Double differential cross-sections of (n, α) reactions in aluminium and nickel at 14.77 MeV neutrons

The double differential cross-sections (DDX) for the emission of alpha particles from Al-27(n, alpha)Na-24 and Ni(n, alpha) reactions induced by 14.77 MeV neutrons were estimated from the alpha particle spectra recorded at 30 degrees, 50 degrees, 90 degrees, 110 degrees angles for aluminium, and at 20 degrees, 45 degrees, 90 degrees, 110 degrees for natural nickel. The results indicate that the alpha particles below and around the most probable energies (similar to 6.3 MeV from aluminium and similar to 8 MeV from natural nickel) are emitted predominantly through the compound nucleus formation process, and the higher energy alpha particles are emitted through the pre-equilibrium or the direct reaction. In general, the measured double-differential cross-sections are in agreement with the theoretical cross-sections estimated using Talys-1.0 and Preco2007 computer programs. The present value of the level density parameter for Na-24 is close to the literature value and, therefore, these results reveal consistency in the alpha particle spectra recorded with a single silicon surface barrier detector at different scattering angles. (C) 2009 Elsevier B.V. All rights reserved.