Thermal neutron capture cross-section measurements using a cold neutron beam

The PGAA-NIPS experimental facilities of the Budapest Research Reactor (BRR) were presented. The neutrons produced by the 10-MW BRR are cooled by a liquid hydrogen cold source and are guided to the PGAA-NIPS facility by super mirror guides. The gammas emitted from the neutron capture activated samples are detected by a Compton-suppressed Hyperpure Germanium detector (HPGe) system. The activation by cold neutrons avoids the influence of the first resonance of most isotopes, including 241Am, and thus provides independent data from the usual instrumental neutron activation for thermal cross-sections. The use of the beam chopper option improves the detection conditions. Neutron capture cross-sections are determined by several methods based on partial gamma-ray cross-section measurements. Until now, we have measured the partial gamma-ray and derived the thermal cross-sections of most stable elements and a few radioactive targets, such as 99Tc and 129I. New intensities were calculated for the primary calibration reaction of 14N(n,γ)15N based only on basic principles, which may have influenced the high-energy detector efficiencies. The ground-state capture cross-section of 241Am using in-beam and activation experiments with different conditions and targets will be measured in collaboration with the Institute for Reference Materials and Measurements (IRMM) and Commissariat a l'Energie Atomique (CEA). Further experiments have been suggested to clarify the contradictions of existing capture cross-sections for 237Np. We need to obtain about 10 mg of 237Np from IRMM in order to proceed with this experiment