Reports until 20:06, Monday 10 July 2023
H1 SQZ
naoki.aritomi@LIGO.ORG - posted 20:06, Monday 10 July 2023 (71217)
Reduce SQZ ASC ANG P/Y gain

Today we had SQZ ASC issue again. The first attached figure shows the related signals when SQZ ASC ran away. It seems that the ANG P/Y ran away for some reason and the SQZ-ASC_TRIGGER_INMON got down below the threshold and the SQZ ASC was turned off.

To avoid this, I reduced the gain of ANG P/Y by 20dB. I put -20dB in FM5 of ANG P/Y. The second attached figure shows the same signals with reduced ANG P/Y gain. The ANG P/Y ran away for the first 10 minutes, but the drift is much less and the ANG P/Y came back to reasonable value after that. 

I still don't understand the reason of the drift (related to beam spot control?), but at least SQZ ASC can be engaged without running away now.

Images attached to this report