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  Impurity behaviour in the ASDEX Upgrade divertor tokamak with large area tungsten walls

Neu, R., Dux, R., Geier, A., Kallenbach, A., Pugno, R., Rohde, V., et al. (2002). Impurity behaviour in the ASDEX Upgrade divertor tokamak with large area tungsten walls. Plasma Physics and Controlled Fusion, 44(6), 811-826.

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Item Permalink: http://hdl.handle.net/11858/00-001M-0000-0027-40FB-7 Version Permalink: http://hdl.handle.net/11858/00-001M-0000-0027-40FC-5
Genre: Journal Article

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 Creators:
Neu, R.1, Author              
Dux, R.1, Author              
Geier, A.2, Author              
Kallenbach, A.1, Author              
Pugno, R.3, Author              
Rohde, V.2, Author              
Bolshukhin, D.4, Author
Fuchs, J. C.2, Author              
Gehre, O.2, Author              
Gruber, O.5, Author              
Hobirk, J.2, Author              
Kaufmann, M.2, 6, Author              
Krieger, K.7, Author              
Laux, M.8, 9, Author              
Maggi, C.1, Author              
Murmann, H.3, Author              
Neuhauser, J.3, Author              
Ryter, F.10, Author              
Sips, A. C. C.2, Author              
Stäbler, A.11, Author              
Stober, J.2, Author              Suttrop, W.12, Author              Zohm, H.12, Author              ASDEX Upgrade Team, Author more..
Affiliations:
1Experimental Plasma Physics 4 (E4), Max Planck Institute for Plasma Physics, Max Planck Society, ou_1856293              
2Experimental Plasma Physics 1 (E1), Max Planck Institute for Plasma Physics, Max Planck Society, ou_1856295              
3External Organizations, ou_persistent22              
4Max Planck Society, ou_persistent13              
5Tokamak Theory (TOK), Max Planck Institute for Plasma Physics, Max Planck Society
6Experimental Plasma Physics 3 (E3), Max Planck Institute for Plasma Physics, Max Planck Society, ou_1856291              
7Material Research (MF), Max Planck Institute for Plasma Physics, Max Planck Society, ou_1856328              
8Plasma Diagnostics Group (HUB), Max Planck Institute for Plasma Physics, Max Planck Society, ou_1856324              
9W7-X: Physics (PH), Max Planck Institute for Plasma Physics, Max Planck Society, ou_1856305              
10Tokamak Edge and Divertor Physics (E2), Max Planck Institute for Plasma Physics, Max Planck Society, ou_1856308              
11Technology (TE), Max Planck Institute for Plasma Physics, Max Planck Society, ou_1856318              
12Experimental Plasma Physics 2 (E2), Max Planck Institute for Plasma Physics, Max Planck Society, ou_1856292              

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 Abstract: At the central column of ASDEX Upgrade, an area of 5.5 m(2) of graphite tiles was replaced by tungsten-coated tiles representing about two-thirds of the total area of the central column. No negative influence on the plasma performance was found, except for internal transport barrier limiter discharges. The tungsten influx Gamma(W) stayed below the detection limit only during direct plasma wall contact or for reduced clearance in divertor discharges spectroscopic evidence for Gamma(W) could be found. From these observations a penetration factor of the order of 1% and effective sputtering yields of about 10(-3) could be derived, pointing to a strong contribution by light intrinsic impurities to the total W- sputtering. The tungsten concentrations ranged from below 10(- 6) up to a few times 10(-5). Generally, in discharges with increased density peaking, a tendency for increased central tungsten concentrations or even accumulation was observed. Central heating (mostly) by ECRH led to a strong reduction of the central impurity content, accompanied by a very benign reduction of the energy confinement. The observations suggest that the W-source strength plays only an inferior role for the central W-content compared to the transport, since in the discharges with increased W-concentration neither an increase in the W-influx nor a change in the edge parameters was observed. In contrast, there is strong experimental evidence, that the central impurity concentration can be controlled externally by central heating.

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Language(s): eng - English
 Dates: 2002-06
 Publication Status: Published in print
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: eDoc: 21068
ISI: 000177105000014
 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: 811 - 826 Identifier: ISSN: 0741-3335