Particle characterization for the evaluation of the 181mTa excitation yield in millijoule laser induced plasmas

The particles (ions, atoms, x-rays and high-energy electrons) resulting from the interaction of a high repetition rate laser with a tantalum target are characterized at laser intensities ranging between 3 × 1015 and 6 × 1016 W cm−2 using plasma and nuclear physics techniques. A simple model is developed to estimate, from these data, the 181Ta isomeric state excitation yields in the ablated matter and in the remaining target. Both nuclear photoexcitation and electron inelastic scattering processes have been taken into account in the calculations. A maximum of a few 10−3 excitations per laser shot are predicted in the investigated intensity range.