Bulletin of the American Physical Society
2017 Fall Meeting of the APS Division of Nuclear Physics
Volume 62, Number 11
Wednesday–Saturday, October 25–28, 2017; Pittsburgh, Pennsylvania
Session JD: Nuclear Instrumentation III |
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Chair: Nathan Frank, Augustana College Room: Salon 4 |
Friday, October 27, 2017 10:30AM - 10:42AM |
JD.00001: DESCANT - Testing and Commissioning Vinzenz Bildstein, P.E. Garrett, D. Bandyopadhay, J. Bangay, L. Bianco, G. Demand, B. Hadinia, K.G. Leach, C. Sumithrarachchi, J. Turko, J. Wong, S.F. Ashley, B.P. Crider, M.T. McEllistrem, E.E. Peters, F.M. Prados-Est\'{e}vez, S.W. Yates, J.R. Vanhoy, G.C. Ball, D.P. Bishop, A.B. Garnsworthy, G. Hackman, C.J. Pearson, B. Shaw, F. Sarazin The DESCANT array at TRIUMF is designed to detect neutrons from RIB experiments. DESCANT is composed of 70 close-packed deuterated organic liquid scintillators coupled to digital fast read-out ADC modules. This configuration permits online pulse-shape discrimination between neutron and $\gamma$-ray events. A prototype detector was tested with monoenergetic neutrons at the University of Kentucky Accelerator Laboratory. The data from these tests was compared to Geant4 simulations. A first commissioning experiment of the full array, using the decay of \textsuperscript{145-146}Cs, was performed in August 2016. The results of the tests and a preliminary analysis of the commissioning experiment will be presented. [Preview Abstract] |
Friday, October 27, 2017 10:42AM - 10:54AM |
JD.00002: Development of a neutron detector with tracking capabilities (NEXT) David Perez-Loureiro, Robert Grywacz, Leonard D. Mostella, Mustafa Rajabali, Kyle Schmitt Future rare isotope beam facilities, like FRIB, will make it possible to access the very neutron-rich side of the nuclear landscape, approaching, and even reaching the neutron dripline in certain cases. Far from stability, neutron separation energies become lower and accessible via beta decay. Therefore, beta delayed neutron spectroscopy will be an essential method of obtain information about the nuclear structure for very neutron-rich nuclei. The NEXT detector will be a high resolution neutron detector array based on time of flight measurements. It will be composed of small modules of neutron-discriminating plastic scintillator coupled to silicon photomultipliers (SiPMs) for the readout. During the R\&D phase of the project prototypes of different geometries of the modules are being tested. Plastic scintillator coupled to 6~mm silicon photomultipliers are being used to investigate the timing capabilities of these detectors using digital electronics data acquisition. In parallel, detailed Montecarlo simulation codes are being developed to optimize light collection efficiency and define the final geometry of the array. The status of the project and most recent results will be presented in this contribution. [Preview Abstract] |
Friday, October 27, 2017 10:54AM - 11:06AM |
JD.00003: Spectroscopic Investigations with Dual Neutron-Gamma Scintillators P. Chowdhury, T. Brown, E. Doucet, C.J. Lister, C. Morse, A.M. Rogers, G.L. Wilson, M. Devlin, N. Fotiades, J.A. Gomez, S. Mosby The spectroscopic capabilities of $^7$Li-enriched Cs$_2$$^7$LiYCl$_6$ (C$^7$LYC) dual neutron-gamma scintillators are being tested in diverse application arenas to exploit the excellent pulse-shape discrimination together with the unprecedented pulse height resolution ($\sim$10\%) for fast neutrons in the $<$ 8 MeV range via the $^{35}$Cl(n,p) reaction [1]. Test experiments include both elastic and inelastic neutron scattering cross-sections on $^{56}$Fe at Los Alamos with a pulsed white neutron source, as well as (p,n) and (d,n) reactions on low-Z targets using mono-energetic proton and deuteron beams from the 5.5 MV Van de Graaff accelerator at the UMass Lowell Radiation Laboratory. Tests of waveform digitizers with different sampling rates are also being performed. A key goal is to evaluate whether the low intrinsic efficiency of C$^7$LYC for fast neutrons compared to traditional neutron detectors, such as liquid scintillators, can be effectively offset by the gain in solid angle obtained by positioning the detectors much closer to the target, since the typical long time-of-flight arms for energy resolution are not necessary.\\ 1. N. D'Olympia et al., Nucl. Inst. Meth. A694, 140 (2012), and A763, 433 (2014). [Preview Abstract] |
