Thermal neutron capture cross section and resonance integral of the La-139(n,gamma)La-140 reaction

Abstract

The thermal neutron capture cross section (sigma(o)) and resonance integral cross section (I-0) of the La-139(n,gamma)La-140 reaction have been measured relative to that of the Au-197(n,gamma)Au-198 reaction by means of the activation method. High-purity natural lanthanum and gold foils were exposed to pulsed neutrons at the Pohang neutron facility. One set of foils was irradiated directly and a second set of foils was shielded with a cadmium cover of 0.5 mm thickness. The induced activities in the activated foils were measured by a gamma-ray spectrometer based on a calibrated high purity germanium (HPGe) detector. In order to improve the accuracy of the experimental results the epithermal neutron spectrum shape factor (alpha) was determined, and the corrections for the thermal neutron self-shielding (G(th)), the resonance neutron self-shielding (G(epi)), the gamma-ray attenuation (F-g) and the gamma-ray coincidence summing effects were made. The thermal neutron cross-section for the La-139(n,gamma)La-140 reaction has been determined to be 9.16 +/- 0.36 barn, relative to the reference value of 98.65 +/- 0.09 barn for the Au-197(n,gamma)Au-198 reaction. By assuming the cadmium cut-off energy of 0.55 eV, the resonance integral cross section for the La-139(n,gamma)La-140 reaction is 11.64 +/- 0.69 barn, which is determined relative to the reference value of 1550 +/- 28 barn for the Au-197(n,gamma)Au-198 reaction. The measured results are compared with literature values and discussed. (C) 2014 Elsevier B.V. All rights reserved.