Bulletin of the American Physical Society
APS April Meeting 2017
Volume 62, Number 1
Saturday–Tuesday, January 28–31, 2017; Washington, DC
Session S13: Minisymposium: Precision Measurements in Nuclear Physics II |
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Sponsoring Units: DNP Chair: Maxime Brodeur, University of Notre Dame Room: Roosevelt 5 |
Monday, January 30, 2017 1:30PM - 1:42PM |
S13.00001: Beta-delayed neutron spectroscopy using ion traps Barbara Wang, A. Czeszumska, K. Siegl, S. Caldwell, A. Aprahamian, M. Burkey, J. Clark, A. Levand, S. Marley, G. Morgan, E. Norman, A. Nystrom, R. Orford, S. Padgett, A. Perez Galvan, G. Savard, N. Scielzo, K. Sharma, S. Strauss Trapped radioactive ions suspended in vacuum allow for a new way to perform beta-delayed neutron spectroscopy. Decay branching ratios and energy spectra of the emitted neutrons are inferred from a measurement of the nuclear recoil, thereby circumventing the many limitations associated with direct neutron detection. Beta-delayed neutron measurements were carried out for \textsuperscript{137-138,140}I, \textsuperscript{134-136}Sb, and \textsuperscript{144-145}Cs at the Californium Rare Isotope Breeder Upgrade (CARIBU) facility at Argonne National Laboratory. The data collected are needed in many fields of basic and applied science such as nuclear energy, nuclear astrophysics, and stockpile stewardship. Results for the isotopes \textsuperscript{135-136}Sb and \textsuperscript{140}I will be presented. Supported by NSF under PHY-1419765, and U.S. DOE under NEUP 13-5485, DE-AC02- 06CH11357 (ANL), DE-AC52- 07NA27344 (LLNL), and DE-NA0000979 (NNSA). [Preview Abstract] |
Monday, January 30, 2017 1:42PM - 1:54PM |
S13.00002: Studies of Beta-Delayed Neutron Emission using Trapped Ions Kevin Siegl, A. Aprahamian, N.D. Scielzo, G. Savard, J.A. Clark, A.F. Levand, M. Burkey, S. Caldwell, A. Czeszumska, T.Y. Hirsh, K. Kolos, S.T. Marley, G.E. Morgan, E.B. Norman, A. Nystrom, R. Orford, S. Padgett, A. Pérez Galván, K.S. Sh, S.Y. Strauss, B.S. Wang Using a radio-frequency quadrupole ion trap to confine radioactive ions allows indirect measurements of beta-delayed neutron (BDN) emission. By determining the recoil energy of the beta-decay daughter ions it is possible to study BDN emission, as the neutron emission can impart a significantly larger nuclear recoil than from beta-decay alone. This method avoids most of the systematic uncertainties associated with direct neutron detection but introduces dependencies on the specifics of the decay and interactions of the ion with the RF fields. The decays of seven BDN precursors were studied using the Beta-decay Paul Trap (BPT) to confine fission fragments from the Californium Rare Isotope Breeder Upgrade (CARIBU) facility at Argonne National Laboratory. The analysis of these measurements and results for the branching ratios and neutron energy spectra will be presented. [Preview Abstract] |
Monday, January 30, 2017 1:54PM - 2:06PM |
S13.00003: Searching for Tensor Currents in the Weak Interaction Using $^{8}$Li $\beta$ Decay M.T. Burkey, G. Savard, R.E. Segel, J.A. Clark, N.D. Scielzo, A.T. Gallant, K. Kolos, S.W. Padgett, B.S. Wang, T. Hirsh, E. Heckmaier, S.T. Marley, G. Morgan, R. Orford, K.S. Sharma The weak interaction is framed in the Standard Model with a pure vector-axial vector structure. A high-precision measurement of the $\beta-\nu$ correlation coefficient (a$_{\beta\nu}$) could reveal contributions from tensor or scalar currents and give insight into new physics. We utilize stopped $^{8}$Li in the Beta decay Paul Trap (BPT) at Argonne National Lab to measure a$_{\beta\nu}$. The BPT is surrounded on 4 sides with double-sided silicon strip detectors backed by plastic scintillator detectors, which allow the kinematics of the $^{8}$Li decay products to be over-constrained. A previous measurement done by our collaboration resulted in the first improvement in over 50 years to the tensor limit of a$_{\beta\nu}$ in a nuclear setting and was recently published in PRL. We have since upgraded our system and obtained over ten times our previous statistics. Our goal is to achieve a limit of a$_{\beta\nu}$ with an uncertainty of ~0.001. Analysis is ongoing. [Preview Abstract] |
Monday, January 30, 2017 2:06PM - 2:18PM |
S13.00004: Precision measurements in $^{\mathrm{\mathbf{20}}}$\textbf{F beta decay} Maximilian Hughes, Oscar Naviliat-Cuncic, Paul Voytas, Elizabeth George, Stan Paulauskas, Xueying Huyan Precision measurements of the shape of the beta particle energy spectrum provide a sensitive window to search for new interactions beyond the standard model. The decay of $^{\mathrm{20}}$F offers an attractive system due to the simple decay scheme for a coincidence measurement. A beam of $^{\mathrm{20}}$F ions, produced at the National Superconducting Cyclotron Laboratory, was implanted into a beta-detector. A gamma-ray detection system surrounded the beta detector to detect the beta-delayed gammas in coincidence to reduce the background. Preliminary analysis of these data focus on the half-life of $^{\mathrm{20}}$F due to the statistical inconsistency of previous work. Monte Carlo simulations are ongoing to analyze the shape of the beta energy spectrum. Results of the analysis of the half-life will be presented. [Preview Abstract] |