Friday, October 27, 2017 11:06AM - 11:18AM |
JD.00004: Large Cleaner Detectors for the UCN$\tau$ Neutron Lifetime Experiment Francisco Gonzalez The UCN$\tau$ experiment at Los Alamos National Laboratory measures the neutron $\beta$-decay lifetime by storing ultracold neutrons (UCNs) in a magneto-gravitational trap for holding times longer than the neutron's lifetime. Neutrons with energies above the trapping potential can escape the trap, giving rise to a systematic error. To mitigate this effect, a large polyethylene sheet is lowered into the trap to remove the high energy unbound neutrons. High energy UCN upscatter in the polyethylene sheet and leave the trap. Such a "UCN spectrum cleaner," covering half the trap top, was shown to be effective in removing high-energy neutrons in previous run cycles. During this run cycle, the UCN$\tau$ collaboration has added two thermal neutron detectors on the spectrum cleaner. The new thermal neutron detectors will monitor high-energy neutrons throughout upcoming run cycles, providing important information on the neutron normalization, spectral cleaning, and heating during storage. These detectors use LiF-ZnS sheets coupled to a wavelength-shifting plastic slab, with silicon photomultipliers attached to the edges. We will present results of the light detection simulation and performance tests of these detectors. [Preview Abstract] |
(Author Not Attending)
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JD.00005: Calibration and Characterization of the UNCB and Nab Detectors Bryan Zeck The UCNB and Nab experiments are designed to produce precision measurements of the free neutron decay angular correlations $B$, $a$, and $b$. Measurements of $B$ and $a$ require a coincident detection of the proton and electron produced in neutron decay, while for $b$, which manifests as a subtle shift in the electron energy spectrum, energy resolution better than $3$ keV is desired and excellent fidelity for energy reconstruction is required, including characterization of non-linearity to the $10^{-4}$ level. To this end, a thick segmented silicon detector with a $100$ nm dead layer and a $100$ cm active area has been extensively characterized at LANL. The thin dead layer allows protons accelerated to $30$ keV to deposit energy above threshold in the active volume of the detector, and the paired amplifer chain, developed at LANL, has a risetime of approximately $40$ ns. Comparison of simulation to experiment reveals a detector resolution better than $\sigma = 2.5$ keV. A complete characterization of the detector will be presented. [Preview Abstract] |
Friday, October 27, 2017 11:30AM - 11:42AM |
JD.00006: Absolute calibration of a cold and thermal neutron detector using monochromatic neutron beam Jin Ha Choi, Christopher Cude-Woods, Takeyasu Ito, Albert Young Time of flight spectra for cold neutrons exiting the moderator volume of the LANSCE UCN source has been obtained using a commercial neutron scintillator, EJ-426, coupled to a Hamamatsu R1355. The absolute efficiency for this detector system was determined using a 37.4 meV (monochromatic) neutron beam from the Neutron Powder Diffraction Facility (NPDF) at North Carolina State University's PULSTAR reactor. We measured the absolute neutron flux at the NPDF through thin foil activation and explored threshold effects through analysis of the measured pulse height distribution for effectively pure neutron signals from the NPDF beam. Non-uniformity of the flux profile across the detector and the detection efficiency as a function of the point of incidence of neutrons on the scintillator was explored using a X-Y translation system to perform scans using either fixed or movable apertures. The results are generally consistent with our expectations for this system, and provide a quantitative assessment of the sensitivity of this system to cold and thermal neutrons. [Preview Abstract] |
Friday, October 27, 2017 11:42AM - 11:54AM |
