Analytic insights into nonlocal energy transport: Steady State Fokker Planck theory in arbitrary Z plasmas

Abstract

The generation of energetic electrons in laser fusion in an important issue. The electrons may either arise from a laser plasma instability, or from the uncoupled high temperature tail of a Maxwellian distribution. To study these in a laser fusion context, it is important to find a method accurate enough to be useful, and simple enough to be incorporated into a radiation hydrodynamics numerical simulation, the main workhorse for studying the laser fusion target. That is why analytic insights become important, they allow one to simplify the Fokker Planck theory so that a solution of it can be incorporated into a radiation hydrodynamic (rad-hydro) simulation. This work develops and analyzes a steady state Fokker Planck theory for plasmas of arbitrary Z. It developes a method of solving the simplified Fokker Planck method with a technique called sparse eigenfunction analysis. This method appears to work reasonably well when compared to the experimental results from the Rochester/NIF on plastic spherical targets with and without a silicon layer.