Beam dynamics design of a new radio frequency quadrupole for beam-current upgrade of the Japan Proton Accelerator Research Complex linac

Abstract

We have performed the beam-dynamics design of an H^{-} radio frequency quadrupole (RFQ) for the beam-current upgrade of the Japan Proton Accelerator Research Complex linac (RFQ III). LINACSrfqDES was set up to support the conventional design method, i.e., design with CURLI-type shaper followed by constant bore radius and with constant intervane voltage, supplemented by keeping the equipartitioned condition in the gentle buncher section. For the particle simulation, LINACSrfqSIM was used. The obtained transmission, transverse and longitudinal emittance are 98.5%, 0.21π mm mrad, and 0.11π MeV deg for the input beam current of 60 mA and normalized rms emittance of 0.20π mm mrad. This design satisfies the requirements of RFQ III.