Bulletin of the American Physical Society
APS April Meeting 2017
Volume 62, Number 1
Saturday–Tuesday, January 28–31, 2017; Washington, DC
Session H13: Minisymposium: Instrumentation for Low Energy Nuclear and Neutrino PhysicsFocus
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Sponsoring Units: DNP Chair: Sharon Stephenson, Gettysburg College Room: Roosevelt 5 |
Sunday, January 29, 2017 8:30AM - 9:06AM |
H13.00001: A High Rigidity Spectrometer for the Facility for Rare Isotope Beams. Invited Speaker: Remco Zegers The High Rigidity Spectrometer (HRS) will be the centerpiece experimental tool of the Facility for Rare-Isotope Beams (FRIB) fast-beam program. The fast-beam program has tremendous discovery potential, enabling experiments with beam intensities of a few ions per second or less through the luminosity afforded by thick targets. The high magnetic rigidity of the HRS (up to 8 Tm) will match the rigidities at which rare-isotope production yields at the FRIB fragment separator are maximum across the entire chart of nuclei and enable experiments with the most neutron-rich nuclei available at FRIB. Gain factors in luminosity of ten or more are achievable compared to running with existing spectrometers, which have a maximum rigidity of 4 Tm, with the highest gains for the most neutron-rich unstable isotopes. To enable a broad spectrum of experiments, the HRS will accommodate different ion-optical modes and provide the flexibility to run in coincidence with a diverse set of other detector systems, such as the Gamma Ray Energy Tracking Array (GRETA) and the Modular Neutron Array (MoNA-LISA). In the presentation, an overview of the scientific opportunities with the HRS and the present layout, based on ion-optical and magnet-feasibility studies, will be given. [Preview Abstract] |
Sunday, January 29, 2017 9:06AM - 9:18AM |
H13.00002: Direct Observation of Neutron Scattering in MoNA Scintillator Detectors W. F. Rogers, S. Mosby, N. Frank, A.N. Kuchera, M. Thoennessen Monte Carlo simulations provide an important tool for the interpretation of neutron scattering data in the MoNA and LISA arrays at NSCL. Neutron energy and trajectory are determined by time of flight and position of first light produced in the array. Neutrons elastically scattered from H and inelastically from C typically produce light above detector threshold, while those elastically scattered from C produce light below threshold (``dark scattering'') and are redirected in flight, thus lowering energy and trajectory resolution. In order to test the effectiveness of our Geant4/MENATE\_R simulations, we conducted an experiment at the LANSCE facility at Los Alamos National Laboratory to observe scattering of individual neutrons with well defined energy and trajectory in 16 MoNA detector bars arranged in two different stack geometries. Neutrons with energies ranging from 0.5 to 800 MeV emerged from a 3 mm collimator in the 90m shed on the WNR 4FP15L flight path to enter the array at a well defined point. Several features of neutron scattering are compared with simulation predictions, including hit multiplicity, scattering angle, mean distance between scatters, and the effect of dark scatter redirection. Results to date will be presented. [Preview Abstract] |
Sunday, January 29, 2017 9:18AM - 9:30AM |
H13.00003: A multi-layered active target for the study of neutron-unbound nuclides at NSCL Jessica Freeman, Paul Gueye, Thomas Redpath The characteristics of neutron-unbound nuclides were investigated using a multi-layered Si/Be active target designed for use with the MoNA/LISA setup at the National Superconducting Cyclotron (NSCL). The setup consists of the MoNA/LISA arrays (for neutron detection) and a superconducting sweeper magnet (for charged separation) to identify products following the decay of neutron unbound states. The segmented target consisted of three 700 mg/cm2 beryllium targets and four 0.14 mm thick 62x62 mm2 silicon detectors. As a commissioning experiment for the target the decay of two-neutron unbound 26O populated in a one-proton removal reaction from a radioactive 27F beam was performed. The 27F secondary radioactive beam from the NSCL's Coupled Cyclotron Facility was produced from the fragmentation of a 140 MeV/u 48Ca beam incident on a thick beryllium target and then cleanly selected by the A1900 fragment separator. The energy loss and position spectra of the incoming beam and reaction products were used to calibrate the Silicon detectors to within 1.5{\%} in both energy and position. A dedicated Geant4 model of the target was developed to simulate the energy loss within the target. A description of the experimental setup, simulation work, and energy and position calibration will be presented. [Preview Abstract] |
Sunday, January 29, 2017 9:30AM - 9:42AM |
H13.00004: The new Digital Data Acquisition System for MoNA-LISA Dayah Chrisman, Paul DeYoung The Modular Neutron Array (MoNA) and the Large multi-Institutional Scintillator Array (LISA) at the National Superconducting Cyclotron Laboratory (NSCL) are used to detect neutrons emitted during the decay of exotic nuclei near the neutron dripline. The arrays consist of 288 10cm x 10cm x 2m long plastic scintillation detectors coupled to photomultipliers at each end. The Time of Flight (TOF) of these neutrons determines the neutron energy, which is needed to find the decay energy of the exotic nuclei. A Digital Data Acquisition System (DDAS) based on the XIA PXI modules is being developed to read out and record the signals of the MoNA-LISA scintillation detectors. A 500 Mega Samples per Second (MSPS) PXI module was used to test the time and energy resolution as it compares to the existing analog DAQ setup. [Preview Abstract] |
