Particle energization by high-power laser pulse in a finite-size electron–positron–ion plasma

Abstract

In this paper, nonlinear laser energy absorption in a finite-size electron–positron–ion plasma is studied in detail, using a two-dimensional relativistic electromagnetic PIC simulation code. It turns out that the laser energy absorption rate in the electron–positron–ion plasma drastically depends on the positron to electron density ratio (). This can be attributed to the effects of this parameter on nonlinear phenomena related to laser absorption such as phase mixing and laser scattering. The results illustrate that phase-mixing time is reduced by increasing the defined density ratio, resulting in the enhancement of the laser energy absorption rate. As a significant result, it can be found that in a finite-size electron–positron–ion plasma the absorption rate increases with increasing as long as laser scattering from the plasma is not considerable. It is shown that for long enough times the absorption rate decreases by increasing due to stimulated instabilities. The simulation results presented on the phase mixing of nonlinear oscillations as well as on particle energization in electron–positron–ion plasmas are expected to have relevance to laboratory and astrophysical environments.