ELM frequency control by continuous small pellet injection in ASDEX upgrade

P. T. Lang, J. Neuhauser, L. D. Horton, T. Eich, L. Fattorini, J. C. Fuchs, O. Gehre, A. Herrmann, P. Ignacz, M. Jakobi, S. Kálvin, M. Kaufmann, G. Kocsis, B. Kurzan, C. Maggi, M. E. Manso, M. Maraschek, V. Mertens, A. Mück, H. D. MurmannR. Neu, I. Nunes, D. Reich, M. Reich, S. Saarelma, W. Sandmann, J. Stober, U. Vogl

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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.

Original languageEnglish
Pages (from-to)1110-1120
Number of pages11
JournalNuclear Fusion
Volume43
Issue number10
DOIs
Publication statusPublished - Oct 2003

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frequency control
pellets
injection
actuators
plasma heating
refueling
cryogenics
arrivals
deuterium
repetition

ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Condensed Matter Physics
  • Nuclear and High Energy Physics

Cite this

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

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.; Gehre, O.; Herrmann, A.; Ignacz, P.; Jakobi, M.; Kálvin, S.; Kaufmann, M.; Kocsis, G.; Kurzan, B.; Maggi, C.; Manso, M. E.; Maraschek, M.; Mertens, V.; Mück, A.; Murmann, H. D.; Neu, R.; Nunes, I.; Reich, D.; Reich, M.; Saarelma, S.; Sandmann, W.; Stober, J.; Vogl, U.

In: Nuclear Fusion, Vol. 43, No. 10, 10.2003, p. 1110-1120.

Research output: Contribution to journalArticle

Lang, PT, Neuhauser, J, Horton, LD, Eich, T, Fattorini, L, Fuchs, JC, Gehre, O, Herrmann, A, Ignacz, P, Jakobi, M, Kálvin, S, Kaufmann, M, Kocsis, G, Kurzan, B, Maggi, C, Manso, ME, Maraschek, M, Mertens, V, Mück, A, Murmann, HD, Neu, R, Nunes, I, Reich, D, Reich, M, Saarelma, S, Sandmann, W, Stober, J & Vogl, U 2003, 'ELM frequency control by continuous small pellet injection in ASDEX upgrade', Nuclear Fusion, vol. 43, no. 10, pp. 1110-1120. https://doi.org/10.1088/0029-5515/43/10/012
Lang PT, Neuhauser J, Horton LD, Eich T, Fattorini L, Fuchs JC et al. ELM frequency control by continuous small pellet injection in ASDEX upgrade. Nuclear Fusion. 2003 Oct;43(10):1110-1120. https://doi.org/10.1088/0029-5515/43/10/012
Lang, P. T. ; Neuhauser, J. ; Horton, L. D. ; Eich, T. ; Fattorini, L. ; Fuchs, J. C. ; Gehre, O. ; Herrmann, A. ; Ignacz, P. ; Jakobi, M. ; Kálvin, S. ; Kaufmann, M. ; Kocsis, G. ; Kurzan, B. ; Maggi, C. ; Manso, M. E. ; Maraschek, M. ; Mertens, V. ; Mück, A. ; Murmann, H. D. ; Neu, R. ; Nunes, I. ; Reich, D. ; Reich, M. ; Saarelma, S. ; Sandmann, W. ; Stober, J. ; Vogl, U. / ELM frequency control by continuous small pellet injection in ASDEX upgrade. In: Nuclear Fusion. 2003 ; Vol. 43, No. 10. pp. 1110-1120.
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AU - Lang, P. T.

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AU - Fattorini, L.

AU - Fuchs, J. C.

AU - Gehre, O.

AU - Herrmann, A.

AU - Ignacz, P.

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AU - Kálvin, S.

AU - Kaufmann, M.

AU - Kocsis, G.

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AU - Maggi, C.

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AU - Mertens, V.

AU - Mück, A.

AU - Murmann, H. D.

AU - Neu, R.

AU - Nunes, I.

AU - Reich, D.

AU - Reich, M.

AU - Saarelma, S.

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AU - Stober, J.

AU - Vogl, U.

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