Sunday, January 29, 2017 9:42AM - 9:54AM |
H13.00005: G4MoNA - A Geant4 Simulation for unbound nuclides detected with MoNA/LISA Paul Gueye, Jessica Freeman, Nathan Frank The MoNA Collaboration has conducted a plethora of experiments to study unbound nuclei near the neutron dripline using the invariant mass technique since 2005. These experiments used a variety of secondary beams from the Coupled Cyclotron Facility of the National Superconducting Cyclotron Laboratory. The experimental setup consists of a large gap superconducting Sweeper magnet for charged fragments separation and the MoNA/LISA neutron detector arrays for neutron detection. Recently, a multi-layered Si/Be segmented target consisting of three 700 mg/cm{\$}\textasciicircum 2{\$} thick {\$}\textasciicircum 9{\$}Be slabs and four 140\textasciitilde {\$}$\backslash $mu{\$}m Si detectors were added to the setup. This target improves the resolution of the reconstructed decay energy spectra of the unbound nuclides. The Geant4 Monte Carlo simulation toolkit was used to develop a complete realistic model of the setup ~including a new class to treat the decay of unbound nuclei, the Si/Be segmented target, the MoNA/LISA and the charged fragments detector systems. Comparison between simulated and experimental data will be presented. [Preview Abstract] |
Sunday, January 29, 2017 9:54AM - 10:06AM |
H13.00006: High-rate axial-field ionization chamber for particle identification of Radioactive beams Romualdo Desouza, Justin Vadas, Varinderjit Singh, G. Visser, A. Alexander, S. Hudan, J. Huston, B. Wiggins, A. Chbihi, M. Famiano, M. Bischak The design, construction and performance characteristics of a simple axial-field ionization chamber suitable for identifying ions in a radioactive beam are presented. The detector is optimized for use with low-energy radioactive beams ($<$) 5 MeV/A. A fast charge sensitive amplifier (CSA) integrated into the detector design is also described. Coupling this fast CSA to the axial field ionization chamber produces an output pulse with a rise-time of 60 to 70 ns and a fall time of 100 ns, making the detector capable of sustaining a relatively high rate while providing a time resolution of 6 to 8 ns. Tests with an $\alpha$ source establish the detector energy resolution as $\approx$8$\%$ for an energy deposit of $\approx$3.5 MeV. Beam tests indicate that the detector is an effective tool for the characterization of low-energy radioactive beams at beam intensities up to 3 x 10$^5$ ions/s. [Preview Abstract] |
Sunday, January 29, 2017 10:06AM - 10:18AM |
H13.00007: Development of a flexible circuit board for low-background experiments Alan Poon, Paul Barton, Ankur Dhar, Joern Larsen, James Loach Future underground rare-event search experiments, such as neutrinoless double-beta decay searches, have stringent requirements for the radiopurity of materials placed near the active detector medium. Parylene is a polymer that has a high chemical purity and the vapor deposition process by which it is laid down tends to purify it further. In this talk the technique to fabricate a low-mass, flexible circuit board, with conductive traces photoligthographically patterned on a parylene substrate, is discussed. The performance of a proof-of-principle temperature sensor is presented. [Preview Abstract] |
Sunday, January 29, 2017 10:18AM - 10:30AM |
H13.00008: Detection of far ultraviolet radiation by wavelength-shifting tetraphenyl butadiene Joshua R. Graybill, Chandra B. Shahi, Michael C. Coplan, Robert E. Vest, Alan K. Thompson, Charles W. Clark Far ultraviolet (FUV) radiation has been used in low-energy particle physics\footnote{V. Chepel and H. Ara\'{u}jo, J. Inst. {\bf 8}, R04001 (2013).}, dark matter searches\footnote{E. Aprile, {\em et al.}, Astroparticle Phys. {\bf 35}, 573 (2012).}, and neutron detection\footnote{J. C. McComb, {\em et al.}, J. Appl. Phys. {\bf 115}, 144504 (2014).}, in conjuction with wavelength-shifting (WLS) materials. Tetraphenyl butadiene (TPB) has been found to have high conversion efficiency compared to other WLS fluorophores. We have spin-coated TPB films with high uniformity and optical quality on glass windows and compared the absolute efficiencies of both the spin-coated and vapor deposited films over the incident radiation wavelengths $120 \, \mathrm{nm} < \lambda < 400 \, \mathrm{nm}$ at the NIST SURF III Synchrotron Ultraviolet Radiation Facility. While photon efficiencies of 0.7 and 1.35, have been reported\footnote{V. M. Gehman, {\em et al.}, Nuc. Instr. Meth. Phys. Res. A {\bf 654}, 116 (2011).}, our preliminary results indicate the absolute efficiencies to be between 0.2 and 0.5. The Neutron Observatory\footnote{{\tt http://j.mp/N3utr0n}} was used to compare conversion efficiencies in well-characterized detector platforms. [Preview Abstract] |
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