Hollow high-quality electron beam generation by cyclotron autoresonance in laser-induced acceleration

In this study, the dynamics of electrons by a focused Gaussian laser pulse in the presence of an ultrashort axial magnetic field have been investigated numerically. The cyclotron resonance of the electrons due to the external magnetic field were theoretically investigated. An optimized magnetic field can enhance the electron energy gradient with ultra-low scattering. The simulation provides a circulating hollow electron beam suitable for high-precision and high-energy particle physics experiments. The features of output electron beam such as mean energy gain, energy spectra, spatial emittance and angular scattering distribution were examined and their concerning physical explanations have been presented. It has been found that an electron bunch with about MeV initial energy becomes a compressed electron beam with about 3 GeV energy, after interacting with the laser pulse applied by a nanosecond pulsed magnetic field.