PSL Design Meeting (PSL Review)

Information

Place: Hongo (Science Building 1 East (new building), 6th floor, Room 677), Kamioka, eZuce
Time: May 31, 10:00-12:30
Language: English

Agenda

The aim of this meeting is to share and review the design of PSL. The goal is to finalize the PSL layout and share our knowledge on high power handling towards 40 W operation for Phase-2. The main topics are

Overall PSL layout
Layout of intensity stabilization system (which is different from aLIGO)
RF AM generation scheme (KAGRA original)
High power compatibility (optics, cleanliness)
Safety issues for high power operation

Minutes

Participants:
- Hongo: Norikatsu Mio, Yuta Michimura, Masayuki Nakano, Rei Sakakibara, Kentaro Somiya
- Kamioka: Keiko Kokeyama, Kohei Yamamoto, Yutaro Enomoto, Osamu Miyakawa, Stefan Ballmer, Matteo Leonardi, Yoichi Aso
- eZuce: Shinji Miyoki
Presentation file: JGW-G1808331
Presentation file for MZI: JGW-G1808335

Action items

Make a laser safety plan [Who?]
Make a plan for observation mode [Who?]
Move ISS AOM before PMC [Nakano]
Determine ISS PD before or after MZI [Nakano]
Put thermometer and treat vibration of the high power beam dump (bd5) [Nakano]
Look into IMC power fluctuation and possibility of putting a faraday. [Kokeyama]
Ask LIGO people how to clean optics [Nakano]
Investigate MZI displacement noise [Yamakoh]
Look into other possibilities of RF AM generation and the possibility of three-f [Michimura]
Make a cable rack [Who?]
Design better periscopes [Who?]

Laser

It is not popular, but Labview interface is good for safety because it limits people who can access. LIGO also uses Labview for laser control. [Izumi]
We have to prepare remote control system, interlock system (and realtime and automatic watchdog system), interface to extract important channels.
- Working on the interface between Labview and EPICS [Miyakawa]
- Uchiyama and Tomaru will help for interlock [Kokeyama]
Fiber amp has an automatic shutdown system using a connector (turns off amp (not seed laser) if the connector is not grounded). [Nakano]
Who will make a laser safety plan?
How do we operate high power laser during observation? Do we turn off KOACH and air conditioning? Do we switch AC power supplies to DC?

High power handling

PSL commissioning will be done with the beam attenuated at the output of the laser. And then we move on to 40 W operation. Power to IMC is controlled at the very last stage of PSL. [Nakano]
HWP for power controls should be motorized, and should be quiet when not rotating. [Ballmer, Leonardi]
- We are using the same one as Virgo [Kokeyama]
Water cooling of the beam dump "bd5" will create vibration. Move bd5 to the edge of the table (or put it on a different table) [Ballmer, Leonardi]
- Mio Lab has unused two chiller. He can donate to KAGRA. [Mio]
- There is a camera to monitor the temperature of the whole PSL [Keiko]
  - It cannot be used for alarms. We need specific temperature sensors [Ballmer]
- Thermometer to monitor water pipes? [Miyakawa]
Reflected beam from the beam shutter should go to "bd5" [Ballmer]
Spec for AR coating is crucial for high power optics [Ballmer]
Thorlabs 0th order HWP is fake. Use real ones from CVI, ATF, etc. for high power operation [Leonardi]
Ask LIGO people (Rick, Sheryl?) how to clean optics [Nakano]

Frequency stabilization system

AOM driver for FSS is too noisy. Will replace it. [Nakano]
- Replace it with LIGO Low Noise VCO with some retuning of operating frequencies. [Ballmer]
- Virgo uses different one [Leonardi]
Refcav vacuum chamber had a leak. We have to fix. [Masayuki]
Temperature control for Refcav is independent from FSS loop. [Masayuki]
Refcav before PMC will save EOM and RF source but from noise point of view, after PMC is better.
- PMC cavity pole is not a big issue [Ballmer]

Intensity stabilization system

ISS AOM should be put before PMC. AOM is like an interferometer and output is dirty. [Ballmer]
Out-of-loop PD on a same monolithic table with in-loop PD has common mode noise. We need another out-of-loop PD far from in-loop PD. [Ballmer]
Second steering mirror ins ISS box is curved and 45 deg incident. Is it ok? [Somiya]
- Check with UToyama people.
ISS PD before or after MZI?

EOM

Florida EOM has nasty 3-pin Dsub. Uehera version also has one (p.25 of JGW-G1707003). It should be well fixed. [Izumi, Ballmer]

PMC

PMC PZT has a resonance at ~10 kHz [Nakano]
- LHO PMC had UGF of 100 Hz [Izumi]
- UGF of 100 Hz is OK for frequency noise and intensity noise point of view (see JGW-T1402349) [Michimura]
Beam jitter coupling from the whole table need to be estimated [Ballmer]
PMC PZT capacitance? [Ballmer]
- To be measured [Nakano]
Phase noise imposed by the PMC will be stabilized by the IMC loop [Enomoto]

MZI

Measured result is an in-loop measurement. Furter investigation on seismic noise, common mode rejection ratio, etc. necessary for further noise calculations. [Aso]
0.5 inch mirror (HYD-05) for MZI should be OK for high power operation [Mio]
Air flow should be troublesome [Leonardi]
Differential jitter, frequency noise etc. from two paths make me nervous [Ballmer]
- 99.9% mode-matching should be possible by mode-matching the two paths to a same cavity [Leonardi]
Possibility of EOAM? [Aso]
- Hard to realize EOAM with wedged EOM. (see JGW-D1503189)
Possibility of three-f? [Somiya]
- May be possible if we buy RF tripler and broadband PD. [Michimura]
Possibility of different RF AM generation method?
- Commercial ones? [Ballmer] Waveguides? [Ando, offline]
- Laser current? [Leonardi]
  - f3=56 MHz might be tough, but how about FSR_IMC=5.6 MHz? Attenuation by PMC will be less.

Others

Power to IMC is fluctuating a lot. Etalon effect? Maybe we need more faraday. [Kokeyama]
- Faraday right after laser source has 10% loss [Nakano]
- 20% loss for 100W and a few percent for 40W, according to CQG 19, 1793 (2002) [Somiya]

General remarks

We need a cabling rack over the table. There's screw holes at ceilings, and should be easy. Can also be used for water hose. [Ballmer]
We need a generic DC power supply for PDs etc. [Ballmer]
We need a good solution for optic mounts (AOMs, EOMs, mirrors etc.) [Ballmer]
- No forks
- Periscope should also be stiff
There are too much BNC-SMA and other dirty electronics. [Leonardi]