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