Proton Boron Fusion Reaction: A Novel Experimental Strategy for Cross Section Investigation

The fusion reaction 11B(p,alpha)alpha alpha draws attention since the dawn of nuclear physics for its relevance and potential application in different fields, from nuclear fusion to astrophysics and hadron therapy. Nevertheless, the understanding and description of the physics of the reaction still have some important open points, both theoretical and experimental. Among others, the energy and angular distributions of alpha particles produced by the different reaction channels need to be further characterized, especially at low energies. To this aim, a novel experimental set-up was conceived by combining well-characterized boron-coated targets and a two-stage monolithic detection system. Targets were produced by Pulsed Laser Deposition, a technique that allows to finely tailor thickness, density and chemical composition of coatings. The detection system, based on a Delta E-E silicon telescope, was developed to perform an effective identification and discrimination between alpha particles produced by the p-11B reaction and primary protons, essential for the reaction kinematic analysis at low energies. Irradiations were performed by bom-barding a boron-coated foil with primary protons of energies in the range 1-2.4 MeV. Results show the effectiveness of the particle discrimination. Measured energy distributions highlight the contribution of alpha particles generated in the two main reaction channels. A preliminary quantitative analysis of the reaction cross section was performed for each reaction channel at the different investigated energy and compared with literature data. The experimental set-up was also simulated through the Monte Carlo code FLUKA to test the model capabilities recently implemented in the code.