Bulletin of the American Physical Society
2013 Fall Meeting of the APS Division of Nuclear Physics
Volume 58, Number 13
Wednesday–Saturday, October 23–26, 2013; Newport News, Virginia
Session JF: Nuclear Structure II |
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Chair: R.F. Casten, Yale University Room: Blue Point II |
Friday, October 25, 2013 10:30AM - 10:42AM |
JF.00001: ABSTRACT WITHDRAWN |
Friday, October 25, 2013 10:42AM - 10:54AM |
JF.00002: ABSTRACT WITHDRAWN |
Friday, October 25, 2013 10:54AM - 11:06AM |
JF.00003: Determination of Fission Product Yields of $^{235}$U, $^{238}$U and $^{239}$Pu for Neutron Energies from 0.5 to 14.8 MeV Matthew Gooden, Charles Arnold, John Becker, Chitra Bhatia, Megha Bhike, Brent Fallin, Malcolm Fowler, Calvin Howell, John Kelley, Mark Stoyer, Anton Tonchev, Werner Tornow, David Viera, Jerry Wilhelmy A joint TUNL-LANL-LLNL collaboration has been formed to study the issue of possible energy dependences for fission product isotopes. Work has been carried out at the TUNL 10 MV Tandem accelerator which produces nearly mono-energetic neutrons via either $^{2}$H(d,n)$^{3}$He,$^{3}$H(d,n)$^{4}$He, or $^{3}$H(p,n)$^{3}$He reactions. 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 the neutron beams. After irradiation, thick target foils were gamma counted over a period of 1-2 months and characteristic gamma rays from fission products were recorded using HPGe detectors at TUNL's low background counting area. Using the dual fission chambers fission product yields relative to total number of fissions were determined at a high precision of 2-3{\%} as well as absolute fission product yields at a lower precision of 5-6{\%}. Results will be presented for a number of fission product isotopes at 1.38, 4.6 and 14.8 MeV as well as preliminary results at 9 MeV. [Preview Abstract] |
Friday, October 25, 2013 11:06AM - 11:18AM |
JF.00004: ABSTRACT WITHDRAWN |
Friday, October 25, 2013 11:18AM - 11:30AM |
JF.00005: ABSTRACT WITHDRAWN |
Friday, October 25, 2013 11:30AM - 11:42AM |
JF.00006: Distribution of angular momentum transfers from ($p,d)$ and ($p,t)$ reactions in the high excitation energy continuum region of gadolinium nuclei Thomas Tarlow, Cornelius Beausang, Richard Hughes, Timothy Ross, Kristen Gell, Gargi Vyas The structure of even and odd Gd nuclei at low/moderate spins and up to high excitation energies in the vicinity of the N $=$ 90 shape change region have been probed using the (p,t) and (p,d) reactions on even-even targets. The proton beam, at a beam energy of 25 MeV, was provided by the 88-Inch Cyclotron at Lawrence Berkeley National Laboratory. Outgoing charged particles, between $\sim$30 and 60 degrees, were detected by the STARS silicon telescope while coincident gamma-rays were detected with the clover Ge detectors of the Liberace Array. The measured angular distributions for outgoing deuterons and tritons are well reproduced by DWBA calculations for discrete low-lying states, whereas at higher excitations of (2 -- 9) MeV the angular momentum distribution of the continuum region should be represented by a distribution of L-transfer values. The angular distribution of the continuum region has been investigated in the present work$.$ Weighted linear combinations of calculated (DWBA) angular distributions for L-transfer values of $\Delta $L$=$0 to 6$\hbar $ are compared to the experimental angular distribution in a chi-square minimization technique to find the best fitting distribution of angular momentum transfers in gadolinium nuclei. Preliminary results will be presented. [Preview Abstract] |
Friday, October 25, 2013 11:42AM - 11:54AM |
JF.00007: Experimentally Resolved Photo-Excitation Cross Sections Below the Neutron Separation Energy Nathan Cooper, Volker Werner Numerous nuclear resonance fluorescence experiments have been performed in recent years to study the photon strength function of nuclei up to $E_\gamma = S_n$ by measuring the photo-excitation cross section; however, accurate measurement of the total cross section remains an experimental challenge. A simple method of evaluating several aspects of experimentally resolvable photo-excitation cross sections below $E_x = S_n$ within a statistical model will be presented. The method used in the statistical code developed for this work differs from the widely-used DICEBOX algorithm [1] in that only transition widths of $\gamma$-rays which directly depopulate photo-excited states are sampled and converted into observable quantities, as production of a complete $\gamma$-ray intensity spectrum would be superfluous for this purpose. Available experimental data on the $N=50$ and $N=82$ isotonic chains will be compared with results using photon strength functions given by the standard Lorentzian and the model of Kadmenskii, Markushev, and Furman [2].\\[4pt] [1] F. Be\v{c}v\'{a}\v{r}, Nucl. Instrum. Meth. A 417, 434 (1998).\\[0pt] [2] S.G. Kadmenskii, V.P. Markushev, and V.I. Furman, Yad. Fiz. 37, 277 (1983). [Preview Abstract] |
Friday, October 25, 2013 11:54AM - 12:06PM |
JF.00008: Cross section measurements for $\gamma$-rays emitted in $^{86}$Kr($n, x n y p \gamma$) reactions N. Fotiades, M. Devlin, R.O. Nelson, T. Granier Absolute partial cross sections for production of discrete $\gamma$-rays using $^{86}$Kr($n, x n y p \gamma$) reactions with $x \leq 5$ and $y \leq 1$ in a total of 8 reaction channels were measured. The data were taken using the GEANIE spectrometer comprised of 20 high-purity Ge detectors with BGO escape-suppression shields. The broad-spectrum pulsed neutron beam of the Los Alamos Neutron Science Center's (LANSCE) WNR facility provided neutrons over a wide energy range. The time-of-flight technique was used to determine the incident neutron energies. Partial $\gamma$-ray cross sections have been measured for a total of 35 $\gamma$-rays and for neutron energies 1~MeV$< E_{n} <$100~MeV. Ten transitions were observed for the first time and were assigned to $^{86}$Kr as deexciting five previously known levels, among them the second and third 0$^{+}$ states, and one new level. All previously known levels of $^{86}$Kr with excitation energy up to 3.7~MeV were identified, and the new level was observed at 2917-keV excitation energy. Predictions from shell model calculations are compared with the data. Parts of these results were recently published in reference: N. Fotiades {\it et al.}, Phys. Rev. C {\bf 87}, 044336 (2013). [Preview Abstract] |
Friday, October 25, 2013 12:06PM - 12:18PM |
JF.00009: The Atomic Mass Evaluation (AME2012): Status and Perspectives F.G. Kondev, G. Audi, M. Wang, X. Xu, A.H. Wapstra, M. MacCormick, B. Pfeiffer The atomic mass is a fundamental property of the nucleus that has wide applications in natural sciences and technology. The new evaluated mass table, AME2012, has been recently published as a collaborative effort between scientists from China, Europe and USA, under the leadership of G. Audi. It represents a significant update of the previous AME2003 evaluation by considering a large number of precise experimental results obtained at existing Penning Trap and Storage Ring facilities, thus expending the region of experimentally known masses towards exotic neutron- and proton-rich nuclei. Since the presence of isomers plays an important role in determining the masses of many nuclei, a complementary database, NUBASE2012, that contains the isomer-level properties for all nuclei was also developed. This presentation will briefly review recent achievements of the collaboration, present on-going activities, and reflect on ideas for future developments and challenges in the field of evaluation of atomic masses. [Preview Abstract] |
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