Measurement of the fast electron distribution in laser-plasma experiments in the context of the “fast ignition” approach to inertial confinement fusion

The recent “fast ignition approach” to ICF relies on the presence of fast electrons to provide the “external” ignition spark triggering the nuclear fusion reaction in the compressed core of a thermonuclear target. Such fast electron beam is produced by the interaction of a short-pulse high-intensity laser with the target itself. In this context, it becomes essential to characterize the density of fast electrons and their average energy (i.e. the “laser to fast electron” energy conversion efficiency) but also the finer details of the velocity and angular distribution. In this work we will discuss several techniques used to determine the fast electron distribution function.