Path-oriented early reaction to approaching disruptions in ASDEX Upgrade and TCV in view of the future needs for ITER and DEMO

M. Maraschek, A. Gude, V. Igochine, H. Zohm, E. Alessi, M. Bernert, C. Cianfarani, S. Coda, B. Duval, B. Esposito, S. Fietz, M. Fontana, C. Galperti, L. Giannone, T. Goodman, G. Granucci, L. Marelli, S. Novak, R. Paccagnella, G. PautassoP. Piovesan, L. Porte, S. Potzel, C. Rapson, M. Reich, O. Sauter, U. Sheikh, C. Sozzi, G. Spizzo, J. Stober, W. Treutterer

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Abstract

Routine reaction to approaching disruptions in tokamaks is currently largely limited to machine protection by mitigating an ongoing disruption, which remains a basic requirement for ITER and DEMO [1]. Nevertheless, a mitigated disruption still generates stress to the device. Additionally, in future fusion devices, high-performance discharge time itself will be very valuable. Instead of reacting only on generic features, occurring shortly before the disruption, the ultimate goal is to actively avoid approaching disruptions at an early stage, sustain the discharges whenever possible and restrict mitigated disruptions to major failures. Knowledge of the most relevant root causes and the corresponding chain of events leading to disruption, the disruption path, is a prerequisite. For each disruption path, physics-based sensors and adequate actuators must be defined and their limitations considered. Early reaction facilitates the efficiency of the actuators and enhances the probability of a full recovery. Thus, sensors that detect potential disruptions in time are to be identified. Once the entrance into a disruption path is detected, we propose a hierarchy of actions consisting of (I) recovery of the discharge to full performance or at least continuation with a less disruption-prone backup scenario, (II) complete avoidance of disruption to sustain the discharge or at least delay it for a controlled termination and, (III), only as last resort, a disruption mitigation. Based on the understanding of disruption paths, a hierarchical and path-specific handling strategy must be developed. Such schemes, testable in present devices, could serve as guidelines for ITER and DEMO operation. For some disruption paths, experiments have been performed at ASDEX Upgrade and TCV. Disruptions were provoked in TCV by impurity injection into ELMy H-mode discharges and in ASDEX Upgrade by forcing a density limit in H-mode discharges. The new approach proposed in this paper is discussed for these cases. For the H-mode density limit sensors used so far react too late. Thus a plasma-state boundary is proposed, that can serve as an adequate early sensor for avoiding density limit disruptions in H-modes and for recovery to full performance.
Original languageEnglish
Article number014047
Pages (from-to)-
JournalPlasma Physics and Controlled Fusion
Volume60
Issue number1
DOIs
Publication statusPublished - 1 Jan 2018
Externally publishedYes

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All Science Journal Classification (ASJC) codes

  • Nuclear Energy and Engineering
  • Condensed Matter Physics

Cite this

Maraschek, M., Gude, A., Igochine, V., Zohm, H., Alessi, E., Bernert, M., Cianfarani, C., Coda, S., Duval, B., Esposito, B., Fietz, S., Fontana, M., Galperti, C., Giannone, L., Goodman, T., Granucci, G., Marelli, L., Novak, S., Paccagnella, R., ... Treutterer, W. (2018). Path-oriented early reaction to approaching disruptions in ASDEX Upgrade and TCV in view of the future needs for ITER and DEMO. Plasma Physics and Controlled Fusion, 60(1), -. [014047]. https://doi.org/10.1088/1361-6587/aa8d05