Abstract.
Operating an FG-5 absolute gravimeter in a helium atmosphere should reduce the noise that is caused by vibrations of the air–vacuum interface where the interferometer laser beam enters and leaves the vacuum dropping chamber. The helium atmosphere will decrease the change in refractivity across the interface by up to 88% over the value in air, depending on the purity of the helium. A marked reduction in the post-fit residuals is observed at frequencies of about 50 Hz and little or no effect at higher frequencies. A qualitative explanation of the frequency cutoff in terms of motion of air under compression is developed. Further experiments to measure and characterize the effects of the vibrations are planned.
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Received: 25 January 2002 / Accepted: 6 September 2002
Correspondence to: D. S. Robertson
Acknowledgments. The authors are grateful to J.D. Williams of the NOAA Table Mountain Gravity Observatory for help with the recorder/flute helium sensor system, and to J. Faller of NIST for valuable discussions.
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Robertson, D., Courtier, N. & Winester, D. Absolute gravimeter helium immersion experiment. Journal of Geodesy 76, 684–689 (2003). https://doi.org/10.1007/s00190-002-0295-0
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DOI: https://doi.org/10.1007/s00190-002-0295-0