Edge transport barriers in magnetic fusion plasmas

Gohil, P.

doi:10.1016/j.crhy.2006.06.006

Cited by 14 publications

(6 citation statements)

References 130 publications

(154 reference statements)

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“…The physics of transport barriers is a broad subject that is already covered by several overview papers for external [307][308][309][310] and internal transport barriers [311][312][313]. Two generic key parameters are known to play a stabilizing role: flow shear and magnetic shear.…”

Section: Improved Confinementmentioning

confidence: 99%

Gyrokinetic simulations of turbulent transport

et al. 2010

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This overview is an assessment of the gyrokinetic framework and simulations to compute turbulent transport in fusion plasmas. It covers an introduction to the gyrokinetic theory, the principal numerical techniques which are being used to solve the gyrokinetic equations, fundamentals in gyrokinetic turbulence and the main results which have been brought by simulations with regard to transport in fusion devices and fluctuation measurements.

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Section: Improved Confinementmentioning

confidence: 99%

Gyrokinetic simulations of turbulent transport

et al. 2010

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“…It is well known that turbulent transport on the edge of the plasma column strongly influences the confinement of particles and energy of a fusion device [1,2]. It is also well known that the typical transition of the low confinement mode (L-mode) to the high confinement mode (H-mode) is associated with the formation of an edge transport barrier (ETB) [3,4]. After decades of H-mode studies [5], there are two important phenomena that should be pointed out from the experiments.…”

Section: Introductionmentioning

confidence: 99%

“…(2) The poloidal momentum balance equation consists of the fluctuationdriven Reynolds stress, the collisional bulk plasma diffusion, neoclassical poloidal flow damping and the ion-loss cone near the separatrix, which is related to provide a negative feedback control for LCO during the I-phase. (3) The Reynolds stress is enhanced by increasing turbulence assisting the diamagnetic flow to lead the E × B flow shear intensity to prematurely achieve the critical point of the microscopic turbulent quenching, thus triggering the L-I transition. Finally, a novel time-dependent one-dimensional (in radius) dynamical model is composed of these five coupled macro fields to investigate the L-I-H transition and H-mode power scaling.…”

Section: Introductionmentioning

confidence: 99%

One-dimensional modelling of limit-cycle oscillation and H-mode power scaling

Wan

et al. 2015

Nucl. Fusion

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To understand the connection between the dynamics of microscopic turbulence and the macroscale power scaling in the L-I-H transition in magnetically confined plasmas, a new time-dependent, one-dimensional (in radius) model has been developed. The model investigates the radial force balance equation at the edge region of the plasma and applies the quenching effect of turbulence via the E × B flow shear rate exceeding the shear suppression threshold. By slightly ramping up the heating power, the spatio-temporal evolution of turbulence intensity, density and pressure profiles, poloidal flow and E × B flow selfconsistently displays the L-H transition with an intermediate phase (I-phase) characterized by limit-cycle oscillations. Since the poloidal flow is partially damped to the neoclassical flow in the edge region, the numerical results reveal two different oscillation relationships between the E × B flow and the turbulence intensity depending on which oscillation of the diamagnetic flow or poloidal flow is dominant. Specifically, by including the effects of boundary conditions of density and temperature, the model results in a linear dependence of the H-mode access power on the density and magnetic field. These results imply that the microscopic turbulence dynamics and the macroscale power scaling for the L-H transition are strongly connected.

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“…The achievement of a high confinement mode, or H-mode, in ITER is widely considered necessary to reach the operational goals of the project: namely, a burning plasma with a ratio of fusion power generated to input power of 10 [1,2]. The improved confinement in H-mode operation is partly attributed to the development of an edge transport barrier (ETB) that restricts the transport of particles and heat into the scrapeoff layer (SOL), thus reducing losses to the wall along open field lines [3]. The ETB then builds up a region of steep gradients in temperature and density near the plasma edge known as the H-mode pedestal.…”

Section: Introductionmentioning

confidence: 99%

Two-dimensional characterization of ELM precursors in NSTX

et al. 2012

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Gas puff imaging has been used to capture the two-dimensional evolution of edge-localized mode (ELM) precursors. Precursor events were observed preceding ELMs and ELM-induced H–L back-transitions in radio-frequency heated H-mode plasmas, and the growth of the precursor mode through the ELM filamentation was imaged in the plane perpendicular to the local B-field. Strong edge intensity modulations appeared to propagate in the electron diamagnetic direction while steadily drifting radially outwards. Intensity fluctuations were observed at frequencies around 20 kHz and wavenumbers of 0.05–0.2 cm−1. Upon growing to a trigger point, precursor fluctuations were seen to form filamentary structures and move into the scrape-off layer (SOL) explosively with radial velocities peaking at 8 km s−1. Once in the SOL, filaments reverse their propagation direction and travel in the ion diamagnetic direction. Edge intensity fluctuations are strongly correlated with magnetic signals from Mirnov coils, and toroidally distributed coils estimated toroidal mode numbers of n = 5–10. Quantitatively similar precursors have been observed in ohmic H-mode plasmas as well, though significantly fewer events are seen in the ohmic cases and none were observed in the near-threshold NBI H-modes studied.

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Edge transport barriers in magnetic fusion plasmas

Cited by 14 publications

References 130 publications

Gyrokinetic simulations of turbulent transport

Gyrokinetic simulations of turbulent transport

One-dimensional modelling of limit-cycle oscillation and H-mode power scaling

Two-dimensional characterization of ELM precursors in NSTX

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