Physics of slow L-H transitions in the DIII-D tokamak

Details of the low-high (L-H) confinement transition are studied by a new technique which allows for an arbitrarily slow transition between the L- and H-modes on DIII-D. During the transition, the plasma is in an intermediate state (IM-mode) of temperature, density, confinement and edge shear flow....

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Bibliographic Details
Published in:Nuclear fusion 2002-09, Vol.42 (9), p.1134-1143, Article 312
Main Authors: Colchin, R.J, Carreras, B.A, Maingi, R, Baylor, L.R, Jernigan, T.C, Schaffer, M.J, Carlstrom, T.N, Brooks, N.H, Greenfield, C.M, Gohil, P, McKee, G.R, Rudakov, D.L, Rhodes, T.L, Doyle, E.J, Austin, M.E, Watkins, J.G
Format: Article
Language:English
Subjects:
Electric fields
Exact sciences and technology
Magnetic confinement and equilibrium
Neutrals in plasma
Physics
Physics of gases, plasmas and electric discharges
Physics of plasmas and electric discharges
Plasma confinement
Plasma density
Plasma properties
Plasma stability
Plasma turbulence
Relaxation oscillators
Shear flow
Temperature
Tokamaks
Waves, oscillations, and instabilities in plasmas and intense beams
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Summary:Details of the low-high (L-H) confinement transition are studied by a new technique which allows for an arbitrarily slow transition between the L- and H-modes on DIII-D. During the transition, the plasma is in an intermediate state (IM-mode) of temperature, density, confinement and edge shear flow. The IM-mode is characterized by periodic bursts of an edge instability, governed by relaxation oscillations, which evolve into type III edge localized modes (ELMs) as the neutral beam heating power is raised. An ELM-free H-mode is achieved when the edge pressure gradient is large enough to support shear flow sufficient to quell the IM-mode edge instability.
ISSN:0029-5515
1741-4326
DOI:10.1088/0029-5515/42/9/312