K alpha emission measurements and superthermal electron transport in layered laser-irradiated disk targets.

We report results from an experimental study of superthermal electron energy transport in planar layered disk targets irradiated at high intensities (Ig3\ifmmode\times\else\texttimes\fi{}${10}^{14}$ W/${\mathrm{cm}}^{2}$) by short (l100-psec) pulses of Nd-laser radiation. The K\ensuremath{\alpha} emission from a Ni fluor covered by an Al electron-transport layer has been recorded both spatially integrated and spatially resolved over the target surface. By analyzing the results, with the aid of a Monte Carlo electron-transport code, it has been found that electron transport within the target is dominated by a non-Maxwellian group of very energetic electrons (${E}_{e}$\ensuremath{\approxeq}50--200 keV) which carry about 3% of the absorbed laser energy deep within the targets. The spatial distribution of the electrons over the target surface underlines the effect of the coronal magnetic and electric fields on lateral energy transport by superthermal electrons.