Quiet time between
PDT: 2024-03-11 19:11:02.319941 PDT
UTC: 2024-03-12 02:11:02.319941 UTC
GPS: 1394244680.319941
and
PDT: 2024-03-11 19:21:42.276196 PDT
UTC: 2024-03-12 02:21:42.276196 UTC
GPS: 1394245320.276196
Used this time to run BruCo: https://ldas-jobs.ligo-wa.caltech.edu/~gabriele.vajente/bruco_1394244680_STRAIN_CLEAN/
Notable coherences:
- DHARD_Y at frequencies below 30 Hz [so we might need to tune A2L]
- to a lower extent, CHARD_Y below 30 Hz
OMC-REFL_A_LF shows low-ish but broadband coherence with DARM above 30 Hz, and this is suggestive of the excess noise we see now w.r.t. O4a. Evan suggests that this could be 45 MHz sidebands amplitude noise, that dominates the OMC reflection, and has a small transmission through the OMC
comparing OMC_REFL with CLF to now
Atttached is a plot of the power spectrum of OMC-REFL during:
-- blue: REFL 45 O4a ( Janurary 15th 02:25 UTC )
--green: REFL 45 now (March 12th 12:30 UTC )
--brown: REFL 45 with CLF closed ( March 12th 00:24 UTC )
--red: REFL 45 with CLF open (March 12th 01:54 UTC )
Clearly, during O4a, the noise in OMC-REFL 45 was better compared to now. It seems from this is that the noise level does not change with the modulation depth (only looking at a 2 minute stretch); however, the source of the noise difference between CLF open and closed is not known. The noise level also seems to vary over the recent locks, which we cannot explain yet.
I ran a quick bruco on the OMC-REFL_A_LF channel itself, https://ldas-jobs.ligo-wa.caltech.edu/~elenna.capote/brucos/OMC_REFL/