text:   arms for the Einstein Telescope",8,"['New paper on the arxiv about the #EinsteinTelescope (ET) design, led by Sam Rowlinson (from @UoBIGWaves). <LINK> 1/8 <LINK>', 'The Einstein Telescope (https://t.co/eY4VS6y0PY, ET) is a proposed gravitational wave observatory, with substantial improvements, allowing us to detect new types and more gravitational waves 2/8 https://t.co/NZ9BJ7a1fv', 'For optimal sensitivity the observatory will be a triangle shape (instead of an L) compromising of 6 interferometers! Each side will be 10 km (instead of 3km used by @ego_virgo and @KAGRA_PR and 4km used by @LIGO). 3/8 https://t.co/RhFMQB5SJF', 'Because the arm is very long, the laser beam will be very wide when it exits the ""arm cavity"" (where the gravitational wave interacts with the light). This ""wide"" laser beam must be reduced in size so it can be matched to the laser 4/8 https://t.co/b3CrfMxwpD', 'We design a telescope to reduce the size of this laser beam to an intermediate size as soon as it exits the arm. This allows the use of a smaller beamsplitter (saving money) and has a number of other technical advantages 5/8 https://t.co/a32NlZkZBD', 'These include: decoupling the effects of beam jitter; steering the ""cold"" and ""hot"" beams around each other, allowing good placement of beams in the tunnels. The size is chosen by a tradeoff analysis considering the effects of thermal lensing and thermal noise. 6/8', 'The paper closes with a discussion about which parameters can be ""tuned"" without changing the overall design, based on further studies. 7/8 https://t.co/9LzHGFV2G2', 'Lastly, all of this work was completed with the open-source software Finesse3 (https://t.co/aeqTWD1Kbi)! 8/8']",20,11,1514