Bulletin of the American Physical Society
APS April Meeting 2017
Volume 62, Number 1
Saturday–Tuesday, January 28–31, 2017; Washington, DC
Session M15: Nuclear Instrumentation |
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Sponsoring Units: DNP Chair: Warren Rogers, Indiana Wesleyan University Room: Washington 2 |
Sunday, January 29, 2017 3:30PM - 3:42PM |
M15.00001: Measuring position in 2-dimensions using induced signals in a microchannel plate detector Blake Wiggins, Romualdo deSouza Position-sensitive microchannel plate (MCP) detectors play an important role in the detection of photons, electrons, ions, and neutrons. Recently, a novel approach has been developed to provide position-sensitivity for an MCP detector. In this approach, namely the induced signal approach, the position of the incident particle is determined by sensing the electron cloud emanating from a MCP stack. The induced signals are inherently bipolar, where the negative lobe of the induced signal corresponds to the approach of the electron cloud to the sense wires and the positive lobe corresponds to the recession of the electron cloud from the sense wires. The zero-crossing point is the time at which the centroid of the charge cloud passes the wire plane. For a single incident electron, a spatial resolution of 103 $\mu$m (FWHM) has been achieved by utilizing the zero-crossing point of the induced signals. General considerations suggest that this spatial resolution can be improved by using the entire pulse shape information. The fundamentals of the induced signal approach as well as its implementation in slow neutron radiography will be presented. [Preview Abstract] |
Sunday, January 29, 2017 3:42PM - 3:54PM |
M15.00002: A highly stable 30 keV proton accelerator for studies of angular detection efficiency on Si detectors Americo Salas Bacci, Stefan Baessler, Peter Carr, Thomas Hefele, Dinko Pocanic, Nicholas Roane, Aaron Ross, R. Slater, Alexander Smith, Csaba Toth, Dane Warner, Shawn Zamperini, Panaiot Zotev The Nab experiment at the SNS measures the electron-neutrino correlation parameter and the Fierz interference term in free neutron beta decay by measuring in coincidence the electron energy and proton momentum in a magnetic spectrometer with two Si detectors. These large area, thick, and 127-hexagonal segmented Si detectors have to be carefully characterized for optimal performance and for control of systematic errors. The angular detection efficiency of 30 keV proton incident on Si is an important part of this studies. We will present the design, simulation, operation, and detection of 30\,keV H$^+$ and H$^{+}_{2}$ as well as results to control the beam stability by the correlation of both detected ion signals. At present we have reached beam stability of (1.2 $\pm$1.3)E-7/sec. [Preview Abstract] |
Sunday, January 29, 2017 3:54PM - 4:06PM |
M15.00003: Development of a forward-angle gamma-ray detector array for MoNA-LISA Daniel Votaw In recent years invariant mass spectroscopy has been successfully applied to measure neutron-unbound states. In this method neutrons are measured in coincidence with~charged fragments following reactions with radioactive beams produced in projectile fragmentation reactions. When the final nucleus has bound excited states it is necessary to include gamma-ray detection in order to extract the excitation energy of the initial state. Because the MoNA-LISA setup at NSCL uses a large-gap Sweeper magnet to deflect the charged particles, conventional gamma-ray scintillation arrays cannot be used efficiently because of the large fringe field of the magnet. Thus we are developing a small cesium iodide (CsI) array using silicon photomultipliers (SiPMs) which are agnostic to the presence of a magnetic field. Using GEANT4 simulations the parameters of the array will be optimized to achieve the required efficiency and energy resolution of the Doppler-corrected energy spectra, necessary to extract the gamma-ray transitions in the final nucleus. [Preview Abstract] |
Sunday, January 29, 2017 4:06PM - 4:18PM |
M15.00004: Detection system for electron-proton coincidences in neutron decay Leah Broussard By precisely measuring angular correlations in neutron decay, we can perform precise tests of the Standard Model and search for new physics beyond the Standard Model. The upcoming Nab and UCNB experiments will measure the correlations $a$ and $b$, and $B$, respectively, in neutron decay. The collaborations have jointly developed a prototype detection system based on thick, large area silicon detectors which meets experimental requirements of $\sim$3~keV FWHM energy resolution, rise times of $\sim$50~ns, and energy thresholds below 10~keV. We will present results of characterization of the prototype and an update on the development of the final, fully instrumented detection system. We also present a study of very thin deadlayer silicon drift detectors in development by the TRISTAN collaboration, and their possible applicability to neutron decay correlation experiments. [Preview Abstract] |
