Bulletin of the American Physical Society
2009 APS April Meeting
Volume 54, Number 4
Saturday–Tuesday, May 2–5, 2009; Denver, Colorado
Session C14: Ultracold Neutrons and Fundamental Symmetries |
Hide Abstracts |
Sponsoring Units: GPMFC DNP Chair: Susan Gardner, University of Kentucky Room: Plaza Court 4 |
Saturday, May 2, 2009 1:30PM - 1:42PM |
C14.00001: Measurement of neutron beta decay asymmetry using ultracold neutrons Steven Clayton An experiment to measure the neutron beta-decay angular correlation between the emitted beta particle and the neutron spin (the beta asymmetry) using ultracold neutrons (UCN) will be described. The experimental method involves loading highly polarized UCN into a material decay trap within a solenoidal beta spectrometer. The neutron polarization is systematically flipped to cancel the effect of differing efficiencies between the two ends of the spectrometer. First physics results, which represent a demonstration of the experimental method, were recently published in PRL based on data taken in 2007. In Fall 2008 a much higher statistics data set was collected and several systematics studies were performed. These are expected to give a measurement of the neutron beta asymmetry that approaches the best measurements using cold neutrons. [Preview Abstract] |
Saturday, May 2, 2009 1:42PM - 1:54PM |
C14.00002: Systematics of the UCNA Experiment A.T. Holley The goal of the UCNA experiment is to determine the angular correlation between the electron momentum and the neutron spin (the beta asymmetry) in free neutron decay using polarized ultracold neutrons (UCN). The experimental strategy is to transport UCN into a decay volume through a 7T static magnetic field, allowing the magnetic potential to polarize the UCN. The energy and transverse position of the electrons produced by beta decay are then measured by detectors on either side of the decay volume, with a 1T longitudinal field ensuring $2 \times 2 \pi$ collection of the electrons. UCN polarization can be reversed via an rf adiabatic spin flipper, thereby providing first-order cancellation of systematic asymmetries between the beta detectors via the usual super ratio. The spin flipper also allows an \textit{in situ} measurement of the depolarized contamination which develops during a constant-polarization measurement cycle. UCN-based angular correlation experiments have the innate advantages of essentially 100$\%$ initial neutron polarization and small neutron-generated backgrounds, both of which allow for good control over two of the major systematics in free neutron angular correlation measurements. These systematics, along with the systematic effects associated with our detector response and backscattering, will be discussed in relation to the UCNA experiment and our ultimate goal to extract a 1$\%$ or better measurement of the beta asymmetry from the data taken during our 2008 run cycle. [Preview Abstract] |
Saturday, May 2, 2009 1:54PM - 2:06PM |
C14.00003: Suppression of Ultracold Neutron Depolarization on Material Surfaces with Magnetic Holding Fields Raymond Rios The depolarization of Ultracold Neutrons(UCN) was measured within 1-m long, 2 3/4" diameter electropolished copper, diamondlike carbon-coated copper, and stainless steel guide tubes as a function of magnetic holding field. The UCN were trapped between a 6 Tesla solenoidal magnetic field and a 3/8" copper aperture. A series of Helmholtz coils produced a magnetic field over the length of the test guide of either 10 or 250 Gauss. The surface depolarization was observed to be suppressed at the higher holding field on the measured copper guides. These measurements will aid in the determination of the upper limit of depolarization of UCN in the UCN beta asymmetry measurement at LANL (UCNA) and in understanding the mechanisms for depolarization in non-magnetic guides. [Preview Abstract] |
Saturday, May 2, 2009 2:06PM - 2:18PM |
C14.00004: Diamond-like-Carbon Coated Copper Guides for use in Polarized UCN Transport Russell Mammei The UCNA experiment at Los Alamos National Lab (LANL) employs ultracold neutrons (UCN) to measure the beta-asymmetry in polarized neutron decay. Currently our beamline makes use of polished stainless steel and copper guides to transport and bottle the UCN. Due to their high Fermi potential and low expected depolarization per bounce, Diamond-like-Carbon (DLC) coated copper guides should increase the neutron density in our decay volume. However there have been challenges in obtaining a well-adhered DLC coating on the copper substrate. Although a variety of production processes have been explored, a pulsed laser deposition process, similar to ion-bombardment coating techniques, has been found to produce a successfully bonded coating. To this end two DLC coated copper guides were produced with this method and tested with UCN at LANL. An overview of the coating process will be given along with UCN bottle/transmission results. [Preview Abstract] |
Saturday, May 2, 2009 2:18PM - 2:30PM |
