Bulletin of the American Physical Society
2019 Fall Meeting of the APS Division of Nuclear Physics
Volume 64, Number 12
Monday–Thursday, October 14–17, 2019; Crystal City, Virginia
Session KL: Mini-Symposium on Fundamental Symmetries: Theory and Experiment III |
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Chair: Nadia Fomin, University of Tennessee Room: Salon H |
Wednesday, October 16, 2019 8:30AM - 9:06AM |
KL.00001: The Search for Electric Dipole Moments in the FRIB Era Invited Speaker: Jaideep Singh Experimental tests of fundamental symmetries using nuclei and other particles subject to the strong nuclear force have led to the discovery of parity (P) violation and the discovery of charge-parity (CP) violation. It is believed that additional sources of CP-violation may be needed to explain the apparent scarcity of antimatter in the observable universe. A particularly sensitive and unambiguous signature of both time-reversal- (T) and CP-violation would be the existence of an electric dipole moment (EDM). The current generation of EDM searches in a variety of complimentary systems have unprecedented sensitivity to physics beyond the Standard Model. My talk will focus on diamagnetic systems such as Xe-129 and Hg-199 as well as certain rare diamagnetic atoms such as Ra-225 which have pear-shaped nuclei. This uncommon nuclear structure significantly amplifies the observable effect of T, P, & CP-violation originating within the nuclear medium when compared to isotopes with nearly spherical nuclei such as Hg-199. Certain isotopes of Radium (Ra), Protactinium (Pa), and Radon (Rn) are all expected to have enhanced atomic EDMs and will be produced in abundance at the Facility for Rare Isotope Beams currently under construction at Michigan State University. I will describe the present status of ongoing EDM searches in Xe-129, Hg-199, and Ra-225 as well as the prospects for next generation searches for time-reversal violation in both atomic and molecular systems in the FRIB-era. [Preview Abstract] |
Wednesday, October 16, 2019 9:06AM - 9:18AM |
KL.00002: Status of the neutron Electric Dipole Moment Search at Los Alamos National Laboratory Austin Reid A permanent neutron EDM presents an experimentally accessible measurement of beyond Standard Model physics. Further improvements on the more than a decade old nEDM upper bound have been hindered by insufficient ultracold neutron (UCN) density. The recently upgraded solid deuterium UCN source at Los Alamos National Laboratory (LANL) generates sufficient densities of stored UCN to measure nEDM at $3\times10^{-27}~\mathrm{e}\cdot\mathrm{cm}$ with established technologies. This talk will present the status of the experiment and its projected timeline. [Preview Abstract] |
Wednesday, October 16, 2019 9:18AM - 9:30AM |
KL.00003: Magnetic Field Monitoring in the SNS Neutron EDM Experiment Alina Aleksandrova One of the most sensitive probes of charge-conjugation and parity (CP) violation is the neutron electric dipole moment, for which the current upper limit is $d_{n} < 3.0 \times 10^{-26}$ e-cm (90\% CL). The Spallation Neutron Source neutron EDM experiment aims to reduce this limit by two orders of magnitude. Targeting a sensitivity of $10^{-28}$ e-cm, it is important to suppress systematic effects in the experiment caused by magnetic field nonuniformities. Thus, it is important to be able to precisely control and monitor the magnetic field gradients inside of the experimental volume. However, it is not always possible to measure the field within the region of interest directly. To remedy this issue in the SNS nEDM experiment, we have designed a field monitoring system that will allow us to reconstruct the field gradients inside of the fiducial volume using noninvasive measurements of the field components at discrete locations external to this volume. The field monitor array consists of $39$ cryogenic-compatible, single-axis fluxgate magnetometer probes that are controlled by an automated switching system. This talk will present the design and studies of this field monitor along with studies performed to characterize the properties of these sensors at cryogenic temperatures. [Preview Abstract] |
Wednesday, October 16, 2019 9:30AM - 9:42AM |
KL.00004: Design and Testing of a Magnetic Shielding Enclosure for Testing Spin Transport Magnets for the SNS nEDM Experiment Mark McCrea The SNS nEDM Experiment aims to measure the neutron electric dipole moment to a sensitivity of order $10^{-28}e\cdot cm$. A series of magnets are being developed to transport polarized helium-3 from an atomic beam source outside the external magnetic shielding to its interior which has a uniform 30 mG magnetic field created by a rectangular solenoid. A pair of modified cosine theta coils are being developed to maintain the internal magnetic field uniformity through the 62 cm diameter opening in the magnetic shielding the polarized He-3 passes through. Once inside the shielding the polarized He-3 will be accumulated in a storage volume before being moved into the measurement cell where it will be used as a comagnetometer during the nEDM measurement. To aid in the magnet development a two layer magnetic shielding enclosure composed of high permeability metal alloys has been designed that will provide a similar magnetic environment to the full scale apparatus. I will describe the simulation, design and testing of this shielding enclosure. [Preview Abstract] |
