Measurement of the cross section for the reaction 93Nb(n,n') sup(93m)Nb at 2.8 MeV

The cross section for the reaction 93Nb(n, n') sup(93m)Nb was measured by foil activation to be (252.4 ± 10.9) mbarn at a neutron energy of 2.83 MeV relative to the 238U(n, f) cross section employing a small ionization chamber as fluence monitor. The mass of the fissionable deposit was calibrated relative to the mass of an Al foil by means of an irradiation experiment at 14.8 MeV using the ratio of the 238U(n, f) and 27Al(n, α) 24Na cross sections. The induced sup(93m)Nb activity was assessed by measuring the K-shell X-rays from the 30.7 keV isomeric transition by means of a Si(Li) X-ray detector. Source effects were taken into account determining experimentally the self-attenuation of the measured X-radiation and considering the extension and inhomogeneous activation of the source. The result indicates, together with other recently available experimental data, that the cross section information included in the International Reactor Dosimetry File should be revised. (author)