ISC Meeting on 2019/06/25 14:00 - 15:00

Participants:

Zoom meeting: https://zoom.us/j/6676627462

Next meeting

TBD

https://www.timeanddate.com/worldclock/meetingtime.html?day=8&month=7&year=2019&p1=248&p2=4399&p3=137&iv=0

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Minutes

Agenda

ITM transmission asymmetry JGW-T1910352
ITM inhomogeneity [Hiro, Somiya]
PRC polarization klog #9325 and related klogs
- forward beam is s-pol at POP, but ITM reflected light has some p-pol
- related to ITM birefringence?
SRC gouy phase klog #9246
- Measured to be 48+/-2 deg round-trip (35 deg by design)
- Should be OK from ASC point of view JGW-T1910359
Optical table cover JGW-T1910129
- The height of 720mm (same as IMC REFL cover) might be too low. +100mm would help. Check the frames (beams) of the clean booth.
- A/I: Also design TRX and TRY cover [Michimura]

Arm finesse measurements klog #8977
- A/I: Check uncertainty in ITM transmission measurements [Michimura]
- A/I: Calculate frequency noise and intensity noise requirements with current finesse imbalance (within 1-2 weeks) [Enomoto]
- A/I: Check the frequency stability of current IMC output [Nakano]
- A/I: Check dark port output power (with ITM transmission maps) [Somiya?]
- A/I: Check with Somiya-san on temperature dependence of the thermal noise, what will be the temperature with 10W [Michimura]
- A/I: Check with Somiya-san on FINESSE simulation with ITM transmission maps [Michimura]
- Xarm finesse was ~1410 at room temperature and ~1450 at cryogenic temperatures. Michimura confirmed that this difference is not from the difference in fitting codes.
High power/Low power coil drivers switching for ITMs/ETMs JGW-T1910142
- Agreed to go with high power for ETMY and low power for ETMX.
  - Use ETMX only for DARM control
- Discussed on how to switch after the ISC meeting
  - on/off power switch do not turn off the coil driver noise completely
  - So, use watch dog circuit designed by Tanaka-san (NAOJ) instead to open the output to the coils
    - Re-programming necessary. Under investigation by Tanaka-san.
Design schematic of IOO rack
- Current version at JGW-D1706814
- Circuits to come:
  - ISS 2nd loop servo (2U) and BIO breakout (1U)
  - EOM RF Amplifier for f1,f2,f3 (1U x 3) JGW-T1809211
    - EOM RF Amplifier is similar to RF Distribution Amplifier
  - One more AA for k1ioo1 to host RF sideband monitor
    - We should make a space between AA/AIs because of heat
- A/I: Make a design schematic of IOO rack based on the inputs above [Michimura]
RF sideband tuning, Removal of f2 RF generator
- MZM experiment until May 3. ISC people can tune the frequency and replace f2 afterwards. [Kokeyama]
  - But we want to keep MZM setup as long as possible to perform further measurements if necessary
  - Instead of disassembling MZM, block MZM for a while for commissioning work
- Tune sideband frequencies with respect to PRC. Tune IMC length if we have time
  - We might open the chamber at around September for mid-baffle, beam dumps, ISS 2nd loop PDs etc.
Thick OSTM with wrong coating JGW-T1909937
- Specs
  - we want: 100mm dia, 30mm thick, p-pol, 45 deg, T=1%, AR<500ppm, 2 deg wedge
- 2 deg wedge OK?
In-vac steering mirrors
- For some steering mirrors, p-pol beam
  - STM1, STM2, POM1, POM2 around IFI (PYD-20 is used)
  - steering mirrors after OFI
- PYD-20 has a transmission
  - T < 70ppm at 0 deg for s-pol (measured)
  - T < 25ppm at 30 deg for s-pol (measured)
  - T < 5ppm at 45 deg for s-pol (measured)
  - T ~ 1000pppm at 45 deg for p-pol (specsheet)
- Do we need to order steering mirrors for p-pol?
- Also, how to dump the transmitted beams of steering mirrors?
High power compatibility of REFL table
- HWP, thin film polarizer, beam dump (water cooled power meter) were used for IMC REFL
- REFL table might not have enough space
Beam shutter around OMC
- Ref: https://dcc.ligo.org/LIGO-T1100208 (PD damaged with ~50 mJ; see Fig 6)
- Ref: https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=28683 (H1 OMC damage; pulse width ~0.1s)
- Ref: https://dcc.ligo.org/LIGO-G1000489 (shutter speed ~1msec necessary)
- Advanced Virgo: three types of shutter
  - Slow shutter in front of OMC: open only when locking OMC
  - Fast shutter in between the slow shutter and OMC: Uniblitz shutter, 10msec. Digital trigger using OMC TRANS DC PD signals.
  - Fast shutter in front of DC PDs: 10msec. Digital trigger using OMC TRANS DC PD signals
- Necessity of fast unlocking of OMC?
- For KAGRA, ~120W at max to OMC on IFO unlocks
  - current driver for OMC PZT has ~200 usec delay klog #8050
  - 1msec shutter prototype already made at Titech. In-vac one to be made by summer 2019 [Somiya]
- Delay of 200usec for the driver sounds too fast. May be too noisy?
- aLIGO uses HV driver and LV driver. One PZT is driven by HV and LV, and the other PZT is driven by HV only. LV (high speed) is used for unlocking OMC.
- We should make OMC drivers ourselves.
- OMC driver delay measurement should be done end-to-end (using beam, OMC locked).
- no space in between OSTM and OMC
- slow and compact one in between OSTM and OMC?
In-vac RF PD and RF QPD
- collected info of Advanced Virgo design (RF PD from Romain from LAPP, RF QPD from Matteo from Nikhef)

