Damping of the Trapped-Particle Diocotron Mode

Hilsabeck, T. J.; Kabant︠s︡ev, A. A.; Driscoll, C. F.; O’Neil, T. M.

doi:10.1103/physrevlett.90.245002

Cited by 14 publications

(26 citation statements)

References 5 publications

(6 reference statements)

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“…(5)(6)(7)(8) show striking correspondence to many prior results on asymmetry-induced transport. For magnetic field dependence, we expect ν p ∝ γ a (B) B −1 ∝ (B −1.5 to B −2 ), using the γ a (B) scaling of electric trapping.…”

Section: Possible Examplessupporting

confidence: 69%

“…These collisions at rate ν have been treated by a Fokker-Planck collision operator [5], in an analysis similar to that used for the dissipative trapped-ion instability by Rosenbluth, Ross, and Kostomarov [14]. Velocity space diffusion acting for one mode period smoothes out the separatrix discontinuity over a width δ v t ≈v ν/ f E , and the damping includes this dependence.…”

Section: Electric Trapping: New Modementioning

confidence: 99%

“…This surprising result is conceptually reasonable, in that the entire Maxwellian distribution of particles participates in magnetic separatrix crossings, no matter how small the separatrix angle β 1/2 . Presumably, this process ceases only when the collisional (or non-linear) separatrix width [5] becomes comparable to the trapping width.…”

Section: Common Characteristics: Separatrix Dissipationmentioning

confidence: 99%

“…Theory provides a reasonable picture of trapped-particle-mode damping with electric trapping [5], but modes in the magnetic trapping case remain enigmatic. Theory can not yet explain the observed particle transport scalings for either case, but this appears imminent for electric trapping.…”

Section: Introductionmentioning

confidence: 99%

“…Now, it appears likely that trappedparticle-mediated (TPM) effects are dominant in plasma lifetime scalings, in transport from applied asymmetries, and in diocotron mode damping. This talk will give an overview of what is known [2,3,4,5], where more experiments are needed, and where the theory is lacking.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

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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Section: Possible Examplessupporting

confidence: 69%

Section: Electric Trapping: New Modementioning

confidence: 99%

Section: Common Characteristics: Separatrix Dissipationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Trapped-Particle-Mediated Damping and Transport

Driscoll¹,

Kabant︠s︡ev²,

Hilsabeck³

et al. 2003

AIP Conference Proceedings

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Collisionless and collisional effects on plasma waves from a partition squeeze

Ashourvan

Dubin

2014

J. Plasma Phys.

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A simple 1D model is presented for the heating caused by cylindrically-symmetric plasma waves in a non-neutral plasma column due to the addition of a symmetric squeeze potential applied to the center of the column. We study this model by using analytical techniques and by using a numerical grids method solution, and we compare the results of this model to previous work (Ashourvan and Dubin (2014)). squeeze divides the plasma into passing and trapped particles; the latter cannot pass over the squeeze potential. In collisionless theory, enhanced heating is caused by additional bounce harmonics induced by the squeeze in the particle distribution, leading to Landau resonances at energies E n for which the bounce frequency ω b (E) and wave frequency ω m satisfy ω m = nω b (E n ). As a result, heating is substantially higher than the case with no squeeze, even when ω m is much greater than the thermal bounce frequency ω b (T ). Adding collisions to the theory creates a boundary layer at the separatrix between trapped and passing particles that further enhances the heating at small ω m /k m v s , where k m is the axial wavenumber and v s is the velocity at the separatrix. However, at large ω m /v s , the heating from the separatrix boundary layer is only a small correction to the heating from collisionless resonances in the trapped particle distribution function. IntroductionTrivelpiece-Gould (TG) modes are electrostatic normal modes of a cylindrical plasma column [Trivelpiece and Gould (1959)]. In this paper, we study the plasma heating (and associated wave damping) caused by cylindrically-symmetric TrivelpieceGould modes with frequency ω m and axial wave number k m , after applying a cylindrically-symmetric 'squeeze' potential to the plasma equilibrium. Without the squeeze, the heating is caused by Landau damping of the wave energy, due to resonant particles with axial velocity v equal to the wave phase velocity ω m /k m . With the squeeze, the heating is enhanced because new resonances appear in the velocity distribution. The new resonances occur because the squeeze potential changes the particle orbits, creating a non-sinusoidal time-dependence for the wave as seen in the particle frame, which induces new resonances at harmonics of the particle bounce frequency ω b , i.e. where ω m = nω b (E) for integer n (where E is the particle kinetic energy).This effect was studied in a previous paper (Ashourvan and Dubin 2014), where it was shown that the enhanced heating scales as the square of the applied squeeze potential ϕ s for small squeeze, provided that the wave phase velocity is large

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Controlling Length of Gold Nanowires with Large-Scale: X-ray Absorption Spectroscopy Approaches to the Growth Process

et al. 2007

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By utilizing the X-ray absorption approach, the gold ions evolving from the Au-Cl complex to Au rods have been elucidated. The theoretical simulation of X-ray absorption spectra further revealed the evolution of gold and concluded that ultrafine small clusters of gold (Au 13 ) formed after a reducing agent was added to the growth solution. A redesigned seed-assisted growth method, a serial addition of growth solution, was employed to achieve the goal of the consecutive support of gold. The development approach was found to successfully fabricate 1D gold nanorods/wires with a tunable size from 50 nm to 1.7 µm.

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Damping of the Trapped-Particle Diocotron Mode

Cited by 14 publications

References 5 publications

Trapped-Particle-Mediated Damping and Transport

Trapped-Particle-Mediated Damping and Transport

Collisionless and collisional effects on plasma waves from a partition squeeze

Controlling Length of Gold Nanowires with Large-Scale: X-ray Absorption Spectroscopy Approaches to the Growth Process

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