Shiela, Naoki, Rahul, Kar Meng, Terry
Same as yesterday (77188), we are again today having trouble locking the FC. Wind is again constant at 0-20mph. Can get green flashes but no locking, even with FC feedback turned off, VCO locking also fails.
Rahul changed the M1 coil driver state on FC1 and FC2 from state 1 (usually only used in TFs) to state 2: IFO nominal for other triples. State 2 contains a low pass filter.
Rahul took FC2 P and L transfer functions, look healthy and same as 66414.
Rahul took FC2 OSEMINF spectrums and checked ther health, as previously had issues with FC1 BOSEMS (72563). Can see the 0.3 to 0.4Hz peak, Rahul's not worried about it but we could check old data for this peak.
Jim found that the HAM8 ISI has a resonance at the same place as FC2, peak at 0.375Hz see attached. He edited a gain and the motion seemed to improve enough to lock the FC.
During this time Ibrahim, Oli and I had followed ObservationWithOrWithoutSqueezing wiki and edited all the SQZ guardian code nominal states and accepted no squeezing sdfs. We then reverted these changes once the FC locked.
From HAM8 summary pages, I don't see this 0.36 Hz peak between Dec15 - Jan15. Peak is basically exactly where FC2_L is oscillating in yesterday's screenshot. Since Jan 15 2024, the peak looks intermittently there or gone, pretty variable. Maybe exciting this peak is related to wind? Or maybe this is all totally unrelated to wind.. I don't think this was an issue in O4a, maybe something changed after Jan 15.
Seems like another broken GS13 on HAM8, this time a horizontal sensor. I took some driven measurements looking at the l2l cps to gs13 transfer functions and the H1 cps to gs13 tfs is lower than the other 2 sensors by about 2x, see first attached image. This affects the stability of the blend cross-over, which changes the gain peaking in the blends. I've compensated for now with a digital gain, but this may not work for long.
I tried compensating with a digital gain in the calibration INF filters for the ISI, this seems to have improved things, shown in the second image. Top subplot is the M3 pit witness for FC2, second line is the gain I adjusted, third line are LOG BLRMS for the X, RZ and RX GS13s on HAM8. X and RX don't improve much, but the RZ motion improves a bit after changing the gain. Fourth line is the RZ cps residual, which is much quieter after increasing the gain to compensate for the suspected low response of the H1 GS13.
To add to Vicki's comment, the peaks behavior seems complicated, it started at .6hz in January, then some time around March it moved down to its current frequency ~.37hz. Lots of days missing from the summary pages in that time, so it's hard to track. The transience of the peak is also consistent with broken seismometers we've seen in the past. The gain tweak I put in may not be a stable fix.
SDFs that were accepted for observing w/ sqz
FYI - FRS ticket 31005 is tracking the 1/2 gain GS-13