A plasma target for neutralization of the negative ion beam

Abstract

The results of the experimental study of confinement of low-temperature plasma target for neutralization of high-energy negative ion beam are presented in the paper. The plasma target cylindrical vacuum chamber 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 the two 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 [1]. The plasma is produced in the target by ionization of the working gas by electrons, which emitted by six plane LaB6 cathodes, which are placed uniformly over azimuth at the center of the plasma target near the wall. The plasma parameters were define from Langmuir probes measurements and from recharge of diagnostic atomic beam. In short pulses at 220 kW power, the hydrogen plasma with density ni ≈ 2 · 1013 cm−3 is produced. Degree of plasma ionization reaches 50 %.