Th232 (n,2n)Th231 CROSS SECTION FROM THRESHOLD TO 20.4 MEV

Abstract

The excitation curve for the reaction Th²³² (n,2n) Th²³¹ has been measured by the activation method from the threshold energy, 6.34 Mev, to 20.4 Mev, relative to the known cross section for the S³² (n,p)P³² reaction. Monoenergetic neutrons were obtained from the D (d,n) He³ and T (d,n) He⁴ reactions employing a Tandem Van de Graaff accelerator. From threshold to 9.0 Mev, the (n,2n) cross section rises rapidly, reaching its maximum value of 1.88 ± 0.09 barns in the region of 9.5 to 11.0 Mev. Above 11.5 Mev the (n,2n) cross section decreases due to competition of the (n,3n) and (n,2nf) reactions and at 20.4 Mev it has a value of 0.225 ± 0.01₅ barns.