Simulation of an RFQ funnel for heavy-ion beams

It is pointed out that the use of the magnetic force to focus and deflect heavy-ion beams is marginal at low ion velocities, and that low-emittance-growth funnels using discrete magnetic elements are difficult to design for these beams. It is shown that a new type of radio-frequency quadrupole (RFQ) funnel is especially suitable for this application. Simulation procedures, which include space-charge and image effects, have produced a high-quality funnel design for 20-MeV Bi⁺¹ ions. In this arrangement, two separate RFQ accelerators produce slightly convergent beams that are combined by the RFQ funnel. The funnel provides deflection (and focusing) forces in separate RFQ channels that first make the two beams closely space and nearly parallel. Then the two beams enter a common channel where they are interlaced and made collinear