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  4. Plasma wall interaction and its implication in an all tungsten divertor tokamak
 
conference paper

Plasma wall interaction and its implication in an all tungsten divertor tokamak

Neu, R.
•
Balden, M.
•
Bobkov, V.
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2007
Plasma Physics And Controlled Fusion
34th European-Physical-Society Conference on Plasma Physics

ASDEX Upgrade has recently finished its transition towards an all-W divertor tokamak, by the exchange of the last remaining graphite tiles to W-coated ones. The plasma start-up was performed without prior boronization. It was found that the large He content in the plasma, resulting from DC glow discharges for conditioning, leads to a confinement reduction. After the change to D glow for inter-shot conditioning, the He content quickly dropped and, in parallel, the usual H-Mode confinement with H factors close to one was achieved. After the initial conditioning phase, oxygen concentrations similar to that in previous campaigns with boronizations could be achieved. Despite the removal of all macroscopic carbon sources, no strong change in C influxes and C content could be observed so far. The W concentrations are similar to the ones measured previously in discharges with old boronization and only partial coverage of the surfaces with W. Concomitantly it is found that although the W erosion flux in the divertor is larger than the W sources in the main chamber in most of the scenarios, it plays only a minor role for the W content in the main plasma. For large antenna distances and strong gas puffing, ICRH power coupling could be optimized to reduce the W influxes. This allowed a similar increase of stored energy as yielded with comparable beam power. However, a strong increase of radiated power and a loss of H-Mode was observed for conditions with high temperature edge plasma close to the antennas. The use of ECRH allowed keeping the central peaking of the W concentration low and even phases of improved H-modes have already been achieved.

  • Details
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Type
conference paper
DOI
10.1088/0741-3335/49/12B/S04
Web of Science ID

WOS:000252745900006

Author(s)
Neu, R.
Balden, M.
Bobkov, V.
Dux, R.
Gruber, O.
Herrmann, A.
Kallenbach, A.
Kaufmann, M.
Maggi, C. F.
Maier, H.
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Date Issued

2007

Published in
Plasma Physics And Controlled Fusion
Volume

49

Start page

B59

End page

B70

Subjects

Asdex Upgrade Divertor

•

Iter-Like Wall

•

Alcator C-Mod

•

Facing Components

•

Operation

•

Transport

•

Erosion

Editorial or Peer reviewed

NON-REVIEWED

Written at

EPFL

EPFL units
CRPP  
SPC  
Event nameEvent placeEvent date
34th European-Physical-Society Conference on Plasma Physics

Warsaw, POLAND

Jul 02-06, 2007

Available on Infoscience
July 4, 2012
Use this identifier to reference this record
https://infoscience.epfl.ch/handle/20.500.14299/83373
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