I started the lockloss investigation on 2024/1/31.

• 2025-01-31 00:26:54.812500 UTC (1689s)
  • K1:VIS-PR3_TM_WIT_P_DQ and K1:VIS-PR3_TM_WIT_P_DQ show the oscillation with ~4 Hz. (Fig) I guess this is the cause.
  • GRX, K1:LSC-MICH_IN1_DQ and K1:LSC-PRCL_IN1_DQ show the oscillation with same frequency.
  • K1:OMC-TRANS_DC_{A,B}_IN1_DQ were saturated just before the lockloss. This affected the feedback signal of DARM. (Fig)
• 2025-01-31 03:39:23.562500 UTC (2197s)
  • At -2 s before the lockloss, the POP90 started to decrease. At almost same time, K1:OMC-TRANS_DC_{A,B}_IN1_DQ started to increase. Although I checked the oplev and ASC signals, I couldn't find the coincident signals.
  • At -1 s before the lockloss, the error signal of PRCL shows the oscilattion with 7Hz. This started after the reduction of POP90.
  • To clear the lockloss cause, more statistcs are necessary.
• 2025-01-31 05:48:06.187500 UTC (2787s)
  • At that time, Yokozawa-san and Komori-san were tuning the gain of CARM CMS. This seems to be the trigger of the lockloss.
  • At -1 s before the lockloss, K1:LSC-MCL_OUT_DQ started to increase. It makes the increase of K1:LAS-POW_PMC_OUT_DQ and lockloss of the ISS. (Fig)