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Title: Superconducting magnetic Wollaston prism for neutron spin encoding

Abstract

A magnetic Wollaston prism can spatially split a polarized neutron beam into two beams with different neutron spin states, in a manner analogous to an optical Wollaston prism. Such a Wollaston prism can be used to encode the trajectory of neutrons into the Larmor phase associated with their spin degree of freedom. This encoding can be used for neutron phase-contrast radiography and in spin echo scattering angle measurement (SESAME). In this paper, we show that magnetic Wollaston prisms with highly uniform magnetic fields and low Larmor phase aberration can be constructed to preserve neutron polarization using high temperature superconducting (HTS) materials. The Meissner effect of HTS films is used to confine magnetic fields produced electromagnetically by current-carrying HTS tape wound on suitably shaped soft iron pole pieces. The device is cooled to ∼30 K by a closed cycle refrigerator, eliminating the need to replenish liquid cryogens and greatly simplifying operation and maintenance. A HTS film ensures that the magnetic field transition within the prism is sharp, well-defined, and planar due to the Meissner effect. The spin transport efficiency across the device was measured to be ∼98.5% independent of neutron wavelength and energizing current. The position-dependent Larmor phase of neutron spinsmore » was measured at the NIST Center for Neutron Research facility and found to agree well with detailed simulations. The phase varies linearly with horizontal position, as required, and the neutron beam shows little depolarization. Consequently, the device has advantages over existing devices with similar functionality and provides the capability for a large neutron beam (20 mm × 30 mm) and an increase in length scales accessible to SESAME to beyond 10 μm. With further improvements of the external coupling guide field in the prototype device, a larger neutron beam could be employed.« less

Authors:
; ; ;  [1];  [2];  [3];  [4];  [5];  [1];  [6]
  1. Center for Exploration of Energy and Matter, Indiana University, Bloomington, Indiana 47408 (United States)
  2. Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830 (United States)
  3. National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States)
  4. Ceraco Ceramic Coating GmbH, Ismaning 85737 (Germany)
  5. Adelphi Technology Inc., Redwood City, California 94063 (United States)
  6. (United States)
Publication Date:
OSTI Identifier:
22254861
Resource Type:
Journal Article
Resource Relation:
Journal Name: Review of Scientific Instruments; Journal Volume: 85; Journal Issue: 5; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; COUPLING; CRYOGENIC FLUIDS; DEPOLARIZATION; EQUIPMENT; HIGH-TC SUPERCONDUCTORS; MAGNETIC FIELDS; NEUTRON BEAMS; NEUTRONS; PRISMS; SPIN; SPIN ECHO

