Recent advancements in sputter-type heavy negative ion sources

Significant advancements have been made in sputter-type negative ion sources which utilize (1) direct surface ionization or (2) a plasma to form the positive ion beam used to effect sputtering of samples containing the material of interest. Typically, such sources can be used to generate unstable beam intensities of a few microamperes to several milliamperes from all chemically active elements, depending on the particular source and the electron affinity of the element in question. An introduction to the fundamental processes underlying negative ion formation by sputtering from a low-work-function surface is presented. Several sources which reflect the progress made in this technology are described