A compact, lightweight, variable-energy cyclotron for conventional and FLASH ion beam

The advantage of ion beam radiotherapy for cancer lies in its low dose proximal and distal to the tumor, owed to an energy-dependent depth-dose profile, the Bragg-peak. We present a new conceptual accelerator design that provides smooth variation of the output beam energy from 70 to 230 MeV/amu without degraders, which compromise the quality and intensity of the beam and produce secondary radiation. Removing all magnetic iron from the device yields a linear relationship between coil current, cyclotron magnetic field, and, thus, the output beam energy. Hence, we create a much lighter system with improved magnetic shielding and significantly reduced secondary radiation that can provide ion beams (e.g., proton or carbon) at variable energy while providing the high beam intensity necessary for the promising FLASH technique at all output energies.