Disruptions in tokamaks are very often associated with the slowing down of magneto-hydrodynamic (MHD) instabilities and their subsequent locking to the wall. To improve the understanding of the chain of events ending with a disruption, a statistically robust and physically based criterion has been devised to track the slowing down of modes with toroidal mode numbers n = 1 and mostly poloidal mode numberm= 2, providing an alternative and earlier detection tool compared to simple threshold based indicators. A database of 370 discharges of axially symmetric divertor experiment—upgrade (AUG) has been studied and results compared with other indicators used in real time. The estimator is based on a weighted average value of the fast Fourier transform of the perturbed radial n = 1 magnetic field, caused by the rotation of the modes. The use of a carrier sinusoidal wave helps alleviating the spurious influence of non-sinusoidal magnetic perturbations induced by other instabilities like Edge localized modes (ELMs). The indicator constitutes a good candidate for further studies including machine learning approaches for mitigation and avoidance since, by deploying it systematically to evaluate the time instance for the expected locking, multi-machine databases can be populated. Furthermore, it can be thought as a contribution to a wider approach to dynamically tracking the chain of events leading to disruptions.

Peluso, E., Rossi, R., Murari, A., Gaudio, P., Gelfusa, M. (2020). Alternative Detection of n = 1 Modes Slowing Down on ASDEX Upgrade. APPLIED SCIENCES, 10(21), 1-14 [10.3390/app10217891].

Alternative Detection of n = 1 Modes Slowing Down on ASDEX Upgrade

Emmanuele Peluso;Riccardo Rossi;Pasqualino Gaudio;Michela Gelfusa
2020-01-01

Abstract

Disruptions in tokamaks are very often associated with the slowing down of magneto-hydrodynamic (MHD) instabilities and their subsequent locking to the wall. To improve the understanding of the chain of events ending with a disruption, a statistically robust and physically based criterion has been devised to track the slowing down of modes with toroidal mode numbers n = 1 and mostly poloidal mode numberm= 2, providing an alternative and earlier detection tool compared to simple threshold based indicators. A database of 370 discharges of axially symmetric divertor experiment—upgrade (AUG) has been studied and results compared with other indicators used in real time. The estimator is based on a weighted average value of the fast Fourier transform of the perturbed radial n = 1 magnetic field, caused by the rotation of the modes. The use of a carrier sinusoidal wave helps alleviating the spurious influence of non-sinusoidal magnetic perturbations induced by other instabilities like Edge localized modes (ELMs). The indicator constitutes a good candidate for further studies including machine learning approaches for mitigation and avoidance since, by deploying it systematically to evaluate the time instance for the expected locking, multi-machine databases can be populated. Furthermore, it can be thought as a contribution to a wider approach to dynamically tracking the chain of events leading to disruptions.
2020
Pubblicato
Rilevanza internazionale
Articolo
Esperti anonimi
Settore FIS/01 - FISICA SPERIMENTALE
Settore ING-IND/18 - FISICA DEI REATTORI NUCLEARI
English
disruption avoidance; disruptions; MHD instabilities; Mode Locking; Magnetic Islands
Peluso, E., Rossi, R., Murari, A., Gaudio, P., Gelfusa, M. (2020). Alternative Detection of n = 1 Modes Slowing Down on ASDEX Upgrade. APPLIED SCIENCES, 10(21), 1-14 [10.3390/app10217891].
Peluso, E; Rossi, R; Murari, A; Gaudio, P; Gelfusa, M
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2108/314723
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