Thermal neutron cross section and resonance integral of the ¹⁵⁹Tb(n,γ)¹⁶⁰Tb reaction

The thermal neutron cross section and resonance integral of the reaction ¹⁵⁹Tb(n,γ)¹⁶⁰Tb in the thermal and 1∕E regions, respectively, of a thermal reactor neutron spectrum have been experimentally determined. Literature data on the resonance integral of the reaction show a large scatter ranging from 313 to 780 b. On the basis of such data it becomes extremely difficult to produce a best value for application. In this work we performed a careful experiment in an effort to produce a precise and accurate measured value, which will be a valuable addition to the literature. The ¹⁵⁹Tb(n,γ)¹⁶⁰Tb reaction is studied by irradiating spectrographically pure Tb₄O₇ powder samples with thermal and epithermal neutrons in the Pakistan Research Reactor–1 (PARR-1) at PINSTECH. Thermal and epithermal neutron fluence rates were determined with Au and Co activation detectors. The α parameter, which accounts for the deviation of the neutron spectrum shape from the 1∕E law in the epithermal neutron region, was obtained with good accuracy by using Au, Co, Mn, and Zn activation detectors and adopting the regression and iterative analysis procedures. The induced activities in the target samples and the activation detectors were measured with a high purity germanium detector system. The cadmium ratio method was used to yield the thermal neutron cross section and resonance integral. The measured thermal neutron cross section at 0.0253 eV and resonance integral are 23.6±0.4 b and 443±21 b, respectively. The results are discussed and compared with the literature.