Determination of the 232Th(n, γ) Cross Section from 4 to 140 keV at GELINA

• Published in: Nuclear science and engineering Vol. 152; no. 1; pp. 1 - 14
• Main Authors: Borella, A., Volev, K., Brusegan, A., Schillebeeckx, P., Corvi, F., Koyumdjieva, N., Janeva, N., Lukyanov, A. A.
• Format: Journal Article
• Language: English
• Published: La Grange Park, IL Taylor & Francis 01.01.2006; American Nuclear Society
• Subjects: Applied sciences; Energy; Energy. Thermal use of fuels; Exact sciences and technology; Experimental methods and instrumentation for elementary-particle and nuclear physics; Fission nuclear power plants; Installations for energy generation and conversion: thermal and electrical energy; Neutron sources; Nuclear physics; Particle sources and targets; Physics; Belgium; Europe; Neutron source; Neutron flux; Uncertainty; Neutron capture; Excitation energy; Self-shielding; Multiple scattering; Detection; Cross section (collision); Thorium 232; Cascade
• ISSN: 0029-5639; 1943-748X
• DOI: 10.13182/NSE06-A2557

The neutron capture cross section of thorium has been measured in the energy region between 4 and 140 keV at the GELINA time-of-flight facility of the Institute for Reference Materials and Measurements in Geel, Belgium. The gamma rays from capture events were detected by two C 6 D 6 liquid scintillators, placed 14.37 m from the neutron source. The shape of the neutron flux was measured with a 10 B-loaded ionization chamber. To obtain a detection efficiency independent of the gamma cascade and proportional to the total excitation energy, the pulse-height weighting technique was applied. The data have been normalized to the well-isolated and almost saturated 232 Th resonance at 23.5 eV. The systematic uncertainties related to the normalization and weighting function, using an internal saturated resonance, are ~1.5%. An additional systematic uncertainty of 0.5% results from the self-shielding and multiple scattering corrections. Between 4 and 140 keV, our data are ~9 and 6.5% higher than the data of Kobayashi et al. and Macklin et al., respectively, and in good agreement with the data of Poenitz and Smith. Below 15 keV our data deviate by up to 30% from the data reported by Wisshak et al. Our data have been analyzed in terms of average level parameters. The resulting parameters are consistent with the resolved resonance parameters deduced from the transmission measurements of Olsen et al.