input area shown in FIGS. 2B and 2C is scanned. More specifically, beam on/ beam off data corresponding to the respective scanning lines are stored in the memories 39-1 to 39-n, and the value "1" is stored for the circular image input area 64 in FIG. 2C and the value "0" is stored for the hatched area s.sub.1 +s.sub.2. The memories 39-1 to 39-n are read in parallel to each other by the control of the controlling signal and synchronizing signal generator 35 synchronously with the beam scanning, and only the signal read from the memory corresponding to the current scanning line is selected by a multiplexer 40. While the selected signal is "0", the switch 37 is in contact with b and the control signal bE.sub.c1 for cutting off the electron beam is applied to the terminal 362 of the beam current controller 36 and transmitted to the beam control electrode G.sub.1 of a camera tube 21, thereby cutting off the beam. On the other hand, when the signal selected by the multiplexer 40 is "1", the switch is brought into contact with a and the control signal aE.sub.c1 is applied to the terminal 362 of the beam current controller 36, thereby generating a beam current for reading the image These additional elements 37, 39-1 to 39-n and 40 prevent the generation of an electron beam in the unnecessary scanning domain explained with reference to FIG. 2B such that an electron beam is only generated while the circular image input area is scanned. In the case of adopting an apparatus for changing over the scanning mode to, for example, a 500-, 1,000- or 2,000-line scanning mode, memories for, for example, 2,000 lines are prepared, and the order of selection is designated in the multiplexer 40 in correspondence with the instruction of a 500-, 1,000- or 2,000-line scanning mode. Alternatively, a memory may be prepared for each scanning mode. In the above-described embodiments, when a circular image is input, the square in which the circle is inscribed is set as a scanning domain of the beam deflecting means, but the present invention is applicable to the case of inputting an elliptic image. In this case, the scanning domain of the beam deflecting means is not a square but a rectangle in which the ellipse is inscribed. As described above, according to the present invention, by scanning the area beyond the scanning area determined by the photoconductive layer of a camera tube or the structure of an electrode, the scanning area of the image input area is enlarged, thereby achieving the improvement of the resolution of a real-time DR apparatus, the dynamic range and the signal-to-noise ratio. It is therefore unnecessary to use an expensive large-diameter camera tube in place of the camera tube currently used which is available at low cost. Thus, the present invention greatly contributes to reduction in cost of the apparatus. The advantages of the present invention are indissoluble even when a large-diameter camera tube becomes economically available in future. In an embodiment of the present invention, since a measure for precluding the possibility of the deterioration of the characteristics of a camera tube, damage of an electrode, etc. which may be caused in the case of scanning the area beyond the above-described scanning area is provided, the various advantages described above are ensured. While there have been described what are at present considered to be preferred embodiments of the invention, it will be understood that various modifications may be made thereto, and it is intended that the appended claims cover all such modifications as fall within the true spirit and scope of the invention.
	summary
	claims	1. A method of editing graphical representations of fuel bundle groups, comprising:selecting, with a computer interface, one of a plurality of existing bundle groups within a loading map; andperforming a grouping operation on the selected bundle group, the grouping operation including,modifying, by the user with the computer interface, at least one fuel bundle within the selected bundle group, wherein the at least one fuel bundle is, at the start or finish of the modification step, a member of the selected bundle group, the modification being based on a user-selected symmetry and a user-selected fuel bundle characteristic. 2. The method of claim 1, wherein the modifying includes removing at least one fuel bundle from the selected bundle group. 3. The method of claim 1, wherein the modifying includes adding at least one fuel bundle to the selected bundle group. 4. The method of claim 1, wherein modifying includes deleting the selected bundle group. 5. The method of claim 1, wherein the selected bundle group is a fresh bundle group and modifying includes changing at least one type of fuel bundle allowed in the selected bundle group.
	summary
	summary
051174472	summary	BACKGROUND OF THE INVENTION The present invention relates to an image input apparatus such as a television camera. The present invention also relates to an apparatus using a television camera as an image input apparatus and, more particularly, to an X-ray fluoroscopic and radiographic apparatus such as, for example, a real-time digital radiographic apparatus (hereinunder referred to as a "real-time DR apparatus") for inputting an X-ray image in real time, processing the image, and providing an image for diagnosis. In the field of an X-ray image diagnosis apparatus for medical use, a DR apparatus for converting an X-ray image into an electric signal, processing the digital data obtained by subjecting the electric signal to A/D conversion, and displaying the processed image for diagnosis has recently been increasingly developed. Particularly, an X-ray television apparatus composed of an X-ray image intensifier (hereinunder referred to as an "X-ray II") used for obtaining a fluoroscopic image (an image utilized for reducing the X-ray dose per image and chiefly for determining the portion to be photographed) and a television camera has long attracted attention because it is capable of readily producing X-ray image information in the form of an electric signal in real time. An X-ray television camera is now widely used as an input apparatus of a digital fluorographic apparatus (hereinunder referred to as "DF apparatus"), which is one of the real-time DR apparatuses capable of imaging a blood vessel with an excellent contrast resolution by subtraction between the images read before and after the injection of a contrast medium, as disclosed in U.S. Pat. Nos. 4,204,225 and 4,204,226. The DF apparatus requires not only the above-described fluoroscopic image but also a radiographic image (an X-ray image provided with a good image quality by increasing the X-ray dosage per image to about 1,000 times the dosage used for fluoroscopic monitoring) which is to be observed by a doctor for diagnosis. In this case, since the radiographic image is more important, the apparatus is required to have high spatial resolution, contrast resolution and, if necessary, time resolution, and a wide range of an X-ray intensity which enables imaging, in other words, a wide dynamic range, and among these, the demand for a high spatial resolution and a wide dynamic range is strong. As described above, in a real-time DR apparatus represented by a DF apparatus, the importance of a radiographic image is greater than a fluoroscopic image, so that a television camera used for the real-time DR apparatus is also required to have a high resolution, a wide dynamic range, a high signal-to-noise ratio, a high time resolution, etc. Among these requirements, it will be understood if the number of frames per second (e.g., generally 30 frames/sec in the case of scanning 525 lines) of the television camera used in the real-time DR apparatus is taken into consideration that the demand for the time resolution is easily dealt with. In the present invention, measures for dealing with the other three demands are provided. In order to improve the spatial resolution, the following measures are conventionally adopted. (i) A high-resolution type camera tube 1 inch in diameter (for example, a Saticon (a registered trademark of Nippon Hoso Kyokai), or in some cases, a Plumbicon (a registered trademark of N. V. Philips Gloeilampenfabrieken)) is used. (ii) The number of scanning lines is increased from 525 to 1,125, as described in Japanese Patent Application Laid-Open No. 61-113432. In order to enlarge the dynamic range and improve a signal-to-noise ratio, the following measures are conventionally adopted. (iii) The necessary frequency band is limited as much as possible so as to reduce the amount of noise. (iv) The stray capacitances from the camera tube to the preamplifier are reduced so as to reduce the amount of noise. (v) A signal current from the camera tube is increased. Among these, since the measures (i) and (iv) largely depend on the characteristics of the device and the parts such as a camera tube, an FET (field-effect transistor) and a resistor adopted, and the mounting technique therefor, the selection and the mounting technique of the device or the parts are taken into adequate consideration. In the measures (ii) and (iii), the number of scanning lines and the frequency band are necessarily determined by the specification of the DR apparatus, namely, by the number of images photographed per second and the number of pixels per image. However, with respect to the measure (ii), although it is easy to increase the number of scanning lines itself, it is a problem whether or not the camera tube adopted has a spatial frequency characteristic which corresponds to the increase in the scanning lines. Use of a high-resolution type camera tube is therefore insufficient, and a camera tube having as large a diameter as possible which allows a large scanning area on the surface of a photoconductive layer or the surface of a target is adopted. In the measure (v), it is necessary to increase the amount of charge stored on the surface of a photoconductive layer by increasing the amount of incident light falling onto the camera tube. For this purpose, it is necessary to increase the static capacitance C.sub.s of a photoconductive layer or the voltage applied to the surface of a photoconductive layer, in other words, a signal electrode voltage, or the target voltage V.sub.T of the camera tube. In order to increase C.sub.s, the thickness d of a photoconductive layer is reduced, the dielectric constant .epsilon..sub.s is increased and the scanning area A.sub.2 is increased. Among these, d, .epsilon..sub.s and V.sub.T are determined by the characteristics of the photoconductive layer, and A.sub.s is determined by the diameter of the camera tube. Therefore, a camera tube having as large a diameter as possible is used in the same way as in the case of realizing the measure (ii). As described above, in order to improve the resolution, the dynamic range and the signal-to-noise ratio of a television camera used for a real-time DR apparatus (hereinunder referred to as "television camera for DR"), the diameter of the camera tube is increased and other measures are adopted in the prior art in addition to the selection of a camera tube and the improvement of the circuit and the mounting technique. As a large-diameter camera tube, a camera tube having a diameter of 2/3 to 1 inch or 1.5 inches, in some cases, is used. The increase in the diameter of a camera tube, however, is not always advantageous in that the cost of not only the device but also the television camera using the camera tube and further the DR apparatus as a whole is raised. Still more, new development of a large-diameter camera tube involves a large risk and it is difficult to determine whether or not the thus-developed camera tube will be appropriate. SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to eliminate the above-described problems in the prior art and to provide an image input apparatus having a high resolution, a wide dynamic range and a high signal-to-noise ratio without using a large-diameter camera tube. To achieve this aim, the present invention provides an image input apparatus comprising a camera tube including a photoconductive layer onto which an optical image is to be projected, a cathode for emitting an electron beam for scanning the photoconductive layer, and a control electrode for controlling a beam current of the electron beam emitted from the cathode in accordance with a control voltage; and a deflection circuit for periodically deflecting the electron beam to scan the photoconductive layer; the deflection circuit periodically deflecting the electron beam to scan an area outside a restricted scanning area determined by an internal structure of the camera tube. The above and other objects, features and advantages of the present invention will become clear from the following description of the preferred embodiments thereof, taken in conjunction with the accompanying drawings.
	abstract	A standard member for automatically, stably, and highly accurately performing magnification calibration used in an electron microscope, the standard member including, on the same plane, a multilayer film cross section formed by alternately laminating materials different from each other, a plurality of first mark patterns arranged across a first silicon layer and in parallel to the multilayer film cross section, at least a pair of second mark patterns arranged across a second silicon layer thicker than the first silicon layer on the opposite side of the first mark patterns with respect to the multilayer film cross section and in parallel to the multilayer film cross section, and a silicon layer arranged on the outer side of the first mark patterns and the second mark patterns with respect to the multilayer film cross section.
	summary
	abstract	The present invention relates to a device adapted for producing energy by nuclear fission, the device comprising a core container of a core container material, which core container encloses an inner tubing of an inner tubing material, the inner tubing and/or the core container having an inlet and an outlet, the device further comprising a molten halide salt located in the core container or in the inner tubing, wherein the inner tubing comprises one or more sections consisting of single crystal corundum. The invention further relates to methods of controlling nuclear fission processes using the device and to the use of a corundum tube as a structural material in a nuclear fission device. The invention provides improved economy in molten salt nuclear fission processes.
	abstract	The present disclosure provides a beam shaping assembly for neutron capture therapy, wherein the beam shaping assembly includes a neutron generating device, a moderator, a disturbing unit and a beam outlet. The neutron generating device is used to generate neutrons that form a neutron beam in a direction from the neutron generating device to the beam outlet, the moderator adjacent to the neutron generating device for adjusting fast neutrons in the neutron beam to epithermal neutrons. The disturbing unit is located between the moderator and the beam outlet for passing through the neutron beam and reducing the gamma ray content in the neutron beam passing through the beam outlet. The technical solution provided by the present disclosure can effectively reduce the gamma ray content in the neutron beam under the premise that the quality of the neutron beam is not significantly adversely affected.
	description	The present application is a continuation of U.S. patent application Ser. No. 10/250,132, which was filed on Jun. 5, 2003, entitled “CT Imaging System With Multiple Peak X-Ray Source,” and issued as U.S. Pat. No. 7,120,222, and also is related to U.S. patent application Ser. No. 10/064,775, which was filed on Aug. 15, 2002, entitled “A Hybrid Scintillator/Photo Sensor & Direct Conversion Detector,” and issued as U.S. Pat. No. 6,819,738, and which is incorporated herein by reference. The present invention relates generally to multi-slice computed tomography (CT) imaging systems, and more particularly, to a system and method of performing energy discrimination therein. In computed topography (CT) imaging, portions of a patient are scanned and the density of materials contained therein are determined for various diagnostic and evaluation purposes. There is a continuous effort to increase CT imaging system scanning capabilities. Specifically, in CT imaging, it is desirable not only to be capable of determining density of scanned materials, but also to be able to distinguish between materials or combinations of materials that have similar densities. For example, in certain testing procedures, in order to enhance visibility of blood and to better differentiate blood from other tissues or undesirable deposits within a vessel or organ, Iodide may be injected into the bloodstream of a patient. Combination of Iodide and water or blood, which consists mainly of water, and a combination of calcium deposits and soft tissue exhibit similar material densities, resulting in poor spatial and low contrast resolution between each combination and having effectively similar corresponding brightness levels when viewed by a practitioner. It is undesirable to have calcium build-up on inner linings of blood vessel walls. Thus, the practitioner, due to difficulty in discerning between the brightness levels of reconstructed CT images for the stated combinations, may not be able to determine whether there exists a calcium build-up in the blood vessels of the patient. Referring now to FIG. 1, a cross-sectional view of a traditional CT tube assembly 10 is shown. CT imaging systems include a gantry that rotates at various speeds in order to create a 360° image. The gantry contains the CT tube assembly 10, which generates x-rays across a vacuum gap 12 between a single cathode 14 and an anode 16. In order to generate the x-rays, a large voltage potential is created across the vacuum gap 12 allowing electrons, in the form of an electron beam, to be emitted from the cathode 14 to a single target 18 of the anode 16. In releasing of the electrons, a filament contained within the cathode 14 is heated to incandescence by passing an electric current therein. The electrons are accelerated by the high voltage potential and impinge on the target 18, whereby they are abruptly slowed down to emit x-rays and form an x-ray beam that passes through a CT tube window 20. After passing through the CT tube window 20, the x-ray beam is filtered via a single filter 22. The filter 22 reduces the number of low energy x-rays that have energy levels below a predetermined energy level, thus reducing x-ray exposure to a patient. An example of a pre-patient energy spectrum plot of number of x-rays versus corresponding energy levels is shown in FIG. 2. A post-filter spectrum curve 24 overlays an approximate pre-filter spectrum curve 26. Notice that the spectrum curve 24 is single peaked and that the number of x-rays corresponding to energy levels below 40 KeV are significantly reduced, due to absorption by the filter 22. The post filter x-rays pass through a portion of the patient and are detected by an x-ray detector array. As the x-rays pass through the patient, the x-rays become attenuated before impinging upon the detector array. X-ray attenuation measurements are generated by the x-ray detector corresponding to electrical signal response generated by the received x-rays having varying energy levels depending upon attenuation thereof. An x-ray image is reconstructed in response to the attenuation measurements. The x-ray detector array generates an x-ray signal in response to the single peaked energy spectrum. Number of x-rays received by the detector is integrated over an average area of the detector and over a view time interval to generate an integrated signal. The integrated signal is directly related to densities of scanned materials of the patient. As is known in the art, it is difficult from the resulting energy spectrum and from inherent characteristics of integration to differentiate between similar material densities. It would therefore be desirable to provide a CT system of energy discrimination to differentiate between different scanned materials and different scanned material combinations to increase CT scanning utility and capability. It would also be desirable for the CT system to be capable of performing energy discrimination with accuracy, clarity, and without increased x-ray exposure to a patient. The present invention provides a system and method for performing energy discrimination within an imaging system. An x-ray source for performing energy discrimination within an imaging system is provided and includes a cathode-emitting device for emitting electrons and an anode that has a target whereupon the electrons impinge to generate an x-ray beam with multiple x-ray quantity energy peaks. A method of performing energy discrimination in the imaging system is also provided, which includes emitting the electrons. The x-ray beam with the x-ray quantity energy peaks is generated. The x-ray beam is directed through an object and is thereafter received. An x-ray image having multiple energy differentiable characteristics is generated in response to the x-ray beam as received. One of several advantages of the present invention is that it provides a system that is capable of performing energy discrimination, thus allowing a practitioner to differentiate between materials and material combinations having similar densities. In so doing, the present invention provides an increased yield of information for improved diagnostic, examination, testing, and evaluation purposes. Another advantage of the present invention is that it provides improved spatial and low contrast resolution between different materials, thus further providing increased ease in differentiating between scanned materials. Furthermore, the present invention provides energy discrimination while minimizing x-ray exposure to a patient. The present invention itself, together with attendant advantages, will be best understood by reference to the following detailed description, when viewed in conjunction with the accompanying drawing figures. In each of the drawing figures discussed as follows, the same reference numerals are generally used to refer to the same or similar components. While the present invention is described with respect to a system and method for performing energy discrimination within a computed tomography (CT) imaging system, the following apparatus and method are capable of being adapted for various purposes and are not limited to the following applications: MRI systems, CT systems, radiotherapy systems, X-ray imaging systems, ultrasound systems, nuclear imaging systems, magnetic resonance spectroscopy systems, and other applications known in the art. In the following description, various operating parameters and components are described for one constructed embodiment. These specific parameters and components are included as examples and are not meant to be limiting. Also, in the following description, the term “x-ray quantity energy peaks” refers to the general shape of an energy spectrum plot and the peaks contained therein. An energy spectrum plot is a plot of x-ray energy levels and corresponding number of x-rays for each energy level. “X-ray quantity energy peaks,” however, does not refer to mere sporadic spikes or minor or other insignificant data that may occur or exist within the energy plot. See FIG. 8 description below for a further detailed explanation. Referring now to FIG. 3, a perspective view of a CT imaging system 30 including an x-ray source 32 in accordance with an embodiment of the present invention is shown. The imaging system 30 includes a gantry 34 that has a rotating inner portion 36 containing the x-ray source 32 and an energy-differentiating detector 40. The x-ray source 32 projects a beam of x-rays having multiple x-ray quantity energy peaks toward the detector 40. The source 32 and the detector 40 rotate about an operably translatable table 42. The table 42 is translated along a z-axis between the source 32 and the detector 40 to perform a helical scan. The beam, after passing through a medical patient 44 situated within a patient bore 46, is detected at the detector 40 so as to generate projection data that is used to create a CT image. Referring now to FIG. 4, a cross-sectional close-up block diagrammatic view of the imaging system 30 utilizing an energy discrimination system 50 in accordance with an embodiment of the present invention is shown. The energy discrimination system 50 includes the source 32, the detector 40, and an x-ray controller 52. Generally, in operation the source 32 and the detector 40 rotate about a center axis 53. The beam 54 is received by multiple detector elements 56. Each detector element 56 generates an electrical signal corresponding to intensity of the impinging x-ray beam 54. As the beam 54 passes through the patient 44 the beam 54 is attenuated. Rotation of the inner portion 36 and operation of source 32 are governed by a control mechanism 58. Control mechanism 58 includes the x-ray controller 52 that provides power and timing signals to source 32 and a gantry motor controller 60 that controls the rotational speed and position of the inner portion 36. A data acquisition system (DAS) 62 samples analog data from the detector elements 56 and converts the analog data to digital signals for subsequent processing. An image reconstructor 64 receives sampled and digitized x-ray data from the DAS 62 and performs high-speed image reconstruction. A main controller 66 stores the CT image in a mass storage device 68. The x-ray source 32 and the detector 40 rotate around an object to be imaged, such as the patient 44, so that the angle at which the beam intersects the object constantly changes. A group of x-ray attenuation measurements, i.e., projection data, from the detector 40 at one gantry angle is referred to as a “view.” A “scan” of the object comprises a set of views made at different gantry angles during one revolution of the x-ray source 32 and the detector 40. In an axial scan, the projection data is processed so as to construct an image that corresponds to two-dimensional slices taken through the object. One method for reconstructing an image from a set of projection data, projection data referring to a group of attenuation measurements, is referred to as the “filtered back-projection technique.” This process converts the attenuation measurements from a scan into discrete integers, ranging from −1024 to +3072, called “CT numbers” or “Hounsfield Units” (HU). These HU's are used to control the brightness of a corresponding pixel on a cathode ray tube or a computer screen display in a manner responsive to the attenuation measurements. For example, an attenuation measurement for air may convert into an integer value of −1000 HU's (corresponding to a dark pixel) and an attenuation measurement for very dense bone matter may convert into an integer value of +3000 (corresponding to a bright pixel), whereas an attenuation measurement for water may convert into an integer value of 0 HU's (corresponding to a gray pixel). This integer conversion, or “scoring” allows a physician or a technician to determine the density of matter based on the intensity of the computer display and thus locate and identify areas of concern. In one embodiment of the present invention, the detector 40 includes a first detector array 70 and a second detector array 72, as shown. The first array 70 may be a scintillator detector/photo-sensor detector so as to allow for the collection of traditional information for creating anatomical detail for CT slices. The second array 72 may be a direct conversion (DC) detector, such as a cadmium zinc telluride detector, configured in an x-ray counting and energy discrimination mode to count attenuated x-rays and to measure attenuated x-ray energy. Number and energy of the attenuated x-rays is used when performing energy discrimination to differentiate between material characteristics. Elemental composition and/or density of various tissue materials may be determined, such as differentiating between iodine, blood, calcium, or other materials known in the art. Information obtained from the arrays 70 and 72 may be super positioned to create a single image having identically positioned and overlapping information of anatomical detail and/or tissue discrimination (material type and density). The second array 72 may be of a single slice design and/or a multiple slice design. The multiple slice design may provide information on a variety of different tissue materials, whereas the multiple slice design may be integrated across multiple slices for improved statistics on an individual basis. When the second array 72 is used in the x-ray counting and energy discrimination mode, x-ray dose added to the CT exam is minimized since a low quantity of x-rays are used to perform energy discrimination. To gather energy discrimination data a smaller amount of x-rays are used over a full or normal dose of x-rays, as used in a normal CT scan. A normal CT scan is performed with the first array 70 to provide detailed data, such as detailed anatomical data. When gathering energy discrimination data the second array 72 is used to generate an overlay image with material differentiating characteristics, such as tissue differentiating characteristic. The above-described embodiment is for example purposes only. Although, it is preferred that at least one array be capable of detecting numbers of x-rays for various energy levels or ranges of energy levels, which are hereinafter referred to as x-ray quantity energy levels, any number of arrays may be used. For example, in the above-described embodiment array 72 is capable and configured to detect x-ray quantity energy levels, whereas array 70 is not. Also, each of the arrays 70 and 72 may be of various type and style and be in various configurations known in the art. For a further detailed description of the detector 40 and various possible embodiments thereof, see patent application Ser. No. 10/064,775, which is entitled “A Hybrid Scintillator/Photo Sensor & Direct Conversion Detector,” which issued as U.S. Pat. No. 6,819,738, and which is incorporated herein by reference. The main controller 66 also receives commands and scanning parameters from an operator via an operator console 76. A display 78 allows the operator to observe the reconstructed image and other data from the main controller 66. The operator-supplied commands and parameters are used by the main controller 66 in operation of the x-ray controller 52, the gantry motor controller 60, and the DAS 62. In addition, the main controller 66 operates a table motor controller 74, which translates the table 42 so as to position the patient 44 in the gantry 34. The x-ray controller 52, the gantry motor controller 60, the image reconstructor 64, the main controller 66, and the table motor controller 74 are preferably based on micro processors, such as a computer having a central processing unit, memory (RAM and/or ROM), and associated input and output buses. The x-ray controller 52, the gantry motor controller 60, the image reconstructor 64, the main controller 66, and the table motor controller 74 may be a portion of a central control unit or may each be stand-alone components as shown. In the following embodiments a cathode-emitting device may refer to any electron emitting device or component. A cathode-emitting device may refer to a cathode, an x-ray tube kVp, a cathode-emitting surface, a cathode element, or other electron emitting device or component known in the art. Referring now to FIG. 5, a cross-sectional close-up block diagrammatic view of an energy discrimination system 50″ having a single rotating target 80 of an anode 81, in accordance with an embodiment of the present invention, is shown. A first cathode-emitting device 82 and a second cathode-emitting device 84 emit electrons that are directed to impinge upon the target 80. A first kVp (kilovolt peak) exists between the first cathode-emitting device 82 and the anode target 80, which can be represented by a first approximately linear pre-filter spectrum curve of number of x-rays per energy level. A second kVp, that is different from that of the first kVp, exists between the second cathode-emitting device 84 and the anode target 80, which can be represented by a second approximately linear pre-filter spectrum curve of number of x-rays per energy level. The pre-filter spectrum curves may be represented using Cramer's Rule, as is known in the art. The first kVp pre-filter spectrum curve is different in slope than that of the second kVp pre-filter spectrum curve. Upon impact with the target 80, x-rays in the form of x-ray beams 85 and 86 are generated and directed through a rotating filter 88. The rotating filter 88 includes a first filter 90 and a second filter 92, and each of the filters 90 and 92 has different energy-absorbing characteristics. Although, a rotating filter is utilized, some other filtering device having two or more filters may be used. In one embodiment, each filter 90 and 92 prevents passage of x-rays corresponding to energy levels below associated predetermined energy levels for each of the x-ray beams 85 and 86. In effect, the filters 90 and 92, for the stated embodiment, are acting as high-pass filters. Of course, the filters may each perform as a band pass, notch, low pass, digital, or other type of filter as known in the art. The x-ray beams 85 and 86 are mixed upon passing through the filters 90 and 92 to generate a mixed or composite post-filter beam 93 having multiple x-ray quantity energy peaks, due to generation of different quantities of electrons at associated energy levels therein by the devices 82 and 84 and different absorbing characteristics of the filters 90 and 92. The filters 90 and 92, in effect, may have different energy pass ranges so as to allow x-rays within a predetermined energy range to pass through the filters 90 and 92. The energy pass ranges may be of any size and be associated with any energy level or levels. An x-ray controller 52′, is electrically coupled to the devices 82 and 84 and to a filter rotating device 94, which is coupled to and rotates the filter 88. The controller 52′, synchronously transitions between the devices 82 and 84 and the filters 90 and 92, respectively. The controller 52′ may be in the form of or an integral part of the x-ray controller 52 or the main controller 66, may be a separate controller, or may be some other controller known in the art. Referring now to FIG. 6, a cross-sectional close-up block diagrammatic view of an energy discrimination system 50″ having dual anode rotating targets 100, in accordance with another embodiment of the present invention, is shown. A first cathode-emitting device 82′ and a second cathode-emitting device 84′ emit electrons that are directed to impinge upon a first rotating target 102 and a second rotating target 104 of an anode 106, respectively. A first kVp exists between the first cathode-emitting device 82′ and the rotating target 102, and a second kVp exists between the second cathode-emitting device 84′ and the rotating target 104, in a fashion similar to that of the embodiment in FIG. 5. Upon impact with the targets 102 and 104, x-rays in the form of x-ray beams 108 are generated and directed through the rotating filter 88, whereupon exiting the filter 88 they are mixed to generate a mixed or composite post-filter beam 109. Although the rotating filter 88 is utilized, some other filtering device having one or more filters may be used. The filters 90 and 92 may be transitional or may be stationary. The beam 109 has two or more x-ray quantity energy peaks, as is best shown in FIG. 8. As with the embodiment of FIG. 5, the controller 52′ is electrically coupled to the emitting devices 82′ and 84′ and to the filter rotating device 94, which is coupled to and rotates the filter 88. The controller 52′, synchronously transitions between the devices 82′ and 84′ and the filters 90 and 92, respectively. In an alternative embodiment, the filters 90 and 92 are stationary and the devices 82′ and 84′ are operated simultaneously. FIGS. 5 and 6 illustrate two possible embodiments of the present invention, other embodiments may be easily envisioned by one skilled in the art. There may exist any number of anode targets, cathode-emitting devices, and filters. For example, the first cathode-emitting device 82 and the second cathode-emitting device 84 may be replaced by a single cathode-emitting device operating so as to generate and transition between two different kVps. Also, more than two cathode-emitting devices and/or filters may be used to generate a beam having any number of x-ray quantity energy peaks. These examples are described in further detail below. Although, it is preferred for accuracy, resolution, and clarity purposes to have at least two cathode-emitting devices and at least two filters, as is shown in the embodiments of FIGS. 5 and 6, various quantities of each may be used. In a couple alternative embodiments of the present invention, the embodiments of FIGS. 5 and 6 are modified such that only a single cathode-emitting device is used in combination with the rotating filter 88. The first filter 90 and the second filter 92 are alternated therebetween for a single x-ray beam to generate a post-patient x-ray beam having a dual peaked energy spectrum. The single cathode-emitting device may have a quickly varying kVp, which may be used in conjunction with a transitioning or rotating filter. In a further pair of alternative embodiments of the present invention, the embodiments of FIGS. 5 and 6 are modified, such that the cathode-emitting devices 82, 82′, 84, and 84′ are utilized in conjunction with a single stationary filter instead of the rotating filter 88. The cathode-emitting devices 82 and 84 and the cathode-emitting devices 82′ and 84′ are alternated, respectively, therebetween to generate x-ray beams having different energy spectrum profiles or distributions of the number of x-rays per energy level. Referring now to FIG. 7, a logic flow diagram illustrating a method of performing energy discrimination in an imaging system in accordance with an embodiment of the present invention is shown. For simplicity, the method of FIG. 7 is described with respect to the embodiments of FIGS. 5 and 6, but is not limited to the stated embodiments. In step 110, one or more cathode-emitting devices, such as emitting devices 82, 82′, 84, and 84′, emit electrons to impinge upon one or more anode targets, such as targets 80, 102, and 104, as described above. In step 112, x-ray beams, such as beams 86 and 108, are generated having multiple x-ray quantity energy peaks. For example, a first x-ray beam 114 having a first x-ray quantity energy peak 116 and a second x-ray beam 118 having a second x-ray quantity energy peak 120 may be generated; beams 114 and 118 are best seen in FIG. 6 and peaks 116 and 120 are best seen in the pre-patient energy spectrum plot of FIG. 8. The first x-ray quantity energy peak 116 and the second x-ray quantity energy peak 120 are generated by respective kVp of each cathode-emitting device 82′ and 84′ and filtering of each x-ray beam 108 by the filters 90 and 92. Although, in this described embodiment the energy spectrum plot has only a pair of peaks 116 and 120, an energy spectrum plot may have any number of peaks, by altering the number of cathode-emitting devices, filters, and correlations between the cathode-emitting devices and the filters. The peaks 116 and 120 may correspond to predetermined energy bins 122 and 124, as shown, which may be separated by one or more separation zones 126 (only one is shown) having significantly reduced quantities of x-rays. The bins 122 and 124 and the separation zones 126 aid in accurately differentiating between materials having similar material energy densities. Referring again to FIG. 7, in step 128, the x-ray beams are filtered, via the rotating filter 88. The controller 52′ transitions between the first filter 90 and the second filter 92. The controller 52′ transitions between the filters 90 and 92 at least once for each view in a scan of the patient 44. In step 130, the x-ray beams are mixed so as to generate a mixed or composite post-filter x-ray beam, such as beam 93 or beam 109 in FIGS. 5 and 6, having multiple x-ray quantity energy peaks. In step 132, the post-filter x-ray beam is directed through at least a portion of the patient 44. In step 134, the detector 40 receives the post-filter x-ray beam and in response thereto generates an x-ray signal having material energy density differentiating information, such as numbers of x-rays per energy level, contained therein. The x-ray detector 40 may measure x-ray quantity energy levels of the x-ray beams corresponding to each of the peaks 116 and 120 and may measure x-ray quantity energy levels corresponding to the energy bins 122 and 124 to aid in simplifying energy discrimination of multiple materials having similar energy densities. The detector 40 or other signal conditioning devices known in the art may signal condition the x-ray signal such that separations between x-ray quantity energy peaks are effectively magnified, by filtering out undesired predetermined energy density levels. In step 136, the system 30 generates an x-ray image having multiple energy density differentiable characteristics, such as image contrast levels, brightness levels, color variations, or other differentiating characteristic known in the art, in response to the x-ray signals. In step 138, materials and material densities of the scanned portion of the patient 44 are identified. The materials and material densities may be determined by a practitioner, by the main controller 66, or by some other device or technique known in the art. In having multiple x-ray energy peaks, materials or material combinations having similar densities may be easily differentiated, since each material or material combination exhibits different x-ray energy peak profiles. The x-ray energy peak profiles may be further used to generate different image material differentiating characteristics. For example, a first material combination may exhibit a dual peaked energy spectrum having a first magnitude set of values for each peak and a second material combination may also exhibit a dual peaked energy spectrum, but having a second and different magnitude set of values for each peak. The differences in magnitude or peak values between the two material combinations may be illustrated in an x-ray image through use of one or more of the above-mentioned differentiating characteristics. The above-described steps are meant to be an illustrative example; the steps may be performed synchronously, sequentially, simultaneously, or in a different order depending upon the application. The present invention provides an energy discrimination system and method for easily differentiating between materials and material combinations that have similar energy densities. The present invention provides this increased performance capability and improved spatial and low contrast resolution while minimizing x-ray exposure to a patient. The above-described apparatus, to one skilled in the art, is capable of being adapted for various purposes and is not limited to control systems or other communication systems. The above-described invention may also be varied without deviating from the spirit and scope of the invention as contemplated by the following claims.
	claims	1. A system for attenuating seismic forces in a nuclear reactor assembly comprising:a containment vessel configured located above a support surface;a reactor pressure vessel mounted within the containment vessel to house a nuclear reactor core;a containment vessel encapsulating and suspending the reactor pressure vessel within an inner chamber, the containment vessel including a top head extending over a top end of the reactor pressure vessel and a bottom head extending underneath a bottom end of the reactor pressure vessel;a support skirt located on a floor of a reactor bay and integrally coupled to the bottom head of the containment vessel, the support skirt supporting substantially the entire weight of the reactor pressure vessel and suspending the bottom head of the containment vessel above the floor of the reactor bay; andan attenuation device integrally operatively coupled to the containment vessel and located along a longitudinal centerline of the reactor pressure vessel to attenuate seismic forces transmitted from the support surface to the reactor pressure vessel via the containment vessel in a substantially transverse direction to the longitudinal centerline;wherein the attenuation device includes an integrated vertical key portion and an integrated lateral support portion, the integrated vertical key portion extending upwardly in a substantially vertical direction from an inner surface of the lower head of the containment vessel and the integrated lateral support portion extending downwardly in a substantially vertical direction from an outer surface of the containment vessel;wherein the integrated vertical key portion is to engage inserts into a recess integrally formed and extending vertically up into the lower head of the reactor pressure vessel to provide lateral support to the reactor pressure vessel; andwherein the integrated lateral support portion is to engage between at least a pair of stops extending upwardly from the support surface to receive the seismic forces transmitted from the support surface. 2. The system of claim 1, wherein the attenuation device is configured to provide for a thermal expansion of the reactor pressure vessel within the containment vessel. 3. The system of claim 2,wherein the integrated vertical key portion comprises a substantially vertical protrusion; andwherein the recess comprises a vertical clearance to account for a thermal expansion of the reactyor pressure vessel along the longitudinal centerline. 4. The system of claim 3,wherein the vertical protrusion comprises a diameter; andwherein the vessel recess further comprises an annular-shaped clearance to account for the thermal expansion of the diameter of the vertical protrusion. 5. The system of claim 1,further comprising a support structure located in an upper half of the containment vessel and configured to support the reactor pressure vessel within the containment vessel;wherein the attenuation device is located in the bottom half of the containment vessel. 6. The system of claim 5,wherein a majority of a weight of the reactor pressure vessel is supported by the support structure; andwherein substantially none of the weight of the reactor pressure vessel is supported by the attenuation device. 7. The system of claim 1,wherein the containment vessel comprises a cylindrical-shaped support skirt that contacts the support surface;wherein a bottom head of the containment vessel is located some distance above the support surface; andwherein the support skirt comprises through-holes configured to allow coolant to flow through the support skirt and contact the bottom head. 8. The system of claim 1,wherein the integrated vertical key comprises a vertical post located along the longitudinal centerline of the containment vessel; andwherein the vertical post is inserted into the recess of the reactor pressure vessel. 9. The system of claim 8,wherein the containment vessel comprises a bottom head; andwherein the vertical post extends upward from the bottom head of the containment vessel into the recess associated with the reactor pressure vessel. 10. The system of claim 9,wherein the integrated lateral support may be portion is configured to contact the at least the a pair of stops without directly contacting the a support surface. 11. A system for attenuating seismic forces in a nuclear reactor assembly comprising:a reactor pressure vessel retaining a nuclear reactor core;a containment vessel encapsulating and suspending the reactor pressure vessel within an inner chamber, the containment vessel including a top head extending over a top end of the reactor pressure vessel and a bottom head extending underneath a bottom end of the reactor pressure vessel;a support base located on a floor of a reactor bay and integrally coupled to the bottom head of the containment vessel, the support base supporting substantially the entire weight of the reactor pressure vessel and suspending the bottom head of the containment vessel above the floor of the reactor bay; andan attenuation device integrally coupled to the reactor pressure vessel and located along a longitudinal centerline of the reactor pressure vessel to attenuate seismic forces transmitted from the support surface to the reactor pressure vessel via the containment vessel in a substantially transverse direction to the longitudinal centerline;wherein the attenuation device includes an integrated vertical key portion extending downwardly in a substantially vertical direction from an outer surface of the reactor pressure vessel and a recess formed in an inside surface of the bottom head of the containment vessel to receive the integrated vertical key portion and provide lateral support to the reactor pressure vessel. 12. The system of claim 11, wherein a wall forming the bottom head of the containment vessel has an increasing thickness from lateral sides of the containment vessel towards the longitudinal centerline of the reactor pressure vessel, and the recess extends into the wall from the inside surface of the bottom head and has a depth less than the thickness of the wall. 13. The system of claim 12, wherein the recess comprises a vertical clearance from a bottom end of the integrated vertical key portion to account for a thermal expansion of the reactor pressure vessel along the longitudinal centerline. 14. The system of claim 13, wherein:the integrated vertical key portion comprises a diameter; andthe vessel recess further comprises an annular-shaped clearance to account for the thermal expansion of the diameter of the integrated vertical key portion. 15. The system of claim 11, wherein:the integrated vertical key portion comprises a vertical post located along the longitudinal centerline of the reactor pressure vessel; andthe vertical post is inserted into the recess formed in the containment vessel. 16. The system of claim 11, wherein the attenuation device is configured to provide for a thermal expansion of the reactor pressure vessel within the containment vessel. 17. The system of claim 11, further comprising a suction line that extends from the recess to an outside surface of the bottom head of the containment vessel. 18. The system of claim 11, wherein the integrated vertical key portion includes a conical shaped surface and the recess includes a complimentary shaped conical inner surface.
	summary
	summary
	claims	1. A method for forming a plurality of images on a sample for categorizing defects on said sample, wherein said sample comprises a first pixel column and a second pixel column comprising:moving said sample continuously in a direction perpendicular to said first pixel column and said second pixel column, and from said first pixel column to said second pixel column;line-scanning said first pixel column with a charged particle beam under a first photo-current condition;line-scanning said first pixel column again with said charged particle beam under a second photo-current condition, wherein said second photo-current condition is different from said first photo-current condition;line-scanning said second pixel column with said charged particle beam under said first photo-current condition; andline-scanning said second pixel column again with said charged particle beam under said second photo-current condition;wherein said sample is moved continuously at a speed allowing scanning processing to be done on each pixel column under different photo-current conditions. 2. The method of claim 1, wherein said condition of illumination of said optical beam remains constant during one line scan. 3. The method of claim 1, wherein said condition of illumination of said optical beam includes optical beam intensity, optical beam wavelength, optical beam energy, duration of illumination, or any combination thereof. 4. The method of claim 1, wherein during the formation of each said group of n scan lines, at least two scan lines are formed at identical said condition of illumination of said optical beam. 5. The method of claim 1, wherein said nY scan lines are spaced apart by a fixed distance d such that the product of n multiplied by d is equal to said predefined pixel size p (nd=p). 6. The method of claim 1, wherein said charged particle beam is offset by one or more lines along the line-to-line advancement direction. 7. The method of claim 1, wherein each of formed said images is inspected independently. 8. The method of claim 1, wherein formed said images are inspected collectively after being combined through mathematical operation. 9. The method of claim 1, wherein each said image is formed from a collection of Y said scan lines correspondingly selected from each of said Y groups of n scan lines. 10. The method of claim 1, wherein said predefined types of defects comprise the N+/P-well plug open defect, the P+/N-well plug open defect, N+/P-well plug leakage defect, P+/N-well plug leakage or any combination thereof. 11. The method of claim 1, wherein illumination of said optical beam causes patterns of particular material or electrical properties in said area to display a brighter grey level. 12. The method of claim 1, wherein X, Y and n are an integer equal to or greater than 2. 13. The method of claim 1, wherein said condition of illumination of said optical beam is modulated on/off or to different power levels or selected from different sources of wavelength, in synchronization with said line-scanning. 14. A charged particle beam inspection system for categorizing defects on a sample with a first pixel column and a second pixel column, comprising:a charged particle beam imaging apparatus for forming voltage contrast images of said sample by scanning a charged particle beam over said first pixel column and said second pixel column;an optical beam apparatus for illuminating said sample to induce a first photo-current condition and a second photo-current condition on said sample, wherein said first photo-current condition is different from said second photo-current condition; anda defect determination apparatus comprising a control module and an image analysis module, wherein said control module is coupled to and controls said charged particle beam imaging apparatus and said optical beam apparatuswherein said charged particle beam imaging apparatus scans said first pixel column under said first photo-current condition, then scans said first pixel column under said second photo-current condition, then scans said second pixel column under said first photo-current condition, and then scans said second pixel column under said second photo-current condition; andwherein said sample is moved continuously at a speed allowing scanning processing to be done on each pixel column under different photo-current conditions and said image analysis module is coupled with said charged particle beam imaging apparatus for receiving and analyzing said voltage contrast images from said charged particle beam imaging apparatus for categorizing types of defects on said sample. 15. The charged particle beam inspection system of claim 14, wherein said condition of illumination of said optical beam remains constant during one line scan. 16. The charged particle beam inspection system of claim 14, wherein during the formation of each said group of n scan lines, at least two scan lines are formed at identical said condition of illumination of said optical beam. 17. The charged particle beam inspection system of claim 14, wherein said nY scan lines are spaced apart by a fixed distance d such that the product of n and d is equal to said predefined pixel size p (nd=p). 18. The charged particle beam inspection system of claim 14, wherein each said image is formed from a collection of Y said scan lines correspondingly selected from each of said Y groups of n scan lines. 19. The charged particle beam inspection system of claim 14, wherein said charged particle beam imaging apparatus comprises:a charged particle beam generator for generating a charged particle beam;a condenser lens module for condensing the generated said charged particle beam;an objective lens module for focusing the condensed said charged particle beam into a charged particle beam probe;a deflection module for scanning said charged particle beam probe over the surface of said sample secured on a sample stage;a detector module for collecting charged particles coming from said sample when it is scanned by said charged particle beam probe, and generating a detection signal accordingly; andan image forming module coupled to said detector module for receiving said detection signal and accordingly forming said voltage contrast images of said sample.
052326586	description	Referring now to the figures of the drawing in detail and first, particularly, to FIG. 1 thereof, there is seen a cross section through a fuel assembly according to the invention, which is covered laterally by walls 2 and 3 of a fuel assembly box, at the bottom by a bottom or base part and at the top by a top or cap part. A coolant, serving as a moderator, is introduced through flow openings in the bottom part, flows upward in interstices between fuel rods 4 and 5, and emerges again through flow openings in the top part. It may be advantageous to place an elongated tube 6 in the interior of the fuel assembly box. This tube 6 carries a flow of liquid coolant through it over its entire length, while the coolant flowing along the fuel rods is heated by the rods and is present in the upper part of the fuel assembly as a mixture of liquid and steam. In the box, the tube or water tube 6 assures that sufficient liquid coolant, as the moderator, will be present in the upper part of the fuel assembly as well. In the most common box, the fuel assembly has a square cross section, in which reference symbol d indicates the maximum spacing between the outer surfaces of opposite box walls, which is predetermined by the geometry in the core zone of the reactor. This geometry also determines a radius of curvature r at rounded corners of the box. The invention provides flat surfaces for the outsides of the box walls, the spacing of which have the value d. The corners are rounded in accordance with the predetermined radius r. As is typical in the prior art, the fuel rods are each disposed in rows in such a way that the minimum spacing between two adjacent fuel rods of a bundle is equal to the spacing of two fuel rods that are adjacent one another in a row parallel to one box wall. These lengthwise and crosswise rows, which are defined by the minimum fuel rod spacing, accordingly extend parallel to the box walls 2 and 3. In the exemplary embodiment of FIG. 1, the lengthwise rows and crosswise rows are each formed by 11 fuel rods. In order to keep a minimum spacing m as great as possible despite this high number of fuel rods, the spacing between the inner surfaces of the opposite box walls is increased by reducing the thickness of the box walls 2 and 3. While wall thicknesses of 3 mm have previously been typical, and even uniform wall thicknesses of 2.7 mm and 2.54 mm have been considered adequate, wall thicknesses of less than 2.4 mm, and in particular between 1.5 and 1.7 mm, are used in this case. With previously known materials, this would not have been adequate for the stability of the box. Nevertheless, this stability is attained, because the box walls are thickened in the region of the rounded corners by a reinforcement that protrudes into the interior of the box. Thicknesses between 2.5 mm and 3.0 mm and preferably 2.7 to 2.9 mm, are adequate for this thickening. These thickenings in the wall regions reduce the space available for a corner rod and the intersections of the rows of fuel rods bordering the walls 2 and 3. However, in many boxes, it is readily possible for such corner rods to be thinner than the others, which is already known. In the present box, no fuel rod whatsoever is provided at the aforementioned points of intersection of the two peripheral rows, such as at a position A. It is therefore unnecessary with the selected configuration to manufacture and use fuel rods having a different diameter in order to nevertheless assure that a predetermined minimum value for the flow cross section, or in other words a minimum spacing between the inner surfaces of the box and the adjacent fuel rods, is also adhered to in the region of the rounded corners for the coolant flowing along the vicinity of the box wall. As compared with a configuration of 9.times.9=81 fuel rods, despite the tube 6 which occupies the cross section of 3.times.3 fuel rods and despite the four missing corner rods, the present geometry still has a total number of 11.times.11-(3.times.3)-4=108 fuel rods. An in-between number of 100 fuel rods can advantageously be attained in accordance with FIG. 2. In the FIG. 2 embodiment, the distribution of the fuel rods is especially uniform, even in the corner regions. In this box, the fuel rods 4 and 5 next to the box walls are again disposed in a row parallel to the box walls, and the other fuel rods are disposed in lengthwise and crosswise rows parallel to them. However, a spacing n of the fuel rods in these rows is greater than the minimum spacing m between adjacent fuel rods. In other words, fuel rods having the minimum spacing m are located in rows that are inclined relative to the box walls. This geometry permits a configuration in which there is already no fuel rod provided in the position A. Accordingly, no fuel rod needs to be left out in order to adhere to a minimum spacing between the box wall and adjacent fuel rods. Accordingly, in its outer dimensions, the novel fuel assembly meets all of the demands specified by the geometry of the reactor core. The fuel rods themselves are distributed in a simple, clear and advantageous way over the cross section, and make optimal use of the available cross-sectional area with a view to wide spacings between one fuel rod and adjacent fuel rods or walls. The total fuel provided for one fuel assembly is distributed over a desired higher number of fuel rods, each with a correspondingly smaller diameter.
	abstract	There is provided a multilayered spectroscopic device effective to achieve in a short length of time the highly accurate fluorescent X-ray analysis of boron wherein the influence that may be brought about by the interfering X-rays and the background is sufficiently reduced and the strength of reflection of B-Kxcex1 line is sufficient. In this multilayered spectroscopic device 3, lanthanum (La), an alloy containing lanthanum as a principal component or lanthanum oxide (La2O3) is used for the reflecting layers 31 and boron is used for the spacer layers 32 and the periodic length d is chosen to be within the range of 7 to 14 nm and the film thickness ratio of the reflecting layers 31 to the spacer layers 32 is chosen to be within the range of 2/3 to 3/2. It has a total laminated film thickness t of a value sufficient to allow the strength of reflection of B-Kxcex1 line to be equal to or higher than 98% of a saturation value.
