KAGRA Logbook

IOO (IMC)

tomofumi.shimoda - 23:11 Thursday 22 June 2017 (2985)

Parameters of IMC 2

[Nakano, Kokeyama, Shimoda]

1. Open loop gain under high-Finesse lock

The result is the attatched file. Measured OLG has the same shape and phase as expected, but slightly smaller by a factor of 0.73 than expected. Optical gain or something might be smaller than before.

2. Actuator efficiencies of MCe,i,o suspension

We measured actuator efficiency of MCe,MCi,MCo suspension in the same way as yesterday(only for MCe). Caluclated efficiensies are:

MCe : 17.2 MHz/V , MCi : 15.9 MHz/V , MCo : 14.9 MHz/V @DC

Efficiency of MCe is smaller than yesterday(25.5MHz/V) by a factor of 0.67. It may be because optical gain(calibration factor) was smaller(if so, the actual efficiencies are larger).

And the sign of output matrix of MC length was set to : MCe : +1 / MCi : -1 / MCo : -1

3. IMC guardian has been set

We changed IMC guardian script for current situation(2mW input). It works correctly. Now IMC is locked automatically.

Images attached to this report

Comments to this report:

yutaro.enomoto - 0:46 Friday 23 June 2017 (2987)

Really excited to hear that IMC is back now!!

>> Efficiency of MCe is smaller than yesterday(25.5MHz/V) by a factor of 0.67. It may be because optical gain(calibration factor) was smaller(if so, the actual efficiencies are larger).
It seems unlikey that the actuator efficiency of MCe suspension varies by a factor of ~0.7 day by day. This is probably due to the change of the optical gain, as you implied.
To remove the effect of the change of the optical gain, it would be nicer to inject sine signal to the suspension immediately after injecting sine signal to the laser PZT, since we already have the efficency of the PZT, which should be more stable.

tomofumi.shimoda - 22:15 Friday 23 June 2017 (2992)

Thank you for your advice. It's a good way! We will try to do it next time (unfortunately can't do it right now because we have changed the frequency actuator from laser PZT to AOM today).