Cusp containment and thermonuclear reactors

Abstract

Existing theories of the cusp containment of quiescent plasma are reviewed. Some technical and economic requirements of any fusion reactor are then summarized and used to deduce the probable dimensions of open-ended high-β reactors. It is shown that such reactors must be long, pulsed, and of very high output power. Crucial physical problems are the microstability of the high-β plasma boundary and, to a lesser extent, problems associated with energy transport by hot electrons. Assuming that these physical and technological problems are capable of solution, it is shown that mirror-symmetric versions of the hybrid-cusp discussed previously by Bickerton may have significant advantages over the simpler linear θ-pinch geometry.

Survey of thermonuclear-reactor parameters.

“…Spalding 34 considers variations of the basic cusp configuration including the conventional spindle cusp, a long 6-pinch with cusp ends ("long cusp")) and a symmetric hybrid 8-pinch cusp. He shows that in all cases it is necessary to use a pulsed high-beta plasma.…”

Plasma Confinement by Megagauss Magnetic Fields

“…However, it is intrinsically leaky, and has been bypassed by the mainstream of fusion research because, it is argued, a reactor based on this principle would be inordinately large. 16 This is indeed the case if the magnetic field is no greater than about 100 kG, but we shall show here that a cusp system becomes of reasonable size if combined with MG fields.…”

“…The maximum magnetic field that can be economically produced by a system oflarge, permanent coils is limited by the properties of conductors to -lOs gauss. The maximum density at which this field can confine a plasma of fusion temperature is thus limited to _10 16 cm-3 (for fJ = I). The long confinement times needed to achieve net thermonuclear energy production necessitate complicated confinement geometries, such as toroidal systems, for which fJ is usually much less than unity, and for which there remain problems of plasma stability and transport.…”

Thermonuclear combustion wave

“…The question of the removal of radiation and neutron energy from the hot region is examined in detail in Ref. [7] . The radiation from the cold regions at a temperature T < 1 keV and in the case of L 2 s io 3 cm is too great to be removed by the thermal conductivity of the walls, so that thermal shielding of the walls by means of screening flows of very dense alkaline plasma, produced at the ends of the reactor, becomes necessary.…”