thomas.shaffer@LIGO.ORG - posted 07:45, Wednesday 13 November 2024 - last comment - 16:07, Wednesday 13 November 2024(81240)
Ops Day Shift Start
TITLE: 11/13 Day Shift: 1530-0030 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Aligning
OUTGOING OPERATOR: Oli
CURRENT ENVIRONMENT:
SEI_ENV state: USEISM
Wind: 16mph Gusts, 11mph 3min avg
Primary useism: 0.04 μm/s
Secondary useism: 0.65 μm/s
QUICK SUMMARY: Looks like H1 made it up to low noise two times in the last 3 hours, but lost lock immediately. useism is still quite high, and some wind overnight didn't help. The IMC is now struggling to stay locked after a few failed DRMI attempts, but a successful PRMI. Starting initial alignment now.
Two of the 4 locklosses over the night have FSS_OSCILATION tags and two have the IMC tag. The lockloss tool and attached trend show more glitches in the H1:PSL-FSS_FAST_MON_OUT_DQ channel before these locklosses. Maybe from the changes yesterday: TTFSS changed and "PSL FSS: Common Gain increased from 13 to 15. Fast Gain increased from 5 to 6" 81235
NLN locklosses last night:
Increasing the gains should not have caused more oscillations. I'm writing an alog covering the entirety of our work yesterday right now, but we raised the gains due to finding a bad component in the in-service TTFSS (the PA-85 high voltage op-amp in the EOM path) whose replacement
removedreduced the observed zero crossings around 500kHz noted by Sheila et al here and corrected anomolies Marc observed in the EOM path TF (he has the data for this). We also correctly tuned the EOM notch to remove the 1.685MHz peak also seen in the linked alog. Raising the common gain put the FSS UGF back in its normal range (400kHz - 500kHz), and we raised the Fast gain by 1dB to compensate for a slight loss of gain in the PZT path caused by our moving the PZT notch from ~35.7kHz to ~32.7kHz. The TF and crossover measurement showed all should be well with the FSS after these fixes, so it's still unclear why these IMC locklosses continue.Edit: Upon closer inspection of the TF, the peakiness around 500kHz is still present but apparently less, yet still close to a zero crossing. We could lower the Common gain by 1dB (to 14dB) to better clear the zero crossing if we suspect this is causing instability.
At 17:18UTC had another lockloss where the FSS_FAST_MON and FSS_PC_MON grow before the lockloss, IMC caused. Plot, zoomed plot shows there isn't explicit glitches but the FSS_FAST_MON channel just gets more noisy.
Zoom out comparing Camilla's Lockloss 1 (tagged "FSS" + "IMC") vs. Lockloss 2 (tagged "FSS").
LL1 1415545894 sees lots of FSS glitches before FSS and IMC lose lock, then IFO loses lock. LL2 1415542310 sees noise related to FSS grow slowly before lockloss.
For lockloss 2, tagged "FSS" with a slow oscillation growing before lockloss, Daniel and I then compared the FSS and OMC_DCPD fast (64k) spectra before losing lock here (where H1:PSL-FSS_FAST_MON_OUT_DQ has been calibrated with zpk = ([], [10], [1.3e6]) to get Hz/rtHz.
After PSL swap (cyan and pink traces) - laser noise looks as Daniel expected with ~100 Hz/rtHz at 100 Hz. Before PSL swap, black trace looked lower than expected, unclear. From lho81210, LLO engages this zpk filter in their filter bank to get the output of H1:PSL-FSS_FAST_MON_OUT_DQ in Hz/rtHz ; LHO has it in the filter bank but does not engage it.
We see more broadband extra noise in FSS (not in OMC DCPD) before losing lock, but no big peaks / features otherwise.