Review on Benchmarking of Proton Elastic Scattering - Implementation in the cases of natSi, 19F, natB and natO

(1) Department of Physics, School of Applied Science and Mathematics, National Technical University of Athens, Zografou Campus, 15780 Athens, Greece
(2) Tandem Accelerator Laboratory, INPP, NCSR 'Demokritos', Aghia Paraskevi 15310, Athens, Greece

The implementation of all Ion Beam Analysis (IBA) depth profiling techniques critically depends on the accuracy of the available differential cross sections for the reactions involved. Unfortunately, the existing experimentally determined differential cross-section data are in many cases quite scarce and/or discrepant, thus their reliability is highly questionable. On the other hand, the evaluated cross-sections, when available, are the most reliable ones to be used in analytical studies, since they involve a critical assessment of the experimental datasets, followed by a proper tuning of the corresponding nuclear model parameters. However, it is important to point out that most of the evaluated datasets are still not adequately validated. A carefully designed benchmarking experimental procedure (i.e. the validation of differential cross-section data via the acquisition of thick-target spectra followed by their simulation) is thus mandatory. Benchmarking can also provide the necessary feedback for the adjustment of the parameters of the nuclear model used in the evaluation process, and can help in assigning realistic uncertainties to the cross sections. Moreover, in the absence of evaluated cross sections, it can indicate recommended experimental datasets.

Recently, a dedicated effort was made to thoroughly document this procedure [1], followed by a technical meeting organized by IAEA. In the present review an attempt is made to present the recommended steps and to critically assess the problems of the benchmarking process in the following cases: (1) In natSi(p,p0), for Ep=1.5-3.5 MeV, where channeling perturbations in crystalline wafers, if not carefully treated, can seriously affect the accuracy of the measurements, while the size of the powder used in pressurized tablets can affect the shape of resonances in the experimental thick-target yield spectra, (2) in 19F(p,p0) and natB(p,p0), for Ep=1.5-2.5 MeV, where, for the removal of the important underlying α-particle background, DE/E telescopes have been implemented, and (3) in natO(p,p0), for Ep=1.5-4 MeV, where target related effects (e.g. roughness) need to be taken into account.

[1]  V. Paneta, J. L. Colaux, A. F. Gurbich, C. Jeynes, M. Kokkoris, Nucl. Instr. and Meth. B328 (2014), p. 1-7.