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Mon Mar 30 12:46:36 2009
IOO QPDs were missing the beam
When I re-locked the MC, I wanted to check the trend of the IOO QPDs to see if the input beam pointing has changed.
Then I found that the QPDs were not receiving light.
The attached trend plots show that the QPDs missed the beam on March 23rd.
The IOO-QPD_ANG was installed on Mar 11th by Kiwamu and Kakeru. Since then, they were serving as a reference of the PSL beam pointing.
But there is no record of the past week. This is very bad because then I cannot tell if I should relieve the MC WFS to make the mirrors follow the input beam or not.
I found that someone has moved the beam splitter which picks up the beam going to those QPDs. But there is no elog entry on this around March 23rd.
I re-centered the beam on the QPDs.
Since the X-arm locked to TEM00 with the MC WFS on (i.e. the MC beam axis is following the input beam axis), I guessed that the input beam has not drifted that much. So I relieved the WFS and centered the WFS QPDs.