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

Experimental techniques to provide active neutralization for space-charge-dominated beams as well as to prevent uncontrolled ion beam neutralization by stray electrons have been demonstrated. Neutralization is provided by a localized plasma injected from a cathode arc source. Unwanted secondary electrons produced at the wall by halo particle impact are suppressed using a radial mesh liner that is positively biased inside a beam drift tube. Measurements of current transmission, beam spot size as a function of axial position, beam energy, and plasma source conditions are presented along with detailed comparisons with theory.