Direct Energy Conversion Beam Dump for a 1.6-Mev Neutral Beam for the International Thermonuclear Experimental Reactor

Abstract

A beam direct converter of the Kyoto type, which uses magnetic separation of the D[sup +] and D[sup [minus]] leaving the neutralizer, is adapted to a Lawrence Berkeley Laboratory concept of a neutral-beam injector for the International Thermonuclear Experimental Reactor, which used electrostatic separation of the D[sup +] and D[sup [minus]]. Among the advantages of a direct converter over an ordinary beam dump for the residual D[sup +] and D[sup [minus]] beam leaving the neutralizer is that the power density on the beam dump is reduced by a large factor, making heat removal easier. Further, [open quotes]soft landing[close quotes] virtually eliminates deuterium-deuterium neutron production on the dump electrodes, a particular advantage in the development stage. In addition, the total power consumed is less. This paper addresses the technological obstacle to feasibility, which is holding the large voltage (+1.6 and -1.6 MV for a 1.6-MeV neutral beam). The electrode system in the present design uses 15 grading electrodes around each 1.6 MV collector with 100 kV between them. Each grading electrode is subdivided into two. The total stored energy is 260 J (4 J per electrode) and an average of 10 kV/cm on the insulators. The calculated efficiency is 92%. 13more » refs., 10 figs.« less