A SOFTWARE FOR FITTING LEIS DATA

During the last three years the use of the LEIS technique at ISTP to understand W enrichment on Eurofer samples exposed to a deuterium plasma in GyM was quite extensive. As a matter of fact Eurofer has different elements, besides W, that can migrate toward the surface by thermal diffusion so that the interpretation of LEIS experimental peaks it's really difficult. A typical case stems from V, Fe and Cr. Their respective average mass numbers are very close and their peaks can overlap each other. As a consequence the experimental data can present unresolved components under the same peak. A possible solution to circumvent the problem is to increase the energy of the primary beam or to choose a heavier projectile. The second solution does not offer many opportunities, because it practically means to change from Ne to Ar or Xe since the alkaly metals as primary beam are more expensive. Increasing the energy of the primary beam is advisable to some extent. In fact, increasing the beam energy the position of species with similar mass number could be better resolved at price of sensitivity. The scattering cross section decreases with energy and this negative effect depend also on the specific projectile-target pair. A better approach consists on fitting the experimental data taking into account all the isotopes for every specific element instead of considering a single component with average mass number. This report presents the development of a software based on a scattering model that takes into account all the isotopic species of one element or more (up to four).