Observation of H-Mode Operation Windows for ECH Plasmas in Heliotron J

Journal Article · Wed Sep 15 04:00:00 EDT 2004 · Fusion Science and Technology

OSTI ID:20849746

Sano, F ^[1]; Mizuuchi, T ^[1]; Nagasaki, K ^[1]

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1. Kyoto University (Japan)

The H-mode transition properties of 70-GHz, 0.4-MW electron cyclotron heating (ECH) plasmas in Heliotron J have been studied with special reference to their magnetic configuration dependences, such as the edge iota dependences. Two edge iota windows for the H-mode transition were observed to be (a) 0.54 < {iota}(a)/2{pi} < 0.56 in separatrix discharge plasmas and (b) 0.62 < {iota}>(a)/2{pi} < 0.63 in partial wall-limiter discharge plasmas if a certain threshold line-averaged electron density (n{sub e} = 1.2-1.6 x 10{sup 19} m{sup -3}) is achieved, where {iota}(a) is the vacuum edge iota value and a is the plasma minor radius, respectively. A strong dependence of the quality of the H-mode on the edge topology conditions was revealed. The energy confinement time for the separatrix discharge plasmas was found to be enhanced beyond the normal ISS95 scaling in the transient H-mode phase, being 50% longer than that in the 'before transition' phase. The window characteristics are discussed on the basis of the calculated geometrical poloidal viscous damping rate coefficient in a collisional plasma, indicating that the behavior of the viscous damping rate coefficient alone could not explain the observed characteristics. The bootstrap current properties of ECH plasmas and the relevant electron cyclotron current drive experimental results are also discussed.

• OSTI ID: 20849746
• Journal Information: Fusion Science and Technology, Journal Name: Fusion Science and Technology Journal Issue: 2 Vol. 46; ISSN 1536-1055
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
BOOTSTRAP CURRENT
COLLISIONAL PLASMA
CONFINEMENT TIME
DAMPING
ECR CURRENT DRIVE
ECR HEATING
ELECTRON DENSITY
GHZ RANGE
H-MODE PLASMA CONFINEMENT
HELIOTRON
LIMITERS
OPERATION
PHASE TRANSFORMATIONS
SPACE DEPENDENCE
TOPOLOGY
TRANSIENTS