050739140	abstract	A stereoscopic X-ray apparatus is provided in which X-rays are irradiated from the two foci of a stereoscopic X-ray tube to an object to be examined so as to obtain images of the object picked-up in two directions and which permits the object to be stereoscopically displayed based on the two picked-up images. X-ray images having passed the object are picked-up by an image intensifier tube and a TV camera and stored into two frame memories. The two images output from the frame memories are alternately displayed on a display unit. At this time, the positional relation between the object and the X-ray tube and the positional relation between the object and the image intensifier tube set at the picking-up time are compared with those set in the standard state, the display positions of the two images are shifted in the right and left directions by the same distance equal to half the difference therebetween so as to adjust parallax of the two images which corresponds to the stereoscopy, thus making it possible to stereoscopically display the two images with the desired stereoscopy.
	summary
	summary
	description	FIG. 1 is a general view of a relevant part of a particle-optical apparatus in which the invention can be used. The Figure shows a particle-optical instrument in the form of a part of a column 2 of a scanning electron microscope (SEM). As is customary, an electron source in this instrument (not shown) produces a beam of electrons (the primary beam) which travels along the optical axis 4 of the apparatus. This electron beam can traverse one or more electromagnetic lenses, such as the condenser lens 6, after which the electron beam ultimately reaches the objective lens 8. This lens, being a so-called monopole lens in the present embodiment, forms part of a magnetic circuit which also includes the wall 10 of the specimen chamber 12. The objective lens 8 is used to form a primary beam focus for scanning the object 18 in the form of a semiconductor wafer which is arranged underneath the objective lens. The object 18 is scanned by moving the electron beam across the object in two mutually perpendicular directions by means of scan coils 14 which are provided in the bore of the objective lens 8. The object is arranged on an object carrier 20 which is to be described in detail hereinafter and forms part of an object stage 23. The object carrier 20 can be displaced in two mutually perpendicular directions, thus enabling the selection of a desired region of the object for examination; moreover, the object carrier 20 can be tilted relative to the object stage 23. The objective 8 thus serves as a focusing device for forming a focus of the primary beam in the vicinity of the object on the object carrier 20. The imaging in such a microscope is realized by making electrons from the primary beam land on the object, thus releasing secondary electrons from the object; these secondary electrons travel back in the direction of the lens 8. Such secondary electrons are detected by a detector 16 which is arranged in the bore of this lens. To this detector there is connected a processing unit (not shown) for activating the detector and for converting the flow of detected electrons into a signal which is suitable for forming an image of the object, for example by means of a cathode ray tube. FIG. 2 is a diagrammatic side elevation of the object carrier 20 according to the invention. The object carrier shown includes a circular support body 22 which is sufficiently large so as to carry an object in the form of a semiconductor wafer 18 to be examined. In order to arrange the wafer 18 on the support body 22 without play, the latter body is provided with three cams 26 at its circumference (two of which are shown in FIG. 2), the shape of said cams being slightly tapered in the direction of the support body in order to press the wafer in the direction of the body 22 without play. A number of support elements 28 is provided in the body 22. The desired number of support elements is dependent on the dimension of the wafer and on the expected degree of undesired vibrations in the wafer. For a wafer having a diameter of 30 cm, this number may be of the order of magnitude of thirty; however, a different number is by no means excluded. Each support element 28 is provided with a protrusion in the form of a pin 30 which is resiliently movable in the longitudinal direction of the pin as will be described in detail hereinafter with reference to FIG. 3. The free ends of the pins 30 of the system of support elements 28 are intended to stay in contact with the wafer 18. To this end, together they define a substantially flat support surface 32 which corresponds to the lower side of the wafer to be supported. For the sake of clarity, the shape error of the wafer 18 relative to a flat surface is shown in exaggerated form in FIG. 2. When the wafer 18 suffering from shape errors is arranged on the object carrier 20, the projecting pins 30 are pressed against the lower side 32 of the wafer. In order to achieve the desired effect of the invention, the displacement stroke of the pins must be so large that each pin can press against the lower side of the wafer. FIG. 3a is a sectional view of a support element 28 according to the invention. The support element shown in this Figure includes a housing 34 which defines a cylindrical cavity 36. In this cavity 36 there is arranged a cylindrical body 38 which is movable within the housing and in the direction of the common cylinder axis 40. The upper side of the housing is closed by means of a lid 42 whereas its lower side is closed by means of a closing member 44. The pin 30 which is connected to the cylindrical body projects through an opening 46 in the lid 42 in the direction of the lower side 32 of the wafer. The cylindrical body is also provided with an opening 48 which is intended to allow the passage of air during the up and down movements, so that any air trapped between the lid 42 and the cylindrical body 38 cannot interfere with the movement of the member 38; this could occur if the wafer is arranged on the object carrier in atmospheric conditions. Inside the cylindrical body 38 there is provided a coil spring 50 which presses the cylindrical body in the direction of the wafer, with the result that the pin 30 remains in contact with the wafer surface 32. The force exerted on the relevant region of the wafer by the coil spring 50 should be smaller than the force caused by the weight of the relevant region of the wafer, so that the wafer will not be pressed out of the desired position. The spring 50 bears on the closing member 44 at the lower side. It is to be noted that the support element need not include a housing so as to implement the invention; it is alternatively possible to arrange the cylindrical body 38 directly in a bore in the carrier body 22. The operation of the support element will be described in detail hereinafter with reference to FIG. 3b. When the wafer is arranged on the support elements, in each support element a force F1 is exerted on the pin 30 in the direction of the cylinder axis 40 when the pin 30 is depressed. Due to the action of the spring 50, an opposing force F2 which opposes F1 is thus produced. It is assumed that F2 acts at the center of the cylindrical body, i.e. along the cylinder axis 40. If desired, this situation can be reached by attaching the end of the spring 50 to the center of the body 38. Because the two forces F1 and F2 are not directed along the same line of action (the pin 30 is arranged so as to be eccentric relative to the cylinder axis), a moment is produced which must be compensated by a different moment in the state of equilibrium. Said other moment is produced by two reactive forces F3 and F4; F3 is applied to the upper side of the cylindrical body whereas F4 is applied to the diametrically oppositely situated lower side of the cylindrical body. The forces F1 and F2 are equal as regards magnitude, like the forces F3 and F4. The magnitude of these forces results from the requirement that the moment (F1+F2)d/2 produced by F1 and F2 should be equal to the moment (F3+F4)h/2 produced by F3 and F4. When the friction coefficient is known, the magnitude of the frictional force can be determined from the magnitude of the forces F3 and F4. The frictional force must satisfy two conditions: on the one hand, the frictional force should be smaller than a given maximum value so that the pin 30 always remains pressed against the wafer and cannot remain stuck in a lower position, irrespective of the angle of tilt of the wafer. On the other hand, the frictional force should be larger than a given minimum value so that it is large enough to counteract the tendency to vibrate of the part of the wafer supported by the relevant support element. In other words, the friction between the cylindrical body and the inner side of the housing 34 should be high enough to ensure that the pin 30, and hence the wafer 18, do not move under the influence of any vibration forces acting in the wafer. The intended effect of the invention is achieved by way of the latter choice of the magnitude of the frictional force. In that case no vibrations larger than the vibrations present in the entire construction, notably in the object carrier 20, can arise in the supported point of the wafer. The effect of the steps proposed according to the invention consist in that the support points formed by the pins 30 constitute elastic support points for macroscopic support of the wafer, which support points can follow the shape errors of the wafer; however, for motions in the nanometer range (so for the resonance vibrations) they constitute hard support points which do not allow such movements. It is to be noted that the opening 46 should be large enough to ensure that no friction of any significance is produced by the pin 30, because otherwise the friction between the cylindrical body and the inner side of the housing 34 will not be sufficiently defined. The FIGS. 4a and 4b illustrate the effect of the invention. Both Figures show an image of an object which has been formed by means of a SEM. The object consists in this case of a tin sphere having a diameter of the order of magnitude of from approximately 1 xcexcm to 10 xcexcm. Such tin spheres are provided on a wafer having a diameter of 30 cm; in FIG. 4a this wafer is supported by an object carrier according to the state of the art whereas in FIG. 4b it is supported by an object carrier according to the invention. The images show the edge of the sphere; thus, in the case of a vibration-free image a smooth edge would have to be reproduced. Comparison with the imaging scale 54 (representing a length of 50 nm) shows that in FIG. 4a the edge 52 was subject to vibrations of an amplitude of the order of magnitude of 25 nm. In FIG. 4b, i.e. the Figure relating to the invention, the same edge is subject to vibrations of an amplitude not higher than approximately 2 nm.
	abstract	A reinforced concrete containment vessel in a nuclear reactor includes a cylindrical shell having a side wall. The side wall includes an opening and a plurality of reinforcing bars, at least one of which is interrupted at the side wall opening. A reinforcing plate having an opening is located in the cylindrical shell so that the reinforcing plate opening is aligned with the side wall opening and the interrupted reinforcing bars are connected to the reinforcing plate. Reinforcing bar terminators connect the reinforcing bars to the reinforcing plate.
	description	This present application is a divisional application of co-pending U.S. application Ser. No. 16/662,523, filed 24 Oct. 2019, which claims priority to provisional application 62/749,875, filed Oct. 24, 2018, and which is a continuation in part (CIP) of U.S. application Ser. No. 15/488,983, filed Apr. 17, 2017, which claimed priority to U.S. application Ser. No. 14/190,389, filed Feb. 26, 2014, which has issued as U.S. Pat. No. 9,636,524 on May 2, 2017, which claimed priority to U.S. application Ser. No. 13/532,447, filed on Jun. 25, 2012, now abandoned, which claimed priority to provisional U.S. patent application 61/571,406 filed Jun. 27, 2011. This invention is in the technical area of apparatus and methods for Boron Neutron capture therapy for cancer. Boron Neutron Capture Therapy (BNCT) is not new in the art, as thermal neutrons have been used for cancer therapy for the destruction of cancer tumors. These neutrons interact with boron-10 that has been placed at the cancer site. The neutrons interact with the boron to produce fission events whereby alpha particles and lithium nuclei are created. These massive ionized particles are then released, destroying the chemical bonds of nearby cancer tumor cells. At present the neutrons created in a reactor or accelerator pass through a moderator, which shapes the neutron energy spectrum suitable for BNCT treatment. While passing through the moderator and then the tissue of the patient, the neutrons are slowed by collisions and become low energy thermal neutrons. The thermal neutrons undergo reactions with the boron-10 nuclei at a cancer site, forming compound nuclei (excited boron-11), which then promptly disintegrate to lithium-7 and an alpha particle. Both the alpha particle and the lithium ion produce closely spaced ionizations in the immediate vicinity of the reaction, with a range of approximately 5-9 micrometers, or roughly the thickness of one cell diameter. The release of this energy destroys surrounding cancer cells. This technique is advantageous since the radiation damage occurs over a short range and thus normal tissues can be spared. Gadolinium can also be considered as a capture agent in neutron capture therapy (NCT) because of its very high neutron capture cross section. A number of gadolinium compounds have been used routinely as contrast agents for imaging brain tumors. The tumors have absorbed a large fraction of the gadolinium, making gadolinium an excellent capture agent for NCT. Therefore, GNTC may also be considered as a variation in embodiments of the present invention. The following definitions of neutron energy ranges, E, are used frequently by those skilled in the art of producing and using neutrons for medical, commercial and scientific applications: Fast (E>1 MeV), Epithermal (0.5 eV<E<1Mev) and Thermal (E<0.5 eV) neutrons. BNCT has the potential to treat previously untreatable cancers such as glioblastoma multiforme (GBM). In the US brain tumors are the second most frequent cause of cancer-related deaths for males under 29 and females under 20. GBM is nearly always fatal and has, until now, no known effective treatment. There are approximately 13,000 deaths per year due to primary brain tumors. If conventional medicine is used where the glioblast is excised, new tumors almost invariably recur, frequently far from the original tumor site. Effective radiation therapy, therefore, must encompass a large volume and the radiation must be uniformly distributed. Conventional radiation treatment is usually too toxic to be of use against GBM. For distributed tumors, effective radiation therapy must encompass a larger volume and the radiation must be uniformly distributed. This is also true of liver cancers. The liver is the most common target of metastases from many primary tumors. Primary and metastatic liver cancers are usually fatal, especially after resection of multiple individual tumors. The response rate for nonresectable hepatocellular carcinoma to traditional radiation treatment or chemotherapy is also very poor. However, recent results indicate that the thermal neutron irradiation of the whole liver with a 10B compound, to be bombarded with low-energy neutrons, could be a way to destroy all the liver metastases. Recent research in BNCT has shown that neutron capture therapy can be used to treat a large number of different cancers. BNCT has been found to be effective and safe in the treatment of inoperable, locally advanced head and neck carcinomas that recur at sites that were previously irradiated with traditional gamma radiation. Thus, BNCT could be considered for a wider range of cancers. BNCT holds such promise because the dose to the cancer site can be greatly enhanced over that produced by y-radiation sources. This is a consequence of the fact that the neutron-boron reaction produces the emission of short-range (5-9 um distance) radiation, and consequently normal tissues can be spared. In addition, boron can achieve a high tumor-to-brain concentration ratio, as much as ten or more, thereby preferentially destroying abnormal tissue. BNCT has been tested using either nuclear reactors or accelerators to produce the neutrons, which are not practical or affordable for most clinical settings. Reactors also do not produce an ideal neutron spectrum and are contaminated with y-radiation. Fusion generators produce fast neutrons from the deuterium-deuterium (DD) or the deuterium-tritium (DT) reactions and are, in general, smaller and less expensive than accelerators and reactors. Fast neutrons thus produced must be moderated or slowed down to thermal or epithermal neutron energies using, for example, water or other hydrogen bearing materials. The fusion neutron generator has three basic components: an ion source, an electron shield and an acceleration structure with a target. The ions are accelerated from the ion source to usually a titanium target using a high voltage potential of between 40 kV to 200 kV, which can be easily delivered by a modern high voltage power supply. An electron shield is usually disposed between the ion source and the titanium target. This shield is voltage biased to repel electrons being generated when the positive D+ ions that strike the titanium target. This prevents these electrons from striking the ion source and damaging it due to electron heating. The target uses a deuterium D+ or tritium T+ absorbing material such as titanium, which readily absorbs the D+ or T+ ions, forming a titanium hydride. Succeeding D+ or T+ ions strike these embedded ions and fuse, resulting in DD, DT or TT reactions and releasing fast neutrons. Prior attempts at proposing fusion generators required the use of the DT reaction with the need for radioactive tritium and high acceleration powers. High yields of fast neutrons/sec were needed to achieve enough thermal neutrons for therapy in a reasonable length of time of therapy treatments. These prior schemes for achieving epithermal neutron fluxes are serial or planar in design: a single fast neutron generator is followed by a moderator, which is followed by the patient. Unfortunately, since the neutrons are entering from one side of the head, the planar neutron irradiation system leads to a high surface or skin dosage and a decreasing neutron dose deeper into the brain. The brain is not irradiated uniformly, and cancer sites have lower thermal neutron dosage the further they are from the planar port. A conventional planar neutron irradiation system 14 and its operation is shown in FIG. 1 labeled Prior Art. Conversion of fast neutrons 22 to thermal neutrons 30 takes place in a series of steps. First the fast neutrons 22 are produced by a cylindrical fast neutron generator 20 and then enter a moderating means 18 where they suffer elastic scatterings (collisions with nuclei of the moderating material's atoms). This lowers the fast neutrons to epithermal neutron 24 energies. A mixture of epithermals 24 and thermal neutrons 30 are emitted out of a planar port 16 and then enter the patient's head 26. The epithermal neutrons 24 are moderated still further in the patient's brain and moderated further to thermal neutrons, finally being captured by the boron at the tumor site. The fission reaction occurs, and alpha and Li-7 ions are released, destroying the tumor cells. The epithermal and thermal neutrons reach the patient's head through a planar port 16 formed from neutron absorbing materials that form a collimating means 28. The thermal and epithermal neutrons strike the patient's head on one side, and many neutrons escape or are not used. One escaping neutron 38 is shown as representative. This is an inefficient process requiring a large number of fast neutrons to be produced in order to produce enough thermal neutrons for reasonable therapy or treatment times (e.g. 30 min). To achieve higher yields of fast neutrons the planar neutron irradiation system 14 requires that one use either the DD fusion reaction with extremely high acceleration powers (e.g. 0.5 to 1.5 Megawatts) or the DT reaction which has an approximate 100-fold increase in neutron yield for the same acceleration power. The use of tritium has a whole host of safety and maintenance problems. Tritium gas is radioactive and extremely difficult to eliminate once it gets on to a surface. In the art of producing fast neutrons this requires that the generator be sealed and have a means for achieving a vacuum that is completely sealed. The generator head cannot be easily maintained and usually its lifetime is limited to less than 2000 hours. This reduces the possible use of this generator for clinical operation since the number of patients who could be treated would be small before the generator head would need replacement. On the other hand, the use of the DD fusion reaction allows one skilled in the art to use an actively-pumped-vacuum means with roughing and turbo pumps. The generator can then be opened for repairs and its lifetime extended. This makes the DD fusion reaction neutron generator optimum for clinical use. The downside for the DD fusion reaction is that high acceleration powers are required to achieve the desired neutron yield required by prior art methods. Improving the efficiency of producing the right thermal neutron flux at the cancer site is imperative for achieving BNCT in a clinical and hospital setting. In one embodiment of the invention a Boron neutron cancer treatment system is provided, comprising a secondary moderator having a central treatment chamber for a subject, and eight substantially identical neutron generators, each comprising a pre-moderator block of moderating material having an upper surface, a lower surface, a first and a second end, opposite side surfaces angled inward by forty-five degrees along at least a portion of the height, a first length, a first width substantially less than the first length, and a first thickness, a cylindrical acceleration chamber having a first diameter substantially the first width of the pre-moderator block, sealed at one end to the upper surface of the pre-moderator block adjacent the first end of the pre-moderator block, with a vertical axis perpendicular to the upper surface, the acceleration chamber having a height and a top cover at a second end away from the pre-moderator block, a vacuum pump engaging the acceleration chamber at a right angle to the vertical axis, evacuating the acceleration chamber to a moderately high vacuum, a plasma ion chamber opening into the acceleration chamber through an ion extraction iris through the top cover of the acceleration chamber on the vertical axis of the acceleration chamber, a gas source providing deuterium gas to the plasma ion chamber, a microwave energy source ionizing the gas in the plasma ion chamber, a cylindrical primary isolation well extending a substantial distance into the pre-moderator block from the upper surface, centered on the vertical axis of the acceleration chamber, a secondary isolation well substantially in a shape of a hollow cylinder surrounding the primary isolation well, to a depth somewhat less than the substantial distance of the primary isolation well, within the first diameter of the acceleration chamber, a water-cooled titanium target disk having a target surface orthogonal to the axis of the acceleration chamber, the target disk having a diameter substantially smaller then a diameter of the isolation well, positioned at a lower extremity of the isolation well, the target disk biased to a substantial negative DC voltage, and electrically grounded metal cladding covering all otherwise exposed surfaces of the pre-moderator block. The eight neutron generators are positioned around the secondary moderator with the axis of each acceleration chamber passing through the center of the treatment chamber, and with the angled sides of the neutron generators fully adjacent. In one embodiment the system further comprises eight substantially rectangular spacing blocks of moderator material, one spacing block placed between each adjacent neutron generator with sides of the spacing blocks fully adjacent with the angled sides of the neutron generators. Also, in one embodiment the secondary moderator is shaped to fill all volume between the neutron generators and the central treatment chamber. Also, in one embodiment the secondary moderator is a block or blocks of solid moderator material. In one embodiment the secondary moderator is a container filled with heavy water. And in one embodiment the secondary moderator is a container filled with granulated moderator material. In the following descriptions reference is made to the accompanying drawings that form a part hereof, and in which are shown by way of illustration specific embodiments in which the invention may be practiced. It is to be understood that other embodiments may be utilized, and structural changes may be made without departing from the scope of the present invention. Uniform Delivery of Thermal Neutrons to the Cancer Sites To achieve extremely high thermal neutron fluxes uniformly distributed across a patient's head, for example, a hemispherical geometry is used in one embodiment of the invention. This unique geometry arranges fast neutron sources in a circle around a moderator whose radial thickness is optimized to deliver a maximum thermal neutron flux to a patient's brain. This embodiment produces a uniform thermal neutron dose within a factor of 1/20th of the required fast neutron yield and line-voltage input power of a conventional planar neutron irradiation system. This arrangement permits using a relatively safe deuterium-deuterium (DD) fusion reaction (no radioactive tritium) and commercial high voltage power supplies operating at modest powers (50 to 100 kW). FIG. 2 is a cross sectional view of a hemispheric neutron irradiation system 36 according to one embodiment of the invention. Multiple fast neutron generators 68 surround a hemispheric moderator 34, which in turn surrounds the patient's head 26. Titanium targets 52 are distributed around the perimeter of the hemispheric moderator 34. Surrounding the moderator 34 and the fast neutron generators 68 is a fast-neutron reflector 44. In the moderator 34, moderating material such as 7LiF, high density polyethylene (HDPE), and heavy water are shaped in a hemisphere that is shaped around the head of the patient. The optimum thickness of the hemispheric moderator for irradiation purposes is dependent upon the material's nuclear structure and density. FIG. 3 shows a perspective view of a patient 58 on a table 54 with the patient's head inserted into hemispheric irradiation system 36. The patient 58 lies on the table 54 with his head inserted into hemispheric moderator 34. Surrounding the moderator is neutron reflecting material 44, such as lead or bismuth. Referring again to FIG. 2, fast neutrons 22 are produced by fast neutron generators 68. Generators 68 are composed of titanium targets 52 and ion sources 50. Ion beams are produced by ion sources 50 and accelerated toward titanium targets 52 which are embedded in hemispheric moderator 34. A DD fusion reaction occurs at the target, producing 2.5 MeV fast neutrons 22. The fast neutrons 22 enter the moderator 34 wherein they are elastically scattered by collisions with the moderator atom's nuclei. This slows them down after a few collisions to epithermal neutrons 24 energies. These epithermal neutrons 24 enter the patient's head 26 wherein they are moderated further to thermal neutron 30 energies. These thermal neutrons 30 are then captured by boron-10 nuclei at the cancer site, resulting in a fusion event and the death of proximal cancer cells. Fast neutrons 22 are emitted isotropically from titanium target 52 in all directions. Outwardly traveling fast neutrons 42 are reflected back (reflected neutron 48) by fast neutron reflector 44, while inwardly traveling fast neutrons 40 are moderated to epithermal energies and enter the patient's head 26, where further moderation of the neutrons to thermal energies occurs. A shell of protective shielding 56 is also shown in FIG. 2. In some embodiments, this may be necessary for shielding both the patient and the operator from excessive irradiation due to neutrons, x-rays and gamma radiation. The shielding can be made of a variety of materials depending upon the radiation components one wishes to suppress. In some embodiments, fast neutron reflector 44 is made of lead or bismuth. The fast neutron reflector also acts as a shielding means to reduce emitted gamma rays and neutrons from the hemispherical neutron irradiation system 36. As one skilled in the art will realize, gamma-absorbing or other neutron reflector means can be placed in layers around the hemispherical neutron irradiation system 36 to reduce spurious and dangerous radiation from reaching the patient 58 and the operator. Hemispheric moderator 34, fast neutron reflector 44 and head 26 act together to concentrate the thermal neutrons in the patient's head. The patient's head and the moderator 34 act in concert as a single moderator. With a careful selection of moderating materials and geometry, a uniform dose of thermal neutrons can be achieved across the patient's head and, if a boron drug is administered, a large and uniform therapeutic ratio can be achieved. The invention gives a uniform dose of thermal neutrons to the head while minimizing the fast neutron and gamma contributions. The required quantity of fast neutrons to initiate this performance is reduced compared to that of prior art planar neutron irradiation systems (see FIG. 1). A cross section perspective view of the hemispheric neutron irradiation system 36 in an embodiment of the invention is shown in FIG. 4. This cross-section view is of a radial cut directly through the patient's head 26 and hemispherical neutron irradiation system 36. As shown in this embodiment, ten fast-neutron generators 68 composed of ion sources 50 with titanium targets 52 are radially surrounding the hemispheric moderator 34 and the patient's head 26. The titanium target 52 in this embodiment is a continuous belt of titanium surrounding the moderator 34. The titanium targets can also be segmented, as was shown in FIG. 2. The ion sources in this embodiment are embedded in fast neutron reflector 44. There are a number of materials one could select for the moderator 34 to achieve maximum thermal neutron flux at the patient's head 26. The performance of HDPE, heavy water (D2O), graphite, 7LiF, and AlF3 was analyzed using the Monte Carlo Neutral Particle (MCNP) simulation. In general, there is an optimum thickness for each moderator material that generates the maximum thermal flux at the patient's head (or other body part or organ). The thermal neutrons/(cm2-s) was calculated for these materials as a function of moderator thickness d3, where d4=25 cm, and fast neutron reflector 44 is d1=50 cm thick and is made of lead. As in all our calculations, the combined fast neutron yield striking the area from all the fast neutron generators 68 is assumed in the MCNP to be 1011 n/s. The optimum thickness, range of thicknesses and maximum thermal neutron flux (E<0.5 eV) are given in Table I for various moderator materials. These are approximate values given to help determine the general dimensions of the moderator. TABLE IModerator ThicknessModeratorOptimumRange of Maximum FluxMaterialThickness d3 (cm)thickness d3 (cm)(n/cm2-sec)HDPE 6 4-10 7 × 108D2O15 9-25 2 × 108Graphite2019-20 9 × 1077LiF2520-30 3 × 107AlF33020-401.5 × 107 The calculation of the therapeutic ratio is also important and depends upon the organ in question (brain, liver) and the body mass of the patient. Although HDPE gives the highest flux, it gives a lower therapeutic ratio compared to 7LiF. The designer is expected to do calculations similar to this to determine the optimum geometry for the neutron irradiation system. The MCNP simulation was used to determine the delivered dose and therapeutic ratio to the patient 58 and compare it to a planar neutron irradiation system. In one simulation, moderator 34 is composed of 7LiF whose thickness is d3=25 cm. The inner diameter of the moderator (hole for head) is d4=25 cm. The spacing between hemispheric fast neutron reflector 44 and hemispheric moderator 34 is d2=10 cm. The head is assumed to be 28 cm by 34 cm. Fast neutron reflector 44 is made of d1=20 cm thick lead in one embodiment. Thicker values of d1 increase the tumor dose rate. At a thickness of 10 cm, the tumor dose rate is about one-half the value at a thickness of 50 cm. Fast neutron generators 68 are assumed to emit a total yield of 1011 n/sec. The combined titanium targets 52 give a total neutron emission area of 1401 cm2. In the MCNP simulation BPA (Boronophenylalanine) was used as a delivery drug. The concentration of boron in the tumor was 68.3 μg/gm and in the healthy tissue was 19 μg/gm. The calculated neutron dose rates in Gy-equivalent/hr are plotted in FIG. 5 as a function of distance from the skin to the center of the head. The calculated dose rates are comparable to those used for gamma radiotherapy, typically 1.8 to 2.0 Gy per session. For the same dosage, at a rate of 3 Gy-equivalent/hr, the session length would be from 30 to 40 min. long. These session times are considered reasonable for a patient to undergo. For this simulation, the therapeutic ratio for the hemispherical neutron irradiation system is plotted in FIG. 6 as a function of distance from the skin to the center of the skull. The therapeutic ratio is defined as the delivered tumor dose divided by the maximum dose to healthy tissue. A therapeutic ratio of greater than 3 is considered adequate for cancer therapy. The conventional planar neutron irradiation system requires larger fast-neutron yields (1012 to 1013 n/s) to achieve equivalent dose rates and therapeutic ratios. In FIG. 5, a planar neutron irradiation system 14 of FIG. 1 is compared with that of a hemispheric neutron irradiation system 36 (FIGS. 2, 3, 4) in one embodiment of the present invention, using the same source of fast neutrons (1011 n/s). As can be seen from FIG. 5, the hemispherical neutron irradiation system (called radial source in FIG. 5) achieves a dose rate of about a factor of 20 over that of the conventional planar neutron irradiation system 14. The planar geometry needs a fast neutron source of 2×1012 n/s to achieve the same results. Indeed, if a DD fusion generator is used, then the planar source requires a factor of 20× increase in wall-plug power or 2.0 MW, a prohibitively large power requirement. In addition, as can be seen from FIG. 5, over a ± 5 cm distance across the head center, hemispheric neutron irradiation system 36 has less than a 10% variation in dosage. A uniform dose rate is crucial for the treatment of GBM, where we want to maintain a maximum therapeutic ratio and tumors may have distributed themselves across the brain. Hemispherical neutron radiation system 36 in embodiments of the invention also gives a more uniform therapeutic ratio (FIG. 6) across the brain. The ratio is more uniform for the radial source and requires only 1/20th of the fast neutron yield of the planar source (FIG. 1). Other materials can be used for hemispheric moderator 34 in alternative embodiments. As those skilled in the art will know, high density polyethylene (HDPE), heavy water (D2O), Graphite and 7LiF can also be used. In addition, combinations of materials (e.g. 40% Al and 60% AlF3) can also be used. Different thicknesses d1 of moderator can be used to optimize the neutron flux and give the highest therapeutic ratio. The term “neutron generator or source” is intended to cover a wide range of devices for the generation of neutrons. The least expensive and most compact generator is the “fusion neutron generator” that produces neutrons by fusing isotopes of hydrogen (e.g. tritium and deuterium) by accelerating them together using modest acceleration energies. These fusion neutron generators are compact and relatively inexpensive compared to linear accelerators that can produce directed neutron beams. Other embodiments depend upon the selection of the plasma ion source that is used to generate the neutrons at the cylindrical target. These are (1) the RF-driven plasma ion source using a loop RF antenna, (2) the microwave-driven electron cyclotron resonance (ECR) plasma ion source, (3) the RF-driven spiral antenna plasma ion source, (4) the multi-cusp plasma ion source and (5) the Penning diode plasma ion source. All plasma ion sources can be used to create deuterium or tritium ions for fast neutron generation. Cylindrical Irradiation System for the Liver and Other Cancer Sites. FIGS. 7A and 7B shows another embodiment of the invention which uses a cylindrical geometry to irradiate other organs and parts of patient 58, such as the liver 76. FIG. 7A is a cross sectional view of cylindrical neutron irradiation system 62 and FIG. 7B is a perspective view of the same embodiment. In this embodiment eight fast-neutron generators 68 surround a cylindrical moderator 46. These generators 68 all emit their fast neutrons at the surface of the moderator. A cylindrical fast neutron reflector 44 surrounds the cylindrical moderator 46. As in the case of the hemispheric moderator 34, the cylindrical moderator 62 can be composed of well-known moderating materials such as 7LiF, high density polyethylene (HDPE), and heavy water. These are shaped in a cylinder that surrounds the patient. The optimum thickness of the cylinder moderator for neutron capture purposes is dependent upon the material nuclear structure and density. In this embodiment, fusion neutron generators are used to supply the fast neutrons. Fast neutron generator 68 is composed of a titanium target 52 and an ion source 50 as before. The titanium targets are contiguous to the cylindrical moderator 46. Ion beams 60 are accelerated using a DC high voltage (e.g. 100 kV) to the titanium target 52 where fast neutrons are produced from the DD fusion reaction. The fast neutrons are emitted isotropically from the titanium targets 52 on the moderator, some moving out to the fast neutron reflector 44 and others inwardly to be moderated immediately to epithermal or thermal energies. Those reflected come back into the cylindrical moderator 46 where they are moderated to epithermal and thermal energies, making their way finally to the patient 58. Cylindrical neutron irradiation system 62 permits uniform illumination of a section of the patient's body (e.g. liver) as compared to the conventional planar neutron irradiation system. In the case of the brain, the body itself acts as part of the moderation process, thermalizing epithermal neutrons coming in from cylindrical moderator 46. As one skilled in the art will realize, other cancers, such as throat and neck tumors, can be effectively irradiated by a hemispherical neutron irradiation system such as system 36. The thickness and material content of the moderator can be adjusted to maximize the desired energy of the neutrons that enter the patient. For example, for throat and neck tumors, the moderator can be made of deuterated polyethylene or heavy water (D2O) to maximize thermal neutron irradiation of the tumor near the surface of the body. For deeper penetration of the neutrons one might make the moderator out of AlF3, producing epithermal neutrons. These would be optimum for reaching the liver and producing uniform illumination of that organ. Segmented Moderator In yet another embodiment, fast neutron sources with segmented moderators may be individually moved to achieve a uniform dose across the liver or other cancer site. This geometry produces a uniform thermal neutron dose with a factor of between 1/10th and 1/20th of the required fast neutron yield and line-voltage input power of previous linear designs. This again permits the use of the relatively safe deuterium-deuterium (DD) fusion reaction (no radioactive tritium) and off-the-shelf high voltage power supplies operating at modest power (<100 kW). A segmented neutron irradiation system 70 in an embodiment of the invention is shown in FIG. 8. Ten fast neutron generators 68, each with a wedge-shaped moderator 74, surround the patient 58. The exact shape of each moderator can vary and can be of other geometries. Each generator and moderator pair can be moved independently of the others to achieve uniformity of the neutron flux across the liver, organ, or body part. In between the wedge-shaped moderators 74 more moderating material (“filler moderating material” 72) is inserted, forming a large single moderator. The “filler” moderating material 72 can be heavy water or powered moderating materials such as AlF3. Pie shaped fillers of moderating material can also be fitted into the spaces between the wedge-shaped moderator 74. Since neutrons scatter easily, there can be some space between the wedge-shaped moderators 74 and the pie shaped fillers without undue loss of neutron moderating efficiency. The neutron yield from and the position of each fast neutron generator 68 can be adjusted to achieve uniformity across the liver or body part. The position and the neutron yield of the generator can be varied to achieve the desired radiation dose at a particular location in the patient's body. Since the cancer can be located in any part of the body, this benefit can be particularly useful for optimizing the dose at the cancer site. Surrounding the entire fast neutron/moderator system is a cylindrical fast neutron reflector 44. Fast neutrons are produced by the fast neutron generators 68 and enter the moderators 74 where they are elastically scattered by collisions with the moderator atoms' nuclei, slowing them down after a few collisions to epithermal energies. As in the other embodiments, these epithermal neutrons enter the patient 58 and liver 76, wherein they are moderated further to thermal neutron energies. The invention in various embodiments provides a uniform dose of thermal neutrons to the liver, organ or body part while minimizing fast neutron and gamma contributions. The required number of fast neutrons (e.g. 2×1011 n/s) to initiate this performance is again reduced compared to that (e.g. 2×1013 n/s) needed for the planar neutron irradiation system of the prior art. Another embodiment of the segmented design is shown in FIG. 9. The shape of the neutron irradiation system 78 is elliptical, with six sources of fast neutrons shown as distributed targets embedded in the inside elliptical moderator 96. Fast neutrons 22 are emitted isotropically in all directions. Those fast neutrons 22 moving outwardly are reflected back (see arrow 48) by fast neutron reflector 44, while fast neutrons traveling inwardly 22 are moderated to epithermal energies and enter the liver 76, where further moderation of the neutrons to thermal energies occurs. The inside elliptical moderator 96, outside elliptical moderator 98, reflector 44 and patient's body 58 act together to moderate and concentrate the thermal neutrons into the patient's liver 76. With a careful positioning of the moderators and fast neutron sources 90, 92, 94, a uniform dose can be achieved across the patient's liver, and, with a boron drug administered to the tumor, an excellent therapeutic ratio can be achieved. Elliptical neutron irradiation system 78 in FIG. 9 is a simplified cross-sectional view of the patient 58 inside the elliptical moderator 96. This cross-section view is of a radial cut directly through the patient's torso and the moderator and fast neutron generator system. To maintain visual simplicity, only the titanium targets are shown and not the ion sources. Thus, six fast-neutron sources are represented by three flat titanium targets 90, 92, 94. The rest of the fast neutron generator is not shown. Other components (e.g. plasma ion source) are neglected in the analysis. The wedge-shaped moderators 74 (used in FIG. 8) are also not shown in FIG. 9. For a simple simulation of the neutron irradiation system, the targets 90, 92, 94 are the sources of the fast neutrons and are arranged in an elliptical material 96 (e.g. AlF3, LiF). The effect of the moderating material 96, the fast neutron reflector 44 and the patient's body 58 were calculated using a Monte Carlo N-particle (MCNP5) transport code to determine how fast the neutrons were converted to thermal neutrons in the neutron irradiation system. Dosage calculations were made along a central axis of the liver. The fast neutron sources (titanium targets) are 2 cm×2 cm in area, each producing 1011/N n/s, where N is the number of sources. The human body 58 dimensions are 35.5 cm along the major axis and 22.9 cm along the minor axis. The inner elliptical moderator 96 is made of 7LiF and 10 cm thick, while the outer moderator 98 is made of AlF3 and 40 cm thick. The fast neutron reflector 44 is made of lead 50 cm thick. Boron-10 concentration is 19.0 μg/g in the healthy tissue and 68.3 μg/g in the tumor. The six sources are located in cms at: (−15, 18.06, 0) (−15, −18.06, 0) (−17, 17, 0) (−17, −17, 0) (0, 15.85, 0) (0, −15.85, 0). These measurements are made along the axis of the liver 76 from the point (−15, 0, 0) to (−5, 0, 0). In the x-direction, the first two sources 90 are centered about the left edge of the liver shown in FIG. 9, the two sources 92 are centered about the edge of the body, and the third two 94 are located above and below the origin. The origin is shown in FIG. 9 as a small cross + at the center of the body in the plane of the liver. FIG. 10 shows the therapeutic ratio for a large single dose, and the therapeutic ratio for multiple small doses (where the photon dose to healthy tissue is not included) plotted as a function of distance along the axis of the liver. The photon dose can be neglected if there is some amount of time between doses. Many of the body's healthy cells can self-repair and recover between doses. The expected therapeutic ratio is between these two curves when there is fractionation into multiple doses. In this simulation, BPA was again used as the delivery drug with the concentration of boron in the tumor at 68.3 μg/gm and in the healthy tissue at 19 μg/gm. FIG. 11 indicates that the goal of having an extremely uniform dosage to the tumor has been achieved, with about ± 6% variation along the x-dimension. The calculated dose rates are comparable to those used for gamma radiotherapy, typically 1.8 to 2.0 Gy-equivalent per hour if we increase the total neutron yield to 2×1011 to 3×1011 n/s. Thus, at approximately 2×1011 to 3×1011n/s it is possible to obtain a therapeutic ratio and uniform dosage to a tumor. Approximately 10 to 20 treatments of 30 to 40 minutes would be required, with a good therapeutic ratio, uniformity of dosage, and the opportunity for healthy tissue repair between treatments. Once again, the planar neutron irradiation systems require high fast neutron yields to drive them. In one prior art system known to the inventors a fast neutron source of 3×1013 n/s is needed to obtain realistic treatment time of ˜1-2 hours. Using a D-T neutron source with a yield 1014 n/s, acceptable treatment times were obtained (30 to 72 minutes with single beam and 63 to 128 minutes with 3 beams of different direction). But these are impossible yields to achieve with realistic wall plug powers. Instead of 50 to 100 kW for the hemispheric and cylindrical neutron irradiation systems, it would take a minimum of 0.5 MW to achieve adequate yield for the planar geometry with a DT generator. These are high powers for clinics and hospitals. As one skilled in the art knows, other cancers, such as throat and neck tumors, can be effectively irradiated by the neutron irradiation system. The thickness and material content of the moderator can be adjusted to maximize the desired energy of the neutrons that enter the patient. For example, for throat and neck tumors, the moderator can be made of deuterated polyethylene or heavy water (D2O) to maximize thermal neutron irradiation of the tumor near the surface of the body. For deeper penetration of the neutrons one might make the moderator out of AlF3, producing epithermal neutrons. These would be optimum for reaching the liver and producing uniform illumination of that organ. Modular Generators Introduction As is shown in FIGS. 8 and 9, multiple modular generators may be encased in moderator material and may be arrayed to maximize thermal neutron flux at a cancer tumor location. Fast 2.5 MeV neutrons must be slowed (moderated) to energies (usually epithermal) that will penetrate to the cancer site without too many neutrons being lost in their travel to the cancer via capture by healthy tissue. These modular generators act as independent neutron sources and each may be optimized by adjustment of each individual beam's energy, direction and intensity. The modular generators can be arranged to fit a site in a particular subject's component location and structure. This is true also for cancer tumor location. The energy of the neutrons can also be adjusted by adding or subtracting moderator material. This can be done more easily than with a single beam LINAC or reactor, which usually has a fixed beamline that is integral to the neutron source. In the prior art some adjustment can be made, but the DD fusion generator in embodiments of the invention, being much smaller, can have more degrees of freedom in direction, intensity and moderation. This has an added benefit of aiding physicians in tailoring neutron radiation to the patient's cancer. Comparison to Linear Accelerators and Reactors. Modular generators in various embodiments of the present invention may also form and be part of the mechanical structure of a cancer irradiation system. This has an added benefit of moving the neutron sources as close as possible to the cancer site and the diseased body part, resulting in efficient use of the neutron source. The neutrons are being emitted in a 4π solid angle from the modular generators, so the closer to cancer site, the more of the fast neutron flux is being utilized. Linear accelerators (LINACs), which are somewhat collimated, are further from the cancer site and cannot provide this advantage. Compared to a linear accelerator, which can be several meters long or longer and may include large microwave power sources, the DD fusion sources in embodiments of the invention are less than one meter long and comprise compact microwave sources that can either be solid state microwave sources or small, inexpensive, single microwave oven magnetrons. The accelerator structure in embodiments of the invention is compact and includes a pre-moderator 118 that adds only from 5-10 cm of High-Density Polyethylene (HDPE) or 15-20 cm of polytetrafluoroethene (PTFE) Teflon to produce a first stage of neutron beam tailoring. The pre-moderator in these embodiments is an integral part of each modular generator, as is taught below with reference to several figures. In alternative embodiments other pre-moderator materials can be used such as AlF3, MgF2, 7LiF, and Fluental (trade name). Smaller, Nontoxic, Less Complex Targets for Neutron Production The modular DD fusion generator 118 in embodiments of the present invention uses a small titanium target (e.g. a 5 cm diameter disk of titanium backed by water-cooled copper fins) to produce neutrons. The target is supported directly on the pre-moderator, which is an integral part of the apparatus in this application, termed a modular generator. Linacs and other methods in the conventional arts use larger or toxic targets that require complex cooling and rotation. For example, the neutron source used by Neutron Therapeutics has a 2.6 MeV electrostatic proton accelerator and a rotating, solid lithium target for generating neutrons. In that prior-art process the Lithium becomes radioactive and toxic, and when exposed to air, it disintegrates. This prior art source has a large target chamber housing a large Li disk which is rotated in a powerful 2.8 MeV proton beam produced by a large accelerator. The Lithium wheel is roughly 2 meters in diameter and has been divided into pie-shaped sections that are removed by mechanical robotic means. In embodiments of the present invention, the Ti target is a relatively small diameter (˜5 cm) and is typically attached with 6-8 screws to the pre-moderator block and is sealed to the block with a Viton “O” ring. The Ti targets in embodiments of the invention can be easily manually removed and replaced. They also have a long lifetime and have been tested for over 4000 hours with no failures. Nuclear reactors are large structures with a substantial amount of shielding (water and concrete) and cooling systems to maintain the hot reactor core. Reactors provide primarily thermal neutrons that must be raised up in energy using an energy multiplier, and then the neutron beam must be improved to IAEA standards to produce epithermal neutrons with minimal gamma radiation. Optimizing Neutron Energy for Penetration and Minimum Damage to Healthy Tissue For tumors at depths in a subject of 3 cm or more, a goal for the moderator is to provide a neutron beam that has its energy clustered about 10 keV at the skin, in order to provide sufficient energy to penetrate a minimum of several centimeters into a human target while avoiding higher energies that are more damaging to human tissue. High conversion to epithermal energies occurs in HDPE at a thickness of approximately 5 cm, but it also produces a high yield of thermal neutrons and 2.2 MeV gammas that can damage the healthy tissue at the skin. Modular Generators In embodiments of the present invention modular generators are very important components. The modular generator combines multiple functions that were separate functions in the prior art. These integrated functions include both neutron production and beam tailoring. FIG. 12A is a perspective view of an individual modular generator 118 in an embodiment of the invention. FIG. 12B is a cross section of the modular generator 118 of FIG. 12A taken along an axis of an acceleration chamber 100 for ion beam generation and containment, and at a right angle to the axis of a turbo vacuum pump 124 that is part of the modular generator 118. FIG. 12C is a cross section of the modular generator 118 of FIG. 12A taken along the axis of the acceleration chamber 100, and along the axis of the turbo vacuum pump 124, at a right angle to the section of FIG. 12B. Each modular generator 118 can operate independently of the other modular generators and each possesses all required components to generate neutrons. Further, the various modular generators may have pre-moderators shaped to engage other building blocks of a project, such as adjacent generators or spacing moderators, as is described in enabling detail below. Viewed as in FIGS. 12A, B and C, each modular generator 118 comprises a pre-moderator 108 that is made of material known to moderate energy of energetic neutrons. In most embodiments the pre-moderator is a solid block of material, with a rather complicated shape for certain purposes. Modular generator 118 has three key elements: (1) a deuterium ion source 102, (2) an acceleration chamber 100, through which deuterium ions may be accelerated, and (3) a titanium target 106 (shown in FIGS. 12B and 12C) that is bombarded by the deuterium ions to produce high-energy neutrons. The deuterium ion source 102 has an attached microwave source 160, and microwave slug tuners 172, connected by a cable 178. Deuterium gas is leaked slowly into a plasma ion chamber 174 at the upper end of the acceleration chamber, where microwave energy ionizes the gas, creating deuterium D+ ions. The gas is ionized by microwave energy, and Deuterium (D+) ions are created and accelerated out through an ion extraction iris 138 into acceleration chamber 100, and through an electron suppression shroud 180 which deflects back-streaming electrons from being accelerated back into the plasma source, which could damage the apparatus. Electrons are being created by collisions of the D+ ions in the deuterium gas that are being created in the acceleration chamber. The deuterium ions are positively charged, and target 106 is negatively charged to a level of from 120 kV to 220 kV, and the D+ ions are strongly attracted to negatively biased target 106. Acceleration chamber 100 is connected to a turbo vacuum pump 124 that provides a modest vacuum in one embodiment of about 10−6 Torr, minimizing scattering of the D+ ions as they travel from the extraction iris 138 to the target 106. Titanium target 106 is positioned in a primary electrically insulating well 181 at the bottom of the chamber embedded into the pre-moderator material, which may be UHMW, HDPE or Teflon, of the pre-moderator 108. There is further a secondary electrical insulating well 182 surrounding the primary electrical insulating well. The surface of the moderator material in the primary and secondary electrical insulating wells may be seen as a corrugated insulator causing any surface charge to follow a curved path taken in any direction. The purpose is to provide a very long surface path to prevent electrons from traveling from the target to acceleration chamber 100 wall or any grounded element, and to avoid surface electrical breakdown or flashover in that surface path. As those skilled in the art know, the wells form an electrical insulating path. Additional corrugations or wells can be added to lengthen the path. Pre-moderator 108 has a high voltage bus bar 122 and fluid cooling channels 120 to and from the target. The high voltage is introduced via a high voltage receptacle 130 which is connected to the high voltage bus bar. Pre-moderator 108 acts as a HV insulator and as a mechanical support for the target 106 at a high negative bias. The pre-moderator 108 has metal cladding 140 at ground potential to minimize high voltage breakdown through the pre-moderator plastics. When in operation the D+ ions in the ion beam are attracted to the titanium target 106, where fast (2.5 MeV) neutrons are produced in a resulting DD fusion reaction. FIG. 13A illustrates an assembly of six modular generators 118, wherein pre-moderators 108 are spaced apart by spacers 128 which are also made of moderator material. FIG. 13B shows the arrangement of FIG. 13A in perspective. FIG. 13C shows the arrangement of FIG. 13B with one modular generator 118 removed from the assembly. FIG. 13D is a more diagrammatic illustration showing an arrangement in which modular generators may be mounted on translation and rotation mechanisms to be positioned to maximum irradiation of a cancer site. As is shown in FIGS. 13A-D the modular generators in embodiments of the invention may be arranged in an array to form a complete and moveable system of irradiating neutron sources with pre-moderators. For example, as shown in FIG. 13A-C, in the simplest configuration of the array, the modular generators may form a circle around a human torso or body part. The modular generators can be moved into three dimensional arrays around the subject to maximize neutron flux to a cancer site 148 that may not be centered on a body part 146, illustrated as a human brain in FIG. 13D. Thus, depending upon body contour, shape and size, and cancer location and distribution, the modular generators may be moved to adapt to the shape and tumor location in order to maximize the dose to the cancer and to minimize the dose to the other body parts. Referring to FIG. 13D, rotation 150 and translation 151 of the modular generator 118 can be achieved with electrical motors attached to the modular generator 118. Seven Functions of the Pre-Moderator Because the titanium target is on the pre-moderator (first stage of moderation), fast neutrons coming from the target immediately enter the pre-moderator and quickly moderated to thermal or epithermal energies. The pre-moderator also provides mechanical support, high voltage supply and cooling fluid transport to the titanium target. Exemplary pre-moderator materials that may accomplish this are Teflon and HDPE. Both Teflon and HDPE are excellent high voltage dielectrics which can also support a HV bus bar 122 and water channels 120 to be used to transport HV and the cooling fluids to the Ti target, as shown in FIG. 12C. As shown in FIGS. 12A, B, C a single generator 118 consists of an acceleration chamber 100, an ion source 102 emitting deuterium ions, a titanium target 106 and a pre-moderator 108. Pre-moderator 108 also provides a function of being a high voltage insulator for high voltage bus bar 122 that delivers high voltage (e.g. 80 kV to 300 kV)) to titanium target 106, and a water channels 120 that deliver cooling fluid to the titanium target 106. The high voltage is delivered from a high voltage power supply through a standard HV receptacle 130 to the bus bar 122 and then on to the titanium target 106, all of which are mounted in the pre-moderator 108. In various embodiments of the invention the pre-moderator 108 performs seven functions: (1) moderation, (2) mechanical support of the titanium target, (3) cooling fluid transport to the target, (4) high voltage transport to the target, (5) minimum surface flashover, (6) and a portion of a high vacuum container (a wall) with no out gassing (7). These seven attributes permit a substantial reduction of distance and amount of material between the fast neutron source and the patient, thus helping to maintain a maximum neutron flux delivered to the patient. Modular Generators Around a Subject FIGS. 13A-D show how the generators may be arranged. In FIG. 13A, six modular generators 118 form a ring around a secondary moderator 112 and are part of a structure formed by secondary moderator 112, spacers 128, and pre-moderators 108. Pre-moderators 108 and secondary moderator 112 provide the moderation function by slowing the neutrons down to epithermal energies (function #1). These elements also form a mechanical support (function #2) for the entire generator and moderator system. Secondary moderator 112 may also be a separate section attached directly to the modular generator just after the pre-moderator, each separate from the other instead of being in a ring 112 as in FIG. 13A. As shown in FIG. 12B-C, fluid transport (function #3) is supplied through channels 120, which delivers cooling fluid to target 106 to maintain the target at an acceptable operating temperature. Each generator is supplied with a separate cooling fluid input and output, wherein cooling fluid is provided through a connector 132 shown in FIGS. 12A-12C. Thus, the pre-moderator supplies fluid transport (function #4). High voltage is delivered via high voltage bus 122, which passes through pre-moderator 108 (function 4, high voltage transport). HDPE, UHMW and Teflon are excellent insulators and withstand high voltage flashover (function #6). All three may be used in vacuum systems without excessive out gassing and may help maintain the system vacuum (function #7). The achievement of these seven functions provides a very compact and flexible neutron source. The Secondary Moderator Secondary moderator 112 (FIGS. 13A-C) may comprise any one of or a combination of multiple moderator materials that optimize both the maximum flux and neutron energy for maximum dose to the cancer site. Selection (material, size and shape) may be varied depending on depth of the cancer in the subject and a desired dose at the cancer site. The secondary moderator may be D2O (heavy water) for delivery of thermal neutrons to, for example, throat and neck cancers, or a combination of AlF3 and Teflon for delivery of epithermal neutrons to brain tumors. The recommended levels of fast, thermal and gamma emission by IAEA are given in Table I. TABLE 1values in window.IAEA Recommended the beam exitBNCT beamIAEA Recommended port parametersvalueϕepithermal (n cm−2 s−1)~109ϕepithermal/ϕfast>20ϕepithermal/ϕthermal>100Dfast/ϕepithermal (Gy cm2)<2 × 10−13Dγ/ϕepithermal (Gy cm2)<2 × 10−13Fast energy group (ϕfast)E > 10 keVEpithermal energy group1 eV ≤ E ≤ 10Thermal energy froup (ϕthermal)E < 1 eV These IAEA recommended values depend upon older drugs, such as p-Boronophenylalanine (BPA) that have been approved for use in humans by the Food & Drug Administration (FDA) for other medical applications. Delivery of higher boron concentrations to a cancer site may depend to some extent on newer drugs to be developed, and may permit lower power, less efficient neutron beams to be used. Since treatment time might also be faster, the neutron beam quality need not be as high. DD fusion generators in embodiments of this invention have relatively low beam flux, thus permitting them to be used for cancer therapy. In some embodiments multiple modular generators may be distributed around a secondary moderator surrounding a central chamber holding a subject for treatment, providing an alternative to a completely integrated multi-ion beam system, and may have particular benefits in some circumstances. Benefits might include (1) an ability to quickly replace a single generator that has failed and needs repair; and (2) an ability to change alignment of the generators relative to one another, the moderator, and the subject. In regard to a subject, alignment of the generators may optimize dose distribution and density of neutrons at a cancer site, while at the same time minimizing spurious radiation, such as gamma rays that might be emitted external to the apparatus, or into healthy tissue of the subject. In the prior art, where reactor and accelerator neutron sources are used, careful attention has been given to achievement of high quality neutron beams to meet the IAEA standards for BNCT developed in 2001 for International Atomic Energy Agency (IAEA) (Current Status of Neutron Capture Therapy (2001) IAEA-TECDOC-1223. In embodiments of the present invention, where multiple modular DD fusion generators are used, these standards may be relaxed. The IAEA specification assumes that there is a single neutron beam that is used for all cancers and body locations. This results in standard values for the three neutron energies (thermals, epithermal and fast neutrons). Moderator and neutron spectral shifters are then designed to achieve these values for a particular fast neutron source as an input specification. This results in designs in the prior art that may not use the available fast neutrons economically and then may waste some of them to achieve the IAEA universal specs. For generators such as the DD fusion source in an embodiment of the present invention, early calculations have indicated that a single DD fusion generator would have difficulty achieving required fast neutron input to the moderating process. So, in embodiments of the invention, the use of multiple generators increases the total fast neutron yield available and allows the moderated dose to be distributed over a larger area of the body, instead of having the beam enter at one location of the body. For example, as shown in FIG. 13D, neutrons n are entering the head from many directions. This permits reduction of thermal neutron flux at any one point on the skin of the head while still achieving adequate epithermal flux to the cancer site. In early prior art reactor BNCT experiments, the thermal neutron flux burned the skin of subjects. When considering neutrons used for a particular cancer it is desirable to direct the maximum flux to the cancer site, and therefore, one must consider the specific cancer that is to be treated. This includes location and depth in the human body. Because of their relatively small size and large neutron yield, the modular generators in the embodiments of the present invention are particularly able to accomplish this by being positioned to maximize their flux at the cancer site. Since in embodiments of the invention generators are placed as close to the patient's body as practical to maximize flux at the cancer site, there is a more holistic problem. There are multiple parameters for each modular generator: (e.g. neutron flux, neutron energy, position relative to the body). What comes out of a single neutron beam pipe (1998 IAEA Standards, Table I) is not the only concern. A body part can now, in new implementations of the invention, be irradiated in all directions, and neutron intensity can be adjusted at each modular generator to achieve better flux and even more optimum neutron energy than with a single beam LINAC or a reactor. The direction of each neutron beam can be adjusted by rotating and displacing each modular generator 118. Each modular generator's yield can be adjusted electronically by varying the accelerator voltage and the ion beam current. Since the moderator size is relatively small and compact compared to the prior art, the neutron spectrum of each modular generator 118 can be adjusted by the selection of different moderator materials and thicknesses. Lowering of Required Beam Quality In embodiments of the present invention the subject's body is bombarded with neutrons from multiple directions. The neutrons can come from all sides of the body part, which minimizes the amount of distance each beam has to transverse. Unwanted neutrons striking the skin are now distributed over a larger area, reducing the skin dose of harmful components (e.g. gammas, and thermal and fast neutrons) per unit area. These components are simply delivered over a larger area of the skin. This permits adjustment of dose at the cancer site to be higher than that achieved with a single beam but with reduction of harmful components over a larger area of the skin. For a single beam case in the prior art, an argument might be made that one can rotate the patient for each exposure, but, due to possible patient movement, the neutrons would not be as accurately placed as in multi-beam embodiments of the present invention. For each placement the patient would have to be carefully re-oriented relative to the single neutron beam, which requires careful placement of the patient. In embodiments of the invention, multiple beam directions and an ability to adjust the neutron flux of each modular generator allow for optimum delivery to the cancer site while reducing harmful components. For example, if the cancer is located in the left lobe of the brain, the neutron flux to the tumor can be adjusted to deliver epithermal neutrons in the direction of that tumor. Since each modular generator neutron flux can be adjusted quickly by varying the accelerator's high voltage or the ion beam current, and by translation and rotation, this can be done easily with delivery determined by a computer program. In the present invention, a control computer monitors the ion beam current, the acceleration voltage and the output neutron yield, which can be automatically adjusted. Small modular generators in embodiments of the invention can make use of new boron drug delivery methods for higher concentrations of boron to the cancer sites. Higher concentrations of boron lower the required neutron dose and require shorter delivery time. Higher boron concentrations to the cancer site permit use of neutron generators with lower neutron yield such as the modular DD fusion generators in embodiments of the present invention. Each modular generator 118 is an independent device capable of producing neutrons independently of the other generators. This allows the total available power, P, to be distributed over N generators, resulting in the heat load being distributed safely without, for example damaging the titanium targets (unlike single target devices using lithium). In one example there are six modular generators, distributing total heat load per titanium target, since the number of neutrons per unit area is fixed by the ion beam power per unit target area. To properly treat a tumor in a subject, a large number of neutrons is required. For reasons of temperature management and stability, DD fusion generators are at present limited to fast neutron yields of less than 4×1010 n/sec. To increase the neutron yield, the number of neutron generators can be increased in embodiments of the present invention. Pre-moderators 108 can be shaped so that larger numbers of modular generators may be fitted around a subject to be treated. In the example shown by FIG. 13A there are six generators arranged equally spaced around a common secondary moderator 112, the subject cavity 116 and the subject 134. Spacing blocks 128, composed of moderator material that may be the same as that of pre-moderator 108 (e.g. Teflon or polyethylene), are placed between each pre-moderator to provide adequate spacing for fitting the subject cavity 118. The wedge angle, α, as indicated in FIG. 12A, on the pre-moderator in FIG. 13A determines the number of modules 118 with pre-moderators 108 that can fit in the circle around the patient and how close the sources may be to the patient. For example, a wedge angle of α=30° for 6 generators and α=22.5° for 8 generators. Moveable Sources with Fluid Moderator One embodiment of a system of modular generators is shown in FIGS. 13A and 13B. In FIG. 13A a plane view of six modular neutron generators 118 fitting into the cylinder (or ring) is shown. In FIG. 13B, a perspective view is shown. The modular generators can also be arranged in other patterns to maximize the dose in particular locations in the subject's body and deliver cancer therapy to selected body organs. In some embodiments of the invention the modular generators may be moved by electric motors and mechanical means to optimized locations to provide the maximum dose to the cancer site and tumor profile as determined by boron bio-distribution test biopsy and pathological analysis, Positron Emission Computed Tomography (PET-CT), Computed Tomography (CT) or magnetic resonance imaging (MRI). One may make use of moderating materials between movable modular generators. For clinical systems there should be moderator material between the modular generators. Ideally the material can quickly position itself to the new location of the modular generators and also be a moderating material. As shown in FIG. 13D, liquid moderator 156 can be used to surround the modular generators 118, acting as a secondary moderator. The moderating material is shown between the movable modular generators. The liquid is contained in an appropriate liquid container. Liquids that also have good moderating properties can be used and are easily displaced by the modular generators when moving. For example, different grades of 3M™ Fluorinert™ Electronic Liquid (e.g. FC-40), which is non-conductive, thermally and chemically stable fluid, can be inserted between generators. Like Teflon it contains primarily fluorine atoms, making it an excellent moderator, and no hydrogen. Stages of Moderation Use of multiple modular generators in embodiments of the invention permits efficient use of modulator material, reducing size of moderator and shielding material and, thus, the reduction and size of the entire system. It also reduces the required flux density of fast neutrons by bringing the neutron sources closer to the patient and directing the limited number of neutrons to the cancer site in a more efficient fashion. The subject's body also becomes part of the equation of the moderating process. The fact that the neutrons are coming from multiple directions reduces local skin dose and localized body dose of healthy tissue. Rather than coming into the body at one location, the neutrons are coming from roughly 360 degrees around the body. Moderation of fast neutrons in embodiments of the invention is a three-step process. In a first step (1) the pre-moderator 108 acts to reduce energy of the fast neutrons in as short a distance as practical with a minimal amount of gamma radiation produced in the process. The pre-moderator also serves as a medium to (2) transport high voltage and (3) cooling fluid to a fast neutron production titanium target 106. Combining these three functions ((1) moderation, (2) fluid transport and (3) high voltage transport) reduces distance and the amount of material between the fast neutron source and the patient, helping to maintain a maximum neutron flux finally delivered to the patient. Partially slowed neutrons can then pass into the secondary moderator 112 which continues the slowing process without undue production of gamma rays from, for example, hydrogen. In the case of small animal models, the selected moderator may be heavy water (D2O). Neutron energy reduction is continued by the D2O without the generation of ˜2.2 MeV gammas that would occur if materials composed of hydrogen were used. For the case of irradiating tumors of depth greater than 3 cm in a human body, the neutrons need to be moderated to epithermal neutron energies. The human body also acts as a partial, final moderator. Thus, the