Review of ICR Heating on the Spherical Tokamak Globus-M

The results of experiments on the RF heating of hydrogen-deuterium plasma at ion cyclotron frequencies in the Globus-M spherical tokamak are presented. RF power up to 200 kW at frequencies about 7.5-9 MHz fed via a single-loop antenna led to an increase in the ion temperature from 180 eV up to 400 eV in the best case. High heating efficiency is maintained at high H-concentration (up to 70%). Characteristic times of the ion temperature buildup and decay corresponded to the ion energy confinement time. If the second hydrogen harmonic is arranged in front of antenna, on-axis ion heating becomes worse. It is shown, that in Globus conditions graphite shielding of an inner surface of a vacuum chamber decreases heating due to surface absorption of RF power. Simulation of processes of RF power absorption is performed also. For modeling I-D wave code was used including all possible mechanisms of RF power absorption.