Enhancing Bremsstrahlung Radiation using Front Surface Target Structures

X-ray or $\gamma $-ray sources generated by laser solid interactions have many potential applications in different fields including X-ray radiography, pair production and photonuclear physics. Recent studies with 3D PIC modeling have shown that large scale front-surface target structures can significantly increase the energy and narrow the angular distribution of hot electrons compared to that for a regular flat target.\footnote{S. Jiang, A. G. Krygier, et al., Phys. Rev. E 89, 013106 (2014)} These characteristics of electrons are crucial for further Bremsstrahlung production using a high-Z converter target. The corresponding Bremsstrahlung radiation covers a wide energy range and can be as high as 100 MeV. By performing the Monte-Carlo simulations we find that the peak $\gamma $-ray brightness is 6.0*10$^{19}$ s$^{-1}$mm$^{-2}$mrad$^{-2}$ at 10MeV and 1.4*10$^{19}$ s$^{-1}$mm$^{-2}$mrad$^{-2}$ at 100MeV (0.1{\%} bandwidth), which is comparable to other tunable $\gamma $-ray sources. The brightness for high energy $\gamma $-rays (\textgreater 50MeV) is one or a few orders of magnitude higher using the structured target than the flat target. Simulation and preliminary experimental results will be presented.