JD.00007: Direct Observation of Neutron Scattering in BC408 Scintillator for Comparison with SImulation W. F. Rogers, J. E. Boone, A. Wantz, N. Frank, A. N. Kuchera, S. Mosby, M. Thoennessen Monte Carlo simulation provides an important tool for the interpretation of neutron scattering data in the Modular Neutron Array (MoNA) and the Large multi-Institutional Scintillator Array (LISA), each located at the NSCL facility at MSU and consisting of 144 stacked 2-m long organic plastic scintillator bar detectors. Energy and trajectory for unbound state decay neutrons are determined by time of flight and location of first light produced in the array. While most neutrons scattering elastically from protons and inelastically from C nuclei produce light above detector threshold, those scattered elastically from C remain below threshold (``dark scatter''), altering neutron trajectories, thus decreasing energy and momentum resolution. To test the accuracy of ourGeant4/MENATE\_R simulations, we observed neutrons scattering from 16 MoNA bars arranged in two stack geometries at the LANSCE facility at Los Alamos National Laboratory. Spallation neutrons ranging in energy from 0.5 to 800 MeV emerged from a 3 mm collimator in the 90m shed on WNR flight path 4FP15L and struck the array along a well defined path. Results for neutron hit multiplicity, scattering dynamics, and dark scatter redirection are compared with simulation. [Preview Abstract] |
Friday, October 27, 2017 11:54AM - 12:06PM |
JD.00008: A Charged Particle Veto Wall for the Large Area Neutron Array (LANA) K. Zhu, Z. Chajecki, C. Anderson, J. Bromell, K. Brown, J. Crosby, S. Kodali, W.G. Lynch, P. Morfouace, S. Sweany, M.B. Tsang, C. Tsang, J.J. Brett, J.L. Swaim Comparison of neutrons and protons emitted in heavy ion collisions is one of the observables to probe symmetry energy, which is related to the properties of neutron star. In general, neutrons are difficult to measure and neutron detectors are not as easy to use or as widely available as charged particle detectors. Two neutron walls (NW) called LANA exist at the National Superconducting Cyclotron Laboratory. Although the NSCL NW attains excellent discrimination of $\gamma $ rays and neutron, it fails to discriminate charged particles from neutrons. To ensure near 100{\%} rejection of charged particles, a Charged Particle Veto Wall (VW) is being jointly built by Michigan State University and Western Michigan University. It will be placed in front of one NW. To increase efficiency in detecting neutrons, the second neutron wall is stacked behind it. In this presentation, I will discuss the design, construction and testing of the VW together with the LANA in preparation of two approved NSCL experiments to probe the density and momentum dependence of the symmetry energy potentials in the equation state of the asymmetric nuclear matter. [Preview Abstract] |
Friday, October 27, 2017 12:06PM - 12:18PM |
JD.00009: An Alternative to Excimer Based Neutron Detection Chandra Shahi, Josh Graybill, Uwe Arp, Alan Thompson, Michael Coplan, Charles Clark Scintillations from the noble gases excited by energetic charged particles consist of broad-band radiation from the decay of noble gas excimers and atomic line radiation. For xenon excited by MeV alpha particles, the excimer radiation is in the extreme ultra-violet (EUV), centered about 170 nm. The atomic line radiation is primarily in the ultraviolet (UV). The xenon excimer radiation has led to the development of a thermal neutron detector that consists of a film of $^{10}$B immersed in xenon at pressures up to one bar\footnote{J. C. McComb, {\em et al.}, J. Appl. Phys. {\bf 115}, 144504 (2014).}. The energetic products of the $^{10}$B(n,$\alpha)^{7}$Li reaction produce the excimer radiation that is detected by an EUV sensitive photomultiplier tube (PMT). Examination of the xenon UV atomic radiation over the region from 200 to 400 nm shows both sharp and broadened lines that can be associated with transitions in neutral and ionized atomic xenon. The ratio of the UV to EUV radiation is approximately 1:3, in agreement with the previous studies\footnote{A. Sayers and C. S. Wu, Rev. Sci. Instr. {\bf 28}, 758 (1957).}. This UV radiation has made it possible to replace the low quantum efficiency, high voltage EUV PMT with a silicon photomultiplier. [Preview Abstract] |
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