TiH₂/C₆₀ Cartridge Injector of Plasma Jet System for Disruption Mitigation in Tokamaks

Disruption mitigation in tokamaks by impurity injection aims to reduce the heat load and mechanical forces and to collisionally suppress runaway electrons. Rapid injection of sufficient mass, high penetrability, and large assimilation fraction in the core plasma together with rapid impurity redistribution over the whole plasma are required. FAR-TECH Inc. proposed the innovative idea of using hypervelocity ([greater-than or equivalent to]4 km/s), high-density ([greater-than or equivalent to]10¹⁷ cm⁻³), high-ram-pressure C₆₀ nanoparticle plasma jets to deliver the impurity mass in [approximately]1 ms. For this purpose a large C₆₀ gas mass of explosively sublimated powder, generated by a solid-state, pulsed-power-driven source injector cartridge containing TiH₂ grains and C₆₀ powder, is ionized and accelerated in a plasma accelerator. We report here the characterization of the TiH₂/C₆₀ injector cartridge using a 5-kJ capacitive driver, which produced up to [approximately]210 mg of C₆₀ gas in <0.5 ms. The TiH₂/C₆₀ cartridge is the key component of the 100-kJ coaxial plasma gun ([approximately]35-cm length) prototype developed for a proof-of-principle experiment on a tokamak. Three-dimensional simulations show that a heavy C₆₀ plasmoid penetrates deeply, as a compact structure, through a transverse magnetic barrier.