Plasma scattering measurement using a submillimeter wave gyrotron (gyrotron FU-II) as a power source

Electromagnetic waves of medium power (P = 110 W) in the submillimeter wavelength range (f= 354 GHz) are generated in long pulses (τ = 0.6 s) by the GYROTRON FU-II and they have been applied to plasma scattering measurements in compact helical system plasma. Use of a gyrotron as a power source improves the S/N ratio of the measurement. The results of low frequency density fluctuations correspond to those of reflectometry. A new transmission line is designed for conversion of gyrotron outputs into a high quality beam. Analysis using Huygenʹs equation supports the view that this system can produce a high quality beam. The final goal is to improve the performance of the scattering measurement by applying an optimal probe beam.