Prediction and mitigation of disruptions in ASDEX Upgrade

Pautasso, G.; Egorov, S.M.; Tichmann, C.; Fuchs, Julien; Herrmann, A.; Maraschek, M.; Mast, F.; Mertens, V.; Perchermeier, I.; Windsor, C. G.; Zehetbauer, T.

doi:10.1016/s0022-3115(00)00546-8

Cited by 27 publications

(20 citation statements)

References 5 publications

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“…In the last regard, however, there has been significant recent progress in providing tokamak operators with 'online' impending disruption prediction data that can, in principle, be used to either avoid disruption or to soften the consequences of disruptions that do occur e.g. [306]. The subject of techniques for reliable a priori disruption prediction is addressed in section 3.6.…”

Section: Mechanisms For Major Disruptionmentioning

confidence: 99%

Chapter 3: MHD stability, operational limits and disruptions

Hender¹,

Wesley²,

Bialek³

et al. 2007

Nucl. Fusion

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1,013

947

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Progress in the area of MHD stability and disruptions, since the publication of the 1999 ITER Physics Basis document Nucl. Fusion 39 2137-2664, is reviewed. Recent theoretical and experimental research has made important advances in both understanding and control of MHD stability in tokamak plasmas. Sawteeth are anticipated in the ITER baseline ELMy H-mode scenario, but the tools exist to avoid or control them through localized current drive or fast ion generation. Active control of other MHD instabilities will most likely be also required in ITER. Extrapolation from existing experiments indicates that stabilization of neoclassical tearing modes by highly localized feedback-controlled current drive should be possible in ITER. Resistive wall modes are a key issue for S128 Chapter 3: MHD stability, operational limits and disruptions advanced scenarios, but again, existing experiments indicate that these modes can be stabilized by a combination of plasma rotation and direct feedback control with non-axisymmetric coils. Reduction of error fields is a requirement for avoiding non-rotating magnetic island formation and for maintaining plasma rotation to help stabilize resistive wall modes. Recent experiments have shown the feasibility of reducing error fields to an acceptable level by means of non-axisymmetric coils, possibly controlled by feedback. The MHD stability limits associated with advanced scenarios are becoming well understood theoretically, and can be extended by tailoring of the pressure and current density profiles as well as by other techniques mentioned here. There have been significant advances also in the control of disruptions, most notably by injection of massive quantities of gas, leading to reduced halo current fractions and a larger fraction of the total thermal and magnetic energy dissipated by radiation. These advances in disruption control are supported by the development of means to predict impending disruption, most notably using neural networks. In addition to these advances in means to control or ameliorate the consequences of MHD instabilities, there has been significant progress in improving physics understanding and modelling. This progress has been in areas including the mechanisms governing NTM growth and seeding, in understanding the damping controlling RWM stability and in modelling RWM feedback schemes. For disruptions there has been continued progress on the instability mechanisms that underlie various classes of disruption, on the detailed modelling of halo currents and forces and in refining predictions of quench rates and disruption power loads. Overall the studies reviewed in this chapter demonstrate that MHD instabilities can be controlled, avoided or ameliorated to the extent that they should not compromise ITER operation, though they will necessarily impose a range of constraints.

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Section: Mechanisms For Major Disruptionmentioning

confidence: 99%

Chapter 3: MHD stability, operational limits and disruptions

Hender¹,

Wesley²,

Bialek³

et al. 2007

Nucl. Fusion

Self Cite

1,013

947

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“…These pellets are typically composed of moderate-Z or high-Z materials, and the pellet size and velocity are chosen such that the pellet can penetrate deep into the plasma core. Impurity pellet shutdown experiments demonstrating non-disruptive dissipation of the plasma thermal and/or magnetic energies have been performed in JT-60U [175][176][177], ASDEX-Upgrade [178,179], DIII-D [174,180,181], Alcator C-Mod [182], JET [183] and TFTR [184,185]. The efficacy of killer pellet shutdown clearly depends on having sufficient penetration of the pellet into the plasma, such that the resulting impurities are deposited more-or-less uniformly throughout the plasma cross-section.…”

Section: Other Plasma Disturbances Eg Elmsmentioning

confidence: 99%

Plasma-material interactions in current tokamaks and their implications for next step fusion reactors

et al. 2001

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The major increase in discharge duration and plasma energy in a next step DT fusion reactor will give rise to important plasma-material effects that will critically influence its operation, safety and performance. Erosion will increase to a scale of several centimetres from being barely measurable at a micron scale in today's tokamaks. Tritium co-deposited with carbon will strongly affect the operation of machines with carbon plasma facing components. Controlling plasma-wall interactions is critical to achieving high performance in present day tokamaks, and this is likely to continue to be the case in the approach to practical fusion reactors. Recognition of the important consequences of these phenomena stimulated an internationally co-ordinated effort in the field of plasma-surface interactions supporting the Engineering Design Activities of the International Thermonuclear Experimental Reactor project (ITER), and significant progress has been made in better understanding these issues. The paper reviews the underlying physical processes and the existing experimental database of plasma-material interactions both in tokamaks and laboratory simulation facilities for conditions of direct relevance to next step fusion reactors. Two main topical groups of interaction are considered: (i) erosion/redeposition from plasma sputtering and disruptions, including dust and flake generation and (ii) tritium retention and removal. The use of modelling tools to interpret the experimental results and make projections for conditions expected in future devices is explained. Outstanding technical issues and specific recommendations on potential R&D avenues for their resolution are presented.

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“…The characteristics of transient phenomena, such as disruption, vertical displacement events and ELMs will be investigated, and control measures -for example, impurity gas injection for disruption mitigation [35] and pellet injection for ELM mitigation [17] -will be tested. A neural network will be trained [36,37] and tested for disruption prediction. Schemes for impurity transport control will be tested.…”

Section: Operation Plan and Strategy During The Early Operation Phasementioning

confidence: 99%