Calculation and measurement of the OSEM actuator sweet spot position

Document #:

LIGO-T1000164-v3

Document type:

T - Technical notes

Abstract:

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.

Files in Document:

• T1000164-v3.pdf (1.2 MB)

Other Files:

• T1000164-v3.doc (43.1 MB)
• T1000164-v3.zip (248.1 kB)
• T1000164-v4draft.zip (365.1 kB)

Topics:

• Suspensions
• Subsystem Test

Authors:

• Mark Barton

Notes and Changes:

Fixed incomplete statement in conclusion, added new case for magnets to be used on tiptilt.

Note added by Norna Robertson 31st March 2016.
The coupling values given in tables 2,3 and 4 are incorrect due to a bug in Mark's Mathematica code, and should be ignored. Mark has separately provided me with the correct value of second derivative from which the coupling can be derived for the case of the iLIGO sized magnets used with AOSEMs. It is 919 N/A/m^2.
Mark is working on a v4 of this document. Meanwhile I have attached zip file from him of the redone Mathematica.