Measurement of thermal neutron cross section and resonance integral for the ¹⁶⁵Ho(n, γ)^166gHo reaction

Abstract

The ground state thermal neutron cross section and the resonance integral for the ¹⁶⁵Ho(n, γ) ¹⁶⁶Ho reaction in thermal and 1/E regions, respectively, of a thermal reactor neutron spectrum have been measured experimentally by activation technique. The reaction product, ¹⁶⁶Ho in the ground state, is gaining considerable importance as a therapeutic radionuclide and precisely measured data of the reaction are of significance from the fundamental point of view as well as for application. In this work, the spectrographically pure holmium oxide (Ho₂O₃) powder samples were irradiated with and without cadmium covers at the IEA-R1 reactor (IPEN, São Paulo), Brazil. The deviation of the neutron spectrum shape from 1/E law was measured by co-irradiating Co, Zn, Zr and Au activation detectors with thermal and epithermal neutrons followed by regression and iterative procedures. The magnitudes of the discrepancies that can occur in measurements made with the ideal 1/E law considerations in the epithermal range were studied.

The measured thermal neutron cross section at the Maxwellian averaged thermal energy of 0.0253 eV is 59.0±2.1 b and for the resonance integral 657±36 b. The results are measured with good precision and indicated a consistency trend to resolve the discrepant status of the literature data. The results are compared with the values in main libraries such as ENDF/B-VII, JEF-2.2 and JENDL-3.2, and with other measurements in the literature.