epithermal energy neutrons are slowed further as they move through the body, and finally are slowed to thermal energies at the tumor site. Those skilled in the art will understand that the moderation is a statistical and random process that reduces the neutron energy with a variation or spread of the neutron energies. The process can also result in undesired gamma ray components (e.g. 2.2 MeV gammas from hydrogen capture of neutrons) which damage health cells. In embodiments of the invention, selection of the moderator material depends at least in part upon the desired energy of the neutrons at the body's skin to achieve maximum penetration to the cancer site while reducing (1) excess thermal energy components at the skin, (2) the cost and availability of the moderator material, and (3) harmful gamma ray components. Each generator's energy, yield, direction and moderation can be determined from moderation materials, the generator's voltage and acceleration current. Unlike in the prior art, dimensions of the moderator and content may be quickly changed. In some embodiments of the invention a liquid moderator (e.g. Fluorinert FC40) or a granular (e.g. AlF3) moderator may be used. The modular generators are positioned in the liquid or granular moderator material, where they are free to move by mechanical means quickly between different cancer sites. In the prior art, the moderators and shields are large, massive and usually fixed relative to a single beam reactor or linear accelerator. The patient is usually moved relative to the fixed neutron source. Using liquid or granular moderator materials permits a more efficient reduction of fast neutrons to epithermal energies while minimizing thermals and fast neutrons. Selection of the pre-moderator material is important for optimum neutron beam quality. Generally speaking, beam quality involves minimization of harmful components of radiation that accompany the production of thermal neutrons at the cancer site but also the minimization of the fast and thermal neutrons at the skin surface. In this process gamma rays are produced and, depending upon the cancer site, fast neutrons must be converted to the right energy so that they penetrate the body and deliver thermal neutrons to the tumor site with minimal irradiation of healthy tissue. Moderating the neutrons to thermal energy can result in the skin being damaged. Indeed, the thermal neutron dose to the skin can be larger than the dose to the tumor. The body itself moderates and absorbs the neutrons as they penetrate the body. Selection of the moderator material requires materials that do not moderate the fast neutrons too quickly to thermal energies. Thermal neutrons can damage the skin, and if hydrogen atoms are present in the moderation process, then damaging gamma rays are also produced. Like the moderator, the human body also moderates and absorbs the neutrons. The desired required depth of penetration depends upon the location of the tumor in the body. Simulations show that penetration of thermal neutrons starting at the skin results in penetration depths of 3 to 5 cm before a large fraction of the neutrons are absorbed. Teflon Moderator for Clinical Machine When used as a Pre-moderator, Teflon (PTFE) can satisfy 6 of the 7 functions listed above. Indeed, on several of the attributes Teflon excels. For example, since Teflon does not have atomic hydrogen, gamma production is avoided, whereas the use of HDPE does have hydrogen and, therefore maximizes the thermal neutron moderation with and added 2.2 MeV gamma ray component. Selection of HDPE as the pre-moderator material results in production of thermal neutrons in a short distance from the Ti target, whereas the use of Teflon results in a slower rate of neutron energy reduction from 2.5 MeV permitting the production of epithermal neutrons for deeper penetration into the human body and no 2.2 MeV gammas. Teflon can have a minimum high voltage in which surface arcs (flashovers or surface discharges) momentarily short out the high voltage, and lead to damage to the Teflon surface and possibly damage to the high voltage power supply. This is primarily a materials problem and not a structural problem (shape of the accelerator and Teflon shape and structure). Surface discharge along solid insulators in a vacuum in high voltage devices determines the maximum voltage between an anode and a cathode. The voltage hold-off capability of a solid insulator in vacuum is usually less than that of a vacuum gap of similar dimensions. O. Yamamoto et. al (Yamamoto, O; Takuma, T; Fukuda, M; Nagata, S; Sonoda, T “Improving withstand voltage by roughening the surface of an insulating spacer used in vacuum,” IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION (2003), 10(4): 550-556) has studied a simple and reliable method to improve surface insulation strength of a dielectric such as Teflon, PMMA, and SiO2 by roughening the surface of the dielectric. Some experimental results have revealed that in a vacuum, charging along the surface of an insulating spacer precedes the flashover. The charging takes place through a process in which electrons are released from a triple junction where the cathode, insulator and vacuum meet, and propagate toward the anode, causing a secondary emission electron avalanche (SEEA) along the insulator surface. The dielectric (e.g. Teflon or HDPE) can hold charge like a battery or capacitor and then release it along the surface. This limits the use of plastics such as Teflon and HDPE as insulators and moderators inside the vacuum chamber of the neutron generator's acceleration chamber 100. For short distances across Teflon (10 mm), Yamamoto found that roughing the surface (e.g. with sandpaper or sandblasting) affects the charging of various plastics (such as Teflon and HDPE), which decreases as roughness increases. Yamamoto used roughness up to 37.8 μm but had used lower voltage gradients and smaller dielectric thicknesses (10 mm). Studies in embodiments of the present invention find that larger surfaces (distances e.g. 8 inches) of Teflon can be roughened with roughness values of 5 microns and greater and achieve high voltages of 150-220 kV for distances greater than ˜2 cm without flashover. More importantly, the roughing method gives higher insulation strengths without time-consuming conditioning previously used. This provides a significant advantage and makes generators in embodiments of the present invention operational more quickly. Depending on maximum field strength required, conditioning by the roughing process could take minutes or days. Below 1 MV m−1, the conditioning process is relatively fast. Between 1 and 10 MV m−1, the conditioning process takes longer. The best way to monitor how conditioning is going is to record the number of transient discharges (or sparks) per hour. At very high fields the arc rate might never get better than a few arcs per hour. A tolerable arc rate depends on the application. If no high voltage breakdown (arcs) can be tolerated, then the system must first be conditioned to a higher field, and then when the voltage is reduced to the operating level the arc rate drops almost to zero. For very high field strengths above 10 MV m−1, it is very difficult to condition the electrodes to give an arc rate of zero. The electrode shape and material composition becomes very important at these field levels. The Importance of the Human Body in the Moderation Process The human body acts as a moderator to reduce the epithermal neutrons to thermal energies at the cancer site. The amount of neutron energy reduction by the human body depends at least in part upon the depth of the tumor in the body. This determines the maximum neutron flux for delivery to the patient. The desired reduction of the neutron's energy will depend upon the depth of the tumor in the human body. For example, with throat and neck cancers the reduction of the neutron energy to thermal energies is desired for maximum dose to the cancer site. For small animal models, thermal energies are also desired. Dimension in the body from the skin (epidermis) to the cancer site can vary, requiring the neutron energy to be large enough for penetration to the cancer while still primarily at thermal energies, permitting capture by the boron and the destruction of cancer cells. For small animal models or skin cancer in humans, the neutrons can be at thermal energies. For cancers at deeper depths in the body, epithermal neutrons (0.025 to 0.4 eV) can be used. For deep tumors in the torso, such as, for example, pancreatic tumors, epithermal neutrons are required. Pancreatic tumors are deep in the torso and require epithermal neutrons at entrance to the body to penetrate to the tumor. Moderation of the epithermal neutrons occurs as they pass though the body. Simulations in various embodiments show that there are materials at the right thicknesses, such as Teflon, 7LiF and AlF3, which produce the epithermal neutrons that penetrate the body and thermalize by the time they reach the depth of the tumor with a maximum neutron flux. In embodiments of the invention, this occurs while minimizing production of thermal neutrons at the skin. Shape of a Clinical Machine to Match a Human Body The shape of the patient's chamber in a machine may be contoured to fit the human body part to maximize radiation to the cancer site. The shape depends upon the body part to be irradiated and the location of the tumor. As shown in FIG. 13D, for glioblastoma 148 (brain cancer), modular generators 118 may be arranged in a close ring around the head 146 that maximizes neutron flux to the cancer site 148 in the brain. The intensity of each generator can be varied to achieve maximum thermal neutrons to the tumor while minimizing the dose to healthy tissue. As discussed above, applications in embodiments of this invention permit control of the distance of each generator from the cancer site. The cancer site may be mapped using radiographic means (CT scans) and/or MRIs. A treatment planning protocol can then be determined for the optimum use of the clinical neutron source. The intensity of the neutrons coming from each neutron generator can then be varied and the location of each individual generator can be optimized. As shown in FIG. 13 D, an improvement of the moderator surrounding the modular generators is to suspend or surround the modular generators with a liquid 156 that does not contain hydrogen (a gamma producing source), but has modest atomic-number atoms like Fluorine, Carbon or Nitrogen. Various kinds of Fluorinert (tradename), FC-70 or FC-40, or FC3839 can be used. The fluid may be put between the modular generators and by mechanical means each modular generator can move independently of the other generators to a certain extent. This fluid can also absorb some heat from modular generators. As shown in FIG. 13 D, an improvement of the moderator surrounding the modular generators is to suspend or surround the modular generators with a liquid 156 that does not contain hydrogen (a gamma producing source), but has modest atomic-number atoms like Fluorine, Carbon or Nitrogen. Various kinds of Fluorinert (tradename), FC-70 or FC-40, or FC3839 can be used. The fluid may be put between the modular generators and by mechanical means each modular generator can move independently of the other generators to a certain extent. This fluid can also absorb some heat from modular generators. Generator Alignment In embodiments of the present invention each stand-alone generator, as seen in FIG. 13D, for example, may be positioned and aligned to give a maximum flux and neutron distribution at the cancer site. Each generator is small enough in size and weight that the generators may be mechanically moved and positioned so that optimum neutron flux at the cancer site is achieved, depending upon the cancer's location and distribution. The generators may be arranged around a moderator whose radial thickness is optimized to deliver a maximum thermal neutron flux to the cancer site. Depending upon the body part being irradiated, the geometry can be circular or elliptical. By selecting the moderating material and radial thickness one can deliver thermal neutrons to the cancer site. FIG. 14A shows an on-axis view of an exemplary clinical neutron source using multiple modular generators 118 for BNCT of a human head. This example uses eight modular generators 118 and assorted moderator materials coupled with reflecting and shielding material (e.g. graphite 144). Secondary moderators (166 and 170) can be composed of one or more materials. There are moderator spacing blocks 128 in one embodiment composed of the same material High Density Polyethylene (HDPE), Ultra High Molecular Weight polyethylene (UHMW), or (PTFE (Teflon)) as the secondary moderators. Blocks of these materials fit in between the modular generators and are adjacent to each generator's pre-moderator. They act as mechanical spacers as well as moderator components. The outside of this region, between and behind the modular generators 118, is filled with either graphite or lead 144 to serve as a neutron reflector and shield. FIG. 14B also shows a side section view of the apparatus of FIG. 14A taken along a line through the top and bottom generators. There is additional moderator material in the front and behind the modular generators, extending a little above the pre-moderator. In our example, the cylindrical space 164 available for the patient's head is 52 cm deep and 30 cm in diameter. This space might be lined with 1-mm of cadmium 162 to shield against too large a thermal neutron dose to the patient's skin. Shield 162 is also shown in FIG. 14A. In other embodiments this space may be lined with 6LiF. The exemplary arrangement as illustrated in FIGS. 14A and B has a secondary moderator consisting of multiple layers of 40% Al and 60% AlF3 (166) and an additional moderating cylinder 170 of either 7LiF or D2O. These materials are shown to be concentric rings in FIG. 14A. Since 7LiF or D2O can be expensive, thicknesses were varied to obtain a desired neutron beam quality without over-using either 7LIF or D2O. In the example shown in FIGS. 14A and 14 B the thickness ratio between the two segments is altered, the total moderator thickness is 34 cm, and the sources are R=52.5 cm from the origin (center of the brain). The effect of doing this varying these materials is plotted graphically in FIG. 15. The reflector material graphite 144 is 30 cm thick in this example, the thickness of the Teflon 168, t, in front of the 2.5 MeV source is varied, and the portion 170 of the moderator is either 7LiF or D2O. As t changes, the thickness of the Al/AlF3 166 of the moderator changes, with all other dimensions remaining constant. The target is embedded in the Teflon 168, UHMW or HDPE. Sources are titanium targets 106 being bombarded by deuterium ion beams 5.0 cm in diameter. Each target is emitting 4×1010 neutron/sec. Eight modulator generators 118 emit 3.2×1011 n/s total emission. A concentration of 10B in the tumor and health tissue (e. g. skin) is known to be possible. 10B tumor concentration is assumed to be 50 ppm, while 10B in healthy tissue is 15 ppm. The relative biological effectiveness (RBE) for 10B in tumor is 2.7, and in healthy tissue is 1.3. Tumor and healthy tissue doses are calculated using the NRC and ICRP models for neutron RBE. The material 7LiF was the best performer and D2O was second best. An important main objective in these examples is to give a sufficient dose of neutrons to the cancer while minimizing the dose to the healthy tissue and not damaging it. FIG. 15 shows the performance for moderators with different values for tin cm and either 7LiF or D2O in the secondary moderator. The ordinate R is the ratio of tumor dose at the origin to healthy tissue skin dose, and the tumor dose at the center of the brain assumed to be the site of the cancer. As can be seen from FIG. 15, 7LiF outperforms D2O. The best performance is R=1.9 and a tumor dose in excess of 1.4 Sv/hr. A consequence of RBE is that a small percentage of fast neutrons is essential to obtain a high value for R; also, a reasonable number of epithermals is required to penetrate the target. Thus a combination of 7LiF and D2O may outperform either material alone. A Need for Small Animal Neutron Sources Development of boron delivery agents for BNCT is an ongoing and challenging task of high priority. A number of boron-10 containing delivery agents have been prepared for potential use in BNCT. With the development of new chemical synthetic techniques and increased knowledge of the biochemical requirements needed for an effective agent and their modes of delivery, a wide variety of new boron agents has emerged, but only two of these, oronophenylalanine (BPA) and sodium borocaptate (BSH) have been used clinically and have US FDA approval. Patient-derived xenograft (PDX) is created by transferring primary tumors from a patient into a mouse or small animal model. Tests of delivery and effectiveness of drugs to the cancer site can then be performed. In the prior art, only beamlines from nuclear reactors and linear accelerator structures can be used. A small laboratory neutron source, as in embodiments of this invention, is therefore valuable in the development and testing of new boron delivery drugs and their effectiveness in destroying the cancer site. As compared to a clinical delivery system, a smaller number of stand-alone generators such as generators 118 is needed for a delivery system for a small animal such as a mouse. The modular generators used have a slab wall angle of α=0 (see α defined in FIG. 12 A). The secondary moderator may be a separate container of heavy water (D2O). Since the small animal target is indeed small, the secondary moderator volume can be reduced, and the compact modular generators can be moved close to it permitting the modular generators to be closer to the animal target. Thus, the neutron flux at the cancer site is increased, and with proper selection of moderator material and size, will still be able to moderate the neutrons to IAEA standards. In addition, by moving closer, the number of generators can be reduced while still maintaining a high thermal neutron flux at the cancer site. In our example of the new art for a small animal source, we can use four modular generators 118 to emit enough thermal neutrons at the cancer site. We can use the modular generators of 12 A, B, C with the slab wall angle of α=0. This makes the pre-moderator 108 a rectangular cuboid (or “rectangular slab” of). FIG. 16A is a perspective view of a modular generator having such a rectangular pre-moderator 108, making it suitable for arrangements of four generators in a rectangular array, as shown in FIG. 16B. In FIG. 16B the four modular generators are arranged around a secondary moderator 112, which in one embodiment may be a container of heavy water or granulated moderator material. FIG. 16C is a cross section view of the arrangement of FIG. 16B, taken along section line4 16C-16C of FIG. 16B. The elements previously annotated for modular generators are reused in FIGS. 16 A, B and C. FIG. 16D is an exploded view where the four generators 118 are moved back from the small heavy water moderator 112. Each generator 118 has a pre-moderator 108 with a fast neutron generator with a titanium target 106. A deuterium ion beam is generated by a plasma ion source 102 and accelerated in an acceleration chamber 100 to the titanium target 106, where the DD fusion reaction occurs releasing fast 2.5 MeV neutrons. This description is all common to the descriptions or other embodiments in the specification. The neutrons generated pass through a pre-moderator 108, where they are partially moderated to thermal neutron energies. They then pass into the moderator block 112 where they are further moderated, reducing the energy of fast neutrons to thermal neutron energies. The thermal neutrons then enter a cylindrical mouse chamber 114 where they enter the small animal 116. The pre-moderator is designed to slow the fast neutrons to thermal neutrons by scattering the fast neutrons via collisions with the hydrogen in the HDPE or UHMW plastics. The distance the 2.5 MeV neutrons have to traverse is approximately 3 to 5 cm, wherein approximately 50% of the neutrons lose enough of their energy to be classified as thermal neutrons. These neutrons, containing both thermal and fast neutron components, can then travel into the moderator box 112, where they are further moderated by collisions with deuterium atoms. Roughly speaking, the HDPE with its hydrogen-atoms moderates the neutrons to thermal energies over a short distance; the thermalized neutrons then penetrate the cylindrical chamber 114 wherein they place the small animal 116. The small animal model is used to test the delivery of boron to the cancer site. For the pre-moderator, high density polyethylene (HDPE) is optimum for producing the maximum flux of thermal neutrons. As in the case of the clinical generator, it is desired to produce a maximum thermal flux at the cancer site. A mouse is a small object, and penetration of thermal neutrons to the cancer site can easily be achieved. Moderation of the fast neutrons to thermal energies is desired with minimum production of gamma radiation, which is harmful to the healthy cells. As those skilled in the art will understand, hydrogen atoms are excellent at scattering fast neutrons, resulting in moderation of the neutrons to thermal energies in the shortest path length in the moderating material. Indeed, using 5-6 cm of high-density polyethylene (HDPE) or UHMW plastic results in moderation of about 50% of 2.5 MeV neutrons to thermal energies. Further moderation of the neutrons by longer distances in the HDPE results in more fast neutrons being converted to thermal energies. However, this results in reduction of the total flux (n/cm2) that is available since the neutrons are being emitted in a 4π solid angle. Hydrogen capture of neutrons produces high energy gamma radiation, which is destructive to both healthy and cancerous cells. Adding another moderator to further thermalize the neutrons is accomplished by the use of heavy water (D2O). The skilled person will understand that the embodiments described in this application are exemplary, and not limiting. Many variations may well fall within the scope of the invention, which is limited only by the scope of the following claims.
	abstract	A particle removal tool includes a workpiece holder and an optical tweezer. The workpiece holder is configured to support a workpiece. The optical tweezer is configured to emit a plurality of focused light beams to the workpiece, wherein the plurality of focused light beams are respectively converged to focal points between the optical tweezer and the workpiece, and are configured to take particles away from the workpiece.
	claims	1. Apparatus comprising:an x-ray source which defines a static focal spot;a collimator which controls the dispersion of radiation from the x-ray source;a detector which obtains images while the x-ray source is in motion; anda motion controller which synchronizes movement of the static focal spot, x-ray source and collimator such that the static focal spot and collimators are moved in a direction opposite to directional movement of the x-ray source during an exposure period. 2. The apparatus of claim 1 wherein the static focal spot is moved at a linear speed equal to that of the x-ray source during the exposure period. 3. The apparatus of claim 1 wherein synchronized movement of the static focal spot, x-ray tube and collimator maintains an effective focal spot fixed in space relative to a target during an exposure and maintains an x-ray field on a detector. 4. The apparatus of claim 1 wherein the focal spot and the collimator follow a linear oscillating pattern over multiple x-ray exposures during a tomosynthesis scan. 5. The apparatus of claim 1 wherein the collimator blades and x-ray source have closed loop controllers. 6. The apparatus of claim 1 further including a main processor which regulates motion of the focal spot, collimator and x-ray source. 7. The apparatus of claim 1 further including a focal spot and collimator position controller coupled to a cathode to deflect electron trajectory in a width direction. 8. The apparatus of claim 1 wherein focal spot displacement is proportional to a bias voltage level applied by a voltage controller. 9. The apparatus of claim 8 wherein the bias voltage is dynamically or statically configured prior to x-ray exposure. 10. A method comprising the steps of: performing a tomosynthesis scan including synchronizing movement of a static focal spot, x-ray source and collimator using a motion controller, including moving the static focal spot and collimator in a direction opposite to directional movement of an x-ray source during an exposure period. 11. The method of claim 10 including moving the x-ray source counter clock-wise to a start position, and moving the focal spot and collomator in a direction opposite that of the tube to a start position. 12. The method of claim 11 including moving the x-ray source clock-wise and moving the static focal spot in a direction opposite to and generally synchronized with directional movement of the x-ray source, and moving the collimator in synchronization with the static focal spot. 13. The method of claim 12 including causing the synchronized movements to be continuous over the duration of the exposure. 14. The method of claim 13 including activating the x-ray source upon reaching an initial imaging position. 15. The method of claim 14 including moving the focal spot to a starting position which is pre-calculated based on the x-ray technique and gantry scan speed of an intended tomosynthesis scan. 16. The method of claim 15 including, when the exposure is complete and the focal spot reaches a pre-calculated stop position, deactivating the x-ray source and moving the static focal spot and collimator blades back to the start position. 17. The method of claim 16 including, after obtaining a tomosynthesis projection image, determining whether an end point of the clock-wise scan has been reached and, if the end point has not been reached, obtaining at least one more tomosynthesis projection image. 18. The method of claim 17 including moving the x-ray source to a zero position and moving the focal spot and collimator to a center position to prepare for a conventional mammographic exposure.
	claims	1. An apparatus, comprising:a. a charged particle source configured to emit charged particles;b. at least one particle optical element configured to form a charged particle beam of charged particles emitted by the charged particle source;c. an objective lens configured to generate a charged particle probe from the charged particle beam, the objective lens defining a particle optical axis;d. a first electrostatic deflection element arranged—in a direction of propagation of charged particles emitted by the charged particle source—downstream of the objective lens, the first electrostatic deflection element configured to deflect the charged particle beam in a direction perpendicular to the charged particle optical axis; ande. an electrically conductive shielding element with an opening configured so that the charged particle beam can pass through the opening, the electrically conductive shielding element being arranged—in the direction of propagation of charged particles emitted by the charged particle source—downstream of the first electrostatic deflection element. 2. The apparatus of claim 1, wherein the first electrostatic deflection element comprises electrodes having a capacity with respect to each other and with respect further components of the apparatus adjacent to the electrodes of less than 50 pF. 3. The apparatus of claim 2, wherein the objective lens has a source side directed to the charged particle source and a probe side opposite to the source side, and wherein the objective lens comprises an electrostatic immersion lens configured to reduce a kinetic energy of charged particles when passing through the objective lens from the source side to the probe side to a kinetic end energy of less than or equal to 5 keV. 4. The apparatus of claim 3, wherein the objective lens further comprises a magnetic lens. 5. The apparatus of claim 1, further comprising a gas feeding system with one or more tubes, each of the one or more tubes having a terminating end, wherein the terminating end of each of the one or more tubes is positioned between the objective lens and the electrically conductive shielding element. 6. The apparatus of claim 5, wherein the gas feeding system is designed to feed a reaction gas that is capable of causing a chemical reaction with a sample in the apparatus after excitation by the charged particle beam. 7. The apparatus of claim 6, further comprising a control system configured to control the gas feeding system and the first electrostatic deflection element so that, after a reaction gas is supplied to the sample, the sample can be scanned at specified positions by the charged particle beam. 8. The apparatus of claim 1, wherein the apparatus is configured so that the sample is scanned by the charged particle beam so that a position at which the charged particle beam impinges on the sample is kept constant for a selectable dwell time and thereafter is scanned to another position on the sample within a time period of less than 100 ns. 9. The apparatus according to claim 1, wherein a distance d1between the first electrostatic deflection element and the electrically conductive shielding element is in the range of 10 μm<d1<2.5 mm. 10. The apparatus according to claim 1, wherein the opening of the electrically conductive shielding element has a linear opening dimension of less than 100 μm. 11. The apparatus according to claim 1, wherein a distance d2 between the electrically conductive shielding element and a probe plane in which the probe is generated by the objective lens is less than 50 μm. 12. The apparatus according to claim 1, wherein the first electrostatic deflection element has an inner opening of a size not to obstruct the charged particle beam in a field of view with a diameter of d3<100 μm. 13. The apparatus according to claim 1, wherein the first electrostatic deflection element has an inner opening with a diameter d4 in a range of 0.05 mm<d4<5 mm. 14. The apparatus according to claim 1, wherein the first electrostatic deflection element comprises a plurality of electrodes separated by slits having a width w of 50 μm<w<3 mm. 15. The apparatus according to claim 1, further comprising a second electrostatic deflection element arranged on a source side of the objective lens. 16. The apparatus according to claim 15, further comprising a deflection control configured to control deflection voltages applied to the first and the second electrostatic deflection elements so that the beam of charged particles is angularly deflected while a position of the charged particle probe in a probe plane, in which the probe is generated by the objective lens, is maintained fixed. 17. The apparatus according to claim 1, further comprising a blocking element arranged between the first deflection element and a surface of a sample, the blocking element being configured to at least partly block the beam of charged particles when the beam of charged particles is deflected. 18. The apparatus according to claim 1, wherein the first electrostatic deflection is selected from the group consisting of a dipole, a quadrupole, a hexapole, an octopole and a decapole. 19. A method comprising:a. directing a primary beam of charged particles onto a surface of a sample, the primary beam of charged particles passing through, in relative order, an objective lens, an electrostatic deflection element and an electrically conductive shielding element before reaching the surface of the sample; andb. deflecting the primary beam of charged particles with the electrostatic deflection element onto a plurality of positions on the surface of the sample with a minimum dwell time of 100 nanoseconds or less at each of the positions on the surface of the sample. 20. The apparatus of claim 1, wherein the first electrostatic deflection element has a deflection bandwidth of at least 10 MHz.
052705498	description	DESCRIPTION OF THE PREFERRED EMBODIMENTS There is shown in FIG. 1 an annular cylindrical multihole collimator 10 for a radioisotope camera. Collimator 10 is made up of a plurality of closed annular radio-opaque plates 12 and 12a each having a plurality of corrugations extending from the inner 16 to the outer 18 radius of the plate and defining one or more (actually three in FIG. 1) segment sections 20, 22 and 24, which combine to form three segments 26, 28 and 30 separated by junctions 32, 34 and 36. The junctions are uncorrugated areas between segment sections. If the collimator is to have but one segment then each plate will have but one corrugated segment section and the remainder of the plate will be all junction. The stacking of plates 12 and 12a along longitudinal axis 40, with their peaks 42 and valleys 44 aligned from plate to plate, create a multiplicity of holes 46. Each plate 12 or 12a, FIG. 2, may have the corrugations 14 converging as shown at 14a, diverging as shown at 14b, or parallel as shown at 14c. Segment sections 20', 22' and 24' may be crescent-shaped as shown in FIG. 2, or may have uniform inner and outer radii as shown in FIG. 1. Aligning means or indicia may be provided for assembly of plates 12 and 12a. For example, junctions 32', 34' and 36' may include alignment holes 50, 52, 54, respectively, for receiving alignment pins, or may include notches 56, 58, 60, or some other indicia to meet with a jig or guiding surface. If there is symmetry about a diametral axis through the center of one segment section, then plate 12 can be reversed and used in place of 12a. The assembly technique is shown in more detail in FIG. 3, where plates 12a, b, . . . , are stacked on a base ring 70 which contains alignment pins 72, 74 which are received in alignment holes 76, 78 in two of the four junctions 80, 82, 84, 86, which define the four segment sections 88, 90, 92, 94 that constitute the four segments 96, 98, 100 and 102. Between the junctions 84 of each plate 12" are fillers 104, 106, 108 and 110, which are radiologically opaque as are the junctions. Fillers 104 and 106 include holes 112 and 114 respectively, which receive guide pins 72 and 78 receivable in junctions 80 and 82. Cap ring 120 is fastened to alignment pins 72 and 74 by means of screws and washers 122 and 124, thereby unifying the entire assembly. Optionally, as shown in FIG. 4, assembly can be guided by means of pins which are parallel and provisionally reside in the corrugation holes 46 themselves, FIG. 4. Such pins 130, 134, 136 are shown radially disposed in each layer of holes 46. Preferably at least one additional set of guide pins 130a, 134a, 136a, is provided in order to provide two-dimensional alignment through the quadrature relationship of the pins. Plates 12 and 12a are bonded together by a suitable adhesive 140, FIG. 5, where their peaks and valleys contact. Pins 130, 134, 136, 130a, 134a, 136a are removed after bonding is complete. The corrugations may be triangular as shown in FIG. 5 to form square collimator holes 46, or the corrugations may be three-sided to form hexagonal holes as shown in FIG. 6. Alternatively, triangular corrugations may be used, as shown in FIG. 7, in staggered fashion with joiner plates 150 between them which are bonded to their peaks and valleys. Each plate 12 may be formed from a blank using a press and die set 160, FIG. 8, which cuts an annular blank 162 with two or more guide holes 164 and 166. Blank 162 is then placed in a corrugation die set 170 aligned by pins 190, 192 inserted in holes 160, 164, FIG. 9, to produce a finished corrugated piece 172. The method thus involves the first step 180, FIG. 10, of cutting the blank, followed by the corrugation step 182, after which the finished plates are assembled 184 as shown in FIG. 3 and bonded together, step 186, before they are finally capped 188, again as shown in FIG. 3. In accordance with the structure of FIG. 7, every other plate would be left uncorrugated: that is, step 182, depicted in FIG. 9, would be omitted and the flat blank plate 162 resulting from the operation in FIG. 8 would be used between the corrugated plates. Although specific features of the invention are shown in some drawings and not others, this is for convenience only as each feature may be combined with any or all of the other features in accordance with the invention. Other embodiments will occur to those skilled in the art and are within the following claims:
	abstract	A fuel assembly design for nuclear reactors that is used in fast neutron reactor cores to provide more reliable spacing of a fuel element bundle in a fuel assembly and reduced local stress in the cladding of the fuel elements in the region where the elements are in contact with spacing elements. The fuel assembly has a top nozzle and a bottom nozzle which are connected to one another by a jacket. A bundle of rod-type fuel is elements arranged in the fuel assembly with the aid of a grid and spiral spacer elements wrapped around the cladding of each fuel element. At least the peripheral fuel elements in the bundle are provided with spacer elements in the form of thin-walled tubes with longitudinal through slots, wherein the elements have a substantially oval cross section in the regions where they are in contact with the jacket.
	description	This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2007-106025 filed on Apr. 13, 2007, the entire contents of which are incorporated herein by reference. 1. Field of the Invention The present invention relates to an active sensor, a multi-point active sensor, a method of diagnosing deterioration of a pipe, and an apparatus for diagnosing deterioration of a pipe, capable of judging existence of a malfunction such as a pipe wall-thickness reduction caused by a high-temperature steam in an atomic power plant and a heat power plant, and a pipe corrosion in a chemical factory and an incineration plant, and capable of identifying the part having a trouble. 2. Description of Related Art A pipe wall-thickness reduction and a pipe corrosion are conventionally inspected on periodic inspections by using an ultrasonic flaw detecting method and an X-ray transmission method. In the ultrasonic flaw detecting method, a probe that transmits and receives ultrasonic waves is brought into contact with a surface of a pipe, for example, and ultrasonic waves of various frequencies are propagated to an inside (pipe wall part) of the pipe. Then, by receiving the ultrasonic waves that have been reflected on a flaw in the pipe wall part of the pipe or a rear surface of the pipe and returned therefrom, a state of the pipe wall part of the pipe can be grasped. A position of the flaw can be obtained by measuring a time period between the transmittance of the ultrasonic waves and the reception thereof. A size of the flaw can be obtained by measuring a height of the received echo (intensity of the ultrasonic waves that have been reflected and returned) and a range where the echo appears. Such an ultrasonic flaw detecting method is mainly used in an atomic power plant, for detecting a plate thickness and a lamination (side cutting appearing in a cut surface of the plate) of a material, and detecting a fusion deficiency of a fused part and a base material by welding, and a crack generated in a thermally affected part. In addition, with respect to a build up welding for reinforcing a nozzle opening, a branch, and a pipe joint, which are disposed around a pressure vessel of an atomic reactor, the ultrasonic flaw detecting method is applied to a base material directly below a build-up welded part, a fused part, and a build-up deposited part (see, Atomic Energy and Design Technique, Okawa Shuppan, (1980), pp. 226 to 250 (Giitiro Uchigasaki, et al.)). On the other hand, the X-ray transmission method can detect a pipe wall-thickness reduction, without detaching a heat insulation material from the pipe. In the X-ray transmission method, data, which haven been provided by a serial radiographic apparatus such as an X-ray CT scanner, are subjected to a high-speed image processing by using a powerful computer, so as to make an image of the overall object with a fault image showing different X-ray transmittances. Recently, there is known a method capable of simultaneously taking a picture of substances of different X-ray transmittances, by a simple system including only a sheet-like color scintillator (fluorescent screen) and a CCD camera. The color scintillator emits three primary colors of light, i.e., red (R), green (G), and blue (B), with a luminescent ratio changing in accordance with a transmission amount. This method is used for observing a pipe wall-thickness reduction and for inspecting foreign matters in a thermal/atomic power plant and an oil/chemical complex. However, in the above ultrasonic flaw detecting method, it is necessary to measure the thickness of a pipe at not less than 1000 positions, and thus it is difficult to conduct the method during a periodic inspection. Further, when the thickness of the pipe is measured, it is necessary to stop the plant in consideration of a temperature constraint, which results in decrease in availability factor. On the other hand, in the X-ray method capable of detecting a malfunction through the heat insulation member of the pipe, although the method can measure a distribution of the thickness of the pipe, the method is not widely used because an apparatus therefor is expensive. The present invention has been made in view of the above circumstances. The object of the present invention is to provide an active sensor, a multi-point active sensor, a method of diagnosing deterioration of a pipe, and an apparatus for diagnosing deterioration of a pipe, capable of inspecting, while a plant is running, a pipe over a wide area thereof for a short period of time, and of reducing the time and the number of steps required for the inspection, at a low manufacturing cost. The present invention is an active sensor positioned on an outside of a pipe so as to detect a thickness of the pipe, the active sensor comprising: an oscillator capable of inputting oscillatory waves into the pipe and scanning a frequency of the oscillatory waves within a desired range; and an optical fiber sensor mounted on the pipe, the optical fiber sensor detecting the oscillatory waves generated in the pipe. Due to this structure, there can be obtained, at a low manufacturing cost, a thin active sensor capable of simply inspecting a pipe while a plant is running, and of significantly reducing the time and the number of steps required for the inspection. The present invention is an active sensor positioned on an outside or an inside of a pipe so as to detect a thickness of the pipe, the active sensor comprising: an oscillator capable of inputting oscillatory waves into the pipe and scanning a frequency of the oscillatory waves over a desired range; and an optical fiber sensor mounted on the pipe, the optical fiber sensor detecting the oscillatory waves generated in the pipe. Due to this structure, there can be obtained, at a low manufacturing cost, a thin active sensor capable of simply inspecting a pipe while a plant is running, and of significantly reducing the time and the number of steps required for the inspection. The present invention is a multi-point active sensor comprising the plurality of aforementioned active sensors wherein the active sensors are linearly arranged or arranged in matrix. Due to this structure, the thickness of the pipe can be measured and mapped over a wider area, whereby the malfunction of the pipe can be accurately detected. The present invention is a method of diagnosing deterioration of a pipe using the aforementioned multi-point active sensor, the method comprising the steps of: inputting oscillatory waves into a pipe by the oscillator of at least one active sensor; detecting the oscillatory waves generated in the pipe by the optical fiber sensor of at least one active sensor; and calculating a thickness of the pipe by deriving a relationship between a frequency and a vibration strength, based on a frequency of the oscillatory waves inputted by the oscillator into the pipe and an amplitude of the oscillatory waves at this frequency detected by the optical fiber sensor. Due to this structure, the thickness of the pipe can be measured and mapped over a wider area, whereby the malfunction of the pipe can be accurately detected. The present invention is an apparatus for diagnosing deterioration of a pipe, comprising: the aforementioned multi-point active sensor; a waveform analysis unit connected to the respective active sensors, the waveform analysis unit calculating a thickness of a pipe by deriving a relationship between a frequency and a vibration strength, based on a frequency of oscillatory waves inputted by the oscillator of this active sensor into the pipe and an amplitude of the oscillatory waves at this frequency detected by the optical fiber sensor of this active sensor; a diagnostic database storing judgment threshold values relating to the deterioration of the pipe; and a diagnostic unit connected to the waveform analysis unit and the diagnostic database, the diagnostic unit comparing the thickness of the pipe calculated by the waveform analysis unit with the judgment threshold values stored in the diagnostic database, so as to diagnose the deterioration and the malfunction of the pipe. Due to this structure, the deterioration and the malfunction of the pipe can be diagnosed in accordance with a size and a thickness thereof which may differ with the industry and the kind. In addition, it is possible, not only to calculate the thickness of the pipe so as to diagnose the deterioration and the malfunction of the pipe, but also to judge a lifetime of the pipe. The present invention is a method for diagnosing deterioration of a pipe using the aforementioned multi-point active sensor, the method comprising the steps of: passively detecting oscillatory waves generated in a pipe by the optical fiber sensor of at least one active sensor; and analyzing the oscillatory waves generated in the pipe and detected by the optical fiber sensor, so as to detect deterioration and malfunction of the pipe. Due to this structure, the deterioration and the malfunction of the pipe can be detected, without inputting oscillatory waves into the pipe by the oscillator of the active sensor. According to the present invention, by using an active sensor including an oscillator capable of inputting oscillatory waves into a pipe and scanning a frequency of the oscillatory waves within a desired range, and an optical fiber sensor mounted on the pipe, the optical fiber sensor detecting the oscillatory waves generated in the pipe, the pipe can be inspected over a wide area thereof for a short period of time at a low manufacturing cost, while a plant is running. A first embodiment of an active sensor according to the present invention is described below, with reference to the drawings. FIGS. 1 to 8, FIGS. 13(a) and 13(b), and FIG. 14 are views showing the first embodiment of the present invention. As shown in FIGS. 1 and 2, an active sensor 10 is positioned on an outside of a pipe 60, and is used for detecting a thickness of the pipe 60. The active sensor 10 has: an oscillator 15 capable of inputting oscillatory waves (ultrasonic waves) into the pipe 60 and scanning frequencies of the oscillatory waves within a desired range; and an optical fiber sensor 11 mounted on the oscillator 15 on a side of the pipe 60, the optical fiber sensor detecting the oscillatory waves generated in the pipe 60. As shown in FIG. 2, the optical fiber sensor 11 is embedded in a high-temperature adhesive 12 filling a space between a pair of polyimide sheets 19u and 19l. The polyimide sheet 191, which is located on a lower part of FIG. 2, is attached to the pipe 60 with the high-temperature adhesive 12. Between the upper polyimide sheet 19u and the oscillator 15, there is disposed a holding member 13 that prevents a connection between an oscillation caused by the oscillator 15 and an oscillation propagating in the pipe 60 to be tested. In place of attaching the polyimide sheet 191 to the pipe 60 with the high-temperature adhesive 12, the polyimide sheet 191 may be disposed on the pipe 60 by spraying. It is preferable to optimize a size of the optical fiber sensor 11 in accordance with a plate thickness value of the pipe 60 to be measured and an oscillatory wavelength, considering an attenuation of ultrasonic waves propagating in the pipe 60. Specifically, an inner diameter of the optical fiber sensor 11 is preferably not less than 5 mm which is a minimum size capable of avoiding a breaking of the optical fiber sensor 11 by bending. Meanwhile, it is desirable to optimize an outer diameter of the optical fiber sensor 11 based on a wavelength of the oscillatory waves propagating inside the pipe 60. The outer diameter is preferably not more than a value that is obtained by adding, to the inner diameter, one half of the wavelength of the oscillatory waves propagating inside the pipe 60. The standard number of winding turns of the optical fiber sensor 11 is 50. FIGS. 13(a) and 13(b) respectively show a state in which the optical fiber sensor 11 is connected to the pipe 60. In FIGS. 13(a) and 13(b), illustration of the oscillator 16 is omitted and is not shown. The wave lines in FIGS. 13(a) and 13(b) show shapes of oscillatory waves propagating inside the pipe 60. As shown in FIG. 13(a), in a case where the outer diameter of the optical fiber sensor 11 is not more than a value that is obtained by adding, to the inner diameter, one half of the wavelength of the oscillatory waves propagating inside the pipe 60, since amplitudes of the oscillatory waves propagating in aligned sensing part 11a (described below) of the circular or elliptic optical fiber sensor 11 are oriented in the same direction, a large vibration strength can be provided. On the other hand, as shown in FIG. 13(b), in a case where the outer diameter of the optical fiber sensor 11 is larger than a value that is obtained by adding, to the inner diameter, one half of the wavelength of the oscillatory waves propagating inside the pipe 60, the amplitudes of the oscillatory waves propagating in the sensing part 11a undergo vibrations of opposite direction. Namely, since the vibration directions are balanced out by the opposite amplitudes, the vibration strength is lowered. In FIGS. 13(a) and 13(b), the reference number 11r represents a region in which the optical fiber sensor 11 is positioned, i.e., a region between the inner diameter and the outer diameter of the optical fiber sensor 11. FIG. 14 is a graph showing a relationship between the outer diameter of the optical fiber sensor 11 (referred to as “optical fiber sensor outer diameter” in FIG. 14) and the vibration strength. Herein, a thickness of a test piece is 5 mm, a wavelength of oscillatory waves propagating in the test piece is 10.7 mm (sonic velocity: 5800 m/sec), and an inner diameter of the optical fiber sensor 11 is 10 mm. In a case where the outer diameter of the optical fiber sensor 11 is 15 mm, which is a value obtained by adding, to the inner diameter (10 mm) of the optical fiber sensor 11, 5 mm which is about one half of the wavelength of the oscillatory waves, it can be seen that the sufficient vibration strength is obtained. On the other hand, in a case where the outer diameter of the optical fiber sensor 11 is a value obtained by adding, to the inner diameter of the optical fiber sensor 11, a value larger than one half of the oscillatory wavelength (in a case where the outer diameter of the optical fiber sensor 11 is larger than 15 mm), it can be seen that the vibration strength is reduced. The above oscillator 15 is formed from an electromagnet oscillator. To be specific, as shown in FIGS. 1 and 2, the oscillator 15 has a permanent magnet 16 positioned so as to generate a magnetic flux in a normal line direction of a pipe surface 60f (in the A direction shown by the arrow in FIG. 1), and an electric coil 17 disposed on the permanent magnet 16 on a side of the optical fiber sensor 11. In place of disposing the electric coil 17 on the permanent magnet 16 on the side of the optical fiber sensor 11, the electric coil 17 may be wound around the permanent magnet 16. In addition, instead of electric coil 17, there may be used a conductive layer of an optical fiber sensor which is coated with a conductive material such as a metal. The optical fiber sensor 11 is formed from a fiber-optic Doppler (FOD) sensor (see, FIGS. 3(a) to 3(d) that detects a kinetic strain of the pipe 60, which is generated by the oscillatory waves inputted from the oscillator 15 into the pipe 60. With the use of such an optical fiber sensor 11, strains and vibrations can be detected as the Doppler effect of light based on the FOD principle. As shown in FIGS. 1 and 3, the optical fiber sensor 11 has the circularly winding sensing part 11a. As shown in FIGS. 1 and 2, the oscillator 15 is located at a center of the sensing part 11a. The sensing part 11a of the optical fiber sensor 11 are subjected to a heat-resistant process, such as a heat-resistant coating using gold, nickel, silica, and polyimide, and/or a narrow tube. Thus, the active sensor 10 can be mounted on even a position where a temperature thereof is raised to a high temperature (between about 350° C. and 750° C.). As shown in FIG. 3(d), the optical fiber sensor 11 has a core 41 formed from a quartz line or the like, and a clad 42 made of quartz and covering the core 41. As shown in FIG. 3(a), connected to one end of the optical fiber sensor 11 is a light source 5 that supplies a light beam of a predetermined wavelength, such as a laser beam, into the optical fiber sensor 11. Connected to the other end of the optical fiber sensor 11 is a photodetector 6 that detects a deviation of the wavelength which is caused by the kinetic strain in the pipe by the Doppler effect when the light beam has passed through the optical fiber sensor 11. As described above, since the optical fiber sensor 11 is formed from a fiber-optic Doppler (FOD) sensor, the optical fiber sensor 11 is strained in accordance with strain rates (εx; strain rate in an x direction, εy; strain rate in a y direction) generated in the pipe 60, so that a light beam P incident on the optical fiber sensor 11 from the light source 5 at a frequency f0 repeatedly reflects in the core 41 of the sensing part 11a of the optical fiber sensor 11 so as to produce the Doppler effect (see, FIG. 3(d)), and emerges at a frequency f0±fd to the photodetector 6 (see, FIG. 3(a)). FIG. 3(b) is a partial enlarged view of the sensing part 11a of the optical fiber sensor 11. FIG. 3(c) is a further enlarged view of FIG. 3(b). FIG. 3(d) is a view showing a state in which the light beam P repeatedly reflects in the core 41 of the sensing part 11a of the optical fiber sensor 11. The deviation of the frequency fd is concretely represented as the following (Expression 1).fd=neqNπRav(+)/λ0 (Expression 1) in which: neq; transmission refractive index in fiber N; winding number Rav; average winding diameter λ0; wavelength of incident light beam As shown in FIGS. 4(a) and 4(b), by linearly (serially) arranging the plurality of active sensors 10, a multi-point active sensor 20 can be obtained. The respective active sensors 10 are connected to each other by connection members 22 having a plasticity and a flexibility. FIG. 4(a) is a plan view showing the multi-point active sensor 20 from above, and FIG. 4(b) is a side view showing the multi-point active sensor 20 from the lateral side. To be specific, as shown in FIG. 4(a), each of the active sensors 10 is located in the connection member 22 having a projection 23 and a recess 24. The projection 22 of each connection member 22 is fitted in the recess 24 of the adjacent connection member 22, whereby each of the connection members 22 is connected to the connection members 22 adjacent thereto. In FIG. 5 (see, also FIG. 1), connected to each electric coil 17 of the oscillator 15 of the active sensor 10 of the multi-active sensor 20 is an oscillation controller 32 that supplies an alternating current to the electric coil 17. The oscillation controller 32 is provided with a function generator (not shown) capable of scanning a frequency of the alternating current supplied by the oscillation controller 32. In addition, the oscillation controller 32 is capable of adjusting an intensity of the current to be supplied. As shown in FIG. 5, an apparatus for diagnosing deterioration of a pipe is composed of: the above multi-point active sensor 20; a waveform analysis unit 31 connected to the oscillation controller 32 and the photodetector 6, the waveform analysis unit 31 calculating a thickness of the pipe 60; a diagnostic database 33 storing judgment threshold values relating to the deterioration of the pipe 60; and a diagnostic unit 35 connected to the waveform analysis unit 31 and the diagnostic database 33, the diagnostic unit 35 comparing the thickness of the pipe 60 calculated by the waveform analysis unit 31 with the judgment threshold values stored in the diagnostic database 33 so as to diagnose the deterioration of the pipe 60. Herein, the waveform analysis unit 31 calculates the thickness of the pipe 60 by deriving a relationship between a frequency and a vibration strength, based on a frequency of the oscillatory waves inputted into the pipe 60 by the oscillator 15 of the active sensor 10 in the multi-point active sensor 20 and an effective value of an amplitude of the oscillatory waves or a frequency spectral intensity obtained by Fourier converting the oscillatory waves at the frequency detected by the optical fiber sensor 11 of the active sensor 10. Connected to each of the oscillators 15 is a switching mechanism (not shown) which can be selectively switched on and off from a remote position. Thus, it is possible to select the active sensor(s) 10 to be activated in the multi-point active sensor 20. Accordingly, which point(s) of the pipe 60 to be measured can be freely selected. Next, an effect of this embodiment as structured above is described. At first, a relationship between a frequency of oscillatory waves inputted into the pipe 60 by the oscillator 15 of the active sensor 10 and the thickness of the pipe 60 is described. As shown in FIG. 6, when a relationship of “λ=2L” is satisfied between the thickness L of the pipe 60 and the wavelength λ of the oscillatory waves inputted into the pipe 60, the oscillatory waves (incident waves) inputted into the pipe 60 and the oscillatory waves (reflected waves) detected by the optical fiber sensor 11 sympathetically vibrate so that resonant waves are observed. The resonant waves herein mean reflected waves which are observed after the incident waves are stopped (after a time point T1 in FIG. 6). The reference character T0 shows a time point at which the incident waves are started to be inputted, and T1 shows a time point at which the incident operation is stopped. Thus, the thickness L of the pipe 60 can be measured by a reverse operation from the wavelength λ. Namely, when the following condition is satisfied, the ultrasonic wave resonates. 2d=λ Expression (2) in which a thickness of a metal plate is d and a wavelength of an ultrasonic wave is λ. This can be rewritten with a frequency f of the ultrasonic wave to obtain the following Expression (3). Thus, when a resonant frequency and a sonic velocity can be grasped, the plate thickness can be reversely operated. f = v 2 · d - 1 ( v ⁢ : ⁢ ⁢ sonic ⁢ ⁢ velocity = 5900 ⁢ ⁢ m ⁢ / ⁢ sec ) Expression ⁢ ⁢ ( 3 ) For example, in a case where the pipe 60 formed from a steel plate having a thickness of 15 mm is measured, when ultrasonic waves at a frequency of 200 kHz are inputted, the resonance occur. After the optical fiber sensor 11 whose winding number is 50 is attached with an instant adhesive to surfaces of SUS 304 (stainless steel) plates having the same diameter of 200 mm, and thicknesses of 5 mm, 7 mm, 10 mm, 15 mm, 20 mm, 25 mm, and 30 mm, sine waves amplified to 150 Vp-p by an amplifier at every 1 kHz in increment in a range from 50 kHz to 500 kHz are generated. Then, resonant waves corresponding to each frequency can be detected (FIG. 6). Then, when a value obtained by integrating an intensity (voltage value) of the resonant waves in a preset time period relative to the time is defined as “vibration strength”, vibration strengths at the respective frequencies can be derived (see, FIG. 6). From the vibration strengths at the respective frequency as obtained above, a relationship between the frequency and the vibration strength can be derived, which is shown in FIG. 7. From the frequency when the vibration strength is highest (frequency corresponding to the region surrounded by the elliptic circle), the resonant frequency can be derived. FIG. 8 shows a relationship between a resonant frequency and an inverse number of the plate thickness of SUS 304. It can be understood from FIG. 8 that the relationship defined by the Expression (3) is satisfied between the resonant frequency and the inverse number of the plate thickness of SUS304. Next, a method of diagnosing deterioration and malfunction of the pipe 60 is described. At first, oscillatory waves are inputted into the pipe 60 by the oscillators 15 of the active sensors 10 of the multi-point active sensor 20. Specifically, by supplying an alternating current to the electric coil 17 of the oscillator 15 by the oscillation controller 32, the Lorentz force is applied to the permanent magnet 16, to thereby input transversal waves to the pipe 60 in a thickness direction thereof (see, FIGS. 1 and 5). A frequency of the alternating current is changed by using the function generator of the oscillation controller 32, and the alternating current is scanned with a desired frequency bandwidth. By connecting an amplifier to the function generator, it is possible to optionally change both a frequency and an intensity of the input waves. On the occasion of construction or periodic inspection of the pipe 60, such a multi-point active sensor 20 is preferably mounted on an elbow portion and an orifice downstream portion of the pipe 60, which are susceptible to erosion and corrosion. Then, the oscillatory waves generated in the pipe 60 are detected, and are sent to the photodetector 6 by the optical fiber sensor 11 of the active sensor 10 (see, FIG. 5). Since the oscillator 15 is positioned at the center of the sensing part 11a, the oscillatory waves generated in the pipe 60 can be detected with an improved sensitivity (see, FIGS. 1 and 2). In addition, since the optical fiber sensor 11 is formed from a fiber-optic Doppler sensor, the waves can be detected with an excellent sensitivity over a wide frequency bandwidth ranging from 0 Hz (excluding zero) and several MHz. Then, based on a frequency of the oscillatory waves inputted into the pipe 60 by the oscillator 15 of the active sensor 10, and an amplitude of the oscillatory waves at this frequency detected by the optical fiber sensor 11 of this active sensor 10, a relationship between the frequency and the vibration strength is derived by the waveform analysis unit 31 connected to the oscillation controller 32 and the photodetector 6 (see, FIG. 7). Thereafter, the waveform analysis unit 31 derives a resonant frequency based on the relationship between the frequency and the vibration strength, and calculates the thickness of the pipe 60 based on the Expression (3) or the graph shown in FIG. 8. Then, the thickness of the pipe 60 calculated by the waveform analysis unit 31 and the judgment threshold values stored in the diagnostic database 33 are compared to each other, and the deterioration of the pipe 60 or the malfunction of the pipe 60 is diagnosed. In this manner, since the deterioration of the pipe 60 is diagnosed with the use of the judgment threshold values stored in the diagnostic database 33, the pipe 60 can be diagnosed in accordance with its size and thickness, which may differ with the industry and the kind. In addition, it is possible, not only to calculate the thickness of the pipe 60 so as to diagnose the deterioration and the malfunction of the pipe 60, but also to judge a lifetime of the pipe 60. As has been described above, by mounting the multi-point active sensor 20 on the outside of the pipe 60, it is possible to, while a plant is running, calculate the thickness of the pipe 60 so as to diagnose the deterioration and the malfunction of the pipe 60 over a wide area, for a short period of time, without detaching an heat-insulation material from the pipe 60. Thus, the time and the number of steps required for the inspection can be significantly reduced. Accordingly, the time for the periodic inspection can be reduced, and the corrective maintenance service can be improved. As shown in FIGS. 4(a) and 4(b), the respective active sensors 10 included in the multi-point active sensor 20 are connected to each other by the connection members 22 having a plasticity and a flexibility. Thus, the multi-point active sensor 20 can be mounted on a curved portion and an elbow portion of the pipe 60, whereby portions of the pipe 60 where a thickness thereof is prone to be reduced can be inspected. Since the active sensor 10 in this embodiment can be manufactured from the electric coil 17, the permanent magnet 16, and the optical fiber sensor 11, a manufacturing cost for the active sensor 10 is considerably inexpensive. The reliability of the multi-point active sensor 20 can be prolonged, by reducing the size of the oscillator 15 of the active sensor 10 so as to restrain a sensing area, by optimizing a distance between the active sensors 10, by enhancing a connection between the active sensors 10, by enhancing a decomposability when measuring a thickness, by improving a heat-resistant property of the adhesive 12, and by improving an absorbance of the active sensor 10 at an elbow portion of the pipe 60. Further, the use of the smaller oscillator 15, which can be driven at a low voltage, and the optical fiber sensor 11, which can detect a wave with a short FOD gauge length, can enhance practical usefulness. The precision of measuring the thickness of the pipe 60 is determined by parameters such as a power of the oscillatory waves from the oscillator 15 (capacity of the amplifier connected to the function generator), a magnetic force of the permanent magnet 16, the turning number of the electric coil 17, a sensitivity of the optical fiber sensor 11 itself (the turning number of the optical fiber sensor 11), and a heat resistance. In the above embodiment, the oscillator 15 formed from an electromagnetic oscillator is described by way of example. However, not limited thereto, there may be used an oscillator 15 formed from a piezoelectric oscillator having a piezoelectric element. When such a piezoelectric oscillator is used, a strong oscillation can be provided at a lower electric power. Further, in the above embodiment, the optical fiber sensor 11 having the circularly winding sensing part 11a is described by way of example. However, not limited thereto, there may be used an optical fiber sensor 11 having an elliptically winding sensing part. When such an optical fiber sensor 11 having the elliptically winding sensing part is used, the optical fiber sensor 11 can have an anisotropy. Next, an alternative example 1 of the first embodiment is described with reference to FIGS. 9(a) to 9(c). In the alternative example 1 of the first embodiment shown in FIGS. 9(a) to 9(c), in place of using the multi-point active sensor 20 in which the plurality of active sensors 10 are linearly arranged, there is used a multi-point active sensor 20 in which the plurality of active sensors 10 are arranged in matrix. Other structures of the alternative example 1 are substantially the same as those of the first embodiment shown in FIGS. 1 to 8. In the alternative example 1 shown in FIGS. 9(a) to 9(c), the same parts as those in the first embodiment shown in FIGS. 1 to 8 are shown by the same reference numbers, and a detailed description thereof is omitted. As shown in FIG. 9(b), the multi-point active sensor 20 in this embodiment has the plurality of active sensors 10 arranged in matrix. To be more specific, as shown in FIG. 9(b), in the multi-point active sensor 20, there are arranged, in a square area of 100 mm by 100 mm, the nine active sensors 10 of about 30 mmφ in 3×3 matrix. As shown in FIG. 9(c), each of the active sensors 10 included in the multi-point active sensor 20 of the alternative example 1 has: an oscillator 15 mounted on a pipe surface 60f of a pipe 60, the oscillator 15 inputting oscillatory waves into the pipe 60, and an optical fiber sensor 11 mounted on an outer surface of the pipe 60 so as to surround the oscillator 15, the optical fiber sensor 11 detecting oscillatory waves generated in the pipe 60. The oscillator 15 and the optical fiber sensor 11 are attached to the outer surface of the pipe 60 with a heat-resistant adhesive 12 (or tackifier). As shown in FIGS. 9(b) and 9(c), the respective active sensors 10 are connected to each other by a connection member 22a made of a silicon sheet. On the connection member 22a and at an outer periphery of the optical fiber sensor 11, there is disposed a case 29 made of metal or engineering plastic. A space between the oscillator 15 and the case 29 is filled with silicon 27. By using such a multi-point active sensor 20, a thickness of the pipe 60 can be measured and mapped over a wider area, whereby the deterioration and the malfunction of the pipe 60 can be more precisely detected. In the alternative example 1, there is described by way of example the active sensor 10 including the oscillator 15 mounted on the outer surface of the pipe 60 and the optical fiber sensor 11 mounted on the outer surface of the pipe 60 so as to surround the oscillator 15. However, not limited thereto, there may be used an active sensor 10 including an oscillator 15, and an optical fiber sensor 11 mounted on the oscillator 15 on a side of the pipe 60, as shown in the first embodiment. To the contrary, there may be used, as the active sensor in the first embodiment, an active sensor 10 as shown in the alternative example 1 including an oscillator 15 mounted on an outer surface of a pipe 60 and an optical fiber sensor 11 mounted on the outer surface of the pipe 60 so as to surround the oscillator 15. Next, an alternative example 2 of the first embodiment is described with reference to FIG. 10 and FIGS. 11(a) and 11(b). In the alternative example 2 shown in FIG. 10 and FIGS. 11(a) and 11(b), in place of using the oscillator 15 including the permanent magnet 16 positioned so as to generate a magnetic flux in a normal line direction of the pipe surface 60f (in the A direction shown by the arrow in FIG. 10) and the electric coil 17 disposed on the permanent magnet 16 on a side of the optical fiber sensor 11, there is used an oscillator 15 including a pair of permanent magnets 16 positioned so as to generate a magnetic flux in a direction perpendicular to a normal line direction of the pipe surface 60f (in the A direction shown by the arrow in FIG. 10), and an electric coil 17 disposed between the pair of permanent magnets 16. Other structures of the alternative example 2 are substantially the same as those of the first embodiment shown in FIGS. 1 to 8. In the alternative example 2 shown in FIG. 10 and FIGS. 11(a) and 11(b), the same parts as those in the first embodiment shown in FIGS. 1 to 8 are shown by the same reference numbers, and a detailed description thereof is omitted. As shown in FIG. 10 and FIGS. 11(a) and 11(b), the oscillator 15 in this alternative example has the pair of permanent magnets 16 positioned so as to generate a magnetic flux in a direction perpendicular to a normal line direction of the pipe surface 60f, and the electric coil 17 disposed between the pair of permanent magnets 16. Thus, by supplying an alternating current to the electric coil 17 disposed between the pair of permanent magnets 16 from an oscillation controller 32, the Lorentz force can be applied to the pair of permanent magnets 16 positioned so as to generate a magnetic flux in a direction perpendicular to a normal line direction of the pipe surface 60f, to thereby input longitudinal waves into the pipe 60 in a thickness direction thereof (see, FIGS. 5 and 10). As shown in FIG. 11(b), a holding member 13 may be provided between the permanent magnets 16 and a polyimide sheet 19u. Alternatively, as shown in FIG. 11(a), the provision of the holding member 13 between the permanent magnets 16 and the polyimide sheet 19u may be omitted. Next, a second embodiment of the present invention is described with reference to FIG. 12. In the second embodiment shown in FIG. 12, a waveform analysis unit 31 has the following three functions, i.e., (1) a frequency analysis function considering a burst behavior at a high frequency area (discrimination from a steady noise), (2) a behavior observation function of standing waves at a low frequency area (discrimination from a steady noise), and (3) a “steady”/“non-steady” observation function utilizing a neutral network and the like. In addition, a diagnostic database 33 stores information relating to deterioration and malfunction of a pipe 60, the information being to be compared to oscillatory waves generated in the pipe 60 for some reason or other which are detected by an optical fiber sensor 11 of an active sensor 10. Other structures of the second embodiment 2 are substantially the same as those of the first embodiment shown in FIGS. 1 to 8. In the second embodiment shown in FIG. 12, the same parts as those in the first embodiment shown in FIGS. 1 to 8 are shown by the same reference numbers, and a detailed description thereof is omitted. At first, by the optical fiber sensor 11 of the active sensor 10, oscillatory waves generated in the pipe 60 for some reason or other (for example, oscillatory waves caused by a bust impact, or oscillatory waves generated in an abnormal state which do not appear in a steady state) are passively detected (see, FIG. 12). Then, due to the (1) a frequency analysis function considering a burst behavior at a high frequency area (discrimination from a steady noise), (2) a behavior observation function of a standing wave at a low frequency area (discrimination from a steady noise), and (3) a “steady”/“non-steady” observation function utilizing a neutral network and the like, of the waveform analysis unit 31, a waveform of the oscillatory waves generated in the pipe 60 or some reason or other is analyzed. Then, a diagnostic unit 35 analyzes the oscillatory waves detected by the optical fiber sensor 11 of the active sensor 11, referring to the information relating to deterioration and malfunction of the pipe 60, which has been stored in the diagnostic database 33 beforehand, so that the deterioration and the malfunction of the pipe 60 is detected (see, FIG. 5). As shown in the first embodiment, the diagnostic unit 35 can also detect the thickness of the pipe 60 from a resonant frequency derived from an amplitude of the oscillatory waves detected by the optical fiber sensor 11. Thus, according to the apparatus for diagnosing deterioration of a pipe in this embodiment, it is not necessary to input oscillatory waves into the pipe 60 by the oscillator 15 of the active sensor 10, which is necessary in the above first embodiment, but it is possible to passively detect oscillatory waves generated in the pipe 60 for some reason or other, to thereby detect the thickness of the pipe 60 and the deterioration and the malfunction of the pipe 60. Further, with the use of the information relating to the deterioration and the malfunction of the pipe 60, which has been stored in the diagnostic database 33 beforehand, the pipe 60 can be diagnosed in accordance with its size and thickness, which may differ with the industry and the kind. Furthermore, it is possible, not only to calculate the thickness of the pipe 60 so as to diagnose deterioration and malfunction of the pipe 60, but also to judge a lifetime of the pipe 60. According to the present invention, after oscillatory waves are inputted into the pipe 60 by the oscillator 15 of the active sensor 10, the oscillatory waves generated in the pipe 60 can be actively detected by the optical fiber sensor 11 of the active sensor 10, which is shown in as shown in the above first embodiment (including the alternative examples 1 and 2). Alternatively, oscillatory waves generated in the pipe 60 for some reason or other can be passively detected without inputting oscillatory waves into the pipe 60, which is shown in the second embodiment. Therefore, the deterioration and the malfunction of the pipe 60 can be detected with a high probability.
