EXCITATION CURVES FOR THE REACTIONS Al27(n, α)Na24 AND Mg24(n, p)Na24

Abstract

Excitation curves for the reactions Al²⁷(n, α)Na²⁴ and Mg²⁴(n, p)Na²⁴ have been measured by the activation method from near threshold energies to 20.3 Mev. The measurements are relative to the known cross section for the reaction S³²(n, p)P³². Monoenergetic neutrons were obtained from the D(d, n)He³, T(d, n)He⁴, and the T(p, n)He³ reactions employing a Tandem Van de Graaff accelerator or 125-kev accelerator. Cross sections for both reactions rise above the minimum detectable value of 0.02 mb near 5 Mev and reach maximum values of 126 mb for the Al(n, α)Na²⁴ reaction and 205 mb for the Mg²⁴(n, p)Na²⁴ reaction at 13.5 Mev. Above this energy both cross sections decrease. From the excitation curves effective cross-section values for a fission-neutron spectrum have been calculated as 0.61 ± 0.03 mb for the (n, α) reaction and 1.34 ± 0.07 mb for the (n, p) reaction.