High Sensitivity Far Infrared Interferometry For Plasma Density Measurements

Kenneth J. Button; Stephen M. Wolfe

doi:10.1117/12.955442

26 August 1977 High Sensitivity Far Infrared Interferometry For Plasma Density Measurements

Kenneth J. Button, Stephen M. Wolfe

Proceedings Volume 0105, Far Infrared/Submillimeter Wave: Technology/Applications; (1977) https://doi.org/10.1117/12.955442
Event: 1977 SPIE/SPSE Technical Symposium East, 1977, Reston, United States

Abstract

High resolution submillimeter interferometry systems for measurement of electron densities in the range 10¹³ cm^-3 ≤n_e ≤ 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.

Citation Download Citation

Kenneth J. Button and Stephen M. Wolfe "High Sensitivity Far Infrared Interferometry For Plasma Density Measurements", Proc. SPIE 0105, Far Infrared/Submillimeter Wave: Technology/Applications, (26 August 1977); https://doi.org/10.1117/12.955442

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