Relativistic electron generation in interactions of a 30 TW laser pulse with a thin foil target

Energy and angular distributions of the fast outgoing electron beam induced by the interaction of a 1 J, 30 fs, $2\times {10}^{19}{\mathrm{W}/\mathrm{c}\mathrm{m}}^2,$ 10 Hz laser with a thin foil target are characterized by electron energy spectroscopy and photonuclear reactions. We have investigated the effect of the target thickness and the intensity contrast ratio level on the electron production. Using a $6-\mu \mathrm{m}$ polyethylene target, up to $4\times {10}^8$ electrons with energies between 5 and 60 MeV were produced per laser pulse and converted to $\gamma$ rays by bremsstrahlung in a Ta secondary target. The rates of photofission of U as well as photonuclear reactions in Cu, Au, and C samples have been measured. In optimal focusing conditions, about 0.06% of the laser energy has been converted to outgoing electrons with energies above 5 MeV. Such electrons leave the target in the laser direction with an opening angle of $2.5°.$