Today BS was less noisy, however, as reported in elog 2046, filter cavity was unlocked by the filter cavity length correction signal drift.

Actually I was thinking maybe it is related to I just turned on laser. But even after more than one hour of laser-on, the length correction signal is still drifting. Anyway, in the end, the signals including FC_GR_tra, FC_GR_correction, FC_IR_tra and PDH_detuning were monitored for one hour.

We could see that during this one hour, without any re-alignment, the detuning never jumps. The detuning changing range is roughly from 40Hz to 80Hz.

There was one period of time, green is quite stable. This is different from elog 2047, which has green misalignment. We could see during this green stable time, IR detuning drift is still happening.