INFLUENCE OF CONDUCTING SIDE LIMITERS ON THE EXCITATION OF ALFVEN WAVES IN TOKAMAK PLASMAS

In recent experiments carried out on the Phaedrus tokamak, the conduct ing plates that protect both sides of a poloidal antenna set have been replaced by non-conducting boron nitride plates. With this modificati on, direct heating and current drive by Alfven waves were demonstrated . An analysis proves that elimination of poloidal conducting protector s plays a crucial role in antenna performance improvement. The effect of the conducting side limiters on the wave spectrum and antenna imped ance is calculated numerically for a cylindrical plasma column and mod el antenna current. The results demonstrate that conducting side Limit ers cause the excitation of additional modes that are deleterious for the Alfven heating and current drive scheme.