Estimating Reaction Cross Sections from Measured (gamma)-ray Yields: The (238)U(n,2n) and (239)Pu(n,2n) Cross Sections

摘要

A procedure is presented to deduce the reaction-channel cross section from measured partial gamma-ray cross sections. In its simplest form, the procedure consists in adding complementary measured and calculated contributions to produce the channel cross section. A matrix formalism is introduced to provide a rigorous framework for this approach. The formalism is illustrated using a fictitious product nucleus with a simple level scheme, and a general algorithm is presented to process any level scheme. In order to circumvent the cumbersome algebra that can arise in the matrix formalism, a more intuitive graphical procedure is introduced to obtain the same reaction cross-section estimate. The features and limitations of the method are discussed, and the technique is applied to extract the (235)U(n,2n) and (239)Pu(n,2n) cross sections from experimental partial gamma-ray cross sections, coupled with (enhanced) Hauser-Feshbach calculations.