Jenne, Sheila

We tried to move the OMC ASC to the dither servos, we were in low noise with the dithers on from about 0UTC April 13th until 1:21 UTC, but we have now reverted to using the QPDs because we saw that the optical gain was decreased by using the dithers.  We will have to come back to why these are not working.

The first time that we tried to transition to the dithers while DARM was locked on RF, the OMC unlocked.  The second time, we were able to engage the servos but they had a very slow oscillation (~15 minutes) and we could see signals in the Q quadratures.  We transitioned back to the QPD servos and introduced offsets.  We phased the dither demods to reduce the signals in Q while the offsets were on, and closing the servos brought the OMC transmission back up (once we removed out offsets).  

However, watching the trend of kappa_c over the first hour of the lock we can see that the optical gain was low and getting worse, in other locks kappa_c is consistently between 1 and 1.02, in this lock it started at 1 and dropped to 0.99.  at about -200 seconds in the attachment you can see that the optical gain goes right back to 1 when we dropped out of observing to swtich back to the QPD alignment servos.  It also seems that kappa_uim and kappa_pum respond to the change in OMC alignment, which seems funny.