I performed some quick analyses of these glitches and report a few preliminary observations below.

• Although they appear very strong in B1, their SNR in the strain channel is about 220-270, roughly half that of the 25-minute glitches. Figure 1 shows the glitchgram of the strain data, where these glitches have a central frequency around 100 Hz.
• Their waveform differs from that of the 25-minute glitches: they have a broader bandwidth and are shorter in duration, although they do show residual excitations after the peak: Figure 2.
• They seem to have a preferred separation of roughly 14′45″ ± 2″ (to be confirmed with more statistics), but they can also occur very close to one another: Figure 3.
• I ran UPV on both the strain and on SDB2_B1_PD1_D, but I did not find any evidence of correlations for these glitches (some insights for others). I will repeat the analyses over the next few days with larger statistics.

Figure 1. The problem can be already seen in CARM NULL 1F, in the trend data DARM has also glitches spaced by 15min before we reach LN3 (before there is power on B1)

Figure 2. Looking at raw data in CARM NULL 1F, the issue is actually more clearly visible in PRCL, in trend data the high frequency fluctuations of DARM are supressed, which is the reason in trend data it is more clearly visible in DARM.

Figure 3. In RDS 50Hz data the glitches can be clearly seen in PRCL, both in CARM NULL and in LN3

Figure 4. The problem was already present in the night from Nov 18 to 19, when we had the first longer CARM NULL lock after the electrical incident of Nov 17.

Figure 5. The problem was not presen in the morning of Nov 17 before the electrical incident.

A question is if the glitches remain synchronized to the ~15min spacing between different locks.

Another question if is there is any suspension glitches or environmental glitches that are coincident. By glitch, I mean a transient at ~1.3Hz, which means it will not be detected by omicron which typically looks only at higher frequencies.

There are coincident glitches in the WE F7 control signals. They started on Monday, after the timing crisis. The involved signals are the LVDT's received from the coil driver board and reconstructed as error signals of the loops. The raw signals, sent to the master board from the LVDT board, look fine, while the recontructed signals are corrupted, so we guess that the issue is at the level of the coil driver, or in the communication between LVDT and CD.