karmeng.kwan@LIGO.ORG - posted 11:52, Tuesday 16 December 2025 - last comment - 09:59, Friday 19 December 2025(88549)
Old OPO inspection after the swap from HAM7
[Eric, Daniel, Karmeng]
We transferred the OPO from LVEA to optics lab, uncovered the lids and everything looks good.
Touch the mirror mounts and mirrors, no failure except for M3, which swivels off the mount, only part of the glue holding the mirror on the mount.
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EPO-Tagging for cool photos of OPO.
We believe that the loose M3 mirror might explain several of the issues seen with this OPO during O4:
https://services1.ligo-la.caltech.edu/FRS/show_bug.cgi?id=30440
The mirror coming loose likely moved the cavity axis and both misaligned the crystal and miscentered the beam on the M4 PZT mirror. This might explain why the cavity alignment would change whenever the crystal was moved or when the M4 PZT was scanned.