[Sunil, Yuzurihara]
We performed the lockloss investigation for the recent lockloss from the OBSERVATION state of the LSC_LOCK guardian, between 2025-06-02 02:33:35.062500 UTC and 2025-06-03 00:07:31.062500 UTC. The previous lockloss investigation was posted in klog34025. During this period, there were 14 lockloss. Note that this number included the lockloss from the 'WORKING_WITH_OBSERVATION_WITHOUT_LINES', so some of the lockloss might be related to the commissioning work.
EXCITATION under OBSERVATION_WITHOUT_LINES
Even though the state of the LSC_LOCK guardian was the OBSERVATION_WITHOUT_LINES, the excitation was done during 5 lockloss. Please switch the state to WORKING_WITH_OBSERVATION*. We don't want to waste times for the unnecessary check.
- 2025-06-02 04:38:37.562500 UTC
- 2025-06-02 05:05:22.062500 UTC
- 2025-06-02 05:59:09.187500 UTC
- 2025-06-02 06:47:16.937500 UTC
- 2025-06-02 08:15:36.312500 UTC
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 caused the IMC lockloss. The plots are listed in DAC wiki.
One new finding about one lockloss (2025-06-02 02:33:35.062500 UTC) is that the excess of the seismic motion continued over 2 minutes, as shown in Figure 1. This is quite longer than the typical time of the earthquake or the blasting and the shape is different. This might be different source. As a result of excess of the seismic motion, mirrors started to oscillate (Figure 2) and lockloss happened.
This is different from the blasting, because I didn't receive the announcement.
