Eleonora, Pengbo, Yaochin, and Yuhang

We found green transmission DC dropped to ~600 counts at the beginning of today's work.

First, we checked the GR higher-order modes we have for the filter cavity.(As shown in the last figure) It was fine.

Then we went to the end room and found the GR_tra PD was tilted almost by 45deg. We think the PD cables have been accidentally pulled during the work to repair air conditioner which took place this morning in the end room. After we correct the angle of this PD, we found the signal went back to ~2700 counts.

We also checked green power at two points(shown in the attached picture 1) in today's situation (the green injected power is 12mW). The first point is just before GR_tra PD and it is 45uW(shown in the attached picture 2 and measured as shown in the attached picture 3). The second point is just after the green BS and it is 1mW(shown in the attached picture 4).