I performed the lockloss investigation for the recent lockloss between 2025-06-11 00:06:05.187500 UTC and 2025-06-15 18:15:17.812500 UTC. The previous lockloss investigation was posted in klog34084. During this period, there were 39 lockloss from the OBSERVATION state. The plots are listed in DAC wiki.
1~10Hz seismic motion made the IMC lockloss
For 5 lockloss, we saw the excess of the seismic motion with 1~10 Hz, which made the oscillation of the IMC length control and caused the IMC lockloss.
- 2025-06-11 11:04:54.437500 UTC ( 4458s)
- 2025-06-13 18:38:51.687500 UTC ( 7587s)
- 2025-06-14 10:48:35.562500 UTC ( 1155s)
- 2025-06-14 11:58:57.562500 UTC ( 2139s)
- 2025-06-14 21:31:46.937500 UTC ( 3459s)
ETMY MN oplev glitches
For 11 lockloss (2025-06-11 00:06:05 UTC ~ 2025-06-12 00:37:38 UTC), we saw the glitches due to the ETMY MN oplev source and it made the lockloss. This issue was reported in klog34154 (6/12) and the target temparature was changed at same day (klog34168).
After the temperature adjustmenf of 6/12 0:06, we see still the several glitches in K1:VIS-ETMY_MN_OPLEV_TILT_VER_OUT_DQ and K1:VIS-ETMY_MN_OPLEV_TILT_SUM_OUT_DQ. But, the displacement size is not enough large to cause lockloss.
From my eye-scans, I thought the lockloss happened when the count of K1:VIS-ETMY_MN_COILOUTF_V3_OUTPUT is larger than 4000. So, this value might be used for the threshold. Figures 1~3 show the examples. (Figure 4 shows the exceptional event where the lockloss did't occur even though the count of K1:VIS-ETMY_MN_COILOUTF_V3_OUTPUT was larger than 4000.) Note that other plots related to this glitch are listed in DAC wiki.
Reduction of GRX power (might be due to water release from dam)
This is not related to the lockloss. we saw the reduction of the GRX power (Figure 5). Coincidently the error signal of the ASC for MCE looks like the oscillating at -1 hour (Figure 6). The fluctuation of AS17 started to increase at -30 min. Figure 7 shows the seismometer with several band pass filters. The magnitude increased at -1.5 hour of the lockloss.
Although I'm not confident, this time might be coincident with the water release from the dam, as reported in klog34228.
Gradual drop of IR trans powers
One lockloss was due to the earthquake (During writing the klog, I realized this was due to the earthquake...). There was no label by the SYS_LOCKKLOSS guardian. We saw the reduction of the both IR trans powers at -10 minutes (Figure 8). Figure 9 shows the oscillation of 0.031 Hz at BS pitch. Figure 10~11 show 0.038 Hz at ITMX pitch, ETMX pitch, and several ASC signals.
Figure 12 shows the excess of the seismometer signal.
Transient in OMC DCPD
During the lock, we saw the transient excess in OMC DCPD many times, as shown in Figure 13. This will be related to the klog34180. It might be beneficial to evaluate the frequency of the violine mode and to identify which the suspension is problematic.
