Laser-driven ultrafast multi-MeV gamma-ray beam generation.

Ultrafast multi-MeV high-flux gamma-ray beams have been experimentally produced via bremsstrahlung radiation of laser-accelerated energetic electrons through millimeter-thick copper targets. By optimizing the electron bunches to the charge of 10 nC in a clustering argon gas target, the obtained gamma-ray beam significantly increases to 10$^{\mathrm{10}}$ photons per shot. The gamma-ray beam spectrum has been measured using a differential filtering detector and has a broad spectrum up to 15 MeV, which is approximately consistent with the Geant4 simulation. The generated high-flux high-energy gamma-ray beams are promising sources for photonuclear reaction, non-destructive inspection and clinical applications. \\ \\Tongjun Xu, Baifei Shen, Jiancai Xu, \textit{et al.}, \textit{Phys. Plasmas} 23, 033109 (2016). \item Shun Li, Baifei Shen, Jiancai Xu, \textit{et al.}, Ultrafast multi-MeV gamma-ray beam produced by laser-accelerated electrons (submitted).