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Neutron and gamma pulse shape discrimination in a liquid scintillator counter for neutron multiplicity measurements of enriched uranium

Conference ·
OSTI ID:977763
A new neutron multiplicity counter is being developed which utilizes the fast response of liquid scintillator (NE-213) detectors. Current uranium coincidence counting methods rely on the assay samples to conform to the calibration standards with respect to the sample uniformity, geometry, material type, etc. There exists a wide range of material throughout the DOE complex where these attributes are non-standard or unknown. A neutron counter with short die-away time makes possible the measurement of higher order coincidences. This information can be used to more accurately assay many of the problem items in the inventory. In addition, such a counter would allow for rapid inventory measurements of all forms of uranium. Liquid scintillator detectors also allow for energy discrimination between interrogation source neutrons and fission neutrons, allowing for even greater assay sensitivity. Liquid scintillator detectors are sensitive to {gamma} and neutron radiation. Differences in the timing of scintillation light produced in {gamma}-ray and neutron interactions allows for separation of these events using pulse shape discrimination (PSD). PMT pulses resulting from neutron and {gamma} interactions in the Liquid scintillator are read in using a fast waveform digitizer with a 1 GS/s sampling rate. The pulse shapes are then compared to {gamma} and neutron pulse templates and a {chi}{sup 2} comparison determines the species. Integrated rise time can also be used to discriminate between they and neutron pulses. The results of these studies are presented.
Research Organization:
Los Alamos National Laboratory
Sponsoring Organization:
DOE
OSTI ID:
977763
Report Number(s):
LA-UR-04-4868
Country of Publication:
United States
Language:
English