Nuclear models and microanalysis

Most of the light elements like d, Li, B, C, N, O, F can be identified and quantified using nuclear reactions induced by protons, deuterons, He-3 or He-4. Profiles or layers thickness measurements depend on knowledge of the nuclear cross sections (excitation function and angular distribution) in an energy and angular range corresponding to the depth to analyze. Several models have been developed since 30 years by nuclear physicists, to describe the nucleus. The interest was mainly the knowledge of spectroscopic data like energy levels, spin, parity, life time, etc. The knowledge of the cross section in large energy or angular domains was not the aim of the research. Using the nuclear models developed for these fundamental studies it is possible to obtain a complete data base of cross sections, doing only a few measurements to normalize the models in the domain of interest for nuclear analysis. We have performed such measurements for the C-12(p, p)C-12 reaction in the energy range 0.300-3.5 MeV, and the angular range 110-180 degrees. The data have been analyzed by the R matrix model. Most of the light element reaction cross sections will be measured and analyzed using either the R matrix model for compound nuclear reactions, or a nuclear transfer model for stripping or pick up interactions, depending on the nuclear mechanism of production. Parallel to this, we are developing an analysis model based on the GEANT library developed at CERN. It consists of an events generator, using a Monte Carlo method, and a geometrical description of the experimental set up. It takes into account all the nuclear reactions (particle and gamma-ray emissions) but not the X-ray emission.