Modelling gamma-ray photon emission and pair production in high-intensity laser–matter interactions

In high-intensity ( > 10 21 W cm − 2 ) laser–matter interactions gamma-ray photon emission by the electrons can strongly affect the electronʼs dynamics and copious numbers of electron–positron pairs can be produced by the emitted photons. We show how these processes can be included in simulations by coupling a Monte Carlo algorithm describing the emission to a particle-in-cell code. The Monte Carlo algorithm includes quantum corrections to the photon emission, which we show must be included if the pair production rate is to be correctly determined. The accuracy, convergence and energy conservation properties of the Monte Carlo algorithm are analysed in simple test problems.