Bulletin of the American Physical Society
9th Annual Meeting of the Northwest Section of the APS
Volume 52, Number 6
Thursday–Saturday, May 17–19, 2007; Pocatello, Idaho
Session B2: Nuclear Physics |
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Chair: Dan Dale, Idaho State University Room: PSUB Bear River Room |
Friday, May 18, 2007 2:00PM - 2:36PM |
B2.00001: Recent Advances in Our Understanding of Nuclear Forces Invited Speaker: The attempts to find the right (underlying) theory for the nuclear force have a long and stimulating history. Already in 1953, Hans Bethe stated that ``more man-hours have been given to this problem than to any other scientific question in the history of mankind.'' In search for the nature of the nuclear force, the idea of sub-nuclear particles was created which, eventually, generated the field of particle physics. I will review this productive history of hope, error, and desperation. Finally, I will discuss recent ideas which apply the concept of an effective field theory to low-energy QCD. There are indications that this concept may provide the right framework to properly understand the nuclear force. [Preview Abstract] |
Friday, May 18, 2007 2:36PM - 3:12PM |
B2.00002: The Importance of Polarization Observables in Extracting Baryon Resonances: The NSTAR Program at Jefferson Lab using Polarized Photon Beams and Polarized Targets Invited Speaker: I shall report on the NSTAR program in Hall B of Jefferson Lab on using polarization observables as an incisive tool for extracting baryon resonances. The scientific purpose of this program is to improve the understanding of the underlying symmetry of the quark degrees of freedom in the nucleon, the nature of the parity exchange between the incident photon and the target nucleon, and the mechanism of associated strangeness production in electromagnetic reactions. With the high-quality beam of the tagged and collimated of circularly- and linearly- polarized photons onto unpolarized and polarized proton and deuterium targets, and coupled with the nearly complete angular coverage of the Hall-B spectrometer, we will extract the differential cross sections and polarization observables for the photoproduction of vector mesons and kaons at photon energies ranging between 1.1 and 2.1 GeV. [Preview Abstract] |
Friday, May 18, 2007 3:12PM - 3:30PM |
B2.00003: Coffee Break
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Friday, May 18, 2007 3:30PM - 3:42PM |
B2.00004: What can we learn from microscopic studies of dense nuclear matter? Francesca Sammarruca Recent efforts in my group have been aimed at exploring nuclear interactions in the medium through a broad spectrum of microscopic theoretical studies of the properties of dense and strongly asymmetric nuclear matter, where asymmetry may refer to isospin and/or spin. An example is the possible existence of a transition to a ferromagnetic state in spin-polarized nuclear/neutron matter. I will present and discuss recent progress and its relevance with respect to a better understanding of the nuclear force in dense matter. [Preview Abstract] |
Friday, May 18, 2007 3:42PM - 3:54PM |
B2.00005: $\phi$-meson Photoproduction By Using a Beam of Linearly-Polarized Photons Julian Salamanca, Philip Cole The observables afforded by linearly-polarized photons provide the necessary means towards delineating the contributions of the various hadronic processes, which give rise to vector meson photoproduction. And in particular, We shall describe how $\phi$ meson production affords an incisive tool for exploring the nature of the parity exchange at threshold energies, the strangeness content of proton, as well as extracting signatures for the violation of Okubo-Zweig-Iizuka observation (OZI rule). Our goal will be measure the $\vec{\gamma} p \rightarrow \phi p $ reaction, with $\phi \rightarrow K^{+}K^{-}$, in the photon energy range of 1.7G to 2.1 GeV by using the Coherent Linear Bremsstrahlung Facility in Hall B of Jefferson Laboratory (Newport News, VA). The data were collected during the g8b run in the summer of 2005. [Preview Abstract] |
Friday, May 18, 2007 3:54PM - 4:06PM |
B2.00006: Field desorption as the basis for a neutron generator ion source David Chichester, Kristin Hertz, Paul Schwoebel, Chris Holland, John Brainard Compact accelerator neutron generators used in research and industry rely upon the creation of a plasma to generate deuterium and/or tritium ion beam beams. As an alternative, research is currently underway to examine the feasibility of using a plasma-free ion source using field desorption as the ion generation mechanism. Making use of standard MEMS manufacturing techniques in conjunction with new design innovations, we are developing silicon field desorption micro arrays which incorporate metallic nano-emitter tips capable of desorbing hydrogen species ions under extreme electric fields. Research is underway to understand the field desorption characteristics of these arrays and assess their applicability for use within sealed neutron tubes. This presentation will briefly describe the technology and illustrate it's potential for use in neutron generators. [Preview Abstract] |
Friday, May 18, 2007 4:06PM - 4:18PM |
B2.00007: Using Thin Films to Rapidly Screen Potential Scintillators Brian Milbrath, Jac Caggiano, Dean Matson, Larry Olsen Growing crystals of inorganic scintillators is a time-consuming and expensive process, slowing the discovery of new radiation detection materials. To that end, we have begun an investigative program to discern the usefulness of thin polycrystalline films for scintillator characterization. As a first step, we made 10 micron thick films of Eu-doped CaF$_{2}$ by electron beam deposition, which took approximately 1.5 hours per sample. After confirming composition with XPS and crystal structure with GIXRD, photoluminescence measurements were performed and found to be in agreement with literature values. Photopeak comparisons can be performed using alpha sources. The method provides a quick way to explore and optimize the proper dopant amount. The crystal structure of the thin films results in grain sizes of approximately 15 nm. Light yields were approximately 10{\%} of those found in commercial, single-crystal materials. Recently, we have begun to make thin Ce halide films. Rare-earth halide scintillators are an area of much current activity due to the favorable energy resolutions and light yields some of them possess. Preliminary results from our Ce halide studies will be presented along with our CaF$_{2}$(Eu) results. [Preview Abstract] |
Friday, May 18, 2007 4:18PM - 4:30PM |
B2.00008: Monte Carlo Simulation of a 12 MeV Cargo Container Inspection System Ibrahim Ozcan, Katherine Chandler, Randy Spaulding, Eduardo Farfan After the terrorist events of 9/11, border security has become one of the most important issues in national security due to the large number of cargo containers entering the country. Screening of all cargo containers for nuclear materials should be performed during border inspections. The technical aspects of inspecting cargo containers using electron accelerators have been studied previously. However, the radiological protection aspects involved in these studies have not been fully considered. This screening process may accidentally harm operators, workers, and bystanders; as well as stowaways hiding inside the containers. In this research project, external doses were estimated at various locations near the inspection system. A 12-MeV linear accelerator (LINAC) was used in the experiment. The relationship between the various locations and doses were determined in this simulation. The simulation was performed using MCNPX. [Preview Abstract] |
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