Bulletin of the American Physical Society
2010 Fall Meeting of the APS Division of Nuclear Physics
Volume 55, Number 14
Tuesday–Saturday, November 2–6, 2010; Santa Fe, New Mexico
Session NE: Instrumentation for EDM Searches |
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Chair: Brad Plaster, University of Kentucky Room: Coronado |
Saturday, November 6, 2010 10:30AM - 10:42AM |
NE.00001: An experimental search on the electron EDM based on solid-state techniques Young Jin Kim, Chen-Yu Liu A discovery of a permanent electric dipole moment of the electron (eEDM) would provide crucial information about the nature of T-violation and imply new sources of CP-violation beyond the Standard Model. We are pursuing research that would improve the present experimental limit of the eEDM using a new technique in solid-state systems at 4K. The experiment uses a Gadolinium Gallium Garnet sample with a large magnetic response, which can be measured using the Superconducting Quantum Interference Device as the magnetometer. In this talk, I will discuss the progress to control the systematic effects, including the design and implementation of a 24-bit DAQ system with ultra-low level of channel crosstalk, and the control of the high voltage drift from the supply. With significant progress, finally we push the experimental limit of eEDM on the order of 10-25e cm under four days integration time of data, which is most sensitive results ever achieved using the solid state technique. In addition, the experiment is free of sources that could produce spurious signal at this level. Further enhancement of the eEDM sensitivity would require operating the experiment at sub-Kelvin temperatures. [Preview Abstract] |
Saturday, November 6, 2010 10:42AM - 10:54AM |
NE.00002: Characterization of a 1/2 scale prototype magnet for the SNS neutron electric dipole moment experiment Adrian Perez Galvan, Bradley Filippone A new multi-institutional effort to measure the neutron electric dipole moment (nEDM) using ultra-cold neutrons and polarized $^{3}$He in a bath of superfluid $^{4}$He is currently underway at the Spallation Neutron Source at Oak Ridge National Laboratory. The search for the nEDM asks for stringent requirements on the stability and uniformity of the magnetic environment where the experiment takes place. A high uniformity holding field (provided by a modified Cos($\theta$) coil) plus several layers of magnetic shielding provide this pristine environment. We present measurements of the uniformity and stability of a half-scale coil inside magnetic shields under different experimental conditions and experimental parameters. [Preview Abstract] |
Saturday, November 6, 2010 10:54AM - 11:06AM |
NE.00003: Construction and commissioning of the magnetic field system for the NPDGamma experiment at the SNS and results of the spin transport calculations Septimiu Balascuta, Ricardo Alarcon, Stefan Baessler, Jasmin Sabina Schadler The NPDGamma experiment measures the parity-violating (PV) angular asymmetry of the gamma rays emitted in the capture of the polarized cold neutrons on protons. The neutrons from the Spallation Neutron Source (SNS) are polarized by a super mirror polarizer with a 350 G internal field. The polarizer fringe field is decreased using an additional magnet. After the polarizer the neutrons are guided to the hydrogen target by a uniform, stable, and vertical magnetic field of 9.5 Gauss. The direction of the neutron spin is reversed on a pulse- by-pulse basis by a resonant spin rotator located in front of the target. Downstream from the spin rotator the relative field gradient in the vertical direction has to be smaller than 3E-4 cm$^{-1}$. The field has to be vertical and aligned with the vertical axis of the detector with a precision better than 0.1 degrees to avoid the mixing of the left-right and up-down angular asymmetry. Measurements of the NPDGamma magnetic field and the simulation of the neutron spin transport will be presented. [Preview Abstract] |
Saturday, November 6, 2010 11:06AM - 11:18AM |
NE.00004: Magnetic Shielding Studies for the nEDM Experiment at the SNS Susan Malkowski, Brad Plaster The nEDM Experiment at the SNS requires an overall magnetic shielding factor of order $10^5$ to attenuate external background magnetic fields. At present, the shielding design includes an external (room-temperature) multi-layer $\mu$-metal magnetic shield, a cryogenic (4 Kelvin) Pb superconducting shield, and a cryogenic (4 Kelvin) ferromagnetic shield composed of a Metglas winding. This presentation will discuss results from a number of R\&D prototyping studies on the magnetic shielding design we have completed, including the formation of $\mu$-metal to $\mu$-metal magnetic seals across shielding gaps, optimized winding patterns for Metglas shields, studies of degaussing cycles, and methods for external background-field stabilization. [Preview Abstract] |
Saturday, November 6, 2010 11:18AM - 11:30AM |
NE.00005: SMOKE 'n Mirrors G. Phelps, M. Kalita, W. Korsch The surface magneto-optic Kerr effect (SMOKE) and photoelastic modulation elipsometry have emerged as integral tools in the study of magnetic thin films. SMOKE refers to the phenomenon in which the polarization of light reflected from a magnetized surface is rotated, the magnitude of which is proportional to the magnetization of the surface. Ellipsometry analyzes the change in the polarization direction of incident light upon the sample. These methods are implemented to study the long-term behavior of the magnetization of a DC magnetron sputtered FeCoV/TiN super-mirror sample by probing the longitudinal and transverse Kerr effects. An ellipsometer containing two Glan-Thompson prisms and a photoelastic modulator is implemented for the extration of the ellipsometric parameters $\Psi$ and $\Delta$ to the microradian level. This study is part of the Oak Ridge National Lab n-EDM Collaboration which plans to improve the present limit on the permanent electric dipole moment of the neutron by up to two orders of magnitude. The experiment will utilize magnetic super-mirrors to both polarize and guide neutrons. First results obtained from a magnetized super-mirror sample will be presented. [Preview Abstract] |
Saturday, November 6, 2010 11:30AM - 11:42AM |
NE.00006: Geant4 Simulations for the Radon Electric Dipole Moment Search at TRIUMF Evan Rand, Jack Bangay, Laura Bianco, Ryan Dunlop, Paul Finlay, Paul Garrett, Kyle Leach, Andrew Phillips, Carl Svensson, Chandana Sumithrarachchi, James Wong The existence of a permanent electric dipole moment (EDM) requires the violation of time-reversal symmetry (T) or, equivalently, the violation of charge conjugation C and parity P (CP). Although no particle EDM has yet been found, current theories beyond the Standard Model, e.g. multiple-Higgs theories, left-right symmetry, and supersymmetry, predict EDMs within current experimental reach. In fact, present limits on the EDMs of the neutron, electron and $^{199}$Hg atom have significantly reduced the parameter spaces of these models. The measurement of a non-zero EDM would be a direct measurement of the violation of time-reversal symmetry, and would represent a clear signal of new physics beyond the Standard Model. Recent theoretical calculations predict large enhancements in the atomic EDMs for atoms with octupole-deformed nuclei, making odd-A Rn isotopes prime candidates for the EDM search. The Geant4 simulations presented here are essential for the development towards an EDM measurement. They provide an accurate description of $\gamma$-ray scattering and backgrounds in the experimental apparatus, and are being used to study the overall sensitivity of the RnEDM experiment at TRIUMF in Vancouver, B.C. [Preview Abstract] |
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