[Obata, Yokozawa, Komori]

We recovered the DC readout state for a very short period (less than one minute).
After reaching the observation state, or sometimes immediately after the handover to the OMC, the DARM loop began oscillating at 30–40 Hz, which led to a lock loss.
This behavior might be caused by a mismatch in the DARM gain.

By the way, we found that the final input power to the interferometer was not at its maximum after finishing the increasing las power state.
As shown in the attached figure, the input power reached 15 W and then decreased to 13 W.