Apparatuses and methods for accelerating electrons include an electron source configured to provide a beam of electrons and an accelerator that utilizes electron cyclotron resonance acceleration (eCRA). The accelerator includes a radio frequency (RF) cavity having a longitudinal axis, one or more inlets, and one or more outlets and a first electro-magnet substantially surrounding at least a portion of the cavity and configured to produce an axial magnetic field. The RF cavity is coupled to an RF source and configured to accelerate the beam of electrons axially entering the RF cavity with non-linear cyclotron resonance acceleration. A second electro-magnet located downstream of the one or more outlets of the RF cavity is configured to generate an inverse cusp in the axial magnetic field to manipulate the beam of electrons leaving the RF cavity from a helical orbit to a substantially linear path.