thomas.vo@LIGO.ORG - posted 22:44, Thursday 07 September 2017 - last comment - 05:06, Friday 08 September 2017(38569)
PSL Ref Cav Needs Adjustment
Attached is a trend of the PSL status in the past 60 days, it seems like the FSS_TPD is slowly diminishing over time and needs to be looked at. We think this is the reason why we had trouble locking in aLOG-38568 and the reason why we had to increase the FSS gain by +6dB.
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The ALS requirement for power going into the fibre after the reference cavity is 10 mW.
Fortuitously 10 mW corresponds to 1 V for the reference cavity transmission. I do not
know how forgiving the ALS power requirement is but the reduced reference cavity transmission
might have something to do with locking in green.
Increasing the servo gain by 6 dB probably means that the unity gain of the FSS had
dropped to a point where it may have presented problems for the IMC.