Fast Neutron Activation of 48.6-min ^111mCd in Natural Cadmium

The 48.6-min isomeric state at 0.396 MeV in ¹¹¹Cd can be excited by the neutron reactions ¹¹⁰Cd(n,γ)^111mCd, ¹¹¹Cd(n,′)^111mCd, and ¹¹²Cd(n, 2n)^111mCd. When natural cadmium is bombarded with fast neutrons, the influence of these reactions on the activation response varies according to the nature of the neutron spectrum. For a predominantly low-energy spectrum, the nonthreshold reaction ¹¹⁰Cd(n,γ)^111mCd dominates, while for a relatively hard spectrum, the threshold reactions ¹¹¹Cd(n,n′)^111mCd and ¹¹²Cd(n,2n)^111mCd are the most influential This situation offers interesting possibilities for utilization of elemental cadmium samples as neutron activation dosimeters in reactor applications. Accordingly, the elemental differential cross section for ^111mCd excitation has been measured for cadmium over the energy range 0.135 to 10.01 MeV using activation techniques, and the response of this excitation function has been investigated for a standard fission-neutron spectrum. Some implications of these results for dosimetry applications are examined.