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

Nuclear Magnetic Resonance;Longitudinal Relaxation;Low Temperature

Yoder, Jacob

关键词: Nuclear Magnetic Resonance;    Longitudinal Relaxation;    Low Temperature;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/18471/Yoder_Jacob.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

The Neutron Electric Dipole Moment (nEDM) experiment that will take place atthe Spallation Neutron Source (SNS) in Oak Ridge, Tennessee will measure the electricdipole moment (EDM) of the neutron with a precision of order 10-28 e-cm, utilizing spinpolarized3He in bulk liquid 4He to detect neutron precession in a 10 mG magnetic fieldand 50 kV/cm electric field. Since depolarized 3He will produce a background,relaxation of the polarized 3He, characterized by the probability of depolarization perbounce, Pd , was measured for materials that will be in contact with polarized 3He.Depolarization probabilities were determined from measurements of thelongitudinal relaxation time of polarized 3He in bulk liquid 4He inside an acrylic cellcoated with the wavelength shifter deuterated tetraphenyl butadiene (d-TPB), whichwill be used to coat the nEDM measurement cell. Relaxation measurements were alsoperformed while rods, made from plumbing material Torlon and valve bellows materialBeCu, were present in the cell. The BeCu was coated with Pyralin resin prior torelaxation measurements, while relaxation measurements were performed both beforeand after the Torlon rod was coated with Pyralin resin. The depolarization probabilitieswere 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 consistentwith design goals.