Laser Induced Nuclear Physics

This thesis describes the first systematic study of laser induced nuclear physics. When the VULCAN ultra-intense laser pulse interacts with a solid target, electron and proton beams of energies up to 40 MeV are generated. These particles were used to induce nuclear reactions in materials. The electron beams, being inefficient in inducing nuclear reactions were converted to energetic gamma-rays via bremsstrahlung in a tantalum converter. These gamma-rays were then used to induce photo-nuclear reactions in different materials via (gamma,mn) reactions. Evidence of reactions occurring was obtained by measuring the radiation emitted by the product nuclei. The gamma-rays produced in the laser-solid interaction were used to fission a sample of 238U the first observation of laser induced fission. Photo-nuclear reactions were used to measure the number and angular distribution of photons above 10 MeV produced in the interaction and to measure the temperature of the fast electrons generated. Protons can directly interact with nuclei to take part in nuclear reactions. In particular (p,n) and (p,alpha) reactions were used to produce positron emitting nuclei, specifically and 11C which are 13N used in Positron Emission Tomography, a form of medical imaging. Nuclear reactions were also used to measure the spectrum of the proton beams produced in the laser-solid interaction. Preliminary measurements of proton production on a much smaller laser system, ASTRA were performed as a possible extension of the above techniques to table-top laser systems