Jim and I have been adjusting the interferometer alignment for the last few hours.
IMC alignment
We noticed as has been noted by a few people that the IMC alignment is different from before the EQ according to the witness sensors and spots on QPDs (IMC WFS DC, IM4, and ISS QPD). We tried restoring the optics and input PZT using witness sensors, as I am sure people have tried in the last week, and saw that this made it impossible to lock the mode cleaner. Next we went back to the alignment from overnight last night. I moved the uncontrolled DOF (DOF4) to bring the IMC WFS DC spots to where they were before the EQ (this was the idea behind Suresh's effort to control DOF4 several years ago). Jim restored IM1,2,3 to their alignments pre EQ using the osems (the biggest move was IM1 pit). This resulted in restoring the spot positions on IM4 trans and the ISS QPD to their pre EQ positions. (see attached plots of QPDs and range so you can identify times of the EQ and other alignment changes made trying to recover from EQ).
One thing we noticed which Corey has also logged is that there is some kind of mistake in the IMC WFS offlaod script which misaligns the PZT. We could replace this with our generic WFS offload guardian state anyway.
PR3+SR3 osem jumps
This is also something that other people have noted, but there is a large jump in the osem values compared to the oplevs for PR3 +SR3 after the EQ. We spent some time worry about both of these optics because of a problem which turned out to be the fast shutter. PR3 moved after teh EQ, but the osem and oplev do not agree about the size of the move, and it seems like it is some kind of permanent shift in the value of the osem. Cheryl has a nice plot that shows this. It seems like people already knew this and had realinged PR3 correctly using the oplev and reset the SR3 cage servo soon after the EQ.
Fast shutter problem
Jim and I did an initial alignment after the IMC +IM move, but ran into trouble at SRC aling. Cheryl and I spent several hours with this problem, which at first seemed very mysterious. We could not move the beam in single bounce to center it on AS_C, if we tried to do this using either SR2 or SR3 the image on the AS camera would turn into a huge interference/clipping blob, and the power on the AS_C QPD would drop nearly to zero. We tried moving many things with no improvement, but in the end clsing the AS shutter fixed the problem. Our best guess is that the shutter was somehow stuck in a half open state from about 22 UTC July 16th (or earlier) to about 4:30 UTC July 17th. This could have happened as early as this morning's unexplained lock loss. This happened a few more times while we were trying to test the shutter in DRMI. It looks (from the strip tool) like the shutter never actually closes but gets stuck half shut while it is opening.
We are not going to lock for the rest of the night because we don't think the shutter is correctly protecting the OMC. We are trying to contact Jeff B to cancel the OWL shift.
Final note: Ireverted the POP A offsets to what they were before the EQ, in hopes that the IFO alingment is more similar to that now. This worked in DRMI.
