A four-channel polarizing interferometer for ECE measurements on FTU tokamak

Fourier Transform Spectrometers (FTS) are very useful for ECE measurements since they can be absolutely calibrated by standard blackbody sources, so that independent electron temperature measurements can be obtained. The simultaneous use of several spectrometers is often required, either to analyze two dimensional configurations or to study the spatial distribution of suprathermal electrons. The path difference in conventional FTS is scanned by translating a plane mirror; an alternative scheme is based on the rotation of a screw shaped reflector; this makes possible the development of multichannel instruments with a single, very fast scanning device