Abstract

The average electron concentration of a gas-discharge plasma can be inferred from the phase change suffered by an electromagnetic wave in its passage through the medium. With available microwave generators, the maximum electron density that can be measured is approximately 3×10¹⁴ cm⁻³. On the other hand, interferometers that operate at optical wavelengths become insensitive at electron densities less than approximately 10¹⁶ cm⁻³. An infrared interferometer is described here which operates at 0.03 cm wavelength and is able to detect densities above 5×10¹³ cm⁻³ in a plasma column 1 cm thick. In the design, incoherent radiation from a mercury arc lamp is split by a diffraction grating and the plasma placed in one of the diffracted beams. The beams are then recombined and fringe shifts measured by a Golay detector.

© 1963 Optical Society of America

Multichannel far-infrared laser interferometer for electron density measurements on the tokamak fusion test reactor

D. K. Mansfield, H. K. Park, L. C. Johnson, H. M. Anderson, R. Chouinard, V. S. Foote, C. H. Ma, and B. J. Clifton
Appl. Opt. 26(20) 4469-4474 (1987)

Multichannel HCN interferometer for electron density profile measurements of tokamak plasmas

D. Véron, J. Certain, and J. P. Crenn
J. Opt. Soc. Am. 67(7) 964-967 (1977)

Resolving Power in the Near Infrared of the Fabry–Perot Interferometer with Gold and with Silver Coatings

D. A. Jackson and K. Narahari Rao
J. Opt. Soc. Am. 53(5) 558-567 (1963)

Light Output Observations on Low-Pressure Mercury-Vapor Discharges*

F. W. Crawford and H. R. Pagels
J. Opt. Soc. Am. 53(6) 734-740 (1963)

Very Stable Common-Path Interferometers and Applications

J. Dyson
J. Opt. Soc. Am. 53(6) 690-694 (1963)