karmeng.kwan@LIGO.ORG - posted 14:16, Friday 16 January 2026 - last comment - 21:59, Monday 19 January 2026(88789)
HAM7 ZM4 alignment
[Sheila, Rahul, Karmeng]
A continuation of yesterday's progress. The additional power observed yesterday was due to the green for FC lock. We measured 0.75mW exiting the OPO, 0.74mW after SFI1 and also on the SQZT7 homodyne detector.
Today we reduced the saturation on ZM4 by clearing the offset and physically rotate the ZM4, we recovered the alignment on OMC QPDs and SQZT7 irises.
We also aligned the beam back to the HAM7 QPD A and B, at ~100nW for both of them, will need to re-centre the beam once we're back to laser hazard.
Friday, we recentered the beam onto the OPO pump fiber rejected PD.
Robert and I also went to the chamber in laser safe in the afternoon and reattached the cable clamp to the pillar on the hard to reach side of the VIP, and took phots of the camble routhing and iris locations.
Since we adjusted the alignment of B:M4 while moving the beam location in SFI2, we had to realing the path to the FC QPDs as Kar Meng mentioned above. We did this using the seed beam because that beam can be seen on a card, but it saturated the QPDs. We walked the pointing until the beam was on both QPDs as seen by saturating all the quadrants, we will want to use the CLF beam to actually center on these QPDs so that we aren't saturating.
Still to do in HAM7 in laser hazard:
Not in laser hazard: