Generation of an intense, submillimeter wave beam and its application to plasma diagnostics

Scattering measurements of density fluctuations gives important information to understanding of the mechanisms of plasma confinement and plasma heating. The spatial and wave number resolutions and the S/N ratio of measurement depend on the wavelength range, the size and the intensity of a probe beam. A submillimeter wave beam to offer small scattering volume and relatively large scattering angle is suitable for improving the spatial and wave number resolutions. Application of high frequency gyrotron is effective in improving the S/N ratio of the measurement because of their capacity to deliver high powers. It is necessary to stabilize the output of gyrotron to improve the performance of the scattering measurement. The output of gyrotron was stabilized (ΔP/P~0.2%, Δƒ~10kHz) by introducing the smoothing circuit that consisting of resistor, an induction coil and a capacitor into the high-voltage power supply