[Aso, Ushiba]

Abstract:

We implemented low-pass filter for OMC in-vac QPD to check if they can be used for OMC ASC or not.
To avoid conflict with OMC initial alignment with INITIAL_ALIGNMENT guardian, the filters are managed by OMC_LSC guardian.

Detail:

Though in-vac OMC QPD signals varies a lot, long-term trend seems stable.
Figure 1 shows the minutes trend data of OMC in-vac QPDs, and the average value seems almost constant.
They might be used for OMC ASC during the OBSERVATION, so we set low-pass filter at K1:OMC-QPDV{1,2}_{PIT,YAW} filter banks to see only slow trend of the signals.
Figure 2 and 3 show the filters we set at the filter banks (we set the same filters at the other filter banks).
Figure 4 shows the QPD signals after low-pass filter engagement and it looks fine because no large glitches.

After checking the filters seem good, I implemented the function in the OMC_LSC guardian to turn on them for OBSERVATION and turn off at DOWN state to avoid conflict with OMC initial alignment with INITIAL_ALIGNMENT guardian.
Figure 5 (DOWN state) and 6 (OMC_LSC_LOCKED_FOR_10W state) show the guardian script I modified.

We will monitor the signals during the observing run this weekends.