Intermittent β collapse after NBCD turn-off in JT-60U fully non-inductive reversed shear discharges

N. Takei, Y. Nakamura, M. Ushigome, T. Suzuki, N. Aiba, M. Takechi, K. Tobita, Y. Takase, A. Fukuyama, S. C. Jardin

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4 Citations (Scopus)


Non-disruptive β collapses with a regular intermittency have been observed after a forced turn-off of neutral beam current drive (NBCD) in JT-60U fully non-inductive, reversed shear (RS) discharges. Self-consistent transport simulations with improved core confinement have first clarified that the redistribution of 'return current' induced after the NBCD turn-off lowers the safety factor of magnetic shear reversal, qmin. Linear MHD stability analysis has also revealed that this lowering of safety factor leads to n ≤ 1 kink-ballooning instability with the modes localized around the internal transport barrier (ITB) of higher qmin (∼6) discharges. It was also pointed out that an increase in the bootstrap current under continuous NB heating can lead to ITB reconstruction and thus causes subsequent β collapses.

Original languageEnglish
Article number011
Pages (from-to)335-345
Number of pages11
JournalPlasma Physics and Controlled Fusion
Issue number3
Publication statusPublished - 2007 Mar 1
Externally publishedYes

ASJC Scopus subject areas

  • Nuclear Energy and Engineering
  • Condensed Matter Physics


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