KAGRA Logbook

MIF (General)

shinji.miyoki - 2:27 Thursday 16 April 2020 (14176)

REFL CCD image clipping

[ushiba, miyoki, yokozawa, yamamoto,yuzu]

(1) We found the REFL PD Image has clipping as an attached image. This means that there was the beam path change around IFI and REFL table.

Ushiba-kun checked the IMMT1 trans QPD position changes were negligible level (within well between +/- 1), So IMC output beam path had no remarkabke change.

Maybe we should check REFL table again, or take SAL alignment again.

This clipping might be related with up/down noise performance in the present sensitivity curves, if true.

(2) LSC-REFL_PDA1_DC_OUTPUT had about 5~6 mW value even if the IMC output power was 2.7W. This value used to be around 6 mW with 5.2 W IMC output power according to our memory and the past history checked by dataviewer. Yokozawa-kun checked the HWP rotation history, however, no ratation was found. Why LSC-REFL_PDA1_DC_OUTPUT increased ? If this value is too high, it affects on CARM servo stability with too high UGF.

Images attached to this report

Comments to this report:

shinji.miyoki - 3:45 Thursday 16 April 2020 (14177)

[ushiba, miyoki, yokozawa, yamamoto,yuzu]

Ushiba-kun took SAL aligment, and Miyoki backed the IMMT1 Yaw value that is same with that on 7th April (246 -> 265 in IMMT1 oplev Yaw).

Then almost problems have gone.

PRM alignment should be changed a lot. The beam direction to OMC was adjusted a lot. 2.5 mW level at REFL PD as used to be.

Then, much less sensitivity fluctuation, apparent 616 kpc level with 2.7W IMC output power !

We will keep this condition until the next unlock !!

Images attached to this comment

tomotada.akutsu - 5:16 Thursday 16 April 2020 (14178)

Nice! but did you also measure transfer function on the DARM signal?

takafumi.ushiba - 6:21 Thursday 16 April 2020 (14179)

Yamamoto-kun measured OLTF and UGF is almost same as previous measurement (one week ago).

shinji.miyoki - 9:13 Thursday 16 April 2020 (14181)

The change of IMMT1/2 oplev values and POP90 in the past 10 hours from 09:00 on 16th April.

IMMT1 pitch used to be -10 on 7th April. Now is around 9.

POP90 seemed to be enhanced after a kick and unlock during CAL measurement, and IFO was relock after that about 2 hours ago.

According to Ushiba-kun, Yamamoto-kun, intentional long stay for autoalignment at the stage of PRFPMI_LSC_LOCKED_RF was skipped in this relock. So the binary range with 2.7 kW IMC output power has changed from ~ 600 kpc to 520 kpc. Remarkably, some structure is recognized at present around 200 - 400 Hz.

Images attached to this comment

masayuki.nakano - 9:28 Thursday 16 April 2020 (14182)

(1) Well, the range of the IMMT QPDs is 1, so +/-1 range means nothing. Maybe typo of 0.1?

(2) Fine for CARM loop. It has +/-10 dB gain margin.

shinji.miyoki - 10:35 Thursday 16 April 2020 (14185)

Maybe this plot. So, +/- 0.1 is proper.

Images attached to this comment