Bulletin of the American Physical Society
2012 Fall Meeting of the APS Division of Nuclear Physics
Volume 57, Number 9
Wednesday–Saturday, October 24–27, 2012; Newport Beach, California
Session NC: Instrumentation V: UCN, EDM, misc |
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Chair: Victor Gehman, Lawrence Berkeley National Laboratory Room: Plaza III |
Saturday, October 27, 2012 8:30AM - 8:42AM |
NC.00001: Performance of the Los Alamos National Laboratory spallation-driven solid-deuterium ultra-cold neutron source Christopher Morris The performance of the Los Alamos spallation-driven solid-deuterium Ultra Cold Neutron (UCN) source will be described. The source uses 800 MeV protons from the LANSCE accelerator impacting a tungsten target to produce spallation neutrons, which are then reflected by a beryllium shield, cooled by a polyethylene moderator, then downscattered to ultra-cold temperatures in a solid deuterium converter. Measurements of the cold neutron flux, the very cold neutron production rate, and the UCN rates and density at the exit from the biological shield will be presented and compared to Monte Carlo simulations. The cold neutron rates compare well with predictions from the Monte Carlo code MCNPX and the UCN rates agree with results from our UCN Monte Carlo code. The maximum delivered UCN density at the biological shield exit was 52(9) UCN/cc. [Preview Abstract] |
Saturday, October 27, 2012 8:42AM - 8:54AM |
NC.00002: Evaluation of a lithium-glass based composite neutron detector for $^{3}$He replacement Grayson Rich, Kareem Kazkaz, H. Paul Martinez In light of the reduction of the world's supply of helium-3 and the increasing demand for neutron detection in the fields of physics research, national security, and nuclear energy, the need for a suitable alternative to $^{3}$He-based detector technology is of paramount importance. It is critical that a potential replacement boast both high neutron detection efficiency and insensitivity to, or the ability to discriminate against, gamma-ray backgrounds. Recent efforts investigating the use of composite detectors, specifically highly neutron-sensitive scintillators embedded in scintillating acrylic, have shown promise but need further improvements to be competitive with moderated helium-3 tubes. Endeavoring to increase the neutron detection efficiency over composite detectors of earlier efforts, we have fabricated a 5'' x 5'' cylindrical detector of polyvinyltoluene embedded with 1.5-mm lithium-glass cubes composing 10{\%} of the total mass. The results of both simulations and experiments comparing our Li-glass based composite detector to other composite technologies and to $^{3}$He are presented. Prepared by LLNL under Contract DE-AC52-07NA27344. LLNL-ABS-XXXXXX. [Preview Abstract] |
Saturday, October 27, 2012 8:54AM - 9:06AM |
NC.00003: Characterization of large area, thick, and segmented silicon detector for electron and proton detection from neutron beta decay experiments in the cold and ultracold energies Americo Salas Bacci, Patrick McGaughey, Stefan Baessler, Leah Broussard, Mark Makela, Jacqueline Mirabal, Robert Pattie, Dinko Pocanic, Seth Hoedl, Sky Sjue, Seppo Penttila, Syed Hasan, Scott Wilburn, Albert Young, Bryan Zeck, Zhehui Wang The ``Nab'' and ``UCNB'' collaborations have proposed to measure the correlation parameters in neutron $\beta$-decay at Oak Ridge and Los Alamos National Laboratory, using a novel detector design and electromagnetic spectrometers. Two large area, thick, hexagonal-segmented Silicon detectors containing 128 pixels per detector are going to be used to detect the electron and proton from neutron decay. Both Silicon detectors are connected by magnetic field lines of few Tesla field strength, and set on an electrostatic potential, such that protons can be accelerated up to 30 keV in order to be detected. We report the characterization, operation, proton detection from 15 to 30 keV, total pulse height defect, computation of atomic scattering defect, recombination defect, and evaluation of dead layer for these large area and thick Silicon detectors. [Preview Abstract] |
Saturday, October 27, 2012 9:06AM - 9:18AM |
