The JET Alfvén Eigenmode Local Manager for the real-time detection and tracking of MHD instabilities

¹ JET-EFDA, Culham Science Centre - OX14 3DB, Abingdon, UK, EU
² Ecole Polytechnique Fédérale de Lausanne, Centre de Recherches en Physique des Plasmas, Association EURATOM-Confédération Suisse - CH-1015 Lausanne, Switzerland
³ Laboratoire d'Astrophysique de Toulouse-Tarbes, Université de Toulouse, CNRS - Toulouse, France, EU
⁴ Culham Centre for Fusion Energy, Culham Science Centre - Abingdon, UK, EU
⁵ JET-EFDA Close Support Unit, Culham Science Centre - Abingdon, UK, EU
⁶ Plasma Science and Fusion Centre,  Massachusetts Institute of Technology - Boston, MA, USA (c)

^a duccio.testa@epfl.ch

Received: 4 June 2010
Accepted: 12 November 2010

Abstract

In this work we report the successful application of an innovative method, based on the Sparse Representation of signals, to perform a real-time, unsupervised detection of the individual components in a frequency degenerate, multi-harmonic spectrum, using a small number of data unevenly sampled in the spatial domain. This method has been developed from its original applications in astronomy, and is now routinely used in the JET thermonuclear fusion experiment to obtain the decomposition of a spectrum of high-frequency (∼10–500 kHz range) magnetic instabilities with a sub-ms time resolution, allowing the real-time tracking of its individual components as the plasma background evolves. This work opens a path towards developing real-time control tools for electro-magnetic instabilities in future fusion devices aimed at achieving a net energy gain. More generally, the speed and accuracy of this algorithm is recommended for instances of physics measurements and control engineering where an unsupervised, real-time decomposition of a degenerate signal is required from a small number of data.