COLD NEUTRON PROMPT GAMMA-RAY ACTIVATION-ANALYSIS AT NIST - RECENT DEVELOPMENTS

The cold neutron capture prompt gamma-ray activation analysis (CNPGAA) spectrometer located in the Cold Neutron Research Facility (CNRF) at NIST has proven useful for the analysis of hydrogen and other elements in a wide variety of materials. Modifications of the instrument and t he CNRF have resulted in improved measurement capabilities for PGAA. T he addition of an atmosphere-controlled sample chamber and Compton sup pression have reduced gamma-ray background and increased signal-to-noi se ratio. More recent revisions are expected to yield still further im provement in analytical capabilities. Replacement of the D2O ice cold source with a liquid H-2 moderator is expected to yield a 5-10 fold in crease in neutron capture rate, and improved neutron and gamma-ray shi elding will result in further reduction of the background Other modifi cations to the instrument allow easier sample mounting and mon: precis e positioning of samples in the neutron beam. Significant improvements in detection limits and analytical accuracy are expected.