Acceleration of cocktail ions at the JAERI AVF cyclotron

The ion species and energy of a cyclotron beam can be quickly changed using a cocktail acceleration technique. Cocktail beams of mass-to-charge (M/Q) ratio of 4 and 5 have been developed at the JAERI AVF cyclotron. Purity of the beam depends on the M/Q resolution of the cyclotron. The resolution has been estimated theoretically and experimentally. A radial spread of an internal beam bunch caused by phase slip of particles with a different M/Q value has been observed using a pulsed incident beam. For practical operation, some methods have been devised for avoiding intermixture of different ion species in a beam extracted from the cyclotron.