Fusion Science and Technology / Volume 64 / Number 4 / November 2013 / Pages 762-786
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.