Acceleration and radiation of externally injected electrons in laser plasma wakefield driven by a Laguerre–Gaussian pulse**Project supported by the National Natural Science Foundation of China (Grant Nos. 11374209, 11374210, and 11774227) and the Major State Basic Research Development Program of China (Grant No. 2015CB859700).

Abstract

By using three-dimensional particle-in-cell simulations, externally injected electron beam acceleration and radiation in donut-like wake fields driven by a Laguerre–Gaussian pulse are investigated. Studies show that in the acceleration process the total charge and azimuthal momenta of electrons can be stably maintained at a distance of a few hundreds of micrometers. Electrons experience low-frequency spiral rotation and high-frequency betatron oscillation, which leads to a synchrotron-like radiation. The radiation spectrum is mainly determined by the betatron motion of electrons. The far field distribution of radiation intensity shows axial symmetry due to the uniform transverse injection and spiral rotation of electrons. Our studies suggest a new way to simultaneously generate hollow electron beam and radiation source from a compact laser plasma accelerator.