Fracture Strength of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi>AlLiB</mml:mi><mml:mn>14</mml:mn></mml:msub></mml:math>

Wan, Liwen F.; Beckman, Scott P.

doi:10.1103/physrevlett.109.145501

Cited by 37 publications

(63 citation statements)

References 39 publications

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“…The insensitivity of the global KBM stability to the details of the q-profile agrees with the global analysis by Wan et al [26] for the intermediate-n KBMs that were not affected by the change in q-profile. All the equilibria used in this paper were stable for low-n peeling-ballooning modes that were found to be stabilised by the qprofile flattening in [26].…”

Section: Discussionsupporting

confidence: 76%

“…We believe that the global gyrokinetic modes that are presented in Figs. 9 a) and 10 a) are the same KBMs that were found in [26] (KBM torodial mode numbers for conventional aspect ratio tokamak DIII-D analysis in [26] are the same as those for JET in this paper. They are slightly lower for the tight aspect ratio tokamak MAST).…”

Section: Discussionsupporting

confidence: 58%

“…All the equilibria used in this paper were stable for low-n peeling-ballooning modes that were found to be stabilised by the qprofile flattening in [26]. Low-n MHD modes tend to be peeling-ballooning modes (PBM) in the pedestal, and these are not captured in the lowest order gyrokinetic model used in codes like GS2 and ORB5.…”

Section: Discussionmentioning

confidence: 99%

“…The point is that equilibrium parallel current density gradient drive that is necessary to describe PBMs is missing from the local non-shifted Maxwellian background distribution function f 0 used here [24]. In [26], where the gyrokinetic model must have been extended somehow to include the current gradient drive, the stabilising effect of flattening qprofile was found for low-n modes (identified as kinetic peeling-ballooning mode, or peeling-ballooning mode in [27]). However the KBMs with n=20-60 in [26] are affected only slightly and actually destabilised by the q-profile flattening.…”

Section: Discussionmentioning

confidence: 99%

“…In [26], where the gyrokinetic model must have been extended somehow to include the current gradient drive, the stabilising effect of flattening qprofile was found for low-n modes (identified as kinetic peeling-ballooning mode, or peeling-ballooning mode in [27]). However the KBMs with n=20-60 in [26] are affected only slightly and actually destabilised by the q-profile flattening. We believe that the global gyrokinetic modes that are presented in Figs.…”

Section: Discussionmentioning

confidence: 99%

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Non-local effects on pedestal kinetic ballooning mode stability

Saarelma

Martin-Collar

Dickinson

et al. 2017

Plasma Phys. Control. Fusion

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The H-mode pedestal height plays an important role in determining the global confinement of the tokamak plasma. In type I ELMy H-mode the ultimate limit for the pedestal pressure at constant width is set by the ideal MHD peeling-ballooning modes that are thought to be the trigger for the ELMs. However, the peeling-ballooning mode criterion does not uniquely determine the pedestal. Increasing the width of the pedestal, the marginally peeling-ballooning stable pedestal height increases as well. The second criterion for the pedestal is set by the transport processes in the pedestal that limit the gradient between the ELMs.One candidate for driving this transport is the kinetic ballooning mode (KBM) that is driven by the pressure gradient Non-Local Effects on Pedestal Kinetic Ballooning Mode Stability 2 with the pressure gradient clamped near to the stability limit. In the local linear gyrokinetic analysis of experimental MAST and JET plasmas we have found that, like the n=∞ ideal MHD ballooning modes, the KBMs can access locally so called second stability if the magnetic shear becomes low enough [2,3]. However, in the pedestal region the local assumption that the equilibrium can be considered radially constant for the investigated modes is no longer justified. In this paper we revisit the KBM analysis using a global code ORB5 to investigate whether second stability access exists for KBMs.We find that counter to the local analysis, the global KBM stability is not sensitive to the magnetic shear in the pedestal region. At sufficiently high β (but still below the ideal peeling-ballooning limit) the pedestal region becomes KBM unstable regardless of the amount of bootstrap current assumed in the equilibrium reconstruction. However, just as in local analysis, the mode is stabilised by reducing the pressure gradient. This suggests that KBMs can regulate the pedestal pressure gradient during the ELM cycle even when local analysis finds them stable due to high bootstrap current.

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Section: Discussionsupporting

confidence: 76%

Section: Discussionsupporting

confidence: 58%

Section: Discussionmentioning

confidence: 99%