D. C. Larson

Measurement of 7Li(n,γ0)8Li cross sections at En=1.5-1340 eV

The {sup 7}Li({ital n},{gamma}){sup 8}Li cross section is important in inhomogeneous big bang models, and as a constraint on model parameters used to determine the solar {sup 7}Be({ital p},{gamma}){sup 8}B reaction rate. Values of the {sup 7}Li({ital n},{gamma}{sub 0}){sup 8}Li reaction cross section were measured for neutron energies between 1.5 and 1340 eV at the Oak Ridge Electron Linear Accelerator. The normalization of the cross section was determined by measuring the gamma-ray yield from the {sup 7}Li({ital n},{gamma}{sub 0}){sup 8}Li reaction relative to that from the {sup 10}B({ital n},{alpha}{gamma}){sup 7}Li reaction. The cross section was found to have the inverse neutron-velocity relationship (1/{ital v}) indicative of {ital s}-wave capture. These results help resolve ambiguities in previous measurements. {copyright} {ital 1996 The American Physical Society.}

Measurement of {sup 7}Li({ital n},{gamma}{sub 0}){sup 8}Li cross sections at {ital E}{sub {ital n}}=1.5{endash}1340 eV

The {sup 7}Li({ital n},{gamma}){sup 8}Li cross section is important in inhomogeneous big bang models, and as a constraint on model parameters used to determine the solar {sup 7}Be({ital p},{gamma}){sup 8}B reaction rate. Values of the {sup 7}Li({ital n},{gamma}{sub 0}){sup 8}Li reaction cross section were measured for neutron energies between 1.5 and 1340 eV at the Oak Ridge Electron Linear Accelerator. The normalization of the cross section was determined by measuring the gamma-ray yield from the {sup 7}Li({ital n},{gamma}{sub 0}){sup 8}Li reaction relative to that from the {sup 10}B({ital n},{alpha}{gamma}){sup 7}Li reaction. The cross section was found to have the inverse neutron-velocity relationship (1/{ital v}) indicative of {ital s}-wave capture. These results help resolve ambiguities in previous measurements. {copyright} {ital 1996 The American Physical Society.}

Measurement ofLi7(n,γ0)8Li cross sections atEn=1.5–1340 eV

The {sup 7}Li({ital n},{gamma}){sup 8}Li cross section is important in inhomogeneous big bang models, and as a constraint on model parameters used to determine the solar {sup 7}Be({ital p},{gamma}){sup 8}B reaction rate. Values of the {sup 7}Li({ital n},{gamma}{sub 0}){sup 8}Li reaction cross section were measured for neutron energies between 1.5 and 1340 eV at the Oak Ridge Electron Linear Accelerator. The normalization of the cross section was determined by measuring the gamma-ray yield from the {sup 7}Li({ital n},{gamma}{sub 0}){sup 8}Li reaction relative to that from the {sup 10}B({ital n},{alpha}{gamma}){sup 7}Li reaction. The cross section was found to have the inverse neutron-velocity relationship (1/{ital v}) indicative of {ital s}-wave capture. These results help resolve ambiguities in previous measurements. {copyright} {ital 1996 The American Physical Society.}

Measurement of Li-7 (n, gamma0) Li-8 cross sections at En=1.5-1340 eV

The {sup 7}Li({ital n},{gamma}){sup 8}Li cross section is important in inhomogeneous big bang models, and as a constraint on model parameters used to determine the solar {sup 7}Be({ital p},{gamma}){sup 8}B reaction rate. Values of the {sup 7}Li({ital n},{gamma}{sub 0}){sup 8}Li reaction cross section were measured for neutron energies between 1.5 and 1340 eV at the Oak Ridge Electron Linear Accelerator. The normalization of the cross section was determined by measuring the gamma-ray yield from the {sup 7}Li({ital n},{gamma}{sub 0}){sup 8}Li reaction relative to that from the {sup 10}B({ital n},{alpha}{gamma}){sup 7}Li reaction. The cross section was found to have the inverse neutron-velocity relationship (1/{ital v}) indicative of {ital s}-wave capture. These results help resolve ambiguities in previous measurements. {copyright} {ital 1996 The American Physical Society.}

Measurement and Analysis of the Nitrogen Total and Differential Scattering Cross Sections in the Resonance Region

High-resolution neutron transmission and differential elastic scattering measurements have been made on samples of nitrogen from 0.5 eV to 10 MeV at the Oak Ridge Electron Linear Accelerator (ORELA). For the transmission measurement several different detectors were used at various flight path lengths, with high-purity nitrogen gas samples. The data have been corrected for the dead time of the time digitizer and for several small backgrounds. For the scattering measurements six detectors were placed at various angles inside an evacuated scattering chamber at 200 meters from the neutron producing target. The sample was silicon nitride held in a thin graphite container. Scattering from carbon and silicon samples was also measured to correct for these materials and calibrate the relative efficiencies of the scattering detectors. The data have been corrected for dead time and for a constant background. A preliminary analysis has been completed to obtain parameters of the resonances up to 4.8 MeV.

Measurement of the Nitrogen Total Cross Section from 0.5 eV to 50 MeV, and Analysis of the 433-keV Resonance

High-resolution neutron transmission measurements have been made on several thicknesses of nitrogen gas samples from 0.5 eV to 50 MeV at the Oak Ridge Electron Linear Accelerator (ORELA). A preliminary R-matrix analysis has been done for resonances up to 800 keV. An R-matrix analysis of previous data was done by LANL for ENDF/B-VI, including the lowest energy resonance in 14N at 433 keV. They found a spin of 3/2 (with l = 1) and a peak cross section of 7.0 b. Analysis of the present data yield a spin of 7/2 (requiring l ≥ 2) and a peak cross section of 11.5 b for this resonance. These results are important for transport calculations of neutrons through air. Scattering measurements are planned to determine the parity of this resonance.