  This study uses neural networks to improve Monte Carlo (MC) implementations
of the Bethe-Heitler process in Particle-In-Cell (PIC) codes. We provide a
neural network that is as accurate as pre-calculated tables, and requires a
hundred times less memory to store. It is trained to predict Bethe-Heitler pair
production cross-sections for atomic numbers 1-50 and photon energies between 1
MeV and 10 GeV in the PIC code OSIRIS. We first validate our approach against a
theoretical estimate in a simplified context. We later prove that both
approaches have similar performance in a typical relativistic laser-plasma
interaction scenario. The large memory decrease accessible with neural networks
will enable introducing more advanced cross-section models for Bethe-Heitler
pair production and other QED mechanisms in the MC modules of PIC codes.
