Bulletin of the American Physical Society
2007 APS April Meeting
Volume 52, Number 3
Saturday–Tuesday, April 14–17, 2007; Jacksonville, Florida
Session C16: Nuclear Instrumentation I |
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Sponsoring Units: DNP Chair: Werner Tornow, Duke University/TUNL Room: Hyatt Regency Jacksonville Riverfront City Terrace 12 |
Saturday, April 14, 2007 1:30PM - 1:42PM |
C16.00001: Qweak Main Detector Status David Mack The Qweak experiment at Jefferson Laboratory will make the first measurement of the weak charge of the proton. Because this electroweak observable is suppressed in the Standard Model, the modest projected 4\% uncertainty will still allow us to constrain new electron-quark interactions at the multi TeV-scale. The weak charge is accessed through the small ($<$ 1 ppm), parity-violating asymmetry in the elastic scattering of longitudinally polarized electrons from unpolarized protons. Scattered electrons which pass through fused silica bars emit Cerenkov light which is collected and converted to current by phototubes. The status of procurements and R\&D will be summarized. We are on-track for completion by September 2008 and installation in Spring 2009. [Preview Abstract] |
Saturday, April 14, 2007 1:42PM - 1:54PM |
C16.00002: The Ultracold Neutron Source at Los Alamos National Lab M. Makela, G. Hogan, C.L . Morris, A. Saunders, S. Seestrom, T.M. Ito, R. Rios, R. Mammei, R.B. Vogelaar, H.O. Back, L. Broussard, A. Holley, R. Pattie, A.R. Young The Ultracold Neutron (UCN) source at Los Alamos National Lab (LANL) has completed a second run cycle of operation. In the LANL UCN source spallation neutrons are cooled in a moderator then down scattered in solid deuterium (via a super thermal process) to UCN temperatures (1-4 mK). The UCN reach experiments after passing through 8 meters of guide. During the 2006 run cycle several changes were made to the source and guide system. This talk will give an overview of the LANL UCN source, its current status and results from source test runs during the 2006 run cycle. [Preview Abstract] |
Saturday, April 14, 2007 1:54PM - 2:06PM |
C16.00003: On Production and Optimization of Hybrid Spin Exchange Optical Pumping Polarized $\mathrm{^3He}$ Targets Peter Dolph, Karen Mooney, Gordon Cates, Vladimir Nelyubin, Jaideep Singh, William Tobias Hybrid spin exchange optical pumping consistently outperforms pure alkali SEOP. Hybrid cells contain an alloy of potassium and a small amount of rubidium, whereas conventional cells contain a single species of metal, typically Rb. K-$\mathrm{^3He}$ spin exchange is more efficient than Rb-$\mathrm{^3He}$. Consequently, less laser power is required to achieve a higher noble gas polarization with the benefit of a shorter polarization buildup time. The hybrid technique has been successfully employed in the large scale production of target cells for use in nuclear physics experiments and shows great potential for use in medical imaging. The production of hybrid alloys, optimization, and results will be discussed. [Preview Abstract] |
Saturday, April 14, 2007 2:06PM - 2:18PM |
C16.00004: Polarization Enhancement of $^{129}$Xe in TEMPO-Doped Xenon at 2.0K and 0.31 Tesla. D.N. Balakishiyeva, J.W. McNabb, C. Bednarski-Meinke, A. Honig Enhancements of $^{129}$Xe NMR signals up to 300 times their equilibrium value at temperature 2.0K and magnetic field $\sim $ 0.3T, corresponding to a spin polarization $>$1{\%}, have been obtained in solid xenon with TEMPO$^{1}$ impurity concentrations near 10$^{18}$ /cm$^{3}$. This dynamic polarization results from interaction of the nuclear Zeeman spin reservoir with the electron spin-spin reservoir$^{2}$, while irradiating near the electron Zeeman resonance frequency ($\sim $8.7 GHz) with up to 500 mW of microwave power. The mixing procedures in which TEMPO is introduced into liquid Xenon prior to freezing, and the \textit{electron} spin resonance line shapes which correlate with dynamic polarization enhancements are described. At higher magnetic fields up to $\sim $5 T, and temperatures still within the 1 - 2K range, the results suggest a route for fast and copious production of hyperpolarized $^{129}$Xe, with its multitude of applications$^{3}$. 1. Pluckthun, M. et al, Nucl. Instrum. and Meth. in Phys. Res. A \underline {400}, 122 (1997). 2. Abragam, A. and M. Goldman, Rep. Prog. Phys. \underline {41}, 395 (1978). 3. Oros, A-M and N. J. Shah, Phys. Med. Biol. \underline {49}, R105 (2004). [Preview Abstract] |
Saturday, April 14, 2007 2:18PM - 2:30PM |
