30E03P
JT-60Uの逆方向トロイダル回転とセパラトリクスパワーによるType-I ELM特性に対する統合的効果
Unified effects of counter toroidal rotation and power across the separatrix
on type-I ELMs in JT-60U
浦野創，大山直幸，神谷健作，相羽信行，鎌田裕，藤田隆明，JT-60チーム
URANO Hajime, OYAMA, Naoyuki, KAMIYA Kensaku, AIBA Nobuyuki, KAMADA Yutaka,Fujita Takaaki, JT-60 Team
日本原子力研究開発機構 那珂核融合研究所
Japan Atomic Energy Agency, Naka Fusion InstituteType-I ELMs are spontaneous periodic relaxationsof the pressure gradient at the pedestal of H-mode
plasmas, occurring in a repetitive manner once theedge pressure gradient and current density exceed
the stability boundary. In present understanding on
type-I ELMs, the peeling-ballooning instability
driven by both edge pressure gradient and current
density has described the experimentally observed
limit of edge pressure profiles in tokamaks. In
recent ELM studies, it has been prevalently
recognized that the edge toroidal rotation plays asignificant role in determining the ELM feature.
The effects of toroidal rotation on the stability
boundary of edge MHD modes have also been
detected in recent theoretical studies.
One of the most general features in type-I
ELMs is the proportionality between ELM
frequency fELM and the power crossing theseparatrix Psep, which is also utilized in many cases
for validation of ELM type. The ELM
characteristics are strongly influenced by the edge
pedestal structure just before an ELM crash occurs.
Therefore, in case the toroidal momentum source isinput by NBs in ELMy H-mode plasmas whether
those are tangential NBs or perpendicular NBs, thecomposition of ELM characteristics becomessuddenly complex. This is because the edge
pedestal structure itself could be modified directly
or indirectly when the toroidal rotation and heating
power are changed. An increase of βp due to theapplication of increased heating power could
improve the stability of the plasma edge in the low
magnetic field side. At the same time, this also
causes the increase of ELM frequency because ofincreased heat flux across the separatrix. Besides,
the stability boundary is modified by the edge
toroidal rotation.
In this study, the influence of toroidal rotationand heating power is examined using the variety ofNB injections in JT-60U. ELM frequency fELM
during the type-I ELMy H-mode phase increased

Fig. 1. Dependence of fELM on Psep for two cases of fixed
VTped in type-I ELMy H-mode plasmas.

monotonically together with Psep for all the cases oftangential NBs. In addition, fELM became higher incase of counter-tangential NB at a given Psep.
However, dependence of fELM on Psep for each caseof tangential NB was explicitly stronger than aproportional relation when the perpendicular NBs
were injected. The toroidal rotation velocity at theH-mode pedestal VTped shifted continuously incounter-direction when Psep was increased by theperpendicular NBs. Fig. 1 shows the dependence offELM on Psep for two cases of fixed VTped. At fixedvalues of VTped, fELM increased clearly in proportion
to Psep. In addition, this proportionality between
fELM and Psep holds regardless of the mixture ofdataset with the toroidal momentum inputs [1]. The
proportional coefficient decreased as VTped shifted inco-direction. The ELM frequency observed in theH-mode experiments with power scan becomes
higher than the value expected in proportion to Psep
when VTped shifts toward counter. This is explained
as a result of the unified effect of VTped and Psep on
ELM activity.
[1] H. Urano, et al., Nucl. Fusion 52 (2012) 103012.