NC.00004: Response of BC418 Plastic Scintillator to Low Energy Protons B.H. Daub, V. Henzl, M.A. Kovash, J.L. Matthews, Z.W. Miller, K. Shoniyozov, H. Yang The response of fast plastic scintillators is unknown for proton energies below approximately 300 keV. The response of BC418 plastic scintillator to protons from 100 keV to 3.6 MeV was measured using elastic scattering of neutrons at the University of Kentucky and at the Los Alamos Neutron Science Center. At Kentucky, protons of precise energies from a Van de Graaff accelerator impinged on a thin LiF target to produce neutrons in narrow energy bands. At Los Alamos, neutrons were produced from a tungsten spallation source and their energies determined by time of flight. In both experiments a coincidence was detected between the recoiling proton in the plastic scintillator and the elastically scattered neutron in a liquid scintillator. The energy of the recoil proton is determined by the elastic scattering kinematics, with the scattered neutron energy precisely determined by time of flight. The results are compared with previous measurements of the response of similar plastic scintillators in the energy region where they overlap. [Preview Abstract] |
Saturday, October 27, 2012 9:18AM - 9:30AM |
NC.00005: Data acquisition for the UCNB experiment Sky Sjue The UCNB experiment will simultaneously detect protons and electrons from the beta decay of ultracold neutrons (UCN) to measure the neutrino asymmetry B using 2 mm-thick, 128 pixel-segmented Si detectors (also in development for the Nab experiment). The data acquisition system must provide timing resolution on the order of nanoseconds with minimal dead time to detect coincidences and backscattering of electrons from the Si detector. Proton detection will be achieved by biasing the entire detector and detector mount to roughtly -30 kilovolts. Detection of these protons requires a low noise threshold and good energy resolution. The system must be scalable to simultaneously operate 256 channels on two detectors for the fully instrumented experiment. The performance of a 12 bit, 250 MHz flash ADC data acquisition system meets these requirements. Customized triggering algorithms using the system's FPGA allow a low noise threshold while keeping the rate adequately low and providing ample waveform data for our resolution requirements. We will present data from low energy beta emitters and electron-proton coincidences from the decay of UCN at the LANL source to demonstrate the performance of this system. [Preview Abstract] |
Saturday, October 27, 2012 9:30AM - 9:42AM |
NC.00006: Accessing Interior Vector Magnetic Field Components in Neutron EDM Experiments via Boundary Value Techniques Brad Plaster We propose a new technique for the determination and monitoring of the interior vector magnetic field components during the operation of neutron EDM experiments. If a suitable three-dimensional volume surrounding the fiducial volume of an experiment can be defined which contains no interior currents or magnetization, each of the interior vector field components will satisfy the Laplace Equation within this volume. Therefore, if the field components can be measured on the boundary, the interior vector field components can be determined uniquely via numerical solution of the Laplace Equation. We discuss the applicability of this technique to the determination of the magnetic field components and magnetic field gradients in the fiducial volumes of neutron EDM experiments. [Preview Abstract] |
Saturday, October 27, 2012 9:42AM - 9:54AM |
NC.00007: Detector Array Performance Estimates for Nuclear Resonance Fluorescence Applications Micah Johnson, J.M. Hall, D.P. McNabb There are a myriad of explorative efforts underway at several institutions to determine the feasibility of using photonuclear reactions to detect and assay materials of varying complexity and compositions. One photonuclear process that is being explored for several applications is nuclear resonance fluorescence (NRF). NRF is interesting because the resonant lines are unique to each isotope and the widths are sufficiently narrow and the level densities are sufficiently low so as to not cause interference. Therefore, NRF provides a means to isoptically map containers and materials. The choice of detector array is determined by the application and the source. We will present results from a variety of application studies of an assortment of detector arrays that may be useful. Our results stem from simulation and modeling exercises and benchmarking measurements. We will discuss the data requirements from basic scientific research that enables these application studies. We will discuss our results and the future outlook of this technology. [Preview Abstract] |
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