Transport of long--mean-free-path electrons in laser-fusion plasmas

The Fokker-Planck kinetic equation for suprathermal electrons which are confined in a spherical plasma by the sheath potential and collide with colder denser electrons and ions is investigated. In the region where the collisional mean free path, lambda, is longer than the spatial scale length, L, the kinetic equation is reduced by averaging it along an orbit between reflections by the sheath. The electrons are seen to diffuse in impact parameter relative to the plasma core while slowing down in velocity. The resulting heat flow scales as (L/lambda) n/sub s t h/mv/sub s t h/3