Experimental studies of divertor stabilization in an axisymmetric tandem mirror.

A divertor coil set has been installed on the Tara tandem mirror [Nucl. Fusion 22, 549 (1982); Plasma Physics and Controlled Nuclear Fusion Research 1984 (IAEA, Vienna, 1985), Vol. 2, p. 285] for stabilization of m=1 flutelike modes. The effectiveness of divertor stabilization is discussed in experiments where m=1 modes are driven to instability by plug electron cyclotron heating (ECH) in an ion cyclotron heated (ICH) plasma. The instability onset is characterized by thresholds in ECH power, fueling rate, ICH power, and mapping radius of the divertor null. In general, the stability is enhanced by mapping the null radially inwards into the plasma. The interdependence of these parameters and their effect on equilibrium profiles and stability boundaries are discussed. [ABSTRACT FROM AUTHOR]