Bulletin of the American Physical Society
2011 Annual Meeting of the Four Corners Section of the APS
Volume 56, Number 11
Friday–Saturday, October 21–22, 2011; Tuscon, Arizona
Session D7: Detectors for Nuclear Physics |
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Chair: Bruce Barrett, University of Arizona Room: UA Student Union Tubac |
Friday, October 21, 2011 2:00PM - 2:12PM |
D7.00001: Efficiency of Moderated Neutron Lithium Glass Detectors Using Monte Carlo Techniques Brian James Due to national security concerns over the smuggling of special nuclear materials and the small supply of He-3 for use in neutron detectors, there is a great need for a new kind of neutron detector. Using Monte Carlo techniques I have been studying the use of lithium glass in varying configurations for neutron detectors. My research has included the effects of using a detector with two thin sheets of lithium at varying distances apart. I have also researched the effects of varying amounts of shielding a californium source with varying amounts of water. This is important since shielding would likely be used to make nuclear material more difficult to detect. The addition of one sheet of lithium-6 glass on the front surface of the detector significantly improves the efficiency for the detection of neutrons from a moderated fission source. [Preview Abstract] |
Friday, October 21, 2011 2:12PM - 2:24PM |
D7.00002: Neutron Detection using Lithium Glass Scintillator Adam Wallace, Lawrence Rees, Bart Czirr We have developed a neutron detector using a thin sheet of lithium-6 glass scintillator. Lithium-6 has a high capture cross-section for neutrons, giving high neutron detection efficiency. One of the difficulties of neutron detection is discriminating between neutron and gamma radiation. We have measured the gamma sensitivity of our detector to be one in 10,000. For nuclear non-proliferation applications, radioactive sources may be shielded. Unlike most neutron detectors, lithium glass detectors are more efficient at detecting neutrons if the source is shielded. We are testing different configurations to optimize the detector's neutron capture efficiency. [Preview Abstract] |
Friday, October 21, 2011 2:24PM - 2:36PM |
D7.00003: Optimization of Multi-Neutron Detection in a Detector Array using GEANT4 David Walter The study of neutron halos in light nuclei requires detection of multiple neutrons in a neutron detector array. This is especially challenging due to ``false-positives'' induced by crosstalk between detectors. In this work, we report on the development of a crosstalk filter used to efficiently differentiate between the detection of a single neutron inducing crosstalk and multiple (real) neutrons based on timing 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 crosstalk 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 even better discrimination than normal scintillators. This work is done by simulating the interaction of halo neutrons in various neutron detector configurations using the simulation package GEANT4. [Preview Abstract] |
Friday, October 21, 2011 2:36PM - 2:48PM |
D7.00004: Characterization of a Broken Lithium-6 Glass Neutron Detector for Improved Gamma Insensitivity Steven Gardiner, Lawrence Rees, Bart Czirr The gamma sensitivity of a neutron detector consisting of shards of \textsuperscript{6}Li-loaded glass scintillator was experimentally investigated. The intrinsic gamma-neutron detection efficiency (defined as the fraction of incident gamma rays which are misidentified as neutrons) of the detector was measured to be less than $1\times10^{-6}.$ Theoretical modeling with MCNP was also used to search for an optimally efficient broken glass detector design. The detector was modeled as a solid cylinder of poly(methyl methacrylate) with thousands of small scintillating glass spheres embedded within it. To enable the rapid specification of customizable geometries involving thousands of glass spheres, a library of Wolfram Mathematica functions was developed as an MCNP input file generation tool. [Preview Abstract] |
Friday, October 21, 2011 2:48PM - 3:00PM |
D7.00005: Progress towards a first-of-its-kind ion interferometer James L. Archibald, C.J. Erickson, Jarom Jackson, Michael Hermansen, Dean Anderson, Mark Cunningham, Dallin S. Durfee We are building the first matter-wave ion interferometer that works by exploiting the internal structure of the ions. The completed apparatus will allow novel tests of electromagnetic theory and other fundamental physics. The apparatus consists of a low-velocity intense source (LVIS) for $^87$Sr. Atoms emitted from the LVIS will be ionized using a two-photon transition to an auto-ionizing bound state. Interferometry will be achieved using stimulated Raman transitions between the hyperfine ground states of $^87$Sr$^+$. The laser system that will stimulate these transitions consists of a grating-stabilized, 408 nm master laser which is arranged in a double-pass configuration through a 2.5 GHz frequency-shifter to generate two beams that are detuned from one another by 5 GHz (which corresponds to the hyperfine splitting). These beams are then used to injection lock two slave lasers. We will discuss the theory of operation, potential applications, experimental techniques and our preliminary results. [Preview Abstract] |
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