Bulletin of the American Physical Society
2015 Fall Meeting of the APS Division of Nuclear Physics
Volume 60, Number 13
Wednesday–Saturday, October 28–31, 2015; Santa Fe, New Mexico
Session HH: Mini-Symposium on Applications of Nuclear Physics III |
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Chair: Lee Bernstein, Lawrence Livermore National Laboratory Room: General Kearny |
Friday, October 30, 2015 8:30AM - 8:42AM |
HH.00001: Deuterated-xylene (EJ301D): A new, improved deuterated scintillator for neutron spectroscopy Fred Becchetti, Ramon Torres-Isea, Michael Febbraro, Shaun Clarke, Angela Di Fulvio, Sara Pozzi In conjunction with Eljen Technologies (Sweetwater,TX), we have developed and evaluated a deuterated-xylene based liquid organic scintillator detector (3 in. x 3 in.) and PMT assembly. Like deuterated-benzene based scintillators such as EJ315 and NE230 the n$+$d recoil spectrum producing the light spectrum has distinct peaks corresponding to specific neutron energy groups. The light spectrum can then be unfolded to produce neutron energy spectra including fission spectra without the need for time-of-flight. This results in a large over-all detection efficiency for such detectors as they can be used in arrays covering a large angular range, close to the neutron source and do not require a pulsed or gated source. In addition, the new EJ301D scintillator has a lower neutron energy threshold for improved PSD, which is important in many low-energy measurements. More importantly this scintillator has a much safer flash point than benzene-based scintillators making it better suited for many applications including field applications in nuclear security and non-proliferation. [Preview Abstract] |
Friday, October 30, 2015 8:42AM - 8:54AM |
HH.00002: Capture-Gated Fast Neutron Spectroscopy H.P. Mumm, J.N. Abdurashitov, E.J. Beise, H. Breuer, V.N. Gavrin, C.R. Heimbach, T.J. Langford, M. Mendenhall, J.S. Nico, A.A. Shikhin We present recent developments in fast neutron detection using segmented spectrometers based on the principle of capture-gating. Our approach employs an organic scintillator to detect fast neutrons through their recoil interaction with protons in the scintillator. The neutrons that thermalize and are captured produce a signal indicating that the event was due to a neutron recoil and that the full energy of the neutron was deposited. The delayed neutron capture also serves to discriminate against uncorrelated background events. The segmentation permits reconstruction of the initial neutron energy despite the nonlinear response of the scintillator. We have constructed spectrometers using both He-3 proportional counters and Li-6 doping as capture agents in plastic and liquid organic scintillators. We discuss the operation of the spectrometers for the measurement of low levels of fast neutrons for several applications, including the detection of very low-activity neutron sources and the characterization of the flux and spectrum of fast neutrons at the Earth's surface and in the underground environment. [Preview Abstract] |
Friday, October 30, 2015 8:54AM - 9:06AM |
HH.00003: Spectral unfolding of fast neutron energy distributions Michelle Mosby, Kevin Jackman, Jonathan Engle The characterization of the energy distribution of a neutron flux is difficult in experiments with constrained geometry where techniques such as time of flight cannot be used to resolve the distribution. The measurement of neutron fluxes in reactors, which often present similar challenges, has been accomplished using radioactivation foils as an indirect probe. Spectral unfolding codes use statistical methods to adjust MCNP predictions of neutron energy distributions using quantified radioactive residuals produced in these foils. We have applied a modification of this established neutron flux characterization technique to experimentally characterize the neutron flux in the critical assemblies at the Nevada National Security Site (NNSS) and the spallation neutron flux at the Isotope Production Facility (IPF) at Los Alamos National Laboratory (LANL). Results of the unfolding procedure are presented and compared with \textit{a priori} MCNP predictions, and the implications for measurements using the neutron fluxes at these facilities are discussed. [Preview Abstract] |
Friday, October 30, 2015 9:06AM - 9:18AM |
HH.00004: Functionalization of Polymers with Fluorescent and Neutron Sensitive Groups for Efficient Neutron and Gamma Detection Adam Mahl, Henok Yemam, Tyler Remedes, Jack Stuntz, Unsal Koldemir, Alan Sellinger, Uwe Greife This presentation will review the efforts made by an interdisciplinary development project aimed at cost-effective, thermal neutron sensitive, plastic scintillators as part of the communities efforts towards replacing~$^{\mathrm{3}}$He based detectors. Colorado~School of Mines researchers with backgrounds in Physics and Chemistry have worked on the incorporation of~$^{\mathrm{10}}$B in plastics through admixture of various commercial and novel dopants developed at CSM. In addition, new fluorescent dopants have been developed for plastic scintillators in an effort towards better understanding quenching effects and scintillator response to thermal neutrons via pulse shape discrimination methods. Results on transparent samples using fluorescent spectroscopy and gamma/neutron excitation will be presented. [Preview Abstract] |
Friday, October 30, 2015 9:18AM - 9:30AM |
