Characterization and optimization of a prototype Cs+ surface ionization ion source

The main objective of this work was the characterization and optimization of the brightness and stability of a Cs+ beam generated by a surface ionization source recently developed by the “Unité d’Instrumentation Scientifique” UIS team at the Centre de Recherche Public – Gabriel Lippmann CRPGL. The particular design of this ion source should enable the generation of positive or negative ion beams  with high brightness for challenging surface analysis applications by Secondary Ion Mass Spectrometry. The brightness was determined as a function of the ionizer and reservoir temperatures and of the applied pre-extraction voltage. It was shown that working with extraction voltages below 400 V is not recommendable because of the space charge effect which causes low ion currents. The highest brightness measured was 12 A/cm2/sr. The brightness values determined in this work are probably not the maximal values that can be obtained with the source. Due to sub-optimal vacuum conditions and ion beam stabilization issues, the best possible working conditions of the source have certainly not been reached yet. However, the results obtained so far are a good starting point for further design optimizations with the ultimate objective of obtaining a stable ion beam with a competitive brightness as compared to the currently available Cs+ ion sources.