The stellatron accelerator

The magnetic field configurations consisting of the combination of a weak-focusing betatron field, toroidal field and either l=0 or l=2 stellarator windings, are assessed for their potential as focusing fields for high-current cyclic electron accelerators. These accelerators, named ''stellatrons'', are shown to have improved tolerance to mismatch between the average beam energy and the equilibrium beam energy that matches the vertical magnetic field compared to devices without the stellarator fields. Both analytical calculations in the paraxial approximation and numerical particle-orbit calculations are presented to substantiate this finding. The problems of orbital resonances and of injection into these devices are discussed. Earlier work in the field is discussed and compared with the stellatron concept. (author)