[Oli, Elenna]

Summary: Oli and I finished the alignment of all the optics on the BHSS. We were able to place beamdumps to capture the reflected beams off of the four QPDs.

Oli wrote up a summary of the work from yesterday, 89836, and they noted a mistake in the alignment of the B path. We were able to correct that alignment, so the reflected beam from QPD-T-B-R2 goes to QPD B 1 and the transmitted beam reflects off QPD-T-B-R3 to the QPD B 2. Keep in mind that we are following the naming convention that's currently in D2000405 and the BHSS build document T2100190. We found that we had placed B-R2 one hole wrong yesterday, and once we had corrected this, it was much easier to center the beams on the mirrors and get them to the correct QPDs.

Oli briefly described this issue yesterday, but I want to emphasize again: we struggled to use the D2400130 alignment template to align the mirror called "36-R1". This mirror is a high reflector that steers the beam to a splitter that splits to the on-platform OMCB REFL path, and then off-platform to the LO WFS. Because this mirror is a high reflector, it has black glass clipped to the back, and the screw to hold the clip in place protrudes and interferes with the place the optic is supposed to press against the alignment template. This means we have to slightly rethink the HAM6 table alignment plan slightly. I think, since we have aligned the subsequent beamsplitter to the OMCB REFL path, we can follow these steps:

• use the OMC iris alignment template to align the input beams to each OMC, remove when finished
  • placing this alignment template requires removing the three optics at the head of the manta ray (A-R1, B-R1 and 36-1)
• use D2400130 to align A-R1 and D2400129 to align B-R1
• Use the reflected beam from OMCB and the placement of B-R1 and all downstream optics to find the correct placement of 36-R1

These steps will vary slightly depending if we only do the phase A install, or we do phase A and B together. If we only do phase A, we will just have to guess the 36-R1 placement for now, because there will be no beam to check it.

We are ready to go for cable routing and butterdish clamping on the BHSS!