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Proceedings Paper

High Sensitivity Far Infrared Interferometry For Plasma Density Measurements
Author(s): Kenneth J. Button; Stephen M. Wolfe
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Paper Abstract

High resolution submillimeter interferometry systems for measurement of electron densities in the range 1013 cm-3 ≤ne ≤ 2 x 1015 cm-3 have been developed for use in Tokamaks. For the HCN laser interferometer, a mechanical modulation technique is used. The optically pumped CH3 OH lasers, which operate on the 118.8 μm line, employ phase modulation at ≈1 MHz which is accomplished by difference frequency mixing of two cavity tuned laser oscillators. These lasdrs feature a novel output coupling design which permits good mode quality and low beam divergence. The beat signals are detected using a newly developed Ge:Ga photoconductor and a direct measurement of the phase shift is obtained from the time lag between probe and reference signals. The sensitivity of the resulting phase measurement is independent of the instantaneous phase, and unaffected by fluctuations in the amplitude or in the frequency of the modulation.

Paper Details

Date Published: 26 August 1977
PDF: 8 pages
Proc. SPIE 0105, Far Infrared/Submillimeter Wave: Technology/Applications, (26 August 1977); doi: 10.1117/12.955442
Show Author Affiliations
Kenneth J. Button, Francis Bitter National Magnet Laboratory (United States)
Stephen M. Wolfe, Francis Bitter National Magnet Laboratory (United States)

Published in SPIE Proceedings Vol. 0105:
Far Infrared/Submillimeter Wave: Technology/Applications
Thomas S. Hartwick; Dean T. Hodges, Editor(s)

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