048427730	abstract	The invention is directed to a method for producing a cement product for terminal storage of tritium water wherein activated bentonite capable of swelling is dispersingly mixed with the tritium water and the suspension obtained thereby is subjected to a swelling operation. The swollen suspension is dispersingly mixed with cement. The cured product has a water content of over 75% by weight.
	description	The present invention relates to the technique of processing high-level radioactive waste including fission products. Electric power providers owning nuclear power plants have stored a massive amount of used nuclear fuel, and establishment of the method for safely and effectively processing such used nuclear fuel has been an urgent issue. For this reason, study has been conducted on a nuclear fuel cycle that fissionable U-235 or Pu is extracted from the used nuclear fuel and about 3 to 5% of the resultant is mixed with non-fissionable U-238 to reproduce new fuel. A used nuclear fuel of about 20 tons is annually produced or yielded from a 1000 MWe class nuclear power plant. Used nuclear fuel of 3%-enriched uranium fuel (U-235: 3%, U-238: 97%) contains 1% of U-235, 95% of U-238, 1% of Pu, and 3% of other products. These products are categorized into minor actinide (MA), platinum groups, short-lived fission products (SLFP), and long-lived fission products (LLFP). Note that these products exhibit high neutron absorbing properties, and are the cause of interfering with progress of chain reaction of nuclear fission along with increasing of those amounts. For this reason, these products are much contained in highly active liquid waste (HALW) inevitably caused by reprocessing of the used nuclear fuel and vitrified waste in such a form that the highly active liquid waste can be discarded. When this highly active liquid waste (HALW) is, without change, formed into the vitrified waste for disposal, a massive amount of high-level radioactive waste generating heat needs to be managed for thousands of years, leading to a burden increase. Actually, the vitrified waste has been already held, and therefore, long-term management has been demanded. For these reasons, for the purpose of reducing a burden due to disposal of the highly active liquid waste (HALW) and management of the already-held vitrified waste, study has been conducted on the technique of separating contained nuclides into groups according to a half-life or chemical properties and selecting, for each group, a disposal method according to properties. Thus, a storage period of the high-level radioactive waste can be shortened, and a storage space can be further saved. For the groups with the long-lived fission products (LLFP) among the groups separated from the highly active liquid waste (HALW) and the vitrified waste, study has been conducted on application of the technique of nuclear transmutation into short-lived radionuclides or stable nuclides. Specifically, the technique of nuclear transmutation into isotopes with a shorter half-life by application of photonuclear reaction (γ, n) for irradiating the long-lived fission products (LLFP) with a gamma beam to cause neutron emission or neutron capture reaction (n, γ) for irradiating the long-lived fission products (LLFP) with neutrons to cause gamma beam emission has been disclosed (e.g., Patent Literatures 1 and 2). Patent Literature 1: JP1993-119178A Patent Literature 2: WO00/00986 However, in the above-described photonuclear reaction (γ, n) or neutron capture reaction (n, γ), long-lived radionuclides which can be efficiently nuclear-transmuted are limited due to high nuclide dependency of a reaction cross section. For this reason, the long-lived radionuclides may be directly irradiated with a high-energy beam, or may be indirectly irradiated with a secondary beam generated from the high-energy beam. In this manner, nuclear transmutation can be effective. Group separation as described above is based on element separation, and is not accompanied by isotope separation. Thus, even when the long-lived fission products (LLFP) are separated into the groups, not only isotopes of the long-lived radionuclides but also isotopes of the short-lived radionuclides and the stable nuclides might be present in a mixed manner. For this reason, when the groups with the long-lived fission products (LLFP) are, without thinking, irradiated with the high-energy beam to perform nuclear transmutation processing, there are concerns that the long-lived radionuclides are not only transmuted into the short-lived radionuclides or the stable nuclides, but also the short-lived radionuclides or the stable nuclides are nuclear-transmuted into the long-lived radionuclides. Thus, the nuclear transmutation processing of extracting only the long-lived radionuclides by isotope separation is conceivable, but is not practical due to low productivity of isotope separation processing in a current situation. Moreover, practically-applicable elements are limited in such isotope separation processing, and therefore, there is a limitation on application for the purpose of detoxifying of the long-lived fission products (LLFP) or re-utilization of the long-lived fission products (LLFP) as useful elements. One or more embodiments of the present invention are directed to a fission product processing method for selective nuclear transmutation, without isotope separation, only the radionuclides into stable nuclides in the fission products. In one or more embodiments of the present invention, a method for processing radioactive waste includes the step of extracting, from the radioactive waste, the isotopes without isotope separation, the isotopes including radionuclides of fission products and having a common atomic number, and the step of irradiating the isotopes with high-energy particles generated by an accelerator to produce nuclear transmutation of a long-lived radionuclide of the radionuclides into a short-lived radionuclide with a short half-life or a stable nuclide re-utilizable as a resource. According to one or more embodiments of the present invention, the fission product processing method for selective nuclear transmutation, without isotope separation, only the radionuclides into stable nuclides in the fission products is provided. Further, a radioactive waste processing method can be provided so that the stable nuclides transmuted from the long-lived radionuclides or the like can be re-utilized as the resource. An embodiment of the present invention will be described below based on the attached drawings. As shown in FIG. 1, the method for processing radioactive waste according to the embodiment includes the step (S11) of separating and extracting, from the radioactive waste, the isotopes including radionuclides of fission products and having a common atomic number, and the step (S13) of irradiating the isotopes with high-energy particles generated by an accelerator to produce nuclear transmutation of long-lived radionuclides or mid-lived radionuclides into short-lived radionuclides with a short half-life or stable nuclides. The method further includes, after the separation extraction step (S11) and before the nuclear transmutation step (S13), the step (S12) of concentrating, based on parity on a concentration effect, the isotopes into any one of an isotopes with an odd number of neutrons and an isotopes with an even number of neutrons. Radioactive waste including fission products (FP) is assumed as the radioactive waste targeted for application in the present embodiment. These fission products (FP) indicate two or more nuclides separated by nuclear fission of fissionable nuclides such as uranium U-235 and plutonium Pu-239. The element types of the fission product (FP) of the uranium U-235 are about 40 types from nickel (atomic number 28) to dysprosium (atomic number 66). Yield distribution on the mass number of the fission product (FP) of the uranium U-235 is across a range of 72 to 160, and is in a double peak shape with local maximum values around a mass number of 90 and a mass number of 140. As described above, there are several hundred types of fission products (FP) when distinguished according to isotopes, and these fission products (FP) are further categorized into stable nuclides and radionuclides. Of these nuclides, the radionuclides are changed into more stable nuclides by nuclear decay. Short-lived radionuclides with a short half-life of nuclear decay emit a massive amount of radiation in a short amount of time, but radioactivity rapidly attenuates as time proceeds. For this reason, such radionuclides can be detoxified by storage for a predetermined period of time. On the other hand, long-lived radionuclides with a long half-life emit a less amount of radiation, but the speed of attenuation is slower. For this reason, semi-permanent management is necessary in the case of massive possession. Thus, when nuclear transmutation of the long-lived radionuclides into the short-lived radionuclides or the stable nuclides can be produced, a burden due to management of the radioactive waste can be reduced. Major long-lived radionuclides (a half-life in parentheses) included in the fission products (FP) include, for example, selenium Se-79 (2.95×105 years), palladium Pd-107 (6.5×106 years), zirconium Zr-93 (1.5×106 years), cesium Cs-135 (2.3×106 years), iodine I-129 (1.57×107 years), technetium Tc-99 (2.1×105 years), and tin Sn-126 (2.3×105 years). For iodine I-129 (1.57×107 years) and technetium Tc-99 (2.1×105 years) of these radionuclides, examples showing effective life shortening by neutron capture reaction (n, γ) have been reported. For this reason, iodine I-129 and technetium Tc-99 are left out of consideration in the present embodiment, but the present invention is applicable to these radionuclides. Note that in the present embodiment, radionuclides with a half-life of equal to or longer than 1010 years are regarded as metastable nuclides, and are excluded from processing targets. Strontium Sr-90 (28.8 years), krypton Kr-85 (10.8 years), and samarium Sm-151 (90 years) as major fission products (FP) for mid-lived radionuclides with a half-life of exceeding 10 years are, even if these products are other than the above-described long-lived radionuclides, included in the processing targets for further life shortening, and study has been conducted on these products. The separation extraction step (S11) of FIG. 1 is the step of separating and extracting, from the radioactive waste including various types of nuclides, the isotopes including the focused long-lived radionuclides. That is, the isotopes having the same atomic number (the number of protons) Z as that of the focused long-lived radionuclides and having different mass numbers (the number of protons+the number of neutrons) A is extracted. A typical element separation method can be applied as such a method for separating and extracting the isotopes, and for example, includes an electrolytic method, a solvent extraction method, an ion exchanging method, a precipitation method, a dry method, or a combination thereof. In a case where vitrified waste is targeted, the vitrified waste needs to be melted or decomposed at a step before separation extraction. A typical melting/decomposition method can be applied, and for example, includes an alkali fusion method, a molten-salt method (electrolysis reduction, chemical reduction), a high-temperature fusion method, a halogenation method, an acid solution method, and an alkali melting method. After the vitrified waste has been melted or decomposed, the above-described typical element separation method can be applied. The even-odd concentration step (S12) of FIG. 1 is the step of performing, for the isotopes subjected to the separation extraction step (S11), the processing of concentrating, based on the parity on the concentration effect, the isotopes into any one of the isotopes with the odd number of neutrons and the isotopes with the even number of neutrons. After this even-odd concentration step (S12), the efficiency of the subsequent nuclear transmutation processing step (S13) is enhanced. Thus, this even-odd concentration step (S12) is not an essential step, and is not sometimes performed considering a total cost. In general, isotope separation is performed utilizing a slight physical property difference or a slight mass difference, such as an isotope vapor pressure. An isotopic shift phenomenon has been known, in which the number of vibration of an atomic spectral line slightly shifts among isotopes, and an optical transition selection rule on light polarization varies among odd-number isotopes and even-number isotopes. Utilizing such a phenomenon, the isotopes separated and extracted at (S11) can be, at (S12), concentrated into any one of the isotopes with the odd number of neutrons and the isotopes with the even number of neutrons. Such an even-odd concentration step (S12) may use such properties that in the case of an even number of neutrons, the transition selection rule in the course of electronic excitation by a right/left circular polarization laser varies among even-even nuclei and even-odd nuclei with a nuclear spin of zero. Specifically, only odd-number nuclides can be ionized by laser irradiation with a laser of which polarization has been controlled. Note that the method applied to the even-odd concentration step (S12) is not specifically limited. The nuclear transmutation processing step (S13) of FIG. 1 will be described below separately for each type of irradiated high-energy particle and each type of separated and extracted isotopes. (Secondary Neutron Emission Reaction; (n, xn) Reaction (x≥2)) First, a case where the high-energy particles with which the isotopes is irradiated are neutrons (n) will be described. The neutrons do not receive clone force due to the charge of atomic nuclei, and therefore, tend to enter the atomic nuclei to produce nucleus reaction. Typically in a case where neutrons with low energy enter atomic nuclei, elastic scattering ((n, n) reaction) in which the sum of kinetic energy before and after entering is conserved is dominant. However, when the energy of the neutrons increases to above hundreds of kilo electron volts, inelastic scattering in which the sum of kinetic energy before and after entering is not conserved begins to occur. Then, when the energy of the neutrons reaches equal to or higher than 1 MeV, reaction for emitting charged particles, such as (n, p) reaction or (n, α) reaction, is produced. When the energy of the neutrons reaches 7 to 8 MeV, (n, 2n) reaction begins to occur, and therefore, secondary neutrons are emitted. Then, when the energy of the neutrons further increases, (n, 3n) reaction is produced. The (n, 2n) reaction described herein is reaction that two neutrons are emitted from an atomic nucleus when a single neutron enters the atomic nucleus. The (n, 3n) reaction described herein is reaction that three neutrons are emitted from an atomic nucleus when a single neutron enters the atomic nucleus. The magnitude of energy for separating and emitting a secondary neutron by entering of a primary neutron into an atomic nucleus shows tendency depending on the parity of the number of neutrons. In general, energy is lower in the case of taking a single neutron out of an atomic nucleus with an odd number of neutrons than in the case of taking a single neutron out of an atomic nucleus with an even number of neutrons. Selective nuclear transmutation of a long-lived radionuclide or a mid-lived radionuclides into a short-lived radionuclide or a stable nuclide based on the parity of neutron separation energy of an isotope element by proper setting of neutron irradiation energy will be described below for each type of isotopes targeted for processing. FIG. 2A is a graph of a neutron emission reaction cross section of a selenium isotope (Se) with respect to the neutron irradiation energy. FIG. 2B is the chart of nuclides of major isotopes including bromine Br, selenium Se, and arsenic As. For the Se isotopes, only Se-74, 76, 77, 78, 80, 82 as stable nuclides and Se-79 (a half-life of 2.95×105 years) as a long-lived radionuclide remain in the course of storage for a certain period of time and the separation extraction step (FIG. 1; S11), and almost all of other isotopes are transmuted due to nuclear decay. Of these Se isotopes, a target for transmutation is Se-79 as the long-lived radionuclide. As shown in FIG. 2A, when the neutron irradiation energy increases, the (n, 2n) reaction cross sections of Se-77 and Se-79 with an odd number of neutrons begin to increase at around the point of exceeding 7 MeV. Each nuclide loses a single neutron, leading to nuclear transmutation of these nuclides into Se-76 and Se-78. When the neutron irradiation energy further increases, the (n, 2n) reaction cross sections of Se-76, Se-78, and Se-80 with an even number of neutrons begin to increase at around the point of exceeding 10 MeV. This leads to nuclear transmutation of these nuclides into Se-75, Se-77, and Se-79. Then, the (n, 2n) reaction cross sections of these Se isotopes reach a constant value at around the point of exceeding 14 MeV. When the neutron irradiation energy still further increases, a (n, 3n) reaction cross section begins to increase at around the point of exceeding 18 MeV. Of nuclear transmutation of the Se isotopes as shown in FIG. 2B, disadvantageous side (n, 2n) reaction is nuclear transmutation of Se-80 as the stable nuclide into Se-79 as the long-lived radionuclide. Note that nuclear transmutation of Se-82 as the stable nuclide into Se-81 as a short-lived radionuclide is acceptable because of nuclear decay of Se-81 into Br-81 (a stable nuclide) within a short period of time. Thus, for selective transmutation of only Se-79 as the long-lived radionuclide from the Se isotopes, the value of the neutron irradiation energy is preferably set within such a range that the (n, 2n) reaction cross section of Se-79 is equal to or larger than 10 times as large as the (n, 2n) reaction cross section of Se-80, specifically a range of 7.5 MeV to 10.3 MeV. Note that in the case of setting the neutron irradiation energy within such a range, the (n, 2n) reaction of Se-77 as the stable nuclide is also produced. However, this is not an issue because nuclear transmutation of Se-77 into Se-76 as the stable nuclide is produced. FIG. 3A shows a graph of a neutron emission reaction cross section of a palladium isotope (Pd) with respect to the neutron irradiation energy. FIG. 3B is the chart of nuclides of major isotopes including silver Ag, palladium Pd, and rhodium Rh. For the Pd isotopes, only Pd-102, 104, 105, 106, 108, 110 as stable nuclides and Pd-107 (a half-life of 6.5×106 years) as a long-lived radionuclide remain in the course of storage for a certain period of time and the separation extraction step (FIG. 1; S11), and almost all of other isotopes are transmuted due to nuclear decay. Of these Pd isotopes, a target for transmuted is Pd-107 as the long-lived radionuclide. As shown in FIG. 3A, when the neutron irradiation energy increases, the (n, 2n) reaction cross sections of Pd-105 and Pd-107 with an odd number of neutrons begin to increase at around 7 MeV. Each nuclide loses a single neutron, leading to nuclear transmutation of these nuclides into Pd-104 and Pd-106. When the neutron irradiation energy further increases, the (n, 2n) reaction cross sections of Pd-102, 104, 106, 108, 110 with an even number of neutrons begin to increase at around the point of exceeding 9 MeV. This leads to nuclear transmutation of these nuclides into Pd-101, 103, 105, 107, 109. Then, the (n, 2n) reaction cross sections of these Pd isotopes reach a constant value at around the point of exceeding 11 MeV. When the neutron irradiation energy still further increases, a (n, 3n) reaction cross section begins to increase at around the point of exceeding 16 MeV. Of nuclear transmutation of the Pd isotopes as shown in FIG. 3B, disadvantageous side (n, 2n) reaction is nuclear transmutation of Pd-108 as the stable nuclide into Pd-107 as the long-lived radionuclide. Thus, for selective transmutation of only Pd-107 as the long-lived radionuclide from the Pd isotopes, the value of the neutron irradiation energy is preferably set within such a range that the (n, 2n) reaction cross section of Pd-107 is equal to or larger than 10 times as large as the (n, 2n) reaction cross section of Pd-108, specifically a range of 7 MeV to 9.5 MeV. Note that in the case of setting the neutron irradiation energy within such a range, nuclear transmutation of Pd-110 as the stable nuclide into Pd-109 (a half-life of 13.7 hours) as a short-lived radionuclide is produced by the (n, 2n) reaction. However, this is acceptable because nuclear decay of Pd-109 into Ag-109 as a stable nuclide is produced. Moreover, the (n, 2n) reaction of Pd-105 as the stable nuclide is also produced. However, this is not an issue because nuclear transmutation of Pd-105 into Pd-104 as the stable nuclide is produced. FIG. 4A shows a graph of a neutron emission reaction cross section of a zirconium isotope (Zr) with respect to the neutron irradiation energy. FIG. 4B is the chart of nuclides of major isotopes including molybdenum Mo, niobium Nb, and zirconium Zr. For the Zr isotopes, only Zr-90, 91, 92, 94, 96 as stable nuclides and Zr-93 (a half-life of 1.5×106 years) as a long-lived radionuclide remain in the course of storage for a certain period of time and the separation extraction step (FIG. 1; S11), and almost all of other isotopes are transmuted due to nuclear decay. Of these Zr isotopes, a target for transmutation is Zr-93 as the long-lived radionuclide. As shown in FIG. 4A, when the neutron irradiation energy increases, the (n, 2n) reaction cross sections of Zr-91, 93, 95 with an odd number of neutrons begin to increase at around 7 MeV. Each nuclide loses a single neutron, leading to nuclear transmutation of these nuclides into Zr-90, 92, 94. When the neutron irradiation energy further increases, the (n, 2n) reaction cross sections of Zr-92, 94, 96 with an even number of neutrons begin to increase at around 8 MeV. This leads to nuclear transmutation of these nuclides into Zr-91, 93, 95. When the neutron irradiation energy still further increases, a (n, 3n) reaction cross section begins to increase at around the point of exceeding 15 MeV. Of nuclear transmutation of the Zr isotopes as shown in FIG. 4B, disadvantageous side (n, 2n) reaction is nuclear transmutation of Zr-94 as the stable nuclide into Zr-93 as the long-lived radionuclide. Thus, for selective transmutation of only Zr-93 as the long-lived radionuclide from the Zr isotopes, the value of the neutron irradiation energy is preferably set within such a range that the (n, 2n) reaction cross section of Zr-93 is equal to or larger than 10 times as large as the (n, 2n) reaction cross section of Zr-94, specifically a range of 7.2 MeV to 8.7 MeV. Note that in the case of setting the neutron irradiation energy within such a range, nuclear transmutation of Zr-96 as the stable nuclide into Zr-95 (a half-life of 64.0 days) as a short-lived radionuclide is produced by the (n, 2n) reaction. However, this is acceptable because nuclear decay of Zr-95 into Nb-95 (a half-life of 35.0 days) as a short-lived radionuclide is produced and nuclear decay of Nb-95 into Mo-95 as a stable nuclide is further produced. Moreover, the (n, 2n) reaction of Zr-91 as the stable nuclide is also produced. However, this is not an issue because nuclear transmutation of Zr-91 into Zr-90 as the stable nuclide is produced. FIG. 5A shows a graph of a neutron emission reaction cross section of a kypton isotope (Kr) with respect to the neutron irradiation energy. FIG. 5B is the chart of nuclides of major isotopes including rubidium (Rb), kypton Kr, and bromine Br. For the Kr isotopes, only Kr-78, 80, 82, 83, 84, 86 as stable nuclides, Kr-81 (a half-life of 2.3×105 years) as a long-lived radionuclide, and Kr-85 (a half-life of 10.8 years) as a mid-lived radionuclide remain in the course of storage for a certain period of time and the separation extraction step (FIG. 1; S11), and almost all of other isotopes are transmuted due to nuclear decay. Of these Kr isotopes, a target for transmutation is Kr-85 as the mid-lived radionuclide. Note that the abundance of Kr-81 (a half-life of 2.29×105 years) of the Kr isotopes included in the radioactive waste is slight, and therefore, Kr-81 is taken out of consideration. As shown in FIG. 5A, when the neutron irradiation energy increases, the (n, 2n) reaction cross sections of Kr-85 and Kr-83 with an odd number of neutrons begin to increase at around the point of exceeding 7.5 MeV. Each nuclide loses a single neutron, leading to nuclear transmutation of these nuclides into Kr-84 and Kr-82. When the neutron irradiation energy further increases, the (n, 2n) reaction cross sections of Kr-86, Kr-84, and Kr-82 with an even number of neutrons begin to increase at around the point of exceeding 9.8 MeV. This leads to nuclear transmutation of these nuclides into Kr-85, Kr-83, and Kr-81. Then, the (n, 2n) reaction cross sections of these Kr isotopes reach a constant value at around the point of exceeding 14 MeV. When the neutron irradiation energy still further increases, a (n, 3n) reaction cross section begins to increase at around the point of exceeding 18.5 MeV. Of nuclear transmutation of the Kr isotopes as shown in FIG. 5B, disadvantageous side (n, 2n) reaction is nuclear transmutation of Kr-86 as the stable nuclide into Kr-85 as the mid-lived radionuclide. Thus, for selective transmutation of only Kr-85 as the mid-lived radionuclide from the Kr isotopes, the value of the neutron irradiation energy is preferably set within such a range that the (n, 2n) reaction cross section of Kr-85 is equal to or larger than 10 times as large as the (n, 2n) reaction cross section of Kr-86, specifically a range of 7.5 MeV to 10 MeV. Note that in the case of setting the neutron irradiation energy within such a range, the (n, 2n) reaction of Kr-83 as the stable nuclide is also produced. However, this is not an issue because nuclear transmutation of Kr-83 into Kr-82 as the stable nuclide is produced. FIG. 6A shows a graph of a neutron emission reaction cross section of a samarium isotope (Sm) with respect to the neutron irradiation energy. FIG. 6B is the chart of nuclides of major isotopes including europium (Eu), samarium (Sm), and promethium (Pm). For the Sm isotopes, only Sm-150, 152, 154 as stable nuclides, Sm-148, 149 as metastable nuclides, and Sm-151 (a half-life of 90 years) as a mid-lived radionuclide remain in the course of storage for a certain period of time and the separation extraction step (FIG. 1; S11), and almost all of other isotopes are transmuted due to nuclear decay. Of these Sm isotopes, a target for transmutation is Sm-151 as the mid-lived radionuclide. Note that the abundance of each of Sm-146 (a half-life of 1.03×108 years) and Sm-147 (a half-life of 1.06×1011 years) of the Sm isotopes included in the radioactive waste is slight, and therefore, Sm-146 and Sm-147 are taken out of consideration. As shown in FIG. 6A, when the neutron irradiation energy increases, the (n, 2n) reaction cross sections of Sm-151 and Sm-149 with an odd number of neutrons begin to increase at around the point of exceeding 5.8 MeV. Each nuclide loses a single neutron, leading to nuclear transmutation of these nuclides into Sm-150 and Sm-148. When the neutron irradiation energy further increases, the (n, 2n) reaction cross sections of Sm-148, Sm-150, Sm-152, and Sm-154 with an even number of neutrons begin to increase at around the point of exceeding 8 MeV. This leads to nuclear transmutation of these nuclides into Sm-147, Sm-149, Sm-151, and Sm-153. Then, the (n, 2n) reaction cross sections of these Sm isotopes reach a constant value at around the point of exceeding 11 MeV. When the neutron irradiation energy still further increases, a (n, 3n) reaction cross section begins to increase at around the point of exceeding 14.3 MeV. Of nuclear transmutation of the Sm isotopes as shown in FIG. 6B, disadvantageous side (n, 2n) reaction is nuclear transmutation of Sm-152 as the stable nuclide into Sm-151 as the mid-lived radionuclide. Thus, for selective transmutation of only Sm-151 as the mid-lived radionuclide from the Sm isotopes, the value of the neutron irradiation energy is preferably set within such a range that the (n, 2n) reaction cross section of Sm-151 is equal to or larger than 10 times as large as the (n, 2n) reaction cross section of Sm-152, specifically a range of 5.8 MeV to 8.3 MeV. Note that in the case of setting the neutron irradiation energy within such a range, the (n, 2n) reaction of Sm-148, 149 as the metastable nuclides is also produced. However, this is not an issue because nuclear transmutation of Sm-148, 149 into Sm-147, 148 which are also the metastable nuclides is produced. Similarly, the (n, 2n) reaction of Sm-150 as the stable nuclide is also produced. However, this is not an issue because nuclear transmutation of Sm-150 into Sm-148 as the metastable nuclide is produced. Similarly, the (n, 2n) reaction of Sm-154 as the stable nuclide is also produced. However, this is not an issue because β− decay of Sm-153 as a short-lived radionuclide into Eu-153 as a stable nuclide is produced within a short period of time after nuclear transmutation of Sm-154 into Sm-153. FIG. 7A shows a graph of a neutron emission reaction cross section of a cesium isotope (Cs) with respect to the neutron irradiation energy. FIG. 7B is the chart of nuclides of major isotopes including barium Ba, cesium Cs, and xenon Xe. For the Cs isotopes, only Cs-133 as a stable nuclide, Cs-134 (a half-life of 2.07 years) as a mid-lived radionuclide, Cs-135 (a half-life of 2.3×106 years) as a long-lived radionuclide, and Cs-137 (a half-life of 30.07 years) as a mid-lived radionuclide remain in the course of storage for a certain period of time and the separation extraction step (FIG. 1; S11), and almost all of other isotopes are transmuted due to nuclear decay. Of these Cs isotopes, targets for transmutation are Cs-135 as the long-lived radionuclide and Cs-137 as the mid-lived radionuclide. A difference of Cs from Se, Pd, and Zr described so far is that the number of neutrons of Cs-135 as the long-lived radionuclide is an even number, and therefore, the energy required for the (n, 2n) reaction of such a long-lived radionuclide is higher than that for the isotope nuclide with an odd number of neutrons. As shown in FIG. 7A, when the neutron irradiation energy increases, the (n, 2n) reaction cross section of Cs begins to increase at around 7 MeV. Each of Cs-133, 134, 135, 137 loses a single neutron, leading to nuclear transmutation of these nuclides into Cs-132, 133, 134, 136. Then, the (n, 2n) reaction cross section of Cs reaches a constant value at around the point of exceeding 11 MeV. When the neutron irradiation energy further increases, a (n, 3n) reaction cross section begins to increase at around the point of exceeding 16 MeV. As shown in FIG. 7B, nuclear transmutation of Cs-133 into Cs-132 (a half-life of 6.48 days) as a short-lived radionuclide is produced by the (n, 2n) reaction. Nuclear decay (β+ decay) of Cs-132 into Xe-132 as a stable nuclide is produced. Then, nuclear transmutation of Cs-134 into Cs-133 as the stable nuclide is produced by the (n, 2n) reaction. Nuclear transmutation of Cs-135 into Cs-134 (a half-life of 2.07 years) as the mid-lived radionuclide is produced by the (n, 2n) reaction, and nuclear decay (β− decay) of Cs-134 into Ba-134 as a stable nuclide is produced. Nuclear transmutation of Cs-137 into Cs-136 (a half-life of 13.2 days) as a short-lived radionuclide is produced by the (n, 2n) reaction, and nuclear decay (β− decay) of Cs-136 into Ba-136 as a stable nuclide is produced. Of nuclear transmutation of the Cs isotopes, disadvantageous side (n, xn) reaction is nuclear transmutation of Cs-137 as the mid-lived radionuclide into Cs-135 as the long-lived radionuclide by (n, 3n) reaction. Thus, for selective transmutation of Cs-135 as the long-lived radionuclide or Cs-137 as the mid-lived radionuclide from the Cs isotopes, the value of the neutron irradiation energy is preferably set within such a range that the (n, 2n) reaction cross section of Cs-137 is equal to or larger than 100 times as large as the (n, 3n) reaction cross section of Cs-137, specifically a range of 8.5 MeV to 16.2 MeV. Note that in the case of setting the neutron irradiation energy within such a range, when Cs-136 subjected to nuclear transmutation from Cs-137 by the (n, 2n) reaction is further irradiated with neutrons, there is a concern that nuclear transmutation of such a nuclide into Cs-135 as the long-lived radionuclide is produced by the (n, 2n) reaction. For this reason, the flow of the processing of the Cs isotope as illustrated in FIG. 8 will be discussed. After the radioactive waste has been left uncontrolled for a predetermined period of time, nuclear decay of the contained short-lived radionuclides is produced (S21). Subsequently, the Cs isotopes are separated and extracted from the radioactive waste (S22), and then, are irradiated with neutrons to produce the (n, 2n) reaction (S23). At this step of (S23), Cs-136 nuclear-transmuted from Cs-137 is, in some cases, further nuclear-transmuted, thereby generating Cs-135 as the long-lived radionuclide. For this reason, the short-lived radionuclides such as Cs-136 are left uncontrolled for a predetermined period of time again, and are transmuted by atomic nuclear decay (S24). Then, stable isotopes of other elements than Cs are extracted, the stable isotopes being generated by nuclear decay as described above (S25). The step (S25) of extracting the stable isotopes of other elements than Cs is not only for the purpose of eliminating disadvantageous side reaction at the subsequent neutron irradiation step (S23), but also for the purpose of obtaining useful isotope elements. For example, only Xe-132 of multiple stable isotopes can be separated from Cs-133 by way of Cs-132. As long as Cs-137 is present, a certain percentage of Cs-136 nuclear-transmuted by the (n, 2n) reaction is inevitably nuclear-transmuted into Cs-135 as the long-lived radionuclide (Yes at S26). For this reason, by repeating the flow from (S23) to (Yes at S26), Cs-137 can be transmuted, and Cs-135 as the long-lived radionuclide can be also transmuted (No at S26). In this manner, detoxifying of the Cs isotopes is realized (END after S27). Moreover, by repeating the flow as described above, nuclear transmutation of Cs-135 into Xe-132 as a useful element by way of Cs-133 is produced, and Xe-132 is extracted. FIG. 9A shows a graph of a neutron emission reaction cross section of a strontium isotope (Sr) with respect to the neutron irradiation energy. FIG. 9B is the chart of nuclides of major isotopes including yttrium Y, strontium Sr, and rubidium Rb. For the Sr isotopes, only Sr-84, 86, 87, 88 as stable nuclides and Sr-90 (a half-life of 28.8 years) as a mid-lived radionuclide remain in the course of storage for a certain period of time and the separation extraction step (FIG. 1; S11), and almost all of other isotopes are transmuted due to nuclear decay. As shown in FIG. 9A, when the neutron irradiation energy increases, the (n, 2n) reaction cross section of Sr-89 begins to increase at around 6.8 MeV. Subsequently, the (n, 2n) reaction cross section of Sr-90 begins to increase at around 8.2 MeV. Thus, each of Sr-89, 90 loses a single neutron, leading to nuclear transmutation of these nuclides into Sr-88, 89. Sr-89 nuclear-transmuted from Sr-90 is further transmuted into Sr-88 (the stable nuclide) by the (n, 2n) reaction. As shown in FIG. 9B, any of other Sr isotope elements than Sr-90 are a stable nuclide or a short-lived radionuclide. Thus, new long-lived and med-lived radionuclides are not generated even by the (n, 2n) reaction of all of the Sr isotopes. For this reason, for transmutation of Sr-90, the even-odd concentration step (S12) is not necessarily undergone, and even-odd selection is not necessarily utilized for the neutron irradiation energy. For transmutation of Sr-90 as the mid-lived radionuclide of the Sr isotopes, the value of the neutron irradiation energy may be specifically set to equal to or greater than 8.2 MeV. Note that even when nuclear transmutation of Sr-86 (the stable nuclide) into Sr-85 (a half-life of 64.8 days) by irradiation with equal to or greater than 12 MeV is produced, this is not an issue because Sr-85 is transmuted into Rb-85 (a stable nuclide) by β+ decay. FIG. 10A shows a graph of a neutron emission reaction cross section of a tin isotope (Sn) with respect to the neutron irradiation energy. FIG. 10B is the chart of nuclides of major isotopes including tellurium Te, antimony Sb, and tin Sn. For the Sn isotopes, only Sn-112, 114, 115, 116, 117, 118, 119, 120, 122, 124 as stable nuclides and Sn-126 (a half-life of 1×105 years) as a long-lived radionuclide remain in the course of storage for a certain period of time and the separation extraction step (FIG. 1; S11), and almost all of other isotopes are transmuted due to nuclear decay. As shown in FIG. 10A, when the neutron irradiation energy increases, the (n, 2n) reaction cross section of Sn-119 begins to increase at around 6.8 MeV. Subsequently, the (n, 2n) reaction cross section of Sn-126 begins to increase at around 8.2 MeV. As shown in FIG. 10B, any of other Sn isotope elements than Sn-126 are a stable nuclide or a short-lived radionuclide. Thus, new long-lived and med-lived radionuclides are not generated even by the (n, 2n) reaction of all of the Sn isotopes. For this reason, for transmutation of Sn-126, the even-odd concentration step (S12) is not necessarily undergone, and even-odd selection is not necessarily utilized for the neutron irradiation energy. For transmutation of Sn-126 as the long-lived radionuclide of the Sn isotopes, the value of the neutron irradiation energy may be specifically set to equal to or greater than 8.2 MeV. Note that even when nuclear transmutation of the stable nuclide of Sn is produced by irradiation with equal to or greater than 8.2 MeV, this is not an issue because a stable nuclide of another element is generated by further β− decay or β+ decay. (Neutron Beam Generation Device) A secondarily-generated beam generated utilizing an accelerator is applied as a neutron beam for inducing the (n, 2n) reaction of the isotopes. In this accelerator, protons are accelerated to energy slightly higher than target neutron energy, and a target is irradiated with the protons. In this manner, neutrons are generated. Alternatively, in this accelerator, deuterons are accelerated to total energy about twice as high as target neutron energy, and a target is irradiated with the deuterons. In this manner, neutrons are generated. Such a target structure is designed to control the strength and profile (the degree of convergence) of the generated neutrons, and therefore, a beam-shaped neutron bundle is output. (Muon Nuclear Capture Reaction) Next, a case where the high-energy particles with which the isotopes is irradiated are muon μ− will be described based on FIG. 11. Note that muon includes positive muon μ+ and negative muon μ−. The present invention is targeted for the negative muon and therefore, the muon described below all indicates the negative muon. When the muon μ− is captured by an atomic nucleus of an element X, one of protons forming the atomic nucleus is transmuted into a neutron when bonded to the muon μ−. Then, a neutrino ν is emitted (Reaction Formula (1)). Then, nuclear transmutation into an element Y with a (Z−1) atomic nucleus of which number of protons is reduced by one is produced. As shown in Reaction Formulae (2) to (5), such an element Y shows an excited state, and the nucleus reaction for emitting one or more neutrons n is produced.(μ−, ν) reaction: μ−+X(Z,A)→Y((Z−1), A)+ν (1)(μ−, nν) reaction: Y((Z−1), (A))→n+Y((Z−1), (A−1)) (2)(μ−, 2nν) reaction: Y((Z−1), (A))→2n+Y((Z−1), (A−2)) (3)(μ−, 3nν) reaction: Y((Z−1), (A))→3n+Y((Z−1), (A−3)) (4)(μ−, 4nν) reaction: Y((Z−1), (A))→4n+Y((Z−1), (A−4)) (5) Reaction Formulae (1) to (5) as described above are symbolized as shown in FIG. 11, and are shown as 1 to 5. Multiple muon nuclear capture reactions are simultaneously produced at a predetermined rate depending on the element X. It has been found, as an experimental example, that for iodine I-127, the occurrence rates of the (μ−, ν) reaction, the (μ−, nν) reaction, the (μ−, 2nν) reaction, the (μ−, 3nν) reaction, the (μ−, 4nν) reaction, and the (μ−, 5nν) reaction are 8%, 52%, 18%, 14%, 5%, and 2.5%, respectively. (Muon Beam Generation Device) A muon beam for inducing the (μ−, xnν) reaction of the isotopes is obtained as follows. That is, a target such as carbon is irradiated with a proton beam with an energy of about 800 MeV, and in this manner, negative pion is generated. Then, this generated pion (a life of 2.6 nanoseconds) is decayed, and in this manner, a negative muon beam is obtained. FIG. 12 is the chart of nuclides for describing transition of the selenium isotopes (Se) by the muon nuclear capture reaction. For the Se isotopes, only Se-74, 76, 77, 78, 80, 82 as the stable nuclides and Se-79 (a half-life of 2.95×105 years) as the long-lived radionuclide remain in the course of storage for the certain period of time and the separation extraction step (FIG. 1; S11), and almost all of other isotopes are transmuted due to nuclear decay. In the case of focusing on Se-79, when such a Se isotopes is irradiated with the muon μ−, nuclear transmutation reactions 79Se(μ−, ν)79As, 79Se(μ−, nν)78As, 79Se(μ−, 2nν)77As, and 79Se(μ−, 3nν)76As are produced. As-76, As-77, As-78, and As-79 generated as described above are short-lived radionuclides. Thus, nuclear decay (β− decay) of these radionuclides is produced within a short period of time, and the radionuclides are transmuted into Se-76, Se-77, Se-78, and Se-79. That is, for Se-79 as the long-lived radionuclide, some of the nuclides transmuted by the muon nuclear capture reaction are transmuted back into Se-79, but the remaining nuclides are the Se stable nuclides. For Se-80, 82 of Se-74, 76, 77, 78, 80, 82, some of the nuclides transmuted by muon irradiation are also Se-79 as the long-lived radionuclide. As described above, in the case of irradiating the Se isotopes with the muon μ−, the transmuted nuclides are transmuted back due to β− decay. Thus, Se-79 cannot be transmuted by one-time irradiation, but can be decreased. For this reason, concentration of Se-77, 79 with an odd number of neutrons among the Se isotopes by way of the even-odd concentration step (FIG. 1; S12) will be discussed. Of the transmuted nuclides from Se-77 (the stable nuclide), As-77 is transmuted back into Se-77 by β− decay, As-76 is transmuted into Se-76 (the stable nuclide) by β− decay, As-75 is present as a stable nuclide, and As-74 is transmuted into Se-74 (the stable nuclide) by β− decay and Ge-74 (a stable nuclide) by β+ decay. Although transmutation of some of the transmuted As nuclides of Se-79 back into Se-79 cannot be avoided, Se-79 can be efficiently decreased by one-time muon irradiation. This is because the transmuted As nuclides of Se-77 are not transmuted back into Se-79. FIG. 13 is the chart of nuclides for describing transition of the palladium isotopes (Pd) by the muon nuclear capture reaction. For the Pd isotopes, only Pd-102, 104, 105, 106, 108, 110 as the stable nuclides and Pd-107 (a half-life of 6.5×106 years) as the long-lived radionuclide remain in the course of storage for the certain period of time and the separation extraction step (FIG. 1; S11), and almost all of other isotopes are transmuted due to nuclear decay. In the case of focusing on Pd-107, when such a Pd isotopes is irradiated with the muon μ−, nuclear transmutation reactions 107Pd(μ−, ν)107Rh, 107Pd(μ−, nν)106Rh, 107Pd(μ−, 2nν)105Rh, and 107Pd(μ−, 3nν)104Rh are produced. Rh-104, Rh-105, Rh-106, Rh-107 generated as described above are short-lived radionuclides. Thus, nuclear decay (β− decay) of these radionuclides is produced within a short period of time, and the radionuclides are transmuted into Pd-104, Pd-105, Pd-106, and Pd-107. That is, for Pd-107 as the long-lived radionuclide, some of the nuclides transmuted by the muon nuclear capture reaction are transmuted back into Pd-107, but the remaining nuclides are the Pd stable nuclides. For Pd-108, 110 of Pd-102, 104, 105, 106, 108, 110, some of the nuclides transmuted by muon irradiation are also Pd-107 as the long-lived radionuclide. As described above, in the case of irradiating the Pd isotopes with the muon μ−, the transmuted nuclides are transmuted back due to β− decay. Thus, Pd-107 cannot be transmuted by one-time irradiation, but can be decreased. For this reason, concentration of Pd-105, 107 with an odd number of neutrons among the Pd isotopes by way of the even-odd concentration step (FIG. 1; S12) will be discussed. Of the transmuted nuclides from Pd-105 (the stable nuclide), Rh-105 is transmuted back into Pd-105 by β− decay, Rh-104 is transmuted into Pd-104 (the stable nuclide) by β− decay and Ru-104 (a stable nuclide) by β+ decay, Rh-103 is present as a stable nuclide, and Rh-102 is transmuted into Pd-102 (the stable nuclide) by β− decay and Ru-102 (a stable nuclide) by β+ decay. Although transmutation of some of the transmuted Rh nuclides of Pd-107 back into Pd-107 cannot be avoided, Pd-107 can be efficiently decreased by one-time muon irradiation. This is because the transmuted Rh nuclides of Pd-105 are not transmuted back into Pd-107. FIG. 14 is the chart of nuclides for describing transition of the strontium isotopes (Sr) by the muon nuclear capture reaction. For the Sr isotopes, only Sr-84, 86, 87, 88 as the stable nuclides and Sr-90 (a half-life of 28.8 years) as the mid-lived radionuclide remain in the course of storage for the certain period of time and the separation extraction step (FIG. 1; S11), and almost all of other isotopes are transmuted due to nuclear decay. In the case of focusing on Sr-90, when such a Sr isotopes is irradiated with the muon μ−, nuclear transmutation reactions 90Sr(μ−, ν)90Rb, 90Sr(μ−, nν)89Rb, 90Sr(μ−, 2nν)88Rb, and 90Sr(μ−, 3nν)87Rb are produced. Rb-87 generated as described above is a metastable nuclide, and Rb-88, Rb-89, and Rb-90 generated as described above are short-lived radionuclides. Thus, nuclear decay (β− decay) of these nuclides is produced within a short period of time, and these nuclides are transmuted into Sr-88, Sr-89, and Sr-90. Sr-89 is further transmuted into Y-89 as a stable nuclide by β− decay. That is, for Sr-90 as the mid-lived radionuclide, some of the nuclides transmuted by the muon nuclear capture reaction are transmuted back into Sr-90, but the remaining nuclides are Sr stable nuclides, Y stable nuclides, or Rb metastable nuclides. The rest of Sr-84, 86, 87, 88 are also eventually transmuted into stable nuclides or metastable nuclides by muon irradiation. FIG. 15 is the chart of nuclides for describing transition of the zirconium isotopes (Zr) by the muon nuclear capture reaction. For the Zr isotopes, only Zr-90, 91, 92, 94, 96 as the stable nuclides and Zr-93 (a half-life of 1.5×106 years) as the long-lived radionuclide remain in the course of storage for the certain period of time and the separation extraction step (FIG. 1; S11), and almost all of other isotopes are transmuted due to nuclear decay. In the case of focusing on Zr-93, when such a Zr isotopes is irradiated with the muon μ−, nuclear transmutation reactions 93Zr(μ−, ν)93Y, 93Zr(μ−, nν)92Y, 93Zr(μ−, 2nν)91Y, and 93Zr(μ−, 3nν)90Y are produced. Y-90, Y-91, Y-92, and Y-93 generated as described above are short-lived radionuclides. Thus, nuclear decay (β− decay) of these radionuclides is produced within a short period of time, and these radionuclides are transmuted into Zr-90, Zr-91, Zr-92, and Zr-93. That is, for Zr-93 as the long-lived radionuclide, some of the nuclides transmuted by the muon nuclear capture reaction are transmuted back into Zr-93, but the remaining nuclides are Zr stable nuclides. For Zr-94, 96 of Zr-90, 91, 92, 94, 96, some of the nuclides transmuted by muon irradiation are also Zr-93 as the long-lived radionuclide. As described above, in the case of irradiating the Zr isotopes with the muon μ−, the transmuted nuclides are transmuted back due to β− decay. Thus, Zr-93 cannot be transmuted by one-time irradiation, but can be decreased. For this reason, concentration of Zr-91, 93 with an odd number of neutrons among the Zr isotopes by way of the even-odd concentration step (FIG. 1; S12) will be discussed. Of the transmuted nuclides from Zr-91 (the stable nuclide), Y-90, 91 are transmuted into Zr-90, 91 (the stable nuclides) by β− decay, Y-89 is present as the stable nuclide, and Y-88 is transmuted into Sr-88 (the stable nuclide) by β+ decay. Although transmutation of some of the transmuted Y nuclides of Zr-93 back into Zr-93 cannot be avoided, Zr-93 can be efficiently decreased by one-time muon irradiation. This is because the transmuted Y nuclides of Zr-91 are not transmuted back into Zr-93. FIG. 16 is the chart of nuclides for describing transition of the cesium isotopes (Cs) by the muon nuclear capture reaction. For the Cs isotopes, only Cs-133 as the stable nuclide, Cs-134 (a half-life of 2.07 years) as the mid-lived radionuclide, Cs-135 (a half-life of 2.3×106 years) as the long-lived radionuclide, and Cs-137 (a half-life of 30.07 years) as the mid-lived radionuclide remain in the course of storage for the certain period of time and the separation extraction step (FIG. 1; S11), and almost all of other isotopes are transmuted due to nuclear decay. In the case of focusing on Cs-137, when such a Cs isotopes is irradiated with the muon μ− nuclear transmutation reactions 137Cs(μ−, ν)137Xe, 137Cs(μ−, nν)136Xe, 137Cs(μ−, 2nν)135Xe, and 137Cs(μ−, 3nν)134Xe are produced. Moreover, in the case of focusing on Cs-135, nuclear transmutation reactions 135Cs(μ−, ν)135Xe, 135Cs(μ−, nν)134Xe, 135Cs(μ−, 2nν)133Xe, and 135Cs(μ−, 3nν)132Xe are produced. Xe-137 and Xe-135 generated as described above are short-lived radionuclides. Thus, nuclear decay (β− decay) of these radionuclides is produced within a short period of time, and these radionuclides are transmuted into Cs-137 and Cs-135. That is, for Cs-137, 135 as the long-lived radionuclides, some of the nuclides transmuted by the muon nuclear capture reaction are transmuted back into Cs-137, 135, but the remaining nuclides eventually become stable nuclides. FIG. 17 is the chart of nuclides for describing transition of the tin isotopes (Sn) by the muon nuclear capture reaction. For the Sn isotopes, only Sn-112, 114, 115, 116, 117, 118, 119, 120, 122, 124 as the stable nuclides and Sn-126 (a half-life of 1×105 years) as the long-lived radionuclide remain in the course of storage for the certain period of time and the separation extraction step (FIG. 1; S11), and almost all of other isotopes are transmuted due to nuclear decay In the case of focusing on Sn-126, when such a Sn isotopes is irradiated with the muon μ−, nuclear transmutation reactions 126Sn(μ−, ν)126In, 126Sn(μ−, nν)125In, 126Sn(μ−, 2nν)124In, and 126Sn(μ−, 3nν)123In are produced. In-123, 124, 125, 126 generated as described above are short-lived radionuclides. Thus, nuclear decay (β− decay) of these radionuclides is produced within a short period of time, and these radionuclides are transmuted into Sn-123, 124, 125, 126. That is, for Sn-126 as the long-lived radionuclide, some of the nuclides transmuted by the muon nuclear capture reaction are transmuted back into Sn-126, but the remaining nuclides eventually become stable nuclides. The rest of Sn-112, 114, 115, 116, 117, 118, 119, 120, 122, 124 also eventually become stable nuclides by muon irradiation. FIG. 18 is the chart of nuclides for describing transition of the samarium isotopes (Sm) by the muon nuclear capture reaction. For the Sm isotopes, only Sm-150, 152, 154 as the stable nuclides, Sm-147, 148, 149 as the metastable nuclides, Sm-146 (a half-life of 1×108 years) as a long-lived radionuclide, and Sm-151 (a half-life of 90 years) as the mid-lived radionuclide remain in the course of storage for the certain period of time and the separation extraction step (FIG. 1; S11), and almost all of other isotopes are transmuted due to nuclear decay. In the case of focusing on Sm-151, when such a Sm isotopes is irradiated with the muon μ−, nuclear transmutation reactions 151Sm(μ−, ν)151Pm, 151Sm(μ−, nν)150Pm, 151Sm(μ−, 2nν)149Pm, and 151Sm(μ−, 3nν)148Pm are produced. Pm-148, 149, 150, 151 generated as described above are short-lived radionuclides. Thus, nuclear decay (β− decay) of these radionuclides is produced within a short period of time, and these radionuclides are transmuted into Sm-148, 149, 150, 151. That is, for Sm-151 as the long-lived radionuclide, some of the nuclides transmuted by the muon nuclear capture reaction are transmuted back into Sm-151, but the remaining nuclides eventually become stable nuclides. For Sm-150, 152 of Sm-146, 147, 148, 149, 150, 152, 154, some of the nuclides transmuted by muon irradiation are also Sm-151 as the mid-lived radionuclide. As described above, in the case of irradiating the Sm isotopes with the muon μ−, the transmuted nuclides are transmuted back due to β− decay. Thus, Sm-151 cannot be transmuted by one-time irradiation, but can be decreased. For this reason, concentration of Sm-151, 149, 147 with an odd number of neutrons among the Sm isotopes by way of the even-odd concentration step (FIG. 1; S12) will be discussed. Although transmutation of some of the transmuted Pm nuclides of Sm-151 back into Sm-151 cannot be avoided, Sm-151 can be efficiently decreased by one-time muon irradiation. This is because the transmuted Pm nuclides of Sm-149 are not transmuted back into Sm-151. Moreover, the transmuted nuclide Pm-147 of Sm-147 (the metastable nuclide) is transmuted back into Sm-147 by β− decay, and other transmuted nuclides Pm-144, 145, 146 are transmuted into Nd stable nuclides or metastable nuclides by β+ decay. According to the method for processing the radioactive waste according to at least one embodiment described above, the separated and extracted isotopes is irradiated with the high-energy particles, and in this manner, only the radionuclides can be selectively transmuted into the stable nuclides in the fission products. According to such a radioactive waste processing method, isotope separation is not necessary, and the stable nuclides transmuted from the long-lived radionuclides or the like can be reutilized as a resource. Some embodiments of the present invention have been described. However, these embodiments have been set forth merely as examples, and are not intended to limit the scope of the invention. These embodiments can be implemented in other various forms, and various omissions, replacements, changes, and combinations can be made without departing from the gist of the invention. These embodiments and variations thereof are included in the scope and gist of the invention, as well as being included in the invention described in the claims and an equivalent scope thereof.
