Bulletin of the American Physical Society
2011 Fall Meeting of the APS Division of Nuclear Physics
Volume 56, Number 12
Wednesday–Saturday, October 26–29, 2011; East Lansing, Michigan
Session HF: Nuclear Structure V |
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Chair: Steven Yates, University of Kentucky Room: 104AB |
Friday, October 28, 2011 10:30AM - 10:42AM |
HF.00001: The polariser beamline at TRIUMF for nuclear structure physics A. Voss, M.R. Pearson, C.D.P. Levy, J. Billowes, F. Buchinger, K.H. Chow, J.E. Crawford, M.D. Hossein, R.F. Kiefl, W.A. MacFarlane, E. Man\'e, G.D. Morris, T.J. Parolin, H. Saadaoui, Z. Salman, O.T.J. Shelbaya, M. Smadella, Q. Song, D. Wang Originally built to provide polarised ion beams for condensed matter experiments, the polariser beamline at TRIUMF is coupled to both beta-NMR and beta-NQR spectrometers. In addition, the beam can be passed through a radio-frequency quadrupole cooler and buncher (RFQ) providing bunched beams. Recently, a laser spectroscopy and beta-NQR program was started to investigate the ground state structure of exotic nuclei. Results from recent experiments including zero-field beta-NQR studies to determine the quadrupole moment of the halo nucleus Li-11 and laser spectroscopy to determine the charge radius of Rb-74. [Preview Abstract] |
Friday, October 28, 2011 10:42AM - 10:54AM |
HF.00002: Precision Neutron Scattering Length Measurements with Neutron Interferometry M.G. Huber, M. Arif, D.L. Jacobson, D.A. Pushin, M.O. Abutaleb, C.B. Shahi, F.E. Wietfeldt, T.C. Black Since its inception, single-crystal neutron interferometry has often been utilized for precise neutron scattering length, $b$, measurements. Scattering length data of light nuclei is particularly important in the study of few nucleon interactions as $b$ can be predicted by two + three nucleon interaction (NI) models. As such they provide a critical test of the accuracy 2+3 NI models. Nuclear effective field theories also make use of light nuclei $b$ in parameterizing mean-field behavior. The NIST neutron interferometer and optics facility has measured $b$ to less than 0.8\% relative uncertainty in polarized $^3$He and to less than 0.1\% relative uncertainty in H, D, and unpolarized $^3$He. A neutron interferometer consists of a perfect silicon crystal machined such that there are three separate blades on a common base. Neutrons are Bragg diffracted in the blades to produce two spatially separate (yet coherent) beam paths much like an optical Mach-Zehnder interferometer. A gas sample placed in one of the beam paths of the interferometer causes a phase difference between the two paths which is proportional to $b$. This talk will focus on the latest scattering length measurement for n-$^4$He which ran at NIST in Fall/Winter 2010 and is currently being analyzed. [Preview Abstract] |
Friday, October 28, 2011 10:54AM - 11:06AM |
HF.00003: High-Performance Algorithm for Calculating Non-Spurious Nuclear Level Densities Roman Senkov, Mihai Horoi, Jagjeet Kaur, Vladimir Zelevinsky A new high-performance algorithm was recently proposed for calculating spin- and parity-dependent shell model nuclear level densities using methods of statistical spectroscopy in the proton-neutron formalism. When used in valence spaces that cover more than one major harmonic oscillator shell, this algorithm mixes the genuine intrinsic states with spurious center-of-mass excitations. We construct an advanced algorithm based on the method of statistical moments that eliminates the spurious states. Results for states of unnatural parity in several $sd$-shell nuclei are presented and compared with exact shell model calculations and experimental data. The new algorithm is applied to calculation of reaction rates for nuclei on the $rp$-process path. [Preview Abstract] |
Friday, October 28, 2011 11:06AM - 11:18AM |
HF.00004: An algorithm for the removal of spurious states and calculations of nuclear level densities Jagjeet Kaur, Mihai Horoi, Roman Senkov An algorithm was developed for the calculation of nuclear level densities in proton-neutron formalism using the moments method. This method was further improved to discard the contributions of spurious states related to the center-of-mass excitations. We present nuclear level densities for some nuclei in comparison with the shell model calculations and experimental data. Applications of this algorithm such as calculations of the reaction rates for the nuclei in the $rp$-process will be also presented. [Preview Abstract] |
Friday, October 28, 2011 11:18AM - 11:30AM |
HF.00005: Simulations of the HRIBF Modular Total Absorption Spectrometer (MTAS) Charles Rasco, Marek Karney, Krzysztof Rykaczewski, Aleksandra Kuzniak, Marzena Wolinska-Cichocka, Robert Grzywacz We will present calculations of the simulated performance of the MTAS detector at the Holifield Radioactive Ion Beam Facility (HRIBF) at Oak Ridge National Laboratory. The total absorption gamma spectra measured with MTAS will be used to derive improved beta-feeding patterns and the resulting beta strength functions for fission products. In particular, measurements of decay heat released by radioactive nuclei produced in nuclear fuels at power reactors will be performed. The MTAS is made up of 19 large NaI(Tl) hexagonal detectors and this geometry was simulated using the GEANT4 toolkit. The energy resolution depends crucially on the nonlinearity response of the optical light production of the NaI crystals. We developed a light production curve based on the dE/dx of the electrons generated by all incoming particles and this curve was used to generate the amount of light produced independent of the incoming particle type. Simulation results of the energy resolution compared with several measurements will be presented. [Preview Abstract] |
