[Table of Contents]

Plasma and Fusion Research

Volume 1, 027 (2006)

Rapid Communications

Characteristic Formation of Edge Transport Barrier in the Compact Helical System
Masaki TAKEUCHI1), Kazuo TOI, Kenichi NAGAOKA, Chihiro SUZUKI, Takashi MINAMI, Tsuyoshi AKIYAMA, Yasuo YOSHIMURA, Shin NISHIMURA, Mitsutaka ISOBE, Akihiro SHIMIZU, Chihiro TAKAHASHI, Keisuke MATSUOKA, Shoichi OKAMURA and CHS Group
National Institute for Fusion Science
1)
Department of Energy Engineering and Science, Nagoya University
(Received 12 July 2005 / Accepted 6 April 2006 / Published 16 May 2006)

Abstract

The structure of the Edge Transport Barrier (ETB) was measured by means of a triple Langmuir probe in the Compact Helical System, this diagnostic method achieving high time and spatial resolutions. The radial profiles of electron temperature and electron density show a steep gradient inside the normalized minor radius ρ ˜ 0.96, having a plateau of Te at 0.96 < ρ < 1 and a dip of ne at 0.95 < ρ < 0.98. The radial electric field clearly changed in the H-phase in the region at ρ < 0.96 and 0.99 < ρ < 1, and its shear increased around ρ ˜ 0.97. The characteristic profile evolutions suggest an interaction between ETB formation and a magnetic island related to ι/(2π) = 1. Based on these data, the precise position of the ETB is not determined denitely; that is, it is not established whether it exists inside the magnetic island or closely inside the last closed flux surface (ρ = 1).

Keywords

edge transport barrier, L-H transition, Langmuir probe, radial electric field, magnetic island

DOI: 10.1585/pfr.1.027

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References

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This paper may be cited as follows:

Masaki TAKEUCHI, Kazuo TOI, Kenichi NAGAOKA, Chihiro SUZUKI, Takashi MINAMI, Tsuyoshi AKIYAMA, Yasuo YOSHIMURA, Shin NISHIMURA, Mitsutaka ISOBE, Akihiro SHIMIZU, Chihiro TAKAHASHI, Keisuke MATSUOKA, Shoichi OKAMURA and CHS Group, Plasma Fusion Res. 1, 027 (2006).