[Yutaro, Masayuki]

We found that the IMC and RefCav lock-loss happens every 1 hour with the error of a couple of minutes. Fig. 1 plot shows the IMC-TRANS (REFL) and the REFCAV-TRANS (REFL) for the 1 day-long.

The reason why we did not realize that the lock-loss events are periodic is that each event is very short. Therefore, we cannot see several events on the striptool or the Epics channel, and the guardian cannot realize those events. Fig.2  is the 1-sec plot of the test points with the full data.

We could not come up with the idea what cause these periodic events. So, if anyone has the idea, please let me know.

Fig.1 1-day trend of the TRANS and the REFL signals

Fig.2 Lock-loss event.

Buy the way,

I found that the TFP on the IMC REFL table was not fixed well. Also, the mirror mount for the TFP was not installed in the proper direction. The transmitted light is close to crip at the mount. I fix it, and I expected that is the reason for the lock-loss.