Optimization of e+/e− pair yield during the interaction of a Doppler-boosted laser with a solid-density plasma

The interaction of a Doppler-boosted laser with a solid-density plasma is investigated with two-dimensional particle-in-cell simulations, with special attention paid to the influences of laser incident angle on the yield of e+/e− pairs. With normal laser incidence, it is found that parts of plasma electrons are accelerated by the reflected laser and radiate high-energy γ-photons, which further make nearly head-on collisions with the subsequent incoming laser pulses. The nonlinear quantum parameters of the produced photons can reach 4.6, and the yield of e+/e− pairs increases by a factor of 4 compared to an incident angle of 45°. The optimization is easy to implement and can improve the signal-to-noise ratio in the experiments.