Modified Saddle Field Ion Source Using A Ring Focusing Electrode

Abstract

<b> </b>An experimental study of a dc saddle field ion source is reported with a view to maximizing the beam current and insuring extended operation of the source. The dependence of the beam current on geometrical and operational parameters is studied. The electrical characteristics of a dc saddle field discharge were studied using nitrogen gas. This study includes the experimental arrangement for ion beam production from nitrogen gas under the influence of discharge voltages applied to the focusing electrode. Also, different focusing hole diameters are examined and optimized to get a highest efficiency of the ion source. A focusing electrode in the form of a ring is placed at 4 mm from the ion source exit. Different ring electrodes with different exit hole diameters (5, 7, 9, and 11 mm) were used as focusing electrodes. The optimum hole diameter for the focusing electrode was found to be 9 mm where maximum ion beam current can be obtained. It was found that at 9 mm hole diameter, focusing voltage = - 3 kv, and pressure P<SUB>r</SUB> = 8x10<SUP>-4</SUP> mbar using nitrogen gas at distance between two anode rods= 6 mm, discharge region = 5 mm, an ion beam current of 243 µA could be obtained. These data are important for ion beam sputtering, ion beam thinning and in other several applications.