KAGRA Logbook

MIF (General)

takaaki.yokozawa - 8:36 Thursday 30 March 2023 (24601)

DARM OLG measurement

I measured the DARM OLG this morning.
After the 8:33:00 (JST) I didn't touch the interferometer, so it would be a silent run.

Images attached to this report

24601_1680133075_Screenshot from 2023-03-30 08-32-24.png

Comments to this report:

takahiro.yamamoto - 13:34 Tuesday 04 April 2023 (24664)

There was no change in DARM control if I didn't miss any component.
So change in OLTF should come from the change in the optical gain.

Optical gain decreased ~22% from the current parameter in the front-end calibration which was measured on 3/23.
Hc: 255.079dB -> 253.365dB.

This means the sensitivity in high frequency is ~22% worse than the figure in https://dac.icrr.u-tokyo.ac.jp/KAGRA/DAWG/Detchar/klog/klog24635.

Because this measurement was also already far past, I didn't apply the new value to the front-end calibration.

Images attached to this comment

takahiro.yamamoto - 1:10 Thursday 06 April 2023 (24692)

I estimated the DARM optical gain with OLTF on 4/5 (see Fig.1 and Fig.2) measured by Ushiba-kun.

A change from 3/23 was only ~3%.
255.079dB (3/23) => 254.808dB (today).

I'm not sure a reason why there was ~22% change between 3/23 and 3/30.
Is it alignment?

Anyway, today's OLTF seems to be healthy (UGF is on the intended frequency).

Images attached to this comment