The Resonant Acceleration Of Electrons With Multiple Laser Beams And Spontaneous Electromagnetic Fields In Plasma

The interaction of intense short laser pulse with plasmas is an open problem and has attracted much attention, for its many important applications such as laser-driven fusion, inertial confinement fusion fast ignition, intense field physics, hard x-ray emission, and new electron accelerator. All these applications are associated with the study of the electron acceleration in plasmas.First, using the single electron model, the acceleration of electrons in combined circularly polarized intense laser fields and the spontaneous quasistatic fields (including axial magnetic field Bsz azimuthal one Bθ, axial electric field Esz and the transverse one Esr) produced in intense laser plasma interaction is investigated analytically and numerically by fitting the proper parameters of the quasistatic fields based on the data from the experiment and numerical calculation. It is found that the bounce frequencyωβoscillating in the laser fields, the spontaneous quasistatic fields includes Bsz, Bsθ, Esr,Esz, and r (the distance from the axis) and vz(electron longitudinal velocity). A new resonant condition is given:the resonance acceleration of electron depends not only on laser field, but also on the bounce frequencyωβand the laser frequencyω. Asωβ/ωapproaches unity, resonance happens. The net energy gained by electron does not increase monotonously withEsz, but there are some optimal axial electric fields.Secondly, the acceleration mechanism of electrons with n coherent laser beams and strong spontaneous electromagnetic field Bsz Bsθand Esr fields is investigated. By fitting the parameters of Bsz, Bsθas well as Esr, the relativistic dynamical equations of single electron are solved numerically. It is found that the electron can be more effective accelerated by n beams of laser with the amplitude a0/n and special frequency difference(or one laser with amplitude a0 and nspecial frequency difference) than by single beam laser with the amplitude a0, because of the stochastic-like resonances between the frequencies or beat produced by the multiple coherent laser beams and electron cyclotron motion induced by the laser electromagnetic fields and the quasi-static spontaneous electric and magnetic fields.