Energy Deposition Of Fast Electrons In Compressed Targets Of Fast-Ignition

The interaction of a MeV electron with a dense plasma is studied in the context of inertial fusion fast ignition. Fast ignition, an alternative approach to inertial confinement fusion(ICF), has recently attracted significant attention. In this scheme, different from the conventional approach to central hot-spot ignition, a pre-compressed DT target will be ignited by an external spark. Fast ignition relax the conditions on target compression and reduce the total energy requirements for ICF ignition, leading to higher target gain. Successful realization of fast ignition requires understanding and controlling of the transport and energy deposition of MeV electrons in the target.We are entitled to restrict ourselves to a continuous slowing down approximation because large and sudden energy losses are likely to happen very rarely over the energy range considered in this paper, radiative losses contribute can be neglected. Also, electron-position pair production remains totally negligible. In the context we considered, self-generated electromagnetic fields play a minor role and we neglect them. It is shown that classical stopping and scattering dominate electron transport and energy deposition when the electrons reach the dense plasmas in the cores of compressed targets.In our paper , fast electron energy deposition was addressed in slowing down theory. Although the derivation shown here borrows heavily from other work, it improves the slowing down theory by fixing some inaccuracies appearing in previous. The stopping power of fast electrons due to binary collisions come from the paper of Robiche. Contrary to previous work, we obtained the new total stopping power due to both binary collisions and plasma wave excitation. In order to take into account plasma screening of distant interaction, we use cross-sections accounting for plasma screening, without introducing any artificial long distance cut-off. We obtained different the first-and second-order spatial moments of the electron-distribution by using the multiple-scattering theory of Lewis.Furthermore, the mean penetration, the longitudinal straggling and the beam blooming were given. The fundamental dependence of the mean penetration on plasma density, Z, temperature are discussed in the paper.