GYRAC: a compact, cyclic electron accelerator

The concept of the gyro-resonant accelerator (GYRAC), which is based on cyclotron resonance in a magnetic field that is increasing slowly in time, is presented. Previously published work shows that this results in an autoresonance in which the wave provides a synchronous acceleration of the electrons. Using a simple model makes it possible to design a particularly compact, cyclic electron accelerator; in a cavity with a 1-m radius and final magnetic field of 5 T, electron energy reaches 680 MeV, giving rise to synchrotron radiation of 1 keV. Assuming uniform fields and rescaling time, a Hamiltonian system is arrived at which has one degree of freedom and which, in first-order approximation is time independent. In a second-order approximation, a slow damping of the autoresonant oscillation is found. A paraxial model for beam and fields allows evaluation of the charge effects-the GYRAC then resembles the betatron. These results are illustrated by numerical three-dimensional simulations