LIGO Document T1100616-v2

Buoyancy correction for suspensions

Document #:
LIGO-T1100616-v2
Document type:
T - Technical notes
Other Versions:
Abstract:
When a chamber containing a suspension is pumped down, the loss of buoyancy from the air causes a slight sag of the hanging masses, with implications for OSEM and EQ stop adjustment. -v2 of this document estimates the magnitude for quad TM, CP and ERM chains, and metal and glass builds of the BS/FM. Later versions will add estimates for other suspension types.

Betsy observes that the change in height during pumpdown is less than what is predicted in -v2 of this doc. See LHO log https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=15887

The comment to that log (15892), by Brett, estimates that those observations are something like 80% of the prediction.

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Notes and Changes:
-v2 adds calculations for BS/FM
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