[Jenne,Yuta]
Both arms are aligned starting from Y green.
We have all beams unclipped except for IPANG. I think we should ignore IPANG and go on to PRMI locking and FPMI locking using ALS.
IPANG/IPPOS and oplev steering mirrors are kept un-touched after pumping until now.
Current alignment situation:
- Yarm aligned to green (Y green transmission ~240 uW)
- TT1/TT2 aligned to Yarm (TRY ~0.86)
- BS and Xarm alined to each other (TRX ~ with MI fringe in AS)
- X green is not aligned yet
- PRMI aligned
Current output beam situation:
IPPOS - Coming out clear but off in yaw. Not on QPD.
IPANG - Coming out but too high in pitch and clipped half of the beam. Not on QPD.
TRY - On PD/camera.
POY - On PD.
TRX - On PD/camera.
POX - On PD.
REFL - Coming out clear, on camera (centered without touching steering mirrors).
AS - Coming out clear, on camera (centered without touching steering mirrors).
POP - Coming out clear, on camera (upper left on camera).
Oplev values:
Optic Pre-pump(pit/yaw) PRFPMI aligned(pit/yaw)
ITMX -0.26 / 0.60 0.25 / 0.95
ITMY -0.12 / 0.08 0.50 / 0.39
ETMX -0.03 / -0.02 -0.47 / 0.19
ETMY 0.37 / -0.62 -0.08 / 0.80
BS -0.01 / -0.18 -1 / 1 (almost off)
PRM -0.34 / 0.03 -1 / 1 (almost off)
All values +/- ~0.01. So, oplevs are not useful for alignment reference.
OSEM values:
Optic Pre-pump(pit/yaw) PRFPMI aligned(pit/yaw)
ITMX -1660 / -1680 -1650 / -1680
ITMY -1110 / 490 -1070 / 440
ETMX -330 / -5380 -380 / -5420
ETMY -1890 / 490 -1850 / 430
BS 370 / 840 360 / 800
PRM -220 / -110 -310 / -110
All values +/- ~10.
We checked that if there's ~1200 difference, we still see flash in Watec TR camera. So, OSEM values are quite good reference for optic alignment.
IPANG drift:
On Saturday, when Rana, Manasa, and I are trying to get Y arm flash, we noticed IPANG was drifting quite a lot in pitch. No calibration is done yet, but it went off the IPANG QPD within ~1 hour (attached).
When I was aligning Yarm and Xarm at the same time, TRY drifted within ~1 hour. I had to tweak TT1/TT2 mainly in yaw to keep TRY. I also had to keep Yarm alignment to Y green. I'm not sure what is drifting so much. Suspects are TT2, PR2/PR3, Y arm and Y green.
I made a simple script(/opt/rtcds/caltech/c1/scripts/Alignment/ipkeeper) for keeping input pointing by centering the beam on IPPOS/IPANG using TT1/TT2. I used this for keeping input pointing while scanning Y arm alignment to search for Y arm flash this weekend (/opt/rtcds/caltech/c1/scripts/Alignment/scanArmAlignment.py). But now we have clipped IPANG.
So, what's useful for alignment after pumping?:
Optic alignment can be close by restoring OSEM values. For input pointing, IPPOS/IPANG are not so useful. Centering the beam on REFL/AS (POP) camera is a good start. But green works better. |