GeV-level γ-ray and positron beams produced by collisions of multi-PW laser on high-energy electron beam

Abstract: Based on collisions between the 100 PW laser and 8 GeV superconducting linear accelerator constructing in Shanghai High Repetition Rate X-ray Free Electron Laser and Extreme Light Facility, the building of GeV-level γ-ray as well as positron beams are proposed according to particle-in-cell simulations. Key processes are considered involving the nonlinear inverse Compton scattering for γ-ray generation and the multiphoton Breit-Wheeler process for electron-positron pair production. Regardless of laser polarization, the simulations indicate that γ-ray beams achieve energy up to 8 GeV, brilliance around 10²⁷ photons/(s·mm²·mrad²), and emittance as low as 0.1 mm·mrad, while positron beams attain energy up to 7 GeV, brilliance around 4 × 10²⁴ positrons/(s·mm²·mrad²), and emittance as low as 0.1 mm·mrad. Various applications could benefit from the possible high-energy γ-ray and positron beams, which may potentially be built in SHINE, including fundamental physics of strong-field quantum electrodynamics theory validation, nuclear physics, nuclear astrophysics, imaging and so on.