ENERGY FLOWS IN A QUASI-ISOBARIC FUSION-REACTOR .1. MAGNETOHYDRODYNAMIC EQUILIBRIA

The dominant mechanisms of energy flow in a novel magnetic confinement device have been examined. The plasma is contained in the space betwe en two concentric cylinders. There is uniformity in the direction para llel to the curved surfaces of the cylinders, i.e., the toroidal direc tion, and the confining magnetic field is purely toroidal. The plasma has a rectangular cross section, bounded by a planar electrode at one end and a thermionic emitter at the other, and cylindrical walls insid e and outside. There is a modest pressure gradient, i.e., NT similar o r equal to constant. The temperature is high in the core of the plasma , where fusion occurs, but falls to low values near the walls and end- plates. It is hoped that the quasi-isobaric character will eliminate o r reduce serious instabilities and that plasma behavior will be near c lassical. The high-N, low-T periphery should reduce damage to the wall s from energetic plasma partides. The contributions of alpha-particle slowing down, electron cyclotron radiation transport, atomic processes , bremsstrahlung, conduction, convection, and heat exchange between el ectrons and ions to the energy balance in the plasma have been evaluat ed. Radiofrequency heating using waves in the lower hybrid range can b alance the differential energy equations for electrons and ions throug hout the plasma. For a device producing 125 MW effusion power, there i s a class of magnetohydrodynamic equilibria that is energetically sust ainable, with Q(dt) similar or equal to: 0.3. The inner and outer radi i and height of the reactor are 31.4, 38.7, and 7.3 m, respectively. A high magnetic field is required, in the range of 20 to 40 T. The temp erature T rises from 200 eV near the walls to 2.7 keV in the fusion co re, where N-c similar or equal to 1.5 x 10(14) cm(-3). The results obt ained here are significantly different from those obtained in an earli er study that assumed a slab geometry. This device may be acceptable a s the fusion driver of a fusion-fission hybrid reactor. Major technolo gical developments are necessary before such a device can become viabl e, but there are also some advantages relative to a tokamak reactor.