Measurement of Optical Path Fluctuations due to Residual Gas in the LIGO 40 Meter Interferometer

Abstract:: Statistical fluctuations in the column density of residual gas in the beams of a laser interferometer gravitational wave detector induce noise in the measured optical path. Resulting limits on the permissible gas pressure for a given strain sensitivity strongly influence the LIGO vacuum system’s configuration and cost. Until recently these limits were based entirely on a theoretical model. The displacement noise spectral density of the LIGO 40 meter interferometer was monitored as samples of carbon dioxide, nitrogen, and xenon gases were admitted to its vacuum system. Measurements confirm the model’s predicted dependencies on frequency, molecular polarizability and mass, and pressure. Independent calibration of the interferometer verifies that the model also accurately predicts the effect’s observed magnitude, within the 10% calibration accuracy.

Files in Document:

Notes and Changes:: Migrated document information from the old DCC:
- Full document number: LIGO-P940008-00-R
- Author(s): Stan Whitcomb; Mike Zucker
- Document date: 1997-09-22
- Document received date: 1997-09-22
- Document entry date: 1994-01-01
- Publcation info: Proceedings of the Seventh Marcel Grossman Meeting on General Relativity, July 1994, Stanford University, R.T. Jantzen and G.M. Keiser, eds., World Scientific Publishing Co., Singapore, 1434-1436 (1996)
- Publication author(s): Zucker, M.E. and Whitcomb, S.E.
- Citation reference: f

LIGO Document P940008-x0