ELECTRON ACCELERATION IN VACUUM: EFFECT OF LASER POLARIZATION IN ADDITION TO THE WIGGLER MAGNETIC FIELD

Abstract

Irrespective of the chirped pulse inverse free electron laser (CPIFEL) concept, a comparative study of a chirped circular-polarized (CP) laser pulse and a chirped linear-polarized (LP) laser pulse has been done numerically via electron acceleration in vacuum. We found that ultrahigh acceleration of the electron could be achieved by each chirped laser CP and LP pulse. Due to some unique property of the CP laser pulse, like a large acceleration phase channel and axial symmetry of the electromagnetic fields (EM), the acceleration gradient is expected to be higher in a chirped CP laser pulse than in a chirped LP laser pulse. A combination of periodically tapered wiggler magnetic field helps in stabilizing the transverse motion of the electron and projects one component of the laser's electric field in the direction of the electron motion, resulting in a higher energy gain. Laser parameters, like the amplitude, the initial phase of the laser and the laser frequency chirped parameter in addition to the tapered wiggler magnetic field parameters, all have strong influence on the electron energy gain. It is higher for the combination of a chirped CP laser with a circular wiggler magnetic field than for a chirped LP laser and a planar wiggler magnetic field. We show that energy gradients of several giga-electron-volts (GeV) per meter may be obtained when the parameters are adjusted in such a way to meet the IFEL resonance condition.