	description	This invention relates to the field of packages for the storage of irradiated fuel, comprising packaging as well as a canister which provides confinement of the irradiated fuel and which is housed in the cavity defined by the packaging. The packaging of an irradiated fuel storage package is generally intended to be placed vertically during storage. Nevertheless, prior to storage, loading of the confinement canister into the cavity of the packaging may be achieved with the latter placed horizontally. In order to facilitate introduction of the canister, internally the packaging may be equipped with rails for guiding the canister, upon which this canister rests when it is slid into the cavity. Once this operation has been carried out the housing cavity of the canister is closed off by a cover (or the removable end) of the packaging, then the package is tipped through 90° to adopt its vertical storage position. In order to be able to meet regulatory storage requirements, the package must, notably, meet the requirements of the so-called “aircraft crash” test. This test may be simulated by a very high intensity impact taking place externally on the lateral body of the packaging. It is then necessary to demonstrate that the canister which provides confinement of the irradiated fuel remains sealed after this impact. It has been shown that the presence of guide rails was a significant source of risk of breaching of the leak-tightness of the canister, especially when the impact is located on the part of the packaging which bears these rails. In order to resolve this problem, the packaging can be strengthened even further and/or it can be protected by additional shock absorbing means placed externally around the lateral body of said packaging. Nevertheless, these measures may prove to be insufficient to meet the requirements of the aircraft crash test, and furthermore result in extremely high overall mass and volume which are not compatible with operational constraints. It is noted that this problem in terms of the guide rails may also be encountered during an earthquake, during which repeated impacts may lead to damage being caused to the confinement canister, until this leads to a rupture in the leak tightness. Furthermore, this problem is not associated solely with guide rails for introducing the canister horizontally into the cavity of the packaging, but may also occur with any assembly forming guide rails provided for introducing the canister vertically into this same cavity. The purpose of the invention is therefore to at least partially provide a solution to the disadvantages mentioned above, compared with the embodiments of the prior art. In order to do this the object of the invention is a package comprising packaging as well as a confinement canister for irradiated fuel, the packaging comprising a lateral body which extends around a longitudinal axis of the packaging and which bears an internal surface which delimits a housing cavity wherein the canister is placed, packaging furthermore comprising at least one assembly forming a guide rail for the canister in the cavity, the assembly being mounted on the lateral body and protruding at least partly into the housing cavity from said internal surface of the lateral body. According to the invention, said assembly forming a guide rail includes an impact shock absorbing element designed to absorb, by plastic deformation, a lateral impact between the packaging and the confinement canister. Thus, despite the protruding position of the assembly forming a guide rail in the cavity, the risk of damage to the confinement canister are limited by the shock absorbing element, which makes up all or part of the assembly forming the guide rail. In effect, following an external impact on the lateral body which causes it to be displaced and/or deformed, or, in the case of an earthquake, the forces transmitted to the canister are in part absorbed/filtered by the plastic crushing of the shock absorbing element between said canister and the lateral body. Thus the invention provides a particularly clever solution to the problems of meeting the requirements of the aircraft crash test, and to compliance with the regulatory criteria relating to the confinement of irradiated fuel. In other terms, the impact shock absorbing element is designed to form a zone which preferentially undergoes plastic deformation in preference to the canister during the impact of the assembly forming the guide rail against said canister. An assembly forming a guide rail is to be taken to mean any assembly protruding inside the cavity and which allows the canister to be guided during its introduction into the cavity, whether this introduction is carried out with the packaging placed vertically or horizontally. In this last case the assemblies concerned are those upon which the canister rests during the introduction, but also the assemblies which may simply be in contact with the canister during this operation. In the case of loading vertically, it means all the assemblies protruding into the cavity used to guide/centre the canister during the vertical introduction. It should all the same be noted that irrespective of the orientation of the packaging for loading, during storage in the vertical position there is not necessarily any contact between the canister and the assemblies forming the guide rails, with gaps in effect appearing/remaining. It is emphasised that the presence of said gaps amplify the force transmitted to the canister by the wall of the packaging and/or by the assembly forming the guide rail. Thus, the larger the aforementioned gap, the more consequential the force transmitted in the event of an external impact on the lateral body. Preferably said assembly forming the guide rail extends along the direction of the longitudinal axis over a length corresponding to at least 70% of the height of the housing cavity along this same direction. Yet more preferentially, the length of this assembly is substantially equal to the height of aforementioned cavity. Preferably, the assembly forming the guide rail is parallel to the longitudinal axis. Preferably, the package comprises multiple assemblies forming guide rails spaced circumferentially apart from each other on the interior surface of the packaging body. Preferably, the impact shock absorbing element is made of aluminium or of one of its alloys. Preferably, the assembly forming the guide rail is arranged in part in a housing formed in the lateral body. Preferentially, in a plane of a transverse section of the assembly forming the guide rail, the ratio between the surface area of the part of this assembly located in the housing and the surface area of this housing is less than 0.9. Alternatively, the assembly may be fixed so that it is entirely protruding from this body, without being partially housed in a housing or similar of the lateral body. Preferably, the shock absorbing element is arranged so that it is free to move in translation along the longitudinal direction of the assembly forming the rail, in relation to the lateral body. Alternatively it may be fixed at one of its ends to the body, in order to be able to undergo thermal expansion relative to this body without stress. Nevertheless, as stated above, the shock absorbing element is preferably not fixed to the lateral body at all. Preferably, the assembly forming the guide rail comprises a radially internal portion forming a rail, as well as the shock absorbing element arranged between the rail and the packaging lateral body. In particular the rail protects the shock absorbing element during the introduction of the canister, notably against the risk of tearing of material. In addition, by providing adequate rigidity, the rail can spread the forces over a larger surface area of the shock absorbing element with which it is in contact. The effectiveness of the shock absorbing function provided by the assembly is thus enhanced. Preferably the rail is provided with a low-friction coating. Preferably the rails and the impact shock absorbing element are connected to each other by a link made of complementary shaped parts. It may, for example, be a dovetail link, a square or rectangular section link or again a simple flat support face. Irrespective of the shape used for this link, it is preferably made such that a relative longitudinal movement can take place between the rail and the shock absorbing element, with an amplitude which may be limited, but which in particular allows for any differential thermal expansion between these two elements. This is naturally advantageous when the coefficients of thermal expansion are substantially different. Finally, the rail is preferably firmly fixed to the lateral body at one of its ends and the same rail is arranged so that it is free to move in translation along the longitudinal direction of the rail, relative to the shock absorbing element, up to its other end. Preferably said end of the raid firmly fixed to the lateral body is located close to the opening of the cavity through which the canister is introduced. As an indication, in a preferred embodiment the opening of the cavity concerned is located at the lower end of the packaging, the latter being equipped with a removable end designed to free the opening of the cavity. This not only allows the problem of any differential expansion between these two elements to be managed, but also limits the risk of the rail buckling during the canister introduction phase. In effect, during this introduction the rail may deform freely along its longitudinal direction in the direction of said other end of the rail, relative to the shock absorbing element which supports it, without the risk of buckling. Preferably the canister encloses irradiated fuel rods, preferably grouped together within one or more nuclear fuel assemblies. Preferably, in any transverse section plane through the packaging and the canister, the ratio of the surface area of the canister delimited by its external surface and the surface of the cavity delimited by its internal surface is greater than 0.8. Other advantages and characteristics of the invention will appear in the detailed non-restrictive description below. With reference firstly to FIGS. 1 and 2, a package 100 for storage of radioactive materials taking the form of a preferred embodiment of the present invention is shown. The package is intended to hold irradiated fuel. It includes packaging 1 which receives a confinement canister 3 containing the nuclear fuel. Preferably this involves irradiated fuel rods, preferably grouped together within one or more nuclear fuel assemblies. Packaging 1 includes overall a hollow lateral body 2 of cylindrical form and which defines a cavity 4 for receiving the canister 3, a detachable head cover 6 closing cavity 4 at one upper end 2a of body 2, together with a packaging base 8 closing cavity 4 at the other end of lateral body 2, called lower end 2b. The base may be made in one piece with the lateral body. In a manner known to those skilled in the art, the canister 3 fills a very large portion of the cavity 4. Usually this is expressed by the fact that in any transverse section plane through the packaging 1 and the canister 3, as in that of FIG. 3, the ratio of the surface area of the canister 3 delimited by its external surface and the surface area of the cavity 4 delimited by its internal surface 22 is greater than 0.8. As is known to those skilled in the art, in such packaging for storage, preferably long-term storage, the cavity does not constitute a confinement enclosure for radioactive materials, this enclosure being effectively defined by the canister itself. Nevertheless, the design of this packaging provides the usual neutron protection, gamma radiation protection and mechanical strength functions. To achieve this, it may be envisaged in particular that the thickness of hollow lateral body 2 is at least 200 mm, and it can be made of steel. The lateral body 2 extends around the longitudinal axis 12 of the packaging, on which the opening of the cavity located on the opposite side from the base 8 is centred. The packaging 1 also comprises multiple handling devices 14, also called lifting trunnions, intended to fit onto a lifting beam (not represented) in order to enable the package to be moved/tipped. There are preferably four or more such devices, distributed near the upper and lower ends of lateral body 2, from which they project radially towards the outside. In addition, packaging 1 comprises means of ventilation which allow air to circulate by convection between the cavity 4 and the outside of the packaging when the latter is in the vertical position. These specific means, providing an air flow which enables a portion of the heat released by the radioactive materials contained in the container to be collected and dissipated, can be produced by any means known to those skilled in the art. As an indication, through-passages 17 may be made at the upper and lower ends of the packaging, so that the exterior of the latter is linked to the cavity 4. These through-passages 17 may, for example, be made on the top 2a and bottom 2b ends of the body 2, as shown in FIGS. 1 and 2. Thus, as schematically shown by the arrows in those same figures, the external air passes through the packaging body 2 via the through-passages 17 of the bottom end 2b, then to enter within an annular free space between the canister 3 and the internal wall of the cavity 4, to then be extracted through analogous passages 17 provided at the top end of the body 2. FIG. 4, in which the cover 6 has been removed for the purposes of clarity, shows that the interior surface 22 of the lateral body 2 which delimits the cavity 4 is equipped with means to help the canister slide relative to the lateral body 2 when it is being loaded into the cavity 4. As an indication, it should be noted that the introduction can alternatively be carried out from a removable base of the packaging, without going beyond the scope of the invention. The means for helping the canister to slide are specific to this invention and will be described in detail whilst making reference to the following figures. First of all with reference more specifically to FIGS. 3 to 6, it is shown that the packaging includes two assemblies 15 forming guide rails for the canister in order to introduce it into the cavity 4. These two assemblies 15 are spaced apart from each other circumferentially, for example by an angle of between 5 and 30° centred on the axis 12. These assemblies, with a long extended shape, extend parallel to said axis 12. Each of them is partly housed in a recess 20 in the lateral body, and protrude from this latter to the interior of the cavity 4, that is to say, they extend radially towards the interior beyond the surface 22 of the lateral body 2 which delimits the cavity 4. The recess 20 is a substantially parallelepiped-shaped housing extending parallel to the axis 12, over substantially the entire length of the cavity. The two assemblies 15 concerned are those located lowest down when the packaging 1 rests horizontally, in the position for loading the canister 3. They are preferably arranged symmetrically in relation to a vertical median plane which includes the axis 12. The preferred embodiment shown, each assembly 15 comprises a radially internal part 24 forming a rail, made of steel. A low-friction coating 26 may be applied, for example made of hard stainless steel. Naturally the purpose of this coating is to promote the sliding of the canister on the assemblies 15 when it is being introduced into the cavity, preferably carried out with the packaging horizontal as shown schematically in FIGS. 2 and 3. Each assembly also includes a shock absorbing element 28, preferably made of aluminium or of one of its alloys. This element 28 is housed at least in part in the recess 20, being arranged between the lateral body 2 and the rail 24, as can be better seen in FIG. 5. This impact shock absorbing element 28 is designed to absorb, by plastic deformation, a lateral impact between the body 2 and the confinement canister 3. Thus although the assemblies 15 protrude into the cavity 4 in order to fulfil their first function of guiding the canister during its introduction into the packaging, the risks of damage to this confinement canister are limited by the impact shock absorbing element 28 which can undergo plastic deformation. The impact shock absorbing element 28 extends inside of the recess 20 in the form of a continuous bar over the entire length of the assembly 15. Alternatively, there may be several lengths of shock absorber arranged end to end along the longitudinal direction of the rail 24, which is preferentially continuous along its entire length, namely over the entire length of the assembly 15. In this regard, it should be noted that each assembly extends over a very large portion of the packaging. As can be seen in FIG. 5, each assembly 15 extends along the direction of the longitudinal axis 12 over a length “L” which corresponds to at least 70% of the height “H” of the cavity 4, with it being specified nevertheless that a percentage of up to 90% or more may be envisaged. Each assembly 15 is assembled onto the lateral body 2 using two support spacers 30 each placed, respectively, at the ends of the recess 20. The spacers 30 are preferably welded to the lateral body 2, as the U-welds 34 show in FIGS. 6a and 6b. In addition the ends of the rail 24 and the spacers 30 are linked two by two by a connection using complementary shaped parts 46, here a dovetail connection. As shown in FIG. 5, the shock absorbing element 28 is arranged with an axial gap between the head spacer 30 and the bottom spacer 30, so as to be able to expand freely in the longitudinal direction of the assembly 15 relative to the body 2 and to the rail 24. In other terms, the shock absorbing element 28 is simply wedged axially, with a gap, and maintained radially by being clasped between the base of the recess 20 and the rail 24. With reference to FIG. 6, it is shown that the rail 24 and the impact shock absorbing element 28 are connected to each other by a connection using complementary shaped parts 37, here a dovetail connection. The connection 37 is located slightly more towards the interior that the limitation surface 22 of the cavity 4. Thus a very large portion of the shock absorbing element 28 is located in the recess 20, and more precisely, almost all of it, except for its internal end in the form of a dovetail, male or female. With this connection 37 relative longitudinal movement can occur between the rail 24 and the shock absorbing element 28, with an amplitude which is limited but which allows for the phenomenon of differential expansion between these two elements 24, 28. Returning to FIG. 6a, it should be noted that the rail 24 is firmly fixed to the support spacer 30 located at the side where the canister is introduced. In the embodiment that is described this is therefore the spacer located on the cover side. Fixing is achieved for example by a weld 38 along the dovetail interface. On the other hand, over the entire remaining length of the rail 24 from this end of the rail located close to the cover of the packaging, the rail is arranged so that it is free to move in translation along the longitudinal direction relative to the shock absorbing element 28. This is also the case with the other spacer 30, as can be seen in FIG. 6b which shows the connection 36 which offers a degree of freedom of translation between the rail 24 and said spacer 30. Consequently the rail 24 is free to move in translation relative to the shock absorber 28 up to its other end, which in addition allows the problem of differential thermal expansion between these two elements to be managed, limiting the risk of buckling of the rail 24 during canister loading operations. In effect, during this introduction the rail can extend freely in the direction of the base, relative to the shock absorbing element 28 and to the spacer 30 located at the opposite end of the cavity intended for the introduction of the canister. FIGS. 5 and 7 show that a centring spacer 40 is attached to the front of the head end of the rail 24, superimposed on the support spacer 30 to which it is preferably assembled by a weld 42 placed at the front interface between these two spacers 30, 40. Another weld is also envisaged at the interface between the head end of the rail 24 and this centring spacer 40 which, due to its inclined surface, allows the canister 3 to self-centre during the initial canister loading phase. The spacer 40 is preferentially wholly located within the cavity 4, that is, radially offset towards the interior relative to the surface 22. FIG. 8 shows a schematic view of the behaviour of the assembly 15 in the event of an impact taking place to the lateral body 2 of the packaging, simulating, for example, an aircraft crashing onto the package. Analogous behaviour may also occur in the event of an earthquake causing repeated high intensity shocks. Following an external impact 50 on the lateral body 2 causing it to be displaced and/or deformed, the forces transmitted to the canister are in part absorbed/filtered by the plastic crushing of the shock absorbing element 28 between the canister 3 and the base of the recess 20 of the lateral body 2. In other terms, in the event of an external impact whose intensity is greater than a determined value, the shock absorbing element 28 forms a zone which preferentially undergoes plastic deformation, between the canister 3 and the body 2. In order to favour the crushing of the assembly 15 forming a guide rail, the latter is fitted in its housing 20 with a lateral gap. Such lateral gaps 31 are schematically represented in the transverse section in FIG. 8a. In effect they allow the portion 15a of the assembly 15 located in the housing 20 to be acceptably crushed without being hindered by the lateral walls of the housing. During a fall, the crushing of the part 15a, which is preferentially made up entirely of the shock absorbing element 28, leads to a lateral expansion of the assembly 15 and therefore to the lateral gaps 31 being taken up. As an indication, the sum of these gaps may be greater than 1 or 2 mm. Alternatively, a single gap may be provided instead of two without going beyond the scope of the invention. Whatever the case, it is envisaged that in a plane of a transverse section of the assembly 15, as shown in FIG. 8a, the ratio between the surface area of the portion 15a located in the housing 20 and the surface area of this housing is less than 0.9. This ratio is observed over at least 70% of the length of the assembly 15, but is obviously not achieved at the spacers 30 which entirely fill the housing 20. With reference to FIG. 9, another possible embodiment of the assembly 15 is shown. Firstly the assembly is made in one piece. It thus forms in its entirety a shock absorbing element made to carry out the rail function although the low-friction coating 26 may be retained at its interior end. Furthermore, the assembly 15 protrudes entirely from the interior surface 22 which delimits the cavity 4, and is no longer partially inserted in a recess in the lateral body 2 of the packaging. With reference now to FIGS. 10 to 12, another possible embodiment of the assemblies 15 forming the guide rails is shown. This preferably is a design used for assemblies other than the two bottom assemblies 15 shown in FIGS. 3 and 4 and described above. These other assemblies, arranged all around the cavity 4, have references 15′ in said FIGS. 3 and 4. In what follows they will nevertheless be described under reference 15 for the description of FIGS. 10 to 12. Each assembly 15 is also made from a single piece which in its entirety forms the shock absorbing element. It is free to move in translation relative to the body 2 along the longitudinal direction of the rail. It is also placed in a housing 20 of this body 2, being simply supported on the body at its ends by two fixing straps 30a. In order to this, the straps 30a are preferably welded to the body 2 and have a support foot 51 holding the assembly 15 against the base of the housing 20. For thermal expansion of the assembly 15, axial gaps are made between the latter and the straps 30a also arranged in the housing 20 of the packaging body 2. The foot 51 of the fixing straps 30a is applied between two longitudinal external protruding parts 52 of the assembly 15, these protruding parts 52 each leading along the longitudinal direction of the rail. Naturally various modifications may be made to the invention, which has just been described as non-restrictive examples only, by those skilled in the art.
041707370	claims	1. A top-entry transmission electron microscope comprising: a stage, a removable cartridge housed in said stage, a specimen holder mounted in said removable cartridge, a magnetic lens, in the field of which is located said specimen holder mounted so that it can be tilted about the axis x perpendicular to the microscope's optical axis, an electric drive for said holder mechanically coupled with the latter, an actuating step motor of said electric drive mounted on said stage, a rotor of said actuating step motor having the axle coincident with said axis x and mechanically coupled with said specimen holder for the synchronous turning of said rotor and holder, a piezoelectrically actuated electromechanical means for turning said rotor, mechanically coupled with the latter, a drive-transmitting member of said step motor secured on said rotor-turning electromechanical means, a pivot secured in said removable cartridge, a rocker designed to convey drive to said rotor, geared to said drive transmitting member and secured on said pivot so that it can be displaced translationally with respect to said pivot, a piezoelectrically actuated electromechanical means for positioning said rocker, interacting with said drive transmitting member, a control voltage shaper for said step motor having an analogue output joined to said rotor-turning electromechanical means and a count input, a code-to-voltage converter for said control voltage shaper having an output serving as said analogue output for said control voltage shaper and an input, a Johnson code distributor for said input of said control voltage converter having an output joined to said input of said code-to-voltage converter, a unit for setting the magnitude and sense of holder displacement having an output for clock pulses and joined to said count input of said control voltage shaper, a control unit of said unit for setting the magnitude and sense of holder displacement having inputs, meant for receiving the signals of "start," "stop," "reset," "clock pulse frequency," "sense of displacement," "magnitude of displacement," and an output, a synchronization unit having an input joined to said output of said control unit, an output for clock pulses joined to said control voltage shaper, and a control output joined to said rocker-positioning electromechanical means. a mechanism for bringing the specimen into coincidence with the tilt axis x, a bearing pulley of said coincidence mechanism mounted on said rotor so that it can be rotated about the tilt axis x, a means for braking said bearing pulley with respect to the body of said removable cartridge having an electrical input, a crank-link mechanism of said coincidence mechanism whose crank is mounted on said bearing pulley whereas its link pin is secured in said rotor perpendicularly to the tilt axis x and lies in the specimen plane, a sent for housing said specimen provided in the body of said link of said crank-link mechanism, a switch having an input joined to said control output of said synchronization unit, a first output joined to said rocker-positioning electromechanical means, and a second output joined to said electrical input of said bearing pulley braking means. a gear rim provided on said rotor, a tooth provided at the end of said rocker engageable with said rotor and having a profile complementary to the tooth space profiles of said gear rim. an elastic cantilever element, serving as said pivot, bearing said rocker of said step motor, with one end being rigidly fixed in said removable cartridge body and the other bearing said rocker rigidly secured on this free end of said cantilever element. a mechanism for translating said link in the specimen plane, a second bearing pulley with a crank of said link translating mechanism mounted on said rotor so that it can be rotated about the tilt axis x, a means for braking said second bearing pulley with respect to said removable cartridge having an electrical input, a slot provided in the body of said link of said crank-link mechanism perpendicular to its pin axis to house said crank of said second bearing pulley, a second output of said switch connected with said electrical input of said braking means of said second bearing pulley. a braking rocker designed to interact with said bearing pulley, a pivot secured to said removable cartridge bearing said braking rocker, electromechanical means mounted on said stage and designed to interact with said braking rocker during braking. a second braking rocker designed to interact with said second bearing pulley, a pivot secured in said removable cartridge bearing said second braking rocker, a second electromechanical means mounted on said stage and designed to interact with said second braking rocker during braking. a stage, a removable cartridge housed in said stage, a specimen holder mounted in said removable cartridge, a magnetic lens, in the field of which is located said specimen holder mounted so that it can be tilted about the axis x perpendicular to the microscope's optical axis, an electric drive for said holder mechanically coupled with the latter and having an actuating step motor mounted on said stage, a rotor of said actuating step motor having the axle coincident with said axis x and mechanically coupled with said specimen holder for the synchronous turning of said rotor and said specimen holder, a piezoelectrically actuated electromechanical means for turning said rotor mechanically coupled with said rotor, a drive-transmitting member of said step motor secured on said rotor-turning electromechanical means, a pivot secured in said removable cartridge, a rocker designed to convey drive to said rotor geared to said drive transmitting member and secured on said pivot so that it can move lengthwise with respect to this pivot, a piezoelectrically actuated electromechanical means for positioning said rocker and interacting with said drive-transmitting member, a control voltage shaper having an analogue output joined to said rotor-turning electromechanical means and a count input, a code-to-voltage converter of said control voltage shaper having an output, serving as said analogue output for said control voltage shaper, and an input, a Johnson code distributor of said control voltage shaper having an output joined to said input of said code-to-voltage converter, a unit for setting the magnitude and sense of holder displacement having a clock pulse output joined to said count input of control voltage shaper, a control unit for said unit for setting the magnitude and sense of holder displacement having inputs, meant for receiving the signals of "start," "stop, " "reset," "clock pulse frequency," "sense of displacement," "magnitude of displacement," and an ouput, a synchronization unit having an input, joined to said output of said control unit, an output of clock pulses, joined to said control voltage shaper, and a control output, joined to said rocker-positioning electromechanical means, a clock pulse generator of said control unit having an input, serving as said "clock pulse frequency" input of said unit for setting the magnitude and sense of holder displacement, and an output, a flip-flop of said control unit having an S-input, serving as a "start" input for said unit for setting the magnitude and sense of holder displacement, an R-input and a Q-input, a second flip-flop of said control unit having an S-input, connected to said S-input of said first flip-flop, an R-input, joined to said R-input of said first flip-flop, a P-output and a count (complementary) input, a logical OR circuit of said control unit having a first and a second input, serving as "stop" and "reset" inputs of said unit for setting the magnitude and sense of holder displacement, an output joined to said P-inputs of said flip-flops and a third input, a coincidence circuit for the codes of set and current values of rotor displacement of said control unit having an input, serving as the "magnitude of displacement" input of said unit for setting the magnitude and sense of holder displacement, an output joined to said third input of said logical OR circuit, and a comparison input, a bidirectional counter of said control unit having an output joined to said comparison input of said coincidence circuit, an input serving as said count input of said control unit, a synchronization input joined to said second input of said logical OR circuit, and a control input, a switch of said control unit having an input, serving as the "sense of displacement" input of said unit for setting the magnitude and sense of holder displacement and joined to said control input of said bidirectional counter, also having a second, a third input, and an output. a first logical AND circuit of said synchronization unit having a first input, joined to said output of said clock pulse generator and to said Q-output of said first flip-flop, an output serving as said clock pulse output of said synchronization unit, and a second input, a one-shot multivibrator of said synchronization unit having an inverted output, joined to said second input of said first logical AND circuit, and an input joined to said P-output of said second flip-flop, a second logical AND circuit of said synchronization unit having a first input, joined to said P-output of said second flip-flop, a second input joined to said Q-output of said first flip-flop, a third input joined to said output of said switch of said control unit, and an output serving as the control output of said unit for setting the magnitude and sense of holder displacement, a third logical AND circuit of said synchronization unit having an input, joined to said output of said switch of said control unit, and an output joined to said complementary input of said second flip-flop, a fourth logical AND circuit of said synchronization unit having an input, joined to said output of said first logical AND circuit, a second input joined to said output of said second logical AND circuit, and an output joined to said count input of said bidirectional counter. an n-digit Mobius ring counter of said Johnson code distributor having n inputs in accordance with the number of digits, a count input joined to said clock pulse output of said synchronization unit, a "reset" input joined to said "reset" input of said unit for setting the magnitude and sense of holder displacement, Q- and P-outputs of the least significant digit and Q- and P-outputs of the most significant digit, a logical 2AND-to-2OR circuit of said distributor having a first input, joined to said Q-output of the l.s.d. of said Mobius ring counter, a second input joined to said P-output of the m.s.d. of said Mobius ring counter, a third input joined to said P-output of the l.s.d. of said Mobius ring counter, and a fourth input joined to said Q-output of the m.s.d. of said Mobius ring counter, an output of said third input of said fourth logical AND circuit of said synchronization unit, at least one redundant digit of said Mobius ring counter having an output, joined to said l.s.d., and an input joined to said m.s.d. of said Mobius ring counter, also having P- and Q-outputs joined to said second and third inputs of said switch of said control unit. a non-linear Johnson-code-to-voltage converter of said code-to-voltage converter having n inputs joined to said n outputs of said Mobius ring counter, and an output joined to said electromechanical means of said step motor, a linear Johnson-code-to-voltage converter of said code-to-voltage converter having n inputs, joined to said n outputs of said Mobius ring counter, and an output, a comparator of said code-to-voltage converter having an input, joined to said output of said linear Johnson-code-to-voltage converter, an output joined to said input of said third logical AND circuit of said synchronization unit, and a second input, a gate of said code-to-voltage converter having a control input, joined to said output of said logical OR circuit of said control unit, a second input joined to said output of said linear converter, and an output, an analogue storage of said converter having an input, joined to said output of said gate, and an output joined to said second input of said converter. 2. A top-entry transmission electron microscope, as claimed in claim 1, comprising: 3. A top-entry transmission electron microscope, as claimed in claim 1, comprising: 4. A top-entry transmission electron microscope, as claimed in claim 1, comprising: 5. A top-entry transmission electron microscope, as claimed in claim 1, comprising a friction increasing means provided on the end of said rocker of step motor to interact with said drive transmitting member. 6. A top-entry transmission electron microscope, as claimed in claim 2, comprising: 7. A top-entry transmission electron microscope, as claimed in claim 2, comprising: 8. A top-entry transmission electron microscope, as claimed in claim 6, comprising: 9. A top-entry transmission electron microscope, as claimed in claim 7, comprising a friction increasing means provided on the end of said braking rocker to interact with said electromechanical means. 10. A top-entry transmission electron microscope, as claimed in claim 7, whose said first electromechanical means is piezoelectrically actuated. 11. A top-entry transmission electron microscope, as claimed in claim 8, comprising a friction increasing means provided on said second braking rocker to interact with said second electromechanical means. 12. A top-entry transmission electron microscope, as claimed in claim 8, whose said second electromechanical means is piezoelectrically actuated. 13. A top-entry transmission electron microscope comprising: 14. A top-entry transmission electron microscope, as claimed in claim 13, comprising 15. A top-entry transmission electron microscope, as claimed in claim 14, comprising-- 16. A top-entry transmission electron microscope, as claimed in claim 15, comprising
	abstract	A group management apparatus manages, as a plurality of groups, numerous installation devices installed in a plurality of buildings. The group management apparatus includes an acquiring component, a summarizing component and a screen generating component. The Acquiring component acquires operating data of the numerous installation devices via controllers. The controllers are placed in the buildings and control the numerous installation devices inside the buildings. The summarizing component summarizes, per group, operating data values that are values represented by the operating data. The screen generating component generates a screen in which results, with respect to the plurality of groups, of the operating data values having been summarized by the summarizing component are juxtaposed.
	claims	1. A debris filter for use in a nuclear fuel assembly comprising a bundle of fuel rods to be supplied with a coolant fluid flow, the filter comprising:a plurality of walls defining a plurality of flow ducts extending in a longitudinal direction, each duct being delimited between a pair of the walls; anddeflectors protruding into each duct alternately from the corresponding pair of walls and overlapping in the longitudinal direction to define a zigzag shaped flow channel in each duct, the overlapping deflectors in each duct being provided with a set of holes aligned in the longitudinal direction to define through the overlapping deflectors a passage for accommodating a lower end pin of one of the fuel rods. 2. The debris filter according to claim 1, further comprising each duct in register in the longitudinal direction with each passage, one cell for accommodating a bottom end cap of a fuel rod. 3. The debris filter according to claim 2, wherein each cell comprises at least one spring for at least one of transversely and longitudinally supporting the bottom end cap accommodated in the cell. 4. The debris filter according to claim 1, wherein the walls are each made up of at least one metallic sheet provided with at least one deflector fold for forming one deflector. 5. The debris filter according to claim 4, further comprising intermediate walls separating two adjacent ducts and each intermediate wall being made up of two metallic sheets provided with deflector folds protruding on opposite faces of the intermediate wall. 6. The debris filter according to claim 5, wherein each intermediate wall is provided with one deflector fold protruding from one of the opposed faces of the intermediate wall at a level intermediate to two deflector folds protruding from the other one of the opposed faces of the intermediate wall. 7. The debris filter according to claim 1, wherein the deflectors are plates secured to the walls at an angle. 8. The debris filter according to claim 7, comprising intermediate walls separating two adjacent ducts each provided with at least one deflector plate interlocked with the intermediate wall to form two deflectors each protruding on a respective face of the wall. 9. The debris filter according to claim 8, comprising at least one pair of adjacent intermediate walls provided with deflector plates intersecting the corresponding intermediate walls at the same level. 10. The debris filter according to claim 1, further comprising connection strips interlocked perpendicularly with the walls. 11. Nuclear fuel assembly comprising a bundle of fuel rods extending in a longitudinal direction and each fuel rod comprising a pin at a lower end and a debris filter according to claim 1, the pin of each fuel rod being accommodated in one passage. 12. The nuclear fuel assembly according to claim 11, further comprising a grid-shaped support plate disposed below the debris filter, the support plate comprising bars defining between them openings, the bars being arranged for supporting the fuel rods extending through the passages and the openings being arranged to allow coolant flow though the support plate into channels of the filter.
	abstract	A method including, in one embodiment, severing a sample at least partially from a substrate by cutting the substrate with a focused ion beam (FIB), capturing the substrate sample by activating a grasping element, and separating the captured sample from the substrate. The captured sample may be separated from the substrate and transported to an electron microscope for examination.
	claims	1. A scanning type charged particle beam microscope comprising:a charged particle imaging unit having a charged particle beam irradiation unit to irradiate a focused charged particle beam to a surface of a sample formed with a pattern and to scan it over the surface, anda secondary charged particle imaging unit to detect secondary charged particles emitted from the sample as the charged particle beam irradiation unit irradiates and scans the charged particle beam over the sample and to generate a secondary charged particle image of the sample surface;an image quality improving unit to process the secondary charged particle image of the sample surface generated by the charged particle imaging unit; andan output unit to output a result of processing by the image quality improving unit;wherein the image quality improving unit aligns the position of the design data of the pattern formed on the sample with the position of the secondary charged particle image of the sample surface generated by the charged particle imaging unit and then improves a quality of the secondary charged particle image of the sample surface by using the design data of the pattern formed on the sample;wherein a way of improving the quality of the secondary charged particle image of the sample surface differs according to the design data. 2. A scanning type charged particle beam microscope according to claim 1, wherein the charged particle imaging unit is a scanning electron microscope (SEM) and the image quality improving unit improves a quality of a SEM image of the sample imaged by the scanning electron microscope (SEM). 3. A scanning type charged particle beam microscope according to claim 1, further comprising:an image processing unit to process the image whose quality has been improved by the image quality improving unit, and to perform a detection of defects of the sample, a production of an image of defects or a measuring of dimensions of the pattern. 4. A scanning type charged particle beam microscope according to claim 1, wherein the image quality improving unit aligns the position of the design data of the pattern formed on the sample with the position of the secondary charged particle image of the sample surface generated by the charged particle imaging unit and then corrects pattern geometry information of the design data and improves a quality of the secondary charged particle image by using the design data whose geometry information has been corrected. 5. A scanning type charged particle beam microscope according to claim 1, wherein the image quality improving unit aligns the position of the design data of the pattern formed on the sample with the position of the secondary charged particle image of the sample surface generated by the charged particle imaging unit and then divides an area of the secondary charged particle image by using the design data and improves a quality of the divided secondary charged particle image. 6. An image processing method using a scanning type charged particle beam microscope, comprising the steps of:irradiating and scanning a focused charged particle beam over a surface of a sample formed with a pattern;detecting secondary charged particles emitted from the sample as the focused charged particle beam is irradiated to the sample and creating a secondary charged particle image of the sample surface; andprocessing the created secondary charged particle image of the sample surface;wherein, after the position of the design data of the pattern formed on the sample is aligned with the position of the secondary charged particle image of the sample surface, a quality of the created secondary charged particle image of the sample surface is improved by using the design data of pattern formed on the sample,wherein a way of improving the quality of the secondary charged particle image of the sample surface differs according to the design data. 7. An image processing method using a scanning type charged particle beam microscope according to claim 6, wherein the focused charged particle beam is an electron beam, the secondary charged particle image of the sample surface is a SEM image, and a quality of the SEM image of the sample surface is improved by using the design data. 8. An image processing method using a scanning type charged particle beam microscope according to claim 6, wherein, after the position of the design data of the pattern formed on the sample is aligned with the position of the secondary charged particle image of the sample surface, a quality of the created secondary charged particle image of the sample surface is improved by using design information or sample characteristic information. 9. An image processing method using a scanning type charged particle beam microscope according to claim 6, wherein, after the position of the design data of the pattern formed on the sample is aligned with the position of the secondary charged particle image of the sample surface, pattern geometry information of the design data is corrected and a quality of the secondary charged particle image is improved by using the design data whose geometry information has been corrected. 10. An image processing method using a scanning type charged particle beam microscope according to claim 6, wherein, after the position of the design data of the pattern formed on the sample is aligned with the position of the secondary charged particle image of the sample surface, an area of the secondary charged particle image is divided by using the design data and a quality of the divided secondary charged particle image is improved. 11. A scanning type charged particle beam microscope according to claim 1,wherein the image quality improving unit processes a resolution improvement or noise removing operation or contrast correction.
	description	The present invention relates to a solution with respect to stringent demands for image definition, without loss in speed, in computed radiography. In radiography it is important to have excellent image quality for the radiologist in order to make an accurate evaluation of a patient's condition. Important image quality aspects are image resolution and image signal-to-noise ratio (SNR). For computed radiography (CR) SNR depends on a number of factors. The number of X-ray quanta absorbed by the storage phosphor screen is important. SNR will be proportional to the square-root of the number of absorbed quanta. The so-called fluorescence noise, however, is of primary importance as well. This noise contribution originates from the fact that the number of photostimulated light (PSL) quanta detected for an absorbed X-ray quantum is small. Since much of the PSL is lost in the detection process in CR, fluorescence noise has an important contribution to the SNR. Hence, it is important that the number of photons detected per absorbed X-ray quantum is as high as possible. This situation is most critical in mammography, where X-ray quanta are used with low energy. Softer X-rays will give rise to less PSL centres and, therefore, to less PSL photons per absorbed X-ray quantum than harder X-rays. In CR, a large number of PSL centres is created by an absorbed X-ray quantum. However, not all PSL centres are stimulated in the read-out process, because of the limited time available for pixel stimulation and because of the limited laser power available. Typically, only about 30% of the PSL centres is stimulated to give rise to a PSL photon. Since these photons are emitted and scattered in all directions, only 50% of the PSL photons escape from the storage phosphor screen at the detector side. Only a fraction of the PSL photons emitted at the top side of the storage phosphor screen is guided to the detector, which has a limited quantum efficiency itself. For that reason, the number of PSL photons detected per absorbed X-ray quantum is of the order of 1 to 5 and the fluorescence noise contribution is important in CR systems. In addition, it is well-known that fine detail visualisation, i.e. high-resolution high-contrast images are required for many X-ray medical imaging systems and, more particularly, in mammography. In phosphor screens, light scattering by the phosphor particles and their grain boundaries results in loss of spatial resolution and contrast in the image. The number of PSL centres that is stimulated in the read-out process can be increased by reflecting the stimulating light at the bottom of the phosphor layer, i.e. by having a reflecting substrate. In this case the fraction of PSL centres that is stimulated will be higher than 30%. A reflecting substrate will also reflect the PSL photons, thereby increasing the number that leaves the screen at the top side to a fraction higher than 50%. The combination of these effects may increase the number of PSL centres detected per absorbed X-ray quantum to a significant extent, thereby strongly improving the image SNR. However, having a reflecting substrate causes increased scattering in a powder screen as well. The stimulating light spot is broadened when it is reflected at the screen substrate and spatial resolution is diminished. In powder CR screens, therefore, a reflective substrate is seldom used as such. It may be used in combination with an anti-halation dye on top of it. The anti-halation dye absorbs the stimulation light, thereby preventing its reflection and maintaining high resolution. As a consequence of having the anti-halation dye on top of the reflective substrate, however, the sensitivity of the CR plate is not remarkably enhanced. Preparation steps in order to manufacture such screens or panels have been described in WO 01/03156. In favor of image sharpness needle-shaped Eu-activated alkali metal halide phosphors, and more particularly, Eu-activated CsBr phosphor screens as described in EP-A 1 113 458 are preferred and, in view of an improved sensitivity, annealing of said phosphors as in EP-A 1 217 633 is advantageously performed, said annealing step consisting of bringing the cooled deposited mixture as deposited on the substrate to a temperature between 80° C. and 220° C. and maintaining it at that temperature for between 10 minutes and 15 hours. The high degree of crystallinity is easily analysed by X-ray diffraction techniques, providing a particular XRD-spectrum as has been illustrated in EP-A 1 113 458. Therefore a mixture of CsBr and EuOBr or EuBr3 is provided as a raw material mixture in the crucibles, wherein a ratio between both raw materials normally is about 90% by weight of the cheap CsBr and 10% of the expensive EuOBr, both expressed as weight %. It is an object of the present invention to offer a screen or panel that allows efficient creation and detection of PSL light, without leading to reduced resolution, i.e., to offer a CR screen that simultaneously provides high sensitivity and good resolution in a CR system. It is a further object of the present invention to offer a screen or panel for CR applications and, more in particular, for applications related with mammography. Still another object of the present invention is to reduce costs, more particularly with respect to the use of raw materials in the preparation process of the storage phosphor screen or panel. The above-mentioned advantageous effects have been realized by providing a storage phosphor screen or panel having the specific features set out in claim 1. Specific features for preferred embodiments of the invention are set out in the dependent claims. Further advantages and embodiments of the present invention will become apparent from the following description and drawings. As will become clear from the description and the examples hereinafter the object of the present invention has been achieved by providing a needle-shaped phosphor layer on top of the reflective substrate, more preferably a metal substrate and in a most preferred embodiment an aluminum substrate or layer acting as a mirror. It is well known that needle-shaped crystals act, to a certain extent, as light guides, thereby reducing lateral spread of stimulation and emission light in the phosphor layer. Surprisingly, however, it was found that, by having a reflective layer having a certain degree of roughness, under the needle-shaped phosphor layer, an increased sensitivity of the CR system by a factor of 2 was attained without affecting its resolution (sharpness) at all. According to the present invention an image storage screen or panel has been provided, wherein said screen or panel comprises a binderless needle-shaped stimulable phosphor of CsBr:Eu, wherein amounts of Eu-dopant are in the range of from 100 up to 400 p.p.m. versus CsBr, and a substrate, wherein said substrate has a surface roughness of less than 2 μm and a reflectivity of more than 80%. In order to measure said reflectivity use can be made of the measurement technique with a reflectometer as described in ASTM D523, 1985, corresponding with DIN 67530 (01.82) and ISO 2813 (1978) wherein reflections are measured at values of the reflection angles of 20° and 60°. Measurement normally takes place at reflection angles of 20° in the case of high gloss and at 60° for moderate gloss as decreasing values are obtained at lower measurement angles. Measurements made at 10 different sites at the film surface provide ability to calculate average values and standard deviations therefrom and to express said reflectance in percentage figures. It was not possible to derive surface glare characteristics from surface roughness data as optical theory for light interacting with smooth and rough surfaces tells that sinusoidal roughness differences of 0.01 μm reduce gloss by ca. 40% as has been set forth in Journal of Coatings Technology, Vol. 67 (851), p. 61, published December 1995. It is clear that the “reflectance percentage”, is closely related with “surface roughness”. Said roughness, called “Rz” has to be determined as the arithmetic mean or average roughness depth value Rt of five different, but adjacent measuring area on the “rough” reflecting substrate; said value Rt being defined as the difference in height between the highest “top” and the lowest “valley” measured onto said substrate. A suitable instrument for such microscopically fine measurements is a “perthometer”, by means of which the surface texture can be measured according to ANSI B46.1-1985 as published by The American Society of Mechanical Engineers. The said image storage screen or panel of the present invention thus comprises a binderless needle-shaped stimulable phosphor of CsBr:Eu, wherein amounts of Eu-dopant are in the range of from 100 up to 400 p.p.m. versus CsBr, and a reflecting substrate, wherein said substrate has a surface roughness of less than 2 μm, more preferably less than 1 μm (but exceeding 0 μm), and a reflectivity of more than 80%, and, in a more preferred embodiment it has a reflectivity of at least 90%, and even more preferably at least 95%. More preferred for use as a reflecting substrate of the screen or panel of the present invention is a metal substrate and, in a most preferred embodiment, the said metal substrate is an aluminum substrate, thereby forming a mirror. The reflecting metal substrate of the stimulable phosphor screen or panel may form the only support layer, but is, in a preferred embodiment further composed of two layers in contact with each other, said layers being a layer of the polymeric type or an amorphous carbon type (a-C)layer and, in contact therewith, an aluminum layer. Reason for this is that presence of only one metal support layer absorbs X-rays to such an extent that use of a phototimer is no longer interesting in some dedicated applications as will be explained furtheron hereinafter. Thicknesses of both layers, the reflective mirror layer (3) and the support layer (4) are, as illustrated in FIG. 1, in the range from about 2 mm for the support layer (4) and 1 μm for the reflective mirror layer (3), acting as a mirror, not only for incident stimulation radiation light from the read-out laser, but also for the stimulated radiation emitted by the stimulable phosphor, after having been laser stimulated, in order to transform the stored energy, stored in the phosphor layer (1), into stimulated radiation. In FIG. 1 an intermediate layer is provided as moistureproof layer (2) inbetween reflective mirror (3) and phosphor layer (1). The very thin reflective mirror preferably is an aluminum layer (having a thickness of about 1 μm) deposited onto an about 2 mm thick support layer (amorphous carbon—a-C layer—or a polymeric support layer), in the most common way, by means of the vapor deposition technique. Polymeric support films known in the art are, e.g., polyester film, polyvinylchloride, polycarbonate, syntactic polystyrene, etc. Preferred polymeric films are polyester ester film, e.g., polyethyleneterephthalate films, polyethylenenaphthalate films, etc. The thickness of the support auxiliary layer (4), in principle range from 1 μm to 500 μm. Instead of the cited polymeric film supports, it is however possible to make use of a fairly thin amorphous carbon film, e.g., 400 μm and laminate a 500 μm thick auxiliary film to it at the side away from the phosphor layer, as well as to use a thick amorphous carbon film, e.g., 2000 μm thick with a thin, e.g., 6 μm thick, polymeric film laminated to it. The relative thickness of amorphous carbon and polymeric film can be varied widely and is only directed by the required physical strength of the amorphous carbon during deposition of the phosphor layer and amorphous carbon and polymeric film can be varied widely and is only directed by the required physical strength of the amorphous carbon during deposition of the phosphor layer and the needed flexibility of the panel during use. The screen or panel according to the present invention thus has a substrate, the surface roughness of which is less than 2 μm, and even more preferably less than 1 μm, when measured by means of a perth-o-meter as set forth hereinbefore. If an extremely low surface roughness is envisaged, high quality optical polishing of the metal layer, preferably aluminum, can be performed as has e.g. been described in U.S. Pat. No. 6,350,176, wherein precise optical polishing of typical bare aluminum proceeds up to a surface roughness of less than about 300 nm rms and preferably about 50 nm rms while maintaining a “surface figure accuracy” in terms of “surface figure error” of not more than one-fifteenth of wave peak-to-valley. As described in U.S. Pat. No. 5,288,372 a method for changing a metal body has been provided, wherein as an undeniable advantage the said metal body surface is substantially uniformly roughened with a reproducible surface texture. The lower its roughness, the better the aluminum layer is acting as a flat mirror, and the better the image definition for the captured image, present as stored energy to be stimulated, and the lower the loss in speed. Adding a specularly reflecting layer between the phosphor layer and the amorphous carbon layer thus enhances both image quality and speed of the screen or panel. Also in panel according to the present invention, addition of such a specularly reflecting auxiliary layer may be beneficial. When such a layer is added, it preferably reflects at least 80% of the light impinging on it in a specular way. More preferably said layer reflects 90% of the impinging light specularly. Such metal layers preferably have a thickness under 20 μm, preferably under 10 μm. When in a screen or panel according to the present invention, a specularly reflecting layer is present, it is preferred that the layer is a thin aluminum layer. Preferably said thin aluminum layer has a thickness of less than or equal to 10 μm, more preferably from about 0.2 up to 5 μm. Since such a thin metal layer, preferably an Al layer, can be quite corrosion sensitive, it is further preferred that, when a specularly reflecting metal layer (3) is present in a screen or panel of the present invention, that this layer is covered with a barrier layer (2) that impedes water and/or moisture of reaching the relecting metal layer (3). Such a barrier layer (2) can, in principle, be any moistureproof barrier layer known in the art, but is preferably a layer of parylene. Most preferred polymers for use in the moistureproof layer and in a protective layer, in contact with the phosphor layer and farther from the support layer (4), of the screen or panel of the present invention, are chemical vacuum deposited poly-p-xylylene films. Such a poly-p-xylylene has repeating units in the range from 10 to 10000, wherein each repeating unit has an aromatic nuclear group, whether or not substituted. As a basic agent the commercially available di-p-xylylene composition sold by the Union Carbide Co. under the trademark “PARYLENE” is thus preferred. The preferred compositions for the barrier layer are the unsubstituted “PARYLENE N”, the monochlorine substituted “PARYLENE C”, the dichlorine substituted “PARYLENE D” and the “PARYLENE HT” (a completely fluorine substituted version of PARYLENE N, opposite to the other “parylenes” resistant to heat up to a temperature of 400° C. and also resistant to ultra-violet radiation, moisture resistance being about the same as the moisture resistance of “PARYLENE C”). Most preferred polymers for use in the preparation of the layer A of a phosphor panel of this invention are poly(p-2-chloroxylylene), i.e. PARYLENE C film, poly(p-2,6-dichloroxylylene), i.e. PARYLENE D film and “PARYLENE HT” (a completely fluorine substituted version of PARYLENE N. The advantageous effect of the parylene layers as moistureproof barrier layers in a screen or panel of the present invention is their temperature resistance: the temperature resistance of the parylene layers is such that they can withstand the temperature need for vacuum depositing the storage phosphor. Use of parylene layers in storage phosphor screens has been disclosed in e.g. EP-A's 1 286 362, 1 286 363, 1 286 364 and 1 286 365. In the production of binderless phosphor screens by means of chemical vapor deposition in vacuum, the support on which the phosphor is deposited can be heated to a temperature of up to about 400° C. So the use of a thermostable support is necessary. Therefore, a polymeric support, though being composed of elements having a low atomic number is not the most suitable. Including an amorphous carbon film (4) in the support however provides opportunities to produce a binderless storage phosphor screen on a support with low X-ray absorption, even by vacuum deposition at fairly high temperature. Amorphous carbon films suitable for use in this invention are commercially available through, e.g., Tokay Carbon Co, LTD of Tokyo, Japan or Nisshinbo Industries, Inc of Tokyo, Japan, where they are termed “Glass-Like Carbon Film”, or “Glassy Carbon”. In a binderless phosphor sceen or panel according to the present invention, the thickness of the amorphous carbon layer can range from 100 μm up to 3000 μm, a thickness between 500 μm and 2000 μm being preferred as a compromise between flexibility, strength and X-ray absorption. Such a low X-ray absorption moreover provides ability to make use of a so-called “phototimer”, already mentioned hereinbefore. Said “phototimer” comprises a radiometer for measuring the radiation dose passing through the object (patient) and the radiographic imaging system and a connection to the source of penetrating radiation for switching the penetrating radiation source off as soon as a pre-set dose is reached. In systems using such a “phototimer” it is important that a well measurable dose reaches the radiometer in the phototimer, since when the dose reaching the phototimer is too low, small differences will cause large irreproducibility and uncertainty with respect to the switching off of the source of penetrating radiation. In a practical setting the amount of radiation that reaches the “phototimer” is determined by the absorption of penetrating radiation by the object, wherein the tube side of the cassette contains the supported storage phosphor screen or panel and the back side of the cassette. Otherwise the absorption of the supported storage phosphor screen or panel is determined by the phosphor that is used, the amount of phosphor and the support: as a higher absorption in the phosphor layer is advantageous for speed and image quality of the radiographic imaging system there is a need to increase the thickness (the absorption) of the phosphor layer and this can only be done when the total absorption of phosphor layer and support remains almost constant, so that increasing the thickness of the phosphor layer must be compensated by lowering the absorption of penetrating radiation in the support. Especially in radiographic techniques where penetrating radiation of low energy is required as e.g. in mammography and some dedicated non-destructive testing applications, the much too high contribution of the support to the absorption of the phosphor screen or panel should be lowered. Lowering of the absorption of penetrating radiation by the support by lowering its thickness may however lay burden on the desired high mechanical strength of the screen or panel, its non-desired brittleness and, in case of vacuum deposition of the phosphor onto the said support, ability to withstand the high temperatures needed during vapor deposition. Amorphous carbon has therefore been selected as a particularly suitable support combining all advantages for use in a screen or panel of a stimulable phosphor, more particularly with respect to mechanical. Strength and heat resistance. As an alternative hard thin films, such as tetrahedral amorphous carbon (ta-C) films, have interesting and useful properties, such as extreme hardness (about 70 Gpa), thermal stability, high electrical resistivity, smooth surface and low friction, and transparency in wide spectral range because of the high sp3 fraction of carbon atoms (up to 87%) in the film. However, the high internal stress in the films can limit their applications, especially when it is desired to deposit a relatively thick film, as the film may flake away from the substrate. In order to reduce the internal stress of ta-C films, and in an attempt to improve adhesion of thick films of this type, different modifications have been made, as recently disclosed in U.S. Pat. No. 6,387,443 wherein amorphous silicon-carbon alloys (a-Si1-x Cx). In a particularly preferred embodiment of that invention the preparation method comprises depositing a layer of a composite film of carbon and silicon, suitably using a target which contains at least 40% carbon, the remainder being substantially silicon. The thus obtained composite Si—C film moreover provides suitable applications in the semiconductor field. As stress levels are reduced if compared with pure ta-C films, deposition at greater thicknesses than pure ta-C films are available with retainment of an acceptable hardness. According to the present invention a screen or panel has thus been provided wherein said substrate is an amorphous carbon layer (23) as part of the support (2) of the needle shaped stimulable phosphor layer (1), wherein said amorphous carbon layer (23) has been overcoated with a reflecting layer (22) as has more particularly been illustrated in FIG. 3. Furtheron a screen or panel (as in FIG. 3) has been provided, wherein said reflecting layer is a metal layer, and more preferably, wherein said reflecting layer is an aluminum layer (22). Since such a thin metal layer can be, quite corrosion sensitive it is preferred that, when a specularly reflecting aluminum layer is present in a panel or