Friday, October 28, 2011 11:30AM - 11:42AM |
HF.00006: Progress towards the search for the permanent electric dipole moment of Ra-225 Jaideep Singh, Kevin Bailey, Matt R. Dietrich, John P. Greene, Roy J. Holt, Mukut R. Kalita, Wolfgang Korsch, Zheng-Tian Lu, Peter Mueller, Tom P. O'Connor, Richard H. Parker, Ibrahim A. Sulai We are searching for the permanent electric dipole moment (EDM) of Radium-225. In this context, a nonzero EDM is a signature of time-reversal-symmetry violating interactions within nuclei. The Ra-225 radioisotope (half-life of 15 days) is an attractive choice because, due to its unusually large nuclear deformations, it is expected to be an extraordinarily sensitive probe to these types of interactions. In our measurement scheme, Ra atoms are first laser-cooled \& -trapped in a magneto-optical trap. Subsequently they are transferred into an optical dipole trap, which is used to transport the atoms into the science chamber. Finally, the atoms are transferred into a more stable \& confining optical dipole trap, where the measurement takes place. The first two steps have already been demonstrated. We will report on progress towards measurements of atomic properties necessary for the EDM search and the EDM search itself. This work is supported by DOE, Office of Nuclear Physics, under contract No. DE-AC02-06CH11357. [Preview Abstract] |
Friday, October 28, 2011 11:42AM - 11:54AM |
HF.00007: Challenges and opportunities in the search for electric dipole moment (EDM) in $^{225}$Ra atom Mukut Ranjan Kalita, Kevin Bailey, Matthew Dietrich, John Greene, Roy Holt, Wolfgang Korsch, Zheng-tian Lu, Peter Mueller, Thomas O'connor, Richard Parker, Ibrahim Sulai, Jaideep Singh The observation of a permanent electric dipole moment (EDM) in a non-degenerate system would indicate violation of time reversal symmetry. $^{225}$Ra atom is a particularly attractive candidate for this search since it has a nuclear spin I=1/2 and has a significant nuclear octupole deformation. This property increases the Schiff moment of the nucleus and therefore enhances the atomic EDM. The half life (t$_{1/2 }$=14.9 days) of $^{225}$Ra is sufficiently long to perform EDM searches. Our group has already demonstrated the trapping of laser cooled Ra atoms in a magneto-optical trap (MOT) and transferring them to a far off resonant optical dipole trap (ODT). We will discuss our recent progress on manipulation of ultra cold Ra atoms in the ODT, efforts in improving our laser systems and generation of electric and magnetic fields required for the measurement. [Preview Abstract] |
Friday, October 28, 2011 11:54AM - 12:06PM |
HF.00008: Behavioral Study of Magnetization of Super-mirror Sample Gretchen Phelps, Mukut Kalita, Wolfgang Korsch The surface magneto-optic Kerr effect (SMOKE) refers to the phenomenon in which the polarization of light reflected from a magnetized surface is rotated, the magnitude of which is proportional to the magnetization of the surface. Using SMOKE we are able to extract the Kerr rotation $\theta_{K}$ and Kerr ellipticity $\epsilon_{K}$ of an FeCoV/TiN super-mirror, and non-magnetic samples. A comparison between these results is utilized to study the temporal behavior of the magnetization of the super- mirror sample. Our set-up incorporates a modulation technique, which allows for phase sensitive detection through lock-in amplifiers. Currently our sensitivity is at the $\mu$rad level. This study is part of the Oak Ridge National Lab nEDM Collaboration which plans to improve the present limit on the permanent electric dipole moment of the neutron by up to two orders of magnitude. The experiment will utilize magnetic super-mirrors to both polarize and guide neutrons. Preliminary analysis comparing results obtained from a magnetized super-mirror and non-magnetic samples will be presented. [Preview Abstract] |
Friday, October 28, 2011 12:06PM - 12:18PM |
HF.00009: Reconciliation of Values for Bohr Radius and Empirical Radius of H-Atom Using Nuclear Vibration Factor Stewart Brekke The value for the calculated H-atom radius, the Bohr value, is $5.29x10^{-11} m$ and the empirical value for that radius has been found to be $2.5x10^{-11} m$. Since the nucleus is vibrating, the distance relation, d, between the nucleus and the electron is $r + Acos2\pi ft = d$, due to a slight lag time between nuclear vibration and orbiting electron repeatedly changing the distance between the vibrating nucleus and the electron. Therefore, the distance between vibrating nucleus and orbiting electron must only be an average distance. The average value for the cosine is the RMS value of 0.707. Substituting the calculated distance for r and the empirical distance for d, the equation becomes $5.29x10{^-11} m + (0.707)A = 2.5x10^{-11} m$. Solving for the average amplitude of nuclear vibration, A, $A=3.95x 10^{-11} m$. [Preview Abstract] |
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