EXCITATION CURVES FOR THE REACTIONS Al²⁷(<i>n</i>, α)Na²⁴ AND Mg²⁴(<i>n</i>, <i>p</i>)Na²⁴

Abstract

Excitation curves for the reactions Al 27 (n, α)Na 24 and Mg 24 (n, p)Na 24 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 S 32 (n, p)P 32 . Monoenergetic neutrons were obtained from the D(d, n)He 3 , T(d, n)He 4 , and the T(p, n)He 3 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)Na 24 reaction and 205 mb for the Mg 24 (n, p)Na 24 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.