Coaxial guns for the ARPA-E PLX-α project — Design and initial experimental results

We describe the ongoing effort to design, build, and test coaxial plasma guns [1] appropriate for a scaling study of spherically imploding plasma liners as a standoff magneto-inertial-fusion driver under ARPA-E's Accelerating Low-Cost Plasma Heating And Assembly (ALPHA) program. HyperV joins LANL, UAH, UNM, BNL, and Tech-X to develop, build, operate and analyze a 60-plasma-gun experiment using the existing PLX facility [2] at LANL. The guns are being designed to operate over a range of operating parameters: 0.5–5.0 mg of Ar, Ne, N2, Kr, and Xe; 20–60 km/s; 1016–1017 cm− muzzle density; and up to 7.5 kJ stored energy per gun. Each coaxial gun incorporates a contoured gap designed to suppress the blow-by instability, fast dense gas injection and triggering, and innovative integral sparkgap switching. The switch and pfn configurations are designed to reduce inductance, cost, and complexity, and to increase efficiency and system reliability. Each gun is driven by a 600μF, 5kV capacitor bank mounted directly onto the back of the gun to reduce inductance. The pfn is sufficiently low weight to allow mounting of the gun/pfn module directly on the vacuum-tank port without any additional supports. This also eliminates the need for racks and thick-cable bundled transmission lines to 60 guns, resulting in vastly improved experimental access to the vacuum tank, guns, and diagnostics. We will provide a brief overview of the PLX-α project, describe the overall design approach for the guns and pulsed-power systems, the projected performance over the parameter ranges mentioned above, and experimental results from testing of the first gun, AlphaGun-1.