Design and operating characteristics of a low pressure ion source

The operating characteristics of various designs of the twin anode electrostatic ion source are described. The ion extraction system has been modified to improve the efficiency of the source and increase the ion beam intensity. A water cooled source has been produced which is very stable and has been used continuously for many hours without any deterioration in performance. A thermionic version of the source has also been constructed which should be suitable for ultra high vacuum and produces ions of average energy of several 100 eV. Scanning electron micrographs of a cadmium sulphide field-ion emitter tip which has been ion sharpened with this source are given to illustrate one of its important applications. (auth.)