I found that the sum of the ITMX oplev signals had gone down to zero yesterday.
I checked the ITMX table and found two iris on the He-Ne laser path were blocking the beam on their apertures.
I guess this is because we were working around there for installation of POP/POX and may have touched some of the oplev optics.
Then I fully opened the apertures of those two iris and the sum went back to nominal of 600 counts. |