Abstract
The effects of epithermal neutron flux an isotropy upon the cadmium correction factor F[subscript cd] have been determined both theoretically and experimentally for indium foils in a water medium. Spencer's and Fano's solution of the neutron transport equation was used to determine the values of the magnitude of the vector flux so that the theoretical bare and cadmium covered activities could be determined. It was shown that this solution gave correct values for the flux only if the weight function was chosen properly. From the theoretical considerations it was found that the experimental data should be plotted as a function of linear combinations of exponential integral functions of the cadmium cover thickness to determine F[subscript cd]. This fit of the experimental data was designated as an E[subscript n] fit. The experimental data was obtained by irradiating cadmium 2 covered indium foils with thicknesses varying from 37 mg/cm² to 148 mg/cm² at various distances out from a plane source of Pu-Be neutrons. It was found that F[subscript cd], decreased in value as the distance between the source and detector increased, and that near the source F[subscript cd], was essentially independent of foil thickness. As the distance between the source and detector increased F[subscript cd], became more a function of foil thickness. Substantial agreement was obtained between the experimental and theoretical results except near the source. In addition to the E[subscript n] fits, logarithmic fits were performed on the experimental data to determine F[subscript cd], and the resulting values were compared with the E[subscript n] values. The logarithmic values differed from the E[subscript n] values by a maximum of 5% near the source, but were almost identical to the E[subscript n] values at the farthest positions from the source.
Powell, James Edward (1965). The effects of epithermal neutron flux anisotropy on cadmium correction factors. Doctoral dissertation, Texas A&M University. Texas A&M University. Libraries. Available electronically from
https : / /hdl .handle .net /1969 .1 /DISSERTATIONS -177162.