Thermal Soft X-Rays Interaction with foam Layered Gold Targets

Abstract

The purpose of the experiment presented in this paper was to study the effect of low density foams on the generation of shocks driven by thermal soft X-rays because of their applications in Inertial Confinement Fusion (ICF)^1-4. Experiments were performed at MPQ, Garching using Asterix laser energy up to 400 J at 0.44 μm (3ω of Iodine laser) in ≈ 450 ps (FWHM). A conical shaped shield was constructed inside the Labyrinth cavity⁵ so that the laser irradiated area and the shocked material are not in direct view of each other (Fig. 1). Cavity surface area was equivalent to a sphere surface area of radius 0.5 mm. Target specifications are, 1) Aluminium base of thickness 16.95 μm with Al step of thickness 6.23 μm. 2) gold base of thickness 4.96 μm with a 1.95 μm gold step. The front surface of the gold foil was layered with low density foam (TMPTA-trimethylol propane triacrylate, C₁₅H₂₀O₆) of 50 μm thickness, ρ = 20 mg/cc, and also 50, 100 and 150 μm thick with ρ = 50 mg/cc). The areal densities were d = 0.1, 0.25, 0.5 and 0.75 mg/cm² respectively. A visible streak camera recorded the shock breakout signal.