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Photo-excitation nuclear reactions induced by the 2J, 30 fs, 4x1010W/cm2, 10 Hz LOA laser were optimized with respect to the thickness of the solid target. Using 6 micrometers CH targets, electrons up to 60 MeV have been produced and converted to (gamma) -rays by Bremsstrahlung in a Ta piece. The rate of photo-fission of 238U, as well as photo- excitation nuclear reactions in Cu, Au and C samples have been measured. More than 106 nuclear reactions were obtained after 60 subsequent laser shots. The high energy electrons are forward focused, within 15 degree(s), as observed from the angular distribution of the activation in Cu. 1% of laser energy was converted to (gamma) -rays with energies higher than 10 MeV.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A search of Nuclear Excitation by Electron Transition (NEET) in 235 U excited in the plasma produced by a 300 mJ, 10 ns laser is presented. Many experimental aspects have been faced to evidence the low rate of NEET excitation of the 76 eV isomeric level in 235 U with a plasma temperature T=25 eV. The experimental limit measured for the transition rate for the 76 eV 235 U m state is N < 2. 10 -5 s -1 . Several potential upgrades are considered to aim at a measure of the NEET excitation rate in 235 U. 1. INTRODUCTION The Nuclear Excitation by Electron Transition (NEET) process is the excitation of the nucleus with simultaneous deexcitation of the atomic system in the same atom [1]. This process is just the reverse of the BIC (for Bound Internal Conversion) in which the deexcitation energy of the nucleus is transferred, via a virtual photon, to the excitation of an atomic electron from one bound state to another bound state. The BIC has been recently studied experimentally and theoretically in