Figure 1. A new family of glitches started on Sunday around 15:30 UTC. These glitches are loud and frequent, and look to be around 33Hz.
Figure 2. These glitches are continuing during last night, so this problem is still present.
Last night's daily UPV run points V1:ENV_WI_MAG_{N/V/W} as witnesses for those glitches. Compare before and after applying these vetoes.
These glitches (I guess these are the same... and 33 Hz or so might be the energy baricenter?) seems to have a precise periodic pattern, see the attached.
Their frequency distribution seems to go from around 15 Hz up to almost 60 Hz.
First glitch is most likely a 25-min glitch. (Picture shows the whitened spectrogram of Hrec_hoft_20000Hz)
These glitches look similar to something we’ve already seen in April 2024: #64114.
The time pattern and magnetic witness point to a noise from the power supply of the heating belts, as evidenced by Bas in O3: https://logbook.virgo-gw.eu/virgo/?r=48521
sorry I missed the previous post, pointing to the same problem. The time pattern is clear.
However, consulting with Federico and Vincenzo: the cause is likely the power supply, whose fans are old and do not cool down enough, the power supply goes in protection ad switches on/off.
The suggestion is first inspect and then replace.
At around 14:57 UTC, with ITF mode set to Adjusting, we went in TCS room where the power supply is located, and also looking at its analog display, we saw that it was delivering intermittently, as indicated by the LSC_WI_HB_moni signal.
We replaced the power supply with a spare one of the same kind (Kert 420). During the intervention the operator temporarily opened the WI etalon loop. It was turned back on at 15:25 UTC.
Now the loop seems working regularly (attached fig).
Unfortunately, during the intervention the ITF unlocked, just a few seconds after the etalon loop was turned back on.
The intervention solved the issue as shown by the latest UPV run: https://scientists.virgo-gw.eu/DataAnalysis/DetCharDev/online/upv/2025/20250828/last_day_1440280822-1440367222/V1:Hrec_hoft_16384Hz/perf/vp.html