Browsing by Author "Walter, RL"

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    Differential cross section for neutron scattering from Bi209 at 37 MeV and the weak particle-core coupling
    (Physical Review C - Nuclear Physics, 2010-08-03) Zhou, Zuying; Ruan, Xichao; Du, Yanfeng; Qi, Bujia; Tang, Hongqing; Xia, Haihong; Walter, RL; Braun, RT; Howell, CR; Tornow, W; Weisel, GJ; Dupuis, M; Delaroche, JP; Chen, Zemin; Chen, Zhenpeng; Chen, Yingyang
    Differential scattering cross-section data have been measured at 43 angles from 11° to 160° for 37-MeV neutrons incident on Bi209. The primary motivation for the measurements is to address the scarcity of neutron scattering data above 30 MeV and to improve the accuracy of optical-model predictions at medium neutron energies. The high-statistics measurements were conducted at the China Institute of Atomic Energy using the H3(d,n)He4 reaction as the neutron source, a pulsed deuteron beam, and time-of-flight (TOF) techniques. Within the resolution of the TOF spectrometer, the measurements included inelastic scattering components. The sum of elastic and inelastic scattering cross sections was computed in joint optical-model and distorted-wave Born approximation calculations under the assumption of the weak particle-core coupling. The results challenge predictions from well-established spherical optical potentials. Good agreement between data and calculations is achieved at 37 MeV provided that the balance between surface and volume absorption in a recent successful model is modified, thus suggesting the need for global optical-model improvements at medium neutron energies. © 2010 The American Physical Society.
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    Neutron-deuteron analyzing power data at 19.0 MeV
    (Physical Review C - Nuclear Physics, 2010-02-23) Weisel, GJ; Tornow, W; Crowe, BJ; Crowell, AS; Esterline, JH; Howell, CR; Kelley, JH; Macri, RA; Pedroni, RS; Walter, RL; Witała, H
    Measurements of neutron-deuteron (n-d) analyzing power Ay(θ) at En=19.0 MeV are reported at 16 angles from θc.m.=46.7 to 152.0°. The objective of the experiment is to better characterize the discrepancies between n-d data and the predictions of three-nucleon calculations for neutron energies above 16.0 MeV. The experiment used a shielded neutron source, which produced polarized neutrons via the H2(d-,n-)He3 reaction, a deuterated liquid scintillator center detector (CD) and liquid-scintillator neutron side detectors. A coincidence between the CD and the side detectors isolated the elastic-scattering events. The CD pulse height spectrum associated with each side detector was sorted by using pulse-shape discrimination, time-of-flight techniques, and by removing accidental coincidences. A Monte Carlo computer simulation of the experiment accounted for effects due to finite geometry, multiple scattering, and CD edge effects. The resulting high-precision data (with absolute uncertainties ranging from 0.0022 to 0.0132) have a somewhat lower discrepancy with the predictions of three-body calculations, as compared to those found at lower energies. © 2010 The American Physical Society.