sheila.dwyer@LIGO.ORG - posted 19:04, Tuesday 17 April 2018 - last comment - 05:05, Wednesday 18 April 2018(41505)
IMC misaligned
Peter King went back into the PSL so that we could try to lock the IMC for some work in HAM6 this evening. While Peter was in the enclosure, the IMC was locked and the alignment was decent, however as Peter was leaving it looks like something misaligned in yaw which is not in the same gouy phase as the PZT, so we can't re-aling it without going back into the PSL. Since I'm not sure which irises Peter and the PMC crew were using, we are not going to try to align it tonight. If we can lock the IMC tomorrow that will help us to finish of HAM6 work.
I've left the alignment sliders as they were last night, this is the alingment that Craig had used to lock the IMC between the EOM and PMC swap. If the irises were set after the EOM swap then these might be a good reference for recovering the IMC alignment.
Attached is a coincidental shot of the table I took yesterday. The two irises are (poorly) marked in the photo. The first is before the second lens located after the EOM. The second is the smaller iris located before the mirror at the base of the IO periscope. Both irises were positioned before the pre-modecleaner was replaced. The laser and pre-modecleaner had been off for about an hour before I went into turn things back one. After re-locking the pre-modecleaner, I checked the beam position on the irises. To me the beam appeared slightly high on the first iris and okay on the second iris. The image of the pre-modecleaner reflected spot was also slightly different. However I would expect that things would return one the pre-modecleaner warmed up. This is also true with the "old" pre-modecleaner.