High power gamma flare generation in multi-petawatt laser interaction with tailored targets

Using quantum electrodynamics particle-in-cell simulations, we optimize the gamma flare (γ-flare) generation scheme from the interaction of a high power petawatt-class laser pulse with a tailored cryogenic hydrogen target having an extended preplasma corona. We show that it is possible to generate an energetic flare of photons with energies in the GeV range and the total flare energy being on a kilojoule level with efficient conversion of the laser pulse energy to γ-photons. We discuss how the target engineering and the laser pulse parameters influence the γ-flare generation efficiency. This type of experimental setup for a laser-based γ-source would be feasible for the upcoming high-power laser facilities. Applications of high intensity γ-ray beams are also discussed.