Wednesday, October 16, 2019 9:42AM - 9:54AM |
KL.00005: Measurement of Neutron Polarization and Transport for the SNS nEDM Experiment. Kavish Imam The existence and size of a neutron electric dipole moment (nEDM) remains an important question in particle and cosmological physics. The SNS nEDM experiment proposes a new limit for nEDM search by using ultra-cold neutrons (UCN) in a bath of superfluid helium. The experiment uses polarized 8.9{\AA} neutrons to create polarized UCN in situ in superfluid helium via superthermal downscattering. This process requires the 8.9{\AA} neutrons to retain their polarization as they pass through the magnetic shielding and nEDM cryostat windows. This talk will describe a setup to measure the neutron polarization loss from the magnetic shielding and cryostat windows. [Preview Abstract] |
Wednesday, October 16, 2019 9:54AM - 10:06AM |
KL.00006: Laser Assisted Electric Field Monitoring in a Cryogenic Environment Mark Broering, Josh Abney, Murchhana Roy, Mark McCrea, Christopher Swank, Brad Filippone, Weijun Yao, Wolfgang Korsch The neutron EDM collaboration at the Spallation Neutron Source (ORNL) plans to use ultra-cold neutrons in liquid helium to improve the nEDM limit by two orders of magnitude. In this apparatus, neutrons are stored in target cells located in a strong, stable electric field. Local radiation generates charged particles which build up on the target cell walls reducing the field's strength and stability. The field fluctuations need to be kept below 1{\%}, making it necessary to study this cell charging behavior, determine its effect on the experiment, and find ways to mitigate this. A compact test setup was designed to study this effect using small electrodes and a cell. Charged particles are generated by ionizing the helium with a $^{\mathrm{137}}$Cs source and the electric field is monitored via the electro-optic Kerr effect. Linearly polarized light is passed through the helium. The Kerr effect then introduces an ellipticity to the polarization that is proportional to the electric field squared. First measurements of cell charging in superfluid helium will be reported. This research is supported by DOE grants: DE-FG02-99ER41101, DE-AC05-00OR22725, DE-SC0014622 [Preview Abstract] |
Wednesday, October 16, 2019 10:06AM - 10:18AM |
KL.00007: Systematics and Operational Studies for the SNS nEDM Experiment Robert Dipert The Systematic and Operational Studies (SOS) apparatus, being designed for the PULSTAR reactor at NC State University, is a test bed for the Neutron Electric Dipole Moment (nEDM) experiment at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory. The PULSTAR-SOS apparatus and SNS-nEDM experiment will have many physically similar conditions, including (a) temperature near 400 mK, (b) the same measurement cell design, size, and wavelength shifter, (c) use of a Superconducting QUantum Interference Device (SQUID) magnetic detection system, and (d) the use of helium-3 as a co-magnetometer, polarization analyzer, and detector. The major difference is that the PULSTAR-SOS apparatus will not have an electric field. However, it is possible to study the major false edm effect by means of relaxation and frequency shift measurements. Construction of the PULSTAR-SOS cryostat has begun at the Triangle Universities Nuclear Laboratory (TUNL). I will report on the systems which have been installed and tested. [Preview Abstract] |
Wednesday, October 16, 2019 10:18AM - 10:30AM |
KL.00008: Simulation of time dependent magnetic field variations in the SNS nEDM experiment Mojtaba Behzadipour The Spallation Neutron Source (SNS) neutron electric dipole moment experiment (nEDM) requires precise control of the magnetic field. Time-dependent variations in the magnetic field will be monitored with the polarized $^3$He co-magnetometer via detection of the precessing $^3$He magnetization in SQUID pickup loops. The resulting SQUID signal will then be used to correct for these time dependent magnetic field variations that appear in measurements of the neutron and $^3$He precession frequency difference. We have carried out simulations of the response of the SQUID $^3$He co-magnetometer to time-dependent variations in the magnetic field and have explored various schemes for corrections to the measured neutron precession frequency due to these time-dependent magnetic field variations. Preliminary results showing the sensitivity of the extracted neutron precession frequency to magnetic field variations will be discussed. [Preview Abstract] |
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