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]