Type II ELMy H modes on ASDEX Upgrade with good confinement at high density

Stöber, J.; Maraschek, M.; Conway, G. D.; Gruber, O.; Herrmann, A.; Sips, A. C. C.; Treutterer, W.; Zohm, H.

doi:10.1088/0029-5515/41/9/301

Cited by 178 publications

(243 citation statements)

References 17 publications

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“…Pedestal densities as high as 90% of the Greenwald limit, with no confinement degradation, have been achieved in DIII-D [463] and in type-II ELMy discharges in ASDEX Upgrade [469]. This has been exceeded in JET with highly shaped discharges, in which pedestal densities up to n ped /n Green =1 have been reached [470].…”

Section: Fig 427-2 Modelled Diii-d Density Profiles Normalised Tmentioning

confidence: 99%

Chapter 4: Power and particle control

Loarte¹,

et al. 2007

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Abstract.Progress, since the ITER Physics Basis publication, in understanding the processes that will determine the properties of the plasma edge and its interaction with material elements in ITER is described. Experimental areas where significant progress has taken place are : energy transport in the SOL in particular of the anomalous transport scaling, particle transport in the SOL that plays a major role in the interaction of diverted plasmas with the main chamber material elements, ELM energy deposition on material elements and the transport mechanism for the ELM energy from the main plasma to the plasma facing components, the physics of plasma detachment and neutral dynamics including the edge density profile structure and the control of plasma particle content and He removal, the erosion of low and high Z materials in fusion devices, their transport to the core plasma and their migration at the plasma edge including the formation of mixed materials, the processes determining the size and location of the retention of tritium in fusion devices and methods to remove it and the processes determining the efficiency of the various fuelling methods as well as their development towards the ITER requirements. This experimental progress has been accompanied by the development of modelling tools for the physical processes at the edge plasma and plasma-materials interaction and the further validation of these models by comparing their predictions with the new experimental results. Progress in the modelling development and validation has been mostly concentrated in the following areas : refinement of the predictions for ITER with plasma edge modelling codes by inclusion of detailed geometrical features of the divertor and the introduction of physical effects, which can play a 2 major role in determining the divertor parameters at the divertor for ITER conditions such as hydrogen radiation transport and neutral-neutral collisions, modelling of the ion orbits at the plasma edge, which can play a role in determining power deposition at the divertor target, models for plasma-materials and plasma dynamics interaction during ELMs and disruptions, models for the transport of impurities at the plasma edge to describe the core contamination by impurities and the migration of eroded materials at the edge plasma and its associated tritium retention and models for the turbulent processes that determine the anomalous transport of energy and particles across the SOL. The implications for the expected performance of the reference regimes in ITER, the operation of the ITER device and the lifetime of the plasma facing materials are discussed. Introduction.This chapter outlines the significant progress achieved since the ITER Physics Basis in understanding basic scrape-off layer (SOL) and divertor processes in a tokamak. The interaction of plasma with first-wall surfaces will have considerable impact on the performance of fusion plasmas, the lifetime of plasma facing components, and the retention of tritium in next step Burning Plasma E...

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Section: Fig 427-2 Modelled Diii-d Density Profiles Normalised Tmentioning

confidence: 99%

Chapter 4: Power and particle control

Loarte¹,

et al. 2007

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“…The scaling of ELM loss energy is not known, but present data suggests an unfavourable dependence on pedestal collisionality ν * [2]. Techniques to avoid large ELMs are therefore being investigated, for example ELM loss reduction by injection of cryogenic pellets [3], small ELM regimes [4][5][6] and stationary ELM-free regimes [7,8]. It has been observed early on in COMPASS-D that non-axisymmetric error fields can reduce the size of ELMs [9].…”

Section: Introductionmentioning

confidence: 95%

In-vessel saddle coils for MHD control in ASDEX Upgrade

Suttrop

Gruber

Günter

et al. 2009

Fusion Engineering and Design

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A set of 24 in-vessel saddle coils is planned for MHD control experiments in ASDEX Upgrade. These coils can produce static and alternating error fields for suppression of Edge Localised Modes, locked mode rotation control and, together with additional conducting wall elements, resistive wall mode excitation and feedback stabilisation experiments. All of these applications address critical physics issues for the operation of ITER. This extension is implemented in several stages, starting with two poloidally separated rings of eight toroidally distributed saddle coils above and below the outer midplane. In stages 2 and 3, eight midplane coils around the large vessel access ports and 12 AC power converters are added, respectively. Finally (stage 4), the existing passive stabilising loop (PSL), a passive conductor for vertical growth rate reduction, will be complemented by wall elements that allow helical current patterns to reduce the RWM growth rate for active control within the accessible bandwidth. The system is capable of producing error fields with toroidal mode number n = 4 for plasma edge ergodisation with core island width well below the neoclassical tearing mode seed island width even without rotational shielding. Phase variation between the three toroidal coil rings allows to create or avoid resonances with the plasma safety factor profile, in order to test the importance of resonances for ELM suppression.

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“…Because these field errors alter the magnetic topology in the pedestal region, understanding ELM stability and developing a predictive model for the H-mode pedestal will likely require an increased understanding of field errors and the plasma response to them. Finally, these results were obtained in double null discharges optimized for advanced tokamak operations, a regime that is ''close'' to conditions (e.g., high triangularity) for achieving small type II ELMs in other devices [14]. It is not clear if the suppression of large type I ELMs can also be achieved in low triangularity shapes.…”

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Suppression of Large Edge-Localized Modes in High-Confinement DIII-D Plasmas with a Stochastic Magnetic Boundary

et al. 2004

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A stochastic magnetic boundary, produced by an applied edge resonant magnetic perturbation, is used to suppress most large edge-localized modes (ELMs) in high confinement (H-mode) plasmas. The resulting H mode displays rapid, small oscillations with a bursty character modulated by a coherent 130 Hz envelope. The H mode transport barrier and core confinement are unaffected by the stochastic boundary, despite a threefold drop in the toroidal rotation. These results demonstrate that stochastic boundaries are compatible with H modes and may be attractive for ELM control in next-step fusion tokamaks.

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Type II ELMy H modes on ASDEX Upgrade with good confinement at high density

Cited by 178 publications

References 17 publications

Chapter 4: Power and particle control

Chapter 4: Power and particle control

In-vessel saddle coils for MHD control in ASDEX Upgrade

Suppression of Large Edge-Localized Modes in High-Confinement DIII-D Plasmas with a Stochastic Magnetic Boundary

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