Bulletin of the American Physical Society
11th Annual Meeting of the Northwest Section of APS
Volume 54, Number 6
Thursday–Saturday, May 14–16, 2009; Vancouver, BC, Canada
Session B4: Nuclear Physics |
Hide Abstracts |
Chair: Francesca Sammarruca, University of Idaho Room: Irving Barber Learning Center 260 |
Friday, May 15, 2009 1:00PM - 1:36PM |
B4.00001: Journey to the Center of the Neutron Invited Speaker: The meaning of model-independent transverse charge densities derived from measured electromagnetic form factors is discussed. The use of experimental data for the neutron electromagnetic form factors led to the finding that the central density of the neutron is negative, in contrast with the expectations of many that it is positive. An explanation for this is presented by using data for deep inelastic scattering to interpret the elastic form factor data via the Drell-Yan-West relation. Current experimental data indicate that the negatively charged $d$ quark dominates the neutron structure function at large values of Bjorken $x$, where the large longitudinal momentum of the struck quark determines center-of-momentum of the system, and thus the center of the neutron. Thus the center of the neutron is occupied mainly by $d$ quarks. [Preview Abstract] |
Friday, May 15, 2009 1:36PM - 1:48PM |
B4.00002: The missing three-nucleon forces: Where are they? Ruprecht Machleidt In recent years, there has been substantial progress in the derivation of nuclear forces from chiral effective field theory. Accurate two-nucleon forces (2NF) have been constructed up to next-to-next-to-next-to-leading order (N3LO) and applied with a fair amount of success. However, chiral three-nucleon forces (3NF) have been used only at N2LO, improving some microscopic predictions, but leaving also several issues, like the ``A$_{\rm y}$ puzzle'', unresolved. Thus, the 3NF at N3LO is needed for essentially two reasons: for consistency with the 2NF and to (hopefully) improve some critical predictions. I will summarize the current status of the derivation of the 3NF at N3LO and discuss the expectations of their impact on ab initio calculations. [Preview Abstract] |
Friday, May 15, 2009 1:48PM - 2:00PM |
B4.00003: Towards the determination of nuclear matrix elements for $2\nu\beta\beta$ decays at TRIUMF's TITAN facility Thomas Brunner, Maxime Brodeur, Stephan Ettenauer, Alain Lapierre, Ryan Ringle, Jens Dilling To unveil the neutrino's mystery, sensitive experiments in underground laboratories are presently searching for $0\nu\beta\beta$ decay. If this decay was observed, the effective neutrino mass could be derived from its half-life and a complex nuclear matrix element. This later is entirely based on theoretical calculations with guidance from $2\nu\beta\beta$-decay matrix elements deduced from experimental data. Unfortunately, such elements often disagree from those of single $\beta$-decays. Measuring electron capture branching ratios (EC-BR) of odd-odd intermediate transition nuclei in $\beta\beta$-decays represents an independent approach to determine $2\nu\beta\beta$ matrix elements. A new technique for measuring these EC-BRs is being developed at the TRIUMF's Ion Trap system for Atomic and Nuclear physics (TITAN), using at the heart of the experiment an open access Penning ion trap. I will present this new method and the results of a proof-of-principle experiment carried out recently with $In^{107}$ which shows its feasibility. [Preview Abstract] |
Friday, May 15, 2009 2:00PM - 2:12PM |
B4.00004: Probing the Neutrino Mass Hierarchy Laura Bodine, R.G. Hamish Robertson The field of neutrino physics is beginning to address many questions posed by previous experiments. Current and next generation experiments will examine the value of $\theta_{13}$, the absolute neutrino mass scale and the nature of massive neutrinos. Yet, even in the wake of these developments, the neutrino mass hierarchy remains unknown. The most promising proposed method for determining the neutrino mass hierarchy, namely the use of matter enhancement, critically relies on a non-vanishing $\theta_{13}$. We discuss the prospects of examining $\nu_\mu$ disappearance over a very long baseline (for example: FNAL to the South Pole) as an alternative method that remains feasible even in the limit of a vanishing $\theta_{13}$. [Preview Abstract] |
Friday, May 15, 2009 2:12PM - 2:24PM |
