= ISC Meeting on 2021/04/13 13:00 - 15:00 = Participants: Satoshi Tanioka, Kenta Tanaka, Naoki Koyama, Chiaki Hirose, Kentaro Somiya, Kiwamu Izumi, Koji Nagano, Marc Eisenmann, Masayuki Nakano, Naoki Aritomi, Shoichi Oshino, Tomotada Akutsu, Yua Michimura Zoom meeting: https://zoom.us/j/6676627462 Your time zone: https://www.timeanddate.com/worldclock/fixedtime.html?iso=20210413T0400 === Next meeting === TBD [[LCGT/subgroup/ifo/ISC/Meetings|back to Meetings page]] == Minutes == * Interferometer alignment [[https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=12594|JGW-T2112594]] (Michimura) * For O4, ISS setup will be removed from IMMT1T table but IMMT1 oplev setup will remain. * We should take care if it affect IMMT1T QPD signals. * Dan Chen made some scripts to give the position of the beam in Tcam. * We might be able to use this to center the beam on ITMs and ETMs automatically. * The reason why we used BS in PRMI alignment instead of ITMY is because BS had more drift than ITMY. * In the OMC alignment actually, OSTM was used instead of OMMT1. * Kenta confirmed this by checking the guardian script. * TRX IR QPDs were actually investigated to see where the pitch-yaw coupling in the QPD signals comes from, but the issue was not solved * '''A/I''' Check if there's any klog reports * What do we do for the beam positioning on SRM? * In aLIGO, there was a QPD to monitor SRM transmission * In KAGRA, we might be able to use OMMT1 transmission * In KAGRA, we don't have an OFI before OMMT1, so we might suffer from back scattering * '''A/I''' Investigate if we can put a QPD (or two QPDs) * We can always use A2L for the beam positioning. * SRM HR camera should be there, but may be it is not useful especially after mid-Baffle installation * What can we do for the automation? * Use Tcam beam positioning script instead of using our eyeballs * Replace POP POM and POS POM with PZT mirrors instead of picomotors * The gouy phase separation between POP POM and PR3 (POS POM and SR3) is small. We might want to use PZT mirrors on POP/POS table. * Remember that POP POM and POS POM are put on a in-vac suspended table * Putting oplevs to POP POM and POS POM might be tough considering space available * Beam positions on PR2, PRM, IMMT2 are not controlled * BPC might not be useful in PRMI since signals are covered by frequency noise * Put cameras? * In aLIGO, beam position on PRM did not affected the sensitivity much * Gouy phase separation between IMMTs and PRs * In Xarm IR alignment, IMMT2 and PR2 were used, but IMMT2 was often skipped. This seemed to be from the degeneracy, but Gouy phase separation between two is ~19 deg, which seems to be enough. * Baffle PDs * They are not used any more, but it is always good to have extra sensors. * IMMT1 and OMMT1 were not used for the alignment. ITMY and SR3 was also not often used. * Fiber noise cancellation improvement plans for ALS [[https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=12769|JGW-T2112769]] (Tanioka) * The end mirror for the reference path drifts too much * Will be replaced * Resonant peaks of PZT limits the control bandwidth * PZT actuation range is small for long-term stability * Fiber temperature loop is there, but not enough * Use woofer and tweeter configuration * 45 deg incidence on PZT mirror gives coupling to alignment * Use AOM instead (in long term upgrade) * 0 deg incidence and put waist on the mirror * Change in the optical layout necessary * Use PBS to minimize the change in the optical layout? * Report from the site * IMC ASC simulation work started * Layout modifications of IMC optical tables started == Agenda == * Summary of interferometer alignment in O3GK and RSE commissioning [[https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=12594|JGW-T2112594]] (Michimura) * Discussion on how to proceed for O4 * Are we going to remove ISS setup at IMMT1T? * Any upgrades necessary for IMC ASC? * Can we automate the beam centering with Tcams for reproducibility? * Any thoughts on why PRMI alignment has to be done before Yarm alignment? * Are there better ways for daily alignment? * What are the steps necessary for engaging WFS/QPD loops in O4? * Other recent topics related to ISC * Fiber noise cancellation improvement plans for ALS [[https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=12769|JGW-T2112769]] (Tanioka) * Non-polarized beam splitter https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=10506 [Michimura] * IMC REFL: Thorlabs BSW11 are used (Ts=~40%) * IMC TRANS: Probably Thorlabs BSW11 are used * REFL: Note that p-pol is coming out from the chamber. Newport 10Q20HBS.33S (for s-pol) are used. Thin film polarizers are also used and there seems to be a confusion. * POP: Newport 10Q20HBS.33S (for s-pol) is used. S-pol/P-pol power ratio can be confused with this BS. * POS: No BS placed. * AS: p-pol is coming out from the chamber. We agreed to use HWP to make them s-pol and to use Newport 10Q20HBS.33S (for s-pol). But this solution might be confusing. * Planning to order non-polarized BS soon. * In-vac steering mirrors: https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=12592 [Michimura] * For some steering mirrors, p-pol beam * STM1, STM2, POM1, POM2 around IFI (PYD-20 is used) * steering mirrors after OFI * PYD-20 has a transmission * T < 70ppm at 0 deg for s-pol (measured) * T < 25ppm at 30 deg for s-pol (measured) * T < 5ppm at 45 deg for s-pol (measured) * T ~ 1000pppm at 45 deg for p-pol (specsheet) * Also, specs of POP_POM and POS_POM for IR p-pol needs to be investigated * Optical table cover for TRX/TRY and IMC REFL/IMC TRANS: [[KAGRA/subgroup/ifo/MIF/Minutes20210412|Review page]] [Michimura]