Stochastic Ion Heating by a Perpendicularly Propagating Electrostatic Wave

Karney, Charles F. F.; Bers, A.

doi:10.1103/physrevlett.39.550

Cited by 151 publications

(90 citation statements)

References 6 publications

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“…However a de-correlation mechanism has been proposed by Karney [23,24,25] in the form of stochastic ion heating. Stochastic ion motion could arise in the presence of a lower hybrid wave (with electric field amplitude above a certain threshold) due to the nonlinear interaction of the resonances between the cyclotron motion and the wave motion even for w>>C2 [241.…”

Section: Warm Plasma Effectsmentioning

confidence: 99%

Linear Theory of Lower Hybrid Heating

Bonoli

1984

IEEE Trans. Plasma Sci.

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The linear theory of wave propagation in the lower hybrid range of frequencies is presented. The topics of accessibility, linear and quasilinear theories of electron Landau damping, and the linear theory of ion Landau damping are covered. The theory of wave propagation is extended to include the effect of toroidal geometry. A simulation model incorporating these theories is described and numerical results obtained with the model are given.

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Section: Warm Plasma Effectsmentioning

confidence: 99%

Linear Theory of Lower Hybrid Heating

Bonoli

1984

IEEE Trans. Plasma Sci.

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“…In recent years, stochastic heating of plasmas has been extensively studied, both theoretically [1][2][3] and experimentally, [4][5][6][7][8] because of its relevance to nonlinear dynamics in general and to anomalous plasma transport in particular. Almost without exception, experimental work on stochastic heating has been performed in carefully controlled ''test'' plasmas, i.e., collisionless, well-confined plasmas where the effects of particle Hamiltonian chaos could be examined without interference from collisional transport processes or other complicating effects.…”

Section: Introductionmentioning

confidence: 99%

Observations of fast anisotropic ion heating, ion cooling, and ion recycling in large-amplitude drift waves

1998

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Large-amplitude drift wave fluctuations are observed to cause severe ion temperature oscillations in plasmas of the Caltech Encore tokamak ͓J. M. McChesney, P. M. Bellan, and R. A. Stern, Phys. Fluids B 3, 3370 ͑1991͔͒. Experimental investigations of the complete ion dynamical behavior in these waves are presented. The wave electric field excites stochastic ion orbits in the plane normal (Ќ) to B, resulting in rapid Ќ heating. Ion-ion collisions impart energy along ( ʈ ) B, relaxing the Ќ-ʈ temperature anisotropy. Hot ions with large orbit radii escape confinement, reaching the chamber wall and cooling the distribution. Cold ions from the plasma edge convect back into the plasma ͑i.e., recycle͒, causing further cooling and significantly replenishing the density depleted by orbit losses. The ion-ion collision period ii ϳT 3/2 /n fluctuates strongly with the drift wave phase, due to intense (Ϸ50%͒ fluctuations in n and T. Evidence for particle recycling is given by observations of bimodal ion velocity distributions near the plasma edge, indicating the presence of cold ions ͑0.4 eV͒ superposed atop the hot ͑4-8 eV͒ plasma background. These appear periodically, synchronous with the drift wave phase at which ion fluid flow from the wall toward the plasma center peaks. Evidence is presented that such a periodic heat/loss/recycle/cool process is expected in plasmas with strong stochastic heating.

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“…Karney 7 ' 8 has shown that above an RF power threshold the ion motion, nnder the influence of the lower hybrid wave, becomes stochastic. When this threshold is far exceeded, perpendicular unmagnetized ion Landau damping can be recovered.…”

Section: Introductionmentioning

confidence: 99%

“…9 This treatment then obtains a velocity space diffusion coefficient which can be used to calculate the ion distribution function. This threshold is, 7 and E. can be determined by the RF power flux per unit area E 2w(e.. + 2(3)2k S =ir (3) For the case of Alcator A (ne ~ 2 X 101 ", Te = 900 eV, T = 800 cV, B, = 62 kG, deuterium, R = 54 cm, re = 10 cm, Pli = 70 kW and a waveguide area = 20 cm 2 ) and for k = 5w/c, we have k_ = 157/cm and E. = 25 kV/cm. This far exceeds the threshold field of Eq.…”

Section: Introductionmentioning

confidence: 99%

Quasi-linear theory calculation of ion tails and neutron rates during lower hybrid heating in Alcator-A

Schuss¹,

Antonsen²,

Porkoláb³

1983

Nucl. Fusion

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ABISTRACTThe steady state fast ion distribution function and the resulting neutron rate are calculated for the conditions of the Alcator A lower hybrid heating experiment from quasilinear theory. First, ion orbit losses are ignored and the steady state ion distribution function is calculated. It is found that in this case the experimental neutron rates and neutron rate decay times are consistent with only a small fraction of the incident RF power being absorbed in the plasma center. This absorbed power is centered in the regime 3.5 < n 1 1 < 4.5. A Monte Carlo ion simulation technique, which incorporates ripple orbit losses is then presented that calculates the steady state ion distribution function in the presence of the RF. The results of this simulation require approximately 50% of the incident RF power to be dissipated in the plasma core in order to obtain agreement with the experimental results. Most of this RF power is lost to ripple trapped ions. These calculations demonstrate the importance of orbit losses in determining lower hybrid heating efficiencies and additionally provide a technique for calculating them.

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Stochastic Ion Heating by a Perpendicularly Propagating Electrostatic Wave

Cited by 151 publications

References 6 publications

Linear Theory of Lower Hybrid Heating

Linear Theory of Lower Hybrid Heating

Observations of fast anisotropic ion heating, ion cooling, and ion recycling in large-amplitude drift waves

Quasi-linear theory calculation of ion tails and neutron rates during lower hybrid heating in Alcator-A

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