Minirailgun accelerator for plasma liner driven HEDP and magneto-inertial fusion experiments

摘要

Summary form only given. A spherical array of minirailgun plasma accelerators is a potential driver for forming imploding spherical plasma liners that can reach HEDP-relevant (~0.1 Mbar) pressures upon stagnation. The liners would be formed via merging of 30 or more dense, high Mach number plasma jets (n ~ 1016-17 cm-3, M -10-35, v ~ 50-70 km/s, tau_jet ~5 cm) in a spherically convergent geometry. The small (typically 1-2 cm square bore x 15-50 cm length) parallel-plate railguns with ceramic insulators would use pulsed injection of high-Z gas at the breech via fast opening valves to produce high density plasma jets with velocity in the 50-100 km/s range. Recent tests at HyperV using a single pulsed capillary discharge injecting into the minirailgun breech have achieved plasma densities in the bore approaching 1018 cm-3, with densities in the jet plume exceeding 1017 cm-3 at velocities above 50 km/s. Total plasma jet mass in these 1 cm square bore tests has not yet been determined, but similar tests of an earlier 6 mm square bore 13 cm long device, with a roughly 3 mus, 100 kA current pulse using an aluminized mylar fuse starting from rest, yielded 90 mug of plasma at 50 km/s, and about 40 mug at 63 km/s. A modest scaleup of the railgun to a 2 cm square bore operating at longer pulse widths of 200-300 kA should be capable of accelerating a few thousand micrograms of high-Z gas (e.g. xenon) to above 50 km/s. This performance should be sufficient for reaching HEDP-relevant pressures.