[Alvin, Yuzurihara]
We performed the lockloss investigation for the recent lockloss from the OBSERVATION state of the LSC_LOCK guardian, between 2025-05-28 00:40:55.062500 UTC and 2025-05-29 00:30:56.812500 UTC. The previous lockloss investigation was posted in klog33916. During this period, there were 11 lockloss. Note that these lockloss (except for one) happened from the WORKING_WITH_OBSERVATION_WITHOUT_LINES.
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:
I got the information about the blasting from Yokozawa-san. The lockloss time is coincident with the planned time of the blasting.
Overflow of BS
1 lockloss was labeled by OVF_BS. We can see the excess on K1:ASC-MICH_Y_IN1_DQ (as shown in Figure 1). Coincidently we can see the MICH and PRCL error signals. Although I checked the several other channels, I could't find the strange behavior.
Oscillation and saturation of OMC DCPD
For the rest lockloss, the scillation of the OMC DCPD happened and saturated.
Stability of BPC from IY
Komori-san's team finished the update of the BPC by IY (klog33923) on May29 0:00 JST. Figure 2~6 show the trend data of BPC controls. The error signals are fluctuating around zero.
