Results on intense beam focusing and neutralization from the neutralized beam experiment

The use of stray electrons to provide active neutralization for space-charge-dominated beams and to prevent uncontrolled ion beam neutralization was discussed. The neutralization was provided by a localized plasma injected from a cathode arc source. The unwanted secondary electrons produced at the wall by halo particle impact were found to be suppressed using a radial mesh liner that was positively biased inside a beam drift tube. The results show that, when the NTX beams was neutralized by passing it through a MEVVA plasma, the focal radius decreases to 1.26-1.4 mm, compared with the 1 mm spot size found in perfect neutralization.