On May 13th (as part of my DQ shift), I noticed a line of 4kHz glitches in the glitchgram, and they have appeared every day since then. Checking the summary pages revealed they’ve been intermittently present since Apr 8, 2024 but not previously (I checked from Dec 1, 2023 onwards). Fig. 1 shows an example glitchgram from May 13th. Figs. 2-4 show Omegascans for some of these glitches. I also created a spreadsheet to characterize these glitches, and did not find any pattern or regularity to their appearance.
I checked the aLogs for possible sources and found the SQZ angle was being tuned around the time the glitches started (aLog). I then compared the timing of the glitches to the SQZ: FC ASC channels and found a correlation between the deviation in the output and the strength of the glitches. See Figs 5-7 for examples, as well as the spreadsheet. I will be meeting with the LSC fellows on Tuesday to discuss these.
Since May 24, the 4kHz glitches looked somewhat mitigated.
The correlation between the deviations of SQZ channels and the loud glitches at 4kHz has been hardly seen since May 24.
(The attachments are Omicron trigger plot and SQZ FC ASC channel on May 26)
There were SQZ commissioning works on May 24, and there are 2 alogs (alog 77980, alog 78033) related to SQZ alignment and the low frequency noises.
The 4kHz glitches are back on May 29, and the correlation between the glitches and the deviation of SQZ FC ASC channels looks apparent again.