Technological and physical aspects of a constricted RF ion source

Experimental results are given for the perveance at different pressures and RF power using nitrogen and argon ions. The results are taken using a constricted axial RF ion source with an aspect ratio of the radius of the outlet aperture to the extraction gap width equals 0.4. Our data confirm the validity of the current scaling law at RF power equals 50 watt 20 watt in case of nitrogen and argon gases respectively at a pressure of 3 μHg. It is found that by increasing the pressure the beam current will decrease. Therefore, in order to keep the beam current constant, the RF power must be increased. In case of nitrogen, at a perveance of 0.24×10^-8 Amp/V^3/2 corresponding to a pressure of 0.03×10^-8 Amp/V ^3/2 corresponding to a pressure of 25 μHg, it reduces to 1.2°. In case of argon, at a perveance of 0.12×10^-8 Amp/V^3/2 corresponding to a pressure of 3 μHg, the beam divergence is 7.2°, while at a perveance of 0.02×10^-8 Amp/V^3/2 corresponding to a pressure of 25 μHg, it becomes 3.2