Heating techniques for an EBT reactor

Abstract

The heating of an ELMO Bumpy Torus (EBT) reactor plasma by microwaves (ECH) and neutral beams is discussed. Although past and present EBT experiments use ECH for formation of the hot electron rings (annuli) and for heating of the bulk (toroidal) plasma, an EBT reactor and future proposed experiments may use neutral beams as well as ECH, or a combination of both, for heating of the toroidal plasma. When plasma is heated to ignition in a reactor, the bulk heating is turned off, but the ring heating must be sustained thoughout the steady-state operation. For microwave heating in a large, high density reactor plasma, considered are questions of microwave energy penetration and accessibility (to both the ordinary and extraordinary modes). Microwave frequencies required are 120 GHz for the toroidal plasma heating and approximately 60 to 70 GHz for the ring formation. These requirements are similar to those frequencies for the proposed EBT-II experiment. Because energetic particles having large pitch angle are well confined in EBT, perpendicular injection of neutral beams appears very attractive. The possibility of perpendicular injection, coupled with the large aspect ratio and relatively small plasma minor radius (approximately 1 m) for an EBT reactor, means that neutralmore » beams of the type being developed for the Tokamak Fusion Test Reactor (TFTR) (approximately 150 keV) will be sufficient.« less