HH.00005: Elastic and Inelastic Neutron Scattering with a C$^7$LYC Array G.L. Wilson, T. Brown, P. Chowdhury, E. Doucet, C.J. Lister, N. D'Olympia, M. Devlin, S. Mosby A scintillator array of 16 1" x 1" Cs$_2$LiYCl$_6$ (CLYC) detectors has been commissioned for low energy nuclear science. Standard CLYC crystals detect both gamma rays and neutrons rays with excellent pulse shape discrimination, with thermal neutrons detected via the $^6$Li(n,$\alpha$)t reaction. Our discovery of spectroscopy-grade response of CLYC for fast neutrons via the $^{35}$Cl(n,p) reaction, with a pulse height resolution of under 10$\%$ in the $<$ 8 MeV range, led to our present array of $^7$Li enriched C$^7$LYC detectors, where the large thermal neutron response is essentially eliminated [1]. While the intrinsic efficiency of C$^7$LYC for fast neutron detection is low, the array can be placed near the target since a long TOF arm is no longer needed for neutron energy measurement, thus recovering efficiency through increased solid angle coverage. The array was recently deployed at Los Alamos to test its capability in measuring differential scattering cross sections as a function of energy for $^{56}$Fe and $^{238}$U. The incident energy from a white neutron source was measured via TOF, and the scattered neutron energy via the pulse height. Techniques, analysis and first results will be discussed.\\[4pt] [1] N. D'Olympia et al., NIM A694 (2012) 140, and NIM A763 (2014) 433. [Preview Abstract] |
Friday, October 30, 2015 9:30AM - 9:42AM |
HH.00006: Windowless Gas Target for Neutron-based Imaging Micah S. Johnson, J.L. Ellsworth, P.J. Fitsos, J.M. Hall, B. Rusnak National security and safeguards agencies are seeking technologies to image very dense objects. Critical to their mission objectives is the need to measure the geometry and internal components of the dense objects. One possible method is to use neutron-based imaging because of the neutron's long mean path length. Neutrons can be produced in a variety of reactions with a variety of materials. For this presentation, we will discuss our method to use (d,n) production reaction on deuterium gas. A windowless gas target for this particular system is required because of the large power of the 7 MeV, 300$\mu $A deuteron beams. We will discuss our windowless gas target and its capabilities. We will present measurements and discuss the results and outlook. [Preview Abstract] |
Friday, October 30, 2015 9:42AM - 9:54AM |
HH.00007: The Berkeley Low Background Facility and the Black Hills State University Underground Campus at SURF Keenan Thomas, Brianna Mount, Kevin Lesko, Eric Norman, Alan Smith, Alan Poon, Yuen-Dat Chan The Berkeley Low Background Facility at LBNL provides a variety of low background gamma spectroscopy services to a variety of projects and experiments. It operates HPGe spectrometers in two unique facilities: a surface low background lab at LBNL and underground (4300 m.w.e.) at the Sanford Underground Research Facility in Lead, SD. A large component of the measurements performed by the BLBF are for ultralow background experiments concerned with U, Th, K, and other radioisotopes within candidate construction materials to be used to construct sensitive detectors, such as those studying dark matter or neutrinos. The BLBF also makes a variety of environmental measurements in search of other radioisotopes, such as fallout from the Fukushima nuclear power plant accident in 2011 and other radioisotope monitoring activities. A general overview of the services and facilities will be presented. In 2015, the BLBF will be relocating its underground counting stations to a new, dedicated space on the 4850L of SURF. The Black Hills State University Underground Campus will host several low background counting stations and operate in a coordinated manner to provide low background measurements to the scientific community. An overview and description of the BHUC will be presented. [Preview Abstract] |
Friday, October 30, 2015 9:54AM - 10:06AM |
HH.00008: Radiation effects testing at the 88-Inch Cyclotron Larry Phair In addition to basic research, the 88-Inch Cyclotron provides a crucial service to organizations involved in the U.S. space program. The space application testing includes heavy-ion beams for single event upset (SEU) tests on integrated circuits. A ``Cocktail'' beam (where multiple ions of the same mass/charge ratio are injected into the cyclotron) is used to mimic cosmic ray damage of integrated circuits. Plots of the failure cross section versus amount of energy deposited (LET = linear energy transfer) for different beams are used to predict how the circuit components will perform in a radiation environment such as space. We will review the analysis of such data and their trends. [Preview Abstract] |
Friday, October 30, 2015 10:06AM - 10:18AM |
HH.00009: Single Event Effect microchip testing at the Texas A{\&}M University Cyclotron Institute Henry Clark, Sherry Yennello A Single Event Effect (SEE) is caused by a single, energetic particle that deposits a sufficient amount of charge in a device as it transverses it and upsets its normal operation. Soft errors are non-destructive and normally appear as transient pulses in logic or support circuitry, or as bit flips in memory cells or registers. Hard errors usually result in a high operating current, above device specifications, and must be cleared by a power reset. Burnout errors are so destructive that the device becomes operationally dead. Spacecraft designers must be concerned with the causes of SEE's from protons and heavy ions since commercial devices are typically chosen reduce the parameters of power, weight, volume and cost but have increased functionality, which in turn are typically vulnerable to SEE. As a result all mission-critical devices must be tested. The TAMU K500 superconducting cyclotron has provided beams for space radiation testing since 1994. Starting at just 100 hours/year at inception, the demand has grown to 3000 hours/year. In recent years, most beam time has been for US defense system testing. Nearly 15{\%} has been provided for foreign agencies from Europe and Asia. An overview of the testing facility and future plans will be presented. [Preview Abstract] |
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