MEASUREMENT AND CONTROL OF THE GROWTH OF ROTATING MAGNETIC ISLANDS BYELECTRON-CYCLOTRON CURRENT DRIVE IN A TOKAMAK

The design of a feedback system based on the application of electron c yclotron (EC) current drive in high-density tokamak plasmas is present ed. A realistic evaluation is given of the current drive produced by h igh-power gyrotron tubes for EC-wave beams injected from the low field side in the O-mode polarization. The driven current, calculated using a relativistic analytical formalism along the ray trajectories, is in serted in a consistent theory of nonlinear tearing-mode evolution. Res ults of modeling calculations are presented, showing the possibility o f controlling by means of a digital system the evolution of the width of rotating magnetic perturbations by phase-locked modulation of the g yrotron power source.