Notes

Main topics for Phase-2 [Michimura]
- Fix initial alignment scheme for full IFO
  - Enomoto?
  - For XY arm JGW-G1808462
- Finalize ALS scheme and RF AM generation scheme and finalize lock acquisition scheme
  - Enomoto?
- ISC modeling, especially ASC modeling, for intermediate IFO configurations
  - Tanioka for ASC?
- Cabling diagram
  - Almost finalized JGW-D1808394
- In-vacuum RF PD and RF QPD
  - Izumi will ask LIGO people first.
  - Laser welding would be tough (resonant circuit cannot be re-tuned)
  - Use similar design to OMC DC PD preamplifier?
- Readout DC PDs and OMC
  - In-vac amplifier board made JGW-D1809177
  - Cabling diagram around OMC JGW-G1809012
- Design output optics on optical tables Output Tables Optics wiki
Thick OSTM with wrong coating JGW-T1909937
- Specs
  - we want: 100mm dia, 30mm thick, p-pol, 45 deg, T=1%, AR<500ppm, 2 deg wedge
  - we ordered: 100mm dia, 60mm thick, s-pol, 3+/-10 deg, T<100ppm, AR<500ppm, 0.3 deg wedge
  - measured: p-pol, T=3%, AR<1000ppm (klog #8049)
  - verndor calculation: p-pol, 45 deg, T=13%, AR=3%
- We concluded that we should
  - make 30mm OSTM with correct coating -> Matteo talking with Prof. Mio
  - make a suspension for 30mm thick mirror (modify TAMA MC input suspension to put OSEMs?)
  - when to replace depends on the sensitivity and timing
Black tube for AS JGW-T1909863 [Michimura]
- Design done. Under procurement. JGW-D1910037
Polarization of Optical tables
- s-pol BSs have been used for optical tables, but actually REFL and AS/OMC REFL/OMC TRANS beams were p-pol (due to IFI and OFI)
- Beam power reducing scheme for REFL requires p-pol
  - not correct! s-pol can also be used [Enomoto]
- Why don't we keep using s-pol BSs for REFL and AS? Any comments?
  - REFL: JGW-T1809238
    - Use reflection of thin film polarizer for beam power reduction
  - AS: JGW-T1909817
    - Put HWP for all the beams
AS optical table layout JGW-T1909817 [Aritomi]
- Procurement done except for 2inch BS and spares. -> ordered 2inch BSs in April 2018
- In-vac layout basically done JGW-T1909618
  - A/I: Add OMC DC PD preamp to the layout to check the position. [Somiya]
- Also wind shield for AS table
  - TAMA wind shield is done by VIT
Harmonic Generator modification plan JGW-T1909661 [Michimura]
- It outputs x30 instead of x24, and we need a switch and standard Dsub 3pin connector for DC power supply.
- AEL will take care of modification around DC power supply, including rear panel modifications
- Use a chassis without a rear panel and handmade DC power supply cable with a switch for the time being
- Replacement of RF components will be done afterwards, with AEL and MIF.
- A/I: buy RF components for the replacement [Michimura]
