Reports until 18:29, Sunday 13 July 2025
H1 AOS
robert.schofield@LIGO.ORG - posted 18:29, Sunday 13 July 2025 (85728)
New suggested settings for ITMY compensation plate offsets, pitch: -317, yaw: -122

The pumps were still running last month when I  suggested preliminary CP-Y settings (85084). I wanted to get back to it with a little higher sensitivity after the pumps were shut off. As a result of this second look, I suggest new settings of Pitch: -317 and Yaw: -122; They represent only a slight reduction in scattering noise coupling, but the new settings don't  consume as much actuator range.

The technique I used to pick a minimum was the same as used here: https://alog.ligo-wa.caltech.edu/aLOG/uploads/76969_20240404184914_Fig3-Sensitivity-To-IY-CP-Yaw-Also-Bright-Spot.pdf

The structure in the coupling variation was like it was before the break (see link), at a scale of about 20 microradians in CP angle. The maximum coupling in the CP sweeps after the vent was about half of what it was in the sweeps before the vent, so maybe there was some improvement.

I made videos of the beam spot on the HAM3 ballast baffle and its support before and after the compensation plate adjustment. The compilation video uses the same slider program (see details in video description) before and after the compensation plate move:

https://youtu.be/nbZ7da6LE9s