Bulletin of the American Physical Society
APS April Meeting 2013
Volume 58, Number 4
Saturday–Tuesday, April 13–16, 2013; Denver, Colorado
Session J10: Instrumentation: Exotic Beams |
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Sponsoring Units: DNP Room: Governor's Square 12 |
Sunday, April 14, 2013 1:30PM - 1:42PM |
J10.00001: Refining signal decomposition for GRETINA detectors V.S. Prasher, C.M. Campbell, M. Cromaz, H.L. Crawford, A. Wiens, I.Y. Lee, A.O. Macchiavelli, C.J. (Kim) Lister, E. Merchan, P. Chowdhury, D.C. Radford The reconstruction of the original direction and energy of gamma rays through locating their interaction points in solid state detectors is a crucial evolving technology for nuclear physics, space science and homeland security. New arrays AGATA and GRETINA have been built for nuclear science based on highly segmented germanium crystals. The signal decomposition process fits the observed waveform from each crystal segment with a linear combination of pre-calculated basis signals. This process occurs on an event-by-event basis in real time to extract the position and energy of $\gamma$-ray interactions. The methodology for generating a basis of pulse shapes, varying according to the position of the charge generating interactions, is in place. Improvements in signal decomposition can be realized by better modeling the crystals. Specifically, a better understanding of the true impurity distributions, internal electric fields, and charge mobilities will lead to more reliable bases, more precise definition of the interaction points, and hence more reliable tracking. In this presentation we will cover the current state-of-the-art for basis generation and then discuss the sensitivity of the predicted pulse shapes when varying some key parameters. [Preview Abstract] |
Sunday, April 14, 2013 1:42PM - 1:54PM |
J10.00002: SAMURAI Time-Projection Chamber: A device for constraining the symmetry energy R. Shane, K. Andrews, J. Barney, B. Brophy, Z. Chajecki, C.F. Chan, J.W. Dunn, E. Ersoy, J. Estee, J. Gilbert, F. Lu, W.G. Lynch, M.B. Tsang, A.B. McIntosh, S.J. Yennello, S. Dye, M. ElHoussieny, M. Famiano, C. Snow, T. Isobe, H. Sakurai, A. Taketani, T. Murakami, W. Powell The SAMURAI-TPC is a time-projection chamber to be used in conjunction with the SAMURAI spectrometer at the Radioactive Isotope Beam Facility at RIKEN, Japan. It is designed to detect charged pions as well as light charged particles up to oxygen produced in heavy ion collisions. Design of the TPC is based on the EOS TPC with similar dimensions. However, the TPC will be equipped with the newly designed General Electronics for TPCs (GET). One of the proposed experimental programs using the TPC is to measure pi+/pi- ratios from heavy-ion collisions which should provide constraints on the asymmetry term in the nuclear equation of state at densities about twice saturation density. In this talk, the design and construction of the detector will be discussed. [Preview Abstract] |
Sunday, April 14, 2013 1:54PM - 2:06PM |
J10.00003: Development of a Segmented Plastic Fast Neutron Detector Sean Stave, David Jordan Pacific Northwest National Laboratory is investigating segmented fast plastic scintillators as an alternative to liquid scintillator for fast neutron detection. Fast plastic scintillator is a non-volatile material, which offers neutron/gamma ray discrimination in segmented geometry and operates at much faster rates than liquid scintillator. Liquid scintillators use pulse shape discrimination (PSD) to distinguish neutrons from gamma rays. At higher rates, the pulses can pile up making PSD more difficult. Segmented plastic scintillator could provide a factor of 50 improvement in rate handling ability. Neutrons in the 2 to 10 MeV energy range and gamma rays interact in different ways with the plastic scintillator. Modeling studies indicate that neutrons can be discriminated from gamma rays by choosing the appropriate segmentation size and maintaining the necessary time resolution. Laboratory studies have been initiated to verify the modeling predictions and a multi-segment proof-of-concept detector is in development. We present anticipated characteristics of the detector, including the neutron detection efficiency and gamma-ray rejection ratio, as well as the method for detecting the light output and digitizing the resulting signals. [Preview Abstract] |
Sunday, April 14, 2013 2:06PM - 2:18PM |
J10.00004: Boron Doped Plastic Scintillator Efficiency Adam Mahl, Pascale Chouinard-Dussault, Cory Pecinovsky, Andrew Potter, Tyler Remedes, John Dorgan, Uwe Greife This talk will describe the progress made in an interdisciplinary development project aimed at cost-effective, neutron sensitive, plastic scintillator. Colorado School of Mines researchers with backgrounds in Physics, Chemistry, and Chemical Engineering have worked on the incorporation of $^{10}$B in plastics through extrusion. First results on transparent samples using fluorescent spectroscopy and beta excitation will be presented. [Preview Abstract] |
Sunday, April 14, 2013 2:18PM - 2:30PM |
J10.00005: Offline Ion Source Developments for the BECOLA Facility at NSCL Andrew Klose, Paul Mantica, Kei Minamisono Singly-charged beams of the stable isotope(s) of K, Ca, Mn, and Fe have been produced using either a commercial plasma ion source or a home-built electron ionization source for the BEam COoler and LAser spectroscopy (BECOLA) facility at the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University. For each element, collinear laser spectroscopy was performed to confirm the presence of the respective element. Production of stable ion beams for a given element is necessary to obtain reference hyperfine spectra of species with known electromagnetic moments before such nuclear properties can be deduced from the laser hyperfine-structure measurements of rare isotopes that are planned at NSCL. The results from the commissioning tests of the plasma and electron ionization sources will be presented, and development of a new Penning Ion Gauge (PIG) ion source will be discussed. [Preview Abstract] |
