Vacuum laser acceleration in circularly polarized fields

This paper presents the characteristics of vacuum laser acceleration in circularly polarized (CP) fields with the capture and acceleration scenario (CAS) scheme. Compared with linearly polarized laser fields, the main advantage for using a CP field is that its acceleration channel occupies a relatively larger phase space, stemming from the distribution of the longitudinal electric component, the dependence on the laser initial phase and on the incident polarization azimuth angle, etc. These features can give rise to greater acceleration efficiency. One of the disadvantages is the 'energy saturation' phenomenon if the laser intensity is sufficiently high, which comes from the additional Lorentz force component in the CP field. The output properties of the accelerated CAS electron bunch, such as the energy spectra, the angular distributions, the energy-angle correlations, the acceleration efficiency, the rms emittance and the energy divergence, are also examined. Physical explanations concerning these characteristics are presented.