Structure in the total 27Al(n, α) 24Na cross section around 14 MeV

Abstract

An excitation function for the 27Al(n, α) reaction has been measured in steps of about 15 keV throughout most of the energy range between 13.45 and 14.91 MeV in an effort to observe structure in the cross section. The insulated core transformer (ICT) neutron facility was used as the neutron source; a rotating, tritiated titanium target, capable of handling ion beams with currents up to 10 mA and with energies up to 450 keV, was employed. Using the activation method, a total of about 500 relative cross-section measurements were made at 87 different neutron energies. Fluctuations with magnitudes of about 1.5 % were observed in the cross section after all of the data had been correlated and corrected for the anisotropy and scattering effects that had been determined experimentally. A statistical treatment of the data yielded a compound nucleus level width of about 30 keV, which is reasonable for a 28Al nucleus excited to 20–22 MeV. The observed structure can be explained in terms of Ericson fluctuation theory.