Bulletin of the American Physical Society
APS April Meeting 2017
Volume 62, Number 1
Saturday–Tuesday, January 28–31, 2017; Washington, DC
Session U13: Minisymposium: Precision Measurements in Nuclear Physics IIIFocus
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Sponsoring Units: DNP Chair: Guy Savard, Argonne National Laboratory Room: Roosevelt 5 |
Monday, January 30, 2017 3:30PM - 4:06PM |
U13.00001: Mass Measurements with the Canadian Penning Trap at CARIBU Invited Speaker: Rodney Orford Roughly half of the elements heavier than iron are thought to be produced through the astrophysical \textit{r} process of nucleosynthesis. Despite its large influence in explaining the observed abundance of heavy elements, much of the \textit{r} process is still poorly understood. A more thorough library of nuclear data of neutron-rich nuclei is needed to improve the accuracy and progression of \textit{r}-process calculations. In particular, accurate mass measurements are in demand due to the strong coupling between mass and other nuclear properties such as $\beta$-decay and neutron-capture rates. For nearly three decades, direct mass measurements conducted by Penning trap mass spectrometers have proven to be an accurate method of determining masses to a precision suitable for \textit{r}-process calculations ($\Delta m/ m < 10^{-7}$). The Canadian Penning trap mass spectrometer (CPT) is currently located in the CARIBU facility at Argonne National Laboratory where intense radioactive beams of neutron-rich nuclei are produced from the spontaneous fission of $^{252}$Cf. Since moving into CARIBU the CPT has successfully measured the masses of more than 110 isotopes to a typical precision of 15 keV/c$^2$. In order to push measurements to nuclides further from stability which may play a part in the \textit{r} process, a number of upgrades to both the CPT and CARIBU have been made. A Multi-Reflection Time-Of-Flight (MR-TOF) mass separator has been added to the CARIBU beamline providing cleaner beams to low-energy experiments, and at the CPT a position-sensitive multichannel plate detector has been installed to facilitate a contemporary phase-imaging mass measurement technique. This technique allows for faster measurements with fewer ions and provides more than an order of magnitude improvement in mass resolving power without loss in precision. These upgrades, alongside recent measurements of neutron-rich rare-earth isotopes will be discussed. [Preview Abstract] |
Monday, January 30, 2017 4:06PM - 4:18PM |
U13.00002: Multi-reflection time-of-flight mass spectrometer (MR-ToF) simulation and commissioning at the University of Notre Dame James M Kelly, Catherine Nicoloff, Bradley E Schultz, Maxime Brodeur The production of rare isotopes entails efficient ion beam purification for precision measurements that require samples of a single species. To this end, a multi-reflection time-of-flight mass spectrometer (MR-ToF) has been built and is being commissioned in an offline test setup at the University of Notre Dame. MR-ToFs can accommodate low production yields and short half-lives of desired radionuclides, and can separate isobars with resolving powers \textgreater 10$^{\mathrm{5}}$. This MR-ToF will be a critical component for quickly removing radioactive contaminants produced at the future N $=$ 126 beam factory addition to ATLAS at Argonne National Laboratory. This unique thermalized ion beam facility will produce through deep-inelastic reactions very neutronrich nuclei relevant to the astrophysical r-process. A series of simulations done to optimize the MR-ToF's operation, as well as preliminary commissioning results, will be presented. This work is supported by the National Science Foundation. [Preview Abstract] |
Monday, January 30, 2017 4:18PM - 4:30PM |
U13.00003: Precision experiments to test the Standard Model at the University of Notre Dame Maxime Brodeur The Standard Model of Physics as a description of matter in the universe contains many unexplained features. One way to search for physics beyond the Standard Model (SM) is accomplished by testing the unitarity of the Cabibbo-Kobayashi-Maskawa matrix. Such a unitarity test requires a precise and accurate determination of the Vud matrix element, which is currently achieved via the precise determination of the comparative half-life of superallowed beta decays. While $V_{ud}$ is currently determined mostly from an ensemble of precise experimental quantities of superallowed pure Fermi transitions, there is currently a growing interest in obtaining $V_{ud}$ from superallowed mixed transitions to test the accuracy of $V_{ud}$ and the calculation of the isospin symmetry breaking theoretical correction. In the past year our group has performed several half-life measurements of mirror decay transitions using radioactive ion beams produced by the TwinSol facility of the Nuclear Science Laboratory of Notre Dame. In the future we also plan on building an ion trapping system to measure the Fermi to Gamow-Teller mixing ratio in many mirror decays for the first time. [Preview Abstract] |
