Measurement of wall relaxation times of polarized 3He in bulk liquid 4He for the Neutron Electric Dipole Moment experiment

Yoder, Jacob

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https://hdl.handle.net/2142/18471 Copy

Description

Title

Measurement of wall relaxation times of polarized 3He in bulk liquid 4He for the Neutron Electric Dipole Moment experiment

Author(s)

Yoder, Jacob

Issue Date

2011-01-14T22:51:55Z

Director of Research (if dissertation) or Advisor (if thesis)

Beck, Douglas H.

Doctoral Committee Chair(s)

Peng, Jen-Chieh

Committee Member(s)

• Beck, Douglas H.
• Errede, Steven M.
• Stone, Michael

Department of Study

Physics

Discipline

Physics

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Nuclear Magnetic Resonance
• Longitudinal Relaxation
• Low Temperature

Abstract

The Neutron Electric Dipole Moment (nEDM) experiment that will take place at the Spallation Neutron Source (SNS) in Oak Ridge, Tennessee will measure the electric dipole moment (EDM) of the neutron with a precision of order 10-28 e-cm, utilizing spinpolarized 3He in bulk liquid 4He to detect neutron precession in a 10 mG magnetic field and 50 kV/cm electric field. Since depolarized 3He will produce a background, relaxation of the polarized 3He, characterized by the probability of depolarization per bounce, Pd , was measured for materials that will be in contact with polarized 3He. Depolarization probabilities were determined from measurements of the longitudinal relaxation time of polarized 3He in bulk liquid 4He inside an acrylic cell coated with the wavelength shifter deuterated tetraphenyl butadiene (d-TPB), which will be used to coat the nEDM measurement cell. Relaxation measurements were also performed while rods, made from plumbing material Torlon and valve bellows material BeCu, were present in the cell. The BeCu was coated with Pyralin resin prior to relaxation measurements, while relaxation measurements were performed both before and after the Torlon rod was coated with Pyralin resin. The depolarization probabilities were found to be: Pd < 1.32 X 10^-7 for d-TPB; Pd = 1.01 ± 0.08 X 10^-6 for bare torlon; Pd = 2.5 ± 0.1 X 10^-7 for coated torlon; Pd = 7.9 ± 0.3 X 10^-7 for BeCu. The relaxation rates extrapolated from the observed values of Pd for d-TPB, coated Torlon, and coated BeCu in the nEDM apparatus were found to be consistent with design goals.

Graduation Semester

2010-12

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Copyright and License Information

Copyright 2010 Jacob Yoder

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