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External Review for interferometer alignment controls (August 2021)

Purpose

From February 25 to April 21, 2020, KAGRA performed its first observing run for 4 weeks with power-recycled Fabry-Perot-Michelson (PRFPMI) congifuration. The sensitivity during the April run with GEO600, dubbed O3GK, was at the binary neutron star range of 0.5-0.7 Mpc. From July 13 to October 13, we had an intense commissioning period to try locking the full resonant sideband extraction (RSE) interferometer. We had many achievements during that period, but we have never achieved the full RSE lock yet.

During the O3GK run and the RSE trial, we faced several issues related to the interferometer alignment. The sensitivity of KAGRA depended very much on the alignment, and the best sensitivity could be achieved only when the expert aligned the interferometer manually. Almost no alignment sensing and controls (ASC) loops where closed, except for a few dither alignment loops in the power recycling cavity (PRC).

The purpose of this External Review is to receive comments from LIGO/Virgo interferometer experts on our plans to improve such situations. We would like to know if the issues we are trying to solve are reasonable, and if our plans are sound. We would also like to find out what are the issues we haven't identified yet. Finally, we would like to prioritize the works in the order of importance for the full RSE lock with ASC.

Agenda

  1. Daily alignment of the interferometer
    • summary of O3-RSE trial situation and improvement plans
  2. Commissioning and simulations for alignment sensing and control
    • summary of current situation and plans, focus on global controls using wave front sensors (WFS) and QPDs
  3. Input mode cleaner alignment sensing and control report
    • report from current on-site works

Basics of KAGRA interferometer

1. Daily alignment of the interferometer

1-1. Summary of the current status

1-2. Known issues and our plans (highly uncertain)

  • Issue 1
    • Plans ...
  • Issue 2
    • Plans ...

1-3. Known issues and our plans (less uncertain)

2. Commissioning and simulations for alignment sensing and control

2-1. Commissioning status

2-2. Simulation status

  • Optickle

    • FPMI, PRFPMI, SRFPMI, DRFPMI (BRSE) sensing matrix simulations with imperfections done JGW-T1910359

    • PRMI, DRMI simulations not yet
  • FINESSE

    • For LSC without mirror maps, GUI for simulations with any interferometer configurations done JGW-T2012132

    • Working on ASC integration
    • Also input mode cleaner (IMC) ASC simulations and analytical calculations on going independently

2-3. Known issues and our plans (highly uncertain)

2-4. Known issues and our plans (less uncertain)

3. Input mode cleaner alignment sensing and control report

KAGRA/Subgroups/MIF/ExternalReview2021 (last edited 2021-08-26 00:30:15 by haoyu.wang)