Magnetic perturbation experiments on MAST L- and H-mode plasmas using internal coils

Kirk, A.; Liu, Yueqiang; Nardon, E.; Tamain, P.; Cahyna, P.; Chapman, I. T.; Denner, P.; Meyer, H.; Mordijck, S.; Temple, D.

doi:10.1088/0741-3335/53/6/065011

Cited by 105 publications

(147 citation statements)

References 23 publications

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“…Both NSTX and MAST saw an increase in the Hmode power threshold with application of RMPs. 214,215,218 This observation is similar to those from tokamaks and is somewhat expected since RMPs tend to degrade edge confinement (or change edge rotational shear.) There are some differences between MAST and NSTX, where in MAST, there is no obvious correlation with E r shear profiles, 214 but in NSTX, some dependence on the E r shear was observed.…”

Section: B H-modes Transition and Power Thresholdsupporting

confidence: 71%

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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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Section: B H-modes Transition and Power Thresholdsupporting

confidence: 71%

“…198,[207][208][209][210][211][212][213][214][215][216][217][218][219][220][221][222][223] Recently, the H-mode was also observed in PEGASUS ohmic plasmas. 224 Overall, an Hmode in STs looks and behaves qualitatively similar to that in tokamaks.…”

Section: B H-modes Transition and Power Thresholdmentioning

confidence: 99%

Recent progress on spherical torus research

Ono

Kaita

2015

Physics of Plasmas

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“…The 3D-corrugation of the electron density and temperature profiles are observed: the deformation of the temperature near the separatrix is given in Fig.58. Last, it is observed in the experiments that the radial electric field is made more positive by RMP application ( [43]). This phenomenon was found in simulations in the cylindrical case ( [12]) and is also found in our toroidal simulations with JOREK, as plotted in Fig.59 in the LFS.…”

Section: Ergodization and 3d-effectsmentioning

confidence: 97%

Non-linear magnetohydrodynamic modeling of plasma response to resonant magnetic perturbations

et al. 2013

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The interaction of static Resonant Magnetic Perturbations (RMPs) with the plasma flows is modeled in toroidal geometry, using the non-linear resistive MHD code JOREK, which includes the X-point and the Scrape-Off-Layer. Two-fluid diamagnetic effects, the neoclassical poloidal friction and a source of toroidal rotation are introduced in the model to describe realistic plasma flows. RMP penetration is studied taking self-consistently into account the effects of these flows and the radial electric field evolution. JET-like, MAST and ITER parameters are used in modeling. For JET-like parameters, three regimes of plasma response are found depending on the plasma resistivity and the diamagnetic rotation: at high resistivity and slow rotation, the islands generated by the RMPs at the edge resonant surfaces rotate in the ion diamagnetic direction and their size oscillates. At faster rotation, the generated islands are static and are more screened by the plasma. An intermediate regime with static islands which slightly oscillate is found at lower resistivity. In ITER simulations, the RMPs generate static islands, which forms an ergodic layer at the very edge (ψ ≥ 0.96) characterized by lobe structures near the X-point and results in a small strike point splitting on the divertor targets. In MAST DND geometry, lobes are also found near the X-point and the 3D-deformation of the density and temperature profiles is observed.

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“…This indeed enables H-modes with very small or even completely suppressed ELMs to be run, [51,52,53,17,54]. Since 2011 ASDEX Upgrade is equipped with such saddle coils, named B-coils, which can produce perturbations with n ≤ 4, where n is the toroidal mode number.…”

Section: L-h Transition In the Presence Of Magnetic Perturbationsmentioning

confidence: 99%

“…Results have been obtained in MAST [17], DIII-D [6], NSTX [18], using an n=3 setting for the MPs. These results all indicate an increase of P L−H with the amplitude of the applied perturbation, which can be as high as two times above the P L−H value without MPs.…”

Section: L-h Transition In the Presence Of Magnetic Perturbationsmentioning

confidence: 99%

Survey of the H-mode power threshold and transition physics studies in ASDEX Upgrade

et al. 2013

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Abstract. An overview of the H-mode threshold power in ASDEX Upgrade which addresses the impact of the tungsten versus graphite wall, the dependences upon plasma current and density, as well as the influence of the plasma ion mass is given. Results on the H-L back transition are also presented. Dedicated L-H transition studies with electron heating at low density, which enable a complete separation of the electron and ion channels, reveal that the ion heat flux is a key parameter in the L-H transition physics mechanism through the main ion pressure gradient which is itself the main contribution to the radial electric field and the induced flow shearing at the edge. The electron channel does not play any role. The 3D magnetic field perturbations used to mitigate the ELMs are found to also influence the L-H transition and to increase the power threshold. This effect is caused by a flattening of the edge pressure gradient in the presence of the 3D fields such that the L-H transitions with and without perturbations occur at the same value of the radial electric field well, but at different heating powers.

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Magnetic perturbation experiments on MAST L- and H-mode plasmas using internal coils

Cited by 105 publications

References 23 publications

Recent progress on spherical torus research

Recent progress on spherical torus research

Non-linear magnetohydrodynamic modeling of plasma response to resonant magnetic perturbations

Survey of the H-mode power threshold and transition physics studies in ASDEX Upgrade

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