Experimental study of a stellatron accelerator using plasma start-up

Formation and acceleration of a high-current electron beam in a stellatron were studied. The apparatus had a 41 cm major radius and 4 cm minor radius torus, which was pumped down to 10-7 Torr. Plasma was injected into the torus and confined in a rising stellarator field. A runaway current of up to a few kiloamperes was induced when applying the betatron field. Beams of over 1 kA and with a current density of approximately 1 kA/cm2 were accelerated to several million electron volts with little loss. A 1 kA, 10 MeV beam was observed by initially forming a 2 kA beam. The loss was associated with negative-mass instability and high-mode orbital resonances