The general “peeling” instability

Lortz, D.

doi:10.1088/0029-5515/15/1/007

Cited by 69 publications

(88 citation statements)

References 5 publications

(7 reference statements)

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“…On the other hand, for shaped plasmas, sufficient current density can stabilize the ballooning mode, providing access to higher pressure gradients: so-called 'second stability' regime. The other instability is the peeling mode [2], which is strongly related to the kink mode, but is not necessarily restricted to low n. The peeling mode is highly localized at the plasma edge, and is driven by the edge current density; in contrast to the ballooning mode, the peeling mode is stabilized by pressure gradient (i.e. a larger edge current density can be tolerated at higher pressure gradient).…”

Section: Introductionmentioning

confidence: 99%

Ideal magnetohydrodynamic constraints on the pedestal temperature in tokamaks

Snyder

Wilson

2003

Plasma Phys. Control. Fusion

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The ideal magnetohydrodynamic (MHD) stability limits for the edge transport barrier (ETB) region in tokamaks are explored, concentrating in particular on the intermediate to high toroidal mode number, n, modes. These calculations take full account of the effect of the edge bootstrap current on the stability of both ballooning and peeling modes. Because the current plays an important role in MHD stability, the temperature and density independently influence stability and, in particular, the pressure gradient that the ETB can support. The stability calculations therefore provide limits to the achievable temperature pedestal associated with the transport barrier which are not simply pressure pedestal limits, as is often assumed. One important result is that increasing triangularity is predicted to be beneficial in providing access to a higher temperature pedestal at fixed pedestal width, at least up to triangularity ∼0.5. Another significant result is that the finite n corrections, which are stabilizing for ballooning modes, are important for narrow pedestal widths and permit significantly higher temperature pedestals than one would obtain using the leading order (n = ∞) ballooning theory. Specific calculations for equilibria characteristic of ITER and FIRE suggest that temperature pedestals in the region of a few kiloelectronvolts should be achievable, but the precise value depends on the pedestal width, a prediction for which is beyond the scope of this paper.

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Section: Introductionmentioning

confidence: 99%

Ideal magnetohydrodynamic constraints on the pedestal temperature in tokamaks

Snyder

Wilson

2003

Plasma Phys. Control. Fusion

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“…Peeling and peeling-ballooning modes [16][17][18][19][20] are widely recognised candidates for driving edge instabilities [13,14], and are driven increasingly unstable by increasingly strong currents at the plasma's edge. Therefore they might be expected to be more strongly destabilised by a strong radially edge-localised current perturbation, as would be greatest with the most rapidly increasing kicks, and smallest with a longer and weaker kick.…”

Section: What Triggers An Elm?mentioning

confidence: 99%

Distinguishing cause from correlation in tokamak experiments to trigger edge-localised plasma instabilities

Webster

Contributors²

2014

Physics of Plasmas

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The generic question is considered: How can we determine the probability of an otherwise quasirandom event, having been triggered by an external influence? A specific problem is the quantification of the success of techniques to trigger, and hence control, edge-localised plasma instabilities (ELMs) in magnetically confined fusion (MCF) experiments. The development of such techniques is essential to ensure tolerable heat loads on components in large MCF fusion devices, and is necessary for their development into economically successful power plants. Bayesian probability theory is used to rigorously formulate the problem and to provide a formal solution. Accurate but pragmatic methods are developed to estimate triggering probabilities, and are illustrated with experimental data. These allow results from experiments to be quantitatively assessed, and rigorously quantified conclusions to be formed. Example applications include assessing whether triggering of ELMs is a statistical or deterministic process, and the establishment of thresholds to ensure that ELMs are reliably triggered.

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“…As discussed in conventional MHD books, these matching conditions are: (1) the tangential magnetic perturbation (δB t ) should be continuous; and (2) total magnetic and thermal force (B · δB + δP) should balance across plasma-vacuum interface in the case without plasma surface current. It can be proved that for localized modes the vacuum contribution is of order ǫ 2 and therefore can be neglected Lortz (1975). Consequently, the boundary condition becomes that total magnetic and thermal forces on the plasma side of the plasma-vacuum interface should vanish.…”

Section: Singular Layer Equation: Interchange and Peeling Modesmentioning

confidence: 99%

“…(50) can be alternatively obtained by the approach of minimization of plasma energy Lortz (1975) Wesson (1978.…”

Section: Singular Layer Equation: Interchange and Peeling Modesmentioning

confidence: 99%

“…In this chapter we try to give a comprehensive review of these prominent theories. Four key types of modes: interchange/peeling modes Mercier (1962) Greene & Johnson (1962) Glasser et al (1975) Lortz (1975) Wesson (1978), ballooning modes Connor et al (1979) Chance et al (1979), toroidal Alfvén egenmodes (TAEs) Cheng et al (1985) Rosenbluth et al (1992) Betti & Freidberg (1992) Zheng & Chen (1998), and kinetically driven modes, such as kinetic ballooning modes (KBMs) Tsai & Chen (1993) Chen (1994) and energetic particle driven modes (EPMs) Zheng et al (2000), are addressed. Besides, we also describe an advanced numerical method (AEGIS Zheng & Kotschenreuther (2006)) for systematically investigating MHD stability of toroidally confined fusion plasmas.…”

Section: Introductionmentioning

confidence: 99%

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