An 26Al target for (n,p) and (n,α) cross-section measurements

The radionuclide 26Al plays an important role in astrophysics. It can be detected via the 1.8 MeV γ-ray it emits, providing information on stellar nucleosynthesis processes using maps of the universe made by γ-ray telescopes. In addition, the decay of 26Al to 26Mg in meteorites producing anomalous 26/24Mg ratios gives clues to the origin of the solar system. New studies of the 26Al(n,p)26Mg and 26Al(n,α)23Na destruction mechanisms required an 26Al target containing significantly more 26Al than that previously used. This target was prepared by molecular plating from isopropanol onto a nickel foil substrate with a yield close to 100%. The total number of 26Al atoms, determined by γ-spectrometry, was (2.6±0.2)×1017, corresponding to 11.2±1.0 μg (expanded uncertainty, coverage factor k=2). The areal density was 0.37 μg/cm2. Measurements of (n,p) and (n,α) cross-sections in a thermal neutron beam exhibited sufficient resolution of the p- and α-peaks to allow detection of a number of new transitions.