Bulletin of the American Physical Society
2012 Fall Meeting of the APS Division of Nuclear Physics
Volume 57, Number 9
Wednesday–Saturday, October 24–27, 2012; Newport Beach, California
Session CE: Nuclear Reactions: Hadrons/Light Ions |
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Chair: Calvin Howell, Duke University Room: Garden I |
Thursday, October 25, 2012 8:30AM - 8:42AM |
CE.00001: Measurement of the Neutron-Proton and Neutron-Carbon Total Cross Section from 150 to 800 keV M. Kovash, Z. Miller, K. Shoniyozov, H. Yang, B. Daub, V. Henzl, J. Matthews There have been very few measurements of the total cross section for $np$ scattering below 500 keV. In order to differentiate among $NN$ potential models, improved cross section data between 20 and 600 keV are required. We measured the $np$ and $n$C total cross sections in this energy region by transmission; a collimated neutron beam was passed through CH$_2$ and C samples and transmitted neutrons were detected with a BC501 liquid scintillator. Cross sections were obtained between 150 and 800 keV by taking the ratios of normalized neutron yields with the samples in the beam and with no sample in the beam. The parameters resulting from fitting effective range theory to the data for $np$ scattering are in good agreement with parameters determined from previous fits. [Preview Abstract] |
Thursday, October 25, 2012 8:42AM - 8:54AM |
CE.00002: Measurements of the $^{89}$Y(n,n')$^{89}$Y$^{m}$ reaction cross section using the ASP D-T fusion source Andrew Simons, Matthew Gardner, Ben Williams, Michael Rubery A programme of measurements of the $^{89}$Y(n,n')$^{89}$Y$^{m}$ reaction cross section has commenced at AWE using the ASP accelerator to impinge deuterons onto tritiated titanium layers mounted on copper discs producing fluxes of approximately 10$^{11}$ neutrons per second. The neutrons are generated for up to half an hour and are used to excite Yttrium into its first isomeric state at 909.1 keV which then decays with a half life of 15.7 seconds. Two other high purity foils (of $^{27}$Al and $^{63,65}$Cu) are used as a reference to establish consistency between the isotopes energetic and temporal decay signatures. These foils mainly serve to check the reported total neutron fluence, produced by the accelerator, incident on the targets. The activation foils are extracted from the irradiation position by a pneumatic transfer system in $\sim $ 7 seconds and are transferred to the counting station in 5 to 30 seconds. Data are taken with a BEGe detector and recorded with both a Canberra Genie analogue system and a Xia Pixie-4 digital system. The results from the first campaigns are presented with a discussion of improvements and future plans. [Preview Abstract] |
Thursday, October 25, 2012 8:54AM - 9:06AM |
CE.00003: Neutron Capture and Fission Measurement on $^{238}$Pu at DANCE Andrii Chyzh, Ching-Yen Wu, Elaine Kwan, Roger Henderson, Jolie Gostic, Aaron Couture, Hye Young, John Ullmann, John O'Donnell, Marian Jandel, Robert Haight, Todd Bredeweg Neutron capture and fission reactions on actinides are important in nuclear engineering and physics. DANCE (Detector for Advanced Neutron Capture Measurement, LANL) combined with PPAC (avalanche technique based fission tagging detector, LLNL) were used to study the neutron capture reactions in $^{238}$Pu. Because of extreme spontaneous $\alpha$-radioactivity in $^{238}$Pu and associated safety issues, 3 separate experiments were performed in 2010-2012. The 1st measurement was done without fission tagging on a 396-$\mu$g thick target. The 2nd one was with PPAC on the same target. The 3rd final measurement was done on a thin target with a mass of 40 $\mu$g in order to reduce $\alpha$-background load on PPAC. This was the first such measurement in a laboratory environment. The absolute $^{238}$Pu(n,$\gamma$) cross section is presented together with the prompt $\gamma$-ray multiplicity in the $^{238}$Pu(n,f) reaction. [Preview Abstract] |
Thursday, October 25, 2012 9:06AM - 9:18AM |
CE.00004: Modernizing the Fission Basis C. Bhatia, B. Fallin, C. Howell, W. Tornow, M. Gooden, J. Kelley, C. Arnold, E. Bond, T. Bredeweg, M. Fowler, W. Moody, R. Rundberg, G. Rusev, D. Vieira, J. Wilhemy, J. Becker, R. Macri, C. Ryan, S. Sheets, M. Stoyer, A. Tonchev A recent Fission Product Review Panel study has identified important issues associated with the possible neutron energy dependence of the fission product isotope $^{147}$Nd. As a result, we initiated a program at TUNL to obtain high-precision and self-consistent data for the energy dependence of fission product yields in the 1 to 15 MeV energy range. Three dual fission ionization chambers dedicated to $^{235}$U, $^{238}$U, and $^{239}$Pu thick target foils and thin monitor foils, respectively, were exposed to neutron beams produced via the reactions $^{2}$H(d,n)$^{3}$He and $^{3}$H(d,n)$^{4}$He. After irradiation, the characteristic $\gamma $ rays from specific fission products were recorded over a period of many weeks using HPGe detectors in a low-background environment. Results for the yield of seven fission isotopes obtained at 4.6, 9.0 and 14.8 MeV are reported. [Preview Abstract] |
Thursday, October 25, 2012 9:18AM - 9:30AM |
CE.00005: ANC measurement on ($^6$Li,d) reactions M.L. Avila, G.V. Rogachev, E. Koshchiy Direct measurement of many astrophysically important reactions cannot be done due to small cross sections. An alternative can be to obtain the Asymptotic Normalization Coefficient (ANC) as an effective method to determine the astrophysical S factor. Combination of the sub-Coulomb $\alpha$-transfer reaction and application of the ANC technique in the analysis of the experimental data practically eliminates all dependence of the result on model parameters, making this approach a very valuable tool for studies of astrophysically important reaction rates. In this study we report the ANC measurements of near threshold states for ($^6$Li,d) reactions performed at sub-Coulomb energies at the Florida State University Tandem-LINAC facility. The reactions that were studied using this technique are $^{16}$O($^6$Li,d)$^{20}$Ne, $^{13}$C($^6$Li,d)$^{17}$O and $^{12}$C($^6$Li,d)$^{16}$O. [Preview Abstract] |
Thursday, October 25, 2012 9:30AM - 9:42AM |
CE.00006: A re-examination of the non-equ1ibrium emission in (p,n) reactions Nikolay Kornilov, Steven Grimes, Alexander Voinov Re-analysis of old experimental neutron spectra from (p,n) reactions allows us to reveal very interesting peculiarities which never were discussed before. The neutron spectrum due to the direct mechanism in particular its high energetic part changes very much from one isotope to other. We describe this difference with incorporation of two components which provide the ``broad bump,'' or ``step like'' shape of neutron spectra at high energy. The properties of these components are: different shape, energy shift between them, and very strong fluctuation between different isotopes for ratio of cross sections connected with partial contribution. In this report we discuss the method applied for data analysis, final results and conclusions. We demonstrated also possible influence and importance of this result for practical application -- nuclear data calculation. [Preview Abstract] |
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