Ablation of a solid obstacle with a radiative shock driven by gas gun plate impact

Radiative ablation of solid obstacles by a radiating shock in low-pressure gas has previously been observed in laser-driven experiments [T. Vinci et al., Phys. Plasmas 13, 2006; M. Koenig et al., Phys. Plasmas 24, 2017]. At First Light Fusion Ltd, we are motivated to study the phenomena in relation to our ‘projectile fusion’ research, where solid surfaces in our targets are irradiated by shocks propagating through low-pressure gas mixtures. Experimental data of this effect is needed to benchmark our in-house radiation hydrodynamics code Hytrac.

We report on an experimental platform to produce a radiative shock driven purely hydrodynamically, using a two-stage light gas gun. The initial shock from a 6.5 km/s plate flyer impact is amplified and increased in strength inside the 'amplifier' target. The release from the amplifier exit drives an 80km/s shock into a gas cell, which is imaged using streaked optical shadowgraphy.

A 125 μm aluminium wire is placed inside the gas cell 2 mm from the amplifier exit and is heated by the radiation from the shock. Simulations using Helios [2017 Prism Computational Sciences, Inc.] and Hytrac predict over 200 μm of expansion when a 250 mbar argon gas fill is used. Comparisons to experimental data are presented.