Relativistic electron heating in focused multimode laser fields with stochastic phase perturbations

Abstract

We describe a direct model for simulation of relativistic electrons acceleration with a given electromagnetic field which is determined by wave packet parameters. The multimode time-spatial structure of a focused Nd-laser beam with stochastic phase disturbances of each spectral component is taken into account as a source of random forces. Electron energies of more than 10 MeV are obtained even at moderate flux densities of 10 16 W/cm 2 . The developed numerical code makes it possible to obtain a quantitative energy distribution function in relation to both field intensity and the temporal bellshape of the laser pulse. The efficient heating of electrons can be triggered in the presence of a counter propagating wave being reflected from the critical plasma area with a different reflection coefficient. The heating mechanism occurs with a delay relative to the beginning of the pulse when the laser fields exceed some threshold amplitudes. The qualitative comparison of simulation results with the experimental data is given as evidence that this mechanism is reasonable.

Stochastic electron heating in an interference field of several laser pulses of a picosecond duration

“…Discussed above observations can be compared with the results reported in [8,10,20] where the presence reflected wave triggered the process of stochastic electron heating. Electron energy enhancement in vacuum by a laser pulse reflection plays important role in laser energy absorption that was demonstrated in [37,38].…”

“…More efficient electron acceleration may occur in the interference pattern of several electromagnetic waves, where the electron acceleration becomes a stochastic process [17][18][19]. Generation of relativistic electrons in interaction of a subrelativistic laser pulse with a solid target was reported in [20]. It was explained by a multimode spatio-temporal structure of a focused laser beam with stochastic phase disturbances of each spectral component.…”