Numerical study of pair creation by ultraintense lasers

Now that intensity of lasers has reached 1020 W/cm2, electron–positron pairs can be created by the irradiation of such ultraintense lasers on a thin gold foil. The energy of electrons produced by ultraintense lasers reaches more than several tens of MeV. Such high energy electrons become a source for creating electron–positron pairs via interaction with nuclei. There are a few processes that create electron–positron pairs in this situation. Two processes, call the trident process and the Bethe–Heitler process, are considered in this study. A numerical simulation code based on a relativistic Fokker–Planck equation is developed for studying the hot electron transport. The equation is solved by assuming one-dimensional real space and two-dimensional momentum space with axial symmetry. It is found that the total positron yield increases logarithmically with the increase of the laser intensity, and the resultant energy distribution of the created positron is found to have a peak near the energy of 1–2 MeV.