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 FD: Nuclear Instrumentation I |
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Chair: Rusty Towell, Abilene Christian University Room: Salon 4 |
Thursday, October 26, 2017 4:00PM - 4:12PM |
FD.00001: Commissioning the EMMA spectrometer at TRIUMF Nicholas Esker, Barry Davids, Martin Alcorta, Kevan Hudson, Matthew Williams The ElectroMagnetic Mass Analyser (EMMA) is a new experimental facility at TRIUMF. Located after the ISAC-II accelerator, EMMA is a symmetric QQEDEQQ-type mass spectrometer capable of separating the recoiling nuclear reaction products from the beam. With the low emittance radioactive beams delivered from ISAC-II at energies up to at least 6.5 A MeV, EMMA is designed for fusion evaporation and transfer reactions of interest in nuclear structure and astrophysics studies. A vacuum mode separator, EMMA disperses ions according to mass/charge in the focal plane. During a successful commissioning run in Dec. 2016, the dispersion and resolving power were measured and found to agree with ion optical calculations. In the future, cross section measurements and decay spectroscopy studies will be performed using a parallel grid avalanche counter, Si implantation detectors, and external high purity Ge detectors at the focal plane. When coupled with the TIGRESS $\gamma$-ray detector array, in-beam spectroscopy at the target will also be available. Today, we present the current status of the EMMA mass spectrometer as it continues to undergo commissioning and begin its experimental life. [Preview Abstract] |
Thursday, October 26, 2017 4:12PM - 4:24PM |
FD.00002: Off-line commissioning of the University of Notre Dame Multi-Reflection Time-of-Flight mass spectrograph Maxime Brodeur, James Kelly, Biying Liu, Brad Schultz The production of exotic nuclei at the vicinity of the N = 126 peak of the rapid-neutron capture process as for a long time pose a challenge. A new facility currently under construction at Argonne National Laboratory aims at undertaking the challenge by producing these difficult nuclei via deep-inelastic reactions. The facility will first include a large-volume gas cell to collect and thermalize the reaction products. Then, upon extraction from the gas cell and radio-frequency ion guide, the ion beam will be separated by a high-resolution mass separator magnet and a multi-reflection time-of-flight mass spectrometer (MR-ToF) for the removal of isobaric contamination. This MR-ToF has been built and is being commissioned in an offline test setup at the University of Notre Dame. The commissioning results and off-line performance of the MR-ToF will be presented. [Preview Abstract] |
Thursday, October 26, 2017 4:24PM - 4:36PM |
FD.00003: Updates to the development to the Solenoid Spectrometer for Nuclear Astrophysics (SSNAP) at Notre Dame Jacob Allen, D. W. Bardayan, D. Blankstein, E. Garcia, M. R. Hall, O. Hall, J. J. Kolata, P. D. O'Malley, F. D. Becchetti, S. T. Marley, S. D. Pain Construction of the Solenoid Spectrometer for Nuclear Astrophysics (SSNAP) has been progressing in preparation for studies of nucleon transfer reactions at the University of Notre Dame. As a helical orbit spectrometer, it will improve our ability to measure nucleon transfer reactions. These studies facilitate extraction of nuclear structure information critical to determining reaction rates in many astrophysical processes, such as novae bursts, and many other natural processes. SSNAP will provide quick, accurate measurements to many nuclear properties, such as nuclear cross sections, branching ratios, and nuclear spectroscopy. SSNAP uses position-sensitive silicon detectors set on-axis in the second solenoid of \textit{TwinSol}. In this presentation, updates to the progress of SSNAP will be presented as well was as future plans to its development will be provided. This work is supported by the National Science Foundation and the Joint Institute for Nuclear Astrophysics. [Preview Abstract] |
Thursday, October 26, 2017 4:36PM - 4:48PM |
