Role of impurity dynamics in resistivity-gradient-driven turbulence and tokamak edge plasma phenomena

Hahm, Tae Soo; Diamond, P. H.; Terry, P. W.; Garcia, L.; Carreras, B. A.

doi:10.1063/1.866259

Cited by 35 publications

(18 citation statements)

References 19 publications

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“…t_. Ue k2w5 (6.5) and the familiar rippling mode scaling [90]. In the simulation only the dependences upon the temperature, density and q were considered so that the scalings were reduced to X d°t _ O.1/T_/2, X dec,,_ nq2/T 1/2 and X r _ lO-2q2nl/a/T 5/_.…”

Section: Profiles On T-10mentioning

confidence: 99%

“…The associated thermal diffusiwity decreases with radius and the corresponding diffusive thermal transport is insignificant. Thus the model predicts that thermal transport in a cool, highly resistive edge plasma is caused primarily by convection [90].…”

mentioning

confidence: 96%

“…Owing to its different mode structure and dynamics the nonlinear state has a much weaker dependence upon the stabilizing parallel thermal diffusivity. A version of the theory was developed which included the effect of ir-y,trity dynamics[90].Here resistivity fluctuations are predominantly ,iriven by fluctuations in Zef! so that this mode is governed by impurity ion flow along field lines proportional to Xz = Vt2h.i/Z2vii• Since Xz << Xll the impurity gradient driven modes are significantly more robust than their temperature gradient driven analogs.…”

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confidence: 99%

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Behavior of the particle transport coefficients near the density limit in MTX

Marinak

1993

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The perturbed particle transport coefficients were determined for a range of plasma conditions in the Alcator C tokamak, a component of the Microwave Tokamak Experiment (MTX), from analysis of density perturbations created in gas modulation experiments. Density measurements from a 15 chord far-infrared interferometer were sufficiently detailed to allow radial profiles of the transport coefficients to be resolved. Gas modulation experiments were carried out on plasmas over a range of relatively low currents and a wide variety of line-averaged densities, including values near the Greenwald density limit. With this technique the perturbed diffusion coefficient D and the perturbed convection velocity V can be determined simultaneously. Measured profiles of D rise toward the outside of the plasma column in a manner generally similar to those determined previously for Xe,HP from sawtooth heat pulse propagation. Values of D are typically smaller than those of Xe,HP given for the _me line-averaged densities by a factor of 2-5. Diffusion coefficients from a series of discharges at constant current showed little variation with density through most of the saturated ohmic confinement regime. At the Greenwald density limit threshold (_e = _J) a dramatic increase occurred in both the perturbed convective and diffusive transport coefficients in the outer region of the plasma. The increases were most pronounced at the outermost range of the radii where coefficients were determined (r/a-0.8), but were apparent over a region which extended well into the plasma interior. Density profiles maintained a similar shape near the density limit, congruous with the similar behavior of the transport coefficients. No dramatic deterioration was evident in the global energy confinement. These increases in the transport coefficients occurred in regions of the plasma which had relatively low temperatures (T_ <250 ev) and were in the Pfirsch-Schlfiter collisionality regime. The variation of D in this region of these high density plasmas compared well with the scaling given in a theory of resistivity-gradient-driven turbulence. The inverse dependences on the temperature and temperature gradient were key components of the model most closely associated with this result.

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Section: Profiles On T-10mentioning

confidence: 99%

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confidence: 96%

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confidence: 99%

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Behavior of the particle transport coefficients near the density limit in MTX

Marinak

1993

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“…To the usual neoclassical fluxes [9-1 lj, we added a linear combination of estimates of drift-wave, rippling mode, and resistive ballooning effects [4,6,7,[12][13][14][15][16][17][18].…”

Section: Transport Modelmentioning

confidence: 99%

Multiple mode model of tokamak transport

Singer¹,

Ghanem²,

Bateman³

et al. 1989

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Theoretical models for radial transport of energy and particles in tokamaks due to drift waves, rippling modes, and resistive ballooning modes have been combined in a predictive transport code. The resulting unified model has been used to simulate low confinement mode (L-mode) energy confine ment scalings. Dependence of global energy confinement on electron density for the resulting model is also described.

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“…We utilize here a simple model of resistivity gradient driven turbulence 31,32 ͑RGDT͒ to derive a thermal fluctuation intensity evolution equation for inhomogeneous turbulence. The dynamics of nonlinear mode coupling are determined by three mode interactions.…”

Section: Introductionmentioning

confidence: 99%

Turbulence intensity pulse propagation with self-consistent nonlinear noise

et al. 2011

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International audienceA model of turbulence intensity spreading with self-consistent nonlinear noise is derived systematically for the simple dynamical model of resistivity gradient driven turbulence. Local effective drive, thermal conduction damping, nonlinear coupling, and spatial scattering effects are included. As a consequence of nonlinear mode coupling processes (i.e., triad mode interactions), turbulence energy can be spatially scattered, leading to turbulence propagation and spreading. However, the range of any nonlinear mode interactions of the background with a test mode is restricted to within a few mode scale widths from the test mode rational surface. The speed of a turbulent spreading front is calculated. This front speed is effectively constant on macroscopic scales. We show that the effect of self-consistent nonlinear noise on the intensity front speed is modest, as a consequence of the ordering Δc

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Role of impurity dynamics in resistivity-gradient-driven turbulence and tokamak edge plasma phenomena

Cited by 35 publications

References 19 publications

Behavior of the particle transport coefficients near the density limit in MTX

Behavior of the particle transport coefficients near the density limit in MTX

Multiple mode model of tokamak transport

Turbulence intensity pulse propagation with self-consistent nonlinear noise

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