Characteristics of a high frequency ion source used in a low-energy accelerator

The characteristics of a high-frequency ion source operating on a low energy, 150 keV accelerator are discussed. The theoretical analysis on which the design of the accelerator is based is presented. It is shown that inward electric forces will counterbalance space charge forces tending to blow up the beam if the axial potential in an electrostatic electrode system is increased with four thirds the power of the axial distance. The resulting, simplified acceleration tube is shorter and of a higher gradient than conventional acceleration columns. The ion source uses axial extraction of the beam. The influence of such parameters as anode extraction potential and cathode shield height on the extracted ion current is investigated, and phase-space characteristics of the beam with and without acceleration are determined.