An ion source for low energy ion scattering spectrometry

Abstract

The alkali ions have been of interest in low energy ion scattering experiments because of their low neutralization probabilities. A method to produce alkali ions has been developed based on the surface ionization technique. A modified surface ionization source uses a sawtooth type sample filament to maintain the slow evaporation of the alkali samples doped on it, and a flat ribbon ionization filament in parallel to it to ionize the alkali vapour. Different alkali compounds have been tried, and high ion currents in the μ A range with the life span of more than 20 h have been obtained using the beta-eucryptite compounds. The intensity of the ion beam can be maintained at a constant value when the operation of the ion source reaches the steady state in less than 30 min. Most ions were singly charged atomic ions with energy spread in the order of 1 eV.