Sunday, April 14, 2013 2:30PM - 2:42PM |
J10.00006: Event-by-Event Fission Modeling of Prompt Neutrons and Photons from Neutron-Induced and Spontaneous Fission with $\mathtt{FREYA}$ Ramona Vogt, Jorgen Randrup The event-by-event fission Monte Carlo code $\mathtt{FREYA}$ (Fission Reaction Event Yield Algorithm) generates large samples of complete fission events. Using $\mathtt{FREYA}$, it is possible to obtain the fission products as well as the prompt neutrons and photons emitted during the fission process, all with complete kinematic information. We can therefore extract any desired correlation observables. Concentrating on $^{239}$Pu($n$,f), $^{240}$Pu(sf) and $^{252}$Cf(sf), we compare our $\mathtt{FREYA}$ results with available data on prompt neutron and photon emission and present predictions for novel fission observables that could be measured with modern detectors. [Preview Abstract] |
Sunday, April 14, 2013 2:42PM - 2:54PM |
J10.00007: Quantitative Analysis of Various Metalloprotein Compositional Stoichiometries with Simultaneous PIXE and NRA Andrew McCubbin, Paul DeYoung, Graham Peaslee, Megan Sibley, Joshua Warner Stoichiometric characterization has been carried out on multiple metalloproteins using a combination of Ion Beam Analysis methods and a newly modified preparation technique. Particle Induced X-ray emission (PIXE) spectroscopy is a non-destructive ion beam analysis technique well suited to determine the concentrations of heavy elements. Nuclear Reaction Analysis (NRA) is a technique which measures the areal density of a thin target from scattering cross sections of 3.4 MeV protons. A combination of NRA and PIXE has been developed to provide a quantitative technique for the determination of stoichiometric metal ion ratios in metalloproteins. About one third of all proteins are metalloproteins, and most do not have well determined stoichiometric compositions for the metals they contain. Current work focuses on establishing a standard method in which to prepare protein samples. The method involves placing drops of protein solutions on aluminized polyethylene terephthalate (Mylar\textregistered) and allowing them to dry. This technique has been tested for several proteins of known stoichiometry to determine cofactor content and has proven to be a reliable analysis method, accurately determining metal stoichiometry in cytochrome c, superoxide dismutase, concanavalin A, vitamin B12, and hemoglobin. [Preview Abstract] |
Sunday, April 14, 2013 2:54PM - 3:06PM |
J10.00008: Applications of Atom Trap Trace Analysis in the Earth Sciences Z.-T. Lu, W. Jiang, K. Bailey, P. Mueller, T.P. O'Connor With the successful development of the Atom Trap Trace Analysis (ATTA) method, radiokrypton dating has become available for the first time to the Earth science community at large. This novel tool is enabling new research opportunities and improved understanding in the Earth sciences, with implications in studying climate change and in water resource management. Examples of applications of ATTA in the Earth sciences are: (1) ATTA measurements of $^{81}$Kr in the Nubian Aquifer of Africa, the Great Artesian Basin of Australia, and the Guarani Aquifer of South America have transformed our understanding of the long-term behavior of these large aquifer systems. $^{81}$Kr dating with more extensive sampling will be carried out on major aquifer systems around the world. (2) A systematic survey of $^{39}$Ar throughout the oceans, particularly when combined with $^{14}$C data, will fill major gaps in our knowledge of deep ocean circulation and mixing, and will allow more accurate predictions of oceanic sequestration of atmospheric CO$_2$. (3) The feasibility and accuracy of $^{81}$Kr dating of old ice has been tested with the well-dated stratigraphy of Taylor Glacier in Antarctica. For more information, search for ``TANGR2012''. [Preview Abstract] |
Sunday, April 14, 2013 3:06PM - 3:18PM |
J10.00009: Optimization of a Modular Neutron Detector Array for the Detection of Halo Neutron Pairs using GEANT4 David Walter, Frederic Sarazin, Duane Smalley, Sergey Ilyushkin The study of halo neutrons in light nuclei may require the detection of multiple neutrons in a neutron detector array. The detection of multiple neutrons is especially challenging due to the ``false-positives'' induced by cross-talk events between detectors. In this work, we report on the development of a cross-talk filter used to efficiently identify true neutron pairs while rejecting cross-talk events based on time of flight considerations. The classic method of neutron detection in the MeV range involves elastic scattering interactions with the hydrogen contained in organic scintillators, either plastic or liquid. To improve the performance of the cross-talk filter, it is possible to take into account the energy loss of the scattered neutrons. In this context, we are also investigating the possibility of using deuterated liquid scintillators, which can potentially provide better energy loss discrimination than in normal scintillators. This work is done by simulating the interactions of neutron pairs in various detector configurations using the simulation package GEANT4. [Preview Abstract] |
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