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arXiv · 1310.0287

Time-Resonant Tokamak Plasma Edge Instabilities?

A. J. Webster·R. O. Dendy·F. A. Calderon·S. C. Chapman·E. Delabie·D. Dodt·R. Felton·T. N. Todd·F. Maviglia·J. Morris·V. Riccardo·B. Alper·S Brezinsek·P. Coad·J. Likonen·M. Rubel·JET EFDA Contributors
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Abstract

For a two week period during the Joint European Torus (JET) 2012 experimental campaign, the same high confinement plasma was repeated 151 times. The dataset was analysed to produce a probability density function (pdf) for the waiting times between edge-localised plasma instabilities ("ELMS"). The result was entirely unexpected. Instead of a smooth single peaked pdf, a succession of 4-5 sharp maxima and minima uniformly separated by 7-8 millisecond intervals was found. Here we explore the causes of this newly observed phenomenon, and conclude that it is either due to a self-organised plasma phenomenon or an interaction between the plasma and a real-time control system. If the maxima are a result of "resonant" frequencies at which ELMs can be triggered more easily, then future ELM control techniques can, and probably will, use them. Either way, these results demand a deeper understanding of the ELMing process.

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A. J. Webster, R. O. Dendy, F. A. Calderon, S. C. Chapman, E. Delabie, D. Dodt, R. Felton, T. N. Todd, F. Maviglia, J. Morris, V. Riccardo, B. Alper, S Brezinsek, P. Coad, J. Likonen, M. Rubel, JET EFDA Contributors. 2013-10-01. Time-Resonant Tokamak Plasma Edge Instabilities?. https://doi.org/10.1088/0741-3335%2F56%2F7%2F075017

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