Magneto-hydrodynamic stability of the H-mode transport barrier as a model for edge localized modes: an overview

Wilson, H. R.; Cowley, S. C.; Kirk, A.; Snyder, P. B.

doi:10.1088/0741-3335/48/5a/s06

Cited by 136 publications

(149 citation statements)

References 46 publications

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“…In the ELM model discussed here, it is assumed that the transient event is initiated when a peeling-ballooning mode is destabilized as the pedestal pressure gradient exceeds the linear marginal stability limit of the mode [1]. This produces an initial pulse of heat and particles that propagate radially outward into a small pre-existing homoclinic separatrix tangle.…”

Section: Conceptual Description Of the Homoclinic Tangle Model For Thmentioning

confidence: 99%

“…A conceptual model describing the dynamics of the edge plasma and the evolution of the pedestal magnetic topology following the linear growth phase of a peeling-ballooning instability [1], i.e., an edge localized mode (ELM), is presented. Understanding the physics, topology and dynamics of an ELM during its post-linear growth phase is essential for predicting the size of the instability versus the pedestal plasma conditions.…”

Section: Introductionmentioning

confidence: 99%

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A conceptual model of the magnetic topology and nonlinear dynamics of ELMs

Evans

Jakubowski

et al. 2009

Journal of Nuclear Materials

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A conceptual model is introduced describing the 3D magnetic topology and nonlinear evolution of Type-I edge localized modes (ELMs), which immediately follows the initial linear peeling-ballooning growth phase. The model requires the feedback amplification of stable and unstable invariant manifolds that increases the helical perturbation. The amplification process is caused by the rapid growth of field-aligned helical thermoelectric currents that flow through relatively short pedestal plasma flux tubes connecting the inner and outer divertor target plates. It is shown that the model qualitatively agrees with the formation of global field-aligned emission filaments and with fast IR heat flux splitting patterns of the inner and outer strike points observed experimentally. In addition, the model predicts an increase in the size of the ELMs as the pedestal collisionality drops. Experimental data and modeling results are presented supporting the basic conceptual elements of the model.

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Section: Conceptual Description Of the Homoclinic Tangle Model For Thmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A conceptual model of the magnetic topology and nonlinear dynamics of ELMs

Evans

Jakubowski

et al. 2009

Journal of Nuclear Materials

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“…A firm understanding of the pedestal is essential for the extrapolation of any highperformance regime to ITER and reactor-scale devices: the pedestal structure sets a strong constraint on overall performance [4], as well as determining stability against large, deleterious ELMs. Recent cooperative efforts among theory, modeling, and experiment [25] have resulted in a predictive model, termed EPED [26][27][28], for ELMy H-mode based on coupled constraints from peeling-ballooning MHD stability [29][30][31] and kinetic-ballooning turbulence [32]. The EPED model has successfully predicted pedestal structure in ELMy H-mode on a number of machines [25,33,34] spanning a range of parameters, reaching ITER-relevant pedestal pressures in the case of H-modes on Alcator C-Mod.…”

Section: Introductionmentioning

confidence: 99%

Edge-localized mode avoidance and pedestal structure in I-mode plasmas

et al. 2014

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I-mode is a high-performance tokamak regime characterized by the formation of a temperature pedestal and enhanced energy confinement, without an accompanying density pedestal or drop in particle and impurity transport. I-mode operation appears to have naturally-occurring suppression of large ELMs in addition to its highly favorable scalings of pedestal structure and overall performance. Extensive study of the ELMy H-mode has led to the development of the EPED model, which utilizes calculations of coupled peeling-ballooning MHD modes and kinetic-ballooning mode (KBM) stability limits to predict the pedestal structure preceding an ELM crash.We apply similar tools to the structure and ELM stability of I-mode pedestals. Analysis of I-mode discharges prepared with high-resolution pedestal data from the most recent C-Mod campaign reveals favorable pedestal scalings for extrapolation to large machines -pedestal temperature scales strongly with power per particle P net /n e , and likewise pedestal pressure scales as the net heating power (consistent with weak degradation of confinement with heating power). Matched discharges in current, field, and shaping demonstrate the decoupling of energy and particle transport in I-mode, increasing fueling to span nearly a factor of two in density while maintaining matched temperature pedestals with consistent levels of P net /n e . This is consistent 2 with targets for increased performance in I-mode, elevating pedestal β p and global performance with matched increases in density and heating power. MHD calculations using the ELITE code indicate that I-mode pedestals are strongly stable to edge peeling-ballooning instabilities. Likewise, numerical modeling of the KBM turbulence onset, as well as scalings of the pedestal width with poloidal beta, indicate that I-mode pedestals are not limited by KBM turbulence -both features identified with the trigger for large ELMs, consistent with the observed suppression of large ELMs in I-mode.

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“…Investigations of pellet ELM triggering, as a method to mitigate the ELM-caused heat load on plasma facing components, have been also recently performed on JET by means of the fast visible camera [4]. The fast visible camera observations may support also the validation of existing theories concerning ELM energy transport [5] and the study of filamentary structures observed during the development of the ELM instabilities [6].…”

Section: Introductionmentioning

confidence: 99%

Application of optical flow method for imaging diagnostic in JET

Murari¹,

Alonso²,

Lang

et al. 2010

Journal of Nuclear Materials

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An optical flow method is applied to the study of several fusion plasma relevant issues, including plasma wall interactions. A multi-resolution coarse-to-fine procedure is used in order to cope with large displacements of objects between consecutive frames, characteristic of plasma images captured by JET fast visible camera. Occlusion modeling is also implemented. The method is able to provide good results for JET fast-visible camera images which can be affected by saturation, discontinuous movement, reshaping of image objects, low gray-level in-depth resolution. Significant experimental cases concerning pellet injection, plasma filaments and MARFEs are analysed. The method is able to provide the real velocity for objects moving close to structures.

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Magneto-hydrodynamic stability of the H-mode transport barrier as a model for edge localized modes: an overview

Cited by 136 publications

References 46 publications

A conceptual model of the magnetic topology and nonlinear dynamics of ELMs

A conceptual model of the magnetic topology and nonlinear dynamics of ELMs

Edge-localized mode avoidance and pedestal structure in I-mode plasmas

Application of optical flow method for imaging diagnostic in JET

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