Low energy transmission measurements of ^240,242Pu at GELINA and their impact on the capture width

Abstract
We present an approach to account for sample inhomogeneities as observed in thin powder samples. To test this model a series of transmission measurements on enriched ²⁴⁰Pu and ²⁴²Pu oxide samples was carried out. These measurements were performed at GELINA, the pulsed, white neutron source at the Institute for Reference Materials and Measurements in Geel. For all samples a mixture of PuO₂ and graphite powder was used. To reduce the influence of the models for Doppler broadening on the extracted resonance parameters, measurements were performed with sample temperatures of approximately 12 K, 77 K and 300 K. To describe the variation in the sample thickness, caused by the particle distribution in a thin powder sample, a Monte Carlo and an analytical description were used in the resonance shape analysis. The values and uncertainties of the extracted resonance parameters are discussed, and suggestion for future measurements are given.