Following on from this log (alog #89046), we have already checked that the MC mirrors are restored to their previous positions from before the power cut in December. We know the seismic state now should be as close as we can manage to this time 2025-12-03 11:28:44 UTC when the mode cleaner was locked at 2W input power and before any HEPIs were locked for the vent.:
Summary of seismic state now:
HAM ISI locked. HAM 2, 3, 4, 5, 6 ISI isolated.
HAM1,2 and BSC2 HEPI locked. HAM 3,4,5,6 HEPI isolated - ie. as per nominal operation.
I trended the IM osems and the MC2 and IM4 QPDs in HAM2 while the mode cleaner was locked for mode scans yesterday (reference time is 2026-02-05 18:44:36 UTC).
It seem as though the MC2 and IM4 trans powers we have are lower now, but also the IM mirrors have changed.
As Sheila did yesterday I will try and summarise these changes in a table and compare whether this makes sense with the greater HAM1 loss we have because of the JAC (~40 %).
Just posting an updated version of Sheila's table to compare this new time (3rd December).
| 2025-12-03 | 2026-02-05 | ||
| seismic state | nominal | HAM1 ISI, HEPI locked, HAM2 HEPI locked. | MC mirrors should be at or close to nominal assuming table alignment didn't change much. |
| power into HAM1 H1:IMC-PWR_IN_OUT16 | 2W | 1W | |
| MC2 trans | 310 counts | 90 counts | consistent with 60% HAM1 throughput measured with a power meter (extra loss due to temporary mirror for JM3) |
|
IM4 trans nsum |
1.8W | 0.1W | should be 0.54 W so not consistent with JAC loss. |
| IM1 position P, Y | 3130, -679 | changed by -11, -0.44 | Off in pitch |
| IM2 P, Y | 915, -226 | -50, -3 | Off in both, mainly pitch. |
| IM3 P, Y | 44, -1634 | +4, -13 | Off in both, mainly yaw |
| IM4 P, Y | -2815, -22 | +64, -8 | Off in both, mainly pitch. |
So after this Sheila and I are going to try turning on the IMC ASC and working out if we can tune the alignment onto IM4-TRANS using the IMs.
