Beam dynamics of a double-gap acceleration cell for ion implantation with multiple atomic species

摘要

As a result of our work on ion implantation, we derived equations for the beam dynamics of a two-gap-resonator cavity for accelerating and bunching various ion species of varying energies with the cavity designed for one particlular ion species of a given energy (the design-reference particel). A two gap structure is useful at low resonant frequencies where lumped circuit elements (inductors) can be used and the structure kept small. A single gap structure has the advantage that ach gap can be independently phased to produce the desired beam dynamics behavior for various ion species and ion energies. However at low frequencies, single gap resounant structures can be large. We find that the two-gap structure, where the phase difference between gaps, for the design reference particle, is fixed at #pi# radians can give acceptable performance provided that the individual two gap cells in the entire acceleator are optimized for the ion species having the largest mass to charge ratio and having the maximum required output energy. Our equations show how to adust the cavity phases and electric fields to obtain equivalent first-order accelerator performance for various ion species and energies. These equations allow for the effective evaluation of various accelerator concepts and can faciitate the tuning of a linac when changing energies and ion species. Extensive simulations have confirment the effcacy of our equations.