C14.00005: Precision Polarization of Neutrons Elise Martin, Libertad Barron-Palos, Aaron Couture, Christopher Crawford, Tim Chupp, Areg Danagoulian, Mary Estes, Binita Hona, Gordon Jones, Andi Klein, Seppo Penttila, Monisha Sharma, Scott Wilburn Determining polarization of a cold neutron beam to high precision is required for the next generation neutron decay correlation experiments at the SNS, such as the proposed abBA and PANDA experiments. Precision polarimetry measurements were conducted at Los Alamos National Laboratory with the goal of determining the beam polarization to the level of 10$^{-3}$ or better. The cold neutrons from FP12 were polarized using optically polarized ${}^{3}$He gas as a spin filter, which has a highly spin-dependent absorption cross section. A second ${}^ {3}$He spin filter was used to analyze the neutron polarization after passing through a resonant RF spin rotator. A discussion of the experiment and results will be given. [Preview Abstract] |
Saturday, May 2, 2009 2:30PM - 2:42PM |
C14.00006: Investigation of Evaporative Removal of $^{3}$He from Liquid $^{4}$He for the nEDM Experiment F. DuBose, D.G. Haase, P.R. Huffman The discovery of a nonzero electric dipole moment for the neutron (nEDM) would have a fundamental impact upon the current understanding of the weak and strong nuclear interactions. A non-zero value at the order expected in the proposed experiment (10$^{-28} \quad e$ \textit{cm}) would indicate new sources of T and CP violation, thereby either extending or disproving aspects of the Standard Model. In the nEDM experiment, neutrons are trapped in liquid helium, doped with trace amounts of polarized $^{3}$He, in parallel magnetic and electric fields, causing them to precess. The effect of the electric field upon the precession frequency of the neutron can then be used to characterize the neutron charge distribution. As the $^{3}$He depolarizes, it must be removed before repeating the doping process. We are developing an evaporative purification technique that can facilitate this removal, thereby lowering the concentration of $^{3}$He in $^{4}$He from approximately 10$^{-10}$ to 10$^{-12}$, at an operating temperature between 250 mK and 500 mK. [Preview Abstract] |
Saturday, May 2, 2009 2:42PM - 2:54PM |
C14.00007: An Apparatus to Study Ultra-Cold Neutron Production in Solid Oxygen Daniel Salvat, Chen-Yu Liu, Christopher Lavelle, Patrick McChesney, Gregory Manus, Yu Feng, Yunchang Shin, Albert Young, Guilhem Ribeill, Adam Holley, Chris Morris, Mark Makela, Andy Saunders Ultra-Cold Neutrons (UCN) provide sensitive measurements of the neutron's properties, such as the neutron lifetime, electric dipole moment, and angular correlations in beta-decay. Solid deuterium offers a super-thermal phonon down-scattering mechanism to produce UCN; however, the lifetime of UCN in solid deuterium is limited by the material's absorption and incoherent scattering cross-sections. Solid oxygen possesses zero incoherent cross-section and magnon, as well as phonon, down-scattering modes. These suggest potentially larger effective production volume and higher UCN yield than deuterium. We present an apparatus to investigate temperature and magnetic field dependent UCN production. The instrument is benchmarked using 97 percent ortho-deuterium from 5 to 18 Kelvin. Results for oxygen will be presented in the following talk. [Preview Abstract] |
Saturday, May 2, 2009 2:54PM - 3:06PM |
C14.00008: Experimental Results of Ultra-Cold Neutron Production in Solid Oxygen Christopher Lavelle, Chen-yu Liu, Yunchang Shin, Dan Salvat, Patrick McChesney, Greg Manus, Guilhem Ribeill, Albert Young, Chris Morris, Mark Makela, Andy Saunders The results of an experimental investigation of Ultra-cold neutron (UCN) production from magnetic solid oxygen are presented. Using neutrons from flight path 12 at Lujan Center, LANSCE, we study the production of UCN from the cold neutron beam at LANSCE FP12 as a function of temperature, source volume, incident neutron energy, and applied magnetic field up to 5.5 T. Results suggest UCN production from magnetic interactions with the neutron is a dominant mode of production, and that UCN from solid oxygen is comparable to that from deuterium. [Preview Abstract] |
Saturday, May 2, 2009 3:06PM - 3:18PM |
C14.00009: Transport Simulation towards Understanding the Field-Dependent Ultracold Neutron Production in Solid Oxygen Yu Feng, Chen-yu Liu, Christopher Lavelle, Yunchang Shin, Daniel Salvat, Patrick McChesney, Greg Manus, Guilhem Ribeill, Albert Young, Chris Morris, Mark Makela, Andy Saunders, Adam Holley We will present a Monte-Carlo simulation on ultracold neutron (UCN) transport in the guide system used in the UCN production experiment in the summer of 2008. The simulation uses a UCN package [1] previously developed at Paul Scherrer Institute using the GEANT4 framework. The resulting transport efficiency is benchmarked by measurements on UCN transport through the same guide system. Furthermore, we simulate UCN transport through a non-uniform, solenoid magnetic field, results of which are used to extract the information of field-dependent UCN production in Solid Oxygen in low temperature alpha- and beta- phases. [1] F. Atchison et al., NIMA 552 (2005) 513 [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700