Decay of the Diocotron Rotation and Transport in a New Low-Density Asymmetry-Dominated Regime

Sarid, E.; Gilson, Erik; Fajans, J.

doi:10.1103/physrevlett.89.105002

Cited by 10 publications

(8 citation statements)

References 8 publications

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“…Here, we are keeping the fraction of trapped particles N L tr /N L ϰV sq / p constant. These scalings were observed in early experiments [5][6][7]26 without a clear understanding of the underlying transport mechanism.…”

Section: Transport With Electric Trappingmentioning

confidence: 79%

Trapped particles and asymmetry-induced transport

Kabant︠s︡ev

Lynch

et al. 2003

Physics of Plasmas

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Trapped particle modes and the associated asymmetry-induced transport are characterized experimentally in cylindrical electron plasmas. Axial variations in the electric or magnetic confinement fields cause the particle trapping, and enable the E×B drift trapped-particle modes. Collisional diffusion across the trapping separatrix causes the modes to damp, and causes bulk radial transport when the confinement fields also have θ asymmetries. The measured asymmetry-induced transport rates are directly proportional to the measured mode damping rates, with simple scalings for all other plasma parameters. Significant transport is observed for even weak trapping fields (δB/B∼10−3), possibly explaining the “anomalous” background transport observed so ubiquitously in single species plasmas.

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Section: Transport With Electric Trappingmentioning

confidence: 79%

Trapped particles and asymmetry-induced transport

Kabant︠s︡ev

Lynch

et al. 2003

Physics of Plasmas

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“…5,6 There has been much previous work on diocotron mode instabilities 2,7-9 and on diocotron mode damping. 5,6,[10][11][12][13] This paper focus on damping.…”

Section: Introductionmentioning

confidence: 99%

Flux-driven algebraic damping of m = 1 diocotron mode

Chim

O’Neil

2016

Physics of Plasmas

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Recent experiments with pure electron plasmas in a Malmberg-Penning trap have observed the algebraic damping of m ¼ 1 diocotron modes. Transport due to small field asymmetries produces a low density halo of electrons moving radially outward from the plasma core, and the mode damping begins when the halo reaches the resonant radius r ¼ R w at the wall of the trap. The damping rate is proportional to the flux of halo particles through the resonant layer. The damping is related to, but distinct from, spatial Landau damping, in which a linear wave-particle resonance produces exponential damping. This paper explains with analytic theory the new algebraic damping due to particle transport by both mobility and diffusion. As electrons are swept around the "cat's eye" orbits of the resonant wave-particle interaction, they form a dipole (m ¼ 1) density distribution. From this distribution, the electric field component perpendicular to the core displacement produces E Â B-drift of the core back to the axis, that is, damps the m ¼ 1 mode. The parallel component produces drift in the azimuthal direction, that is, causes a shift in the mode frequency.

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“…Moreover, for the dominant electrostatic asymmetry presumed in Ref. [11], Eq. (3) gives γ m ∝ ν/ f B −3 N −1 L V 4 a ; and this N −1 L scaling was indeed observed.…”

Section: Possible Examplesmentioning

confidence: 99%

“…The measurements of transport from applied electric and magnetic asymmetries [7,8,9, 10] also should be compared to TPM predictions. "Anomalous" damping of diocotron modes [7,11,12] is almost certainly related to TPM effects, since TPM damping scales as B −3 . TPM transport also has important implications for containment of large numbers of positrons or pBars, since the TPM loss rate for magnetic asymmetries scales as total charge Q 2 , independent of length.…”

Section: Introductionmentioning

confidence: 99%

Trapped-Particle-Mediated Damping and Transport

Driscoll¹,

Kabant︠s︡ev²,

Hilsabeck³

et al. 2003

AIP Conference Proceedings

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Abstract. Weak axial variations in B(z) or φ (z) in Penning-Malmberg traps cause some particles to be trapped locally. This causes a velocity-space separatrix between trapped and passing populations, and collisional separatrix diffusion then causes mode damping and asymmetry-induced transport. This separatrix dissipation scales with collisionality as ν 1/2 , so it dominates in low collisionallity plasmas. The confinement lifetime in the "CamV" apparatus was dominated by a weak magnetic ripple with δ B/B ∼ 10 −3 , and it appears likely that the ubiquitous (L/B) −2 lifetime scalings and other applied asymmetry scalings represent similar TPM effects. TPM transport will limit the containment of large numbers of positrons orps, since TPM loss rates generally scale as total charge Q 2 , independent of length.

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Decay of the Diocotron Rotation and Transport in a New Low-Density Asymmetry-Dominated Regime

Cited by 10 publications

References 8 publications

Trapped particles and asymmetry-induced transport

Trapped particles and asymmetry-induced transport

Flux-driven algebraic damping of m = 1 diocotron mode

Trapped-Particle-Mediated Damping and Transport

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