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

摘要

The radionuclide Al-26 plays an important role in astrophysics. It can be detected via the 1.8 MeV gamma-ray it emits, providing information on stellar nucleosynthesis processes using maps of the universe made by x-ray telescopes. In addition, the decay of Al-26 to Mg-26 in meteorites producing anomalous Mg-26/24 ratios gives clues to the origin of the solar system. New studies of the Al-26(n,p)Mg-26 and Al-26(n,alpha)Na-23 destruction mechanisms required an Al-26 target containing significantly more Al-26 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 Al-26 atoms, determined by gamma-spectrometry, was (2.6 +/- 0.2) x 10(17), corresponding to 11.2 +/- 1.0 mug (expanded uncertainty, coverage factor k = 2). The areal density was 0.37 mug/cm(2). Measurements of (n,p) and (n,alpha) cross-sections in a thermal neutron beam exhibited sufficient resolution of the p- and alpha-peaks to allow detection of a number of new transitions. (C) 2001 Elsevier Science B.V. All rights reserved. References: 14