Average Thermal Neutron Capture Cross Sections of ¹⁹⁸Au, ⁶⁵Ni, And ⁶⁶Cu

The average thermal, neutron capture cross sections of ¹⁹⁸Au, ⁶⁵Ni, and ⁶⁶ Cu have been measured by activation of the stable isotopes ¹⁹⁷Au, ⁶⁴Ni, and ⁶⁵Cu, using y spectrometry techniques and assuming established values for the cross sections of the stable isotopes. The samples were exposed to thermal neutron fluxes up to 2.6 *10¹⁴ n/(cm² sec) during long times in order to obtain enough activity of the isotopes ¹⁹⁹Au, ⁶⁶Ni, and ⁶⁷Cu. The values of these cross sections as determined from these activities are 28 300, 24.3, and 145 b, respectively. These values have a maximum error of 10%. Isotopes enriched to more than 97% were used for the Ni and Cu measurements.