Agenda/Minutes

CRY+VIS Interface Meeting

Date: 2022/2/18 13:00-14:00

Participants: Takahashi, Aso, Uchiyama, Sato, Hirata, Ushiba, Ikeda, Kimura, Tomaru, Miyoki, Yokozawa,　Akutsu

IX: Glitch in the F3 signals. Windshield for the MN oplev. Cooling was started.
EX: Health check of IP. The feedthrough was repaired on 2/9-10. Other flanges have no leak.
IY: Adjustment of IP and BF damper. Height measurement.
EY: Preparation for the accelerometers.

Date: 2022/2/18 14:00-14:30

Participants: Takahashi, Fabian, Ushiba, Tanaka, Miyoki, Terrence, Uchiyama, Aso, Ishizaki

Recovered the suspension from the touching in IY. The resonant frequencies of IP are different (80mHz for L and 110mHz for T).

BS alignment: Last week on Wednesday, we aligned the BS to reflect the X-arm green laser to reach the Y-End.
- We adjusted the yaw of the suspension with the F0 stepper motor. We didn't have much time to check, but Hirata-san did a cursory inspection of the payload and it didn't seem to be touching the security structure. Until now there's no indication there's a problem with the suspension, but we should take a more careful look at it soon. Maybe on a Friday.
- During alignment the oplev went out of range and we recover it on Thursday.
- From Wednesday to Thursday the suspension drifted and we had to repeat the X-arm green laser alignment this week again.
As we have talked before, Terrence detected a very large residual motion of the BS optic, so we investigated.
- On Thursday last week we removed the temporary duct-shaped windshields and covered the chamber with our traditional fabric covers. The residual motion disappear.
- Comparison of "before and after" measurements are shown in the klog, including one of the performance of the damper ring, from which I can estimate the decay time of the 50 mHz yaw mode of the chain.

In PRM, the mirror actuator H1 has a gain which is unusually higher than the others, and we don't know the reason.
There's a klog from September 2019, in which it is suggested the coil driver is not working properly and that it should be replaced.
I superficially assessed the situation by applying actuation in H1, H2 and H4 separately and comparing the motion measured in the oplev QPDs: H1 produced less than half the displacement in yaw than H2 and H4. We definitely should investigate more.
Hirata-san continued the design of the traverser limit switch holders. He also provided information of the position of the centre of mass of PRM mirror.

Replace the PRM mirror coil driver actuator, write the actuation matrix taking into account the position of the CM of the mirror, and estimate the relative imbalance in the actuation channels (e.g. using the Pringle mode). It would be good to calibrate the oplev QPDs and diagonalize the oplev before doing this.
For the BS magnetic damper, using the data I took last week, calculate the decay time and adjust the position of the ring if necessary.
Check the cable of the BS F0 fishing rod. There might be something wrong with it.
We should carry out regular health checks of the suspensions, during nighttime, for example. We should agree on the implementation next week.

(Date in Kamioka)

The week from 2/21

The week from 2/28

KAGRA/Subgroups/VIS/VISMinutes20220218 (last edited 2022-02-20 09:47:58 by RyutaroTakahashi)