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We show that a ring-shaped hollow electron beam can be injected and accelerated by using a Laguerre-Gaussian laser pulse and ionization-induced injection in a laser wakefield accelerator. The acceleration and evolution of such a hollow, relativistic electron beam are investigated through three-dimensional particle-in-cell simulations. We find that both the ring size and the beam thickness oscillate during the acceleration. The beam azimuthal shape is angularly dependent and evolves during the acceleration. The beam ellipticity changes resulting from the electron angular momenta obtained from the drive laser pulse and the focusing forces from the wakefield. The dependence of beam ring radius on the laser-plasma parameters (e.g., laser intensity, focal size, and plasma density) is studied. Such a hollow electron beam may have potential applications for accelerating and collimating positively charged particles. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The article informs that developments in laser-wakefield accelerators have led to compact ultrashort X/gamma-ray sources that are comparable with conventional synchrotron sources. Topics include scheme to efficiently produce collimated ultrabright Gamma ray beams with photon energies tunable up to GeV with a multi-petawatt laser pulse into wakefield accelerator; and numerical simulations demonstrate that Gamma ray photons/shot are produced with energy conversion efficiency for photons.