screen of the present invention, that this layer is covered with a barrier layer (further auxiliary layer (21)) that impedes water and/or moisture of reaching the relecting auxiliary layer. Such a barrier layer can be any moisture barrier layer known in the art, but is preferably a layer of parylene. Most preferred polymers for use in the protective layer of the screen or panel of the present invention, thereby protecting the phosphor layer (1) are vacuum deposited: preferred are chemical vacuum deposited poly-p-xylylene films already discussed hereinbefore. According to the present invention a screen or panel has been provided, wherein the moisture-repellent or moistureproof layers are present, not only inbetween the reflective aluminum layer coated onto an a-C layer substrate and the said phosphor layer, but also as a protective layer onto the said phosphor layer and farther from the said a-C substrate. Preferably the thickness of said parylene layer is in the range from 0.5 up to 15 μm, and, in a more preferred embodiment in the range from 1 up to 10 μm. “Parylene” is a polymeric material having excellent resistance to humidity. The layer may however, when used in an automatic panel handling apparatus, quite easily be physically damaged or simply worn off, so that during use the humidity resistance diminishes, thereby gradually loosing moisture resistance during use. Application of a further protective layer on top of the outermost parylene layer however is recommended in order to prevent the physical wear of the panel so that the useful life of the panel could be extended. Thus a panel according to the present invention, in a more preferred embodiment comprises a protective coating divided into at least two layers, one inner layer, being closest to the phosphor layer and another outermost layer farther away from the phosphor is layer wherein the inner layer is the parylene layer. As an outermost protective layer in the phosphor screen of the present invention any polymeric layer known in the art of applying a protective layer to a phosphor screen or panel may be used. This layer may be coated onto the phosphor panel by directly applying thereto a coating solution containing a film-forming organic, solvent-soluble polymer such as nitrocellulose, ethyl cellulose or cellulose acetate or poly(meth)acrylic resin and removing the solvent by evaporation. According to another technique a clear, thin, tough, flexible, dimensionally stable polyamide film is bonded to the phosphor panel as described e.g. EP-A 0 392 474. In a preferred embodiment, the outermost protective layer covering the parylene layer most remote from the support, and in contact therewith, is produced with a radiation-curable composition, thus providing, in another embodiment according to the present invention, a radiation cured polymeric layer. Use of a radiation curable coating as a protective top layer in a X-ray conversion screen has been described e.g. in EP-A 0.209 358 and in. U.S. Pat. Nos. 4,893,021 and 6,120,902. So e.g. the protective layer comprises a UV cured resin composition formed by monomers and/or prepolymers that are polymerized by free-radical polymerisation with the aid of a photoinitiator. The monomeric products are preferably solvents for the prepolymers used. Very useful radiation curable compositions for forming an outermost protective coating upon the moisture repellent parylene layer of the screen or panel according to the present invention contain, as primary components, (1) a cross-linkable prepolymer or oligomer or a mixture of cross-linkable prepolymers or oligomers, (2) a reactive diluent monomer or mixture of reactive diluent monomers, and (3) in the case of a UV curable formulation a photoinitiator. The usual amounts of these primary components calculated on the total coating composition are in the range from 30–100% by weight for the prepolymer, 10–70% by weight for the reactive diluent and 0–10% by weight for the photoinitiator optionally minor amounts (e.g. 5% by weight) of non-reactive organic solvent for the prepolymer may be present. Although any radiation curable composition known in the art, as e.g., the composition disclosed in EP-A 0 510 753 can be used, it may be very beneficial to have a coating solution containing fluorinated compounds so that the finished protective layer comprises at least 1% mole per mole of fluorinated moieties. Preferably the coating composition is so that the finished protective layer comprises between 5% and 50% (mole per mole) of fluorinated moieties. The fluorinated moieties can be present either in said cross-linkable prepolymer or oligomer or in said reactive diluent monomer or in both. Preferably the fluorinated moieties are added by using as diluent monomer a fluorinated monomer or by adding a fluorinated monomer to the mixture of diluent monomers. Very useful fluorinated monomers for adding fluorinated moieties to the protective layer of a storage panel of this invention are, e.g., C8F17CH2CH2N(CH3)COCH═CH2, C8F17CH2CH2OCOCH═CH2, C6F13C2H45COCH═CH2, C7F15CH2OCOC(CH3)═CH2, C8F17SO2N(C2H5)C2H4NHCOCH═CH2, (CF3)2CF(CF2)8C2H2SCOC(CH3)═CH2, C8F17SO2N(CH3)C2H4COOCH═CH2, C6F13CH2CH2OOCC(═CH2)COOCH2CH2C6F13, C7F15CH2OOCCH═CHCOOCH2C7F15, C6F13C2H4N(CH2CH2OH)COCO═CH2, C7F15CON(C2H5)C3H6SCOC(CH3)═CH2, C6F13CH2NHCOCO═CH2, C8F17CH2CH2OCH═CH2, (CF3)2CF(CF2)6CH2CH(OH)CH2OCOCH═CH2, (CH3)2CFOC2F4OCOCH═CH2, C8F17C2H4SO2N(C3H7)C2H4OCOCH═CH2, C7F15C2H4CONHC4H8OCOCH═CH2 C3H7(CFCF2O)CFCH2OCOCH═CH2 C7F15COOCH2C(CH3)2CH2OCOC(CH3)═CH2, C8F17SO2N(C2H5)C4H8OCOCH═CH2, (C3F7)2C6H3SO2N(CH3)C2H4OCOCH═CH2, C8F17CF═CHCH2N(CH3)C2H4OCOCH═CH2, C8F17SO2N(C2H5)C2H4NHCOCH═CH2, C8F17So2N(CH3)C2H4OCOCH═CH2, C8F17SO2N(C2H5)C2H4OCOC(CH3)═CH2, C8F17SO2N(CH3)CH2C6H4CH═CH2, C8F17C2H4SO2N(C3H7)C2H4OCOCH═CH2, C8F17SO2N(C2H5)C4H8OCOCH═CH2, and (C3F7)2C6H3SO2N(CH3)C2H4OCOCH═CH2 and combinations thereof. As set forth above, the fluorinated monomers may be used as diluent monomer(s) or may be used in combination with non-fluorinated diluent moieties. Very useful non-fluorinated diluent monomers for use in this invention are:methyl (metha)acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, glycidyl methacrylate, n-hexyl acrylate, lauryl acrylate, tetrahydrofurfurylmethacrylate and the like. When the fluorinated moieties are present in the cross-linkable prepolymer or oligomer then preferably a mixture of fluorinated and non-fluorinated prepolymers is used. Examples of fluorinated prepolymers—useful in order to bring fluorinated moieties in the protective layer of this invention—are, e.g., fluorinated polyester acrylates wherein the polyester includes fluorinated moieties brought in the polyester via fluorinated di- or poly-ols or via fluorinated di- or poly-carboxylic acid. Very suitable fluorinated diols and polyesters derived therefrom are those described in, e.g., U.S. Pat. Nos. 4,957,986; 5,004,790 and 5,109,103. Examples of suitable diols are, e.g., 3,3,4,4,5,5,6,6-octafluoro-octan-1,8-diol, or 2,2,3,3-tetrafluoro-1,4-butanediol, and most suitable diols are diols with the formula HOCH2(CF2)nCH2OH, wherein 2≦n≦10. Suitable fluorinated poly- or diacids are those corresponding to the formula HOOC(CF2)nCOOH or the methylesters thereof. Also terephthalic acid carrying —O—(CH2)10—(CF2)9—CF3 as a side group can be used in order to produce a fluorinated prepolymer suitable for use in a screen of the present invention. In both cases the polyester can then be functionalized with acrylates as described in EP-A-207 257. It is also possible to introduce the fluorinated moieties via the acrylation step; when using polyesters as described in, e.g., EP-A 0 207 257, these are functionalized by using fluorinated acrylates, as those shown above. When fluorinated prepolymers or oligomers are used, these can be mixed with non-fluorinated prepolymers or oligomers. Examples of suitable non-fluorinated prepolymers for use in a radiation-curable composition applied according to the present invention are the following unsaturated polyesters, e.g. polyester acrylates; urethane modified unsaturated polyesters, e.g. urethane-polyester acrylates. Liquid polyesters having an acrylic group as a terminal group, e.g. saturated co-polyesters which have been provided with acryl-type end groups, have been described in the published EP-A 0 207 257. When radiation-curing is carried out with ultraviolet radiation (UV), a photoinitiator is present in the coating composition in order to serve as a catalyst thereby initiating the polymerisation of the monomers and their optional cross-linking with the pre-polymers, resulting in curing of the coated protective layer composition. A photosensitizer for accelerating the effect of the photoinitiator may be present. Photoinitiators suitable for use in UV-curable coating compositions belong to the class of organic carbonyl compounds, for example, benzoin ether series compounds such as benzoin isopropyl, isobutylether; benzil ketal series compounds; ketoxime esters; benzophenone series compounds such as benzophenone, o-benzoylmethyl-benzoate; acetophenone series compounds such as acetophenone, trichloroacetophenone, 1,1-dichloroacetophenone, 2,2-diethoxyaceto-phenone, 2,2-dimethoxy-2-phenylacetophenone; thioxanthone series compounds such as 2-chlorothioxanthone, 2-ethylthioxanthone; and compounds such as 2-hydroxy-2-methylpropiophenone, 2-hydroxy-4′-isopropyl-2-methylpropiophenone, 1-hydroxycyclohexylphenylketone; etc. A particularly preferred photoinitiator is 2-hydroxy-2-methyl-1-phenyl-propan-1-one which product is marketed by E. Merck, Darmstadt, Germany under the trade name DRACUT 1173. The above mentioned photopolymerisation initiators may be used alone or as a mixture of two or more. Examples of suitable photosensitizers are particular aromatic amino compounds as described e.g. in GB-Patents 1,314,556 and 1,486,911, in U.S. Pat. No. 4,255,513 and merocyanine and carbostyryl compounds as described in U.S. Pat. No. 4,282,309. To the radiation-curable coating composition there may be added a storage stabilizer, a colorant, and other additives, and then dissolved or dispersed therein in order to prepare the coating liquid for the protective layer. In addition to these primary components additives may be present, as e.g. surfactants, solid lubricants, waxes, de-foamers and plasticizers, without however being limited thereto. It is clear that it is the purpose of an outermost layer, coated upon the moisture repellent parylene layer most remote from the aluminum coated amorphous carbon substrate of the panel, to provide the said phosphor panel of the present invention with good abrasion properties. The abrasion properties of such an outermost layer are tested in a Taber abrasion test using a TELEDYNE TABER 5130 Abraser (trade name of Taber Industries, New York, USA) with rotation elements CALIBRASE CS10F, sandpaper P220, and load of 250 g on each element. Losses in thickness of such an outermost protective layer can be measured after 500 cycles. Preferably the said outermost layer looses, in the test as described above, at most 25% of its thickness. More preferably the layer looses in the test above at most 20% of its thickness and, even most preferably, at most 15%. If desired or required, the outermost layer of the present invention may include spacing particles in favor of improved transportability and adjusted electrostatic properties. Suitable spacing agents in form of friction reducing polymer beads are selected from the group consisting of solid polystyrene, solid polyalkylene and a solid organic fluorinated polymer. Preferably the spacing agents are beads incorporating fluorinated moieties. Such beads have been described e.g. in U.S. Pat. No. 4,059,768. In the construction of the scanning apparatus used for reading storage phosphor screens the trend is towards more and more compact apparatus, so that the distance between the (moving) storage phosphor screen and mechanical (moving) parts of the scanner can become very low (e.g. inbetween 10–100 μm). When then a storage phosphor screen with an outermost protective layer coated upon the moisture repellent parylene layer most remote from the substrate has protruding beads it is important that the beads do not touch mechanical parts of the scanner and that this is true even when the storage panel shows some wobble during transport in the scanner. Therefore beads used as spacing particles in a storage phosphor screen of the present invention preferably have a median volume diameter, dv50, so that 5 μm≦dv50≦25 μm and a median numeric diameter, dn50, so that 1≦dv50/dn50≦1.20. Further the beads are preferably adapted to the thickness, t, of the outermost protective layer on the storage panel of the present invention so that said polymeric beads have a median volume diameter, dv50, wherein 1.25≦dv50/t≦4.0. In favor of flatness of the panel having as a protective layer the single parylene layer or the double-layer with the parylene layer, overcoated with an outermost layer, for the panel of the present invention it is recommended to polish the phosphor layer deposited from the vapor phase to a predetermined even layer thickness before coating a protective layer thereupon by the method as described in WO 02/20868. The phosphor layer in a flat screen or panel of the present invention may in principle comprise any phosphor known in the art, and it may be a prompt emitting phosphor as well as a photostimulable phosphor and, furthereon, the phosphor layer in a panel according to the present invention may be a layer including a phosphor mixed in a polymer binder as well as a binderless phosphor layer. It is however preferred that the phosphor layer in the panel according to the present invention is sandwiched between two moisture repellent layers, preferably both being composed of parylene as set forth hereinbefore. It is advantageous that the stimulable phosphor layer is “surrounded” by a moisture-proof parylene “package” as in the vicinity of the edges, both parylene layers, contacting each other, indeed provide a moisture-proof construction. The screen or the panel of the present invention can also have reinforced edges as described in, e.g., U.S. Pat. No. 5 334 842 and U.S. Pat. No. 5 340 661. The surface of the phosphor layer (1) in a panel or screen of the present invention can be made smaller than the surface of the support (2) so that the phosphor layer does not reach the edges of the support. Such a screen has been disclosed in, e.g., EP-A 1 286 363. Within the scope of the present invention however, a phosphor panel having a protective layer according to the present invention comprises a hygroscopic phosphor having storage capacity, thus being a photostimulable phosphor, most preferably having a binderless phosphor layer. Among the binderless phosphor layers a phosphor layer comprising needle-shaped phosphor particles separated by voids, of a CsX:Eu phosphor, wherein X represents a halide selected from the group consisting of Br and Cl, is most preferred as a phosphor layer in the present invention. Such phosphors have been described in EP-A 1 113 458 and the method to prepare them has been described e.g. in WO01/3156 and the corresponding EP-A 1 203 394. A europium activated cesium bromide phosphor giving an increased stimulated emission amount, and which is also suitable for use in the screen or panel according to the present invention, has, besides low amounts of dopant, minor or neglectable amounts of trivalent europium versus divalent europium, which is measurable from emission intensities of divalent and trivalent europium ions present. Preferably said emission intensities are differing with a factor of at least 103, and more preferably even with a factor of 105 to 106. A screen or panel according to the present invention thus preferably comprises a stimulable phosphor layer having CsBr:Eu phosphor as a stimulable or storage phosphor, wherein Cl may be present. In a preferred embodiment the panel or screen according to the present invention is a binderless phosphor panel or screen, wherein said phosphor layer comprises a needle-shaped CsX:Eu phosphor, wherein X represents a halide selected from the group consisting of Br and Cl. Referring to the documents cited in the “background of the invention” with respect to the preparation of the more desired CsBr:Eu2+ phosphor, binderless storage phosphor panels or screens having such a phosphor layer have been prepared and build up in order to get a panel or screen according to the present invention. In a more preferred embodiment a CsBr:Eu panel is thus envisaged, in view of production cost of starting raw materials, wherein an amount of Europium dopant versus CsBr in the range from 100–400 p.p.m., and even more preferably in the range from 100–200 p.p.m., is measured (by means of X-ray fluorescence). Apart for the use of EuBr3 as a source of Europium dopant, an increased heating temperature (850° C.) of a crucible has been applied, wherein heating in a more homogeneous way has been realized. As a function of coating (evaporating) temperature ratios of raw materials have advantageously been adapted in favor of lower amounts of starting raw material (especially dopant material) and production cost, without resulting in changes in composition: so higher vaporization temperatures for the raw material mixture in ratio amounts of 99.5 wt % CsBr and 0.5 wt % EuOBr provide the same result (related with speed) as before. Such a result can be interpreted as possibly due to a more homogeneously divided phosphor layer, allowing lower amounts of Eu-dopant. According to the present invention screens of CsBr:Eu2+ phosphors having lower amounts of Europium dopant, i.a. in the range from 100–400 p.p.m. versus 800 p.p.m. (see Examples in EP-A 1 113 458, said amounts having been determined with X-ray fluorescence) have thus become available. Opposite thereto screens requiring an amount of dopant in the range from 1000 p.p.m., and even up to 3000 p.p.m. as measured, are probably indicating that dopants do not seem to have been built in efficiently (homogenously) as no speed increase is detected versus the screens doped with low amounts of dopant. So in one embodiment, as described in EP-Application No. 02100295, filed Mar. 26, 2002, needle-shaped CsBr:Eu2+ storage phosphor particles in form of a cylinder are preferred, said particles having an average cross-section diameter in the range from 1 to 30 μm (more preferably in the range from 2 to 15 μm, and an average length, measured along the casing of said cylinder, in the range from 100 μm up to 1000 μm more preferably from 100 μm up to 500 μm. Needle-shaped CsBr:Eu2+ storage phosphor particles having an average aspect ratio of length to cross-section diameter in the range from 5 to 200 (and even in the narrower range from 20 to 100) are most preferred. Variation coefficients upon average cross-section diameter and average casing length in the range from 0.05 up to 0.30 (and even in the range from 0.05 up to 0.20) for the needle-shaped CsBr:Eu2+ storage phosphor particles, are representative for the homogeneity of the needle-shaped phosphors. The radiation image storage phosphor screen or panel emitting radiation after stimulation of phosphor particles having stored energy from X-rays having impinged upon said screen or panel in a most preferred embodiment thus comprises: an amorphous carbon substrate covered with a planar aluminum layer serving as a planar mirror; a multiplicity of cylindrical needle-shaped phosphors extending onto the surface of the aluminum layer, said phosphors being the needle-shaped CsBr:Eu2+ storage phosphor particles (having Eu-dopant in an amount as set forth above) in form of a cylinder, as mentioned; a moisture repellent layer at both sides of the phosphor layer; and, optionally, an outermost protective layer against abrasion due to frequent use of said panel in computed radiographic applications. In a further embodiment the radiation image storage phosphor screen according to the present invention, has a binderless phosphor with needle-shaped phosphors having cylindrical walls, wherein a light reflective coating is disposed along the walls of said cylinders, arranged in order to reflect, at least partially, radiation emitted by said phosphors after having performed stimulation thereupon. Furthermore the radiation image storage phosphor plate or panel comprises one or more dyes. Presence of the dye is not restricted to whatever a layer in the layer arrangement presented hereinbefore, but it is preferred that at least dye in nanocrystalline form is present in at least one layer. Said at least one nanocrystalline dye compound may further comprise colloidal silica. More preferably the said dye is a compound, being a copper complex of a cyanine dye and, even most preferably said dye compound is a Cu-sulphonated phthalocyanine (β-Cu-phthalocyanine). The stimulable phosphor particles, colored with a dye providing ability to be added from an aqueous-free medium, thereby show an excellent light-stability, which, as a consequence is gives an excellent image resolution. Coating amounts of said dyes are in the range from 1 μg/m2 up to 1000 μg/m2. As has already been taught or suggested before the flat screen or panel of the present invention should have a strong protective layer in order to provide ability for easy transport through a scanning module without causing jamming. The layer arrangement with a binderless photostimulable phosphor screen, preferably vapor deposited alkali metal halide phosphor (preferably the needle-shaped CsX:Eu phosphor, wherein X represents a halide selected from the group consisting of Br and Cl) onto the substrate, moreover provided with at least one nanocrystalline dye compound present in at least one layer on the said substrate, coated on an aluminum covered amorphous carbon substrate moreover is in contact with a Fibre Optic Plate (FOP). When on such a phosphor layer with needle shaped phosphor crystals, separated by voids, a (water repellent) layer (thus showing very low water permeability) is deposited, it is preferred that this layer is a chemical vacuum deposited parylene layer, while such a layer not only covers the surface of the needle crystals, but also covers the voids between the needles thus protecting the edges of the phosphor needles thoroughly against humidity. A phosphor panel of the present invention may also comprise edge reinforcements as the ones described in e.g. U.S. Pat. Nos. 5,334,842 and 5,340,661. In a particular embodiment of the present invention the surface of the phosphor layer is smaller than the surface of the support so that the phosphor layer does not reach the edges of the support. Thus a panel with a support having a surface larger than the main surface of the phosphor layer, so that the phosphor layer leaves a portion of the support free. In a preferred embodiment the protective layer(s) cover, at least in part, the portion of the support left free by the phosphor layer. An advantage of such a construction resides in the fact that the edges of the phosphor layer do not touch mechanical parts of the apparatus and are thus less easily damaged during use of the panel, more particularly e.g. during transport in the scanner. Another advantage of this construction is that no special edge reinforcement is necessary (although, if desired, further edge reinforcement can be applied). Although a construction of a phosphor panel wherein the surface of the phosphor layer is smaller than the surface of the support, so that the phosphor layer does not reach the edges of the support, represents a specific embodiment of the present invention, such a construction can be beneficial for the manufacture of any phosphor panel covered with any protective layer known in the art. The invention moreover encompasses a method for the preparation of a phosphor panel comprising the steps of: providing a support (of amorphous carbon, whereupon an aluminum mirror layer has been deposited), chemical vapor depositing a parylene layer on said support (=on said aluminum layer), applying a phosphor layer on said support, chemical vapor depositing another parylene layer, this time on said phosphor layer, and, optionally, applying an outermost protective layer most remote from the support. The present invention moreover includes a method for the preparation of a binderless phosphor panel comprising the steps of: providing a support (of amorphous carbon, whereupon an aluminum mirror layer has been deposited), chemical vapor depositing a parylene layer on said support (=upon said aluminum layer), vapor depositing a CsX:Eu phosphor, wherein X represents a halide selected from the group consisting of Br and Cl, forming thereby a binderless phosphor layer on said support; optionally polishing the phosphor layer; chemical vapor depositing another parylene layer, this time upon said phosphor layer, and, optionally, applying an outermost protective layer most remote from the support, therefore applying a radiation curable solution on top of said parylene layer most remote from the support, and curing it by UV and/or electron beam (EB) exposure. According to the present invention use of a screen or panel as disclosed before in a system for computed radiography has further been claimed. Use of a radiation image storage phosphor panel in an image forming method for storing and reproducing a radiation image thus comprises the steps of: exposing said radiation image storage panel with radiation energy having passed through an object or having been emitted by said object and storing said radiation energy in form of a latent image on said image storage panel; releasing the stored energy in form of light upon irradiation with stimulating rays of the visible or infrared region, thereby emitting light from the ultraviolet or visible wavelength region collecting said light released from the storage panel by light-collecting means and converting the collected light into a series of electric signals; producing an image corresponding to the latent image from the electric signals. More particularly use of a less expensive screen or panel according to the present invention in mammographic applications is claimed as those particular applications are extremely desiring high image quality, and, more particularly, sharpness. While the present invention will hereinafter be described in connection with preferred embodiments thereof, it will be understood that it is not intended to limit the invention to those embodiments. 1. phosphor layer 2: 1–10 μm moisture-repellant or resistant (parylene) layer 3: 1 μm reflective mirror layer 4: 2 mm support layer 21 auxiliary layer, moisture barrier layer 22 auxiliary layer, specularly reflecting layer 23 amorphous carbon layer 24 auxiliary layer, polymeric layer A. Preparation of the Vapor Deposited Screens: The only differences in the preparation method were related, apart for the choice of the crucible temperature (850° C.), with the crucible design, in that an improved refractory (tantalum) crucible was used wherein a more homogeneous heating provoked a more homogeneous melting and composition of the vapor stream after evaporation. Different screens were produced with differing substrates. Before the start of the evaporation, the chamber was evacuated to a pressure of 4.10−5 mbar. A first screen (S-D) was made with an Al substrate. Because of its composition and surface roughness the Al substrate was dull and did not reflect in a mirrorlike way. A second screen was made on an a-C substrate on which an Al mirror was applied by vapor deposition (S-M). The substrate had a clear mirrorlike reflection, because of the surface smoothness and because of the pureness of the aluminum. For both screens the deposited CsBr:Eu layer had a thickness of about 160 μm. Europium dopant amounts, measured by X-ray fluorescence were all in the range between 150 and 180 p.p.m. versus CsBr for the screens or panels in the Table 1 hereinafter: even for such low amounts of Europium dopant in the CsBr:Eu phosphor layer no loss in speed was found. Such a low amount of dopant is directly related with a lower (especially raw dopant material) cost in the phosphor preparation. C. Measurement of the Screen Sensitivity: The screens were homogeneously irradiated at 30 keV and 5 mA for 10 s. Read out was done in a flying spot scanner. In the scanner, the scanning light source was a 30 mw diode laser emitting at 685 nm. A 4-mm BG-39® (trade name of Hoya) filter, covered with a dielectric coating was used to separate the stimulation light from the screen emission light. The scan-average levels (SAL's) were determined as the average signal produced by the screens in the photomultiplier tube of the flying-spot scanner. D. Measurement of Resolution: In a second measurement, the sharpness of the images, produced by the screens was measured. As a measure for the sharpness, the edge response was determined and used to calculate the modulation transfer function (MTF) as a function of spatial frequency. A lead sheet was placed on top of the cassette, containing the screens. The lead sheet was imaged at 30 keV and 5 mA during 30″. The screens were scanned with the flying spot scanner described above. The resulting profile was used to calculate the MTF as a function of spatial frequency. The sensitivity of the screen with reflective substrate (S-M) relative to the sensitivity of the screen with dull Al substrate (S-D) was 170%. FIG. 2 shows the MTF (Modulation Tranfer Function) obtained for both screens. It is clear that both screens lead to very comparable resolutions. The same experiment was done for a powder screen: the powder phosphor layer was applied onto a black PET substrate and onto a white, reflecting PET substrate. For the powder screen as for the needle screen a significant increase in sensitivity was observed, but opposite to the observation for the needle screen, its resolution was strongly degraded and was inferior for the powder screen. Having described in detail preferred embodiments of the current invention, it will now be apparent to those skilled in the art that numerous modifications can be made therein without departing from the scope of the invention as defined in the appending claims.
	abstract	An X-ray lens assembly, a device including the X-ray lens assembly and a method of manufacturing the X-ray lens assembly are described. The X-ray assembly comprises a tube member (50) including an inlet opening (90) for X-rays and an outlet opening (94) for X-rays. Additionally, the assembly comprises a capillary X-ray lens (28) mounted inside the tube member (50). The X-ray lens (28) may be mounted inside the tube member (50) by a stabilizing agent and/or by one or more separate mounting structures (96A, 96B).
	summary
	claims	1. A method for monitoring a power rise during startup of a nuclear reactor, which comprises: detecting power of a nuclear reactor in power range channels with measuring signals; and monitoring at least the measuring signal of one power range channel during the startup of the nuclear reactor to initiate a countermeasure, using a logic circuit, when a range between a lower limit and an upper limit of a power band in a lower part of a measuring range of the power range channel is traversed more quickly than a prescribed minimum time due to an excursion. 2. The method according to claim 1 , wherein the step of initiating a countermeasure does not include discontinuing the startup of a nuclear reactor when the measuring signal for the reactor power does not exceed an upper limit of a power band for a duration of the prescribed minimum time, said upper limit being higher than said lowers limit. claim 1 3. The method according to claim 1 , which further comprises forming the measuring signal of each power range channel for the reactor power by summing measuring signals of power distribution detectors distributed over a volume of a reactor core. claim 1 4. The method according to claim 2 , which further comprises forming the measuring signal of each power range channel for the reactor power by summing measuring signals of power distribution detectors distributed over a volume of a reactor core. claim 2 5. The method according to claim 1 , which further comprises fixing at least one of an operationally independent lower and upper limit mark for the power band. claim 1 6. The method according to claim 2 , which further comprises fixing at least one of an operationally independent lower and upper limit mark for the power band. claim 2 7. The method according to claim 1 , which further comprises placing the power band in a lower third of a rated maximum power of the reactor. claim 1 8. The method according to claim 1 , which further comprises placing the power band in a lower quarter of a rated maximum power of the reactor. claim 1 9. The method according to claim 2 , which further comprises placing the power band in a lower third of a rated maximum power of the reactor. claim 2 10. The method according to claim 2 , which further comprises placing the power band in a lower quarter of a rated maximum power of the reactor. claim 2 11. The method according to claim 1 which further comprises prescribing at least one of a width of the power band and a minimum time in an operationally independent manner. claim 1 12. The method according to claim 2 , which further comprises prescribing at least one of a width of the power band and a minimum time in an operationally independent manner. claim 2 13. The method according to claim 1 , which further comprises setting a width of the power band at less than ⅓ of a rated maximum power. claim 1 14. The method according to claim 1 , which further comprises setting a width of the power band at less than ⅕ of a rated maximum power. claim 1 15. The method according to claim 2 , which further comprises setting a width of the power band at less than ⅓ of a rated maximum power. claim 2 16. The method according to claim 2 , which further comprises setting a width of the power band at less than ⅕ of a rated maximum power. claim 2 17. The method according to claim 1 , which further comprises setting the minimum time at less than one minute. claim 1 18. The method according to claim 2 , which further comprises setting the minimum time at less than one minute. claim 2 19. The method according to claim 1 , which further comprises continuously detecting the reactor power with measuring signals of a plurality of power range channels, and redundantly monitoring the reactor power. claim 1 20. The method according to claim 2 , which further comprises continuously detecting the reactor power with measuring signals of a plurality of power range channels, and redundantly monitoring the reactor power. claim 2 21. The method according to claim 1 , which further comprises monitoring signals of additional neutron flux detectors during startup of the reactor having a reactor core from which control rods are being withdrawn. claim 1 22. The method according to claim 2 , which further comprises monitoring signals of additional neutron flux detectors during startup of the reactor having a reactor core from which control rods are being withdrawn. claim 2 23. The method according to claim 21 , which further comprises monitoring the power of the reactor core for maintenance of current maximum values with the aid of the additional neutron flux detectors, and varying the current maximum value as a function of operation during startup. claim 21 24. The method according to claim 22 , which further comprises monitoring the power of the reactor core for maintenance of current maximum values with the aid of the additional neutron flux detectors, and varying the current maximum value as a function of operation during startup. claim 22
042017386	summary	This invention relates to a method of preparing U.sub.3 O.sub.8 for use as a nuclear fuel material, in particular, for directly preparing U.sub.3 O.sub.8 having a controlled particle size distribution from an aqueous solution of uranyl nitrate. The invention is particularly useful for the recycle of enriched uranium in the powder metallurgy manufacture of U.sub.3 O.sub.8 -Al nuclear reactor fuel assemblies. In powder metallurgy processes for the preparation of U.sub.3 O.sub.8 nuclear fuel material, control of the particle size is required to provide a compatible blend of the U.sub.3 O.sub.8 fuel material and the aluminum matrix material, and to provide the desired physical and nuclear characteristics of the product U.sub.3 O.sub.8 -Al fuel cores. Careful control of U.sub.3 O.sub.8 particle size distribution is necessary because (1) particles or agglomerates larger than 150 .mu.m tend to form large hard particles that can penetrate nuclear fuel cladding and cause undesirable hot spots and result in melting of the cladding during irradiation, (2) fuel containing 40 wt % or more of particles smaller than 44 .mu.m is susceptible to fission-gas blistering during irradiation, and (3) the particle size distribution of the U.sub.3 O.sub.8 must match the particle size of the aluminum powder matrix material to obtain a sufficiently homogeneous U.sub.3 O.sub.8 -Al blend for isostatic compaction. This last factor has been established empirically as a particle size range of between about 150 and 44 .mu.m, based on the first two factors and on the particle size distribution of commercially available aluminum powder for powder metallurgical processes. One such commercial aluminum powder is Alcoa Atomized Powder No. T-108, available from the Aluminum Company of America, Pittsburgh, Pennsylvania 15219, which has an optimum particle size range for the preparation of the U.sub.3 O.sub.8 -Al fuel cores. Heretofore, U.sub.3 O.sub.8 nuclear fuel material for use in the manufacture of U.sub.3 O.sub.8 -Al powder metallurgy compacts for nuclear fuel has been obtained by calcining UO.sub.3 prepared by the thermal denitration of uranyl nitrate solution. The UO.sub.3 prepared by this conventional process has a particle size distribution of between about 150-600 .mu.m. Calcining the UO.sub.3 to U.sub.3 O.sub.8 does not reduce the particle size to the desired range; thus, the U.sub.3 O.sub.8 prepared by this process must be ground and sized to achieve a particle size distribution compatible with aluminum powder for powder metallurgy processing. See, for example, A Chemical Recovery System for Safeguarding Unirradiated Uranium, USAEC Report Y-MA-3582, July 1, 1970, p.10. However, grinding the U.sub.3 O.sub.8 is undesirable because (1) it is a slow operation, (2) it generates excessive fine particles, (3) it presents a potential for release of radioactive contaminates, and (4) it leads to U.sub.3 O.sub.8 powder buildup in the grinding equipment. In view of the difficulties associated with the conventional process described above, those skilled in the art will recognize that a number of uranium salts, such as uranyl or uranous oxalate and uranyl or uranous formate, prepared from uranyl nitrate may serve as possible intermediate salts for preparing U.sub.3 O.sub.8 having the desired particle size range. However, tests conducted by precipitation and calcination of the uranium oxalates and uranous formate did not produce U.sub.3 O.sub.8 with the appropriate particle size distribution. Further, attempts were made to prepare U.sub.3 O.sub.8 having a uniform particle size range by the evaporation of solvent from an unsaturated uranyl formate solution followed by calcination to U.sub.3 O.sub.8. While this method produced an excellent yield of uranium, the dry product, even when stirred during evaporation, consisted of undesirably large particle agglomerates clearly unsuitable for compatible powder metallurgy use without grinding and particle sizing. One solution that has been suggested for the problem of agglomeration in the precipitation of uranyl formate is disclosed in United Kingdom Patent Specification No. 1,230,937, published May 5, 1971. In this U.K. patent uranyl nitrate is precipitated with formic acid in a vertical column partially filled with glass balls. Stirring the glass balls during the reaction serves to dry and grind the resulting precipitate to yield a dry uranyl formate powder. There is no indication in this patent of particle size, particle size distribution, or whether the product will calcine to a suitable U.sub.3 O.sub.8 powder. SUMMARY OF THE INVENTION Therefore, it is the object of the present invention to provide a method for the direct preparation of U.sub.3 O.sub.8 nuclear fuel material having a controlled particle size distribution from uranyl nitrate solution. It is also an object of this invention to provide a method for the preparation of U.sub.3 O.sub.8 for the powder metallurgical manufacture of nuclear fuel that does not require the grinding of the U.sub.3 O.sub.8. It is a still further object to provide U.sub.3 O.sub.8 in powder form that has a particle size distribution compatible with a matrix material for the manufacture of nuclear fuel material. In accordance with the present invention, U.sub.3 O.sub.8 having a controlled particle size distribution is directly prepared from an aqueous solution of uranyl nitrate by adding formic acid to effect a denitration and form an unsaturated solution of uranyl formate. Additional stoichiometric excess of formic acid is added to the unsaturated uranyl formate to precipitate uranyl formate monohydrate. The resulting crystalline uranyl formate monohydrate is then calcined to produce U.sub.3 O.sub.8 having a controlled particle size distribution. It has been found that U.sub.3 O.sub.8 powder prepared by this technique has the following desirable physical characteristics: (1) no large particles, (2) crystalline particle morphology, and (3) narrow particle size distribution that is compatible with aluminum powder. The foregoing properties are achieved without grinding or sieving operations.
	summary
	description	This invention was made with Government support under contract F33615-03-2-2306, awarded by the United State Air Force. The Government has certain rights in this invention. The present invention relates to electro-mechanical actuators and more particularly to an efficiency monitor for an electro-mechanical actuator. Concern about jamming within an actuator, such as an electro-mechanical actuator (EMA), has hindered the acceptance of actuators for use in various structural systems, e.g., mobile platforms. For example, such a jammed actuator that controls the movement of a primary flight control surface of an aircraft can create a potentially very dangerous safety situation for the aircraft. Empirical data strongly suggests that degradation of the actuator mechanism is gradual. But, typically, such data does not provide health data, i.e., periodic wear status data, of the actuator during the useful life of the actuator. Systems that monitor the health of actuators, may include numerous dedicated sensors to monitor various actual actuator loads, characteristics, parameters and conditions. Such sensors would add significantly to the cost and complexity of the actuator and ultimately reduce reliability of the actuator. In various embodiments, the present invention provides a system and method for monitoring a reliability status of an actuator, for example, an electro-mechanical actuator (EMA). The method includes determining a virtual actuator load value (VALV) based on various load factor parameters of a structural system component controlled by the actuator, .e.g., a control surface of a mobile platform. The load factor parameters are acquired absent sensed load values from the actuator. The method additionally includes determining a virtual output force value (VOFV) based on various actuator operational control values that occur in response to a torque command from a main control and monitoring system of the structural system. Furthermore, the method includes calculating a virtual torque efficiency (VTE) of the actuator based on the VALV and the VOFV. The VTE is periodically calculated, e.g., 100 times per second, as the measured load factor parameters and the measured actuator operational control values change during operation of the structural system. The VTE data is collected, stored and analyzed to monitor the reliability status of the actuator during the life of the actuator. Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating various preferred embodiments of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. Referring to FIG. 1, in various embodiments, a reliability status monitoring system 10 is provided for monitoring the reliability status of at least one actuator 14, for example an electro-mechanical actuator (EMA), a digital linear motor or any other electrical motor driven system with a positional output. Each actuator 14 controls the movement of at least one component 18 of a structural system 22, such as a mobile platform. For example, each actuator 14 can control the movement of a control surface of an aircraft. Although the structural system 22 is exemplarily illustrated in FIG. 1 as an aircraft, the structural system 22 is not limited to aircraft or other mobile platforms such buses, ships, trains or other vehicles. The structural system 22 can be any structural system that incorporates one or more actuators 14 to control the movement of at least one component 18 of the structural system 22. For example, the structural system 22 could be a heating, ventilation and air conditioning system that incorporate one or more actuators 14 to control the movement of one or more louvers, shutters, turrets or valves to control the direction and/or volume of air flow. Furthermore, although each actuator 14 is exemplarily illustrated in FIG. 1 as a single actuator, it should be understood that the reliability status monitoring system 10 can be utilized to monitor the reliability status of a plurality of interconnected actuators 14. For example, a plurality of interconnected actuators 14 can be incorporated to provide redundancy and/or added control of the structural component(s) 18, and remain within the scope of the invention. The reliability status monitoring system 10 includes the one or more actuators 14 and a main control and monitoring system (MCMS) 26 of the structural system 22 that controls and/or monitors various operations of the structural system 22. For example, the main control and monitoring system 26 can be the main computer-based aircraft management system of an aircraft that controls such things as transmission of pilot commands and monitors such things as air speed, gravitational forces on the aircraft and amount of deflection of various aircraft control surfaces. Although it should be understood that the reliability status monitoring system 10 can be employed to monitor the reliability status of one or more actuators 14, for simplicity and clarity, the one or more actuators 14 will generally be referred to herein in the singular, i.e., simply as the actuator 14. Similarly, although it should be understood that each actuator 14 can be operatively connected to one or more components 18, for simplicity and clarity, the one or more components 18 will generally be referred to herein in the singular, i.e., simply as the component 18. Referring to FIG. 2, the reliability status monitoring system 10 additionally includes an actuator efficiency module 30 that is a software based module executable by any suitable processor or microprocessor. For example, in various embodiments, the actuator efficiency module 30 can be included in the MCMS 26 and executed by an MCMS processor (not shown). Accordingly, for illustration purpose only, the actuator efficiency module 30 is shown in FIG. 1 as being included in the MCMS 26, but could be included as part of any other computer-based subsystem of the structural system 22 or remote computer-based system communicatively connected to the MCMS 26 via wired or wireless communication. The actuator efficiency module 30 provides a software model for determining a virtual torque efficiency of the actuator 14 by comparing a virtual actuator output force to a virtual actuator load generated using previously compiled surface load model calculations Generally, the actuator efficiency module 30 acquires or receives various measured load factor parameters of the structural component 18 that do not include actual measured load values of the actuator 14. Based on the various measured load factor parameters the actuator efficiency module 30 generates a virtual actuator load value (VALV). Similarly, the actuator efficiency module 30 acquires or receives various measured operational control values of the actuator, and based on the various measured operational control values of the actuator, generates a virtual output force value (VOFV) of the actuator 14. Based on the VALV and the VOFV, the actuator efficiency module 30 calculates an approximate virtual torque efficiency (VTE) 32 of the actuator 14. The actuator efficiency module 30 repeatedly calculates the VTE 32 in accordance with a desired frequency, e.g., 100 Hz or 100 times per second, as the measured load factor parameters and actuator operational control values change in response to changing operational and environmental conditions of the structural system change. Thus, the VTE 32 can be tracked and analyzed to track trends and/or determine the reliability status of the actuator 14 during the life of the actuator 14. For example, over time, as the actuator 14 is utilized and incurs wear, the VTE 32 will decrease helping to identify projected points of failure, and providing an indicator of when to replace or repair the actuator 14 prior to failure. More particularly, in various embodiments, the actuator efficiency module 30 includes a virtual actuator load module or routine 34 that utilizes the various measured load factor parameters to generate the VALV. The measured load factor parameters are provided to the actuator efficiency module from the MCMS 26. Execution of the virtual actuator load module 34 generates the VALV based on the input load factor parameters, as described further below. The load factor parameters are actual measured parameters that effect or factor into the actual surface load exerted on the component 18 and thus, the load exerted on the actuator 14 during operation of the structural system 22. More specifically, the load factor parameters do not include values of actual sensed and measured load exerted on the actuator 14, but rather include values measured by the MCMS 26 that effect the actual resulting load exerted on the actuator 14. Thus, the actuator efficiency module 30 utilizes the load factor parameters to generate a mathematically estimated, non-actual, actuator load that is not based on actual measurements from dedicated force sensors of the load exerted on the actuator 14 by various forces imparted on the structural component 18. For example, in various embodiments the load factor parameters include such data as an amount of gravitational force acting on the component 18, a speed at which the structural system 22 is moving, if the structural system is moving, and/or an amount of surface deflection of component 18 operatively connected the actuator 14. In an exemplary embodiment wherein the structural system 22 is a mobile platform, the load factor parameters can include such data as an amount of gravitational force acting on a mobile platform control surface, a speed at which the mobile platform is moving, and/or an amount of surface deflection of a mobile platform control surface operatively connected the actuator 14. In a further exemplary embodiment, the mobile platform can comprise an aircraft such that the load factor parameters can include such data as an angle of attack, a speed at which the aircraft is moving relative to the speed of sound (Mach number), dynamic pressure, i.e., the difference between the total pressure and the static pressure, and/or an amount of surface deflection of an aircraft control surface operatively connected the actuator 14. As described further below, the virtual actuator load module 34 generates the VALV utilizing surface load, i.e., actuator 14 load, data previously compiled using surface load modeling. The surface load modeling computes loads exerted on the actuator 14 by forces or loads exerted on the surface of the component 18 using simulation testing. For example, if the component 18 was a flight control surface of an aircraft, the surface load model would compute loads exerted on the actuator 14 using wind tunnel and flight-testing that utilizes aerodynamic data acquired by the aircraft to estimate the load applied to the actuator 14. Accordingly, the utilization of the previous compiled surface load data during execution of the virtual actuator load module 34 eliminates the need for a dedicated force sensor to be added to the actuator 14. In various embodiments, the actuator efficiency module 30 additionally includes a virtual actuator output force module or routine 38 that utilizes the various measured operational control values of the actuator 14 to generate the VOFV. More specifically, the MCMS 26 sends position commands to an actuator controller 40 that controls the operation of the actuator 14 to move the component 18 to a desired position. Particularly, in response to the position command, the actuator controller 40 controls the operation of a drive motor 42 (shown in FIG. 1) included in the actuator 14 that operates to move an output ram connected to the component 18 to impart movement of the component 18. In various other embodiments, the MCMS 26 can send other control commands to control the operation of the drive motor 42, such as velocity commands, accelerations commands and/or current commands, such as those used in an error based closed loop control scheme. As described further below, during operation of the actuator 14, the actuator controller 40 measures the operational control values and inputs the values to the actuator efficiency module 30. Execution of the virtual actuator output force module 38 generates the VOFV based on the input operational control values. In various embodiments, the operational control values include such data as a pulse width modulation (PWM) signals input to the drive motor 42, a rotational speed of the motor 42 and an applied voltage to the motor 42. The actuator efficiency module 30 further includes a virtual efficiency calculation module or routine 46 that receives as input the VALV and the VOFV. Utilizing the VALV and the VOFV, the virtual efficiency calculation module 46 generates an approximate virtual torque efficiency 48 of the actuator 14. For example, execution of the virtual efficiency calculation module 46 divides the VALV (the dividend) by the VOFV (the divisor) to generate a quotient representative of the virtual torque efficiency of the actuator. In various embodiments, the actuator efficiency module 30 further includes a smoothing and/or filtering module or routine 50 that modifies the approximate virtual torque efficiency 48 generated by the virtual efficiency calculation module 46 to compensate for aiding and/or resisting force that can be exerted on the component 18. For example, air flow across the component 18 can increase or decrease the load imparted on the component 18 and thereby aid or resist the movement imparted by the drive motor 42 on the component 18. Filtering or smoothing the approximate virtual torque efficiency 48 results in the smoothing/filtering module 50 outputting the virtual torque efficiency (VTE) 32. As described above, the actuator efficiency module 30 repeatedly calculates the VTE 32 in accordance with a desired frequency, e.g., 100 Hz or 100 times per second, as the measured load factor parameters and actuator operational control values change in response to changing operational and environmental conditions of the structural system change. In various embodiments, the plurality of VTE data is output from the actuator efficiency module 30 and stored in any suitable electronic storage or memory device. For example, in various implementations the plurality of VTE data is output to the MCMS 26 and stored in a database within data storage device (not shown) of the MCMS 26. Subsequently, the VTE data can be analyzed via the MCMS 26 or transmitted, via wired or wireless transmission, to a remote computer-based system for analysis. Therefore, the VTE data can be tracked and analyzed to track trends and/or determine the reliability status of the actuator 14 during the life of the actuator 14 to identify projected points of failure, and provide an indicator of when to replace or repair the actuator 14 prior to failure. Referring now to FIG. 3, in various embodiments, the virtual actuator load module 34 includes a hinge moment coefficient lookup table 54, a hinge moment module 58, a mechanical advantage module 62 an other effects module 66 and a summer 70. The virtual actuator load module 34 receives the load factor parameters, e.g., gravitational force, speed and surface deflection, and inputs the load factor parameters to the hinge moment coefficient lookup table 54. The hinge moment coefficient lookup table 54 includes the previously compiled surface load model calculations described above. The hinge moment coefficient lookup table 54 generates a hinge moment coefficient based on the load factor parameters and data identifying the particular structural system 22 in which the actuator 14 is included, and specific structural and operational characteristics of the particular structural system 22. The structural system identification and characteristic data can be hard coded into the hinge moment coefficient lookup table 54 or received as inputs from a remote source, e.g., the MCMS 26. The hinge moment coefficient table 54 takes into consideration the load/force effects the structural system identification and characteristic data may have on the load/force exerted on the component 18. That is, utilizing the structural system identification and characteristic data, the hinge moment lookup table can consider the effects that other structural system surfaces adjacent the component 18 may have on the load/force exerted on the component 18. For example, the hinge moment lookup table 54 can take into consideration the aerodynamic influences that adjacent surfaces of the component 18 can have in the surface load of the component 18. Then, based on the structural system identification and characteristic data and the load factor parameter inputs, the hinge moment coefficient table 54 generates a hinge moment coefficient (CHM) for the component 18 that is input to the hinge moment module 58. The hinge moment module 58 utilizes the hinge moment coefficient to generate a hinge moment value, i.e., the amount of torque about a hinge line of the component 18. In various embodiments, the hinge moment (HM) is generated using the equation HM=CHMqbarSREF*LREF, wherein qbar is equal to dynamic pressure on the surface of the component 18, SREF is equal to surface area of the component 18 and LREF is equal to the distance the center of pressure or force on the component 18 is from the hinge line of the component 18. The hinge moment HM is output to the mechanical advantage module 62 that can also receive as an input the surface deflection value. The mechanical advantage module 62 adds the hinge moment HM to the product of the surface deflection and the effective moment arm between the actuator 14 and the component 18 it is driving. The other effects module 66 multiplies the surface deflection by other loads on the component 18 surface, such as friction with a linkage mechanism between the actuator output ram and the component 18, and/or spring loads created along the hinge line of the component 18 resulting from the particular structural design configuration of the component 18. The outputs of the mechanical advantage module 62 and the other effects module 66 are added at summer 70 to generate the VALV output from the virtual actuator load module 34. Referring now to FIG. 4, in various embodiments, the virtual actuator output force module 38 includes an actuator motor analysis module 74, a torque compensation module 78 and a summer 82. The virtual actuator output force module 38 receives the actuator operational control values, e.g., the rotational velocity of the drive motor 42, the PWM signal input to the drive motor 42, and the applied voltage to the drive motor 42, and inputs the values to the actuator motor analysis module 74. The PWM is generally derived from the error between the position command from the MCMS 26 and the actuator position feedback to the actuator controller 40. The motor velocity, e.g., rotational speed, and the applied or source voltage are input to the actuator motor analysis module 74 from the actuator controller 40. In various embodiments, the source voltage can be considered constant if long term voltage variations are small, which is common in typical mobile platforms, e.g., aircraft. The actuator motor analysis module 74 utilizes the actuator operational control values to perform motor modeling operations to generate a commanded motor torque value output to the summer 82. In various embodiments, the actuator motor analysis module 74 performs motor modeling operations in accordance with the block diagram shown in FIG. 4, wherein Ke equals a back EMF coefficient of the drive motor 42, Rm equals electrical resistance of the drive motor 42 and Kt equals a torque coefficient of the drive motor 42. Additionally, the virtual actuator output force module 38 accounts for free wheeling of the drive motor 42. The summer 82 applies the output of the torque compensation module 78 to the commanded motor torque output from the actuator motor analysis module 74 to account for known electrical, mechanical and acceleration related losses of the drive motor 42. In various embodiments, these losses are computed in accordance with the block diagram illustrated in FIG. 5, wherein Kd equals a viscous drag torque coefficient of the drive motor 42, Ct is Coulomb friction torque of the drive motor 42 and Ki equals a inertia coefficient of the drive motor 42. In various other embodiments, computation of such losses includes consideration of gear efficiency losses that can vary due to drive motor 42 speed and load. Inclusion of the gear efficiency losses in the calculation of the VOFV can be implemented in the form of a lookup table utilizing drive motor 42 speed and estimated load input and outputting a torque value that will be subtracted from the electrical torque output of the motor to generate the output of the torque compensation module 78. In various implementations, the torque compensation module 78 includes an Eddy current losses module 86 to compensate for losses that result from oscillating currents in the drive motor 42. The output of the torque compensation module is a torque value input to the summer 82 of the virtual actuator output force module 38 to generate the VOFV. Referring now to FIG. 6, in various embodiments, the virtual efficiency calculator module 46 generates the approximate virtual torque efficiency in accordance with the block diagram illustrated in FIG. 6, wherein Kr equals a gear ratio coefficient for the actuator 14 based on the ratio between drive motor 42 rotation and linear displacement of the output ram, is a logic signal indicative of whether the actuator 14 is under an aiding or resisting load, and 1/u inverts the output of a summer. Since the actuator efficiency monitor module 30 is intended to be a real time monitor, the loads exerted on the actuator 14 by the surface loads on the component 18 can frequently cross zero. The non-zero blocks are adapted to prevent division by zero within the virtual efficiency calculation module 46. Thus, the outputs of the non-zero blocks will always be a negative or positive value. Additionally, in various embodiments, the filtering/smoothing module 50 receives the output of the virtual efficiency calculator module 46 and generates the VTE in accordance with the block diagram illustrated in FIG. 6. The logic signal output from the block of the virtual efficiency calculation block that is indicative of whether the actuator 14 is under an aiding or resisting load, is input to a switch 1 block of the filtering/smoothing module 50. In response to the logic signal the switch 1 switches the filtering/smoothing module 50 between a resistive load VTE calculation mode and an aiding load VTE calculation. When in the resistive load VTE calculation mode, the filtering/smoothing module 50 outputs a reverse drive VTE. Conversely, when in the aiding load VTE calculation mode, the filtering/smoothing module 50 outputs a forward drive VTE. In various embodiments, the filtering/smoothing module 50 a validity tester module 52 and a discrete filter 53. The validity tester module 52 is used to limit the calculation of efficiency to only the range of input data where validation testing was conducted or where the most reliable data is produced. As an example, despite best efforts to accurately model the system, efficiency data may be erratic at high or low velocities and loads. The discrete filter 53 is simply a point moving average, e.g., a 64 point moving average. For example, the discrete filter 53 could be, a low pass filter, weighted moving average filter, or any mathematical method intended to eliminate any unintended variation due to noise in the data and to smooth the output signal such that the rate of change of the output signal to real failure events matches the detection time requirements of the structural system 22 the monitoring system 10 is used in. For example, if a 20% change in efficiency must be detected in 10 second, the filter must be set up to provide a 20% change in output signal over less than 10 seconds. Therefore, in various embodiments, the present invention provides an actuator efficiency monitoring system that uses data readily available to the MCMS 26 to monitor and compare the virtual actuator load value to the virtual output force value. The comparison is then utilized to calculate the virtual torque efficiency of the actuator 14. Simple calculation methods are implemented that simplify and minimize computation requirements. Accordingly, the actuator efficiency monitoring module 30 provides degradation status to mobile platform personal, e.g., mobile platform operators and maintenance personal, thereby providing time to plan replacement or repair of the actuator 14. While various preferred embodiments have been described, those skilled in the art will recognize modifications or variations which might be made without departing from the inventive concept. The examples illustrate the invention and are not intended to limit it. Therefore, the description and claims should be interpreted liberally with only such limitation as is necessary in view of the pertinent prior art.
	claims	1. A container inspection equipment with the cobalt-60 γ-ray source or the cesium-137 γ-ray source and a cesium iodide or cadmium tungstate detector, comprising:a γ-ray source and a cask for shielding the source;a front collimator and a rear collimator;a detector and the related electronic circuit;a signal and image processing system; anda container trailer system and an automatic control system, wherein:the radiation source is a cobalt-60 γ-ray source or a cesium-137 γ-ray source;the detector is a cesium iodide or cadmium tungstate array detector;the cobalt-60 γ-ray source or the cesium-137 γ-ray source is equipped with a beam shutter configured to automatically open and close, the beam shutter is connected with the cask of the γ-ray source;the cesium iodide or cadmium tungstate array detector is a strip array constituted of blocks in series arrangement consisting cesium iodide or cadmium tungstate scintillator crystals each coupled to a silicon photodiode and an electrical circuit;the cask of the cobalt-60 γ-ray source or the cesium-137 γ-ray source, the beam shutter, and the front collimator are fixed on a first common chassis that is placed in a source room;the rear collimator, the cesium iodide or cadmium tungstate array detector and a radiation catcher are fixed on a second common chassis that is placed in a detector room; andbetween the source room and the detector room is a container inspection tunnel. 2. The container inspection equipment of claim 1, wherein the activity of the cobalt-60 γ-ray source is ≦20.35 TBq. 3. The container inspection equipment of claim 1, wherein the cask of the cobalt-60 γ-ray source or the cesium-137 γ-ray source consists of a tungsten alloy semi-sphere and a lead semi-sphere, being enveloped by a stainless steel case to form an integrated cask. 4. The container inspection equipment of claim 3, wherein the beam shutter is a swing type iron shutter, the shutter is opened or closed using an electromagnetic driver and a restoring spring, the open or close duration is less than 0.3 second, the beam shutter is connected with the tungsten alloy semi-sphere of the cask, a collimating slit between them is accurately aligned with a slit of the front collimator, and the slit width is 6˜8 mm. 5. The container inspection equipment of claim 4, wherein the front and the rear collimators are made of iron, lead and the alloys thereof, in the shape of a single dog leg line, the width of the slit is 6˜8 mm. 6. The container inspection equipment of claim 1, wherein the cesium iodide or cadmium tungstate array detector is a strip array constituted of blocks in series arrangement in the vertical direction consisting plurality of cesium iodide or cadmium tungstate scintillator crystals each coupled to a silicon photodiode and an electrical circuit. 7. The container inspection equipment of claim 1, wherein the cross section of the scintillation crystal is a strip of 10˜50 mm2, the length is ≦8cm. 8. The container inspection equipment of claim 1, wherein the container trailer system includes a detection trolley for carrying a container truck, a frequency control drive motor, a control system, a rail and a support rail beam. 9. The container inspection equipment of claim 1, wherein the signal and image processing system uses digital circuit and microcomputer and is located in a master control and image processing room which is remote from the cobalt-60 γ-ray source or the cesium-137 γ-ray source and the inspection tunnel. 10. The container inspection equipment of claim 1, wherein the automatic control system includes a master computer, programmable logic control, radiation dose monitoring, and position, temperature, and humidity sensors, and closed circuit TV for surveillance.
