jenne.driggers@LIGO.ORG - posted 16:00, Wednesday 12 June 2024 - last comment - 14:26, Monday 17 June 2024(78393)
Spot position measurements on SRC optics - summary from April-June
Sheila and Keita have double-checked the sign convention of what beam positions mean given some A2L gain on an optic. Since we have had some errors in the past few weeks, I'm summarizing their findings in this alog (and will link to this alog from the 3 measurements we have over the last few weeks).
- P2L gains that are positive mean beam is below center of optic (all optics)
- Y2L gains that are positive on SR3 mean beam is on the -X side of SR3
- Y2L gains that are positive on SR2 mean beam is on the +X side of SR2
- Y2L gains that are positive on SRM mean beam is on the -X side of SRM
Here is a summary table, in units of A2L gain:
| alog 77443, 26 Apr 2024 | alog 78119, 29 May 2024 | alog 78283, 6 June 2024 | |
| SR2 P2L gain | +5.5 | -1.0 | +8.0 |
|
SR2 Y2L gain |
-4.5 | +0.3 | +1.5 |
| SRM P2L gain | -3.4 | -5.5 | -1.0 |
| SRM Y2L gain | +3.6 | +1.85 | +6.0 |
Here is that data translated into inferred position on the SRC optics, in mm:
| 26 Apr 2024 | 29 May 2024 | 6 June 2024 | |
| SR2 Pit position [mm] | 11.1 mm below center | 2.0 mm above center | 16.1 mm below center |
| SR2 Yaw position [mm] | 9.1 mm -X of center | 0.6 mm +X of center | 3.0 mm +X of center |
| SRM Pit position [mm] | 6.8 mm above center | 11.1 mm above center | 2.0 mm above center |
| SRM Yaw position [mm] | 7.2 mm -X of center | 3.7 mm -X of center | 12.1 mm -X of center |
I have added comments to the CalcSpotPos.py script, including a printout to the terminal that reminds us of these sign conventions when using the script.
The script is still in ...../userapps/isc/common/scripts/decoup/BeamPosition/CalcSpotPos.py .
Reproduced below is a table of M1 OSEM P and Y INMON for the SRC optics I made at the request of Alena. I've just made the same thing in alog 78493 but figured that this is a better (more convenient) place for others to find these numbers.