aLIGO LHO Logbook

H1 AOS (SEI, SUS)

jason.oberling@LIGO.ORG - posted 15:12, Thursday 31 October 2013 (8345)

WBSC3 ITMx Alignment

IAS: J. Oberling

SUS: B. Weaver, T. Sadecki

Took a first look at the ITMx today. It was initially pitched too far down to get accurate numbers, so Travis jumped in the chamber and adjusted it. After that I measured the following position errors and pitch/yaw:

Longitudinal: -5.0 mm (South)
Lateral: +2.5 mm (West)
- Tolerance: ±1.0 mm
Vertical: -0.5 mm (low)
- Tolerance: ±1.0 mm
Pitch: 1002 µrad down
- Target Pitch: 971 µrad down (619 µrad optic pitch + 352 µrad FC correction)
- Error: 31 µrad down
- Tolerance: ±50 µrad
Yaw: 183 µrad CCW
- Target Yaw: 0 µrad
- Error: 183 µrad CCW
- Tolerance: ±50 µrad

On caveat here: since the ISI was floating we couldn't attach the corner cube to get an accurate longitudinal measurement. The total station can use a "Sheet Refelctor" mode to measure the distance to the optic from the HR face directly, but this introduces more error in the measurement. For the purpose of calculating the lateral and vertical errors a few mm of error in the longitudinal measurement means almost nothing at this distance (>33 m; a 5 mm shift in the longitudinal direction only imparts a change of <1 µm in the lateral/vertical error calculation), but I would not use this longitudinal measurement as a basis for the actual optic position (and adjust HEPI when it might not be necessary). When the ISI is locked down we will attach the corner cube and get an accurate measurement of the longitudinal position error of the ITMx (and make any decisions about HEPI adjustments at that point).