Citation Formats

Li, F., E-mail: fankli@indiana.edu, Parnell, S. R., Wang, T., Baxter, D. V., Hamilton, W. A., Maranville, B. B., Semerad, R., Cremer, J. T., Pynn, R., and Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830. Superconducting magnetic Wollaston prism for neutron spin encoding. United States: N. p., 2014. Web. doi:10.1063/1.4875984.
Li, F., E-mail: fankli@indiana.edu, Parnell, S. R., Wang, T., Baxter, D. V., Hamilton, W. A., Maranville, B. B., Semerad, R., Cremer, J. T., Pynn, R., & Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830. Superconducting magnetic Wollaston prism for neutron spin encoding. United States. doi:10.1063/1.4875984.
Li, F., E-mail: fankli@indiana.edu, Parnell, S. R., Wang, T., Baxter, D. V., Hamilton, W. A., Maranville, B. B., Semerad, R., Cremer, J. T., Pynn, R., and Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830. 2014. "Superconducting magnetic Wollaston prism for neutron spin encoding". United States. doi:10.1063/1.4875984.
@article{osti_22254861,
title = {Superconducting magnetic Wollaston prism for neutron spin encoding},
author = {Li, F., E-mail: fankli@indiana.edu and Parnell, S. R. and Wang, T. and Baxter, D. V. and Hamilton, W. A. and Maranville, B. B. and Semerad, R. and Cremer, J. T. and Pynn, R. and Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830},
abstractNote = {A magnetic Wollaston prism can spatially split a polarized neutron beam into two beams with different neutron spin states, in a manner analogous to an optical Wollaston prism. Such a Wollaston prism can be used to encode the trajectory of neutrons into the Larmor phase associated with their spin degree of freedom. This encoding can be used for neutron phase-contrast radiography and in spin echo scattering angle measurement (SESAME). In this paper, we show that magnetic Wollaston prisms with highly uniform magnetic fields and low Larmor phase aberration can be constructed to preserve neutron polarization using high temperature superconducting (HTS) materials. The Meissner effect of HTS films is used to confine magnetic fields produced electromagnetically by current-carrying HTS tape wound on suitably shaped soft iron pole pieces. The device is cooled to ∼30 K by a closed cycle refrigerator, eliminating the need to replenish liquid cryogens and greatly simplifying operation and maintenance. A HTS film ensures that the magnetic field transition within the prism is sharp, well-defined, and planar due to the Meissner effect. The spin transport efficiency across the device was measured to be ∼98.5% independent of neutron wavelength and energizing current. The position-dependent Larmor phase of neutron spins was measured at the NIST Center for Neutron Research facility and found to agree well with detailed simulations. The phase varies linearly with horizontal position, as required, and the neutron beam shows little depolarization. Consequently, the device has advantages over existing devices with similar functionality and provides the capability for a large neutron beam (20 mm × 30 mm) and an increase in length scales accessible to SESAME to beyond 10 μm. With further improvements of the external coupling guide field in the prototype device, a larger neutron beam could be employed.},
doi = {10.1063/1.4875984},
journal = {Review of Scientific Instruments},
number = 5,
volume = 85,
place = {United States},
year = 2014,
month = 5
}
  • The neutron Larmor diffraction technique has been implemented using superconducting magnetic Wollaston prisms in both single-arm and double-arm configurations. Successful measurements of the coefficient of thermal expansion of a single-crystal copper sample demonstrates that the method works as expected. Our experiment involves a new method of tuning by varying the magnetic field configurations in the device and the tuning results agree well with previous measurements. The difference between single-arm and double-arm configurations has been investigated experimentally. Here, we conclude that this measurement benchmarks the applications of magnetic Wollaston prisms in Larmor diffraction and shows in principle that the setup canmore » be used for inelastic phonon line-width measurements. The achievable resolution for Larmor diffraction is comparable to that using Neutron Resonance Spin Echo (NRSE) coils. Furthermore, the use of superconducting materials in the prisms allows high neutron polarization and transmission efficiency to be achieved.« less
  • A double-Wollaston prism laser differential interferometer (LDI) has been developed to observe, for the first time, the evolution of the imploding current sheath (CS) and the high temperature and high density plasma pinch in the plasma focus. The light source is a Q-switched and frequency-doubled YAG laser operated in a single-pulse mode: {lambda}=532 nm, the pulse width (FWHM) about 10 nm (also the resolution time of the LDI). The LDI measures density gradients and has a line sensitivity of about n{sub e}{sup {prime}}=(2.58{plus_minus}0.46){times}10{sup 25} m{sup {minus}4} for a typical sheath thickness of 1.6 mm and a minimum distinguishable fringe shiftmore » of 5{percent}, and a spatial resolution of 1.26 mm. The density gradient and equivalent density of the CS are measured to be n{sub e}{sup {prime}}{approx}(2.58{plus_minus}0.46){times}10{sup 26} m{sup {minus}4} and n{sub e}{approx}(3.25{plus_minus}0.59){times}10{sup 23} m{sup {minus}3}, respectively. More importantly in this article, the double-Wollaston prism LDI, with a simple optical arrangement, gives direct physical pictures of the high density gradient plasma configuration and structure which are of interest in studying the status of plasma motion. {copyright} {ital 1997 American Institute of Physics.}« less