(This is the report of yesterday20200217) Aritomi, Eleonora and Yuhang

We found BS moved quite a lot, this was figured out later that it is because of the saturating of BS coil drivers. Then we tried to remove the DC offset of BS, which didn't work very well since we found BS moved more than before. In the end, we open the oplev local control for BS and did the experiment.

We locked filter cavity with GR and closed the pitch dithering. The BAB is sent to filter cavity and we demodulated the filter cavity reflection to have PDH signal. We detuned IR by 60Hz and leave it for one hour. During this time, the filter cavity was unlocked several times. We relocked three times, once we just relock and twice we re-aligned filter cavity.

The filter cavity GR/IR transmission and GR filter cavity length correction and IR detuning was monitored.

The result is attached. We can see different alignment causes different detuning value.

There was a zoom-in part, which we can see the correction singal doesn't change but alignment and detuning keep changing.