Concerned about locking issues, I looked into alignment changes and compared before the power outage to after the power outage and there's a few things that stand out.
IMC MC1-3 alignment changes:
| mc1 p | 1.3 | urad |
| mc1 y | -24 | urad |
| mc2 p | 3.5 | urad |
| mc2 y | -8 | urad |
| mc3 p | 18 | urad |
| mc3 y | -22 | urad |
changes of 8-24urad
Total angular change of each chamber:
| HAM2 | 71.4 | nrad |
| HAM3 | 6.8 | nrad |
Linear change at 16.4m (IMC length)
| HAM2 | 1.2 | um |
| HAM3 | 0.1 | um |
change due to ISI is in um range
change in IM4 Trans
| im4 t p | 0.02 | normalized QPD |
| im4 t y | 0.079 | normalized QPD |
change in IM1 alignment required to account for change in IM4 Trans
| IM1 / IM4 Trans conversion | IM4 t diff | calculated IM1 change | ||||
| pitch | 287.5 | urad/ normalized QPD | 0.02 | 5.75 | urad | |
| yaw | 147.3988439 | urad/ normalized QPD | 0.079 | 11.64 | urad | |
IM1 would have to move 11.64urad in yaw to account for the change on IM4 Trans.
IM1 hasn't move 11.64urad, so changes on IM4 Trans are coming from somewhere else
change in WFSA and WFSB yaw (before values are approximate)
| before | after | diff | |
| approx | |||
| WFSA yaw | -0.83 | -0.88 | -0.05 |
| WFSB yaw | -0.83 | -0.88 | -0.05 |
diff value is not so much the problem
both WFSA and WFSB are close to or already railed in yaw, at -0.9 on a +/-1.0 scale
Seems like these things have been drifting over a long long time, see attached. Note that IMC WFS PIT and YAW signals are physically YAW and PIT on IOT2L, but PIT and YAW in chamber.
In the attached trend for 180 days, you can see that the WFS DC pointing was pretty well centered in YAW (PIT on table) and about 0.25 in PIT (YAW on table) until about 10-days after O1 concluded. There have been 5 distinct jumps since then and each step made the YAW (PIT on the table) centering worse.
It could be the loose periscope mirror on MC REFL periscope in HAM2 (alog 15650) but it's hard to say for sure.
Anyway, this means that the beam could be off on the MC length diode. If that's the case this should be fixed on the table, not by MC WFS picomotors.