TY - JOUR
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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U2 - 10.1088/0741-3335/49/3/011
DO - 10.1088/0741-3335/49/3/011
M3 - Article
AN - SCOPUS:34247247250
SN - 0741-3335
VL - 49
SP - 335
EP - 345
JO - Plasma Physics and Controlled Fusion
JF - Plasma Physics and Controlled Fusion
IS - 3
M1 - 011
ER -