FD.00004: Development of a $\beta$-delayed charged particle detector for studying novae and x-ray bursts Moshe Friedman, Tamas Budner, Marco Cortesi, Madison Harris, Molly Janasik, David Perez-Loureiro, Emmanuel Pollaco, Michael Roosa, Pranjal Tiwari, Chris Wrede, John Yurkon Classical novae and type I x-ray bursts are energetic and common thermonuclear astrophysical explosions. However, our ability to understand these events is limited by the lack of comprehensive nuclear data on proton-rich nuclei. Specifically, constraining the $^{30}P(p,\gamma)^{31}S$ and $^{15}O(\alpha,\gamma)^{19}Ne$ reaction rates has been found to be crucial to the understanding of nucleosynthesis and energy generation in these events. As direct measurements of these reactions are not technically feasible at the present time, a gas-filled detector of $\beta$-delayed charged particles has been designed and built to measure the $^{31}Cl(\beta p)^{30}P$ and $^{20}Mg(\beta p \alpha)^{15}O$ decay sequences at NSCL, providing an indirect probe of resonances in the radiative capture reactions above. The detector is coupled with the Segmented Germanium Array (SeGA) to enable coincidence γ detection, as an additional probe of interaction details and for normalization purposes. The first phase of the detector functions as a proton calorimeter and it is currently being tested and optimized. We will describe the technical status of Phase I, including the concept, simulations, design, assembly, and first offline measurements using radioactive sources. [Preview Abstract] |
Thursday, October 26, 2017 4:48PM - 5:00PM |
FD.00005: Multi-layer Thick Gas Electron Multiplier (M-THGEM) Simulations at Low Pressure for High-Gain Operation Adam Fritsch, Marco Cortesi, Wolfgang Mittig The Multi-layer Thick Gaseous Electron Multiplier (M-THGEM) is a novel hole-type gaseous electron multiplier produced by multi-layer printed circuit board technology; it consists of a densely perforated assembly of multiple insulating substrate sheets sandwiched between thin metallic-electrode layers\footnotemark. The electron avalanche processes occur along the successive multiplication stages within the M-THGEM holes, under the action of strong dipole fields resulting from the application of suitable potential differences between the electrodes. Using ANSYS Maxwell and Garfield, Monte Carlo simulations have been performed to find geometries that maximize the achievable gain, electron collection efficiency, ion feedback, energy resolution of M-THGEM devices at low pressure with pure gases. Comparisons of the calculations with measurements of a prototype device are ongoing. Preliminary results will be presented. \footnotetext[1]{Cortesi \textit{et al.}, arXiv:1606.07314v1 [physics.ins-det]} [Preview Abstract] |
Thursday, October 26, 2017 5:00PM - 5:12PM |
FD.00006: FENRIS Focal-plane Detector Package on the TUNL Split-pole Spectrograph Caleb Marshall, Kiana Setoodehnia, Federico Portillo, Richard Longland The Facility for Experiments of Nuclear Reactions in Stars (FENRIS) uses an Enge split-pole spectrograph to measure reactions of interest for astrophysics. Magnetic spectrographs focus particles onto a plane according to their charge to mass ratio and kinetic energy. A detector positioned at this focal plane needs to be able to measure the spatial separation of focused particle groups in order to extract their physical quantities. The FENRIS focal plane detector, in particular, must provide both accurate position measurements and particle identification for reaction products. Our detector package consists of two position sensitive gas proportionality counters, a gas proportionality energy loss section, and a residual energy scintillator. Our design choices and fabrication techniques for each of these sections has produced a detector that achieves the previously stated requirements, eases routine maintenance, and is flexible enough to accommodate future upgrades. Calibration and characterization experiments have been carried out, and their results have validated the detector design. [Preview Abstract] |
Thursday, October 26, 2017 5:12PM - 5:24PM |
FD.00007: Target characterization for one percent precision Kyle Schmitt Reaction cross section measurements are a necessary input for models of fission application technologies. Precision measurements are currently underway to reduce design margin requirements, which depend on the uncertainties for these measured cross sections. The Neutron Induced Fission Fragment Tracking Experiment (NIFFTE) collaboration has undertaken to measure the Pu-239(n,f) cross section in ratio to the U-235(n,f) cross section in the fast neutron energy regime with a total systematic uncertainty of 1{\%}. To achieve this level of uncertainty, it is necessary to characterize beam, target, and detector with unprecedented precision. One important challenge for this measurement is to characterize Pu-239 and U-235 samples with spontaneous alpha decay rates that differ by a factor of 10,000, each to a precision less than 1{\%}. A low-geometry alpha counting setup has been developed for this purpose. Characterization methods and results will be presented. [Preview Abstract] |
