Full-orbit and drift calculations of fusion product losses due to explosive fishbones on JET

M. Fitzgerald, J. Buchanan, S.E. Sharapov, V.G. Kiptily, M. Sertoli, G. Szepesi, J. Boom, R.J. Akers, D. King, Leena Aho-Mantila, Markus Airila, Antti Hakola, Aaro Järvinen, Juuso Karhunen, Seppo Koivuranta, Aki Lahtinen, Jari Likonen, Antti Salmi, Paula Sirén, Tuomas TalaJET Contributors

    Research output: Contribution to journalArticleScientificpeer-review

    8 Citations (Scopus)

    Abstract

    Fishbones are ubiquitous in high-performance JET plasmas and are typically considered to be unimportant for scenario design. However, during recent high-performance hybrid scenario experiments, sporadic and explosive fishbone oscillations with sawtooth reconnection were observed coinciding with reduced performance and a main chamber hotspot. Fast ion loss diagnostics showed fusion products ejected from the plasma by the fishbones. We present calculations of the perturbed motion of non-resonant fusion products in the presence of fishbones assuming a fixed linear mode structure and frequency. Using careful reconstruction of the equilibrium and measurements of the perturbation, we show that the measured fishbone spatial structure in these experiments can be well modelled as a linear MHD internal kink mode. Both drift and full-orbit calculations predict losses of fusion products at the same location of the observed hotspot, however the calculated energy content of those losses is negligible and cannot be contributing significantly. The fast ions responsible for the hotspot and the reason for their loss both remain unexplained.
    Original languageEnglish
    Article number016004
    JournalNuclear Fusion
    Volume59
    Issue number1
    DOIs
    Publication statusPublished - 2019
    MoE publication typeA1 Journal article-refereed

    Keywords

    • fast particles
    • fishbone
    • fusion products
    • instability
    • JET
    • losses
    • sawteeth

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