- Installed: klog #8095
  - Bandpass filter for 135 MHz?
- Rear panel modification done.
Sapphire mirror damage with high power klog #7931 [Hirose]
- The average threthold for coating damage is at 92 W/mm^2
- 10 W input at PRM already gives ~13 W/mm^2 at ITM/ETMs.
- Needs to consider this risk when going to higher power.
Safety guard around output optics
- shield for OMMT1, OMMT2 (~500 mW during observation with 80W input at PRM)
- beam dump for OMC REFL (~500 mW during observation with 80W input at PRM)
- high speed beam shutter, electronics for unlocking OMC (~120W at max on IFO unlocks)
  - current driver for OMC PZT has ~200 usec delay klog #8050
  - 1msec shutter prototype already made at Titech. In-vac one to be made by summer 2019 [Somiya]
DRMI LSC with 3f, 70% SRM JGW-G1909595 [Enomoto]
- DRMI can be done with 3f
- f3 error signals during CARM offset change seem to be more affected by 3f. Strange.
AS port layout JGW-T1909618 [Somiya,Michimura]
- The power of OMC REFL will be quite high (~500 mW with 80 W input, carrier TEM00 is ~20 mW).
  - Put a pick-off mirror inside the vaccum chamber to reflect 99 % of the beam to dump, and extract 1% transmission in-air.
- The power will be even higher in IFO unlocks.
  - A/I: High speed beam shutter, Analog circuit for unlocking OMC, Protectors for OMMTs and OSTM.
  - Ref: https://dcc.ligo.org/LIGO-T1100208 (PD damaged with ~50 mJ)
  - Ref: https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=28683 (H1 OMC damage; pulse width ~0.1s)
- A/I: Check AR reflectivity of viewports [Hirose]
  - -> ~1% at 45 deg
- A/I: Check if OMC TRANS is extractable from OMC mirrors [Somiya]
- A/I: Buy a pick-off mirror [Somiya]
Mach-Zehnder modulator [Yamakoh]
- Future plans
  - Make monolithic MZM?
  - Make a wind shield?
ITMY inhomogeneity JGW-T1808715
- We should check impact on sensitivity and locking as soon as possible
  - For both O3 and full bKAGRA
- There was a discussion whether we should re-optimize OMC for BRSE or DRSE without homodyne angle optimization.
- ASC simulation by FINESSE show worse signal when ITMY inhomogeniety is added (a few % degradation in shot noise?)
- higher order contents, especially odd-order modes are worse
- But still need to check the Finesse code (alignment loop not closed yet)
- FINESSE calculation on ASC was not reliable since Gouy phase tuning was not done
- Working on Gouy phase tuning
Other long standing tasks
- Real Low Noise VCO, also for FSS
- Fiber noise cancellation for ALS
- DC QPD holder
- IMMT1 and IMMT2 transmission
- Slow channels for monitoring things (PLC based? Beckhoff? Acromag?)

See Minutes20170410, Minutes20190225, and Minutes20190528 for other agendas.