LINUS cycle calculations including plasma transport and resistive flux loss

Abstract

In the LINUS fusion reactor concept, a rotating liquid-metal liner is used for reversible mechanical compression of thermonuclear plasmas, where a vacuum-field ‘buffer’ zone is used between the plasma and wall to reduce transport losses. The concept has the particular attractiveness of operating in a self-sustaining cycle if the alpha-particle burn energy equals all losses incurred during the liner implosion and re-expansion. A minimum LINUS size can be derived by requiring this burn energy to equal the energy lost to Ohmic dissipation associated with flux diffusion into the linear material and mechanical losses associated with the liner fluid mechanics. A one-dimensional plasma transport and burn code, including incompressible liner dynamics with heat transfer and temperature-dependent flux diffusion in the liquid metal, is used to model various LINUS configurations. Corrections due to compressibility are discussed using a simplified analytical model. Numerical coefficients are derived for simple LINUS scaling laws. The particular case of plasma contact with the liquid metal is studied to determine the effect on LINUS performance. Some thermal contact with the liner before peak compression does not kill the plasma burn, and can thus be allowed in compression scenarios. The tendency of the field to remain imbedded in the hot plasma is, however, not sufficient to significantly retard diffusive flux loss into the liner and, thus, does not reduce the minimum LINUS size. Particular emphasis is placed on evaluating, from a physics standpoint, the relative merits of the lithium-plus-steel shell and the Pb-Li + inner-Li-layer configurations proposed in the literature.