Rana and I found that the QPD for the optical lever at X end are showing small signals.
At this moment each of the segments exhibits approximately 200 counts when the oplev beam is centered.
These small numbers may be due to the coating of ETMX, but we are not sure.
Probably we have to increase the gain of the QPD depending on situations.
So a set of the tomorrow's daytime task is:
1. check the trend data of the QPD outputs to see how much signals were there in the past.
2. check the whitening filters to make sure if it's on or off.
3. If it's necessary, increase the gain of the QPD to have reasonable readouts.
I am going to ask somebody to do this task.