The ¹⁰B(n,α₀)⁷Li and ¹⁰B(n,α_lγ)⁷Li alpha-particle angular distributions, branching ratios and cross-sections measurements for E_n < 3 MeV

The ¹⁰B(n,α₀)⁷Li and ¹⁰B(n,α_iγ)⁷Li angular distributions have been measured at the GELINA time-of-flight spectrometer in the incident neutron energy range from 0.1 keV to 1 MeV by means of a twin Frisch-grid ionization chamber. With this type of detector it is possible to measure the angular distribution of the charged reaction fragments in a close to 2×2π solid angle with ~100% efficiency and a clear separation of both reaction channels: emission to the ⁷Li ground state (α₀) or to its first excited state (α₁). A strong angular anisotropy was observed at ~ 520 keV. In order to extend the energy range up to 2.5−3 MeV and to measure, also, the reaction cross sections, a double twin Frisch-grid ionization chamber was constructed. It is loaded with two very thin 94% ¹⁰B-enriched samples, mounted back-to-back with ²³⁵U samples on the common cathodes. New data acquisition, visualization and analysis software is used in a new set of long-term measurements, which are still going on.