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Low-to-high confinement transition simulations in divertor geometry
Recent results are presented for turbulence in tokamak boundary plasmas and its relationship to the low-to-high confinement (L–H) transition in a realistic divertor geometry. These results are obtained from a three-dimensional (3D) nonlocal electromagnetic turbulence code, which models the boundary...
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Published in: | Physics of Plasmas 2000-05, Vol.7 (5), p.1951-1958 |
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Main Authors: | , , , |
Format: | Article |
Language: | English |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | Recent results are presented for turbulence in tokamak boundary plasmas and its relationship to the low-to-high confinement (L–H) transition in a realistic divertor geometry. These results are obtained from a three-dimensional (3D) nonlocal electromagnetic turbulence code, which models the boundary plasma using fluid equations for plasma vorticity, density, electron and ion temperatures and parallel momenta. With sources added in the core-edge region and sinks in the scrape-off layer (SOL), the code follows the self-consistent profile evolution together with turbulence. Under DIII-D [Luxon et al., International Conference on Plasma Physics and Controlled Nuclear Fusion (International Atomic Energy Agency, Vienna, 1986), p. 159] tokamak L-mode conditions, the dominant source of turbulence is pressure-gradient-driven resistive X-point modes. These modes are electromagnetic and curvature-driven at the outside mid-plane region but become electrostatic near X-points due to magnetic shear and collisionality. Classical resistive ballooning modes at high toroidal mode number,
n,
coexist with these modes but are sub-dominant. Results indicate that, as the power is increased, these modes are stabilized by increased turbulence-generated velocity shear, resulting in an abrupt suppression of high-
n
turbulence and the formation of a pedestal in density and temperature, as is characteristic of the H-mode transition. The sensitivity of the boundary turbulence to the direction of the toroidal field
B
t
is discussed. |
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ISSN: | 1070-664X 1089-7674 |
DOI: | 10.1063/1.874044 |