Monday, January 30, 2017 4:30PM - 4:42PM |
U13.00004: Building a Single Atom Microscope for Nuclear Astrophysics Dustin Frisbie, Maegan Johnson, Kristen Parzuchowski, Jennifer Wenzl, Jaideep Singh The primary research goal of this project is to develop a new technique of optical single atom detection to measure rare nuclear reactions at low energies. The $^{22}$Ne($\alpha$,$n$)$^{25}$Mg reaction is of particular interest, as it is thought to be a primary source of neutrons in the the s-process of massive stars. Nuclear reaction products are captured in a cryogenically frozen film of noble gas, which can contain a variety of guest atoms. These solids are ideal to use because they are optically transparent and simple to grow and purify. The sample is illuminated by laser light and imaged to identify fluorescing atoms. The atomic transitions of captured atoms indicate which atoms are present; only atoms which are excited at the laser wavelength will fluoresce. This offers high selectivity during experiments. We began development with Yb, a very bright guest atom, being embedded in a host of solid neon in order to study the optical properties necessary for single atom detection. In addition, we study background effects from the laser exciting contaminants in our substrates. We present data that indicates the efficiency with which we can excite and collect fluorescence light with our apparatus, and use it to propose a strategy for the development of Mg single atom detection. [Preview Abstract] |
Monday, January 30, 2017 4:42PM - 4:54PM |
U13.00005: A new search for the permanent electric dipole moment of $^{129}$Xe at FRM-II N. Sachdeva, T. Chupp, S. Degenkolb, P. Fierlinger, E. Kraegloh, F. Kuchler, T. Lins, J. Meinel, B. Niessen, S. Stuiber, W. A. Terrano, M. Burghoff, I. Fan, W. Kilian, S. Gr{\"u}neberg, A. Schnabel, F. Seifert, D. Stollfuss, L. Trahms, J. Voight, E. Babcock, Z. Salhi, J. Huneau, J. Singh CP-violating sources in beyond-the-standard-model physics, necessary to explain baryon asymmetry, give rise to permanent electric dipole moments (EDMs). Precise EDM measurements of the neutron, electron, paramagnetic and diamagnetic atoms constrain CP-violating parameters. The previous limit for the $^{129}$Xe EDM is $6 \times 10^{-27}~e \cdot \mathrm{cm}$ (95$\%$ CL). The HeXeEDM experiment at FRM-II (Munich Research Reactor) utilizes an ultralow magnetic field in a high-performance magnetically shielded room and $^3$He comagnetometer to improve the limit by up to three orders of magnitude. In the experiment, hyperpolarized $^3$He and $^{129}$Xe precession signals are detected with a SQUID magnetometer array in the presence of applied electric and magnetic fields. Recent progress will be presented. [Preview Abstract] |
Monday, January 30, 2017 4:54PM - 5:06PM |
U13.00006: Upgrades for an improved measurement of the EDM of $^{\mathrm{\mathbf{225}}}$\textbf{Ra} Tenzin Rabga, Kevin Bailey, Matthew R. Dietrich, John P. Greene, Roy J. Holt, Wolfgang Korsch, Zheng-Tian Lu, Peter Mueller, Tom P. O'Connor, Steven Fromm, Roy Ready, Jaideep T. Singh If charge conjugation (C), parity (P) and time-reversal (T) symmetries, collectively form a good symmetry of nature, CPT, then T-violating phenomena would also violate CP. An Electric Dipole Moment (EDM) would violate time-reversal symmetry, and therefor EDMs provide a sensitive way for probing CP-violation that might explain the abundance of matter over anti-matter in the Universe. The $^{\mathrm{225}}$Ra atom (t$_{\mathrm{1/2}} \quad =$ 15 days, I $=$ 1/2) is a particularly attractive candidate for an EDM search in diamagnetic atoms due to its octupole deformed nuclear structure, nearly degenerate parity doublet ground state, and a large mass, that make it sensitive to T-violating interactions in the nuclear sector. Our latest measurement limits the atomic EDM of $^{\mathrm{225}}$Ra to be less than 1.4x10$^{\mathrm{-23}}$ e-cm (95{\%} C.L). Further experimental upgrades are being implemented including an electric field upgrade to enhance the EDM sensitivity and STIRAP for an improved spin precession detection scheme. With these upgrades in place our EDM sensitivity should increase by nearly two orders of magnitude and allow us to substantially improve constraints on certain T-violating processes within the nucleus.~This work is supported by the U.S. DOE, Office of Science, Office of Nuclear Physics, under contract DE-AC02-06CH11357 and the Michigan State University. [Preview Abstract] |
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