ISC Meeting on 2018/3/26 14:00 - 15:00

Participants:

eZuce meeting: "KAGRA ISC Meeting" in the KEK community.

Next meeting

2018/4/9 (Mon) 14:00 - 15:00

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Minutes

Site report [Enomoto] JGW-G1808115
- ETMY damping
  - As for MN actuator cross-coupling issue, actuation efficiency check should also be done to check sign flip etc.
- ETMY DAC glitch
  - Converting 16 kHz foton file and 2 kHz foton file might not be so easy
  - 2 kHz might be OK for upper suspensions even at the late stages of KAGRA
- Alignment recover
  - IMC alignment drifts, at ~100 urad for MCi and MCo, mainly in pitch. MCe pitch won't compensate this drift. This suggests vertical shift of the cavity axis is not the main drift, which means PSL beam might not be the cause of drift.
  - Quantitative evaluation of beam spot drift and IMC alignment drift is necessary.
  - If PSL input pointing is really drifting, evaluation of the drift is necessary to estimate the actuation range of the PZT mirror at PSL.
Site report at ISC meetings
- Sounds useful
- Use klog entries as meeting materials as much as possible to reduce reporting work
- Encourage more people to attend ISC meetings
RF generation using Mach-Zehnder interferometer [Kohei Yamamoto]
- MZI displacement noise requirements can be met considering shot noise and seismic noise
- RF oscillator noise requirements for MZI should also be calculated

Agenda

Site report [Enomoto] JGW-G1808115
KAGRA configuration for early phase of bKAGRA JGW-T1707334
- SRM reflectivity
  - Mirror ordered
  - Black coating for metal mass?
- ITM asymmetry [Enomoto] JGW-T1707565
  - ITM asymmetry is OK for early stages, but asymmetric ITMs cannot be used for achieving design sensitivity
bKAGRA RF cables [Michimura] klog #4362
- purchased almost all the SMA cables, except for 30m cables
RF generation using Mach-Zehnder interferometer [Kohei Yamamoto] JGW-G1707309 JGW-G1807655 JGW-G1808029
- simulation on imperfections (MZ arm asymmetry, MZ lock, EOM phase difference control etc.)
- calculate requirements on MZI displacement, EOM modulation phase difference, EOM imbalance
- Requirements derived from full Optickle simulation and those derived from transfer function between displacement of MZI and sideband power kind of matched after implementing RAM into calculation for the latter. However, we need more investigation on the following issues:
  - Modulation depth for RAM generating EOM changes the requirement.
  - Spectrum shapes of the requirements for mid-fringe do not match. Maybe coming from accuracy of the mid-fringe?
  - Unknown frequency response of the transfer function from the displacement of MZI and sideband power
  - Check if caluculated RF oscillator amplitude noise is relative one or not with simple Optickle model
- calculations for requirements on delay line lock displacement noise, parallel EOM MZ lock displacement noise, EOM modulation phase difference, EOM imbalance on-going
- Relative f1 PM and f1 AM also needs to be adjusted (CQG 31, 095003 (2014)). Another EOM for f1 or relative amplitude adjuster between two EOMs?
- 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.
- Ref: LIGO-T040119
- Yamamoto will focus on experimental demonstration at Ando Lab until the end of March, and visit Kamioka from April
- MZI implementation starts in May, probably before high power laser installation
Three-f or 3f for early phase of bKAGRA ?
- Three-f (THD)
  - Needs RF tripler for 16.88 MHz and 45 MHz, RF PD for 50.64 MHz (3*f1) and 135 MHz (3*f2). Broadband photo detector? (LIGO-D1002969)
  - operational frequency range of IQ demodulator: upto 100 MHz
- 3f
  - needs RF differential frequency generator (or harmonics generator) for 39.39 MHz (f3-f1) and 11.25 MHz (f3-f2), RF PD for those frequencies.
  - needs Mach-Zehnder modulation
ALS configuration JGW-E1707416 JGW-T1200788 ALS Wiki
- where to put a frequency offset: arm length or PLL offset [Enomoto] JGW-L1807726
- fiber selection meeting on March 23
- end-cap for fiber or not
  - end-cap on both ends -> sounds most reasonable
    - compatible to high power, upto 1.4 W
    - achieved input coupling of 80% with commercial collimator
    - measured output beam mode with commercial collimator is strange
    - can not connect short fiber on both ends for protection for handling
  - end-cap only on input side
    - can connect short fiber on output side for protection for handling
    - output beam mode is measured to be good without end-cap
    - possibility of loss and darkening at the connector adapter
  - no end-cap
    - can only put 20 mW at max, according to the specsheet
    - can connect short fiber on both side for protection for handling
    - output beam mode is measured to be good without end-cap
    - possibility of loss and darkening at the connector adapter
RF generation scheme [Michimura]
- f1 = 3/8*f2, f3 = 10/8*f2
- we need 2*f1, 2*f2, f3-f1, f3-f2 as well
- use harmonics generator (x3, x5, x6, x7, x8, x10, x16 for f2/8 = 5.62698725 MHz (FSR for IMC))
  - Wenzel specsheet JGW-D1808028
    - if Wenzel reference is input, it gives -155 dBc/Hz @ 100Hz for f1, -147 dBc/Hz @ 100 Hz for f2
    - meets the BRSE requirement (but not DRSE requirement without f1 AM) JGW-T1200913
    - updated specsheet (with updated phase noise and harmonics requirement) and quote arrived
    - will order at least two units

IMMT1 and IMMT2 transmission [Michimura, Takeda]
- IMMT2 transmission optics are too much squeezed
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
OMC and OFI [Somiya]
- look for OFI with larger aperture [Somiya]
- DC PD and DC QPD [Michimura]
  - DC PD not available. Look for product with similar specs
  - DC QPD available from RS
In-vacuum RF PD and RF QPD
- we need them within 1 year, considering OMC REFL and AS RF
In-vac beam-dumps
- required spec?
Actuator noise modeling [Michimura,Miyamoto]
- Summarized in the paper JGW-P1707051
- 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]

See this page for other agendas.