ISC Meeting on 2017/7/3 14:00 - 15:00

Participants: Hiro Yamamoto, Arai, Kokeyama, Akutsu, Aso, Izumi, Michimura (eZuce meeting)

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2017/7/31 14:00 - 15:00 (July 17 is a holiday)

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Minutes

Vibration from heat links
- information also needed for WAB
OMC 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)
DC QPD holder
- 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
bKAGRA sensitivity update
- torsion modes of blade springs could complicate the suspension thermal noise

Agenda

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
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
  - Ochi is measuring vibration of cryo-shield, which is different cryo system from the mirror
  - Yamada is measuring spring constant of heat links
  - Miyamoto has the cryopayload suspension model
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
  - size: 2-inch
  - wedge: 1 deg
  - substrate: Fused Silica
  - surface quality: λ/20, 0.1 nm rms roughness
DC QPD holder [Michimura]
- we are using oplev QPD (JGW-D1402411) for ISC DC QPD
- we will need QPD mounts for them, just like oplev QPD mount (JGW-D1503562)
- 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
bKAGRA sensitivity update
- quantum noise calculation was wrong (pointed out by Haino)
  - sign mistake, very slight effect on sensitivity
- suspension thermal noise calculation was wrong (pointed out by Komori)
  - strange behavior with respect to sapphire blade resonant frequency
  - temperature gradient treatment was wrong
- update on sapphire mirror temperature
  - ITM substrate absorption turned out to be ~30 ppm/cm (JGW-G1706429)
  - 80 ppm/cm was assumed in the last update, so mirror temperature was 23.1 K (JGW-G1605698)
- currently re-calculating the thermal noise, with non-equilibrium condition and less substrate absorption [Komori, Somiya, Ballmer, Michimura]

See this page for other agendas.