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 HD: Nuclear Instrumentation II |
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Chair: Jenna Smith, Reed College Room: Salon 4 |
Friday, October 27, 2017 8:30AM - 8:42AM |
HD.00001: Hybrid Array of Gamma Ray Detectors (HAGRiD) X. Pereira-Lopez, K. Smith, T. Baugher, S. Burcher, A.B. Carter, K.A. Chipps, J.A. Cizewski, M. Febbraro, R. Grzywacz, K.L. Jones, S. Munoz, S.D. Pain, S.V. Paulauskas, A.K. Ratkiewicz, K.T. Schmitt, C. Thornsberry, R. Toomey, M. Vostinar, D. Walter, H. Willoughby Transfer reactions and beta-decay studies can benefit from measuring gamma rays in coincidence with charged particles. In order to address this purpose, HAGRiD was designed as a highly modular, highly efficient array of LaBr3(Ce) detectors with, currently, 27 2" and 10 3" crystals available. The LaBr3(Ce) crystals provide better resolution and intrinsic efficiency than NaI crystals while offering more flexibility than Ge detectors due to the reduced infrasctructure required. This flexibility allows to couple HAGRiD with very different detectors, such as the ORRUBA silicon array and the VANDLE neutron array, proven by successful experiments carried out at NSCL, Notre Dame and HBRIF. The advantages offered by HAGRiD and the efforts devoted to optimize its perfomance will be discussed in this presentation. [Preview Abstract] |
Friday, October 27, 2017 8:42AM - 8:54AM |
HD.00002: High-Resolution and -Efficiency Gamma-Ray Detection for the FRIB Decay Station Hannah Grover, Kyle Leach, Connor Natzke As we push our knowledge of nuclear structure to the frontier of the unknown with FRIB, a new high-efficiency, -resolution, and -sensitivity photon-detection device is critical. The FRIB Decay Station Collaboration is working to create a new detector array that meets the needs of the exploratory nature of FRIB by minimizing cost and maximizing efficiency. GEANT4 simulations are being utilized to combine detectors in various configurations to test their feasibility. I will discuss these simulations and how they compare to existing simulations of past-generation decay-spectroscopy equipment. [Preview Abstract] |
Friday, October 27, 2017 8:54AM - 9:06AM |
HD.00003: Using HGe and LaBr detectors in gamma-gamma-coincidence applications. Eva Kasanda, Dennis Muecher, Vinzenz Bildstein, Joseph Turko, Deyvid Mitkov In the past decade, nuclear detectors have been subject to increasing demands for accuracy and efficiency. High Purity Germanium (HPGe) detector arrays are an excellent example of a high precision detector born of this demand, as they boast an energy resolution of below 0.1% at 1 MeV. While the superior energy resolution of HPGe detectors is ideal for gamma-gamma coincidence analysis, the relatively poor timing resolution results in increased random coincidences and decreased SNR. Instead, Lanthanum Bromide (LaBr$_3$) scintillators have a much faster response (100 ps). They allow for precise time gating in gamma-gamma coincidence analysis, but can produce spectra with ill-defined peaks due to their low energy resolution. We use Geant4 and ROOT to investigate a combination of LaBr$_3$ and HPGe detectors in the measurement of fusion-evaporation reactions, resulting in an improved SNR when compared to spectra obtained by measuring with LaBr$_3$ or HPGe detectors on their own. This technique could provide a significant improvement to experiments using fast external triggers, and environments with strongly competing channels. We will demonstrate the application of this method for the range verification in ion beam radiation therapy, and in the identification of superheavy elements. [Preview Abstract] |
Friday, October 27, 2017 9:06AM - 9:18AM |
HD.00004: Design and calibration GODDESS, a particle-$\gamma$ spectrometer Heather Garland, Jolie Cizewski, Alex Lepailleur, Steven Pain, David Walter, Harry Sims The ability to detect $\gamma$-rays and particles in coincidence is advantageous to performing high-resolution studies of exotic nuclei. It is experimentally challenging to retain detector optimization when combining $\gamma$-ray detectors, which typically need to be in close configuration for efficiency, with particle detectors that require greater target to detector distances to maintain angular resolution. GODDESS (Gammasphere ORRUBA: Dual Detectors for Experimental Structure Studies) --- allows a full implementation of the Oak Ridge Rutgers University Barrel Array within the cavity inside Gammasphere. The ORRUBA detectors consist of position-sensitive silicon strip detectors supplemented with annular silicon strip detectors at forward and backward angles. The full compliment of ORRUBA covers $>$70\% in azimuthal angle over $\sim$15 to 165 deg polar angle, with $\sim$1 deg polar resolution throughout. These specifications allow the use of GODDESS for a wide range of direct reaction studies, such as transfer reactions and inelastic scattering. This talk will focus on design and calibration of GODDESS detectors and the geometric analysis of ORRUBA data. [Preview Abstract] |
Friday, October 27, 2017 9:18AM - 9:30AM |
HD.00005: Effects of a Realistic Beam Profile on the Extraction of $\gamma\gamma$ Angular Correlations with GRIFFIN Connor Natzke, Kyle Leach, Adam Garnsworthy, Andrew MacLean, Jenna Smith, Carl Svensson The GRIFFIN spectrometer at TRIUMF-ISAC is a powerful device for measuring gamma-gamma angular correlations following the decay of rare isotopes. GEANT4 simulations are essential in understanding the effects of detector shape, finite source and detector size, and source position. In this work, simulations exploring the sensitivity to a finite source radius and an off-centre source position on GRIFFIN's ability to accurately measure gamma-gamma angular correlations have been performed. The off-centre simulations provide insight into the beta decay of radioactive ions implanted onto a moving tape, which can be constantly moved through the chamber to prevent the build-up of long-lived radioactive daughter nuclei. The simulations indicate that a source radius or displacement of less than 1 cm has a minimal effect on the extracted gamma-gamma angular correlations. However, larger radii or offsets introduce significant deviations in the shape of measured angular correlations. The findings of these investigations will be discussed, along with ongoing simulation work of using the GRIFFIN array for Compton polarimetry measurements. [Preview Abstract] |
