Racetrack Fixed Field Accelerator with pulsed quadrupoles for variable energy extraction

Abstract: In this paper, a novel concept combining a fixed field alternating gradient accelerator with time-varying quadrupoles is presented which solves some of the major problems of conventional fixed field accelerators. This concept combines a stable racetrack fixed field configuration with dispersion free straight sections to enable continuous variable energy extraction. In the long straight sections, a time-varying synchrotron-like alternating gradient focusing structure makes it possible for the first time to correct the beam optics of an FFA accelerator in order to heuristically maximize the beam transmission by minimizing the tune excursion and avoiding the crossing of harmful betatron resonances. This accelerator makes it possible to design a compact variable energy extraction machine which is particularly useful for research and medical applications such as heavy ion therapy.