I performed the lockloss investigation for the recent lockloss from the OBSERVATION state of the LSC_LOCK guardian, between 2025-06-05 01:22:05.687500 UTC and 2025-06-06 01:49:44.812500 UTC. The previous lockloss investigation was posted in klog34073. During this period, there were 10 lockloss from the OBSERVATION state. The plots are listed in DAC wiki.
1~10Hz seismic motion made the IMC lockloss
For 4 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.
- 2025-06-05 13:26:37.312500 UTC (2399s)
- 2025-06-05 14:52:34.562500 UTC (2889s)
- 2025-06-05 21:01:22.062500 UTC (925s)
- 2025-06-06 01:21:00.312500 UTC (4432s)
Excess of OMC DCPD and coincidence with ETMY MN oplev transient
For 1 lockloss, we saw the excess of OMC DCPD (K1:OMC-TRANS_DC_SUM_OUT_DQ and K1:OMC-TRANS_DC_{A, B}_IN1_DQ) from -10 s, as shown in Figure 1. We are not sure the origin of this excess.
Separately, Figure 2 shows the excess of OMMT2 TRANS at -23, 19, and -5 s. These excess has a coincidence with the transient behavior of K1:VIS-ETMY_MN_OPLEV_TILT_SUM_OUT_DQ.
Memo1: Transient of ITMY and ETMY MN oplev sum
Note that this will not be related to the lockloss.
Figure 3 shows the oplev sum of ITMY and ETMY over a four hours. Sometimes we can see the transient behavior in the oplev sum of ETMY MN. It has a coincidence with the OMMT2 TRANS, as shown in Figure 4. And also, we can see the transient shift of the oplev sum of ITMY MN. As I heard from Yokozawa-san, this seems to be a mode hop.
Memo2
The duty cycle of June 5 was 71 %.
