An axial geometry cesium sputter negative ion source with continuous tungsten surface ionizer

Abstract

A high brightness axial geometry negative ion source has been designed, developed, and used as an “on-line” source for routine operation of the Holifield Heavy Ion Research Facility tandem accelerator. The present source utilizes a continuous surface, solid tungsten ionizer to effect ionization of cesium vapor which, in turn, is used to sputter a negatively biased probe containing the material of interest. Operational experience with the source indicates that the source is reliable, long lived, stably operating and a prolific producer of a wide spectrum of negative ions. To date the source has been used to produce more than eighteen negative ion species including Ag −, Au −, B −, CaH 3 −, Cl −, CrH 2 −, Cu −, Lu −, MgH 3 −, Mo −, Ni −, O −, S −, Si −, Sn −, TiH 3 −, Tm −, and Yb −. Details of the mechanical design features and computational techniques utilized in arriving at the final electrode configuration are presented in the text. Data pertinent to source operation, the dependence of negative ion yields on certain source operational parameters, and examples of intensities typical of particular negative ion species are also given.