Monday, January 30, 2017 2:18PM - 2:30PM |
S13.00005: Overview of Neutron Beta Correlation Parameter Analysis from the UCNA Experiment Xuan Sun The UCNA experiment, operated at the Ultracold Neutron Facility at the Los Alamos Neutron Science Center, uses ultracold neutrons (UCN) to measure the free-neutron $\beta$-decay correlation parameter, $A$, between the neutron spin direction and $\beta$ momentum direction. Measurements of $A$ presently provide the most precise value of $g_A/g_V$, the ratio of the axial-vector and vector coupling constants of the nucleon weak interaction. The UCNA experiment has previously analyzed and reported on a measurement of $A$ from a 2010 dataset. Additional datasets were also taken in 2011-2012 and 2012-2013. Improvements in energy calibrations, polarimetry, and statistics are expected to provide a more precise measurement of $A$ from the later datasets. We provide a review of the experimental apparatus and give an updated overview on the state of the 2011-2012 and 2012-2013 dataset analysis with respect to the $A$ measurement. [Preview Abstract] |
Monday, January 30, 2017 2:30PM - 2:42PM |
S13.00006: Performance of the New Los Alamos UCN Source and Implications for Future Experiments Mark Makela The Los Alamos Ultracold Neutron (UCN) source was replaced during this past summer and has been commissioned during the last few months. The new source is the result of lessons learned during the 10 year operation of the first UCN source and extensive Monte Carlo analysis. The new source is a spallation driven source based on a solid deuterium UCN moderator similar the previous one. This talk will present an overview of the new source design and the results of commissioning tests. The talk will conclude with a brief overview of the implications of source performance on the neutron lifetime and LANL nEDM experiments. [Preview Abstract] |
Monday, January 30, 2017 2:42PM - 2:54PM |
S13.00007: Overview of the n3He Experiment and Target Chamber Mark McCrea The n3He Experiment aims to measure the parity-violating asymmetry in the direction of proton emission relative to the initial neutron polarization direction in the reaction $\vec{n}+^3He \rightarrow T+p+ 765\,\mathrm{keV}$ to a high precision. The size of the asymmetry is estimated to be in the range $-9.5-2.5\times 10^{-8}$, and our goal statistical accuracy is $2\times 10^{-8}$. The experiment ran at the Spallation Neutron Source with data taking completing at the end of 2015. The experiment used a Helium-3 ionization chamber as the combined target and detector. Data analysis is underway and is currently in an advanced stage [Preview Abstract] |
Monday, January 30, 2017 2:54PM - 3:06PM |
S13.00008: Simulation of ion chamber signals in the $n+^{3}$He$\rightarrow p+t$ experiment Christopher Coppola The parity violating proton directional asymmetry from the capture of polarized neutrons on $^{3}$He was measured with a pulsed neutron beam at the Spallation Neutron Source at Oak Ridge National Laboratory. The target is an ion chamber with $^{3}$He at 0.476 atmosphere. Signal wires in the chamber have different sensitivities to the physics asymmetry, depdendent on their location and the the configuration of the experiment. These geometry factors must be determined by simulation. In addition, simulation estimates the statistical precision of the experiment, optimizes configuration variables, and assists with systematic analysis. To achieve the most accurate simulation of the detector signals, a custom simulation was written in C++ using weighted variables and taking advantage of parallel execution. The phsyics inputs to the simulation came from measurements of the neutron phase space, ENDF cross sections, and PSTAR ionization data. A cell model was applied to combine this physics to produce an accurate simulation of the experimental data. This simulation can be used to calculate accurate and tunable geometry factors, and to produce desired quanities for use in optimization and analysis. [Preview Abstract] |
Monday, January 30, 2017 3:06PM - 3:18PM |
S13.00009: Polarized Electron Source for the MOLLER Experiment Caryn Palatchi The MOLLER experiment at Jefferson Laboratory will be part of a new generation of ultra high precision electroweak experiments. It will measure the Moller (electron-electron scattering) parity-violating asymmetry, providing an unprecedented precision on the electroweak mixing angle. To achieve such small uncertainties, innovative techniques in the electron source are required to switch the beam helicity more quickly than previously achievable. The key technology is the Pockels cell in the laser optics of the polarized electron source. RTP crystals, which do not suffer from piezo-electric ringing, have been demonstrated to achieve almost an order of magnitude faster transition times than commonly used KD*P crystal cells. This talk will detail the design modifications made to the RTP cell in order to achieve beam quality which is comparable to traditional KD*P controlled accelerator beams. The specific challenges for this use of the RTP system, including laser and crystal constraints, will be discussed. [Preview Abstract] |
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