R-matrix analysis of Cl neutron cross sections up to 1.2 MeV

Abstract

We have analyzed and evaluated $^{35}\mathrm{Cl}$, $^{37}\mathrm{Cl}$, and ${}^{\mathrm{nat}}$Cl neutron cross section data in the resolved resonance region with the multilevel Reich-Moore R-matrix formalism. Energies and widths were determined for 388 resonances in the range 0.2 to 1200 keV. New J assignments were made for 33 resonances, and parities were assigned for 15 of these resonances. Neutron strength functions were calculated for both s and p waves; our results include the first reported p-wave values for Cl. Resonance analyses were carried out with the computer code SAMMY, which utilizes Bayes' method, a generalized least-squares technique. Because SAMMY now has the ability to calculate charged-particle penetrabilities, it was possible to include a proton exit channel in the analysis and to deduce proton widths for several resonances. Our resonance parameter representation describes the data much better than pre-vious evaluations, and it should lead to improved criticality safety calculations for systems where Cl is present.