Bulletin of the American Physical Society
2021 Fall Meeting of the APS Division of Nuclear Physics
Volume 66, Number 8
Monday–Thursday, October 11–14, 2021; Virtual; Eastern Daylight Time
Session JL: Mini-Symposium: BSM Searches in Fundamental V: EDMs |
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Chair: Emanuele Mereghetti, LANL Room: Georgian |
Wednesday, October 13, 2021 9:30AM - 9:42AM |
JL.00001: The TUCAN EDM Experiment Jeffery W Martin The goal of the TUCAN EDM experiment (TRIUMF Ultra-Cold Advanced Neutron Electric Dipole Moment experiment) is to make a new precise measurement of the neutron EDM, with an uncertainty of 1x10-27 e-cm, a one order of magnitude improvement compared to the current world's best limit. The experiment is unique in using a spallation-driven superfluid helium (He-II) source of ultracold neutrons (UCN). We have been operating a prototype UCN source at TRIUMF since 2017. We are now at the stage of upgrading this source to produce world-leading UCN densities, using a new He-II cryostat that has undergone cryogenic testing at KEK in 2020-21. We are also assembling the experimental components of the EDM experiment, including a magnetically shielded room, coils, and atomic magnetometers. This presentation will give an overview of the project, and discuss our recent progress upgrading the UCN source and preparing the EDM experiment. |
Wednesday, October 13, 2021 9:42AM - 9:54AM |
JL.00002: Magnetic Field Requirements for the TUCAN nEDM Experiment Mark H McCrea The TUCAN collaboration is preparing to make a new precision measurement of the neutron's permanent electric dipole moment (EDM), dn, with an uncertainty of 1×10-27e-cm, an order of magnitude better than the current world's best. To reach the goal sensitivity it is required to have highly uniform and well understood magnetic fields in the EDM measurement cells. |
Wednesday, October 13, 2021 9:54AM - 10:06AM |
JL.00003: The TRIUMF UltraCold Advanced Neutron source Wolfgang Schreyer The TUCAN collaboration is building a unique ultracold-neutron source using superfluid helium and liquid deuterium to moderate neutrons from a spallation source. Scheduled to go into operation in 2022 we expect it to be the world’s strongest source for ultracold neutrons, which will allow us to search for an electric dipole moment of the neutron with a sensitivity of 10-27 e·cm. |
Wednesday, October 13, 2021 10:06AM - 10:18AM |
JL.00004: Searching for time-varying nuclear electric dipole moments using precision magnetic resonance Alexander Sushkov The Cosmic Axion Spin Precession Experiments (CASPEr) search for ultralight axion-like dark matter. CASPEr-e is sensitive to the time-varying nuclear electric dipole moment, induced by the electric-dipole moment (EDM) coupling gd. The detection scheme is based on a precision measurement of 207Pb solid-state nuclear magnetic resonance in a polarized ferroelectric crystal. We calibrated the detector and characterized the excitation spectrum and relaxation parameters of the nuclear spin ensemble with pulsed magnetic resonance measurements in a 4.4 T magnetic field. We swept the magnetic field near this value and searched for axion-like dark matter with Compton frequency within a 1 MHz band centered at 39.65 MHz. Our measurements place the upper bound gd < 9.5 × 10-4 GeV-2 (95% confidence level) in this frequency range. This constraint corresponds to an upper bound of 1.0 × 10-21 e·cm on the amplitude of oscillations of the neutron electric dipole moment, and 4.3 × 10-6 on the amplitude of oscillations of CP-violating θ-parameter of quantum chromodynamics. Our results demonstrate the feasibility of using solid-state nuclear magnetic resonance to search for axion-like dark matter in the nano-electronvolt mass range. |
Wednesday, October 13, 2021 10:18AM - 10:30AM |
JL.00005: Magnetic Field System in the nEDM@SNS Experiment Alina A Aleksandrova, Larry Bartoszek, Joe Benson, Robert Carr, Umit Hasan Coskun, Christopher Daurer, Bradley Filippone, Roy J Holt, Brad Plaster, John C Ramsey, Simon A Slutsky, Xuan Sun, Christopher M Swank, Raymond Tat, Wanchun Wei The neutron electric dipole moment (nEDM) is one of the most sensitive probes of charge-conjugation and parity (CP) violation. The current upper limit for the nEDM is dn < 1.8×10-26 e-cm (90% CL). The nEDM experiment at the Spallation Neutron Source (nEDM@SNS) aims to reduce this limit by two orders of magnitude. Targeting a sensitivity of < 3×10-28 e-cm, it is important to suppress false EDM signals due to the geometric phase effect which arises from nonuniformities in the magnetic field. The required uniform magnetic field, with gradients in the holding field < 3 ppm/cm, will be generated by a modified, saddle shaped cosθ coil enclosed in a nearly-hermetic superconducting lead shield. This talk will present the design, construction and status of the magnetic field system in the nEDM@SNS experiment. |