	description	This application is a Continuation Application of PCT Application No. PCT/JP2012/080966, filed Nov. 29, 2012 and based upon and claiming the benefit of priority from Japanese Patent Application No. 2011-263791, filed Dec. 1, 2011, the entire contents of all of which are incorporated herein by reference. Embodiments described herein relate generally to an X-ray computed tomography apparatus. Reciprocal helical scanning is recently available as one of the scanning schemes using an X-ray computed tomography apparatus (to be referred to as an X-ray CT apparatus hereinafter). Reciprocal helical scanning is an imaging technique of continuously reciprocating the top while continuously rotating the X-ray tube on a circular orbit centered on an object to be examined. With regard to the reciprocal movement of the top, imaging along a forward path will be referred to as forward scanning hereinafter. With regard to the reciprocal movement of the top, imaging along a backward path will be referred to as backward scanning. According to reciprocal helical scanning, the X-ray tube (or the X-ray detector) traces a locus in a helical form (to be referred to as a helical locus hereinafter) with respect to an object. This will obtain a tomographic image with excellent continuity in a wide range. For example, reciprocal helical scanning on an object injected with a contrast medium is used to analyze hemodynamics (perfusion). Conventional reciprocal helical scanning, however, has the following problems. First, the object is not imaged during a returning process from forward (backward) scanning to backward (forward) scanning, i.e., an acceleration/deceleration process of the top (for example, FIG. 19). An imaging wait time during an acceleration/deceleration process of the top degrades the temporal resolution in perfusion analysis. Second, X-rays are emitted when the top reaches a constant velocity while the rotating frame on which the X-ray tube and the X-ray detector are mounted is rotated in advance at a predetermined angular velocity. For this reason, different helical loci are sometimes traced in different forward (backward) scans (for example, FIG. 20). The differences between helical loci in different forward (backward) scans cause differences in image quality (to be referred to as image quality differences hereinafter) concerning the same imaging position in the object. If the temporal resolution is low and image quality differences occur at the same imaging position, perfusion analysis sometimes becomes inaccurate. In general, according to one embodiment, an X-ray computed tomography apparatus includes an X-ray tube, an X-ray detector, a top, a rotation driving unit, a movement driving unit, and a scan control unit. The X-ray tube generates X-rays. The X-ray detector detects the X-rays generated from the X-ray tube and transmitted through an object. The object is placed on the top. The rotation driving unit rotates a rotating frame around the object, wherein the X-ray tube and the X-ray detector are mounted on the rotating frame. The movement driving unit relatively reciprocates the rotating frame and the top over a plurality of times along a long-axis direction of the top. The scan control unit controls the movement driving unit in relative reciprocal movement of the rotating frame and the top such that a plurality of moving loci of the X-ray tube corresponding to a plurality of respective forward movements are matched with each other and a plurality of moving loci of the X-ray tube corresponding to a plurality of respective backward movements are matched with each other. An X-ray computed tomography apparatus (to be referred to as an X-ray CT apparatus hereinafter) according to an embodiment will be described below with reference the accompanying drawing. X-ray CT apparatuses include various types of apparatuses, e.g., a rotate/rotate-type apparatus in which an X-ray tube and an X-ray detector rotate together around an object, and a stationary/rotate-type apparatus in which many X-ray detection elements are arrayed in the form of a ring, and only an X-ray tube rotates around an object. This embodiment can be applied to either type. Recently, with advances toward the commercialization of a so-called multi-tube type X-ray computed tomography apparatus having a plurality of pairs of X-ray tubes and X-ray detectors mounted on a rotating frame, related techniques have been developed. This embodiment can be applied to both a conventional single-tube type X-ray computed tomography apparatus and a multi-tube type X-ray computed tomography apparatus. The single-tube, rotate-rotate-type X-ray computed tomography apparatus will be exemplified here. Note that the same reference numerals denote constituent elements having almost the same functions and arrangements in the following description, and a repetitive description will be made only when required. FIG. 1 is a view showing the arrangement of an X-ray CT apparatus 100 according to this embodiment. As shown in FIG. 1, the X-ray CT apparatus 100 includes a gantry 10, a bed 20, and a console device 30. FIG. 2 is a sectional view showing an example of sections of the gantry 10 and bed 20 of the X-ray CT apparatus 100. The gantry 10 and the bed 20 are arranged in the manner exemplified by FIG. 2. An arrow shown in FIG. 2 indicates the body axis direction of an object P. A top 22 continuously reciprocates in the first direction (e.g., the forward direction) parallel to the body axis direction of the object P and the second direction (e.g., the backward direction) opposite to the first direction. As shown in FIGS. 1 and 2, an annular or disk-like rotating frame 15 is mounted on the gantry 10. The rotating frame 15 supports an X-ray tube 12 and an X-ray detector 13 so as to allow them to rotate around the rotation axis. The rotating frame 15 supports the X-ray tube 12 and the X-ray detector 13 so as to make them face each other through the object P. The rotating frame 15 is connected to a rotation driving unit 16. The rotation driving unit 16 continuously rotates the rotating frame 15 under the control of the control circuit 38 in the console device 30. The X-ray tube 12 and the X-ray detector 13, which are supported on the rotating frame 15, rotate around the rotation axis. The definitions of the axes according to this embodiment will be described with reference to FIG. 3. The Z-axis is defined as the rotation axis of the rotating frame 15. The Y-axis is defined as an axis connecting the X-ray focus of the X-ray tube 12 and the center of the X-ray detection surface of the X-ray detector 13. The Y-axis is perpendicular to the Z-axis. The X-axis is defined as an axis perpendicular to the Y- and Z-axes. In this manner, the XYZ orthogonal coordinate system forms a rotating coordinate system which rotates with the rotation of the X-ray tube 12. The X-ray tube 12 generates an X-ray cone beam upon receiving a high voltage applied from a high voltage generation unit 11. The high voltage generation unit 11 applies a high voltage to the X-ray tube 12 under the control of a scan control unit 36. The X-ray detector 13 detects the X-rays generated from the X-ray tube 12 and transmitted through the object P. The X-ray detector 13 generates a current signal corresponding to the intensity of the detected X-rays. It is preferable to use, as the X-ray detector 13, a type called a flat panel detector or multi-row detector. An X-ray detector of this type has a plurality of X-ray detection elements arrayed two-dimensionally. Assume that in the following description, a single X-ray detection element forms a single channel. For example, 100 X-ray detection elements are arrayed one-dimensionally along an arc direction (channel direction) with the X-ray focus being the center and the distance from the center to the center of the light-receiving unit of each X-ray detection element being the radius. The plurality of X-ray detection elements arrayed along the channel direction will be referred to as an X-ray detection element row. For example, 64 X-ray detection element rows are arrayed along the slice direction indicated by the Z-axis. A data acquisition unit (data acquisition system to be referred to as a DAS hereinafter) 14 is connected to the X-ray detector 13. As mechanisms of converting incident X-rays into electric charges, the following techniques are the mainstream: an indirect conversion type that converts X-rays into light through a phosphor such as a scintillator and converts the light into electric charges through photoelectric conversion elements such as photodiodes, and a direct conversion type that uses generation of electron-hole pairs in a semiconductor such as selenium by X-rays and migration of the electron-hole pairs to an electrode, i.e., a photoconductive phenomenon. As an X-ray detection element, either of these schemes can be used. The data acquisition unit 14 reads an electrical signal from the X-ray detector 13 for each channel under the control of the scan control unit 36. The data acquisition unit 14 amplifies the read signals. The data acquisition unit 14 generates projection data by converting the amplified electrical signals into digital signals. Note that the data acquisition unit 14 can also generate projection data by reading electrical signals from the X-ray detector 13 during a period in which no X-rays are emitted. The generated projection data is supplied to the console device 30 via a noncontact data transmission unit (not shown). The bed 20 is installed near the gantry 10. The bed 20 includes the top 22, a top support mechanism 23, and a top driving unit 21. The object P is placed on the top 22. The top support mechanism 23 supports the top 22 so as to allow it to reciprocate along the Z-axis. Typically, the top support mechanism 23 supports the top 22 so as to make the long axis of the top 22 parallel to the Z-axis. The top driving unit 21 drives the top 22 under the control of a driving control unit 38 of the console device 30 (to be described later). More specifically, the top driving unit 21 moves the top 22 at a constant velocity in a constant-velocity region set in an imaging range. The top driving unit 21 accelerates or decelerates the moving velocity of the top 22 in an acceleration/deceleration region in the imaging range. That is, the top driving unit 21 decelerates and stops the top 22 in a deceleration region. After the top 22 stops, the top driving unit 21 reverses the moving direction of the top 22. The top driving unit 21 accelerates the moving velocity of the top 22 in an acceleration region. Note that the gantry 10 may be moved at a constant velocity instead of the top 22. A gantry driving unit (not shown) moves the gantry 10 along the Z-axis. In addition, the gantry driving unit accelerates or decelerates the gantry 10 in the above acceleration/deceleration region. That is, the gantry driving unit decelerates and stops the gantry 10 in a deceleration region. After the gantry 10 stops, the gantry driving unit reverses the moving direction of the gantry 10. The gantry driving unit accelerates the moving velocity of the gantry 10 in an acceleration region. The console device 30 includes an input unit 31, a display unit 32, a system control unit 33, an image processing unit 34, an image data storage unit 35, a scan control unit 36, a velocity time change pattern storage unit 37, and the driving control unit 38. The input unit 31 includes input devices such as a mouse, keyboard, and touch panel. The input unit 31 inputs, to the X-ray CT apparatus 100, various kinds of commands, various kinds of information, and the like input by the operator via input devices. The display unit 32 is a display such as an LCD (Liquid Crystal Display). The display unit 32 displays a medical image stored in the image data storage unit 35 (to be described later), a GUI (Graphical User Interface) for accepting various kinds of instructions from the operator, and the like. The input unit 31 sets or inputs various kinds of scan conditions in reciprocal helical scanning in accordance with instructions input by the operator via input devices. Reciprocal helical scanning is an imaging technique of continuously reciprocating the top 22 while continuously rotating the X-ray tube 12 on a circular orbit centered on an object to be examined. Scan conditions include, for example, an imaging range for an object for which reciprocal helical scanning is executed, the position information of the imaging range, the velocity of the top 22 (to be referred to as the top velocity hereinafter) concerning reciprocal helical scanning, a helical pitch, a scan time, the rotational velocity of the rotating frame 15, and the distance of a constant-velocity interval of the top 22. Note that the input unit 31 may input a range, of the imaging range, in which the top 22 is moved at a constant velocity by operation by the operator via an input device. The input unit 31 may also input an angular velocity at which the rotating frame 15 is continuously rotated around the rotation axis in accordance with an instruction from the operator via an input device. Note that the scan control unit 36 (to be described later) may set an angular velocity in advance based on scan conditions. FIG. 4 is a view for explaining reciprocal helical scanning. According to reciprocal helical scanning, as exemplified by FIG. 4, the focus of the X-ray tube 12 (or the X-ray detector 13) traces a locus in a helical form (to be referred to as a helical locus hereinafter) with respect to the object P. As exemplified by FIG. 4, of the body axis direction of the object P, the direction of an arrow from the head of the object to the feet is defined as a Z direction. Imaging performed by moving the top 22 in the same direction as the Z direction will be referred to as forward scanning. Imaging performed by moving the top 22 in a direction opposite to the Z direction will be referred to as backward scanning. The arrow of “top IN” exemplified in FIG. 4 indicates a direction in which the top 22 is moved in forward scanning. The arrow of “top OUT” exemplified in FIG. 4 indicates a direction in which the top 22 is moved in backward scanning. The arrows of symbols a and b shown in FIG. 4 indicate the rotating direction of the X-ray tube 12. The system control unit 33 includes integrated circuits such as an ASIC (Application Specific Integrated Circuit) and FPGA (Field Programmable Gate Array) and electronic circuits such as a CPU (Central Processing Unit) and MPU (Micro Processing Unit). More specifically, the system control unit 33 controls the overall X-ray CT apparatus 100 by controlling the gantry 10, the bed 20, and each unit in the console device 30. For example, the system control unit 33 controls the scan control unit 36 to acquire projection data. The system control unit 33 controls the image processing unit 34 (to be described later) to reconstruct a medical image based on projection data. The system control unit 33 outputs the scan conditions input via the input unit 31 to the scan control unit 36. The image processing unit 34 executes various kinds of processes for the projection data generated by the data acquisition unit 14. More specifically, the image processing unit 34 executes preprocessing such as sensitivity correction for the projection data. The image processing unit 34 reconstructs a medical image based on the reconstruction conditions instructed from the system control unit 33. The image processing unit 34 stores the reconstructed medical image in the image data storage unit 35 (to be described later). In order to reconstruct an image, projection data corresponding to one rotation around an object, i.e., 360°, is required, or (180°+fan angle) projection data is required in the half scan method. This embodiment can be applied to either of these reconstruction schemes. The image data storage unit 35 includes semiconductor memory devices such as a RAM (Random Access Memory), ROM (Read Only Memory), and flash memory, a hard disk, and an optical disk. The image data storage unit 35 stores the medical image reconstructed by the image processing unit 34. The velocity time change pattern storage unit 37 stores a plurality of time change patterns (patterns of acceleration changes) concerning top velocities. FIGS. 5, 6, and 7 each show an example of the relationship between the moving time of the top and the moving velocity of the top (to be referred to as a velocity time change pattern hereinafter) in the forward direction in reciprocal movement of the top 22. FIG. 5 shows a velocity time change pattern associated with values of an imaging range and uniform velocity of the top which are input by the operator. FIG. 7 shows a velocity time change pattern in the case of an imaging range smaller than that in FIG. 5. FIG. 6 shows a velocity time change pattern in the case of an imaging range smaller than that in FIG. 5 but larger than that in FIG. 7. A time interval (A) in FIGS. 5, 6, and 7 indicates a period during which the acceleration of the top 22 increases. A time interval (B) in FIGS. 5 and 6 indicates a period during which the acceleration of the top 22 is constant. A time interval (C) in FIGS. 5 and 7 indicates a period during which the acceleration of the top 22 decreases. The time intervals (A), (B), and (C) correspond to an acceleration region at a turnaround portion of reciprocal movement in the imaging range. A time interval (D) in FIG. 5 indicates a period during which the top velocity is constant. The time interval (D) corresponds to a constant-velocity region in the imaging range. A time interval (E) in FIGS. 5, 6, and 7 indicates a period during which the deceleration of the top 22 increases. A time interval (F) in FIGS. 5 and 6 indicates a period during which the deceleration of the top 22 is constant. A time interval (G) in FIGS. 5 and 7 indicates a period during which the deceleration of the top 22 decreases. The time intervals (E), (F), and (G) correspond to a deceleration region at a turnaround portion of reciprocal movement in the imaging range. As indicated by (A), (C), (E), and (G) in FIG. 5, it is possible to reduce the force exerting on the object placed on the top 22 by smoothly changing acceleration while performing acceleration and deceleration. Note that it is possible to use any type of velocity time change pattern as long as it is a top velocity time change pattern which is set to make the time required for one reciprocal movement of the top 22 become an integer multiple of the time taken to cause the rotating frame 15 to make one rotation around the rotation axis. The scan control unit 36 includes integrated circuits such as an ASIC and FPGA and electronic circuits such as a CPU and MPU. The scan control unit 36 controls the high voltage generation unit 11, the data acquisition unit 14, and the driving control unit 38 (to be described later) based on the scan conditions instructed from the system control unit 33. For example, the scan control unit 36 reads out a top velocity time change pattern from the velocity time change pattern storage unit 37 based on scan conditions. The scan control unit 36 outputs the readout top velocity time change pattern and scan conditions to the driving control unit 38. The scan control unit 36 outputs an instruction to rotate the rotating frame 15 to the driving control unit 38 based on the scan conditions. The scan control unit 36 controls the high voltage generation unit 11 to reduce radiation exposure on the object. For example, the scan control unit 36 controls the high voltage generation unit 11 to change X-ray intensities in the direction along the Z-axis (to be referred to as the Z direction hereinafter) and the directions along the X- and Y-axes (to be referred to as the X and Y directions hereinafter) based on a scanogram acquired in advance. The scan control unit 36 controls the data acquisition unit 14 to acquire projection data. More specifically, the scan control unit 36 controls the data acquisition unit 14 to set the same number of views required to reconstruct a tomographic image at any Z positions in each of forward scanning and backward scanning. Note that the scan control unit 36 can also calculate the total rotational angle of the top 22 in a constant-velocity interval based on the distance of the contrast-velocity interval and the rotational velocity of the rotating frame 15 which are set or input via the input unit 31. This allows the scan control unit 36 to calculate the rotational angle of the X-ray tube 12 at the end position in the constant-velocity interval based on the set scan conditions. The scan control unit 36 can also set the rotational angle of the X-ray tube 12 at a scan start position on a forward path in a constant-velocity interval of the top 22 to a predetermined position. The scan control unit 36 can calculate the rotational angle of the X-ray tube 12 at the end position in a constant-velocity interval of the top 22 on a backward path in a constant-velocity interval in the same manner as described above. These allow the scan control unit 36 to decide the relationship (to be referred to as the helical locus hereinafter) between the rotational angle of the X-ray tube 12 and the position of the top 22 in reciprocal helical scanning. In addition, the scan control unit 36 can control the driving control unit 38 to make the helical locus of the X-ray tube on a forward path of the top 22 in a constant-velocity interval coincide with that on a backward path of the top 22. The scan control unit 36 can also decide the velocity of the top 22 or gantry 10 in forward scanning and backward scanning based on the imaging range information for an object which is input by the input unit 31. Note that the scan control unit 36 can also decide the acceleration of the top 22 or gantry 10 at a turnaround portion (to be referred to as the first turnaround portion) from forward scanning to backward scanning and at a turnaround portion (to be referred to as the second turnaround portion hereinafter) from backward scanning to forward scanning based on the imaging range information. The scan control unit 36 can also decide the velocity of the top 22 or gantry 10 in a constant-velocity interval in each of forward scanning and backward scanning based on the imaging range information. In addition, the scan control unit 36 can control the X-ray tube 12 and the X-ray detector 13 to acquire projection data by irradiating an object with X-rays in an acceleration/deceleration interval of the top 22 or gantry 10 at the first and second turnaround portions. Note that the scan control unit 36 can also control the driving control unit 38 to make the rotation end angle of a helical locus at the end position in a forward constant-velocity interval coincide with the rotation start angle of a helical locus at the start position in a backward constant-velocity interval. In addition, the scan control unit 36 may select a velocity pattern in an acceleration/deceleration interval of the top 22 so as to match the rotation end angle of a helical locus at the end position in a forward constant-velocity interval with the rotation start angle of a helical locus at the start position in a backward constant-velocity interval. For example, to match the rotation end angle with the rotation start angle, the scan control unit 36 selects a velocity pattern that satisfies the following relationship. That is, the rotational angle at the time of deceleration (or acceleration) in an acceleration/deceleration interval is equal to ((rotation start angle−rotation end angle)+360°×n rotations)/2. The driving control unit 38 controls the rotation driving unit 16 and the top driving unit 21 based on the scan conditions output from the scan control unit 36. The driving control unit 38 adjusts a velocity time change pattern based on the imaging range for the object. More specifically, the driving control unit 38 adjusts a velocity time change pattern such that the time required for each of a plurality of reciprocal movements of the top 22 becomes an integer multiple of the time taken to cause the rotating frame to make one rotation around the rotation axis. For example, the driving control unit 38 adjusts at least one of an acceleration change pattern of a velocity time change pattern, a uniform-velocity time, the magnitude of velocity, and the magnitude of acceleration. The driving control unit 38 controls the top driving unit 21 in accordance with the adjusted velocity time change pattern. The driving control unit 38 controls the rotation driving unit 16 to continuously rotate the rotating frame 15. The driving control unit 38 controls the top driving unit 21 so as to match top velocity time change patterns with each other in the respective reciprocal movements. The driving control unit 38 controls the top driving unit 21 so as to null the wait time at the turnaround time point in reciprocal movement of the top 22. Note that the driving control unit 38 may control the top driving unit 21 to change and adjust the acceleration so as to almost null the wait time at the turnaround time point in reciprocal movement of the top 22. FIG. 8 is a graph showing an example of the relationship between the scan position and the top velocity in one reciprocal movement in reciprocal helical scanning. The driving control unit 38 controls the top driving unit 21 to match top velocities with each other in association with the scan position and the scan direction in the respective reciprocal movements, as shown in FIG. 8. Note that FIG. 9 is a graph showing an example of the relationship between the scan position and the top velocity in reciprocal helical scanning without any imaging wait time. Note that the driving control unit 38 controls the top driving unit 21 to almost null the imaging wait time (the stop time at a turnaround point) during acceleration/deceleration of the top 22 in each of a plurality of reciprocal movements, as shown in FIG. 9. In addition, the driving control unit 38 can stop the top 22 at a turnaround point from a forward path to a backward path in each of a plurality of reciprocal movements and execute (180°+fan angle) or 360° imaging under the control of the scan control unit 36. This makes it possible to increase the range of image reconstruction larger than the reciprocal moving range. At this time, the driving control unit 38 controls the top driving unit 21 so as to stop the top 22 during the execution of 360° or (180°+fan angle) imaging using the rotating frame 15 at a turnaround time point. FIG. 10 is a graph showing the relationship between the number of rotations of the rotating frame 15 (or the X-ray tube 12 or the X-ray detector 13) and the position of the top in each moving direction of the top. “Top IN” and “top OUT” in FIG. 10 respectively correspond to “top IN” and “top OUT” in FIG. 4. In “top IN” (forward scanning), the driving control unit 38 controls the top driving unit 21 so as to stop the top 22 until the rotating frame 15 completes one-rotation (360°) imaging. The driving control unit 38 controls the top driving unit 21 so as to accelerate the top 22 upon performing one-rotation (360°) imaging. The driving control unit 38 controls the top driving unit 21 so as to stop the top 22 when the number of rotations of the rotating frame 15 reaches 10. In “top OUT” (backward scanning), the driving control unit 38 controls the top driving unit 21 so as to stop top 22 until the rotating frame 15 completes one-rotation) (360°) imaging. The driving control unit 38 controls the top driving unit 21 so as to accelerate the top 22 upon performing one-rotation (360°) imaging. The driving control unit 38 controls the top driving unit 21 so as to stop the top 22 when the number of rotations of the rotating frame 15 reaches 10. The driving control unit 38 repeats the above control for the top driving unit 21. FIG. 11 is a graph showing an example of a helical locus in “top IN” and a helical locus in “top OUT” when the driving control unit 38 controls the top driving unit 21 in the case of FIG. 10. The driving control unit 38 controls the top driving unit 21 so as to match helical loci with respect to the object in “top IN” and “top OUT” in reciprocal helical scanning. In other words, the driving control unit 38 performs control to match helical loci with each other in the respective reciprocal movements like the first reciprocal movement and the second reciprocal movement. That is, a plurality of helical loci respectively corresponding to a plurality of respective forward movements in a plurality of reciprocal movements almost are matched with each other. In addition, a plurality of helical loci respectively corresponding to a plurality of respective backward movements in a plurality reciprocal movements almost are matched with each other. Note that the rotational angle of the X-ray tube 12 at the relative movement start time in a forward path may be equal to the rotational angle of the X-ray tube 12 at the relative movement start time in a backward path or may differ from it by 180°. FIG. 12 is a view showing an example of the positional relationship between the X-ray tube 12, the X-ray detector 13, and the imaging range in reciprocal helical scanning associated with FIGS. 10 and 11. “FOV” in FIG. 12 stands for a field of view. The hatched region defined by “FOV” and the imaging range is a scan region. The driving control unit 38 controls the top driving unit 21 so as to stop the top 22 until the rotating frame 15 rotates through 360° at a turnaround point from forward scanning to backward scanning. This makes it possible to reconstruct an image at each of turnaround points (the two ends of the imaging range) by using projection data corresponding to one rotation of the rotating frame 15. This can obtain an imaging range larger than the reciprocal moving range of the top 22, as shown in FIG. 12. FIG. 13 is a graph showing an example of the time dependencies on the rotational angle of the X-ray tube 12, the top position, and the top velocity under the control of the driving control unit 38. For the sake of descriptive convenience, FIG. 13 shows a case in which the rotational angle of the X-ray tube 12 is used instead of the rotational angle of the rotating frame 15. When reciprocal helical scanning starts, the X-ray tube 12 makes one rotation around the Z-axis while the top 22 stops moving. The top 22 then moves along a forward direction. At this time, the X-ray tube 12 makes N rotations (N is a natural number) around the Z-axis at a constant angular velocity. The top 22 stops at a turnaround time point. While the top 22 stops moving, the X-ray tube 12 makes one rotation around the Z-axis. Subsequently, the top 22 moves along a backward direction. At this time, the X-ray tube 12 makes N rotations (N is a natural number) around the Z-axis at a constant angular velocity. The top 22 stops at a turnaround time point. While the top 22 stops moving, the X-ray tube 12 makes one rotation around the Z-axis. Subsequently, the above operation repeats. A function of implementing an improvement in temporal resolution in reciprocal helical scanning and a reduction in helical locus difference will be described below. FIG. 14 is a flowchart showing an example of a procedure for reciprocal helical scanning. The operator inputs an imaging range for an object, the maximum value of the moving velocity of the top 22, and the number of reciprocal movements of the top 22 via the input unit 31 (step Sa1). The apparatus then decides a top velocity time change pattern (velocity time change pattern) based on the input imaging range and maximum value (step Sa2). At this time, the operator may select imaging corresponding to one rotation at a turnaround time point in reciprocal movement of the top 22. Note that the operator can set velocity control on the top 22 via the input unit 31. The apparatus reads out the decided velocity time change pattern from the velocity time change pattern storage unit 37 (step Sa3). The apparatus adjusts the readout velocity time change pattern based on the input imaging range (step Sa4). When the apparatus starts scanning (step Sa5), the top 22 reciprocally moves based on the adjusted velocity time change pattern (step Sa6). The apparatus repeats the processing in step Sa6 until the number of reciprocal movements of the top 22 becomes equal to the input number of reciprocal movements (step Sa7). When the number of reciprocal movements of the top 22 becomes equal to the input number of reciprocal movements, the apparatus stops scanning (step Sa8). (Modification) FIG. 15 is a view showing the arrangement of the X-ray CT apparatus 100 according to a modification of this embodiment. As shown in FIG. 15, the X-ray CT apparatus 100 includes the gantry 10, the bed 20, and the console device 30. A difference between the arrangement of this embodiment (FIG. 1) and the arrangement of this modification (FIG. 15) will be described. The modification includes an imaging range storage unit 39 and an imaging range setting unit 40 instead of the velocity time change pattern storage unit 37 of the embodiment. The imaging range storage unit 39 stores a plurality of discrete imaging ranges. Each of the plurality of imaging ranges is an imaging range in which the time required for one reciprocal movement of the top 22 becomes an integer multiple of the time taken to cause the rotating frame 15 to make one rotation around the rotation axis. In addition, each of the plurality of imaging ranges is an imaging range in which the stop time of the top at a turnaround time point in reciprocal movement of the top 22 becomes minimum (almost zero). The imaging range storage unit 39 stores top velocity time change patterns (velocity time change patterns) respectively corresponding to the plurality of discrete imaging ranges. Note that the imaging range storage unit 39 may store a plurality of velocity time change patterns in correspondence with the respective discrete imaging ranges. The imaging range setting unit 40 sets, as an imaging range in which reciprocal helical scanning is to be executed (to be referred to as an execution imaging range hereinafter), an imaging range, of the plurality of discrete imaging ranges, which is equal to the imaging range input via the input unit 31 (to be referred to as an input imaging range hereinafter) or the minimum imaging range of imaging ranges exceeding the input imaging range. FIG. 16 is a view showing an example of setting an imaging range for an object according to this modification. Referring to FIG. 16, an input imaging range 71 is input by dragging on, for example, the scanogram displayed on the display unit 32 with a mouse or the like of the input devices. At this time, the imaging range setting unit 40 sets, as execution imaging ranges, a plurality of discrete imaging ranges (“a” in FIG. 16), of the imaging ranges (“a”, “b”, “c”, “d”, and “e” in FIG. 16) stored in the imaging range storage unit 39, which exceed the input imaging range 71. FIG. 17 is a view showing an example of a setting window for an imaging range for an object according to this modification. Imaging regions such as a head region, chest region, and abdominal region shown in FIG. 17 are displayed in a pull-down menu. The operator selects a desired region (the head region in FIG. 17) of the imaging regions displayed in the pull-down menu via an input device. Subsequently, the discrete imaging ranges stored in the imaging range storage unit 39 are displayed in the pull-down menu (80, 82, 84, . . . , 160 in FIG. 17). The operator selects a desired imaging range (80 in FIG. 17) of the discrete imaging ranges displayed in the pull-down menu via an input device. A function of setting an execution imaging range will be described below. FIG. 18 is a flowchart showing an example of a procedure for setting an imaging range in reciprocal helical scanning according to this modification. The operator inputs an imaging range for an object concerning reciprocal helical scanning via an input device of the input unit 31 (step Sb1). If the imaging range storage unit 39 stores an imaging range equal to the input imaging range 71 (step Sb2), the apparatus reads out a velocity time change pattern corresponding to this imaging range from the imaging range storage unit 39 (step Sb3). The apparatus drives the top 22 based on the readout velocity time change pattern. If the imaging range storage unit 39 stores no imaging range equal to the input imaging range 71 (step Sb2), the apparatus sets, as an execution imaging range, the minimum imaging range of the plurality of discrete imaging ranges exceeding the input imaging range 71 (step Sb4). The apparatus reads out a velocity time change pattern corresponding to the set imaging range from the imaging range storage unit 39 (step Sb5). The apparatus drives the top 22 based on the readout velocity time change pattern. According to the arrangement described above, the following effects can be obtained. The X-ray computed tomography apparatus 100 according to this embodiment can reduce or null the imaging wait time at each turnaround time point in reciprocal movement of the top 22 in reciprocal helical scanning. This improves the temporal resolution. In addition, it is possible to match helical loci in reciprocal helical scanning with each other in forward scanning and backward scanning. This can equalize image quality in the respective scans. As described above, it is possible to improve the accuracy of perfusion analysis. In addition, setting discrete imaging ranges concerning reciprocal helical scanning can facilitate controlling the gantry 10 and the bed 20. This makes it possible to provide the inexpensive X-ray computed tomography apparatus 100. In addition, it is possible to perform imaging in a wider range by stopping the top 22 at the two ends of the moving range of the top 22 and executing 360° or (180°+fan angle) imaging. In addition, it is possible to reduce directional artifacts remaining in differences between forward paths and between backward paths. This can prevent deterioration in the accuracy of an analysis result on, for example, perfusion analysis. 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.
	claims	1. A scanning electron microscope (“SEM”) comprising:an electron gun for producing an electron beam directed toward a sample;a secondary electron (“SE”) detector for detecting secondary electrons reflected from the sample in response to the electron beam;a dual-layer shield disposed around and enclosing the SE detector, the shield comprising:a magnetic shielding lamina layer; anda metallic foil layer. 2. The SEM of claim 1 wherein the magnetic shielding lamina layer comprises a highly ferro-magnetic material. 3. The SEM of claim 1 wherein the metallic foil layer comprises a highly reflective conductor. 4. The SEM of claim 1 wherein the magnetic shielding lamina layer comprises a nickel-iron alloy. 5. The SEM of claim 1 wherein the magnetic shielding lamina layer comprises one of steel plate and platinum. 6. The SEM of claim 1 wherein the metallic foil layer comprises aluminum foil. 7. The SEM of claim 1 wherein the metallic foil comprises at least one of gold foil, copper foil, and silver foil. 8. The SEM of claim 1 wherein the shield comprises the first layer disposed over the second layer. 9. The SEM of claim 1 wherein the shield comprises the second layer disposed over the first layer. 10. An apparatus for shielding a secondary electron (“SE”) detector of a scanning electron microscope (“SEM”) from effects of electromagnetic interference (“EMI”), the apparatus comprising:a dual-layer shield disposed around and enclosing the SE detector, the shield comprising:a first layer comprising a magnetic shielding lamina; anda second layer comprising a metallic foil. 11. The apparatus of claim 10 wherein the magnetic shielding lamina comprises a nickel-iron alloy. 12. The apparatus of claim 10 wherein the magnetic shielding lamina comprises one of steel plate and platinum. 13. The apparatus of claim 10 wherein the metallic foil comprises aluminum foil. 14. The apparatus of claim 10 wherein the metallic foil layer comprises at least one of gold foil, copper foil, and silver foil. 15. The apparatus of claim 10 wherein the shield comprises the magnetic shielding lamina layer disposed over the metallic foil layer. 16. The apparatus of claim 10 wherein the shield comprises the metallic foil layer disposed over the magnetic shielding lamina layer. 17. A method of shielding a secondary electron (“SE”) detector of a scanning electron microscope (“SEM”) from effects of electromagnetic interference (“EMI”), the method comprising:providing a first shielding layer around the SE detector; andproviding a second shielding layer over the first shielding layer. 18. The method of claim 17 wherein one of the first and second layers comprises a metallic foil layer and the other one of the first and second layers comprises a magnetic shielding lamina. 19. The method of claim 18 wherein the metallic foil layer comprises one of aluminum, copper, gold, and silver. 20. The method of claim 18 wherein the magnetic shielding lamina comprises one of a nickel-iron alloy, steel plate, and platinum.
	summary
	claims	1. In a charged-particle-beam microlithography apparatus that irradiates a pattern-defining reticle with a charged particle beam passing through an illumination-optical system such that particles of the beam pass through the reticle, and that passes the beam transmitted through the reticle through a projection-optical system so as to projection-transfer the reticle pattern onto a wafer, a system for producing a hollow beam, comprising: a scattering aperture situated at a crossover-image plane of the illumination-optical system, the scattering aperture being configured as one or more openings defined in a layer of beam-scattering material, the openings being arranged to have, collectively, a first radius equal to a radius of a central region of the scattering aperture and a second radius greater than the first radius so as to produce a hollow beam downstream of the scattering aperture as the beam passes through the openings; and a blocking aperture situated between the scattering aperture and the reticle, the blocking aperture being configured as a plate defining a central opening, the plate being configured to absorb charged particles of the beam that were scattered by passage through the scattering aperture. 2. The system of claim 1 , further comprising a current-limiting aperture upstream of the scattering aperture, the current-limiting aperture being configured to pre-absorb particles of the charged particle beam at an edge of the beam. claim 1 3. The system of claim 1 , further comprising a scattered-particle-absorbing aperture, configured as a particle-absorbing plate defining a central void, and configured to be situated between the blocking aperture and the reticle. claim 1 4. A charged-particle-beam microlithography apparatus comprising the system of claim 1 . claim 1 5. A method for manufacturing a semiconductor device, comprising performing projection-transfer of a pattern, defined by a reticle, onto a wafer using a charged-particle-beam microlithography apparatus as recited in claim 4 . claim 4 6. The system of claim 1 , wherein the scattering aperture is configured as voids defined in a beam-scattering plate. claim 1 7. The system of claim 6 , wherein the voids collectively define a profile that is substantially ring-shaped. claim 6 8. The system of claim 1 , wherein the scattering aperture is configured as an opening in a layer of charged-particle-beam-scattering material on a relatively charged-particle-beam-transmissive membrane. claim 1 9. The system of claim 8 , wherein the opening is ring-shaped. claim 8
	abstract	The present disclosure relates to a method and a system for generating low-energy electrons in a biological material. The biological material is held in position by a support. Laser beam pulses are directed by a focusing mechanism toward a region of interest within the biological material. This generates filaments of low-energy electrons within the region of interest. The method and system may be used for radiotherapy, radiochemistry, sterilization, nanoparticle coating, nanoparticle generation, and like uses.
	abstract	A scattered radiation collimator is disclosed for radiological radiation. In at least one embodiment, the scattered radiation collimator includes a multiplicity of absorber elements connected one behind the other in a collimation direction and at least two plate-like holding elements which are arranged substantially parallel with respect to one another and have absorber element holders for holding the absorber elements. In order to avoid erroneous positioning when transverse forces are acting, it is proposed in at least one embodiment, to connect the holding elements to each other by cross beams running along the end face of the absorber elements.
	abstract	Excitation light is split into two components with mutually orthogonal polarization. One component is fed clockwise and the other component is fed counterclockwise into a polarization maintaining loop. An optical conversion generation unit including two second-order nonlinear optical media disposed on opposite sides of a half-wave plate in the loop generates up-converted light from each excitation component by second harmonic generation, and generates down-converted light from the up-converted light by spontaneous parametric down conversion. A polarization manipulation unit manipulates the polarization direction of at least one of the excitation or down-converted components. The clockwise and counterclockwise components of the down-converted light are recombined and output as quantum entangled photon pairs having substantially the same wavelength as the excitation light. The optical components can be optimized for operation at this wavelength without the need to consider the shorter wavelength of the up-converted light.
046833790	summary	CROSS-REFERENCE TO RELATED CASES A sunlamp which emits radiation primarily in the UVA band of the ultraviolet range and in the visible range of the spectrum is disclosed in the commonly owned copending patent application Ser. No. 752,251 filed July 3, 1985. Reference should also be had to commonly owned U.S. Pat. Nos. 4,095,113, 4,106,083, 4,177,384, 4,194,125, 4,196,354, 4,287,554, 4,309,616 and 4,316,094. BACKGROUND OF THE INVENTION The invention relates to improvements in lamps, especially sunlamps, which emit radiation in the visible and ultraviolet ranges of the spectrum. It is already known to fill the envelope of a sunlamp with a mixture of radiation emitting substances which ensure that the lamp can emit radiation in the visible as well as in the UVA band of the ultraviolet range of the spectrum. The effect of such lamps strongly resembles that of sunlight except that the lamps cannot radiate the same amount of heat energy. However, the addition of a substance which causes the lamp to radiate in the UVA band affects a pronounced reduction of radiation in the visible range, i.e., the brightness of such lamps is less than satisfactory. It is also known to confine in the envelope of a lamp a substance which has pronounced radiation peaks in the red, blue and green portions of the visible range, i.e., in those portions of the visible range in which the human eye is particularly sensitive so that the lamp can be categorized as a "bright" lamp. OBJECTS AND SUMMARY OF THE INVENTION An object of the invention is to provide a lamp, particularly a sunlamp, whose brightness is highly satisfactory even though it is capable of emitting radiation in the visible as well as in the ultraviolet range of the spectrum. Another object of the invention is to provide a lamp whose photobiological effect in the ultraviolet range is highly satisfactory in spite of the fact that it can be categorized as a "bright" lamp. A further object of the invention is to provide a sunlamp which can be utilized for long periods of time without any adverse effects upon the person whose body is exposed to its radiation. An additional object of the invention is to provide a novel and improved combination of radiation-emitting substances which can be utilized in a lamp of the above outlined character. Another object of the invention is to provide novel and improved substances which can be utilized in the above outlined lamp to ensure the emission of beneficial radiation in the UVA and UVB bands of the ultraviolet range of the spectrum. A further object of the invention is to provide a novel and improved ratio of radiation emitting substances which can be used in the above outlined lamp. The invention is embodied in a lamp which emits radiation in the red, blue and green bands of the visible range as well as in the long-wave and short-wave portions of the UVA range of the spectrum. The energy maximum of radiation in the long-wave portion of the UVA range is less pronounced than the energy maxima in the red, blue and green bands of the visible range, and the energy maximum of radiation in the short-wave portion of the UVA range is substantially less pronounced than in the long-wave portion of the UVA range and extends into the UVB range to terminate in the region of approximately 300 nm. The energy maximum of radiation in the long-wave portion of the UVA range is preferably between 370 and 390 nm. The lamp comprises an envelope and a mixture (e.g., an internal layer) of radiation emitting substances in the envelope. The mixture includes a first substance which emits radiation in the visible range, a second substance which emits radiation in the longwave portion of the UVA range, and a third substance which emits radiation between 300 and at least 320 nm. The second substance can emit radiation between approximately 350 and 400 nm, and the third substance is preferably selected to emit radiation up to approximately and at least slightly above 350 nm. The percentage of the first substance is preferably at least 80 percent of the sum of the first, second and third substances; the percentage of the second substance preferably exceeds the percentage of the third substance and the second substance preferably contains europium-activated strontium fluoroborate; the third substance preferably contains cerium-strontium-magnesium aluminate; the second substance preferably constitutes between 5 and 10 percent of the sum of the first, second and third substances; and the third substance preferably constitutes between 1 and 4 percent of the sum of the first, second and third substances. The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved lamp itself, however, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain specific embodiments with reference to the accompanying drawing.
042773636	abstract	The method for processing a mixture of air and rare gases consisting especially of xenon and krypton which are at least partially radioactive and especially for processing gaseous effluents arising from the reprocessing of irradiated fuels comprises a step involving concentration of the rare gases in solution in liquid argon by cryogenic distillation of the light gases and mainly nitrogen from the liquefied mixture.
	abstract	A method for calculating area values of a pattern written by using a charged particle beam, includes virtually dividing a pattern into a plurality of mesh-like first square regions surrounded by first grids defined at intervals of a predetermined size, virtually dividing the pattern into a plurality of mesh-like second square regions surrounded by second grids defined at intervals of the predetermined size, wherein the second grids being positionally deviated from the first grids by a half of the predetermined size, distributing an area value of a sub-pattern in each of the second square regions to a plurality of apexes of each of the second square regions such that a center-of-gravity position of the sub-pattern does not change, wherein the sub-pattern being a part of the pattern, and outputting the distributed area values as area values, for correcting a proximity effect, defined at the center position of each of the first square regions.
	claims	1. An X-ray diagnostic device comprising:an X-ray tube that emits X-rays in an X-ray beam;a diaphragm housing containing diaphragm plates movable relative to said X-ray beam for limiting an X-ray field produced by said X-ray beam;a beam sighting arrangement including a lamp and a mirror disposed in said housing, said lamp emitting light that is reflected by said mirror for producing a light ray field substantially coinciding with a hypothetical X-ray field;at least one filter disposed in said diaphragm housing for filtering the X-rays in said X-ray beam; anda single disk to which said filter and said mirror are mounted, said disk being rotatable around an axis of said disk for selectively moving either said mirror or said filter into said X-ray beam. 2. An X-ray diagnostic device as claimed in claim 1 wherein said disk is round and has a periphery, and comprising a plurality of teeth disposed at said periphery, and said X-ray diagnostic device comprising a motor-driven transmission interacting with said teeth at said periphery of said disk for rotating said disk.
	abstract	Inside-out gelation process to generate hydrogel microcapsules (aka microbeads). Methods of encapsulating biological material in the microbead 3-dimensional hydrogel matrix are described herein. The process generally comprises formation of a mixture of a hydrogel precursor compound, an optional biological material, and a divalent cation. The mixture is then combined with alginate, to generate an alginate shell around droplets of the mixture, followed by gelation of the hydrogel precursor core, and removal of the temporary alginate shell to yield self-sustaining microbeads.
	claims	1. A method for irradiating a charged particle beam onto an irradiation subject, the method comprising:determining, by performing a treatment optimization calculation by a treatment planning apparatus, an arrangement of columnar irradiation fields at a first plurality of locations of the irradiation subject in accordance with a distal form of the irradiation subject and at a second plurality of locations of the irradiation subject in accordance with a distal form of portions of the irradiation subject;when it is determined that the arrangement of columnar irradiation fields at the determined first plurality of locations and the determined second plurality of locations includes overlapping columnar irradiation fields, adjusting, by an optimization calculation unit, the arrangement of the overlapping columnar irradiation fields such that portions where the columnar irradiation fields overlap are eliminated and an irradiation dose falls within a predetermined range;after at least said determination, generating, by a columnar-irradiation-field generation apparatus, a columnar irradiation field having a Spread Out Bragg Peak (SOBP) width, wherein said generated columnar irradiation field (i) is generated without scattering the charged particle beam in an X-Y direction perpendicular to the charged particle beam and (ii) has a depth in the irradiation subject in the direction of the charged particle beam that is larger than a cross-sectional dimension of the charged particle beam in the X-Y direction perpendicular to the charged particle beam on the irradiation subject;in accordance with the treatment optimization calculation, (i) initially scanning, by a scanning system, the charged particle beam with the generated columnar irradiation field at the first plurality of locations of the irradiation subject in accordance with the distal form of the irradiation subject, and (ii) subsequently scanning, by the scanning system, the charged particle beam with the generated columnar irradiation field at the second plurality of locations of the irradiation subject in accordance with the distal form of portions of the irradiation subject, other than the first plurality of locations irradiated in the initial scanning. 2. The method of claim 1, wherein, during the subsequent scanning, the columnar irradiation field has a SOBP width that differs from the SOBP width of the columnar irradiation field during the initial scanning. 3. The method of claim 1, wherein the columnar-irradiation field generation apparatus includes an apparatus for changing the energy of the columnar irradiation field, and wherein, during the scanning steps, the energy of the columnar irradiation field is changed in accordance with the distal form of the area of the irradiation subject that is to be irradiated. 4. The method of claim 3, wherein:the energy changing apparatus comprises a plurality of absorbers, one absorber including a uniform thickness that differs from a uniform thickness of another absorber, andthe step of changing the energy of the columnar irradiation fields include adjusting, by at least one driving device, a combined thickness of the plurality of absorbers. 5. The method of claim 4, wherein adjusting the combined thickness of the plurality of absorbers includes positioning at least two absorbers from the plurality of absorbers along a beam axis of the charged particle beam such that the at least two absorbers from the plurality of absorbers are in alignment with the charged particle beam. 6. The method of claim 3, wherein the energy changing apparatus comprises a range shifter whose thickness changes in a direction perpendicular to the charged particle beam, and wherein the steps of scanning the charged particle beam in accordance with a distal form of the irradiation subject include moving the charged particle beam in said perpendicular direction, by at least one deflection electromagnet, to a desired location in the range shifter. 7. The method of claim 1, wherein, during the initial scanning, the columnar irradiation field is scanned along an outer distal periphery of the irradiation subject. 8. The method of claim 7, wherein, during the subsequent scanning, the columnar irradiation field is scanned along locations interior of the outer periphery scanned during the initial scanning. 9. The method of claim 1, wherein the generated columnar irradiation field of the charged particle beam enters the irradiation subject from a plurality of different directions during each of the initial and subsequent scannings.
	abstract	The Portable Nuclear Radioactive Fallout Protection Shelter & Preservation of Potable Water Storage System is comprised of self-supporting interlocking stackable radiation shielding watertight jugs having the dual purpose of being used to rapidly assemble fallout shelters and to store drinking water. The jugs are made of rigid neoprene, plastics, or similar substances that when filled with water and properly assembled omits radioactive gamma and X-rays. Wooden or metal support beams may be required when ceiling supports are necessary. The jugs may be filled using a common garden hose and be emptied by pouring water out of the water spouts that are also an integral part of the self supporting interlocking mechanisms and be drained by pouring water from the spouts or using a siphon hose or water pump. The system implements the construction of walls, modules, and complete protective shelters inside or outside of existing buildings.
	summary
053032829	description	DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A radiation imager system 10, such as a medical computed tomography (CT) system, incorporating the device of the present invention is shown in schematic form in FIG. 1. CT system 10 comprises a radiation point source 20 and a radiation detector 30 comprising a plurality of radiation detector panels 40 and a plurality of collimators 50 disposed between radiation source 20, typically an x-ray source, and detector panels 40. Each detector plate comprises a plurality of detector elements (not shown) that convert incident radiation into electrical signals. The detector elements are typically arranged in a one- or two-dimensional array. The radiation detector elements are coupled to a signal processing circuit 60 and thence to an image analysis and display circuit 70. Detector panels 40 are mounted on a curved supporting surface 80 which is positioned at a substantially constant radius from radiation point source 20. This arrangement allows an object or subject 90 to be placed at a position between the radiation source and and the radiation detector for examination. Collimators 50 are positioned over radiation detector panels 40 to allow passage of radiation beams that emanate directly from radiation source 20, through exam subject 90, to radiation detector panels 40, while absorbing substantially all other beams of radiation that strike the collimator. The details of steps in the fabrication, and the resulting structure, of collimators 50 in accordance with this invention are set out below. FIG. 2 is a cross-sectional view of a representative portion of a collimator substrate 110. Substrate 110 comprises photosensitive material, i.e., a material that will react to exposure to light in a manner similar to photoresist, to allow etching of a pattern in the material. Such photosensitive material may lose its photosensitive characteristics after it has been exposed to light and processed. One example of this type of substrate material is the Corning, Inc. product known as Fotoform.RTM. glass. An optically opaque mask 112 is formed by conventional methods on a first surface 110a of collimator substrate 110. The pattern of openings in mask 112 corresponds to the pattern of detector elements in each radiation detector panel 40 (FIG. 1). For example, mask 112 would have a pattern generally mimicking the arrangement, e.g., rows and columns in a two-dimensional array, as well as the cross-sectional shapes of detector elements at the interface between radiation detector panel 40 and collimator 50 (FIG. 1). Alternatively, mask 112 need not be on the surface of the collimator substrate but can be positioned with respect to the substrate in accordance with known photolithographic techniques to provide the desired exposure of the photosensitive material in substrate 110. In any event, the pattern of the mask is selected to expose areas of photosensitive collimator substrate 110 of sufficient size and orientation so that, upon completion of the fabrication of collimator 50, the surface of each radiation detector element for receiving the radiation is exposed to radiation passing along the desired paths from the radiation source. In accordance with the present invention, collimator substrate 110 and mask 112 are exposed to light from light source 114. Light source 114 is preferably a laser, an ultraviolet light source, or the like, and is positioned with respect to collimator substrate 110 so that light beams pass through the openings in mask 112 and strike collimator substrate 110 along paths corresponding to direct paths between radiation point source 20 and radiation detector 30 (FIG. 1). As illustrated in FIG. 2, exemplar pairs of light beams 116a-b, 116c-d, and 116e-f define the boundaries of exposed photosensitive material shown in cross section. The light beams exposing the photosensitive material under each respective opening in mask 112 strike the collimator substrate at slightly different angles, the magnitude and orientation of which depend on the position along the length of the collimator substrate where the light strikes. For example, light beams 116a and 116b strike the collimator substrate at angles which differ in magnitude and orientation (i.e. left or right with respect to a perpendicular between the substrate and the light source) from light beams 116c-d and 116e-f. The light beams falling on photosensitive collimator substrate 110 define a plurality of respective exposed volumes 118 in the photosensitive material under each opening in the mask through which the light beams pass. Each exposed volume 118 has a longitudinal axis at a selected orientation angle corresponding to the angle at which the light beams emanating along a direct path from light source 114 strike the collimator substrate. Thus light beams 116a-b expose a volume that has a selected orientation angle .beta., whereas light beams 116e-f expose a volume having a different selected orientation angle, .differential.. The position of the collimator substrate with respect to light source 114 is selected to correspond with the distance that the collimator substrate will be from the radiation source in the assembled imager. Further, to ensure that the exposed volumes have the correct selected orientation angles required for collimating radiation in the assembled device, the plane of the collimator substrate is oriented at a "planar angle" so that the plane of the substrate has the same orientation with respect to the light source as the radiation detector panel with respect to the radiation source in the assembled device. Collimator substrate 110 is then etched using conventional techniques appropriate for the photosensitive material used in the substrate to remove the exposed volumes 118 of photosensitive material and create a plurality of channels or passages 120 through the substrate, as illustrated in FIG. 3. Each of these channels has a longitudinal axis 122 aligned with the selected orientation angle defined when the photosensitive material was exposed to light source 114 (FIG. 2). Typically the selected orientation angles of the longitudinal axes of the channels range between about 0.degree. and 10.degree.. Each channel has a channel sidewall 124 which is substantially smooth along its length and has a substantially uniform slope formed when the photosensitive material exposed by the light beams in the previous step is removed in the longitudinal axes of the channels range between about 0.degree. and 10.degree.. Each process. The slope of the sidewalls is typically substantially aligned with the selected orientation angle of the channel defined by those sidewalls. The remaining portions of mask 112 may next removed to prepare the collimator substrate for the next step in the process of forming the collimator. A radiation absorbent material layer 130 (FIG. 3) is then applied on collimator substrate 110 so as to cover at least the surfaces of the substrate which will be exposed to incident radiation when assembled in an imager device. The radiation absorbent material at least covers all of the sidewalls defining the channel. The cross-sectional portion of the radiation absorbent material on the sidewalls and the top and bottom of substrate 110 is illustrated in FIG. 3 in cross-hatch, while the radiation absorbent material on the "back" sidewall of the channel is illustrated in alternating cross-hatch and dashed lines. The radiation absorbent material can be applied through known techniques, such as vapor deposition techniques. Radiation absorbent material 130 is selected to absorb radiation of the wavelength distribution emitted by radiation source 20 (FIG. 1) in the imager device. The radiation absorbent material typically has a relatively high atomic number, e.g., greater than about 72, and advantageously comprises tungsten, lead, or gold when the radiation used in the imager device is x-ray. The thickness of the radiation absorbent material layer is selected to provide efficient absorption of the incident radiation and depends on the type of incident radiation and the energy level of the radiation when it strikes the collimator. For example, in a typical CT system using an x-ray point radiation source of about 100 KeV positioned approximately one meter from the detector array, a total thickness in the range of about 30 to 40 mils of tungsten in one or more layers disposed along the path of the radiation will substantially absorb the x-rays emitted by the source. After application of the radiation absorbent material, the cross-sectional area of the opening or void space in the channel is substantially the same as the area for receiving radiation on the detector element which it adjoins so as to allow substantially all radiation rays emanating along direct paths from the radiation source to strike the detector element. When two or more substrates are joined together to form the collimator body, the openings of the channels in the respective surfaces of the collimator substrates are aligned to form continuous channels through the collimator body. The channel sidewalls are advantageously aligned so that the sidewalls of the respective channels in the adjoining substrates are contiguous. Dependent on the energy level and wavelength of the radiation to be collimated, different thicknesses of collimator bodies may be required. Once the necessary thickness has been determined, an appropriate thickness of collimator substrate, or plurality of substrates, can be selected and fabricated in accordance with this invention. For example, the thickness of a collimator for an imager system using x-rays, such as a CT system, may be only about 8 mm, but for an imager using gamma rays, the collimator preferably would be three to five times thicker than that used for x-ray radiation. In the assembled device, collimator body 55 is disposed to adjoin radiation detector panel 40, as illustrated in FIG. 4. Radiation detector elements 42 are positioned along detector panel 40 and typically comprise a scintillator coupled to a photodetector. Collimator body 55 is positioned to allow incident radiation on a direct path between the radiation source and one of the radiation detector elements 42 to pass through the channels in the collimator. Beams of radiation that are not aligned with such a direct path strike the collimator body and are absorbed. The collimator of the present invention is readily used with either a one-dimensional or a two-dimensional array of radiation detector elements. A plan view of a collimator fabricated in accordance with the present invention and showing a representative number of channels 120 appears in FIG. 5. The figure has been marked to show left, right, upper and lower edges solely to provide a reference for ease of discussion, and the selection and positioning of such references is not meant to constitute any limitation on the structure or positioning of the device of the invention. Openings 122 of channels 120 on the opposite surface of collimator body 55 are shown in phantom. In the two-dimensional array the center channel is in substantial vertical alignment with the radiation source, and the opening 122 of the channel on the side of the collimator body opposite the radiation source is aligned with the opening in the surface closest to the radiation source. As the radiation beams spread out as they emanate from the point source, each of openings 122 has a slightly larger cross-sectional area than the respective opening of the channel 120 in the surface of the collimator closest to the radiation source. Openings 122 for channels on the left, right, top, or bottom are slightly offset from being in vertical alignment with their respective openings in the upper surface of the substrate. The direct path from the radiation source to a radiation detector in the upper left hand corner, for example, is offset both to the left and the upper side of the array. The selected orientation angle of the axis of the channel is substantially aligned with this direct path, and the channel thus extends through the collimator body at this angle. The selected orientation angle for each channel is different from any other channel in the collimator. Such a structure, which would be extremely difficult and time consuming to construct with conventional collimator fabrication techniques, is readily produced in accordance with this invention. While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.
