A plasma target for neutralization of the negative ion beam

Abstract

Abstract.The results of the experimental study of build-up and confinement of low-temperature plasma target for neutralization of high energy negative ion beam are presented in the paper. The cylindrical vacuum chamber of the plasma target is 1.2 m long and 0.2 m in diameter. The axisymmetric multicusp magnetic field is formed at the periphery of the target chamber by using an array of the permanent NdFeB magnets, which are placed closely on the thin chamber walls. The target chamber is ended by the two diaphragms with 0.1m diameter apertures for the negative ion beam passing through. For reduction of the plasma losses through the ends, the inverse magnetic field are formed in the apertures .The plasma is produced in the target by ionization of the working gas by electrons, which emitted by six plane LaB 6 cathodes, which are placed uniformly over azimuth at the center of the plasma target. The discharge duration is set to 1 s. In short pulses at 300 kW power, the hydrogen plasma with density is produced. Spatial profiles of the plasma parameters in the target were measured.

On suitable experiments for demonstrating the feasibility of the beam-driven plasma neutraliser for neutral beam injectors for fusion reactors

“…In large systems, the D + 2 ions created through gas ionisation by the fast electrons are rapidly converted either into D + 3 ions by colliding with the gas molecules or into D + ions through the dissociation reaction (15). The D + 2 and D + 3 ions are simultaneously also lost because of dissociative recombination (reactions ( 12) and ( 13)).…”

“…The neutralisation yield was increased from 55% without plasma in the neutraliser to 65% with plasma at an optimal target thickness that was only 65% of that required in the gas neutraliser case. Besides creation of the plasma by arcs [14,15], neutraliser plasma generation by electron cyclotron resonance (ECR) was also suggested and demonstrated [16].…”