Relative importance of mega electronvolt-electron energy deposition by collisions and field effects in fast ignition

Abstract

The rates of energy deposition of MeV electrons by return-current Ohmic heating and Coulomb collisions are compared in the context of the fast ignition scheme of inertial confinement fusion. A criterion for distinguishing the relative importance of the two heating mechanisms is presented. It depends on the kinetic energy of the relativistic electrons, the temperature of the background plasma, as well as the ratio between the densities of the two groups of electrons. A critical density ratio is also found.