SIMION simulation studies for sputter negative ion sources

Sputter negative ion sources are known to produce varieties of negative ion beams for experiments. SIMION simulation studies are performed on NEC manufactured three versions of sputtering sources: (i) SNICS (ii) MCSNICS with cesium focus lens (MC-SNICS-I) and (iii) MC-SNICS with immersion lens (MC-SNICS-II) to explore the roles of many factors such as geometrical shape in beam forming area including the ionizer shape, cesium focus lens shape on ion source efficiency and its beam quality. The first two sources have conical ionizers; third one has a spherical shape ionizer. Extraction electrode geometries are different for these sources. The trajectories of Cs+ beam with and without space charge effect for various cathode voltages are performed. Simulations are performed for detailed study of secondary negative ion beam extraction and transportation along the beam line. MC-SNICS versions have more focused and intense Cs+ beam spot at the cathode surface. Due to this, they are much better in ion beam production with lower emittances. Geometry in ion beam forming area not only plays major role in ion beam production efficiency but also helps in operation of the source. MC-SNICS with immersion lens geometry effectively uses the sample material. This geometry reduces breakdowns caused by cesium and thereby minimizes frequency of servicing of the source. (author)