KINETIC EFFECTS ON THE ELECTRON THERMAL TRANSPORT IN IGNITION TARGET DESIGN

Preheating is one of the most critical issues in laser fusion, because of significant reduction of volume compression. The nonlocal heat tra nsport in an ablative plasma is found to play an important role in the preheating under high intensity laser irradiation. Namely, the electr on heat transport should be described by the Fokker-Planck (FP) equati on in the fluid implosion code. The Spitzer-Harm (SH) thermal conducti on model is not applicable because the electron mean free path is comp arable. to the temperature scale length. The numerical simulations of the implosion with the FP heat transport have been carried out for the fast (high entropy) implosion mode in which the implosion velocity re aches as high as 6x10(7) cm/s. In the fast implosion, the required las er energy for ignition can be reduced, It is found in the simulation t hat the isentrope in the FP simulation code is higher by two to four t imes than that in the flux limited SH simulation. (C) 1996 American In stitute of Physics.