Beam dynamics studies on the ISAC RFQ at TRIUMF

An 8 m long split-ring RFQ linac is being constructed at TRIUMF as part of the ISAC radioactive beam project. The RFQ is designed to accelerate unstable nuclei with q/A⩾1/30 from 2 keV/u to 150 keV/u. Several unusual beam dynamics studies have been pursued during the latter stages of the design. To furnish engineering alignment tolerances, particle tracking in the 10-term potential was performed to estimate the RFQ performance with respect to vane displacement errors; the results are compared with a simple analytical model. In order to explore fringe field effects, particle tracking studies through computed three-dimensional fields at the RFQ entrance and exit were made to optimize the radial matching section (RMS) to the LEBT optics, and to appraise the value of a transition cell. In this paper we describe the methods and results of the beam dynamics simulations and summarize final specifications for the RFQ