Photonuclear Physics when a Multiterawatt Laser Pulse Interacts with Solid Targets

When a laser pulse of intensity ${10}^{19}\mathrm{W}{\mathrm{cm}}^{-2\mathrm{}}$ interacts with solid targets, electrons of energies of some tens of MeV are produced. In a tantalum target, the electrons generate an intense highly directional $\gamma$-ray beam that can be used to carry out photonuclear reactions. The isotopes ${}^{11}\mathrm{C}$, ${}^{38}\mathrm{K}$, ${}^{62,64}\mathrm{Cu}$, ${}^{63}\mathrm{Zn}$, ${}^{106}\mathrm{Ag}$, ${}^{140}\mathrm{Pr}$, and ${}^{180}\mathrm{Ta}$ have been produced by $(\gamma ,n)$ reactions using the VULCAN laser beam. In addition, laser-induced nuclear fission in ${}^{238}\mathrm{U}$ has been demonstrated, a process which was theoretically predicted at such laser intensities more than ten years ago. The ratio of the ${}^{11}\mathrm{C}$ and the ${}^{62}\mathrm{Cu}$ ${\beta }^{+}$ activities yields shot-by-shot temperatures of the suprathermal electrons at laser intensities of $\sim {10}^{19}\mathrm{W}{\mathrm{cm}}^{-2\mathrm{}}$.