Dependence of enhanced asymmetryinduced transport on collision frequency
Abstract
A singleparticle code with collisional effects is used to study how asymmetryinduced radial transport in a nonneutral plasma depends on collision frequency. For asymmetries of the form ϕ{sub 1}(r) cos(kz) cos(ωt−lθ), two sources for the transport have been identified: resonant particles and axially trapped particles. The simulation shows that this latter type, which occurs near the radius where ω matches the azimuthal rotation frequency ω{sub R}, is usually dominant at low collision frequency ν but becomes negligible at higher ν. This behavior can be understood by noting that axially trapped particles have a lower trapping frequency than resonant particles. In the low ν (banana) regime, the radial oscillations have amplitude Δr ≈ v{sub r}/ω{sub T}, so axially trapped particles dominate, and the transport may even exceed the resonant particle plateau regime level. As ν increases, collisions start to interrupt the slower axially trapped particle oscillations, while the resonant particles are still in the banana regime, so the axially trapped particle contribution to the transport decreases. At the largest ν values, axially trapped particle transport is negligible and the observed diffusion coefficient matches that given by plateau regime resonant particle theory. Heuristic models based on these considerations give reasonable agreement with the observed scaling lawsmore »
 Authors:
 Occidental College, Physics Department, Los Angeles, California 90041 (United States)
 Publication Date:
 OSTI Identifier:
 22299824
 Resource Type:
 Journal Article
 Resource Relation:
 Journal Name: Physics of Plasmas; Journal Volume: 21; Journal Issue: 7; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; AMPLITUDES; ASYMMETRY; BANANA REGIME; COLLISIONS; PLASMA; PLATEAU REGIME; SIMULATION
Citation Formats
Eggleston, D. L. Dependence of enhanced asymmetryinduced transport on collision frequency. United States: N. p., 2014.
Web. doi:10.1063/1.4891661.
Eggleston, D. L. Dependence of enhanced asymmetryinduced transport on collision frequency. United States. doi:10.1063/1.4891661.
Eggleston, D. L. 2014.
"Dependence of enhanced asymmetryinduced transport on collision frequency". United States.
doi:10.1063/1.4891661.
@article{osti_22299824,
title = {Dependence of enhanced asymmetryinduced transport on collision frequency},
author = {Eggleston, D. L.},
abstractNote = {A singleparticle code with collisional effects is used to study how asymmetryinduced radial transport in a nonneutral plasma depends on collision frequency. For asymmetries of the form ϕ{sub 1}(r) cos(kz) cos(ωt−lθ), two sources for the transport have been identified: resonant particles and axially trapped particles. The simulation shows that this latter type, which occurs near the radius where ω matches the azimuthal rotation frequency ω{sub R}, is usually dominant at low collision frequency ν but becomes negligible at higher ν. This behavior can be understood by noting that axially trapped particles have a lower trapping frequency than resonant particles. In the low ν (banana) regime, the radial oscillations have amplitude Δr ≈ v{sub r}/ω{sub T}, so axially trapped particles dominate, and the transport may even exceed the resonant particle plateau regime level. As ν increases, collisions start to interrupt the slower axially trapped particle oscillations, while the resonant particles are still in the banana regime, so the axially trapped particle contribution to the transport decreases. At the largest ν values, axially trapped particle transport is negligible and the observed diffusion coefficient matches that given by plateau regime resonant particle theory. Heuristic models based on these considerations give reasonable agreement with the observed scaling laws for the value of the collision frequency where axially trapped particle transport starts to decrease and for the enhancement of the diffusion coefficient produced by axially trapped particles.},
doi = {10.1063/1.4891661},
journal = {Physics of Plasmas},
number = 7,
volume = 21,
place = {United States},
year = 2014,
month = 7
}

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