ISC Meeting on 2020/07/06 13:30 - 14:30

Participants: Kenta Tanaka, Shinji Miyoki, Haoyu Wang, Eleonora Caposaca, Kiwamu Izumi, Koji Nagano, Masayuki Nakano, Matteo Leonardi, Osamu Miyakawa, Ryutaro Takahashi, Kentaro Somiya, Tomotada Akutsu, Yoichi Aso, Yuta Michimura

Zoom meeting: https://zoom.us/j/5045179604

Your time zone: https://www.timeanddate.com/worldclock/fixedtime.html?iso=20200706T0430

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When necessary (New meeting slot: bi-weekly Mondays, from 13:00 JST)

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Minutes

• Video record of the meeting: JGW-T2011793

• Summary of current measurements so far
  • LSC sensing matrix, measurements vs simulation
    • The parameter choice of "BRSE_SDMR1_17_45" is OK for the Optickle simulation.
      • SDMR1 means single demodulation, using REFL_1I for CARM.
    • POP17Q (MICH error signal) seems to have too much DARM contribution.
      • Although DARM displacement is much smaller than MICH displacement and may be negligible, MICH feedforword would spoil DARM if DARM to MICH coupling is too large
      • DARM excitation was done by injecting signal at DARM error point, when DARM was fed back to both ETMs

    • A/I: Sensing matrix re-measurement with

      • Correct CARM calibration
      • Feedforword off (probably already done with FF off, but need to double check)
      • Measurement for both I-phase and Q-phase
  • Schnupp asymmetry

    • Result from time of flight measurement (3.36(1) m, klog #14575) and that from laser frequency modulation measurement (0.56 m klog #14541) are inconsistent

      • There might be an error in BS calibration, laser frequency calibration and/or calculations
        • ETM calibration starting from free-swinging Michelson and Pcal ETM calibration seems to be consistent
        • Laser frequency calibration using ALS AOM and Pcal ETM calibration seems to be consistent
        • Calculations are confirmed independently by Keiko and Masayuki

      • A/I Check the calculations again

  • PRC length measurements
    • Time of flight measurement would be possible if you use AS beam

    • A/I PRY length measurement to be done once IFO is recovered

  • OMC scan to see mode content of AS beam

    • Carrier and f1 HOM3 mode seems to be overlapped (see usb3 in klog #14691 omcmodes.pdf)

      • When designing OMC with "Sam Waldman method", higher order modes of the sidebands were not taken into account
        • FINESSE simulation with TWE maps with sideband higher order modes give negligible shot noise increase and thought it is OK. But now we have birefringence and maybe the situation is different.
      • Possible effects are the shot noise increase and RF intensity noise coupling
        • Changing DARM offset didn't changed the shot noise, which suggests that shot noise from f1 HOM3 is not dominating now

        • A/I Check with simulations

      • Possible solutions
        • Better alignment (current aligntment is actually not so bad though)
        • Somehow tune macroscopic OMC cavity length
        • Reduce modulation depth
• Birefringence simulations with FINESSE
  • Haoyu started some simulations with directional BS
  • How to combine s- and p-pol power to set the operating point is to be investigated
    • May be setting the operating point with s-pol only is OK since we have IFI for REFL and OFI for AS
  • Right now with transmission map (amplitude map) only. Transmission phase maps for both s-pol and p-pol also need to be included.
  • Peak splitting observed seems to be consistent, considering PRM-messy MICH-PRMp coupled cavity
• New ISC member

  • Kenta Tanaka (ICRR) -> added to kagra-isc mailing list

• New ISC meeting slot
  • Bi-weekly Mondays, from 13:00 JST

Agenda

• RECORD THE MEETING
• Summary of current measurements so far
  • LSC sensing matrix, measurements vs simulation

    • Optickle simulation: https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=11767

      • Parameter choice of "BRSE_SDMR1_17_45" OK?

    • Measurements: https://klog.icrr.u-tokyo.ac.jp/osl/?r=14515, https://klog.icrr.u-tokyo.ac.jp/osl/?r=14593

  • Schnupp asymmetry measurements

    • Time of flight measurement successful https://klog.icrr.u-tokyo.ac.jp/osl/?r=14575

  • PRC length measurements

    • PRY length: 68.28 m with the error of roughly 1 m (designed: 64.926 m) https://klog.icrr.u-tokyo.ac.jp/osl/index.php?r=14555

    • PRX length: about 68 m (designed: 68.2559 m) https://klog.icrr.u-tokyo.ac.jp/osl/?r=14633

    • Actuator efficiency inconsistent between measurements?
  • OMC scan to see mode content of AS beam

    • Summary http://klog.icrr.u-tokyo.ac.jp/osl/?r=14696

    • carrier and f1 3rd mode is overlapped? http://klog.icrr.u-tokyo.ac.jp/osl/?r=14620

  • Frequency noise coupling

    • https://klog.icrr.u-tokyo.ac.jp/osl/?r=14614

  • Arm cavity round-trip loss measurement with birefringence effect correctly taken into account

    • P-pol and S-pol PDs placed on POS table https://klog.icrr.u-tokyo.ac.jp/osl/?r=14622

• Birefringence simulations with FINESSE
  • Any volunteer to add polarization to FINESSE code?
  • "directional beamsplitter" could be used to simulate DRFPMI with FINESSE using s/p two-world approach [Haoyu]

    • https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=11792

• New ISC meeting slot?
  • Bi-weekly SEO and Chief meeting on Modays, from 15:00 JST
  • How about bi-weekly Mondays 13:00 JST (before chief meetings)

Copy from previous meeting

• Simulation activities necessary
  • LSC and ASC simulations with current ITMs and current interferometer setup
    • Especially LSC simulations not done for PRFPMI and DRMI, and 3f locking
    • Compare measured LSC and ASC sensing matrices with simulations
    • Compare measured recycling gain (for carrier and sidebands) with simulations
    • Compare measured AS mode content with simulations
    • Compare measured MICH/PRCL/SRCL controls noise coupling with simulations
    • Compare measured intensity/frequency noise coupling with simulations
  • Thermal lensing in BS
• Measurements necessary to do simulation work
  • PRC (SRC) length and Gouy phase
  • Schnupp asymmetry
  • modulation depth (arm cavity scan)
  • arm cavity length (arm cavity scan)

  • arm cavity round-trip loss measurement with birefringence effect correctly taken into account (with PBS at POP/POS and TRX/TRY) JGW-T2011633

  • Power recycling gain for carrier and sidebands
  • Throughput from IMC output to AS RF, OMC DC, REFL, POP, TRX, TRY
• Measurements necessary to compare the result with simulation
  • frequency/intensity noise coupling, down to ~10 Hz
  • Measure power recycling gain for sidebands (POP 2f with FPMI locked and PRFPMI locked)
  • DRFPMI LSC and ASC sensing matrix

    • LSC https://klog.icrr.u-tokyo.ac.jp/osl/?r=14515

  • MICH/PRCL/SRCL to DARM coupling
  • Measure MICH contrast defect with MICH locked and FPMI locked
  • OMC cavity scan to scan mode content of AS beam

  • https://docs.google.com/spreadsheets/d/1w4q8OvX9E6nkYSgshLYLoZH5yvQXHvGmL1agux8ztx0/edit#gid=0

  • Type-A, B, Bp actuation efficiency measurements (for actuator noise)