A comparison of H-mode pedestal characteristics in MAST as a function of magnetic configuration and ELM type

Kirk, A.; O’Gorman, T.; Saarelma, S.; Scannell, R.; Wilson, H. R.

doi:10.1088/0741-3335/51/6/065016

Cited by 55 publications

(79 citation statements)

References 16 publications

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“…Correlations between the pedestal width and β ped θ have been observed on many tokamaks (e.g., JT60U [4], MAST [14], and see ref. [38] for DIIID and C-MOD).…”

Section: Dynamical Evolution Of Pedestal Parameters In Nstxmentioning

confidence: 85%

Dynamical evolution of pedestal parameters in ELMy H-mode in the National Spherical Torus Experiment

Diallo¹,

Maingi²,

Kubota³

et al. 2011

Nucl. Fusion

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Abstract. Characterizations of the pedestal parameter dynamics throughout the edge localized modes(ELM) cycles are performed on the National Spherical Torus Experiment (NSTX, [M. Ono et al., Nucl. Fusion 40, 557 (2000)]). A clear buildup of the pedestal height is observed between ELMs for three different plasma currents, which tends to saturate prior to the onset of ELM at low and medium plasma current. Similarly, the pedestal width increases with no clear evidence of saturation during an ELM cycle. The maximum pedestal gradient increases as a function of plasma current, reaches a nominal value after the ELM crash, and remains constant until the end of the ELM cycle. The pedestal height just prior to the onset of ELM is shown to increase quadratically with plasma current. The pedestal width ∆ is proportional to the square-root of the poloidal β at the top of the pedestal. Coherent density fluctuations strongly increasing at the plasma edge are observed to be maximum after the ELM crash and to decay during the rest of the ELM cycle. Finally, the pedestal parameters evolution during the ELM cycle as well as the scaling with Ip of the pedestal pressure prior to the onset ELM are found to be qualitatively consistent with the peeling ballooning theory.

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“…Correlations between the pedestal width and β ped θ have been observed on many tokamaks (e.g., JT60U [4], MAST [14], and see ref. [38] for DIIID and C-MOD).…”

Section: Dynamical Evolution Of Pedestal Parameters In Nstxmentioning

confidence: 85%

Dynamical evolution of pedestal parameters in ELMy H-mode in the National Spherical Torus Experiment

Diallo¹,

Maingi²,

Kubota³

et al. 2011

Nucl. Fusion

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“…For example, type III ELMs on JET [9] and MAST [21] appear to be stable to both low-n peeling modes and high-n ballooning modes. For the case of type II ELMs on ASDEX Upgrade [8] and JET [9] stability analyses have shown, that the near double null configuration required to access type II ELMs, considerably expands the stable region in the upper right corner of the α-j diagram.…”

Section: Summary and Discussionmentioning

confidence: 99%

Comparison of small edge-localized modes on MAST and ASDEX Upgrade

Kirk

Müller

Wolfrum

et al. 2011

Plasma Phys. Control. Fusion

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Results from a set of ITPA-coordinated experiments on ASDEX Upgrade and MAST to compare the characteristics of small edge-localized modes (ELMs) are presented. In MAST a small ELM regime is established in connected double null discharges in a limited region of normalised pedestal pressure and collisionality. Type II ELMs on ASDEX Upgrade have high frequency and low energy loss and occur at high triangularity and close to double null. On both devices the transition from type I to small ELMs is connected with a similar threshold value of the pedestal collisionality. For the first time the temporal and spatial evolution of the filament structures observed during these small ELMs has been studied. The radial and toroidal velocities of the filaments in these small ELMs are slower compared to type I ELMs on both devices. The observations are compatible with the filaments in small ELMs originating closer to the last closed flux surface than is the case in type I ELMs. The toroidal mode number of the small ELMs, derived from the temporal evolution of the filaments, is typically a factor of two larger than for type I ELMs. The small ELMs on MAST have sufficient similarities to type II ELMs on ASDEX Upgrade that they should be classified as the same.

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“…80, where the pedestal width is plotted as a function of the pedestal poloidal b. 232 The NSTX pedestal width follows a D ¼ c(b h ped ) 1 dependence, which is quite different from the D ¼ c 0 (b h ped ) 0.5 scaling for MAST 230 and DIII-D. 233 The $1.0 exponent scaling observed for NSTX has been shown to be consistent with preliminary analyses using the ballooning critical technique (BCP), 234 which yielded a 0.8 exponent scaling of the pedestal width as shown in Fig. 80.…”

Section: H-mode Pedestal and Edge Localized Modes (Elms)mentioning

confidence: 97%

Recent progress on spherical torus research

Ono

Kaita

2015

Physics of Plasmas

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The spherical torus or spherical tokamak (ST) is a member of the tokamak family with its aspect ratio (A = R0/a) reduced to A ∼ 1.5, well below the normal tokamak operating range of A ≥ 2.5. As the aspect ratio is reduced, the ideal tokamak beta β (radio of plasma to magnetic pressure) stability limit increases rapidly, approximately as β ∼ 1/A. The plasma current it can sustain for a given edge safety factor q-95 also increases rapidly. Because of the above, as well as the natural elongation κ, which makes its plasma shape appear spherical, the ST configuration can yield exceptionally high tokamak performance in a compact geometry. Due to its compactness and high performance, the ST configuration has various near term applications, including a compact fusion neutron source with low tritium consumption, in addition to its longer term goal of an attractive fusion energy power source. Since the start of the two mega-ampere class ST facilities in 2000, the National Spherical Torus Experiment in the United States and Mega Ampere Spherical Tokamak in UK, active ST research has been conducted worldwide. More than 16 ST research facilities operating during this period have achieved remarkable advances in all fusion science areas, involving fundamental fusion energy science as well as innovation. These results suggest exciting future prospects for ST research both near term and longer term. The present paper reviews the scientific progress made by the worldwide ST research community during this new mega-ampere-ST era.

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A comparison of H-mode pedestal characteristics in MAST as a function of magnetic configuration and ELM type

Cited by 55 publications

References 16 publications

Dynamical evolution of pedestal parameters in ELMy H-mode in the National Spherical Torus Experiment

Dynamical evolution of pedestal parameters in ELMy H-mode in the National Spherical Torus Experiment

Comparison of small edge-localized modes on MAST and ASDEX Upgrade

Recent progress on spherical torus research

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