I performed the lockloss investigation for the recent lockloss from the OBSERVATION state of the LSC_LOCK guardian, between 2025-04-22 10:23:43.062500 UTC and 2025-04-27 23:58:24.687500 UTC. The previous lockloss investigation was posted in klog33509. During this period, there were 22 lockloss.
Lockloss with the interferometer work
15 lockloss occurred in the WORKING_WITH_OBSERVATION_WITHOUT_LINES state.
1~10Hz seismic motion made the IMC lockloss
For 3 lockloss, we saw the excess of the seismic motion with 1~10 Hz, which made the oscillation of the IMC length control and made the IMC lockloss.
The time and date are summarized below:
Lockloss with unknown cause
For 4 lockloss, I'm not sure the lockloss cause.
- 2025-04-23 08:53:46.312500 UTC
- 2025-04-25 23:17:44.187500 UTC
- 2025-04-27 09:20:23.562500 UTC
- 2025-04-27 09:47:12.812500 UTC
They have common features just before the lockloss.
- K1:ASC-DHARD_P_OUT_DQ reached the large negative value (such as -400 ~ -600).
- OMMT2 TRANS increased in the last a few seconds.
In the case of 2025-04-23 08:53:46.312500 UTC, the ASC DSOFT P and Y looks the oscillation with 0.07 Hz (Fig1).
Memo
Although this is not related to the lockloss cause, I found the transient change in IMMT1 oplev P and Y. All four segment detected same transient, as shown in Figure 2 and 3. Is that the glitch due to the oplev light source?
