Charge‐state equilibrium and nonequilibrium modeling of the carbon‐pellet plasma interaction

Abstract

Self‐consistent equilibrium and nonequilibrium charge‐state models are formulated for the spherical expansion of low‐Z pellet vapor as an inviscid perfect gas of constant ratio of specific heats being heated volumetrically by the incident electrons of a thermonuclear plasma. The two models are found to be in agreement in the region where the ratio of the ionization length ζj to pellet radius rp is less than unity, but a single parameter, such as the magnitude of this ratio on the sonic surface, is insufficient to determine whether an equilibrium model will be valid for all regions of the ablatant for carbon pellets. Thus a nonequilibrium model is necessary to model the outer regions of the ablatant cloud even for thermonuclear plasma conditions when the cloud is very dense. Also, the effect of the ionization of the ablatant by the incident plasma electrons is found to be 10% or less for even the C+3 region in the thermonuclear regime. Finally, although the model used for the healing of the ablatant by the plasma electrons is that for a neutral carbon ablatant, it is shown that the differences in heating by the plasma electrons between this model and that for an ionized ablatant are small.