EFFECT OF ELECTRON VELOCITY DISTRIBUTION ON THE HEATING OF CORE BY CORONA IN A SPHERICAL PELLET

When a spherical plasma pellet is irradiated symmetrically from all si des by high power laser beams, hot electrons are produced at the plasm a resonance layer. They move in the inward radial direction causing a counter-streaming cold electron current flowing outwardly to maintain the charge neutrality. In general, the interaction between the hot ele ctrons and the counter-streaming cold background electrons leads to br oadening of the velocity distribution of the latter. For a given heat flux, the electron velocity distribution constrained by the requiremen ts for not supporting beam plasma instabilities, predicts a minimum el ectron velocity in the plasma ablation zone. These considerations affe ct the efficiency of heat transfer from the hot corona to the cold cor e. The purpose of this paper is to study the dependence of core-corona coupling on the electron velocity distribution, laser wavelength and other plasma parameters in detail.