Friday, October 27, 2017 9:30AM - 9:42AM |
HD.00006: Characterization of 3x3x10 cm$^{\mathrm{3}}$ CsI Crystals for Nuclear Physics Experiments Sean Sweany, William Lynch, Betty Tsang, Zbigniew Chajecki, Kyle Brown, Pierre Morfouace, Zhu Kuan, Jacob Crosby, Corinne Anderson, Suhas Kodali The symmetry energy portion of the nuclear equation of state is currently poorly constrained in asymmetric nuclear matter. The momentum dependence of the symmetry energy potential causes a reduction in the nucleon masses causing a splitting between the neutron and proton effective masses. From transport simulations, n/p spectral ratios are shown to be a good observable for studying this effective mass splitting. Arrays of silicon strip detectors backed by scintillator crystals are an effective way of detecting and identifying charged particles over a large range of angles. Recently the HiRA group at the NSCL has finished updating of the HiRA array with 10 cm CsI crystals, HiRA10. The longer CsI crystals allow for higher energy particles to be measured. The doping gradient of thallium along with side and surface treatment of CsI can cause nonuniformity in light output of the crystals, therefore the crystals must characterized before use. For characterization, the crystals were scanned using a collimated Am241 source in a grid pattern of 64 points per crystal. The design of HiRA10 as well as the results of the tests for crystal uniformity will be presented in this talk. [Preview Abstract] |
Friday, October 27, 2017 9:42AM - 9:54AM |
HD.00007: Status of CHICOx upgrade Ching-Yen Wu A proposal was submitted and approved by DOE/NP to upgrade CHICO2 to CHICOx, by resizing the detector chamber and reconfiguring the pixelated position-sensing board, to be fully integrated into GRETA. The recently completed CHICO2, a two-dimensional pixelated parallel-plate avalanche counter, has achieved a position resolution matching to that of GRETA and has been integrated successfully into GRETINA. The science campaign in FY14/15 at ANL using GRETINA/CHICO2 has produced two publications in PRL and two in PLB in addition to a technical article in NIMA on CHICO2. We believe this proposed upgrade will fully exploit the sensitivity of GRETA for the nuclear gamma-ray spectroscopic study using the quasi-elastic reactions such as the sub-barrier Coulomb excitation method and few-nucleon transfer reaction as well as the deep-inelastic reaction. GRETA/CHICOx will be a unique instrument providing the highest sensitivity in exploring the evolution of shell structure and collectivity for neutron-rich nuclei near the r-process path. The upgrade plan together with the timeline will be presented. This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics. Work at LLNL is supported by the U.S. DOE under Contracts No. DE-AC52-07NA27344. [Preview Abstract] |
Friday, October 27, 2017 9:54AM - 10:06AM |
HD.00008: Simulation and Automation of Microwave Frequency Control in Dynamic Nuclear Polarization for Solid Polarized Targets Gonaduwage Perera, Ian Johnson, Dustin Keller Dynamic Nuclear Polarization (DNP) is used in most of the solid polarized target scattering experiments. Those target materials must be irradiated using microwaves at a frequency determined by the difference in the nuclear Larmor and electron paramagnetic resonance (EPR) frequencies. But the resonance frequency changes with time as a result of radiation damage. Hence the microwave frequency should be adjusted accordingly. Manually adjusting the frequency can be difficult, and improper adjustments negatively impact the polarization. In order to overcome these difficulties, two controllers were developed which automate the process of seeking and maintaining the optimal frequency: one being a standalone controller for a traditional DC motor and the other a LabVIEW VI for a stepper motor configuration. Further a Monte-Carlo simulation was developed which can accurately model the polarization over time as a function of microwave frequency. In this talk, analysis of the simulated data and recent improvements to the automated system will be presented. [Preview Abstract] |
Friday, October 27, 2017 10:06AM - 10:18AM |
HD.00009: 12-bit 32 channel 500MS/s low-latency ADC for particle accelerators real-time control. Anton Karnitski, Dalius Baranauskas, Denis Zelenin, Gytis Baranauskas, Alexander Zhankevich, Chris Gill Particle beam control systems require real-time low latency digital feedback with high linearity and dynamic range. Densely packed electronic systems employ high performance multichannel digitizers causing excessive heat dissipation. Therefore, low power dissipation is another critical requirement for these digitizers. A described 12-bit 500MS/s ADC employs a sub-ranging architecture based on a merged sample {\&} hold circuit, a residue C-DAC and a shared 6-bit flash core ADC. The core ADC provides a sequential coarse and fine digitization featuring a latency of two clock cycles. The ADC is implemented in a 28nm CMOS process and consumes 4mW of power per channel from a 0.9V supply (interfacing and peripheral circuits are excluded). Reduced power consumption and small on-chip area permits the implementation of 32 ADC channels on a 10.7mm$^{\mathrm{2}}$ chip. The ADC includes a JESD204B standard compliant output data interface operated at the 7.5Gbps/ch rate. To minimize the data interface related time latency, a special feature permitting to bypass the JESD204B interface is built in. [Preview Abstract] |
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