BruCo scan here for last night lock: https://ldas-jobs.ligo.caltech.edu/~gabriele.vajente/bruco_lho_1237033818/
Some highlights:
- INP1_Y at ~ 20-30 Hz (plot 1) also visible in IMC yaw (plot 5)
- the bump at ~48 Hz is visible also in REFL_B_RF9 (plot 2)
- Below ~20 Hz OMC_RIN (but is this just another witness of DARM motion?) (plot 3)
- At 480 Hz bump, coherence with IMC WFS stuff (plot 4)
- PRCL is close between 30 and 150 Hz (plot 6)
We should check in on this again for our next lock, before we try any TCS tuning, but for at least one lock from yesterday afternoon, there is much less coherence with INP1.
DanB points out that this time is right near a TCS CO2 power change, and the IFO was cooling down a bit, so perhaps the ASC was following in a weird way. On the other hand, I've been suspicious about that particular frequency region for a while - some locks it seems high, while other locks it seems low.
There is a 2Hz cutoff in the INP1 ASC loops, but at higher frequency the suppression is only 40dB. So, probably we should take a quick measurement of these loops and add some more aggressive cutoffs just in case.
The 480 Hz is a jitter peak (ID'd by Robert here and damped here); the WFS are our best witness of jitter. I had a look at a non peak time (16/03 18:00) and a peak time (19/03 11:30) and the WFS see no difference in the 476 Hz peak, suggesting a coupling change.
Maybe I take my statement about lower coherence with INP1 back. For several locks, even in the absence of any TCS work, we have modest coherence with INP1. I have modified the cutoffs, see alog 47726.