B4.00005: Tensor interaction constraints from $\beta$ decay daughter nucleus spin asymmetry of trapped atoms J.A. Behr, J.R.A. Pitcairn, D. Roberge, O. Aviv, D. Ashery, A. Gorelov, P.G. Bricault, M. Dombsky, J.D. Holt, K.P. Jackson, B. Lee, M.R. Pearson, A. Gaudin, B. Dej, C. H\"ohr, G. Gwinner, D. Melconian Parity violation was discovered in 1957 in $\beta$ decay by measuring the asymmetry of electron emission with respect to the nuclear spin. Other observables besides this $\beta$ asymmetry were immediately proposed. Treiman realized that the asymmetry of emission of the daughter nuclei would be the sum of $\beta$ and $\nu$ asymmetries, and that for decays that change nuclear spin it would vanish for some types of weak interactions, making it a sensitive probe of other types. But the low-energy daughter nuclei would stop in a few atomic layers of material, making direct detection difficult. We have used laser trap technology to measure Treiman's observable. The nuclear recoils escape the laser trap, and we were able to measure their emission asymmetry to percent accuracy. The result is consistent with zero as predicted in the modern electroweak model, and constrains a certain type of interaction (`tensor') complementary to other experiments. [Preview Abstract] |
Friday, May 15, 2009 2:24PM - 2:38PM |
B4.00006: BREAK
|
Friday, May 15, 2009 2:38PM - 3:14PM |
B4.00007: Production of the heaviest elements using radioactive beams Invited Speaker: Previously we have evaluated quantitatively the prospects for the synthesis of transactinide nuclei using radioactive beams (PRC {\bf 76}, 014612 (2007)). We have revised these calculations to include current approaches to properly deal with the excitation energy dependence of shell and pairing corrections along with recent experimental advances in our understanding of the fusion probability, P$_{CN}$ and the capture cross sections for very neutron-rich systems and the expected beam intensities at FRIB. Using our simple formalism for calculating the complete fusion cross sections that reproduces the known heavy element production cross sections over six orders of magnitude, we calculate the production rates for transactinide nuclei with Z $\leq$ 120. All possible projectile and target combinations are evaluated. Exciting new possibilities for studies of the atomic physics, chemistry and nuclear spectroscopy of the heaviest elements should be realized at a modern radioactive beam facility. Examples of possible experiments at pre-FRIB facilities will be discussed. The synthesis of new heavy elements is best undertaken at stable beam accelerators. [Preview Abstract] |
Friday, May 15, 2009 3:14PM - 3:26PM |
B4.00008: High Precision Mass Measurements of Radioactive Highly Charged Ions at TITAN / TRIUMF for Tests of Fundamental Symmetries and Nuclear Structure Studies Stephan Ettenauer, Thomas Brunner, Maxime Brodeur, Aaron Gallant, Alain Lapierre, Ryan Ringle, Melvin Good, Paul Delheij, Gerald Gwinner, David Lunney, Jens Dilling Nuclear structure studies as well as tests of fundamental symmetries with nuclear systems such as the verification of unitarity of the CKM matrix require precise knowledge of masses of radioactive nuclei. The most recent development to extend the present limit in precision is to use highly charged ions (HCI) for mass determination in Penning traps. After successful measurements of singly charged exotic nuclei TRIUMF's Ion Trap for Atomic and Nuclear Science (TITAN) is preparing mass measurements of radioactive nuclei by using HCI as the only facility in the world: Singly charged ions will be charge-bred in TITAN's Electron Beam Ion Trap (EBIT) before they are transferred into the measurement Penning trap. First successful tests on stable HCI produced by the EBIT will be presented as well as plans for measurements of radioactive HCI to be performed later this year. [Preview Abstract] |
Friday, May 15, 2009 3:26PM - 3:38PM |
B4.00009: Penning Trap Experiments with the Most Exotic Nuclei on Earth: Precision Mass Measurements of Halo Nuclei M. Brodeur, T. Brunner, S. Ettenauer, A. Lapierre, R. Ringle, P. Delheij, J. Dilling Exotic nuclei are characterized with an extremely unbalanced protons-neutrons ratio ($p$/$n$) where for instance, the halo isotopes of He and Li have up to 3X more $n$ than $p$ (compared to $p$/$n$ = 1 in $^{12}$C). The properties of these exotic halo nuclei have long been recognized as the most stringent tests of our understanding of the strong force. $^{11}$Li belongs to a special category of halos called Borromean, bound as a three-body family, while the two-body siblings, $^{10}$Li and 2 $n$, are unbound as separate entities. Last year, a first mass measurement of the radioisotope $^{11}$Li using a Penning trap spectrometer was carried out at the TITAN (Triumf's Ion Trap for Atomic and Nuclear science) facility at TRIUMF-ISAC. Penning traps are proven to be the most precise device to make mass measurements, yet until now they were unable to reach these nuclei. At TRIUMF we managed to measure the mass of $^{11}$Li to an unprecedented precision of $dm/m$ = 60 ppb, which is remarkable since it has a half-life of only 8.8 ms which it the shortest-lived nuclide to be measured with this technique. Furthermore, new and improved masses for the 2 and 4 $n$ halo $^{6,8}$He, as well has the 1 $n$ halo $^{11}$Be have been performed. An overview of the TITAN mass measurement program and its impact in understanding the most exotic nuclei will be given. [Preview Abstract] |
