I performed the lockloss investigation for the lockloss which happened between 2025/10/04 00:00~23:59 UTC. The previous lockloss investigation was posted in klog34736. During this period, there were 20 lockloss from the INCREASING_LAS_POWER state. The plots are listed in DAC wiki.
Commissioning activity
The first 3 lockloss happened during the commissioning activity (klog). I will ignore them.
Lockloss during increasing the laser power
For 1 lockloss, the lockloss happened during increasing the laser power.
Figure 1 shows the channels related to the PMC control. We can see the clear glitches on PSL-PMC_MIXER_MON_OUT_DQ. The timing of the glitches has the coincidence with the K1:PSL-PMC_HEATER_INMON and the step function of laser power. I'm not sure these are related to the lockloss.
Lockloss just after increasing the laser power
For 7 lockloss, the lockloss happened just after increasing the laser power. The lock duration at INCREASING_LAS_POWER were 290~305s. (Mainly 305s)
- This kind of lockloss started to occur after 2025-10-04 18:21:56.437500 JST.
- Figure 2 and 3 show the PMC channels and MCL channels. After finishing increasing the laser power, the glitches on PSL-PMC_MIXER_MON_OUT_DQ stopped somehow. Just after that, we can see the three glitches on K1:LSC-MCL_IN1_DQ and K1:LSC-MCL_OUT_DQ. We saw this phenomena sometimes.
- The PRCL and MICH error signals show the transient and the fluctuation of the signals increased around -15 s. Figure 4 shows the example of different lockloss.
Lockloss after some time from reaching the increased laser power
For 5 lockloss, the lockloss happened after some time from reaching the the increased laser power. The lock duration at INCREASING_LAS_POWER is more than 300 s. After finishing increasing the laser power, the glitches on PSL-PMC_MIXER_MON_OUT_DQ didn't occur somehow.
For some of them, I found that PRCL and MICH show the transient behavior at -10s. Figure 4 shows the example.
Earthquake
For 4 lockloss, we found the excess of the seismic motion including 1 Hz and typical earthquake.
