Measurement of neutron cross sections of Thorium-232 and investigation of BGO scintillation counter for capture gamma-ray detection

Total cross section from thermal to 20 eV and capture cross section from 1 to 400 keV have been measured by the time of flight method. The neutron was produced by a Ta photoneutron target irradiated with 30-MeV electron from the KUR linear accelerator. In the total cross section measurement, the transmitted neutrons through sample were detected with a 6Li glass scintillator 12.7 cm diam and 1.27 cm thick, placed at 22 m from the source. The experimental result of the present study is in good agreement with RPI'S and ORNL'S results, though our data show slightly higher in the energy range measured. While, the C6D6 scintillation detectors were used in the capture cross section measurement. In this case, the sample was mounted at a distance of 11.7 m from the source and the prompt gamma-rays following neutron capture were detected. The time of flight spectrum of neutron flux were obtained by detecting the 478-keV gamma-rays from 10B(n, αγ) reaction using the same detector. The capture rate as a function of neutron energy was normalized to the absolute value at 24 keV, obtained previously with an Fefiltered beam. The result agrees well with other data. The covariance method in the uncertainty analysis of the present data indicates the usefulness in understanding the uncertainties of the cross section data. A bismuth germanate (BGO) scintillator 10 cm diam and 2 cm thick was used to measure the gamma-ray spectra from the Au(n, γ) and the Pd(n, γ) reactions for the neutron of the energy 3 to 80 keV. The spectra were obtained by unfolding the observed ones with the response functions of the detector. The results are compared with other data for Au and with the calculated spectrum based on the statistical model for Pd. (author)