Fourier transform spectral analysis of the cyclotron radiation from the PLT Tokamak

A Fourier transform spectrometer system, assembled from commercially available components, has been installed on the PLT device as part of a joint University of Maryland Princeton Plasma Physics Laboratory project for studying cyclotron radiation from tokamaks. The system consists of a polarizing Michelson interferometer with a rapidly reciprocating scanning mirror, a multi-element low pass transmission filter, a fast composite germanium bolometer, and a dedicated minicomputer for digitizing the interferogram and computing the spectrum. The system can acquire up to about 12 successive interferograms, at a rate of 2 per 100 msec, during a single PLT discharge. The transformation of an interferogram and the display of the resulting spectrum are accomplished in a few seconds. Analysis of the preliminary data suggests that the system can become a useful diagnostic of the electron temperature and density in PLT.