LIGO Document T0900416-v2

Gas Damping in Advanced LIGO Suspensions

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T - Technical notes
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The Advanced LIGO suspension design for the test masses involves the use of electrostatic drive between the test mass and a reaction mass hanging parallel to it. The baseline design for the gap between these masses is 5 mm. The question of enhanced gas damping due to the small gap has been raised in the past by an NSF review committee. This topic was addressed in a LIGO technical note T050241-00-R [1]. It was concluded in that document, with reference to papers on the topic at that time, that gas damping was not a serious noise concern. However since that document was written, new experimental evidence on enhanced gas damping due to small gaps has been produced by the Trento LISA group [2,3]. We reassess the impact of gas damping in small gaps using this new information and draw conclusions for Advanced LIGO noise performance.
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gas damping suspensions
Notes and Changes:
References updated in v2
1) typo in document number in [1] corrected
2) full reference for [3] now included

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