LIGO Document T1000164-v5

Calculation and measurement of the OSEM actuator sweet spot position

Document #:
Document type:
T - Technical notes
Other Versions:
23 May 2020, 05:51
31 Mar 2016, 16:22
Magnet holders and flags for the OSEMs had been designed according to a calculation in Mathematica by Mark Barton to put the working position of the magnet at the position of maximum force and minimum cross coupling to displacement of the OSEM. This report describes the calculation and measurements made to check it.
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Notes and Changes:
-v5, with additional fix and explanation for coupling issue (units were not N/A/m or the like, but N/A/m^2), and two additional cases of interest:
• HDS (Peter’s emails of 2020-10-22ff), AOSEM wire, larger coil, double length, ř2 mm x 6 mm magnet
• HDDS (Srinath Karat emails, 2021-06-08ff), ř2 mm x 6 mm magnet

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