BEHAVIOR OF MISALIGNED BEAMS IN A HIGH-INTENSITY PROTON RFQ

Motion of off-centered beams in an RFQ for basic researches on nuclear transmutation was analyzed by using a beam optics computer code. In this analysis not only higher-order harmonics in the intervane potential but also 3D beam-generated forces including image effects were taken into account. Beam loss property and transmission efficiency were investigated for different input beam currents as well as for different injection angles. Results are compared with predictions by the PARMTEQ code. Enhancement of beam displacement at the exit of the cavity as well as increase in transverse beam loss was observed as effects of the image charge force. In any case beam loss due to the image effects was less than 3% of the injected particles. For beam injection angles larger than 1 degrees, the beam transmission efficiency decreased owing to non-linear terms in the intervane potential. Tolerance for the error in beam injection angle into the RFQ cavity is also discussed.