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  Transport into and across the scrape-off layer in the ASDEX Upgrade divertor tokamak

Neuhauser, J., Coster, D., Fahrbach, H. U., Fuchs, J. C., Haas, G., Herrmann, A., et al. (2002). Transport into and across the scrape-off layer in the ASDEX Upgrade divertor tokamak. Plasma Physics and Controlled Fusion, 44(6), 855-869.

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Item Permalink: http://hdl.handle.net/11858/00-001M-0000-0027-4298-6 Version Permalink: http://hdl.handle.net/11858/00-001M-0000-0027-4299-4
Genre: Journal Article

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 Creators:
Neuhauser, J.1, Author              
Coster, D.2, Author              
Fahrbach, H. U.3, Author              
Fuchs, J. C.3, Author              
Haas, G.3, 4, Author              
Herrmann, A.3, Author              
Horton, L. D.3, Author              
Jakobi, M.5, Author              
Kallenbach, A.6, Author              
Laux, M.7, 8, Author              
Kim, J. W.9, Author              
Kurzan, B.5, Author              
Müller, H. W.3, Author              
Murmann, H.1, Author              
Neu, R.6, Author              
Rohde, V.3, Author              
Sandmann, W.3, Author              
Suttrop, W.5, Author              
Wolfrum, E.3, Author              
ASDEX Upgrade Team, Author  
Affiliations:
1External Organizations, ou_persistent22              
2Tokamak Theory (TOK), Max Planck Institute for Plasma Physics, Max Planck Society, ou_1856309              
3Experimental Plasma Physics 1 (E1), Max Planck Institute for Plasma Physics, Max Planck Society, ou_1856295              
4Technology (TE), Max Planck Institute for Plasma Physics, Max Planck Society, ou_1856318              
5Experimental Plasma Physics 2 (E2), Max Planck Institute for Plasma Physics, Max Planck Society, ou_1856292              
6Experimental Plasma Physics 4 (E4), Max Planck Institute for Plasma Physics, Max Planck Society, ou_1856293              
7Plasma Diagnostics Group (HUB), Max Planck Institute for Plasma Physics, Max Planck Society, ou_1856324              
8W7-X: Physics (PH), Max Planck Institute for Plasma Physics, Max Planck Society, ou_1856305              
9Tokamak Theory (TOK), Max Planck Institute for Plasma Physics, Max Planck Society

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 Abstract: The elements of transport into and across the scrape-off layer in the poloidal divertor tokamak ASDEX Upgrade are analysed for different operational regimes with emphasis on enhanced confinement regimes with an edge barrier. Utilizing the existing set of edge diagnostics, especially the high- resolution multi-pulse edge Thomson scattering system, in combination with long discharge plateaus, radial sweeps and advanced averaging techniques, detailed radial mid-plane profiles of diverted plasmas are obtained. Profiles are smooth across the separatrix, indicating strong radial correlation, and there is no remarkable variation across the second separatrix either. Together with measured input, recycling, pumping and bypass fluxes, a corrected separatrix position is determined and transport characteristics are derived in the different radial zones generally identified in the profile structure. Transport in the steep gradient region inside and across the separatrix shows typical ballooning-type critical electron pressure gradient scaling and, in parallel, even a clear correlation between radial electron density and temperature decay lengths (e.g. eta(e) = d(ln T)/d(ln n) similar to 2 for type-I ELMy H-modes). These findings indicate the importance of stiff profiles in this region, while diffusion coefficients are secondary parameters, determined essentially by the source distribution. The outer scrape-off layer wing exhibits a more filamentary structure with preferential outward drift especially in high-performance discharges, with formal diffusion coefficients far above the Bohm value in agreement with results on the old ASDEX experiment. A basic mechanism involved there seems to be partial loss of equilibrium and fast curvature-driven outward acceleration, in principle well known from theory, investigated decades ago in pinch experiments and utilized recently in high- field-side pellet fuelling.

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Language(s): eng - English
 Dates: 2002
 Publication Status: Published in print
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Method: Peer
 Identifiers: eDoc: 21071
ISI: 000177105000017
 Degree: -

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Title: Plasma Physics and Controlled Fusion
  Alternative Title : Plasma Phys. Control. Fusion
Source Genre: Journal
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Publ. Info: -
Pages: - Volume / Issue: 44 (6) Sequence Number: - Start / End Page: 855 - 869 Identifier: ISSN: 0741-3335