Jennie W, Jason O, Keita K, Betsy W, Camilla C
Summary: EOM alignment and position captured, moved to opics lab for crystal replacment, JAC-REFL path alignment in progress.
This morning Jason, Keita and I checked the centering of the HAM1 irises after the JM3 alignment Olli and I did on Tuesday. We didn't move the irises right after JM3 as this seemed centred. We did reposition the iris right before the HAM2 septum plate in x and y.
This, along with the alignment of the IMC Olli, Jenne and I did on Tuesday, captures where the beam was with the current EOM installed.
Keita marked the EOM base position with a dog clamp and removed it to the optics lab for crystal replacement. The shims for the EOM and the screws that hold it to the table are in a foil packet on the +Y - X HEPI pier.
Betsy, Camilla and I rechecked the REFL path and spent some time moving JACR-M2 to centre it on the incoming and outgoing beams. Then we pitched down this mirror so the outgoing beam hit the upper periscope mirror. After this Betsy had some concerns that we were too close to where the JM3 tip-tilt will sit (we are currently using a siskiyou mount for this mirror). So we yawed the JACR-M2 mirror so the beam hits the viewport slighly more to the right (as viewed from -Y side). Looking at the placement on the viewport simulator, the beam is low and right on the viewport, whereas it comes to the table, high and right in the bellows hole. This table it almost at the top of its adjustment range, so Jason and I plan to go in this afternoon and see it we can move up the table feet so the beam can move up in the viewport a bit. Betsy and I measured the tilt of the beaM from JACR_M2 off the table. The heigh is 103 mm at the table hole 8 inches from the -X edge and 8 inches from the +Y edge. It tilts up to 113mm at the last hole in this row on the -Y side.
Betsy and I also checked the pitch of the beam entering and leaving JAC after the EOM was removed. The input beam to the JAC was 102 mm above the table, the output beam before the L1 lens was the same height, and the beam height just before JAC_M3 was also 102mm. There is not a large distance between the JAC and JAC_M3 steering mirror so it is hard to get a good measurement of any small pitch in the beam. Pictures for this alog are coming.
EOM crystal was swapped, EOM was tuned in the lab and put back in place in HAM1. Tuning is good. First look at the beam looks good, no ghosts.
We extracted the EOM from HAM1 after the position of the EOM base was marked with three dog clamps.
In the lab, the EOM pivot plate was separated from the EOM base (which was a major pain again), then the EOM top structure was separated from the pivot plate.
Before unmounting the old crystal, three set scews in the face plate were screwed in to contact the electrode board, and then very slightly backed off. After this, we lifted the board/side assy from the front plate to expose the crystal on top of the face plate, swapped the crystal (in our setup, the distance between the crystal edge and the front plate edge close to the output side was set to ~7.5mm due to 0.5mm shim washer we use between the front plate and the input side plate), and put the board/side assy on. This was much easier than before due to the aforementioned set screws. Elenna will post some pictures.
In the afternoon the EOM was tuned in the lab and put back into HAM1. We didn't bother to tap things around this time.
EOM was transferred to HAM1. Tuning measurement was repeated in chamber, no big change from the lab measurement and they're good (see pictures).
With EOM in place, we locked JAC and confirmed that the wedge orientation of the crystal was correct (because the beam was mostly deflected in YAW toward +Y direction). We also saw that the beam deflection was different from the old EOM in PIT as well as YAW (more difference in PIT according to Jason).
No fine alignment of the EOM was done for today, but we quickly raised the power to 1W and neither Jason nor I were able to find any clear ghost beams, unlike with the old crystal.
Below is a table of RTP crystals at LHO (see alog 89125, alog 89115).