ISC Meeting on 2020/04/13 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

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Minutes

• Interferometer alignment 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 klog [Akutsu]

  • 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 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
    • 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 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 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: Review page [Michimura]