New target designs for direct-drive ICF

Abstract

We describe two approaches to the design of a direct-drive high-gain pellet for inertial confinement fusion reactors that has enhanced stability due to the reduction in the Rayleigh-Taylor growth rate and enhanced thermal smoothing of laser imprint. The first design incorporates an overcoat containing a high-Z element that radiatively heats the ablator during the foot of the laser pulse. The second incorporates a very low density foam ablator that is compressed by a series of transmitted and reflected shocks. Both designs enhance thermal smoothing by developing a very long density scale length and high electron densities in the ablator blowoff.