Application of high frequency biasing and its effect in STOR-M tokamak

Abstract

A pulsed oscillating power amplier has been developed to apply high frequency biasing voltage to an electrode at the edge of STOR-M tokamak plasma. The power amplier can deliver a peak-to-peak oscillating voltage up to 120V and current 30A within the frequency range 1kHz-50kHz. The electrode is located in the equatorial plane at radius ρ = 0.88. The frequency of the applied voltage has been varied between discharges. It is observed that the plasma density and soft x-ray intensity from the plasma core region usually increase within the frequency range 1kHz-5kHz but seldom increase above 5kHz. Transport simulation has been carried out for STOR-M tokamak parameters using the ASTRA simulation code to understand the physical process behind experimental observations. The model is based on the stabilizing effect of the pondermotive force due to oscillating inhomogeneous electric field produced by biasing voltage which can suppress anomalous transport. Simulation results can reproduce the experiment quite well.