Fokker Planck and Krook models for nonlocal energy transport in laser produced plasmas*,

Several Krook models have appeared in the literature attempting to describe nonlocal electron energy transport, but there seems to be little consensus. We find that all models so far have had errors, which we hope to correct. One of the main ones involves the Coulomb Logarithm, which is the log of the ratio of maximum to minimum impact parameters in a collision. Using local parameters, instead of the actual nonlocal energies actually involved in the collision gives in some cases a value too small by a factor of between 3 and 5. We have derived approximate analytic solutions for nonlocal transport, which can be used to check and guide more detailed code results. We find that in general, the fuel preheat is significant. However we have also developed a Fokker Planck model and come up with approximate steady state solutions for it. We find that this latter model gives much less preheat. We explain this in terms of the differences between the two collision processes.

*^@ Consultant to NRL through RSI Corporation, wallymanheimer@yahoo.com

^# Consultant to NRL through Syntek Technologies