Sunday, January 29, 2017 4:18PM - 4:30PM |
M15.00005: Holography with a neutron interferometer Dusan Sarenac, David G. Cory, Dmitry A. Pushin, Benjamin Heacock, Michael G. Huber, M. Arif, Charles W. Clark, Chandra B. Shahi We demonstrate the first neutron hologram of a macroscopic object.\footnote{D. Sarenac, {\em et al.}, Optics Express {\bf 24}, 22528 (2016).} Using a Mach-Zehnder neutron interferometer in a configuration similar to the optical setup of Bazhenov {\em et al.},\footnote{V. Y. Bazhenov, M. V. Vasnetsov, and M. S. Soskin, Pis’ma Zh. Eks. Teor. Fiz. {\bf 52}, 1037 (1990).} our reference beam passes through a fused silica prism that provides a linear phase gradient, and our object beam beam passes through an aluminum spiral phase plate with a topological charge of $\ell = 2$, which was recently used in studies of neutron orbital angular momentum.\footnote{C. W. Clark, {\em et al.}, Nature {\bf 525}, 504 (2015).} Interference of reference and object beams in a two-dimensional imaging detector produces the hologram, which is a fork dislocation structure similar to those used to generate atomic\footnote{ H. He, {\em et al.}, J. Mod. Opt. {\bf 42}, 217 (1995).}$^,$\footnote{M. F. Andersen, {\em et al.}, Phys. Rev. Lett. {\bf 97}, 170406 (2006).} and electronic\footnote{B. J. McMorran, {\em et al.}, Science {\bf 331}, 192 (2011).} vortex beams. Our neutron hologram is made in an interferometer in which at most one neutron is present at any given time. [Preview Abstract] |
Sunday, January 29, 2017 4:30PM - 4:42PM |
M15.00006: ABSTRACT WITHDRAWN |
Sunday, January 29, 2017 4:42PM - 4:54PM |
M15.00007: Ultra-High Sensitivity Techniques for the Determination of 3He/4He Abundances in Helium by Accelerator Mass Spectrometry H. P. Mumm, M. Huber, W. Bauder, N. Abrams, C. Deibel, C. Huffer, P. Huffman, K. Schelhammer, R. Janssens, C. Jiang, R Scott, R. Pardo, K. Rehm, R. Vondrasek, C. Swank, C. O'Shaughnessy, M. Paul, L. Yang We report the development of an Accelerator Mass Spectrometry technique to measure the 3He/4He isotopic ratio using a radio frequency (RF) discharge source and the ATLAS facility at Argonne National Laboratory.~ Control over 3He/4He ratio in helium several orders of magnitude lower than natural abundance is critical for neutron lifetime and source experiments using liquid helium.~ Due to low ultimate beam currents, the ATLAS accelerator and beam line were tuned using a succession of species of the same M/q.~ A unique RF source was developed for the experiment due to large natural 3He backgrounds.~ Analog H\textunderscore 3\textasciicircum $+$ and DH\textasciicircum $+$ molecular ions are eliminated by dissociation via a gold stripper foil near the detector. The stripped ions were dispersed in a magnetic spectrograph and 3He\textasciicircum 2$+$ ions counted in the focal plane detector. This technique is sensitive to 3He/4He ratios in the regime of 10\textasciicircum -12 with backgrounds that appear to be below 10\textasciicircum \textunderscore 14.~ The techniques used to reduce the backgrounds and remaining outstanding problems will be presented along with results from measurements on high purity 4He samples. [Preview Abstract] |
Sunday, January 29, 2017 4:54PM - 5:06PM |
M15.00008: Direct Comparison of M\o ller and Compton Polarimeters in Hall C at Jefferson Lab Dave Gaskell Knowledge of the electron beam polarization is one of the most important systematic uncertainties in precision, parity-violating electron scattering experiments with next generation experiments aiming to measure the electron beam polarization to better than 0.5\%. At high energies, the most typical polarimetry techniques are M\o ller (polarized electron-electron) and Compton (polarized electron-photon) scattering. The use of two techniques with different systematic uncertainties provides confidence in the extracted beam polarization. Direct comparisons of the two polarimetry techniques are challenging in that Compton polarimeters typically desire maximum beam flux (high beam currents) while M\o ller polarimeters need to limit the beam current to avoid depolarization effects in the target. We have performed a direct comparison of the M\o ller and Compton polarimeters in experimental Hall C at Jefferson Lab. This test is unique in that the data were taken sequentially under identical beam conditions at $\approx$4.5~$\mu$A. We found excellent agreement between the Hall C M\o ller and Compton polarimeters. Combined with high-current Compton data, we were also able to limit the beam current dependence of the beam polarization to 1\% or less up to a beam current of 180~$\mu$A. [Preview Abstract] |
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