Energy-transport experiments in 10-μm laser-produced plasmas

Abstract
X‐ray experiments were conducted giving data on radiation and electron transport from plasmas produced by the interaction of 10.6‐μm laser light focused on layered targets. The targets employed were evaporated aluminum on SiO2 and copper substrates. The penetration depth of the plasma was measured from the thickness of aluminum required to produce a 1/e attenuation of the highly ionized silicon lines (1s 2p‐1s2) and (1s 3p‐1s2). The penetration of the plasma into the target surface was 95 Å for incident 10.6‐μm laser irradiances of 3×1013 W/cm2. Estimates of electron energies produced in the plasma directed toward the target were made from measurements of the attenuation of the K line of the substrate as a function of aluminum thickness. End‐point electron energies were calculated from the best fit of experimental data with targets of SiO2 and copper substrates for laser irradiances from 3×1013 to 4×1014 W/cm2. When the laser irradiance (IL) is increased, there is an increased dependence of electron energies absorbed by the target. For irradiances greater than 1014 W/cm2 the effective end‐point energy is proportional to I1/2L.