Direct-indirect hybrid mode implosion in heavy ion inertial fusion

Abstract

A direct-indirect hybrid implosion mode is proposed and discussed in heavy ion beam (HIB) inertial confinement fusion (HIF) in order to release sufficient fusion energy in a robust manner. On the other hand, the HIB illumination non-uniformity depends strongly on a target displacement dz from the centre of a fusion reactor chamber. In a direct-driven implosion mode, dz of ~ 20 μm was tolerable, and in an indirect-implosion mode, dz of ~ 100 μm was allowable. In the direct-indirect mixture mode target, a low-density foam layer is inserted, and the radiation energy is confined in the foam layer. In the foam layer the radiation transport is expected to smooth the HIB illumination non-uniformity in the lateral direction. Two-dimensional implosion simulations are performed, and show that the HIB illumination non-uniformity is well smoothed in the direct-indirect hybrid-mode target. Our simulation results present that a large pellet displacement of ~ a few hundred μm is allowed in order to obtain a sufficient fusion energy output in HIF.