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 kno wledge of the nuclear cross sections (excitation function and angular distribution) in an energy and angular range corresponding to the dept h to analyze. Several models have been developed since 30 years by nuc lear 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 angu lar domains was not the aim of the research. Using the nuclear models developed for these fundamental studies it is possible to obtain a com plete data base of cross sections, doing only a few measurements to no rmalize 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 th e energy range 0.300-3.5 MeV, and the angular range 110-180 degrees. T he data have been analyzed by the R matrix model. Most of the light el ement reaction cross sections will be measured and analyzed using eith er the R matrix model for compound nuclear reactions, or a nuclear tra nsfer model for stripping or pick up interactions, depending on the nu clear mechanism of production. Parallel to this, we are developing an analysis model based on the GEANT library developed at CERN. It consis ts of an events generator, using a Monte Carlo method, and a geometric al description of the experimental set up. It takes into account all t he nuclear reactions (particle and gamma-ray emissions) but not the X- ray emission.