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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 5626-5631 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Relaxation time constants of electron polarization, 〈Sz〉, for optically pumped rubidium atoms in a drifilm coated glass cell have been investigated with the Faraday rotation method. The dependence of the 〈Sz〉 relaxation time on pump cell temperature, rubidium density and applied magnetic field has been determined with high precision. The measurements allow the determination of the local magnetic field on the surface, alkali-wall binding energy and wall-dwell time. Furthermore, the change of relaxation time caused by admixtures of molecular hydrogen, nitrogen and oxygen has been investigated. No influence due to the addition of hydrogen could be detected up to a density of 3.3×1014 cm−3 at typical rubidium densities of several 1011 cm−3. The cross section for depolarizing collisons with molecular oxygen has been determined to be 7.50×10−15 cm2. The corresponding cross section for nitrogen was found to be two orders of magnitude lower. The experimental results are discussed in respect to the performance of spin exchange sources for nuclear polarized hydrogen and deuterium. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1434-6079
    Keywords: PACS. 47.45.Dt Free molecular flows – 51.20.+d Viscosity, diffusion, and thermal conductivity – 29.25.Pj Polarized and other targets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The use of storage cells has become a standard technique for internal gas targets in conjunction with high energy storage rings. In case of spin-polarized hydrogen and deuterium gas targets the interaction of the injected atoms with the walls of the storage cell can lead to depolarization and recombination. Thus the number of wall collisions of the atoms in the target gas is important for modeling the processes of spin relaxation and recombination. It is shown in this article that the diffusion process of rarefied gases in long tubes or storage cells can be described with the help of the one-dimensional diffusion equation. Mathematical methods are presented that allow one to calculate collision age distributions (CAD) and their moments analytically. These methods provide a better understanding of the different aspects of diffusion than Monte Carlo calculations. Additionally it is shown that measurements of the atomic density or polarization of a gas sample taken from the center of the tube allow one to determine the possible range of the corresponding density weighted average values along the tube. The calculations are applied to the storage cell geometry of the HERMES internal polarized hydrogen and deuterium gas target.
    Type of Medium: Electronic Resource
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