Friday, May 15, 2009 3:38PM - 3:50PM |
B4.00010: Beam delivery at TRIUMF's ISAC facility Colin Morton The ISAC facility at TRIUMF is arguably the world's premier rare-isotope beam facility. Exotic nuclei are produced by impinging 500 MeV protons from TRIUMF's main cyclotron on a thick target at currents of up to 100 $\mu$A. The resulting radioactive heavy-ion beams are delivered to a number of experimental areas, either at low energy or reaccelerated to energies of up to 5 MeV/nucleon, and drive research programs in nuclear physics and astrophysics, fundamental symmetries, and materials science. An overview of beam delivery at ISAC, and the future direction of the facility, will be presented. [Preview Abstract] |
Friday, May 15, 2009 3:50PM - 4:02PM |
B4.00011: The Use of Thermal Neutron Fission for Isotope Enrichment Jennifer Farley, Ernest Nieschmidt, Shane Hough The world has many applications for elements enriched in a particular isotope. These find application in medicine, nanostructures, electronics, process control and all forms of research. Some degree of enrichment compared to that provided by natural abundance is supplied by fission products produced by the various forms of fissile and fertile materials. Examples are given of U-235 thermal neutron fission. The most used medical isotope is Tc-99m, produced by Mo-99 beta decay; Mo has seven stable isotopes. In the fission product distribution Mo-92 and Mo-94 are absent and the grandparent of Mo-96 has a half-life of 10$^{19}$ years. These three isotopes represent 41{\%} of natural Mo; consequently the remaining Mo isotopes produced in fission are considerably enriched. This would provide good feed material for further enrichment by any applicable enrichment technique. [Preview Abstract] |
Friday, May 15, 2009 4:02PM - 4:14PM |
B4.00012: Application of core shell iron-iron oxide and pure iron oxide magnetic nanoparticles in nuclear waste separation technology M. Kaur T. Singh, H. Han, Y. Qiang, A. Johnson, A. Paszczynski Based on a review of recent development of nuclear waste separation technology, we have developed a nanomagnetic separation method that uses specific actinide chelators conjugated with magnetic nanoparticles (MNPs). This separation method has two main advantages: 1) high efficiency in separating actinides and less amount of secondary waste generation comparing with conventional processes; and 2) the resulting complex of MNP- chelators-actinide is easily manipulated in solutions using magnetic field. The core shell MNPs of size about 15 nm were produced by a cluster source at 200 W. The core shell MNP has high magnetization ($\sim $150 emu/g) compared to commercial iron oxide nanoparticles ($\sim $40 emu/g). Due to high magnetic moment of core shell MNPs, it is easier and faster to separate actinides from nuclear waste solutions. The magnetic properties of all MNPs were studied and characterized using vibrating sample magnetometer before and after coating and attachment of the ligand. [Preview Abstract] |
Friday, May 15, 2009 4:14PM - 4:26PM |
B4.00013: Dispersion and Aggregation of Magnetic Nanoparticles for Nuclear Waste Separation H. Han, M. Kaur T. Singh, Y. Qiang, A. Johnson, A. Paszczynski A novel method of nuclear waste separation using conjugates of actinide chelators and magnetic nanoparticles (MNPs) is developed. The fast separation can be facilitated by the high magnetic moments of core-shell MNPs. Highly uniform dispersion of MNPs in solutions is required for the efficient conjugation. However, stabilization of well dispersed MNPs hinders fast magnetic collection of the conjugates. To address this dilemma, the dispersion and aggregation of the MNPs has been investigated in both mechanical and chemical approaches. In the mechanical approach, continuous ultrasonic dispersed the MNPs, whereas they re-aggregated after up to 20 minutes treatment. Bead beating method improved the MNPs' suspension time by up to two factors. Nevertheless, the magnetization of MNPs dropped sharply due to the generation of non-magnetic beads' residual. Chemical method using electrolyte and agents with different polarizations had significant effects on the suspension and aggregation of the various sized MNPs. The fine balance of Van de Waals, Brownian forces, magnetic dipole and Coulomb interactions are discussed. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700