Recently I looked at the highest SNR (>100) blip glitches from the low-latency monitors and noticed that most of them looked very similar in the autoscaled spectrogram (they have a lot of excess noise in the whitened spectrogram so they do not look like blip glitches there, but they are short like blip glitches).
When I generated the full omega scans, they all had in common some excess noise in the SUS-ETMY_L2_NOISEMON channels (the times I looked at -Feb 10 to Feb 14- are in https://ldas-jobs.ligo-wa.caltech.edu/~miriam.cabero/blips/O2_loud/ ). This is not true for all blip glitches, which makes me think that this might be a new sub-set whose origin could be related with the coil driver. And they are not only very loud blips, I also found other quieter ones that show something in the noisemon channels:
https://ldas-jobs.ligo-wa.caltech.edu/~tdent/wdq/H1_1165129095.9
I have looked at past aLogs and it seems like there was found a possible correlation between periods of extreme glitchiness and the ETMY L2 driver. The glitches I looked into are from last week, not from a particularly noisy period like the few days in mid December or beginning of January.
Andy was saying ( aLog 32730 ) that noisemons will show glitches whenever DARM does, and indeed there are some blips where the noisemon sees the same as DARM (e.g. https://ldas-jobs.ligo.caltech.edu/~thomas.massinger/wdq/ER10_loudest/1163443424.81/ ), but it looks somehow different for the times I mention above (and not all the blips show something in the noisemons).
So I am writing here to ask if this information is relevant for blip-glitch studies, or if the information found in the periods of extreme glitchiness is helpful for this. There seemed to be the conclusion that humidity might be the problem, as had been observed in O1 ( aLog 32885 ). That could indeed be the case for a particular time of high glitchiness, but what about the rest of the time? If the humidity is normal and we still have these kind of glitches, what could we do?
On the PSL SYSSTAT medm, we had the Oscillator/Head 1-4 flow error in a Fault/red state. Jason said this meant that we had a "glitch in laser head flow sensors". Jason brought back the PSL remotely. I topped off the PSL Chiller (the cap did NOT pop off) with 375mL of water.
13:58 Back to LOCK ACQUISITION
FRS #7460 Filed For ~1hr of CORRECTIVE_MAINTENANCE DOWN time.
Cause appears to be a trip of the Laser Head 1-4 Flow interlock, specifically Head 2. The first attachment shows the 3 laser head flow rates (the 4th is currently being forced to a value in the Beckhoff software, so cannot contribute to the trip). It is clear that head 2 became erratic and began to drop in flow, eventually passing below the trip point and tripping the laser. The 2nd attachment shows a zoomed in view of only the Head 2 flow. Possible debris passing through the flow sensor?