Backlight imaging by X-ray irradiation from high-intensity femtosecond-laser driven gas targets

Two experiments of laser-driven methane jet are performed on a petawatt laser, and the X-ray emitted is used to backlight small-size metal objects with SCCD(scintillator screen + CCD camera). Converters with different thicknesses are chosen considering the temperature of hot electrons which is evaluated both by the empirical formula and by the particle-in-cell (PIC) code. The X-ray energies of 377 keV and 130 keV are estimated by the two methods respectively. Consequently, converters with 1.3 mm and 0.8 mm thicknesses are chosen. Photon energies of 49 keV and 92 keV are obtained by grayscale curves of aluminum and copper step-wedges in the second experiment. It is demonstrated that the photon energy deduced from the PIC code agrees with the experimental result.