Understanding ion deceleration lenses: What are the simplicity/performance trade-offs?

The traditional approach for obtaining highly collimated low energy (<200 eV) beams from high-energy (1-10 keV) sector mass spectrometers involves the use of a complex exponential deceleration lens assembly. Through ion optical modeling of the exponential lens and other less-complex lens designs, the fundamental features that contribute to deceleration lens performance are investigated. From this evaluation, a simple high-performance lens was designed, constructed, and characterized. The novel lens described here decelerates a 3-keV ion beam down to the 3-200-eV range while providing low angular divergence, excellent focusing, and good transmission.