Investigation of the ¹⁰B(p,α)⁷Be reaction from 0.8 to 2.0 MeV

Background: A multitude of broad interfering resonances characterize the ¹⁰B(p,α)⁷Be cross section at low energies. The complexity of the reaction mechanism, as well as conflicting experimental measurements, have so far prevented a reliable prediction of the cross section over the energy ranges pertinent for a boron-proton fusion reactor environment.

Purpose: To improve the evaluated cross section of the ¹⁰B(p,α)⁷Be reaction, this study targets the proton energy region from 0.8 to 2.0 MeV, where kinematic overlap of the scattered protons and reaction α particles have made past measurements very challenging.

Method: New detailed studies of the reaction have been performed at the Edwards Accelerator Laboratory at Ohio University and the Nuclear Science Laboratory at the University of Notre Dame using time-of-flight and degrader foil techniques, respectively.

Results: Proton and α-particle signals were clearly resolved using both techniques, and 16 point differential cross sections were measured over an angular range of θlab=45° and 157.5°. A comprehensive R-matrix analysis of the experimental data, including data from previous low-energy studies of the ¹⁰B(p,α)⁷Be, ¹⁰B(p,p)¹⁰B, and ¹⁰B(p,γ)¹¹C reactions, was achieved over the region of measurement. Using a representative set of previous data, the fit was extended to very low energies.

Conclusions: On the basis of this data and R-matrix analysis, a more reliable and consistent description of the ¹⁰B(p,α)⁷Be cross section has been established. The uncertainty over the energy range of this study has been reduced from ≈20% to ≈10%, and the level structure over this region has been clarified considerably.