Bulletin of the American Physical Society
APS April Meeting 2022
Volume 67, Number 6
Saturday–Tuesday, April 9–12, 2022; New York
Session W12: Neutron PhysicsRecordings Available
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Sponsoring Units: DNP Chair: Daniel Salvat, Indiana University Room: Shubert |
Monday, April 11, 2022 5:45PM - 5:57PM |
W12.00001: Improvements to the neutron detector for the BL3 experiment Christopher B Crawford
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Monday, April 11, 2022 5:57PM - 6:09PM |
W12.00002: Simulations of Proton Tacking and Detector Performance in the BL3 Experiment Jason A Fry Neutron beta decay is one of the most fundamental processes in nuclear physics and provides sensitive means to uncover the details of the weak interaction. A precise measurement of the neutron lifetime, along with neutron beta decay correlations, can provide tests of CKM unitarity and is needed for BBN models of the primordial 4He abundance. A next generation beam method experiment, BL3 at the NCNR, aims to improve the systematic precision of neutron lifetime measurements in order to resolve the discrepancy between beam and bottle method measurements. In BL3, the recoil protons from neutron beta decay are born in a quasi-Penning trap with magnetic and electric fields which transport them to a segmented silicon detector. The BL3 experiment will use higher neutron flux in a larger beam, which requires a larger proton detector than the BL2 experiment. The BL3 collaboration is using a combination of simulation tools to assess the anticipated performance. Simulations in Geant4 and Kassiopeia have been developed which use different electric and magnetic field propagation, as well as different physics lists for low-energy interactions. Additionally, a study of backscattering will be discussed. We will present results obtained with these different approaches to assess the performance of the BL3 apparatus. |
Monday, April 11, 2022 6:09PM - 6:21PM |
W12.00003: Measurement of the Los Alamos Ultracold Neutron Source Energy Spectrum Using Gravity Crank Spectrometers Austin R Reid, Chen-Yu Liu, Tyler Bondurant, Greg M Gill, Emma R Hogan, Alicen M Houff, Taejun Lee, Lilian M Lommel, Greg Lukens, Marc Touraev, Douglas Wong, Payne Vogtman The Los Alamos Neutron Science Center Ultracold Neutron Source is capable of generating the world's highest density of usable ultracold neutrons (UCN). We carried out the first direct measurement of the energy spectrum of UCN generated by LANSCE's upgraded Deuterium UCN source. By using two different gravity crank spectrometer geometries and extensive Monte Carlo modeling, we were able to extract an energy spectrum of the UCN delivered to the West beamline. |
Monday, April 11, 2022 6:21PM - 6:33PM |
W12.00004: Pendellösung Interferometric Measurement of the Neutron Charge Radius and Constraints on BSM Forces Benjamin Heacock, Takuhiro FUJIIE, Robert W Haun, Albert Henins, Katsuya Hirota, Takuya Hosobata, Michael G Huber, Masaaki Kitaguchi, Dmitry A Pushin, Hirohiko Shimizu, Masahiro Takeda, Robert Valdillez, Yutaka Yamagata, Albert Young Pendellösung interference occurs between internal neutron wave states in a Bragg-diffracting crystal. The absolute phase of the interference fringes is directly related to the neutron-crystalline potential. Recent measurements of silicon Bragg reflections with Miller indices (111), (220), and (400) have resulted in a determination of the neutron mean square charge radius of -0.1101 ± 0.0089 fm2 and placed limits on a Yukawa modification to gravity on atomic length scales. Further measurements of other Bragg reflections and crystal species can improve the precision of the charge radius measurement, as well as further constrain Beyond the Standard Model forces. |
Monday, April 11, 2022 6:33PM - 6:45PM |
W12.00005: Using a Pulsed Beam to Measure Higher-Order Neutron-Silicon Structure Factors with Pendellösung Interferometry Robert Valdillez, Leah J Broussard, Matthew Frost, Robert W Haun, Benjamin Heacock, Colin A Heikes, Albert Henins, Katsuya Hirota, Shannon M Hoogerheide, Takuya Hosobata, Michael G Huber, Masaaki Kitaguchi, Dmitry A Pushin, Hirohiko Shimizu, Masahiro Takeda, Fujiie Takuhiro, Yutaka Yamagata, Albert Young Dynamical diffraction gives rise to multiple waves inside perfect crystals when the incident wave nearly satisfies a Bragg scattering condition. The interference of these waves, called pendellösung, can be observed by "fringe-like" modulation of the intensity of the transmitted or diffracted beams exiting the crystal. Pendellösung interferometry can be used to precisely determine neutron-silicon structure factors, which may be used to investigate interactions Beyond the Standard Model, measure the internal structure of the neutron via the neutron charge radius, and provide information on thermal motion of the atoms in a lattice. While neutron-silicon structure factors have recently been measured for the (111), (220), and (400) reflections, quality data do not yet exist for the case of high-order reflections. Progress towards using the pulsed beam at the VULCAN beamline located at the Spallation Neutron Source run by Oak Ridge National Lab to measure the (333), (444), and (555) reflections simultaneously will be discussed. Leveraging the pulsed beam to measure multiple structure factors simultaneously will reduce some of the systematic uncertainties associated with the previous experiment. A successful measurement will allow for the study of anharmonic contributions, increase the precision of the determined neutron charge radius, and provide further constraints on an atomic length scale "fifth" force. |
Monday, April 11, 2022 6:45PM - 6:57PM |
W12.00006: A Precision Measurement of Zero Beam Polarization in the Nab Experiment at the SNS Chelsea M Hendrus The Nab Experiment at the Fundamental Physics Beamline (FnPB) at the Spallation Neutron Source (SNS) aims to precisely measure the electron-neutrino correlation coefficient a, and the Fierz interference term b, associated with the beta decay of free unpolarized neutrons. This measurement provides a cross-check and independent measurement of λ, the ratio of vector to axial-vector coupling constants in the Standard Model. A serious potential source of systematic error in this experiment stems from unwanted residual polarization in the incident neutron beam. We must be able to hold the polarization of the beam below 3*10-5. The experimental approach to measuring and mitigating this small polarization uses a polarized 3He spin filter, and an Adiabatic Fast Passage (AFP) neutron spin flipper. Here we present several details on the process of taking this measurement and some preliminary measurement data. |
Monday, April 11, 2022 6:57PM - 7:09PM |
W12.00007: Preliminary measurements of the binding energy of ions on a plastic surface in cryogenic liquids. Ashok Timsina, Wolfgang K Korsch The nEDM@SNS experiment will use a cryogenic technique to improve the present limit of the neutron electric dipole moment (nEDM) by about two orders of magnitude with an ultimate sensitivity of ∼3x10-28e-cm. The central part in this apparatus consists of two coated PMMA cells sandwiched between grounded and high voltage electrodes. Polarized ultracold neutrons are stored in a superfluid helium bath in a strong, stable electric field. During the experiment, several sources of ambient ionizing radiation generate charged particles in the cryogenic liquid. These ionized charges are adsorbed on the cell walls. As a result, an opposing static electric field is generated, which will impact the stability of the electric field. This instability of the E-field needs to be kept below 1% over a measurement cycle to achieve the required sensitivity of the nEDM measurement. Therefore, a compact test setup has been devised to study the behavior of ions inside cryogenic liquids using a scaled-down version of the nEDM cell and the electrodes. |
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