Plasma scattering measurement in NSTX Tokamak using a submillimeter wave Gyrotron as a radiation source

Application of high intensity, well-collimated submillimeter probe beam is effective in improving the S/N ratio and the spatial resolution of plasma scattering measurement. High quality operation of the gyrotron and production of well-collimated Gaussian-like beam are required to improve the performance of the measurement. The high quality operation can be achieved by decreasing the fluctuations of the cathode voltage. Gyrotron output is converted into Gaussian-like beam by quasi-optical system consisting of a quasi-optical antenna and focusing mirrors.