The design and performance of a lowhyphen;energy ion gun system suitable for surface analysis is described. The ion gun system is capable of delivering up to a 0.72 mgr;A beam of Ar+ions at a potential of 500 eV into a spot diameter of 1 mm. This performance is accomplished by using ion optics to refocus the spacehyphen;charge diverging beam along the 44hyphen;cm path to the target. The ion optics have been optimized by the use of a new simulation program,chden, which can model a series of lenses and the effects of spacehyphen;charge forces.
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