How Shock ignition can help to overcome the negative effects of hot electrons in direct-drive high-gain inertial confinement fusion

Abstract

Hot electrons produced by parametric instabilities can negatively affect the thermonuclear gain of a direct-drive inertial confinement fusion capsule. A Monte Carlo transport is coupled to the hydrodynamics MULTI-IFE code in order to study the hot electron transport in a high-gain target implosion. The thermonuclear energy produced by the directly driven implosion of a reference target drops from 27 MJ without hot electrons to 13.5 kJ when the hot electrons are taken into account. A clear relationship is established between the level of hot electrons produced and the degradation of the thermonuclear yield produced by the target. It is shown that adding a relatively short laser spike (shock ignition) to the main pulse restores the thermonuclear energy released by the implosion. Different shock-ignition windows are presented depending on the duration of the spike. It appears that the longer the duration of the spike, the lower the power required for shock ignition. Finally, a 300 ps-duration spike requires only 50 TW to restore a thermonuclear energy output of 20 MJ.