Design study of an energy-variable RF-accelerator for ion implantation

Abstract New applications in ion implantation (e.g. SIMOX, metal surface improvement) require a large penetration depth as well as very high implant doses. Both requirements — high ion energy and high beam current — can be satisfied at the same time by rf accelerators. In this paper we present a design of an rf acceleration system consisting of a Radio Frequency Quadrupole-(RFQ)-Accelerator and a Spiral Loaded Cavity. In contrast to common rf accelerators in this design the exit energy is variable over a large range in spite of a constant resonance frequency, which is achieved by splitting the RFQ into two parts. The first part serves for bunching and preacceleration of the ions, whereas the second part operates at different amplitudes and phases and accelerates the ions to various final energies. A continuous energy range is then obtained by the Spiral Loaded Cavity which is coupled to the RFQ. The design study has been carried out for the acceleration of 5–10 mA oxygen ions and an input energy of 50 keV. The projected output energies extend from 0.5 to 1.7 MeV.