Maximizing MeV photon dose of a short-pulse, laser-driven source via large-scale simulations of solid target laser-plasma interactions

There is interest in using intense, short-pulse lasers to produce bright high-energy sources for the probing of hot, dense material in high-energy density science. We are particularly interested in producing large quantities of hot electrons through laser-solid interactions, which can then provide high-energy X-rays through Bremsstrahlung radiation. At facilities of interest, laser amplitude and duration can be varied with the desire to produce an optimal quantity of MeV X-rays. We present a set of large-scale (100s of μm wide) and long-duration (10s of ps) particle-in-cell simulations with varied laser parameters that maintain constant pulse energy. Characteristics of the hot-electron population are examined, showing clear trends in electron temperature as a function of the normalized vector potential a₀. The electron spectrum is also used to calculate the X-ray Bremsstrahlung radiation spectrum for various target thicknesses. The results provide guidance as to the optimal laser intensity and duration for the greatest number of 1–5 MeV X-rays.