Short laser pulse induced generation of hot electrons and their anomalous stopping in overdense plasmas

In the fast ignition (FI) scheme of inertial confinement fusion, the igniter pulse falls on a precompressed overdense target and hence is unable to penetrate it. Thus, for the task of hot spot generation one has to rely on energetic electrons which are produced by the laser pulse at the critical surface. These electrons subsequently move towards the target core and deposit their energy in a sufficiently localized region. It is thus clear that the production of hot electrons by the incident sub-picosecond laser pulse at the critical surface and their subsequent transport in the overdense plasma region are the two main physics issues which are of relevance to the FI scheme. An experimental study and theoretical analysis which may be of relevance to these two issues are presented here. The study shows that the production of energetic electrons occurs through the wave breaking of plasma waves excited at the critical surface by the incident laser beam. Further, the propagation of hot electrons through the overdense region is influenced by electrostatically induced and/or by turbulence induced anomalous resistivity.