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  ELM frequency control by continuous small pellet injection in ASDEX Upgrade

Lang, P. T., Neuhauser, J., Horton, L. D., Eich, T., Fattorini, L., Fuchs, J. C., et al. (2003). ELM frequency control by continuous small pellet injection in ASDEX Upgrade. Nuclear Fusion, 43(10), 1110-1120. doi:10.1088/0029-5515/43/10/012.

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Lang, P. T.1, Author           
Neuhauser, J.2, Author           
Horton, L. D.1, Author           
Eich, T.1, Author           
Fattorini, L.3, Author
Fuchs, J. C.1, Author           
Gehre, O.1, Author           
Herrmann, A.1, Author           
Ignacz, P.3, Author
Jakobi, M.4, Author           
Kalvin, S.3, Author
Kaufmann, M.1, 5, Author           
Kocsis, G.3, Author
Kurzan, B.4, Author           
Maggi, C.6, Author           
Manso, M. E.3, Author
Maraschek, M.4, Author           
Mertens, V.1, Author           
Mück, A.2, Author           
Murmann, H. D.2, Author           
Neu, R.6, Author           Nunes, I.3, AuthorReich, D.3, AuthorReich, M.1, Author           Saarelma, S.3, AuthorSandmann, W.1, Author           Stober, J.1, Author           Vogl, U.3, AuthorASDEX Upgrade Team, Author   more..
1Experimental Plasma Physics 1 (E1), Max Planck Institute for Plasma Physics, Max Planck Society, ou_1856295              
2External Organizations, ou_persistent22              
3Centro de Fusão Nuclear, Associacão EURATOM/IST, Instituto Superior Técnico, 1049-001 Lisboa, Portugal; KFKI-RMKI, PO Box 49, H-1525 Budapest, Hungary; FH Amberg-Weiden, Abt. Amberg, Kaiser-Wilhelm-Ring 23, 92224 Amberg, Germany; Helsinki University of Technology, Euratom-TEKES Association, PO Box 2200, FIN-02015 HUT, Finland, ou_persistent22              
4Experimental Plasma Physics 2 (E2), Max Planck Institute for Plasma Physics, Max Planck Society, ou_1856292              
5Experimental Plasma Physics 3 (E3), Max Planck Institute for Plasma Physics, Max Planck Society, ou_1856291              
6Experimental Plasma Physics 4 (E4), Max Planck Institute for Plasma Physics, Max Planck Society, ou_1856293              


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 Abstract: Injection of cryogenic deuterium pellets has been successfully applied in ASDEX Upgrade for external edge localized mode (ELM) frequency control in type-I ELMy H-mode discharge scenarios. A pellet velocity of 560 m s⁻¹ and a size of about 6 × 10¹⁹ D-atoms was selected for technical reasons, although even lower masses were found sufficient to trigger ELMs. A moderate repetition rate close to 20 Hz was chosen to avoid over-fuelling of the core plasma. Pellet sequences of up to 4 s duration were injected into discharges close to the L–H threshold, intrinsically developing large compound ELMs at a rate of 3 Hz. With pellet injection, these large ELMs were completely replaced by smaller type-I ELMs at the much higher pellet frequency, accompanied by a slight increase of density and even of stored energy. This external ELM control could be repeatedly switched on and off by just interrupting the pellet train. ELMs were triggered in less than 200 µs after pellet arrival at the plasma edge, at which time only a fraction of the pellet has been ablated, forming a rather localized, three-dimensional plasmoid, which drives the edge unstable well before the deposited mass is spread toroidally. The pellet controlled case has also been compared with a discharge at a somewhat lower density, but with otherwise rather similar data, developing spontaneous 20 Hz type-I ELMs. Despite the different trigger mechanisms, the general ELM features turn out to be qualitatively similar, possibly because of the similarity of the two cases in terms of ELM relevant parameters. The scaling with background plasma, heating power, pellet launch parameters, etc over a larger range still remains to be investigated.


Language(s): eng - English
 Dates: 2003
 Publication Status: Published in print
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
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Title: Nuclear Fusion
  Alternative Title : Nucl. Fusion
Source Genre: Journal
Publ. Info: Copyright © Institute of Physics and IOP Publishing Limited 2003
Pages: - Volume / Issue: 43 (10) Sequence Number: - Start / End Page: 1110 - 1120 Identifier: -