Sheila, Keita, Betsy, Elenna, Ibrahim, Oli, Tom, Camilla. Follow on from 90656
Summary: For BS alignment checks, we spent some time with the SQZ beam to check that we are happy with the SRC pointing. We could not find a beam using the BS sliders only. But we could see SQZ beam reflected off both ITMX and ITMY on the IR viewer paper at PR2. Beam splitter is being moved to overlap these SQZ beams.
With ITMY aligned, SR2, SRM mis-aligned, we expect 2.5 counts of AS_A and AS_B (1.25mW * 0.3 SRM * 0.5 BS * 0.5 BS * 0.3 SRM), we could get this on AS_A and AS_B after we reverted SR3 to O4 sliders and started with SR2 at O4 sliders but moved significantly to get light on AS_A and AS_B.
Once SRM was aligned, we could see a beam not centered on the camera. We then realized the ITMs were far off (for Oplev centering in 90443) and then started taking ITMY back towards sliders walking with SR2 (ZM6 didn't have enough range) to get a round beam more centered on AS_AIR camera. *Sheila was later unsure we should have moved ITMY like this.
After this we could see SRY fringes, there were +/-10 counts in size.
We then took ITMX to it's oplev positions last time we had DRMI lock (19 March 2025 18:02 UTC). The sliders/L2 WIT osems were still ~30urad off, think this is okay for this gross BS alignment.
Sheila put a large wobble on the BS while we had ITMX only aligned and we watched the AS_AIR camera and AS_A/AS_B. We could not find the beam off the BS at the HAM6 sensors.
Betsy then went into the chamber and could see the SQZ beam reflected off both ITMX and ITMY on the IR viewer paper clipped at the baffle in front of PR2. Sliders helped bring these beams together but was not enough. Beam splitter is being moved to overlap these SQZ beams...
Sheila, Oli and I worked on mechanically adjusting Pitch of the BBSS (BS) to bring the ITMs closer together in pitch as seen via their SQZ beams in front of PR2. In the end, I adjusted the BBSS PUM pitch adjuster ~2 full turns (after some more iterating) to get the ITM beams ~on top of each other (our better touching instead of inches apart). At some point it got harder to land the beams right on top of each other as I kept walking over the sweet spot so we moved over to using the sliders. I thought we had the slider values at ~1000 on each PIT and YAW when we left the chamber around 2:30pm PT. However now that we have moved back into the controlroom we have fallen down a few side quests and are a bit confused on what alignments are good and what aren't. So, I think we will need to revisit all of the alignment again starting next week.
Side Quest 1 - In order to refine our initial conditions alignment, Camilla and Elenna started looking closer at the ITM and SR2 slider values which were moved earlier in the day to get the SQZ correct on the AS_AIR. This was confusing since the ITM oplevs likely dropped off when we vented. Then, Anamaria pointed them ~Jun 2 90485 in order to monitor FC and baffle work, but then also they were different a month ago. These biases could be turned off to restore the "IFO pointing" but then we will be blind to the OPLEVs. So, this needs more study.
Side Quest 2 - I brought the HAM5 ISI state to Jims attention today - Jim found that HAM5 had some issues with some sensor electronics being off at the rack for the last 50 day (since April 29th) so fired that up and got the ISI back into the correct state. This moved the beam alignment Elenna and Camilla were in the middle of, so Camilla put the SR3 back to the oplev to restore the beam on the AS_AIR again.
Side Quest 3 - The BBSS sliders are badly cross-coupled in PIT and YAW - we see the beam move diagonally when moving them. LLO is newly reporting this as well. On the test stand there was no Tom, Oli and Ibrahim are looking into this - at the moment they are measuring which of the QOSEMs are firing up when requesting YAW and PIT, so the sliders are on the move. This needs more study.
So, the good news is that we have a process to view the IFO corner alignment in order to confirm/tweek the BBSS.
However because of the above and the factors which mean some SUSes have accurate OPLEVs and some don't, we will need to restart on Monday with repointing the ITMs and then revisit the SQZ beam at PR2.
SR2 - Use OPLEV pointing from THUR 5pm (when ISI came back on)
ITMs - Turn Anamaria biases off then restore to OSEMs from DRMI (?)
The pic of the beams is from before I started the mech pitch adjustment but had Yaw aligned via the slider.