Reports until 12:15, Monday 06 October 2014
H1 SUS (AOS, DetChar, SEI)
jeffrey.kissel@LIGO.ORG - posted 12:15, Monday 06 October 2014 - last comment - 11:30, Thursday 09 October 2014(14312)
Refining ITM Optical Lever Calibration 
J. Kissel

Following the refinement of the ITM alignment slider calibration (see LHO aLOG 14265), I used the sliders as a reference to refine the calibration of the optical levers. As suspected (see LHO aLOG 12216), the correction factor to the ITMX calibration is around a factor of two. The following new calibrations have been installed as of Oct 06 2014 19:00:00 UTC (12:00:00 PDT, GPS 1096657216):
IX P = 30.87 [urad/ct]
IX Y = 25.29 [urad/ct]
IY P = 23.94 [urad/ct]
IY Y = 24.01 [urad/ct]

I still need to capture new safe.snaps for both these suspensions to make sure both the refined slider and optical lever calibrations stick.

The process:
- Step through several alignment offset values (in [urad]), record DC optical lever output (in ["urad"], the quotes indicating the to-be-refined units). I chose to get a smattering of offsets between +/- 20 [urad] surrounding the currently saved "ALIGNED" values.
- Fit slope of data points to a line (see attached). The calibration corrections are
       ["urad"/urad]    [urad/"urad"]
IX P       1.578           0.6339
IX Y       2.233           0.4478
IY P       0.9767          1.024
IY Y       1.031           0.9703
- Correct calibration.

Previous Cal        * Correction           = New Cal
48.6954 ["urad"/ct] * 0.6339 [urad/"urad"] = 30.87 [urad/ct]
56.4889 ["urad"/ct] * 0.4478 [urad/"urad"] = 25.29 [urad/ct]
23.38 ["urad"/ct] * 1.024 [urad/"urad"] = 23.94 [urad/ct]
24.74 ["urad"/ct] * 0.9703 [urad/"urad"] = 24.01 [urad/ct]
Comments related to this report
jeffrey.kissel@LIGO.ORG - 12:43, Monday 06 October 2014 (14313)AOS, DetChar, SEI
Link 

ITMX safe.snap captured as of this entry.
jeffrey.kissel@LIGO.ORG - 11:30, Thursday 09 October 2014 (14385)AOS, DetChar, SEI
Link 

For the record, Thomas had changed the optical lever calibration (see LHO aLOG 10617), based on Keita and Stefan's refinement using the same method (see LHO aLOGs 10331 and 10454). This had *increased* the gain by a factor of 2, where my calculations suggest they should be re-*decreased* back closer to the original values. Keita hints that they factor of two is weird, but, at least in words, seems to describe the same method. I have a feeling that this was done while the ETM and ITM baffle signals were crossed, and he was actually looking at PD3, which is twice as far away. They I'm checking ETMX now to see if I get values consistent with Keita's.