Elenna, Sheila, Brina

When we engaged the OM2 heater on June 27th, we saw a reduction in input jitter coupling to DARM (70864) and a shift in OMC alignment (70886).  Today we attempted to recreate the changes we saw when turning on the TSAMS by shifting the OMC alignement, by watching IMC PZT lines, OM1 + OM3 dither lines, and the optical gain. We see that the alignment shifts are the right size to explain what happened when the TSAMs came on, but the optical gain shifts from alignment are smaller. We also see that the aligments that reduce input jitter aren't the same as those that reduce output jitter.

The first screenshot shows the alignment shift that happened when we first turned on OM2 heater.  Today we added offsets into OMC QPD A and B, we found that adding an offset of about 0.03 to OMC B made a shift somewhat simliar to what happened when OM2 was heating up (second attachment shows a step which was roughly undoing the alignment shift from June 27th).  We saw that there was a 13.8% decrease in IMC PZT P coupling to DARM when we undid that step.  On the 27th there was a 26% decrease in jitter coupling to DARM looking at the known peak around 120Hz.  So the change that we see in jitter coupling from this alignment shift has the right order of magnitude to explain the change in jitter coupling on the 27th, although confusingly we improved the jitter by undoing the move.  This move also made the coupling of the OM1 pitch dither line to DARM worse, while OM3 got slightly better. (3rd screenshot attached)

We quickly tried to move this DOF to see if we could further reduce the jitter coupling, we weren't able to get much more of an improvement. 

During all of our moves today we saw small changes in optical gain, for OMC alignment changes that were comparable in size to what happened on the 27th the optical gain changes were smaller than the 2% drop seen with TSAMs.