camilla.compton@LIGO.ORG - posted 16:48, Tuesday 02 June 2026 - last comment - 17:21, Tuesday 02 June 2026(90448)
HAM7 IR ZM4 Iris Set
Sheila, Begum, Camilla, Fil, Dave, Erik
Day 2 of the HAM7 work, follow on from 90426. The CDS/EE team fixed the FC1 top mass, unsure how. We found we then could not trust the sliders at all. We reverted all optics (apart from FC1) to the 90183 time. We tired putting the FC1 M3 WIT back to this time but the beam clipped on the OPOS.
Then we moved FC1 to center the IR on the SQZT7 irises. Got perfectly centered on far iris, a little high on iris at the bottom of the periscope.
Begum and Sheila then moved the ZM4 iris to mark this alignment.
Attached is current sliders.
Adding some other details:
We became concerned that we could not reproduce the alignment that we had yesterday that got IR beam onto SQZT7 IR PD. We were able to get the beam back without cliping by setting the ZM sliders back to the screenshot from yesterday (90426), and restoring FC1 M3 WIT to where they were yesterday (-85 P, -34 Y). This is not the same alignment of FC1 as O4, or as it was in our reference time 90183, but it convinced us that the ZMs hadn't moved since yesterday.
Camilla then reverted the changes she made to ZM4 + ZM5 sliders, so that they now match our in vacuum reference time for IR reaching SQZT7, 90183. She also set the FC1 sliders to reproduce the FC1 M3 wit from that reference time (P -49, Y -13) . The beam was then not centered on the SQZT7 irises, and was clipping somewhere on the VIP. Camilla then adjusted FC1 pitch to reduce the clipping and center the beam on the SQZT7 irises. This brought FC1 pitch back toward's yesterday's value (now it is at -144 urad P, -31 yaw).
We centered the iris in front of ZM4, and we think this iris will be good enough for us to recover alignment onto SQZT7 once we have recovered FC1 alignment to O4, fixed the clipping on the VIP.