Characterization of the pedestal in Alcator C-Mod ELMing H-modes and comparison with the EPED model

Walk, J.; Snyder, P. B.; Hughes, J.W.; Terry, J. L.; Hubbard, A.; Phillips, P. E.

doi:10.1088/0029-5515/52/6/063011

Cited by 33 publications

(53 citation statements)

References 36 publications

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“…A consistent pattern is observed at other current points, with the suppressed temperature at the highest current point explained by relatively low P net /n e . This behavior is generally consistent with the behavior observed in H-modes; a comparable sensitivity of the pedestal (in density, temperature, and pressure) to plasma current is observed in ELMy H-modes [33], although the sensitivity of the temperature pedestal is spread at a given current point is due to varying power per particle (see Fig. 5).…”

Section: B Temperature Pedestalsupporting

confidence: 85%

“…The temperature pedestal is found to scale strongly with plasma current and heating power per particle, T e,ped ∼ P net /n e . The pressure pedestal, likewise, exhibits a scaling p ped ∼ I p , comparable to ELMy H-mode on C-Mod [33]. Moreover, the pedestal pressure scales strongly with heating power, p ped ∼ n e T e ∼ P net -a significantly stronger response than in ELMy or EDA H-modes on C-Mod, and consistent with the observed weak degradation of global energy confinement with heating power in I-mode [20,46].…”

Section: Discussionsupporting

confidence: 64%

“…This is reflected in plasma parameters by the scaling ∇p ped ∼ I 2 p , as has been observed in ELMy H-mode experiments [33]. More simply, as pedestal width typically varies over a small range for a given operating configuration [43], we may express the ballooning MHD limit as a simple limit on pedestal pressure normalized to the poloidal field, β p,ped .…”

Section: A H-mode Baselinesmentioning

confidence: 87%

“…This method is also used for the MHD stability component of the predictive EPED model [26][27][28]. MHD stability modeling has been successfully applied on C-Mod in ELMy [33] and EDA [34] H-modes, and in extensive cross-machine H-mode studies [25].…”

Section: Mhd Modelingmentioning

confidence: 99%

“…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. We apply a similar approach to the study of I-mode pedestals.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

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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Section: B Temperature Pedestalsupporting

confidence: 85%

Section: Discussionsupporting

confidence: 64%

Section: A H-mode Baselinesmentioning

confidence: 87%

Section: Mhd Modelingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

et al. 2014

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Parameter dependence of density pedestal width and correlation with pedestal turbulence in EAST type-I ELMy H-mode plasma

Zhang

Tang

et al. 2023

Physics Letters A

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Projections of H-mode access and edge pedestal in the SPARC tokamak

et al. 2020

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In order to inform core performance projections and divertor design, the baseline SPARC tokamak plasma discharge is evaluated for its expected H-mode access, pedestal pressure and edge-localized mode (ELM) characteristics. A clear window for H-mode access is predicted for full field DT plasmas, with the available 25 MW of design auxiliary power. Additional alpha heating is likely needed for H-mode sustainment. Pressure pedestal predictions in the developed H-mode are surveyed using the EPED model. The projected SPARC pedestal would be limited dominantly by peeling modes and may achieve pressures in excess of 0.3 MPa at a density of approximately 3 × 1020 m−3. High pedestal pressure is partially enabled by strong equilibrium shaping, which has been increased as part of recent design iterations. Edge-localized modes (ELMs) with >1 MJ of energy are projected, and approaches for reducing the ELM size, and thus the peak energy fluence to divertor surfaces, are under consideration. The high pedestal predicted for SPARC provides ample margin to satisfy its high fusion gain (Q) mission, so that even if ELM mitigation techniques result in a 2× reduction of the pedestal pressure, Q > 2 is still predicted.

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Characterization of the pedestal in Alcator C-Mod ELMing H-modes and comparison with the EPED model

Cited by 33 publications

References 36 publications

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

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

Parameter dependence of density pedestal width and correlation with pedestal turbulence in EAST type-I ELMy H-mode plasma

Projections of H-mode access and edge pedestal in the SPARC tokamak

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