Hot-electron distribution functions in a subpicosecond laser interaction with solid targets of varying initial gradient scale lengths

We have studied the distribution function of the hot electrons produced dur ing the interaction of a 120-fs, 60-mJ, 800-nm wavelength and a p-polarized laser pulse with bilayered Al/Fe targets. The main pulse interacts with a preformed plasma, obtained with a controlled prepulse, whose density gradie nt scale length has been measured. The electron distribution function is ch aracterized by means of the K alpha emission of the two materials of the ta rget asa function of the Al-layer thickness. The low-energy region (<50 keV ) of the hot-electron distribution function shows no dependency in shape on the gradient scale length, but only a variation in the total number of the generated electrons. The comparison between the experimental results and t he particle-in-cell and Monte Carlo calculations of the electron distributi on function and the K alpha emission is gratifying. [S1063-651X(99)07209-8] .