Role of low order rational -values in the ITB events in JT-60U reverse shear plasmas

Neudatchin, S. V.*; Takizuka, Tomonori; Hayashi, Nobuhiko; Isayama, Akihiko; Shirai, Hiroshi; Fujita, Takaaki; Kamada, Yutaka; Koide, Yoshihiko; Suzuki, Takahiro

The formation of internal transport barriers (ITBs) near =2,3 surfaces in normal shear (NrS) discharges of JT-60U and JET is known. In reverse shear (RS) JT-60U plasmas, the role of minimum ( $_{min}$ ) equal to 3.5,3,2.5,2 is not obvious for ITB formation. In this paper, the effect of low rational values on ITB-events in JT-60U NrS and RS plasmas is investigated. Under sufficient neutral beam power ( $_{nbi}$ 8MW for 1.2-1.5MA/3.8T pulses), ITB-events are seen at rational and non-rational values of $_{min}$ . The space-time evolutions of $_{e}$ and $_{i}$ are similar, suggesting the same mechanism for $_{e}$ and $_{i}$ transports. The temporal formation of stronger ITB under passing $_{min}$ =3 (after periodical improvements and degradations via ITB-events) in RS H-mode with $_{nbi}$ =8MW is presented. Under smaller power, ITB-events are observed only at rational $_{min}$ values. In a weak RS shot with $_{nbi}$ =4MW, the abrupt rise of $_{e}$ is seen at $_{min}$ =3.5, while more cases of $_{i}$ rise are observed. The difference between the $_{e}$ and $_{i}$ evolutions for the low power suggests the decoupling of $_{e}$ and $_{i}$ transports.

Language	:	English
Journal	:	Nuclear Fusion
Volume	:	44
Number	:	9
Pages	:	p.945 - 953
Publication Year/Month	:	2004/09
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Paper URL	:	https://doi.org/10.1088/0029-5515/44/9/002
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Keywords	:	Tokamak; JT-60U; Reverse Shear; Normal Shear; ITB; ITB-event; q Value; Transport
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InCites™	:	Percentile:51.27 Category:Physics, Fluids & Plasmas
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Registration No. : A20020613
JAEA Abstracts No. : 320951
Paper Submission No. : 21352

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