CW FIR scattering experiment (1)

The plasma diagnostics by means of the submillimeter wave scattering has been developed and applied successfully to the study of the low frequency instabilities of the tokamak plasma. As for the heterodyne detection system on 890 GHz band, Schottky barrier diodes, manufactured by Nippon Telephone and Telegraph Company, are employed. The voltage responsivity of the detector mount is about 170 V/W and the mixer temperature is determined to be 3 x 10⁴ K at 890 GHz. Simple and long-life waveguide HCN laser is developed as a light source of which power is about 80 mW for the 2.4 m discharge length. The scattering apparatus is constructed by using these developed components and applied to the study of the scattering by the low frequency turbulence in the tokamak plasma. Main features of this observation are discussed. This scattering apparatus is also applied to the study of the optoacoustic diffraction from the TPX Bragg Cell. The use-fullness of the TPX Bragg Cell as the alignment and calibration of the FIR scattering apparatus is experimentally established. (author)