Electron acceleration by a chirped circularly polarized laser pulse in vacuum in the presence of a planar magnetic wiggler

Ultrahigh-gradient acceleration, by a chirped circularly polarized (CP) laser pulse in the presence of a planar magnetic wiggler, is investigated numerically. A simple linear chirped profile of laser frequency has been introduced in our model. The combined effect of frequency chirping and the tapered wiggler magnetic field on the electron acceleration is discussed in detail. It is found that the chirping parameter, the wiggler field tapering parameter, the initial phase of the laser, the laser spot size and laser intensity all have a strong influence on the electron acceleration. If an optimal tapered wiggler magnetic field in the same direction as the magnetic field of the laser pulse is externally applied during the trailing part of the pulse, the electron can gain and retain significant energy in the form of cyclotron oscillations even after the passing of the laser pulse.