I worked on the output optics ASC characterization tonight. The measurement details will come later.
Here I want to note my activities for the other IFO users who might find my mess:
1. Initially I tried to use ITMY single bounce (PRM/SRM/ITMX/ETMX/ETMY misaligned). In reality, I had many difficulties having AS_C, AS_A_DC, AS_B_DC, OMC QPDA, and OMC QPDB in their linear regions at the same time. I jiggled SR2, OM1, OM2, OM3, and OMCS alignment biases. but no success. In the end, I gave up to use the single bounce.
2. I returned to the original values of the bias sliders. Decided to use DRMI which seemed reasonably aligned. I had to slightly tune the alignment of the BS, PRM, and SRM to acquire the lock.
3. Once lock is acquired, BS, PRM, and SRM were slightly aligned to maximize ASAIR_B_RF90 on the wall striptool.
4. In deed, all the QPDs start to show somewhat linear signals. The SRC2 ASC servo was used to align the beam on AS_C. This servo output was eventually offloaded to SR2/SRM.
5. After spending some time on the OM1-3, OMCS alignment, the beams were mostly center of the five QPDs on HAM6. Only AS_B_DC Pitch had residual of -0.3~-0.4. I decided not to go further. During this process, ASC output matrix for DC3/DC4 were touched. (and returned to the original values).
6. OMC was locked on one of the sidebands. The transmission was ~20mW. This was comparable output power to the DC readout.
6. TF and PSD measurements between SRC2, OM1, OM2, OM3, OMCS to the five QPDs and the dither errors. During this measurement, SRC2P/Y FMs were touched.
7. OMC Dither ASC signal seemed to convey no ASC information. I tried several frequencies and retuend to the original freqs (1.68k-1.75k) with dither amplitude increased from 50-200 to 1000.
Dither demoduration phases were moved from (90, 90, 90, 90) to (75, 90, 90, 100).
8. Then moved on the OMC dither LSC characterization.
9. After some cleaning up, I returned to the single bounce. After all, the ITMY single bounce beam shows up all of the QPDs around the center. This is good. So I decided to leave this alignment. We want to recover this state during the HAM6 vent next week.
10. IFO is left with DRMI and LSC not engaged
Alignment sliders before and after:
PRM (P: -1369.8 Y: 506.37) -> (P: -1361.7 Y: 492.4 )
BS (P: 149.03 Y: -297.35) -> (P: 148.98 Y: -298.04)
SR2 (P: 1935.2 Y: 776.7 ) -> (P: 1936.0 Y: 783.8 )
SRM (P: -688 Y: 907 ) -> (P: -695.2 Y: 915.0 )
OM1 (P: -533 Y: -524 ) -> (P: -643 Y: -484 )
OM2 (P: 879 Y: 736 ) -> (P: 899 Y: 656 )
OM3 (P: -423.3 Y: 625.9 ) -> (P: -423 Y: 644 )
OMC (P: -358.7 Y: 363.0 ) -> (P: 3641.3 Y: -637.0 )