New concept positive (negative) surface ionization source for RIB applications

摘要

A versatile, new concept, spherical-geometry, positive (negative) surface-ionization source has been designed. fabricated, and tests completed which can operate in either positive- or negative-ion beam generation modes without mechanical changes to the source. The highly permeable, composite Ir/C has an intrinsic work function of 0 = 5.29 eV and can be used directly for the generation of positive-ion beams of highly electropositive elements. For negative-surface ionization, the work function is lowered by dynamic flow of a highly electropositive adsorbate such as Cs through the ionizer matrix. The results of initial testing indicate that the source is reliable, stable and easy to operate, with efficiencies for Cs(sup +) estimated to exceed 60% and as high as (approximately)50% for F(sup -) generation. The design features, operational principles, and initial performance of the source for generating Cs(sup +) and F(sup -), when operated with Cs, are discussed in this article.