039792587	claims	1. In a nuclear reactor having a bed of spherical reaction elements forming a core, at least one axially elongated absorber control rod, and means connected to said control rod for inserting and withdrawing said rod in the axial direction into and out of the core, wherein the improvement comprises that said control rod as it is inserted into the core by said means contacts the reaction elements directly, said means is connected to said rod for moving said control rod only in the rectilinear direction into and out of the core in the axial direction of said control rod and wherein the connection of said rod to said means permits rotation of the rod about its longitudinal axis in response to the direct contact of the control rod with the spherical elements independent of the rectilinear movement provided by said drive means, said control rod having an external surface which contacts the reaction elements and said external surface has an axial length with the actual axial length of said external surface in contact with said reaction elements being variable based on the extent to which said control rod is inserted into said core, said axial length consists of a lead-in portion which extends for a substantial portion of said total axial length of said control rod which can contact the reaction elements from the end thereof which first enters the core as the control rod is inserted into the core and a remaining portion which extends axially from the trailing end of said lead-in portion and follows said lead-in portion as it is inserted into the core, the circumferentially extending said external surface of said lead-in portion has a varying radial dimension from the longitudianl axis of said control rod so that the reaction elements are deflected outwardly away from said control rod as it is displaced axially within said core, said remaining portion of said control rod has an axially extending thread means, and said thread means on said remaining portion comprises a screw thread formed continuously about the circumferential periphery of the external surface of said remaining portion so that the moving contact between said screw thread and the reaction elements caused by the movement of said control rod by said means effects the rotation of said control rod. 2. A reactor, as set forth in claim 1, wherein the circumferential surface of said lead-in portion comprises an axially extending cylindrically shaped surface and a plurality of laterally spaced ribs extending in the axial direction of said control rod and projecting outwardly from said cylindrical surface. 3. A reactor, as set forth in claim 1, wherein the circumferential surface of said lead-in portion comprises an axially extending section having a transverse oval-shaped cross section. 4. A reactor as set forth in claim 1, wherein the circumferential surface of said lead-in portion comprises a first thread means, said first thread means comprises a first screw thread, said first screw thread formed continuously about the circumferential periphery of the external surface of said lead-in portion, and said first screw thread has a pitch greater than the pitch of said screw thread on said remaining portion. 5. In a nuclear reactor having a bed of spherical reaction elements forming a core, at least one axially elongated absorber control rod, and means connected to said control rod for inserting and withdrawing said rod in the axial direction into and out of the core, wherein the improvement comprises that said control rod as it is inserted into the core by said means contacts the reaction elements directly, said means is connected to said rod for moving said control rod only in the rectilinear direction into and out of the core in the axial direction of said control rod and wherein the connection of rod to said means rotation of the rod about its longitudinal axis in response to the direct contact of the control rod with the spherical elements independent of the rectilinear movement provided by said means, said control rod having an external surface which contacts the reaction elements and said external surface has an axial length with the actual axial length of said external surface in contact with said reaction elements being variable based on the extent to which said control rod is inserted into said core, said axial length consists of a lead-in portion which extends for a substantial portion of said total axial length of said control rod which can contact the reaction elements from the end thereof which first enters the core as the control rod is inserted into the core and a remaining portion which extends axially from the trailing end of said lead-in portion and follows said lead-in portion as it is inserted into the core, the external surface of said lead-in portion has a first thread means, the external surface of said remaining portion of said control rod has a second thread means, said first thread means comprises a first screw thread, said first screw thread formed continuously about the circumferential periphery of the external surface of said lead-in portion, said second thread means comprises a second screw thread formed continuously about the circumferential periphery of the external surface of the remaining part of said control rod, and said first screw thread has a pitch greater than the pitch of said second screw thread.
	summary
	description	The present invention concerns a heat exchanger module with a stack of metal plates and with at least two integrated fluid circuits. The present invention relates more particularly to the production of a new type of heat exchanger module to improve the uniformity of the distribution of the various fluid internal circulation channels, whilst at the same time ensuring good thermal efficiency and satisfactory thermomechanical loading, without compromising the compactness of the module. Known heat exchangers comprise at least two circuits with internal fluid circulation channels. In exchangers with only one circuit, the exchanges of heat are effected between the circuit and a surrounding fluid in which it is immersed. In exchanges with at least two fluid circuits, the exchanges of heat are effected between the two fluid circuits. There are known chemical reactors that employ a continuous process whereby a small quantity of co-reagents is injected at the inlet of a first fluid circuit, preferably equipped with a mixer, and the chemical product obtained is simultaneously recovered at the outlet of said first circuit. Some of these known chemical reactors comprise a second fluid circuit, usually termed a utility circuit, the function of which is thermal control of the chemical reaction, either by input of the heat necessary for the reaction or to the contrary by evacuation of the heat given off thereby. Chemical reactors of this kind with two fluid circuits with utility are usually termed exchanger-reactors. The present invention concerns as much the production of heat exchanger modules with the sole function of exchange of heat and two integrated fluid circuits as the production of exchanger-reactors. Accordingly, by “heat exchanger module with at least two fluid circuits” must be understood, in the context of the invention, as much a heat exchanger module with only the heat exchange function as an exchanger-reactor. The principal use of an exchanger module according to the invention using two fluids is its use with a gas as one of the two fluids. This may advantageously refer to a liquid metal and a gas, for example liquid sodium and nitrogen. The principal intended application of an exchanger module according to the invention is the exchange of heat between a liquid metal, such as liquid sodium, in the secondary loop and nitrogen as the gas in the tertiary loop of a fast neutron reactor cooled by liquid metal, such as a liquid sodium cooled fast reactor (SFR) and that is part of the family of so-called fourth generation reactors. A heat exchanger module according to the invention may also be used in any other application necessitating an exchange between two fluids, such as a liquid and a gas, preferably when it is necessary to have a compact exchanger of high thermal power. By “primary fluid” is meant in the context of the invention the usual meaning in the thermal field, namely the hot fluid that transfers its heat to the secondary fluid, which is the cold fluid. A contrario, by “secondary fluid” is meant in the context of the invention, in the usual sense in the thermal field, namely the cold fluid to which heat is transferred from the primary fluid. In the principal application, the primary fluid is the sodium that circulates in the so-called secondary loop of the thermal conversion cycle of an RNR-Na reactor, while the secondary fluid is the nitrogen that circulates in the tertiary loop of said cycle. Known tube exchangers are for example shell and tube exchangers, in which a U-shape or helical shape bundle of straight or curved tubes is fixed to perforated plates and disposed inside a fluid-tight enclosure termed the shell. In these tube and shell exchangers, one of the fluids circulates inside the tubes while the other fluid circulates inside the shell. These tube and shell exchanges have a large volume and are therefore of small compactness. Existing so-called plate heat exchangers have major advantages compared to existing so-called tube heat exchangers, in particular in terms of their thermal performance and their compactness thanks to a favorably high ratio of the surface area to the volume of thermal exchange. Compact plate exchangers are used in numerous industrial fields. In this field of compact plate exchangers, numerous elementary shapes defining thermal exchange patterns have been developed. There may first be cited exchangers with plates integrating fins, in which a thermal exchange pattern is defined by a structure delimited by fins, the structures being mounted between two metal plates and having highly varied geometries. The exchange pattern may be different between one of the two fluid circuits of the exchanger and the other one. The assembly between metal plates is usually effected by brazing or by diffusion welding. There are also known exchangers with undulating or corrugated plates. The undulations are created by drawing a plate separating the two fluid circuits. Because of this, the exchange pattern is identical for each of the two fluid circuits. The flow of fluids generated by this type of exchange pattern is three-dimensional and therefore offers very high performance. The assembly between plates is effected either by bolted connections or by peripherally welding them (conventional welding or diffusion welding). There are finally known plate exchangers with machined grooves, the machining being carried out mechanically or electrochemically. The channels defined by machining are of millimeter-size section and are most often continuous with a regular zigzag profile. The plates are assembled by diffusion welding enabling welding at all points of contact between two adjacent plates. This type of plate exchanger with machined grooves is therefore inherently highly resistant to pressure. Some of the inventors of the present invention have designed an exchanger with modules using stacked plates for the exchange of heat between a gas and a liquid metal in the context of the production of a nuclear reactor of the so-called fourth generation reactor family, that is to say in a configuration of thermal exchange between an excellent heat conductor, the liquid metal, typically liquid sodium (Na), and a fluid with much lower heat transfer properties, the gas, typically nitrogen (N2). Thus the patent application WO2015/028923 A1 describes and claims a heat exchanger in which the heat exchanger modules are arranged inside and rigidly fixed to an enclosure pressurized by the pressure of the gas, typically around 180 bar, by means of a support and retaining structure, while the liquid metal distribution pipework is not fixed to that support structure. In the above design, the fluid-tight enclosure has a gas circuit manifold role and the dimensions of the heat exchanger modules are governed primarily by the gas, as it is the less thermally conductive of the two fluids. While the size of the exchange pattern of the gas circulation channels is strictly dictated by thermo-hydraulic performance constraints, the size of the liquid metal circulation channels must take into consideration the risks of blockage linked to the circulation of the liquid metal, which limits the minimum section of the latter's circulation channels. Taking also into account differences in physical characteristics, more particularly density characteristics, between a gas and a liquid metal, a resulting exchanger module has head losses in the liquid metal circulation channels that are very low, typically of the order of 40 mbar. Moreover, aiming at compactness, each exchanger module has a unitary thermal power rating of the order of 12 MWth, which, given the rules regarding dimensions, implies a very large number of fluid circulation channels, typically equal to approximately 5000 per module. Another constraint to be considered stems from the fact that each module is arranged inside an enclosure pressurized by the gas. In operation, the structures feeding and recovering the liquid metal, consisting of the manifolds and the distribution pipework, may be subjected to high temperatures and compression forces that unless particular precautions are taken could lead to damage by buckling resulting from creep. Also, from a thermomechanical point of view, these structures must be designed to be as compact as possible. To summarize, the configuration of the heat exchanger modules inside the enclosure pressurized by the gas, according to the aforementioned application WO2015/028923 A1, implies a very large number of channels per module with great compactness. Now, the inventors of the present invention have analyzed that this configuration may lead to a non-uniform distribution of the liquid metal in the channels in each exchanger module, which may compromise on the one hand the overall thermal efficiency of the exchanger and on the other hand the thermomechanical strength of the structures of the exchanger. Thus the inventors were faced with the necessity to design a plate exchanger module enabling homogeneous distribution of liquid metal in the circulation channels in the module to be ensured. Although the hydraulic conditions of an exchanger module according to the aforementioned configuration are not much encountered in the prior art, notably because of a ratio between the very high Reynolds number Re at the inlet and the relatively low one in the channels, the inventors have made an inventory of the various existing solutions enabling rendering the circulation of a fluid in an exchanger more homogeneous (uniform). One of the known solutions consists in increasing the size of the liquid metal manifolds, in order to reduce the speed range in the latter and therefore the dynamic pressure, compared to the head loss in the channels of the module. This solution cannot be adopted because as mentioned above the structures feeding and recovering the liquid metal must be as compact as possible and therefore the manifold as small as possible. It is also known to place a grille inside the manifold. This grille enables the liquid metal jet to be broken up before it enters the module. This solution is pertinent on the hydraulic level, because it could make it possible to solve the problem of poor distribution between plates and within the same plate with a very low cost in terms of head loss, typically with a residual dispersion value of 3% and a pressure variation less than 150 mbar. The major disadvantage of this solution with a grille mounted inside the manifold is the addition of a thermal inertia, which is prejudicial in an operating regime with thermal transients. Moreover, because of the additional component consisting of the grille, mounted inside the manifold, the latter has a size that remains large and that therefore necessitates high wall thicknesses. Finally, it is known to shape the channels with bifurcations in the liquid metal entry zone, which is as it were a pre-manifold. Above all else this makes it possible to reduce the number of channels to which the fluid is to be distributed at the level of the manifold. There have been shown in FIGS. 1 to 3 examples of bifurcation from a single channel 10 formed in a metal plate, which respectively lead to sixteen channels 10.1 to 10.16 or five channels 10.1 to 10.2 for the exchange zone. It is specified that the configuration of FIG. 2 differs from that of FIG. 1 in that the channels are interconnected in the central exchange part. The efficiency of this solution increases as the channel head loss increases, typically corresponding to a residual dispersion value of 10% and a pressure variation of 500 mbar, or to a residual dispersion value of 13% and a pressure variation of 350 mbar. Now, given the very large number of fluid circulation channels to be fed per module, a solution with a single channel per module on the inlet side cannot be adopted. In fact, to preserve acceptable head losses in a module, only a reduction by a factor of 4 in the number of channels discharging into the manifold may be suitable. In other words, the inventors have also concluded that the use of bifurcations as in the prior art cannot be adopted in the context of the configuration explained above, because that does not enable reduction by less than 10% of a poor distribution of the liquid metal in each module. Undoubtedly, work has been done on the optimum bifurcation geometry for the latter not to lead to poor distribution. Thus the patent application WO2015/092199 discloses a compact catalytic reactor with fewer than three plates, the channels of the plates having at least one zone of straight channels of millimeter size, which is a heat exchange zone, and at least one fluid distribution zone on the upstream and/or downstream side of the exchange zone, with a discontinuity of the walls (ribs) that separate the channels along the distribution zone, and an increase in the width of the walls along the distribution zone. The U.S. Pat. No. 4,665,975 discloses a heat exchanger with a stack of plates assembled by diffusion welding, the channels of each plate being configured with three zones including a manifold zone, a pre-manifold zone, and a distribution/exchange zone, the channels communicating with one another, transversely to the longitudinal axis of the plates, at the interface between the pre-manifold zone and the exchange zone, which enables pressure rebalancing. Although the solution described in the application WO2015/092199A1 a priori improves the distribution of the fluid in the channels in the same plate in a good number of hydraulic configurations, the solution according to the U.S. Pat. No. 4,665,975 may give rise to certain problems because of an unbalanced geometry (length and bends) of the channels constituting the pre-manifold zone, which generates unwanted recirculation of fluid. Moreover, and above all, none of the above solutions enables solution of the problem of a non-homogeneous distribution between the plates of the stack of exchangers. There is therefore a need for further improvement of compact heat exchanger modules with stacked plates, with at least two integrated fluid circuits, in particular those intended for exchange of heat between a gas and a liquid metal, notably with the aim of rendering more homogeneous the distribution of the fluids in the modules, that is to say both in a given plate and between the plates of the stack, without compromising the compactness of the modules. The object of the invention is to address at least part of this need. To this end, the invention consists in a heat exchanger module with longitudinal axis (X) comprising a stack of plates defining at least two fluid circuits, at least some of the plates each comprising fluid circulation channels each delimited at least in part by a groove, the channels of at least one of the two circuits, termed the first circuit, including: a zone of feeding the fluid from the exterior of the stack, in which the channels are parallel to one another and extend along a secant axis (X′) intersecting the longitudinal axis (X) and in which two adjacent channels communicate with one another via at least one notch formed in the rib separating their respective grooves; a zone termed the bifurcation zone in which each channel is divided into at least two straight channels parallel to one another and parallel to the longitudinal axis (X), being separated from one another by a rib; a zone termed the connection zone between the feeding zone and the bifurcation zone, the zone in which each channel has a straight profile that extends along the secant axis (X′) and a curved profile continuous with the straight profile in order to connect the channel with a straight channel of the bifurcation zone; a zone of continuous exchange with the bifurcation zone in which the parallel straight channels separated from one another by the ribs extend parallel to the longitudinal axis (X). In the module according to the invention, the channels of each plate of the first circuit communicate with those of the other plates of the first circuit in their respective feed zone, via openings passing through the stack but not communicating with the channels of the second circuit. In other words, the invention essentially consists in judiciously combining communication of the channels with one another in the same plate and between all the plates of the same circuit, in a feed or pre-manifold zone, with a succession of two-by-two groupings of channels in the form of bifurcations. The communication between channels takes the role of a jet-break grille that is integrated into each plate and between the plates, which makes possible natural rebalancing of the flows between all the channels of the same fluid and therefore guarantees homogeneous distribution. The succession of groups of channels enables reduction of the number of channels to be fed by the manifold on the outside of the stack and thereby to increase the head loss induced and also to reduce the size of the manifold. Thanks to the invention, it is therefore possible to distribute homogeneously all the circulation channels of a fluid circuit in a module, even in a critical hydraulic situation in which the manifold has small dimensions, the feed rate is high, and the head loss of the channels is low. The principal advantages of the invention are being able to address the problem of a poor distribution of one of the fluids in an exchanger module without adding any non-integrated device by modification of the head loss (bifurcation zone) and with an integrated grille enabling communication between channels of the same plate and between plates, enabling the module to remain very compact and reducing the size of the inlet manifold. The invention also enables reduction of the number of channels to be fed, which enables reduction of the size of the manifold, and improvement of the thermomechanical dimensions. The inventors have carried out preliminary computational fluid dynamics (CFD) calculations. Those calculations show that the invention enables improvement of the homogeneity of distribution of liquid sodium in a heat exchanger module, under real world conditions of use in the context of an Na/gas exchanger of a fourth generation nuclear reactor. According to a variant embodiment, the curved profile of each channel of the first circuit comprises two curves to connect the straight profile of the connection zone to the straight channel of the bifurcation zone. According to an advantageous embodiment, each straight channel is divided into four channels in the bifurcation zone. According to another advantageous embodiment, the angle between the secant axis (X′) and the longitudinal axis (X) of the module is between 0 and 45° inclusive. An advantageous alternative for the production of the module may consist in inserting a plate of the first circuit between two plates of the second circuit at least in the central part of the stack. The channels of the first circuit may have an oval, circular, rectangular or square section. The metal constituting the plates of the exchanger module according to the invention is chosen as a function of the conditions of its intended use, namely the pressure of the fluids, the temperatures and the natures of the fluids circulating through the module. It may for example be a question of aluminum, copper, nickel, titanium or alloys of those elements as well as a steel, notably an alloy steel or stainless steel, or a refractory metal chosen from alloys of niobium, molybdenum, tantalum or tungsten. The invention also consists in a method of producing a heat exchanger module described hereinabove, comprising the following steps: machining grooves in first metal plates in order to constitute the channels of the first circuit configured with the feed, connection, bifurcation and exchange zones; machining grooves in second metal plates in order to constitute the channels of the second circuit; alternately stacking the first plates and the second plates so as to have the through-openings that enable communication between channels of the plates of the first circuit but not with those of the plates of the second circuit, assembling the first and second metal plates to one another, either by hot isostatic compression (HIC), or by a process termed a hot uniaxial diffusion welding process, so as to obtain diffusion welding between them, or by brazing. The invention also concerns a heat exchanger comprising a fluid-tight enclosure intended to be pressurized by a fluid circulating in the second circuit and a plurality of heat exchanger modules as described above each extending parallel to the central axis of the enclosure and each arranged inside the enclosure. The invention also consists in use of the heat exchanger as described above, the fluid of the first circuit, by way of primary fluid being a liquid metal and the fluid of the second circuit, by way of a secondary fluid, being a gas or a gas mixture. The fluid in the second circuit may principally comprise nitrogen and the first fluid of the first is liquid sodium. The fluid in the first or second circuit may come from a nuclear reactor. The invention finally consists in a nuclear installation comprising a fast neutral nuclear reactor cooled with liquid metal, notably liquid sodium cooled fast reactor (SFR) and a heat exchanger comprising a plurality of exchanger modules as described above. For clarity, the same elements in accordance with the prior art and in accordance with the invention are designated by the same reference numbers. In the whole application, the terms “inlet”, “outlet”, “upstream”, “downstream” are to be understood in relation to the direction of circulation of the fluid concerned in a heat exchange module according to the invention. FIGS. 1 to 3 relating to the prior art have already been commented on in the preamble. They are therefore not described hereinafter. There has been shown in FIGS. 4 to 7 a plate 1 of one of the two fluid circuits, termed the first circuit, of a heat exchanger module according to the invention, which extends along a longitudinal axis X. This first circuit is preferably intended to circulate a liquid metal, such as liquid sodium. This plate 1 is grooved with channels 10, 11, 12, 13 with zones Z1, Z2, Z3, Z4 produced and shaped differently. In the feed zone Z1 for feeding fluid from outside the stack, the channels 10 are parallel to one another and extend along a secant axis X′ intersecting the longitudinal axis X and two adjacent channels 10 communicate with one another via at least one notch 16 formed in the rib 15 separating their respective grooves. As can be seen in FIG. 6, through-openings 17 are made in each channel 10 to enable communication between all the plates 1 of the first circuit through the stack. To this end, other through-openings not shown are also made through the plates 2 of the second circuit. These other through-openings do not enable communication between the channels of the first circuit and those of the second circuit. Accordingly, the channels 10 with the notches 16 between channels and the openings 17 through the plates 1 form a communication grille between channels of the same plate 1 and between the plates 1. In continuity with the feed zone Z1, the channels are extended in a connection zone Z2. In this zone Z2, each channel has a straight profile 11 that extends along the secant axis X′ and a curved profile 12 continuous with the straight profile to connect the channel 11 with a straight channel of a bifurcation zone Z3 in continuity with and downstream of the connection zone Z2. FIG. 5 is a variant of FIG. 4 in which the curved profiles are shorter in order to have all of the channels 13 in the bifurcation zone aligned transversely with the longitudinal axis X. As can be seen in FIGS. 4 and 5, the connection zone Z2 has a relatively large area, which enables sufficient physical separation between the feed zone Z1 and the downstream bifurcation zone Z3. This physical separation enables sufficient space to be provided in the plates 2 of the second circuit so that there is no communication between the channels of the first circuit with those of the second circuit. In the bifurcation zone Z3, each channel 13 is divided into four channels 13.1, 13.2, 13.3, 13.4 that are straight, parallel to one another and extend parallel to the longitudinal axis X, being separated from one another by a rib. Finally, in continuity with the bifurcation zone Z3, the thermal exchange zone Z4 integrates the straight, parallel channels 13.1, 13.2, 13.3, 13.4 separated from one another by the ribs extending parallel to the longitudinal axis X. There has been represented in FIG. 7 a variant embodiment of the feed zone Z1 in which the rib portions 18 that separate the openings 16 between channels 10 are all identical and aligned, likewise the through-openings 17. There has been represented in FIG. 8 an example of the dimensions of the plate 1 in the feed zone Z1 in the variant from FIG. 7. For example, the numerical values are as follows: R1=1.5 mm, e1=42.5 mm, e2=32.5 mm, e3=3 mm, e4=7 mm. In an analogous manner, FIG. 9 shows an example of the dimensions of a channel 13 with four bifurcations 13.1 to 13.4 based on the curved profile 12 of the connection zone Z2. For example, the numerical values are as follows: R2=20 mm, R3=26 mm, e5=25 mm, e6=5.2 mm, e7=25 mm, e8=5.2 mm, e9=25 mm and e10=6 mm. The following procedure is used to produce an exchanger module according to the invention. There are respectively machined in identical metal plates 1 of rectangular shape grooves with the feed zone Z1, connection zone Z2, bifurcation zone Z3 and exchange zone Z4 as described in detail above. The plates 1 are then machined in the zones Z1 so as to have the notches 16 between the channels 10 and the openings 17 through each plate 1. Grooves 20 defining the channels of the second circuit are machined in metal plates 2 of identical shape and size to the plates 1. An alternating stack is produced of the plates 1 of the first circuit with the plates 2 of the second circuit so as to have the through-openings 17 that enable communication between channels of the plates 1 of the first circuit but not with those of the plates of the second circuit. The metal plates 1, 2 are then assembled together, either by hot isostatic compression (HIC), or by a hot uniaxial diffusion welding process so as to obtain diffusion welding between them. Comparative CFD calculations have been carried out by the inventors, in order to verify the best fluid distribution performance in the first circuit of the module according to the invention. The calculations have been done with the hypothesis of circulation of liquid sodium at a temperature of 545° C. at the inlet of the first circuit. It is specified here that a channel in accordance with the comparative examples 1 and 2 has the same dimensions, i.e. length, width and height, as a channel in accordance with example 3 in accordance with the invention. All the comparative calculations are summarized in the table below. Comparative example 1 relates to a prior art module in which the channels of the zone Z4 of the Na circuit are straight and all discharge into the manifold. Comparative example 2 relates to a module comprising channels in the plates 1 only between the fluid inlet and the exchange zone Z4, a zone Z3 with the bifurcations as shown in FIGS. 4 and 5 and sized like those of the invention in FIG. 9. Example 3 conforms to the invention, with a module comprising channels in the plates 1 with all the zones Z1 to Z4, the zone Z1 being sized as in FIG. 8 and the zone Z3 with the bifurcations sized like those of the invention in FIG. 9. In all the examples the other shapes and dimensions of the plates 1 and 2 are identical. There has further been indicated in the table an ideal case of exchange between liquid sodium that leaves the exchanger at 345° C. and nitrogen that enters at 310° C. TABLETotalFlow headdispersionLiquid sodium temperature lossesper at outlet of moduleThermalΔP channel (° C.)efficiency(Pa)(%)minimummeanmaximum(ε)Ideal case03453453450.93Example 16000253153494380.91Example 25000083303433840.92Example 360000<2−345345−3450.93(according to the invention) In this table, it is seen that thanks to the invention the dispersion of the flows per channel is much lower, the head losses much higher but acceptable, with a thermal efficiency equal to the ideal case. Moreover compared to example 2, it is seen that the zones Z1 with notches 16 and the through-openings between plates 1 enable a reduction of the dispersion of the flows by a factor of 4. It may therefore be concluded from this that the system enables improvement of the distribution of liquid sodium. Other variants and improvements may be provided without this departing from the scope of the invention. For example, in an exchanger module using a liquid metal, such as liquid sodium, and a gas, such as nitrogen, it is therefore possible and advantageous to envisage the gas circuit with straight channels and a liquid metal circuit with channels having the various zones Z1, Z2, Z3, Z4, and preferably of larger sections than those of the gas circuit channels. It goes without saying that a liquid metal/gas exchanger is one application example, and that it is entirely possible to envisage having the same zones Z1 to Z4 according to the invention for both the fluid circuits in the same exchanger. The second circuit being for preference more dedicated to the circulation of gas, not too much head loss must be introduced, and it is therefore preferable not to provide the bifurcation zone for the plates of this second circuit. On the other hand, it is advantageous to integrate a jet-breaker grille in each plate of the second circuit, in order to perfect the distribution. It goes without saying that the number of stages, that is to say of plates for the first circuit and/or for the second circuit, is to be adapted according to the operating conditions and that it is entirely feasible to envisage a number different from that in the embodiments shown.
046722114	claims	1. For use in a system requiring electromagnetic radiation to be radiated onto a utilization object, a blackbody simulator having a cavity defining an apex and a cavity surface, and an aperture to the cavity, said cavity surface being divided into a primary radiating surface and a secondary radiating surface, the primary radiating surface comprising portions of the cavity surface which are in direct line of sight to some portion of the utilization object through the aperture, the secondary radiating surface comprising portions of the cavity surface which are not part of the primary radiating surface; wherein the projected solid angle of the aperture with respect to all portions of the primary radiating surface is generally constant; and the primary radiating surface comprises a circular plate having at least one circular groove concentric with the apex, the half angle of said apex being in excess of 20.degree.. wherein the projected solid angle of the aperture with respect to all portiions of the primary radiating surface is generally constant; and the primary radiating surface comprises a circular plate having at least one circular groove concentric with the apex, the half angle of said apex being in excess of 20.degree.; and wherein the ratio of the depth of the cavity to the diameter of the aperture is in the range of approximately 5:1 to 1:1. wherein the projected solid angle of the aperture with respect to all portions of the primary radiating surface is generally constant; and the primary radiating surface comprises a circular plate having at least one circular groove concentric with the apex, the half angle of said apex being in excess of 20.degree.; and wherein the secondary radiating surface is a cylinder such that the ratio of the cylinder diameter to the aperture diameter ranges from approximately 10:1 to approximately 2:1. wherein the projected solid angle of the aperture with respect to all portions of the primary radiating surface is generally constant, the primary radiating surface comprises a circular plate having at least one circular groove concentric with the apex, and the ratio of the depth of the cavity to the aperture diameter ranges from approximately 5:1 to approximately 1:1. the core further having a cavity and an aperture on its first side of the cavity, the cavity being rotationally symmetrical about an axis and having a cone-like apex on the axis opposite the aperture with an apex half-angle of less than 60.degree. and greater than 20.degree., a substantial portion of the cavity surface being shaped so that the value of the projected solid angle of the aperture with respect to any point on the cavity surface portion is substantially constant; the cavity surface portion comprising at least n subsurfaces; the first subsurface extending from the apex toward the aperture; said n being an integer less than 7; a substantial number of said cavity portion subsurfaces defining inner and outer limiting curves with each of said substantial number of subsurfaces extending from the inner limiting curve to the outer limiting curve; said outer limiting curve remaining inside a sphere containing the rim of the aperture and having a radius such that the value of the projected solid angle of the aperture with respect to any point of the sphere is substantially constant, and said inner limiting curve remaining outside an arch defined by the locations at which a tangent in a plane containing the aixs of symmetry interesects the rim of the aperture for each subsurface if extended to the arch wherein the ratio of the depth of the cavity to the aperture diameter ranges from approximately 5:1 to 1:1. 2. The simulator of claim 1 wherein the half angle of the apex is in excess of 40.degree.. 3. For use in a system requiring electromagnetic radiation to be radiated onto a utilization object, a blackbody simulator having a cavity defining an apex and a cavity surface, and an aperture to the cavity, said cavity surface being divided into a primary radiating surface and a secondary radiating surface, the primary radiating surface comprising portions of the cavity surface which are in direct line of sight to some portion of the utilization object through the aperture, the secondary radiating surface comprising portions of the cavity surface which are not part of the primary radiating surface; 4. For use in a system requiring electromagnetic radiation to be radiated onto a utilization object, a blackbody simulator having a cavity defining an apex and a cavity surface, and an aperture to the cavity, said cavity surface being divided into a primary radiating surface and a secondary radiating surface, the primary radiating surface comprising portions of the cavity surface which are in direct line of sight to some portion of the utilization object through the aperture, the secondary radiating surface comprising portions of the cavity surface which are not part of the primary radiating surface; 5. For use in a system requiring electromagnetic radiation to be radiated onto a utilization object, a blackbody simulator having a cavity defining an apex and a cavity surface, and an aperture to the cavity, said cavity surface being divided into a primary radiating surface and a secondary radiating surface, the primary radiating surface comprising portions of the cavity surface which are in direct line of sight to some portion of the utilization object through the aperture, the secondary radiating surface comprising portions of the cavity surface which are not part of the primary radiating surface; 6. A core having a first side; 7. The simulator of claim 1 wherein the secondary radiating surface is defined by a portion of a sphere, said secondary radiating surface being shaped so that the value of the projected solid angle of the aperture with respect to any point of said secondary radiating surface is substantially equal to the value of the projected solid angle of the aperture with respect to points on the cavity primary radiating surface near the apex. 8. The simulator of claim 7 wherein the half angle of the apex is in excess of 40.degree.. 9. The simulator of claim 1 wherein the secondary radiating surface comprises a portion of a sphere, said secondary radiating surface being shaped so that the value of the projected solid angle of the aperture with respect to all points of said sphere portion is substantially equal to the value of the projected solid angle of the aperture with respect to points on the cavity primary radiating surface. 10. The simulator of claim 9 wherein the half angle of the apex is in excess of 40.degree.. 11. The simulator of claim 3 wherein the half angle of the apex is in excess of 40.degree.. 12. The simulator of claim 3 wherein the secondary radiating surface comprises a portion of a sphere, said secondary radiating surface being shaped so that the value of the projected solid angle of the aperture with respect to all points of said sphere portion is substantially equal to the value of the projected solid angle of the aperture with respect to points on the cavity primary radiating surface. 13. The simulator of claim 12 wherein the half angle of the apex is in excess of 40.degree..
	description	The embodiments of the present invention will be described below with reference to the views of the accompanying drawing. First Embodiment FIG. 4 schematically shows the internal structure of the gantry of an X-ray computed tomography apparatus according to the first embodiment of the present invention. FIG. 5 is a block diagram showing the circuit arrangement of the X-ray computed tomography apparatus according to the first embodiment of the present invention. The same reference numerals as in FIG. 4 denote the same parts in FIG. 5. A gantry 7 is the main structure of the X-ray computed tomography apparatus for acquiring multi-directional projection data about an object. The gantry 7 has a stationary portion 8 and ring-like rotating ring 10. The rotating ring 10 is supported on the stationary portion 8 so that it can rotate about a rotation axis RA. A motor (not shown) is used to rotate the rotating ring 10 at a speed as high as less than one sec per rotation. With this operation, the rotating ring 10 undergoes displacement relative to the stationary portion 8. An X-ray tube 12 for generating X-rays in the form of a fan is mounted on the rotating ring 10. In addition, an X-ray detector 16 is mounted on the rotating ring 10 to detect X-rays that are generated by the X-ray tube 12 and transmitted through an object 14. Typically, the X-ray detector 16 complies with multichannel specifications. A DAS (Data Acquisition System) 18 is also mounted on the rotating ring 10. The DAS 18 amplifies a weak electrical signal output from the X-ray detector 16 and converts the amplified electrical signal into a binary (1 and 0) digital signal. Note that a signal output from the DAS 18 will be referred to as projection data. This projection data is transmitted to the stationary portion 8 side through a noncontact type signal transmission device 19. An image data generating unit 25 reconstructs tomographic data about the object on the basis of the transmitted projection data. A monitor 27 visualizes the tomographic data. The noncontact type signal transmission device 19 is configured to perform noncontact transmission of projection data from the rotating ring 10 side to the stationary portion 8 side by using light. For this purpose, the noncontact type signal transmission device 19 includes a plurality of light-emitting diodes 1 and a plurality of light-receiving devices 5. Typically, the light-emitting diode 1 is a light-emitting diode, and the light-receiving device 5 is a photodiode. As shown in FIG. 6, the light-emitting diodes 1 are arranged at predetermined intervals on the outer surface of the rotating ring 10. This interval is set such that the irradiation area from one light-emitting diode 1 overlaps that from another adjacent light-emitting diode 1. The photodiodes 5 are arranged at predetermined intervals on the inner surface of the ring of the stationary portion 8 to oppose the light-emitting diodes 1. The noncontact type signal transmission device 19 also includes a plurality of LED drivers 23 for driving the light-emitting diodes 1 to simultaneously turn them on/off in accordance with projection data, and a data distributor 20 for distributing projection data to the LED drivers 23. The LED drivers 23 and data distributor 20 are mounted on the rotating ring 10. Each LED driver 23 turns on the light-emitting diode 1 when, for example, projection data is xe2x80x9c1xe2x80x9d, and turns it off when the projection data is xe2x80x9c0xe2x80x9d. The light emitted from the light-emitting diode 1 is incident on the photodiode 5. The photodiode 5 detects the incident light and generates an electrical signal having an amplitude corresponding to the amount of light received. The noncontact type signal transmission device 19 further includes a circuit (not shown) for binarizing the electrical signal output from the photodiode 5 and reconstructing the projection data. This reconstruction circuit is mounted on the stationary portion 8. The noncontact type signal transmission device 19 also has a plurality of beam condensing devices 3. The beam condensing devices 3 are respectively provided for the pairs of light-emitting diodes 1 and photodiodes 5. The beam condensing devices 3 are cylindrical lenses, Fresnel lenses, or curved mirrors, typically cylindrical lenses each having a shape concentrically curved with respect to the rotating ring 10. FIG. 7 shows the optical mechanism of the cylindrical lens 3. The cylindrical lens 3 has the function of condensing light from the light-emitting diode 1 in a direction (Zxe2x80x2-axis) substantially perpendicular to the rotational orbit (Yxe2x80x2-axis). The cylindrical lens 3 does not have a function of condensing light from the light-emitting diode 1 or it has the function of diffusing light in a direction substantially parallel to the rotational orbit (Yxe2x80x2-axis). When the light sent onto the lens 3 is viewed from the rotation axis direction of the ring 10, the light from the light-emitting diode 1 diverges in the form of a fan. This light also diverges in the form of a fan after passing through the lens 3. That is, when the traveling direction of light from the light-emitting diode is considered with respect to the Yxe2x80x2 direction and Zxe2x80x2 direction, respectively, the traveling direction of light from the light-emitting diode 1 does not change with respect to the Yxe2x80x2 direction regardless of the lens 3. With respect to the Zxe2x80x2 direction, however, the traveling direction of light from the light-emitting diode 1 changes in the direction in which the light is condensed by the lens 3. Therefore, the light from the light-emitting diode 1 is not condensed to one point but is condensed in a linear or belt-like form along the orbit of the photodiode 5. The condensing function of the cylindrical lens 3 makes it possible to ensure a relatively large light reception amount even if the photodiode 5 is located relatively far from the light-emitting diode 1. With the cylindrical lens 3, therefore, even light that does not strike the effective light-receiving surface of the photodiode 5 without the cylindrical lens 3 can be sent onto the effective light-receiving surface of the photodiode 5. The positional relationship between the light-emitting diode 1, the cylindrical lens 3, and the photodiode 5 is set as follows. For example, as shown in FIGS. 7 and 8A, the positional relationship between these three components is set such that the photodiode 5 is irradiated with light from the light-emitting diode 1 within an area CL1 having a width smaller than the effective light-receiving surface (EW) of the photodiode 5. In this case, the photodiode 5 is positioned at or close to a point F to which light is condensed by the cylindrical lens 3. With this positioning, almost all light is received by the photodiode 5 in the Zxe2x80x2-axis direction. Therefore, the amount of light received increases. As showing FIG. 8B, if some mechanical error (a mounting error and displacement in the rotational orbit in the Zxe2x80x2 direction) or some photodiode position variation in the Zxe2x80x2 direction (in this case, photodiode 5 are mounted in a inclined line to the light emitting diode line) occurs, the irradiation area CL1 may fall outside the effective light-receiving surface of the photodiode 5 and may receive no light. For example, in FIG. 8B, photodiode 5c can""t receive light, in this case, the communication is broken. The positional relationship between the three components which is set to solve this problem will be described next. As shown in FIGS. 9 and 10, the positional relationship between the three components is set such that the photodiode 5 is irradiated with light from the light-emitting diode 1 within a belt-like area BL1 having a width BW substantially equal to or larger than the width EW of the effective light-receiving surface of the photodiode 5. In this case, the point F is positioned farther from the light-emitting diode 1 than the photodiode 5. The positional relationship between the three components is set such that the width of the belt-like irradiation area BL1 becomes larger than, for example, the width of the effective light-receiving surface of the photodiode 5 by a mechanical error (a mounting error or displacement in the rotational orbit in the Zxe2x80x2 direction) or a photodiode position variation in the Zxe2x80x2 direction. In this case, the cylindrical lens 3 is preferably mounted on the ring of the stationary portion 8. With this positional relationship, allowance with respect to a mechanical error such as a mounting error or rotation displacement or a photodiode position variation in the Zxe2x80x2 direction increases as compared with the case shown in FIG. 7. In FIG. 7, photodiodes 5a, 5b can receive light, in FIG. 10, photodiodes 5a, 5b, 5c, 5d and 5e can receive light. As shown in FIG. 11, the positional relationship between the three components may be set such that the photodiode 5 is irradiated with light within the above belt-like area BL1. In this case, the point F is positioned between the lens 3 and the photodiode 5. With this positional relationship, a certain amount of light received can be ensured even with some mechanical error such as a mounting error or rotation displacement or a photodiode position variation in the Zxe2x80x2 direction. In this case, the cylindrical lens 3 is preferably mounted on the rotating ring 10. As described above, according to this embodiment, the light reception amount can be increased (the occurrence ratio of transmission errors can be decreased) within the allowable ranges of photodiode position variation in the Zxe2x80x2 direction and rotation offsets of the rotating ring 10. That is, a reduction in the amount of light received by each photodiode 5 can be suppressed by substantially condensing light emitted from the light-emitting diode 1 onto the orbit of the photodiode 5, even if the amount of light emitted from the light-emitting diode 1 decreases. Even if, therefore, the amount of light emitted from the light-emitting diode 1 decreases due to an increase in the frequency of a transmission signal, an increase in communication error ratio can be suppressed. In addition, since light from the light-emitting diode 1 is not condensed to one point on the orbit but is condensed to the entire orbit, each photodiode 5 can always receive light while moving on the orbit. This makes it possible to continuously transmit signals with small numbers of light-emitting diodes 1 and photodiodes 5. Second Embodiment FIG. 13 shows the arrangement of a noncontact type signal transmission device according to the second embodiment of the present invention. The same reference numerals as in FIG. 6 denote the same parts in FIG. 13. In the first embodiment, the light-emitting diodes 1 are arranged on the rotating ring 10, and the photodiodes 5 are arranged on the stationary portion 8. In the second embodiment, light-emitting diodes 1 are mounted on a rotating ring 10, and photodiodes 5 are mounted on a stationary portion 8. Fresnel lenses 33 are used as beam condensing devices. The Fresnel lenses 33 are mounted on the stationary portion 8, together with the light-emitting diodes 1. FIG. 14A is a sectional view of the Fresnel lens 33 used in this embodiment. FIG. 14B is a front view of this lens. A general Fresnel lens is made up of a plurality of annular lenses. In this embodiment, however, each Fresnel lens 33 is made up of a plurality of belt-like lenses each having a linear shape instead of an annular shape. As shown in FIG. 14A, each Fresnel lens 33 has a sawtooth-like cross-sectional shape (the oblique portions of the respective teeth are not linear but have the same curvature). In addition, as shown in FIG. 14B, when viewed from the front side of each Fresnel lens, strips each having a predetermined width are arranged parallel. This Fresnel lens 33 is thinner than the cylindrical lens 3 in the first embodiment and has a similar beam condensing function. With the Fresnel lenses, therefore, the same effects as those of the first embodiment can be obtained. In addition, since the Fresnel lenses are thinner than the lenses in the first embodiment, a reduction in weight and improvement in heat dissipation characteristics can be attained. As shown in FIG. 15, the Fresnel lenses 33 may be mounted on the rotating ring 10, together with the photodiodes 5. Third Embodiment As beam condensing means, curved mirrors, e.g., elliptic mirrors, are used instead of lenses. The elliptic mirrors are not disposed between light-emitting diodes and photodiodes but are disposed behind the light-emitting diodes or photodiodes. FIG. 16 is a perspective view showing the shape of an elliptic mirror and the position of a light-emitting diode. A light-emitting diode 1 is disposed in an elliptic mirror 35 and emits light toward the mirror surface of the elliptic mirror 35. A shielding plate 55 is disposed to be perpendicular to the generatrix of the elliptic mirror 35. FIG. 17 shows the positions of the light-emitting diode 1 and a photodiode 5 with respect to the elliptic mirror 35. The light-emitting diode 1 is positioned at one focal point of the elliptic mirror 35, and the photodiode 5 is disposed at a position slightly farther from the light-emitting diode 1 than the other focal point of the elliptic mirror 35. Light emitted from the light-emitting diode 1 is reflected by the elliptic mirror 35 and condensed to the other focal point. The reflected light converges first to the focal point and then diverges to reach the photodiode 5. FIG. 18 shows the light condensed to the belt-like irradiation area when viewed from the rear side of the elliptic mirror. In this embodiment using the elliptic mirrors 35, light emitted from each light-emitting diode 1 is condensed onto one line before the orbit of the photodiode 5, and then diverges to be condensed, as light having a belt-like irradiation area 75, onto the orbit of the photodiode 5 as in the first embodiment using the cylindrical lenses. Note that the shielding plates 55 perpendicular to the generatrix of the elliptic mirror 35 are disposed on the right and left ends of the elliptic mirror 35 to suppress the diffusion of light in the generatrix direction, thereby preventing crosstalk. Each elliptic mirror may be disposed behind the corresponding photodiode when viewed from the light-emitting diode. In this case, the light-emitting surfaces of the light-emitting diodes and the light-receiving surfaces of the photodiodes are located in the opposite directions to those in the third embodiment. By substantially condensing light emitted from the light-emitting diode 1 onto the orbit of the photodiode 5 by using the elliptic mirror, the same effects as those of the first embodiment can be obtained. The elliptic mirror is disposed behind the light-emitting diode when viewed from the photodiode, or behind the photodiode when viewed from the light-emitting diode. For this reason, the interval between the light-emitting diode and the photodiode can be reduced as compared with the first and second embodiments in which the lens is disposed between the light-emitting diode and the photodiode. This makes it possible to reduce the size of the apparatus. In the use of elliptic mirrors, as in the first and second embodiments, the light-emitting diodes or photodiodes can be arranged on the rotating portion or stationary portion. In addition, the elliptic mirrors can be arranged on the rotating portion or stationary portion like the cylindrical lenses and Fresnel lenses used in the first and second embodiments. If light emitted from each light-emitting diode is substantially condensed onto the orbit of a corresponding photodiode, the same effects as those of the first embodiment can be obtained, regardless of the positions of light-emitting diodes, photodiodes, and elliptic mirrors. In each embodiment described above, light emitted from a light-emitting means is substantially condensed onto the orbit of a light-receiving means by using one beam condensing means. However, the present invention is not limited these embodiments. Light may be condensed by using two or more beam condensing means. For example, light emitted from a light-emitting means light may be collimated by the first beam condensing means, and this collimated beam is sent onto the second beam condensing means to make the second beam condensing means substantially condense the collimated beam onto the orbit of the light-receiving means. The present invention can be applied to a case wherein both the light-emitting means and the light-receiving means move as well as a case wherein only one of the light-emitting means and the light-receiving means moves. The case in which both the light-emitting means and the light-receiving means move includes not only a case wherein the light-emitting means and light-receiving means move in different directions but also a case wherein they move in the same direction at different moving speeds. Furthermore, these means may move on a straight line or circumference. Each light-emitting means may be formed by only an electrooptic conversion element for generating light modulated in accordance with a signal obtained by coding information to be transmitted or may be made up of a combination of an element that keeps emitting light regardless of the signal and an element for modulating the luminance or the like of the transmitted light in accordance with the signal. The electrooptic conversion element includes a laser diode in addition to a light-emitting diode. The element for modulating transmitted light includes a liquid crystal polarizing plate. Modulated light may be sent onto the light-receiving means through a medium that transmits light instead of being directly sent onto the light-receiving means. The medium for transmitting light includes an optical fiber. The light-receiving means may be formed by only an element (optoelectric conversion element) for detecting the modulation of received light and converting the light into an electrical signal, or may be made up of an optoelectric conversion element and a medium for transmitting received light to the optoelectric conversion element. The optoelectric conversion element includes a phototransistor and photocell in addition to a photodiode. The beam condensing means includes a curve mirror other than an aspherical lens and elliptic mirror as well as a cylindrical lens, Fresnel lens, and elliptic mirror. The case wherein the position of the light-receiving means changes relative to the light-emitting means and beam condensing means includes a case wherein the moving directions and speeds of the light-emitting means and beam condensing means differ from those of the light-receiving means. Likewise, the case wherein the position of the light-emitting means changes relative to the light-receiving means and beam condensing means includes a case wherein the moving directions and speeds of the light-receiving means and beam condensing means differ from those of the light-emitting means. When the number of light-emitting means differs from that of light-receiving means, the beam condensing means are preferably disposed on the minority side. This arrangement requires a smaller number of beam condensing means, and hence makes it possible to facilitate design and manufacture and attain a reduction in cost and the like. 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.
052001385	description	DETAILED DESCRIPTION OF THE INVENTION In the following description, like reference characters designate like or corresponding parts throughout the several views of the drawings. Also in the following description, it is to be understood that such terms as "forward", "rearward", "left", "right", "upwardly", "downwardly", and the like are words of convenience and are not to be construed as limiting terms. In General Referring now to the drawings, and particularly to FIG. 1, there is illustrated a nuclear fuel assembly, represented in vertically foreshortened form and being generally designated by the numeral 10, that can incorporate a spectral shift-producing subassembly, generally designated 12, of the present invention which will be described later on. The fuel assembly 10 is the type used in a pressurized water reactor (PWR) and basically includes a lower end structure or bottom nozzle 14 for supporting the fuel assembly on the lower core plate (not shown) in the core region of a nuclear reactor (not shown), and a number of longitudinally extending guide tubes or thimbles 16 which project upwardly from the bottom nozzle 14. The fuel assembly 10 further includes a plurality of transverse grids 18 axially spaced along the guide thimbles 16, and an organized array of elongated nuclear fuel rods 20 transversely spaced and supported by the grids 18. Also, the fuel assembly 10 has an instrumentation tube 22 located in the center thereof and an upper end structure or top nozzle 24 attached to the upper ends of the guide thimbles 16. With such an arrangement of parts, the fuel assembly 10 forms an integral unit capable of being conventionally handled without damaging the assembly parts. As mentioned above, the fuel rods 20 in the array thereof in the assembly 10 are held in spaced relationship with one another by the grids 18 spaced along the fuel assembly length. Each fuel rod 20 includes nuclear fuel pellets (not shown) and the opposite ends of the fuel rod 20 are closed by upper and lower end plugs 26, 28. The fuel pellets composed of fissile material are responsible for creating the reactive power of the PWR. A liquid moderator/coolant such as water, or water containing boron, is pumped upwardly through the fuel assemblies of the core in order to extract some of the heat generated therein for the production of useful work. Spectral Shift-Producing Subassembly In the operation of a PWR it is desirable to prolong the life of the reactor core as long as feasible to better utilize the uranium fuel and thereby reduce fuel costs. To attain this objective, it is common practice to provide an excess of reactivity initially in the reactor core and, at the same time, provide means to maintain the reactivity relatively constant over its lifetime. The present invention relates to such means in the form of the spectral shift-producing subassembly 12 having a plurality of hermetically-sealed hollow tubular empty rodlets 30 inserted in the guide thimbles 16 of the fuel assembly 10, as shown in FIG. 1. The sealed empty rodlets 30 of the subassembly 12 are stationarily supported in the fuel assembly 10 by a mounting means in the form of a holddown mechanism 32. The sealed empty rodlets 30 are capable of displacing moderator water while in their sealed condition within the fuel assembly 10. The holddown mechanism 32 supports the rodlets 30 in the guide thimbles 16 of some of the fuel assemblies 10 in the core to assist in controlling reactivity over the life of the core. As best seen in FIGS. 2-4, the holddown mechanism 32 of the spectral shift-producing subassembly 12 supports the water displacement rodlets 30 in generally parallel, spaced side-by-side relationship. The holddown mechanism 32 includes a lower flat perforated support plate 34 which fits within the fuel assembly top nozzle 24 and rests on a lower adapter plate 36 of the top nozzle 24. The holddown mechanism 32 also includes a central sleeve 38, being attached at its lower end within a central opening 40 in the support plate 34 and extending upwardly therefrom, and an upper holddown plate 42 which receives the central sleeve 38 and is slidable vertically along it. Further, a holddown coil spring 44 is disposed about the central sleeve 46 and extends between the lower support plate 34 and the upper holddown plate 42. Thus, the support plate 34 is held down against the top nozzle lower adapter plate 36 by the coil spring 44 which is compressed by the upper core plate (not shown) acting through the upper holddown plate 42 which abuts the upper core plate. This arrangement assures that the water displacement rodlets 30 which are attached to the holddown support plate 34 cannot be ejected from the reactor core by coolant flow forces while any thermal growth of the rodlets 30 is accommodated. Turning next to FIG. 4 as well as FIG. 2, there is shown one embodiment of the water displacement rodlet 30 of the spectral shift-producing subassembly 12 of the present invention. The rodlet 30 is hermetically sealed at its opposite ends. The rodlet 30 basically includes an elongated hollow empty tube 46 having an elongated annular (preferably, cylindrical) wall 48, and opposite upper and lower end plugs 50, 52 hermetically sealed to the opposite ends of the tube 46. The upper end plug 50 includes a threaded upper end 50A and an enlarged diameter annular collar 50B spaced below it for facilitating attachment of the rodlet 30 to the holddown support plate 34 of the holddown mechanism 32. The tube 46 and end plugs 50, 52 can be composed of any suitable material, such as zirconium-based alloy. The tube wall 48 of the rodlet 30 has a weakened section in the form of an axially-extending annular wall section 54 of reduced thickness compared to the thickness of the remainder of the wall 48 of the tube 46. The reduction in the thickness of the wall section 54 of the rodlet 30 adapts it to creep collapse and rupture after a desired extended period of use in the nuclear reactor permitting moderator to enter and fill the empty rodlet. In such manner, the displacement of water by the rodlet 30 is produced resulting in an increase in the water/fuel ratio and thereby an increase in reactivity through the occurrence of a spectral shift. Referring to FIGS. 5-7, the respective reduced thicknesses of the axial wall sections 54A, 54B of first and second groups of the rodlets 30A, 30B are different to adapt the rodlets 30A, 30B to rupture at different times and permit water to enter the rodlets at different times to produce an incremental increase in the water/fuel ratio and thereby an incremental increase in reactivity. The rodlets 30A, 30B can also have different levels of internal pressurization, such as by helium gas, to initiate rupture at different times. The axial length of the thinned wall sections is small in comparison to the overall length of the rodlet 30. As an example, the rodlet 30 can be the same length as a nuclear fuel assembly, whereas the wall section 54 can be only six inches in length. The outside diameter of the rodlets 30 is the maximum amount possible to permit the rodlets to fit in the guide thimbles 16 and still not interfere with the guide thimble so as to create problems during removal of the subassembly 12 during refueling. The reduced thicknesses and pressurization of the rodlets 30 would be preset such that the ruptures occur sometime between the middle and the end of the reactor fuel cycle. The increase in water in the guide thimbles 16 after the rodlets 30 fail results in about a 6% change in the H/U ratio which corresponds to a 3% decrease in fuel cycle costs. The 3% decrease in fuel cycle cost is equivalent to $45-$60 kg U fabrication cost improvement. It should be noted that the present invention is very tolerant to some of the spectral shift-producing rodlets not failing during the cycle or failing somewhat sooner or later than desired since the overall gross effect is what is desired and small changes do not significantly affect either safety or economics. It is thought that the present invention and many of its attendant advantages will be understood from the foregoing description and it will be apparent that various changes may be made in the form, construction and arrangement thereof without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the form hereinbefore described being merely a preferred or exemplary embodiment thereof.
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