ISC Meeting on 2017/7/31 14:00 - 15:00

Participants: (eZuce meeting)

Next meeting

2017/9/11 14:00 - 15:00 ?? (August 14 is a holiday, August 28 is F2F)

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Agenda

• bKAGRA sensitivity update [Komori]
  • thermal noise calculation error corrected, substrate absorption 30ppm/cm

    • latest EO approved estimated sensitivity is in JGW-G1605698, but this has error in the code

  • torsion modes of blade springs could complicate the suspension thermal noise

  • heat absorption budget

    • substrate absorption 30 ppm/cm, coating absorption 0.5 ppm
    • heat from coils [Miyamoto]

      • 2.2 mW (see ActuatorDesign wiki)

    • heat from apertures 50 mW? (Sakakibara CQG 2015)

• PSL EOM Layout re-consideration [Enomoto] (JGW-T1706748)

  • Delay-line length decided to be 2.66 m (instead of 8.88 m)
  • Modulation phase between f1 AM and PM is always aligned (we need this to be aligned)

  • Modulation index needed at each EOM is less than measured maximum index by Uehera (JGW-T1605611)

  • Optickle simulation by Kohei Yamamoto
    • simulation on imperfections (MZ arm asymmetry, MZ lock, EOM phase difference control etc.)
    • start with hand calculation, simple setups, and then to full IFO simulation
  • Requirement on carrier power loss?
  • Comment from Stefan Ballmer
    • Similar calculation was done in LIGO in the past. Displacement noise requirement for MZ was tough (~1e-14 m/rtHz).
    • Any in-air interferometer suffer from jitter and frequency noise which cannot be suppressed.
• OFI and OMC status? [Somiya]
  • look for OFI with larger aperture [Somiya]
  • output optics task sharing status?
  • OMC baseplate issue?

  • design review on June 26 at Titech (JGW-G1706853,JGW-G1706854), layout review on July 3

    • OMC suspension (Flipped optics or not? 3 or 4 wires? 2 or 1 DC PD? How to damp and actuate pendulum?), OFI suspension
  • frame resonant frequency should be fixed based on vibration isolation requirements
  • frame should be made like Bosch frame (screws screwed in the direction of pillars are bad!)
  • flipped OMC is inconvenient for alignment
  • put beam dumps as much as possible on OMC

  • Somiya and Kasuya visit Koji's OMC lab (Amaldi at Caltech)

    • Current OMC design is optimized for BAE, but BAE is far future. Why don't we make compact lower finesse OMC first. It is also better for squeezing. Squeezing or balanced homodyne sounds feasible than BAE using contrast defect.
      • prototype OMC could have some constraints from the mode-matching
    • aLIGO spare OMC production should start in 2017. Send students?

• Actuator noise modeling [Michimura,Miyamoto] (JGW-T1503453)

  • Updated magnet size for cryopayload marionette (ActuatorDesign wiki)

  • Updated lock acquisition section to derive velocity requirements for suspensions (see ISC Meeting minutes 20170410) [Michimura]

  • Magnetic noise calculation updated (JGW-T1504459) [Shimoda]

    • Added torque effect on magnets
  • Needs to implement frequency noise, but FSS modeling with ALS is complicated [student!]

  • Discuss mirror vibration from heat link

    • Meeting on July 14 [Yamada, Miyamoto, Ushiba, Michimura]

• bKAGRA Phase 1 initial alignment / commissioning plan [Michimura]: JGW-T1605692

  • Fixed mirrors for AS port (including SR2)
  • Some comments from the Chief Meeting
    • Revised schedule seems compatible with PRMI. Why not?

      • PRMI is an option after achieving the Phase 1 goal, if it doesn't delay the final bKAGRA JGW-T1605595

    • Initial alignment does not interfere with ITM Type-A installation work?
    • Evacuation of IXC/IYC compatible with Type-A installation work?
    • Baffle PDs for initial alignment in vacuum
      • confirmed with Akutsu that he is thinking of putting PDs on narrow angle baffles
      • vibration isolation for baffle PDs necessary?
      • possibility of seeing beams with Tcam
• IR/green steering mirrors [Michimura] (see [kagra-isc 01649])
  • for POP/POS and green steering in PR2/SR2 chamber, needs picomotors and ~40 cm pedestals
  • need this by the end of August 2017 (after PR2 installation on June, before IR initial alignment starts on September)
  • proposed mirror specs
    • HR reflectivity: more than 99% for both 1064nm and 532nm
    • AR refectivity: less than 0.3 % for 1064nm, similar for 532nm
    • incient angle: 20-45 deg, s-polarization
    • radius of curvature: flat

      • should be something like: larger than *** km

        • λ/20 corresponds to RoC of 12 km (by company S)
    • size: 2-inch
    • wedge: 1 deg
    • substrate: Fused Silica
    • surface quality: λ/20, 0.1 nm rms roughness

  • MIF will pay

  • Ordered on July 19

• DC QPD holder [Michimura]

  • beam height should be 4inch to use similar mount, with small modification of spacer (instead of 3inch in JGW-D1402607)

    • RF PD, RF QPD boxes are designed for 4inch beam height
  • stages are not needed for ISC DC QPD

  • design new ones; they can be very simple [-> Michimura?]

  • calibration can be done in different ways
  • put strain relief and anchors for cables to protect QPD board

See this page for other agendas.