Sheila, Keita, Ryan Short, Camilla and TJ
Part way through initial alignment, we stopped and moved SR3 towards the positive yaw spot from 79103, and used the SR2 osem values from that time. A small manul adjustment of AS_C was needed, otherwise initial alingment was uneventful.
With DRMI locked, we ran the fast shutter test that Keita and Ryan S have both looked at.
We also looked at the ratios of AS PDs to compare to 78667, they are most similar to the good times in that alog. After these checks we have decided to try locking.
Fast shutter behavior is attached. It's working fine, but the throughput to HAM6 is ~14% down compared with before.
Before the shutter was closed, ASC-AS_A_DC_NSUM was ~3.7k counts, and ~0.75 counts after (fractional number because of decimation to 2k). That's about 200ppm.
However, it used to be ~4.3k and 1cts on one of the "happy" plots alog 79131, 3.7k/4.3k~0.86, so the throughput to HAM6 seems to be ~14% lower than before.
IFO lost lock even before going DC and we had another FS test forced by the guardian, and it didn't fail, but the throughput is even worse.
A_DC_SUM=3.4k when the shutter was open, Closed/Open ratio is about 1000ppm, and a tiny part of the beam is being missed by the shutter (attached). Note that I'm NOT eyeballing the "open" Y cursor in log scale, I set it while in linear Y scale but changed it to log to show that the power after the shutter was closed seems to be measurably larger than it should be.
Maybe this is going on because of tiny alignment differences from lock to lock, but anyway this doesn't look to be the place we want.