A short superconducting RFQ resonator for slow ion beams

The radio frequency quadrupole can be used as a superconducting linac structure for heavy ions produced by an ECR source. The concept of the RFQlet, a short RFQ, resonator is described. The RFQlet combines the advantages of rf quadrupole focussing with the wide transit time factor curve, low stored energy, small size and flexibility of the individual resonator approach, common to many modern booster linacs. One interesting form of RFQlet is the RFQW resonator, an RFQ geometry with just two accelerating gaps based on the quarter wave resonator, having the same transit time factor curve of the QWR.