MeV γ-ray yield from solid targets irradiated with fs-laser pulses

We have investigated the MeV bremsstrahlung which is emitted when fast electrons generated by the interaction of 200 mJ, 130 fs Ti:sapphire laser pulses with a preformed plasma penetrate into a solid target. Employing different targets the dependence of the γ-ray spectrum on the atomic number was studied. We detected single γ photons with an energy up to 2.5 MeV and found a maximum conversion efficiency of the laser energy into MeV bremsstrahlung of 4×10−6. Data analysis using a Monte Carlo code revealed a fast-electron temperature of 0.9 MeV.