C16.00005: High Resolution Isobar Separator for Study of Exotic Decays V. Shchepunov, A. Piechaczek, H.K. Carter, E.F. Zganjar, J. Batchelder, S.N. Liddick, H. Wollnik, Y. Hu A Multi-pass Time-Of-Flight mass spectrometer and separator (MTOF) was designed and built by the UNIRIB Consortium. The MTOF spectrometer consists of two coaxial electrostatic mirrors and auxiliary focusing, injection, and extraction elements. Ions of different mass are reflected multiple times between the mirrors and separated longitudinally. Using a test ion source, a mass resolving power of 29,000 (FWHM) has been achieved. The agreement between simulated and measured properties of the MTOF spectrometer is very good. MTOF will be converted into a mass separator by adding a fast electrostatic switch of the Bradbury-Nielson type. It will be initially coupled to the online isotope separator, UNISOR, at HRIBF to provide isobaric pure samples of exotic species in the $^{100}$Sn region or neutron-rich nuclei for decay studies. Our ion optic calculations indicate a mass resolving power $\ge $ 15,000 and efficiencies of 30-50{\%}. Ion optic design principles and hardware specifications from numerical simulations will be presented. The proposed RIB injection with beam cooling and bunching from the UNISOR separator into this new, compact isobar separator will be described. [Preview Abstract] |
Saturday, April 14, 2007 2:30PM - 2:42PM |
C16.00006: Use of the GEANT4 code in precise measurements of $\beta^+$-branching-ratios V.V. Golovko, V.E. Iacob, J.C. Hardy In order to determine the vector coupling constant and to test the unitarity of the Cabibbo-Kobayashi-Maskawa matrix one has to make precise measurements of nuclear masses, $\beta$-branching ratios and halflives~[1]. The measurements of halflives and branching ratios are performed in a simple, but very precise counting station at our institute. A typical ``on-line'' branching ratio experiment consists of collection of the accelerator-produced radioactive nuclei with a tape transport station that rapidly moves the collected sample to a location between a scintillaton detector and a well-calibrated high-volume HPGe $\gamma$-detector. Data are collected with a PC station for all $\beta$-$\gamma$ coincident events. In order to completely understand all systematic effects contributing to the branching ratio measurements one must determine the relative efficiency of the scintillator as a function of $\beta$-particle energy, because the various $\gamma$-ray peaks correspond to $\beta$-transitions with different end-point energies and their observed relative intensities will be affected by the slight differences in $\beta$ detection efficiency. Previous work~[2] has reported a response function of $\beta$-particles from standard open $\beta$-sources. Here we present a comparison with measurements obtained in the ``on-line'' geometry configuration. [1] J.~C.~Hardy and I.~S.~Towner. {\em PRC}, 71(5):055501, 2005. [2] V.V.~Golovko et. al. {\em BAPS 59}, no~6, p.~DH4 83, 2006. [Preview Abstract] |
Saturday, April 14, 2007 2:42PM - 2:54PM |
C16.00007: Digital data acquisition setup for ${\beta}$-gamma correlation experiment M.M. Rajabali, R. Grzywacz, S.N. Liddick, C. Bingham, I. Darby, C. Mazzocchi, K. Rykaczewski, J. Batchelder, T. Baumann, T. Ginter, P. Mantica, M. Karny, K. Miernik, M. Pfutzner, S.V. Ilyushkin, J.A. Wagner, W. Krolas A new-generation digital signal processing-based acquisition setup has been successfully tested and used in an on-line experiment at the NSCL at MSU. The acquisition system is based on the new Pixie16 boards from XIA. The detection setup consisted of the SeGA array and silicon detectors. All the signals were read out through the Pixie16 boards. Details of the set-up and results from the test will be given. [Preview Abstract] |
Saturday, April 14, 2007 2:54PM - 3:06PM |
C16.00008: Reducing neutron backgrounds in dark matter detectors with doped water shields Kareem Kazkaz, Adam Bernstein, Bob Svoboda, Steve Dazeley Neutrons can create false positives in next-generation, low-background Weakly Interacting Massive Particle (WIMP) dark matter detectors via elastic scatters from target nuclei. There is a need to reduce and/or tag both internal and environmental neutrons, thereby allowing event-by-event rejection of these backgrounds. One approach to performing both tasks is to submerge the detector in an active water shield, which may thermalize and capture background neutrons. The resulting neutron capture gamma cascade can produce Cherenkov light that may be observed using photomultiplier tubes, providing a veto signal. By doping the water with certain neutrophage elements, the light output can be significantly increased, leading to greater sensitivity and improved suppression of related backgrounds. We present an analysis of adding neutron-absorbing dopants to an active water shield for LUX, a proposed WIMP detector, and discuss follow-on applications. This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under contract No. W-7405-ENG-48. UCRL-ABS-227279. [Preview Abstract] |
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