Thursday, October 26, 2017 5:24PM - 5:36PM |
FD.00008: High Precision Measurement of the Coherent Scattering length of n-$^{4}$He Robert Haun, Michael Huber, Tim Black, Dimitry Pushin, Chandra Shahi, Ben Heacock, Muhammad Arif, Fred Wietfeldt Neutron interferometry provides a tool for high-precision measurement of scattering lengths for gaseous samples. Examples include measurements of the coherent scattering lengths ($b_{c}$) of $^{1}$H, $^{2}$H, $^{3}$He and the incoherent scattering length of $^{3}$He. Neutron scattering lengths of light nuclei provide useful tests of nuclear potential models and may serve as inputs for nuclear effective field theories. Our current work is to measure $b_{c}$ of n-$^{4}$He to the $10^{-3}$ relative precision level. We use a perfect silicon neutron interferometer which splits the matter wave of a single neutron, via Bragg diffraction, into two coherent separated paths and recombines them. A relative phase shift, directly proportional to $b_{c}$, is introduced by the gas sample. The data from this experiment have been collected and we will report a preliminary result. This work is supported by the National Science Foundation. [Preview Abstract] |
Thursday, October 26, 2017 5:36PM - 5:48PM |
FD.00009: Systematic Effects in Precision Measurements Performed using a Neutron Interferometer M.G. Huber, M. Arif, T.C. Black, R.W. HAUN, B. Heacock, D.A. Pushin, C.B. Shahi, F.E. WIETFELDT Coherent neutron scattering lengths and cross sections for various isotopes have been measured using several different techniques including transmission, gravity refractometry, and perfect crystal neutron interferometry (NI). Neutron interferometry, analogous to an optical Mach-Zehnder interferometer, coherently separates a neutron beam into a reference path and sample path. The relative phase between these two paths is measured by an interference pattern. Neutron interferometry has been the preferred method for precision scattering length measurements due to its notable phase sensitivity and the ability to measure both gaseous and solid isotopes. As greater precision is sought, systematic effects become ever more challenging. Recently, we have found a systematic phase shift that we call the `shadow' phase. This `shadow' phase is caused by the 10 mK temperature different between that of the interferometer crystal blades and that of the sample, causing a nonlinear variation in the interferometer's intrinsic phase $\Delta \phi_{\mathrm{0}}$. We have studied this effect and will discuss how to effectively mitigate it. The shadow phase systematic is relevant to precision measurements on weakly interacting isotopes. [Preview Abstract] |
Thursday, October 26, 2017 5:48PM - 6:00PM |
FD.00010: Analysis of high-speed rotating flow inside gas centrifuge casing Dr. Sahadev Pradhan The generalized analytical model for the radial boundary layer inside the gas centrifuge casing in which the inner cylinder is rotating at a constant angular velocity $\Omega $\textit{\textunderscore i} while the outer one is stationary, is formulated for studying the secondary gas flow field due to wall thermal forcing, inflow/outflow of light gas along the boundaries, as well as due to the combination of the above two external forcing. The analytical model includes the sixth order differential equation for the radial boundary layer at the cylindrical curved surface in terms of master potential ($\chi )$, which is derived from the equations of motion in an axisymmetric $(r - z)$ plane. The linearization approximation is used, where the equations of motion are truncated at linear order in the velocity and pressure disturbances to the base flow, which is a solid-body rotation. Additional approximations in the analytical model include constant temperature in the base state (isothermal compressible Couette flow), high aspect ratio (length is large compared to the annular gap), high Reynolds number, but there is no limitation on the Mach number. The discrete eigenvalues and eigenfunctions of the linear operators (sixth-order in the radial direction for the generalized analytical equation) are obtained. The solutions for the secondary flow is determined in terms of these eigenvalues and eigenfunctions. These solutions are compared with direct simulation Monte Carlo (DSMC) simulations and found excellent agreement (with a difference of less than 15{\%}) between the predictions of the analytical model and the DSMC simulations, provided the boundary conditions in the analytical model are accurately specified. [Preview Abstract] |
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