camilla.compton@LIGO.ORG - posted 09:46, Wednesday 01 April 2026 - last comment - 10:04, Wednesday 01 April 2026(89729)
SQZ SUS not-repeatable alignment into FC
On Monday I had a good alignment for the FC, see 89694 and that alog's attached screenshot. Yesterday we went there and had to touch up FCs a little to get flashes. Today for the same sliders was even worse witha very PIT misalinged FC Green beam, see attached, in the same FC1 PIT slider potion, the osems were 150urad off, attached. When I brought us back to the top mass osem positions for all optics (ZM1,2,3,FC1,2 and ZM2 PSAMS) we have no green flashes in the FC, just a single pass green beam, attached.
Since the good FC flashes time on Monday, the FC has moved as attached, ~100urad in Pit and ~200urad in yaw during aligned/misaligned transitions.
I see two issues here:
- Why is the FC1 top mass osems drifting 150urd in 24 hours
- We don't seem to be able to trust the osems as going back to them gives us no FC flashes.
Rahul did in-air TF's 75830
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Rahul found that this was because the LVEA temp around HAM7 had increased ~3degF. Betsy , Geradro noticed this was as the Megacleanroom had been turned on. Richard is now turning it off.