The role of MHD in causing impurity peaking in JET hybrid plasmas

Hender, T. C.; Buratti, P.; Casson, F. J.; Alper, B.; Baranov, Y.; Baruzzo, M.; Challis, C.; Koechl, F.; Lawson, K.; Marchetto, C.; Nave, M. F. F.; Pütterich, T.; Reyes-Cortes, S.; Contributors, Jet

doi:10.1088/0029-5515/56/6/066002

Cited by 42 publications

(49 citation statements)

References 41 publications

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“…Central radio frequency (RF) heating has been identified as a reliable method to limit the central concentration of heavy impurities [1][2][3][4][5][6][7][8][9]. Since the behaviour and the profile shapes of heavy impurities are determined by both turbulent [10][11][12][13][14][15][16][17][18][19][20][21][22][23] and neoclassical transport [25][26][27][28][29][30], and are also affected by the presence of magneto-hydrodynamic (MHD) instabilities [6,[31][32][33][34][35], the physics behind the reduction of the central peaking of the W density produced by central RF heating can be expected to involve a certain level of complexity, in which multiple effects are combined. Central RF heating not only modifies the temperature, density and rotation profiles of the main plasma, but can also directly modify the impurity transport.…”

Section: Introductionmentioning

confidence: 99%

A comparison of the impact of central ECRH and central ICRH on the tungsten behaviour in ASDEX Upgrade H-mode plasmas

et al. 2017

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A comparison of the impact of additional central electron cyclotron resonance heating (ECRH) and ion cyclotron resonance heating (ICRH) on the behaviour of the tungsten (W) density in the core of H-mode plasmas heated with neutral beam injection (NBI) is performed in ASDEX Upgrade. Both localized and broad profiles of the power density of the ECRH have been obtained, where broad profiles reproduce the profile shape of the ICRH power density, which is applied with a hydrogen minority heating scheme. In contrast to ECRH, which produces direct electron heating only, ICRH eventually heats both electrons and ions in almost equal fractions. It is found that both additional RF heating systems reduce the peaking of the W density profile with increasing central RF heating power. Approximately the same values of W density peaking are obtained when the same values of electron heating are produced by the two RF heating systems, which implies that less total heating power is required with ECRH than with ICRH to reduce the W density peaking. A related modelling activity shows that an important ingredient to explain the experimentally observed trend is the variation of the turbulent W diffusion as a function of the electron to ion heat flux ratio. Additional effects are connected with the more favorable W neoclassical transport convection in the presence of ICRH, produced by the combination of stronger central ion temperature gradients and the impact of the H minority on the W poloidal density asymmetry.

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Section: Introductionmentioning

confidence: 99%

A comparison of the impact of central ECRH and central ICRH on the tungsten behaviour in ASDEX Upgrade H-mode plasmas

et al. 2017

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“…Another concern related to magnetic islands is their potential to favour the inward transport of heavy impurities like tungsten towards the core plasma. This effect has been observed experimentally 30,31 and it is again attributed to the interplay of magnetic island, turbulence and neoclassical physics. Hender 30 argues that the temperature flattening inside the island on the one hand increases the neoclassical inward convection of tungsten and on the other hand decreases the diffusivity due to ITG turbulence.…”

Section: Introductionmentioning

confidence: 55%

A reduced MHD model for ITG-NTM interplay

et al. 2020

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A 6-field reduced-MHD model is derived for plasma dynamics. The new model describes coherently both Ion Temperature Gradient mode and Tearing mode, and includes neoclassical effects. The model allows the construction of an energy-like quantity with a linear pressure contribution that is conserved except for dissipative, finite Larmor radius and neoclassical terms. This model may be used to study the nonlinear interaction between ITG microturbulence and neoclassical tearing mode, which is responsible for large-scale magnetic islands in tokamaks, and opens the way to a coherent description of turbulent impurity transport in magnetic islands.

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“…In addition, magneto-hydrodynamic (MHD) instabilities such as tearing modes and sawtooth oscillations add complexity to the impurity behaviour in core plasmas. Indeed, it is observed that the presence of tearing modes locally increases the impurity diffusivity in the islands and enhances accumulation [18]. Also, discrepancies are found between the measured impurity behaviour in presence of the internal kink mode and the neoclassical and turbulent predictions [19].…”

Section: Introductionmentioning

confidence: 97%

Dynamics of heavy impurities in non-linear MHD simulations of sawtoothing tokamak plasmas

Ahn¹,

Garbet²,

Lütjens³

et al. 2016

Plasma Phys. Control. Fusion

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The effect of sawteeth on impurity dynamics is studied with the XTOR-2F code. Non-linear full 3D MHD simulations including appropriate fluid equations for heavy impurities show that the presence of regular sawtooth crashes affects the impurity behaviour. A spatial non-uniformity of 5% in post-crash impurity density profiles persists due to 2D structures of impurity density which appear during sawtooth crashes. They are shown to be mainly driven by the E × B velocity, and are responsible for the sudden impurity transport in the core plasmas.

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The role of MHD in causing impurity peaking in JET hybrid plasmas

Cited by 42 publications

References 41 publications

A comparison of the impact of central ECRH and central ICRH on the tungsten behaviour in ASDEX Upgrade H-mode plasmas

A comparison of the impact of central ECRH and central ICRH on the tungsten behaviour in ASDEX Upgrade H-mode plasmas

A reduced MHD model for ITG-NTM interplay

Dynamics of heavy impurities in non-linear MHD simulations of sawtoothing tokamak plasmas

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