MEASUREMENT OF THE ACTIVATION CROSS-SECTION FOR THE REACTION NB-93(N,N')93MNB IN THE NEUTRON ENERGY-RANGE 6-9-MEV

The cross section for the production of the 30 keV isomer in Nb-93 by neutron inelastic scattering was measured by means of foil activation in the energy range 5.93-8.94 MeV relative to the cross section for the reaction (Ni(n,p)Co)-Ni-58-Co-58. Thin Nb foils attached to Ni monitor foils were exposed to a high flux of quasi-monoenergetic neutrons produced by the (H(t,n)He)-He-3 source reaction at incident triton energies between 11.5 and 15.1 MeV. The effect of secondary neutrons on the activation of both the Nb and Ni samples was corrected for at each energy by carrying out irradiation runs with the hydrogen gas-cell evacuated. The induced Nb-93m activities were assessed by measuring the K-shell X-rays from the 30.7 keV isomeric transition by means of a calibrated Si(Li) X-ray detector; the Co-58 activity in the monitor foils were measured by means of standard gamma-ray counting techniques using a calibrated high-purity Ge detector. The (Ni(n,p)Co)-Ni-58-Co-58 cross section, employed as a secondary reference, had been determined in a previous experiment relative to the (U(n,f))-U-238 cross section which was taken from the ENDF/B-VI file. Within the experimental uncertainties the results of this work confirm the recommended cross sections contained in the IRDF-90.