Illuminating photon production with GEANIE at LANSCE

Journal Article · Thu Jul 01 04:00:00 EDT 1999 · Transactions of the American Nuclear Society

OSTI ID:20005760

Nelson, R O

GEANIE is a multidetector, high-resolution gamma-ray spectrometer that is operated as a collaborative effort between Lawrence Livermore National Laboratory and Los Alamos National Laboratory. The Weapons Neutron Research high-energy spallation neutron source at the Los Alamos Neutron Science Center provides GEANIE's beam. GEANIE enables new measurements of neutron-induced reaction cross sections and fission fragment studies with neutrons with incident energies from 1 to 200 MeV and excellent gamma-ray energy resolution. Results of first studies are designed to provide information for such diverse needs and calibration of high-energy neutron fluence monitors for applications in the accelerator production of tritium and accelerator transmutation of waste. Current efforts with GEANIE are focused on determining the {sup 239}Pu(n,2n){sup 238}Pu reaction cross section from threshold to 15 MeV from gamma-ray measurements. Because of the large fission-neutron background, this reaction is difficult to measure by neutron detection techniques. Only two direct measurements of this cross section as a function of neutron energy from threshold to higher energies have been reported, with large differences in the results. By measuring many partial gamma-ray cross sections in the decay cascade and modeling the reaction with a sophisticated preequilibrium-plus-Hauser-Feshbach computer program (GNASH), the author expects to achieve an absolute cross-section measurement of 10% accuracy or better. Key to current efforts has been the production of a very pure {sup 239}Pu sample with almost all {sup 241}Am removed. As a test of their methods, and for other interests, he is measuring the {sup 235}U(n,n{prime}{gamma}) and (n,2n{gamma}) cross sections and {sup 238}U(n,xn{gamma}) reactions. The author is starting a program of fission fragment studies with French collaborators to look at spontaneous fission and neutron-induced fission.

• Research Organization: Los Alamos National Lab., NM (US)
• OSTI ID: 20005760
• Journal Information: Transactions of the American Nuclear Society, Journal Name: Transactions of the American Nuclear Society Vol. 81; ISSN 0003-018X; ISSN TANSAO
• Country of Publication: United States
• Language: English

Related Subjects

43 PARTICLE ACCELERATORS
44 INSTRUMENTATION
66 PHYSICS
ACCELERATOR FACILITIES
CROSS SECTIONS
FISSION FRAGMENTS
GAMMA SPECTROMETERS
GE SEMICONDUCTOR DETECTORS
NEUTRON REACTIONS
NEUTRON SOURCES
PLUTONIUM 239 TARGET
URANIUM 235 TARGET