Negative ion source improvement by introduction of a shutter mask

Studies of a multicusp source were recently done at the National Institute for Fusion Science by plasma grid masking. The maximal H- ion yield is similar to1.4 times greater for the shutter mask case than that for the standard source. Negative ion current evolution during the cesium feed to the masked plasma grid evidenced that about 60% of negative ions are produced on the shutter mask surface, while about 30% are formed on the plasma grid emission hole edges, exposed by cesium with the mask open. (C) 2004 American Institute of Physics.