Small multicusp H− source

Abstract

High‐quality H⁻ beams have been generated from a multicusp source equipped with a permanent magnet filter. It is shown that a large improvement in H⁻ yield can be achieved by employing a small multicusp source, fabricated with the proper wall material and extraction chamber length. From this small source, H⁻ current densities higher than 250 mA/cm² have been extracted from a 1‐mm‐diam aperture for a discharge voltage of 150 V and a discharge current of 450 A. When the source is operated with deuterium, the extractable negative ion current density is reduced by approximately 30%.