The transport of ions in a turbulent plasma

McWilliams, R.; Okubo, M.; Wolf, N. S.

doi:10.1063/1.859342

Cited by 17 publications

(5 citation statements)

References 30 publications

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“…[6][7][8][9][10] However, quantitative comparison between tokamak experiments and simulations is difficult due to the indirect and limited fast ion diagnostic abilities in hot plasmas. Several experimental works [11][12][13] in a basic linear device reported that ion heating and transport is enhanced under large electrostatic fluctuations. Measurement of energetic particles in a toroidal magnetized basic plasma device (TOR-PEX) has also begun.…”

Section: Introductionmentioning

confidence: 99%

Dependence of fast-ion transport on the nature of the turbulence in the Large Plasma Device

et al. 2011

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Strong turbulent waves (dn=n $0.5, f $5-40 kHz) are observed in the upgraded Large Plasma Device [W. Gekelman, H. Pfister, Z. Lucky, J. Bamber, D. Leneman, and J. Maggs, Rev. Sci. Instrum. 62, 2875] on density gradients produced by an annular obstacle. Energetic lithium ions (E fast = T i ! 300, q fast =q s $ 10) orbit through the turbulent region. Scans with a collimated analyzer and with probes give detailed profiles of the fast ion spatial distribution and of the fluctuating wave fields. The characteristics of the fluctuations are modified by changing the plasma species from helium to neon and by modifying the bias on the obstacle. Different spatial structure sizes (L s ) and correlation lengths (L corr ) of the wave potential fields alter the fast ion transport. The effects of electrostatic fluctuations are reduced due to gyro-averaging, which explains the difference in the fast-ion transport. A transition from super-diffusive to sub-diffusive transport is observed when the fast ion interacts with the waves for most of a wave period, which agrees with theoretical predictions.

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Section: Introductionmentioning

confidence: 99%

Dependence of fast-ion transport on the nature of the turbulence in the Large Plasma Device

et al. 2011

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“…LIF is a nonperturbing, in situ diagnostic capable of measuring ion velocity distributions ͑including convection͒, [1][2][3][4][5][6] direct ion transport, 7 spatial diffusion, [8][9][10][11] velocity space diffusion and stochastic heating, [12][13][14][15][16] and phase space densities. 17,18 The technique described in this article relies upon a reduction of detected intensity due to a laser ion tagging process.…”

Section: Introductionmentioning

confidence: 99%

Single beam laser induced fluorescence technique for plasma transport measurements

Edrich

McWilliams

Wolf

1996

Review of Scientific Instruments

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A technique for measuring ion transport using laser-induced fluorescence has been developed and tested in an argon plasma. It uses only one broadband beam thus being simpler than some previous techniques because no detection beam is required. First, a 5 s laser pulse centered on 611 nm stimulates a transition from the metastable state in Ar͑II͒ 3d 2 G 9/2 to 4 p 2 F 7/2 0 . A 4p 2 F 7/2 0 to 4s 2 D 5/2 transition rapidly results with emission at 461 nm. Upon cessation of the laser pulse, the 461 nm light in the detection volume does not return to its background level immediately because the 3d 2 G 9/2 level is partially depleted. The time history of the 461 nm signal in returning to steady-state background intensity provides a means of determining ion transport because the recovery signal is due to processes including ion excitation, diffusion, convection, and thermal motion. Measurements of the ion velocity distribution yield the contributions of thermal and convective effects to ion transport. By varying the laser beam diameter and the detection volume the plasma ion spatial diffusion coefficient D, and the time, p it takes for processes other than transport to bring the 461 nm emission back to the steady-state background level are determined. For example, in one set of plasma conditions Dϭ0.58Ϯ0.16 m 2 /s and p ϭ59Ϯ7 s were found.

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“…9 There, D Ќ was measured in Ba ϩ /e Ϫ Q plasmas in the presence of broadband, low-frequency noise ( f ϳ50 kHzϳ f ci Ӷ f pi , f pe , f ce ) generated from parametric decay of antenna-launched lower hybrid waves into electrostatic ion cyclotron waves. A linear dependence of D Ќ on (␦n/n) rms was inferred experimentally for 0.002р(␦n/n) rms р0.04 ͑see Fig.…”

Section: Discussionmentioning

confidence: 99%

“…6,7 Edge electrostatic fluctuations have been correlated with significant particle losses in the Madison Symmetric Torus ͑MST͒. 8 Sensitive measurements of ion cross-field transport versus density fluctuation levels have been made in Q-machine plasmas 9 and in the Columbia Linear Machine. 10 Low-frequency turbulence is a universal feature in tokamaks; 11,12 in particular, resistivity gradient driven turbulence and collisional density gradient driven turbulence are believed to drive transport in edge plasmas, while drift wave turbulence is believed to dominate anomalous core transport.…”

Section: Introductionmentioning

confidence: 99%

Ion acceleration and anomalous transport in the near wake of a plasma limiter

1997

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Ion acceleration and anomalous transport were studied experimentally in the near wake region of an electrically floating disk limiter immersed in two different types of collisionless, supersonically flowing, magnetized plasmas: the first initially quiescent, the second initially turbulent. Ion densities and velocity distributions were obtained using a nonperturbing laser induced fluorescence diagnostic. Large-amplitude, low-frequency turbulence was observed at the obstacle edge and in the wake. Rapid ion and electron configuration space transport and ion velocity space transport were observed. Configuration space and velocity space transport were similar for both quiescent and turbulent plasma-obstacle systems, suggesting that plasma-obstacle effects outweigh the effects of initial plasma turbulence levels.

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The transport of ions in a turbulent plasma

Cited by 17 publications

References 30 publications

Dependence of fast-ion transport on the nature of the turbulence in the Large Plasma Device

Dependence of fast-ion transport on the nature of the turbulence in the Large Plasma Device

Single beam laser induced fluorescence technique for plasma transport measurements

Ion acceleration and anomalous transport in the near wake of a plasma limiter

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