Quantitative spatiotemporal density evolution of aluminum heated purely by monochromatic electrons

Abstract

A spatially resolved air-wedge shearing interferometer and shadowgraph diagnostic provides measurements of electron density with a resolution of [Formula: see text]40 [Formula: see text]m. A [Formula: see text]100-ns-long, monoenergetic electron bunch at 19.8 MeV and a current of 1.4 kA ([Formula: see text] [Formula: see text]) heats 100-[Formula: see text]m-thick aluminum (Al) foils in a 1-mm-spot to [Formula: see text] eV. A 5-ns-long, [Formula: see text]60 mJ, frequency doubled Nd:YAG laser probes the dense Al plasma. Electron densities up to [Formula: see text] are resolved; the maximum resolvable density is limited by opacity, transmission, and spatial fringe density achievable with the detector. This diagnostic provides measurements of the total phase shift, transmission, and electron density. Several measurements at different time slices provide the ability to determine the velocity of the leading edge of the shadowgraph and compare it to the motion of different density shells. These measurements are also compared to radiation hydrodynamics simulations. A rough quantitative agreement is shown between the hydro simulations and the measurements; there are differences in the exact density distributions.