Wednesday, October 13, 2021 10:30AM - 10:42AM |
JL.00006: Cryogenic Engineering for the Magnetic Field System in the nEDM@SNS Experiment Wanchun Wei The nEDM@SNS experiment aims to measure the electric dipole moment of neutrons at a new level of sensitivity. The Magnetic Field System is designed to generate a holding field with uniformity < 3 ppm/cm as well as a spin dressing field. The entire magnet package is cooled to below 6K to maintain functioning of the superconducting wires and shields with two pulse-tube cryocoolers. In order to minimize distortion of the fields, these cryocoolers are installed in a separate vessel at a distance, and the cooling power is delivered via circulation of supercritical helium. Heating of the metglas flux return by the alternating dressing field is eliminated by a passive copper shield. A magnetic probe will be installed in a warm bore located in the center of the magnet to characterize the generated fields. A Cu-G10 woven 100K thermal shield around the warm bore is fabricated to minimize the distortion on the dressing field in the field mapping. |
Wednesday, October 13, 2021 10:42AM - 10:54AM |
JL.00007: Cryogenic Magnetic Field Monitor System in the SNS Neutron EDM Experiment Umit Hasan Coskun The existence of a permanent neutron electric dipole moment (nEDM), dn, would be a violation of charge-conjugation and parity (CP) symmetry. The current world limit for the neutron electric dipole moment is dn < 1.8×10-26 e·cm (90% CL). The nEDM experiment at the Spallation Neutron Source (nEDM@SNS) targets to improve this limit by two orders of magnitude, dn ~ 10-28 e·cm. For the suppression of systematic effects in the experiment induced by magnetic field gradients, the magnetic field non-uniformities inside of the experimental region need to be accurately monitored and regulated. A magnetic field monitoring system, which contains 39 single-axis cryogenic fluxgate magnetometer probes at discrete locations, has been designed and constructed to provide a first-pass measure of the field gradients inside of the experimental region using nondisruptive measurements of the components of the magnetic field. This talk will discuss the construction of the field monitor system, and results from initial tests of the system. |
Wednesday, October 13, 2021 10:54AM - 11:06AM |
JL.00008: Measurement of Neutron Polarization and Transmission for the nEDM@SNS Experiment. Kavish Imam The neutron electric dipole moment experiment at the Spallation Neutron Source (nEDM@SNS) will implement a novel method, which utilizes polarized ultra-cold neutrons (UCN) and polarized 3He in a bath of superfluid 4He, to place a new limit on the nEDM down to 2-3×10-28 e·cm. The experiment will employ a cryogenic magnet and magnetic shielding package to provide the required magnetic field environment to achieve the proposed sensitivity. This talk will describe the design and implementation of a 3He polarimetry setup at the SNS to measure the neutron polarization and transmission losses resulting from passage through the magnetic shielding and cryogenic windows. |
Wednesday, October 13, 2021 11:06AM - 11:18AM |
JL.00009: An Atomic Beam Source of Polarized 3He for the nEDM@SNS Experiment Mark A Broering, Evgeni Tsentalovich, James Kelsey, Robert P Redwine The neutron Electric Dipole Moment at the Oak Ridge National Laboratory Spallation Neutron Source (nEDM@SNS) experiment requires a source of highly (>95%) polarized 3He to be used as both a comagnetometer and a neutron spin state analyzer. This latter use is possible because the neutron 3He capture cross-section is minimized, near zero, when their spins are parallel and is maximized when the spins are antiparallel. This will cause any difference between the two Larmor precession frequencies to generate a change in the capture rate. A second magnetic field can be used to critically dress the spins such that any change in capture rate is the direct result of the neutron electric dipole moment coupling to an electric field. Spin exchange and meta-stability exchange optical pumping techniques are unlikely to produce a 3He sample with high enough polarization. Therefore, an Atomic Beam Source (ABS) is being developed to produce the polarized 3He. This device uses a quadrupole magnet system to preferentially select a spin state in a cold 3He gas (at or below 1.3 K). The operating principles and requirements for the ABS and the significant progress that has been made on its development will be described. |
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