New nonscaling FFAG for medical applications

A hybrid design for a fixed-field alternating-gradient (FFAG) accelerator has been invented which uses edge and alternating-gradient focusing principles applied in a specific configuration to a combined-function (CF) magnet to stabilize tunes through an acceleration cycle which extends over a factor of 6 in momentum. Using normal conducting magnets, the final, extracted energy from this machine can attain slightly more than 400 MeV/nucleon without the use of superconducting elements. By using fixed-fields, the machine proposed here has the high current advantage of the cyclotron yet retains important features of the synchrotron: smaller radial aperture, variable energy, and both kicker-based and resonant extraction. This machine, without modification, supports a proton and a carbon ion beam in the energy range of interest for cancer therapy. Competing machines for this application include superconducting cyclotrons[1], synchrotrons [2], and, more recently, scaling FFAGs. As such this machine represents a broad innovation in therapy machines.