jeffrey.kissel@LIGO.ORG - posted 17:06, Friday 05 November 2021 - last comment - 10:31, Wednesday 19 January 2022(60564)
Calibration of HXDS Alignment Sliders: Take 2
J. Kissel Following up on the first take of calculating a calibration of HXDS alignment sliders (see LHO aLOG 60453), I now have Sheila / Camilla's measurement of the beam displacement on the ZM6 baffle caused by the ZM5 pitch slider (LHO aLOG 60480), as well as SolidWorks calculation of the distance between the HR surface of ZM6 and the entrance to the baffle from Don Griffith, which corrects the ZM5 to ZM6 Baffle lever arm and reduces the 3 inch uncertainty to 0.5 inches: Using the same method as before, but updating the lever arm numbers, and taking the weighted mean of today's work on the ZM5 to ZM6 Baffle measurement (new measured pitch calibration, and recalculated yaw calibration with updated lever arm and uncertainty), LHO:60453's ZM4 to ZM5 measurement, and the dead reckoned values from the electronics and dynamical model, I get DOF Unit Value Abs. Unc. (Rel. Unc.) PIT [urad/ct] 0.6412 0.0853 (13.3%) YAW [urad/ct] 0.8166 0.0484 (5.93%) I suggest we install these values.
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The thought process for turning the arc value into and angle value used in the above calculation (from reference LHO aLOG 60453) does not account for the infamous factor of 2 in optical-lever-style displacement measurements. The calculations should not be angle value = (arc value / lever value) but instead angle value = (arc value / (2 * lever value) ) See description of why this factor of two appears in G1200698. Rather than redo all these calculations in the comments here, I'll just make a new aLOG.