ELM pacing and high-density operation using pellet injection in the ASDEX Upgrade all-metal-wall tokamak

P. T. Lang, A. Burckhart, M. Bernert, L. Casali, R. Fischer, O. Kardaun, G. Kocsis, M. Maraschek, A. Mlynek, B. Plodieckl, M. Reich, F. Ryter, J. Schweinzer, B. Sieglin, W. Suttrop, T. Szepesi, G. Tardini, E. Wolfrum, D. Zasche, H. Zohm

Research output: Contribution to journalArticle

34 Citations (Scopus)

Abstract

Edge-localized mode (ELM) triggering and pacing in an all-metal wall environment shows significant differences to a first-wall configuration containing carbon. Here we report on experiments performed at ASDEX Upgrade revisiting the issue with all plasma-facing surfaces now fully replaced by tungsten. This investigation was motivated by experimental findings indicating that ELM triggering becomes more intricate when the carbon is replaced by a metal wall. ELM pacing could no longer be achieved by magnetic triggering in ASDEX Upgrade under conditions that previously showed a positive response. Also, recent investigations at JET indicate that a lag time occurs in pellet ELM triggering when operating with the new ITER-like wall. The ASDEX Upgrade centrifuge-based launching system was revitalized and upgraded for this study, now allowing detailed analysis of the ELM trigger response. The appearance of a lag time for pellet ELM triggering in an all-metal wall environment was confirmed. While different lag time durations were found for several type-I ELMy H-mode scenarios, the magnitude of the pellet perturbation was found to cause no difference. Reducing the auxiliary heating power for ELM triggering clearly makes the pellet tool less efficient for ELM control purposes; however, this affords a major benefit when applied for fuelling. Plasma operation with benign ELM behaviour at core densities far beyond the Greenwald limit was demonstrated, this being fully reversible and not affecting the energy confinement.

Original languageEnglish
Article number083009
JournalNuclear Fusion
Volume54
Issue number8
DOIs
Publication statusPublished - Aug 1 2014

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pellets
injection
metals
time lag
centrifuges
refueling
carbon
launching
tungsten
actuators
perturbation
heating
causes
configurations

Keywords

  • all metal wall
  • ELM pacing
  • pellet
  • tokamak

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Nuclear and High Energy Physics

Cite this

Lang, P. T., Burckhart, A., Bernert, M., Casali, L., Fischer, R., Kardaun, O., ... Zohm, H. (2014). ELM pacing and high-density operation using pellet injection in the ASDEX Upgrade all-metal-wall tokamak. Nuclear Fusion, 54(8), [083009]. https://doi.org/10.1088/0029-5515/54/8/083009

ELM pacing and high-density operation using pellet injection in the ASDEX Upgrade all-metal-wall tokamak. / Lang, P. T.; Burckhart, A.; Bernert, M.; Casali, L.; Fischer, R.; Kardaun, O.; Kocsis, G.; Maraschek, M.; Mlynek, A.; Plodieckl, B.; Reich, M.; Ryter, F.; Schweinzer, J.; Sieglin, B.; Suttrop, W.; Szepesi, T.; Tardini, G.; Wolfrum, E.; Zasche, D.; Zohm, H.

In: Nuclear Fusion, Vol. 54, No. 8, 083009, 01.08.2014.

Research output: Contribution to journalArticle

Lang, PT, Burckhart, A, Bernert, M, Casali, L, Fischer, R, Kardaun, O, Kocsis, G, Maraschek, M, Mlynek, A, Plodieckl, B, Reich, M, Ryter, F, Schweinzer, J, Sieglin, B, Suttrop, W, Szepesi, T, Tardini, G, Wolfrum, E, Zasche, D & Zohm, H 2014, 'ELM pacing and high-density operation using pellet injection in the ASDEX Upgrade all-metal-wall tokamak', Nuclear Fusion, vol. 54, no. 8, 083009. https://doi.org/10.1088/0029-5515/54/8/083009
Lang, P. T. ; Burckhart, A. ; Bernert, M. ; Casali, L. ; Fischer, R. ; Kardaun, O. ; Kocsis, G. ; Maraschek, M. ; Mlynek, A. ; Plodieckl, B. ; Reich, M. ; Ryter, F. ; Schweinzer, J. ; Sieglin, B. ; Suttrop, W. ; Szepesi, T. ; Tardini, G. ; Wolfrum, E. ; Zasche, D. ; Zohm, H. / ELM pacing and high-density operation using pellet injection in the ASDEX Upgrade all-metal-wall tokamak. In: Nuclear Fusion. 2014 ; Vol. 54, No. 8.
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