Experimental evidence of differences in properties of fast ion fluxes from short-pulse and long-pulse laser-plasma interactions

Essential differences in properties of fast ion fluxes from the interaction of 1 ps and 0.5 ns laser pulses with Au target have been observed. In the short-pulse case, only a single fast ion group with a small angular divergence is generated and ions are likely to be accelerated by an axial ponderomotive force from the skin-layer interaction. In the long-pulse case, at least two groups of fast ions are emitted into a wide solid angle and the ion flux properties seem to be determined by self-focussing of the laser beam in plasma. (C) 2003 Published by Elsevier B.V.