[Shuta Tanaka, Ide, Obayashi (Aogaku), Yuzurihara]
We performed the lockloss investigation for the lockloss which happened between 2025/06/25~07/01. The previous lockloss investigation was posted in klog34684. During this period, there were 20 lockloss from the OBSERVATION state. The plots are listed in DAC wiki.

Quick saturation of OMC DCPD

There waa no lockloss with the quick saturation.

Slowly saturation of OMC DCPD

For 3 lockloss (i=62, 67, 68), the slowly saturation of OMC DCPD can be seen. This phenomena is same as regular report one. The oscillation just before the saturation was 20~40 Hz. Two of them have the ISC_WC_L label.

There was no lockloss with 18 Hz oscillation.

Earthquake

For 4 lockloss, the EQ label was asgned.

Excess of 1~10Hz seismic motion

For 8 lockloss (1 of them has also EQ label), 1Hz label was assigned. In addition, for 3 lockloss (i=50, 57, 62), we found the excess of the 1Hz seismic motion.

Alignment upward the AS port

For 2 lockloss (i=53, 60), we can see the increase of OMMT2 TRANS, increase of AS17, the large feedback for ASC DHARD. the gradual drop of IR trans. I guess the alignment upwad the AS port (before the OMC) was changed before the lockloss.
Comments from experts are very helpful.

Lockloss by the human request

For 1 lockloss, the REQ label was asigned.