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

doi:10.1088/0741-3335/49/3/011

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

PPPL Theory

Princeton University

Research output: Contribution to journal › Article › peer-review

Abstract

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, q_min. 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 q_min (∼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 language	English (US)
Article number	011
Pages (from-to)	335-345
Number of pages	11
Journal	Plasma Physics and Controlled Fusion
Volume	49
Issue number	3
DOIs	https://doi.org/10.1088/0741-3335/49/3/011
State	Published - Mar 1 2007

ASJC Scopus subject areas

Nuclear Energy and Engineering
Condensed Matter Physics

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10.1088/0741-3335/49/3/011

Cite this

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

abstract = "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.",

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T1 - Intermittent β collapse after NBCD turn-off in JT-60U fully non-inductive reversed shear discharges

AU - Takei, N.

AU - Nakamura, Y.

AU - Ushigome, M.

AU - Suzuki, T.

AU - Aiba, N.

AU - Takechi, M.

AU - Tobita, K.

AU - Takase, Y.

AU - Fukuyama, A.

AU - Jardin, S. C.

PY - 2007/3/1

Y1 - 2007/3/1

N2 - 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.

AB - 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.

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DO - 10.1088/0741-3335/49/3/011

M3 - Article

SN - 0741-3335

VL - 49

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JO - Plasma Physics and Controlled Fusion

JF - Plasma Physics and Controlled Fusion

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

Abstract

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