Creation and diagnostics of high-flux gamma-rays > 8 MeV and photo-neutrons using a petawatt laser to irradiate high-Z solid targets*

We report the creation of super-high-fluxes of gamma-rays with energy >8 MeV and photo-neutrons via the (gamma,n) reaction near giant dipole resonance energies (8 - 20 MeV), using the ~130 J Texas Petawatt laser to irradiate high-Z (Au, Pt, Re, W) targets of mm - cm thickness, at laser intensities up to 5x10²¹W/cm².  We detected up to ~ several x 10¹² gamma-rays > 8 MeV (~3% of incident laser energy) and ~ 10¹⁰ photo-neutrons per shot.  Due to the short pulse and narrow gamma-ray cone (~17^o  half-width) around laser forward, the peak emergent gamma-ray flux >8 MeV reached ~10²⁷ gammas/cm²/sec, and the peak emergent neutron flux reached ~10²⁰ neutrons/cm²/sec. Such intense gamma-ray and photo-neutron fluxes  will facilitate the study of nuclear reactions and applications requiring super-high-flux of gamma-rays or neutrons,