Studies on gamma ray emission from interaction between solid targets and femtosecond lasers

The generation of gamma ray emission from interaction between femtosecond lasers and solid targets has been investigated experimentally. Apparent effects of a prepulse on gamma ray emission are observed using 150 fs laser pulses at an irradiance of I lambda(2) similar to 5x10(15) Wcm(-2)mu m(-2) focused on solid targets. The fraction of high energy photons (>100 keV) are found to be greatly enhanced by introducing a 8% prepulse at 70 picosecond before the main pulse. Measurements show that a hot electron temperature as high as 83 keV has been produced at such a modest irradiance.