A Fourier transform spectrometer with fast scanning capability for tokamak plasma diagnostic

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Abstract
Electron cyclotron emission spectra are routinely measured in the FTU tokamak by means of a fast scanning Fourier transform spectrometer. The key element of this instrument is a two‐beam interferometer in which the path difference is varied linearly in time by rotation of a helicoidal reflector. The shortest scan time obtained for a path difference excursion of 4 cm was 1.2 ms. The spectrometer has been absolutely calibrated and the measured temperature profiles are in good agreement with those derived from other diagnostics.