Gamma-Rays Generated from Plasmas in the Interaction of Solid Targets with Femtosecond Laser Pulses

The γ-rays with energies up to 300keV have been observed from plasmas produced by femtosecond laser pulses at a focused intensity of 5 x 10¹⁵ W.cm^-2.μm² irradiating Ta, Mo, and Cu targets. By introducing an 8% prepulse of 70ps before the main pulse, the fraction of high energy γ-ray photons (hv >l00keV) was significantly enhanced relative to low energy photons (hv < 100 keV).