Fast electron transport as well as bremsstrahlung emissions induced by relativistic intense laser solid interactions are investigated with a newly developed particle-in-cell (PIC) simulation code. This PIC code is capable of simulating intense laser-solid interactions by taking into account many coupled physical processes, like laser-plasma interaction, ionization dynamics, collisional dynamics, electron transport and photon emission. The target effects can be distinguished according to their intrinsic atomic properties. In this work, aluminium, copper, and gold targets with different thickness are considered. It is shown that with the fixed laser intensity of 1020 W cm−2, the angular distribution of bremsstrahlung emission, significantly depends on target material and target thickness. For low Z material, the electrons and the emitted photons tend to be collimated along the laser propagation direction. For high Z material, the angular distribution is broader, which is attributed to the self-generated resistive magnetic field-induced electron momentum divergence. Moreover, the simulation result shows that for Al target, the total emission energy increases with decreasing target thickness, because electron refluxing induces considerable backward emission. Comparatively, for Au target, the electron refluxing effect on the total emission energy can be ignored, because the backward emission is somewhat buried within the broad distribution.
Hot electron retention in laser plasma created under terawatt subnanosecond irradiation of Cu targets
Transport of intense laser-produced electron beams in matter