High-Resolution Cross-Section Measurements for Production of the 0.478-MeV Gamma Ray from the {sup 9}Be(n,x{gamma}){sup 7}Li Reaction for Neutron Energies Between 12 and 200 MeV with Insight into the {sup 10}Be Level Scheme

Journal Article · Fri Mar 15 04:00:00 EST 2002 · Nuclear Science and Engineering

OSTI ID:20804767

Nelson, R O; Michaudon, A ^[1]

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1. Los Alamos National Laboratory (United States)

Because of the low-energy threshold and relatively large cross section of the {sup 9}Be(n,2n) reaction, beryllium is a very attractive neutron multiplier for some fast-neutron systems, such as those used in the production of fusion energy. But, tritium is also produced when beryllium is irradiated with 14-MeV neutrons emitted from the fusion of deuterium and tritium ions. Among the two exit channels of the {sup 9}Be(n,t){sup 7}Li reaction of {approx}14-MeV incident-neutron energy, the {sup 9}Be(n,t{sub 1}{gamma}){sup 7}Li channel also emits a 0.478-MeV gamma ray. The purpose of the present study is to measure the cross section for the {sup 9}Be(n,t{sub 1}{gamma}){sup 7}Li reaction and also that of the more general {sup 9}Be(n,x{gamma}){sup 7}Li reaction with the production of the same 0.478-MeV gamma ray for incident-neutron energies from the 12-MeV threshold to 200 MeV. Because the {sup 7}Li levels excited above 0.478 MeV are unstable against particle emission, the study of the {sup 9}Be(n,t{sub 1}{gamma}){sup 7}Li reaction gives direct access to the cross section for the formation of {sup 7}Li* in its 0.478-MeV excited state. The few previous experimental data for this reaction are restricted to incident-neutron energies of {approx}14 MeV with large discrepancies between the results. The present data are obtained with a BeO sample, using the pulsed source of high-energy neutrons of the Weapons Neutron Research Facility (WNR) at the Los Alamos Neutron Science Center (LANSCE). The 478-keV gamma rays emitted in {sup 9}Be(n,x{gamma}){sup 7}Li reactions are detected with two high-resolution Ge detectors. The data thus obtained are presented and compared with previous data on the {sup 9}Be(n,t{sub 1}{gamma}){sup 7}Li and the {sup 9}Be(n,t){sup 7}Li reactions. Examination of the present data also provides insight into the {sup 10}Be level scheme.

• OSTI ID: 20804767
• Journal Information: Nuclear Science and Engineering, Journal Name: Nuclear Science and Engineering Journal Issue: 3 Vol. 140; ISSN NSENAO; ISSN 0029-5639
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
BERYLLIUM 10
BERYLLIUM 9 TARGET
BERYLLIUM OXIDES
CROSS SECTIONS
EXCITED STATES
FAST NEUTRONS
GAMMA RADIATION
GE SEMICONDUCTOR DETECTORS
KEV RANGE
LITHIUM 7
MEV RANGE
NEUTRON REACTIONS
NUCLEAR STRUCTURE
PHOTON EMISSION