Photonuclear Fission from High Energy Electrons from Ultraintense Laser-Solid Interactions

A new regime of laser-matter interactions in which the quiver motion of plasma electrons is fully relativistic, with energies extending well above the threshold for nuclear processes, is studied using a petawatt laser system. In solid target experiments with focused intensities exceeding ${10}^{20}\mathrm{W}/{\mathrm{cm}}^2$, high energy electron generation, hard bremsstrahlung, and nuclear phenomena have been observed. We report here a quantitative comparison of the high energy electrons and the bremsstrahlung spectrum, as measured by photonuclear reaction yields, including the photoinduced fission of ${}^{238}\mathrm{U}$.