Doppler and Self-Shielding Effects of Resonances in Unresolved Energy Region of Niobium

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The purpose of the present work is to investigate the Doppler effect and the self-shielding effect of resonances in the unresolved energy region of Nb. The effective average total cross sections (abbreviated EATCS hereinafter) of Nb were measured by using filtered neutron beam of 24, 54 and 144 keV as a function of sample thickness at room temperature for the self-shielding experiments. The measurement for the Doppler broadening effect has also been made at 600°C by using the 24-keV neutrons to observe any sensitivity of the Doppler effect with respect to the temperature. The methods have been reported for U and Sn by Tsang et al.⁽¹⁾ and for Th by Kobayashi et al.⁽²⁾ and Fujita et al.⁽³⁾ We have also compared the experimental results with the results calculated by the U3R code⁽⁴⁾ by using the JENDL-2 file⁽⁵⁾.