Gamma-ray generation and pair production from extreme laser-driven magnetic fields*

The ability of an intense laser pulse to propagate in a classically over-critical plasma through the phenomenon of relativistic transparency is shown to facilitate the generation of strong plasma magnetic fields. Particle-in-cell simulations demonstrate that these fields significantly enhance the radiation rates of the laser-irradiated electrons, and furthermore they collimate the emission so that a directed and dense beam of multi-MeV gamma-rays is achievable[1]. This capability can be exploited for electron-positron pair production via the linear Breit-Wheeler process by colliding two such dense beams. Presented simulations using a novel simulation code show that more than 10³ pairs can be produced in such a setup, and the directionality of the positrons can be controlled by the angle of incidence between the beams. 

[1] O. Jansen et al.; Plasm. Phys. and Contr. Fus., 60, 5, 054006 (2018)