Reduction of edge localized mode intensity on DIII-D by on-demand triggering with high frequency pellet injection and implications for ITERa)

L. R. Baylor, N. Commaux, T. C. Jernigan, S. J. Meitner, S. K. Combs, R. C. Isler, E. A. Unterberg, N. H. Brooks, T. E. Evans, A. W. Leonard, T. H. Osborne, P. B. Parks, P. B. Snyder, E. J. Strait, M. E. Fenstermacher, C. J. Lasnier, R. A. Moyer, A. Loarte, G.T.A. Huijsmans, S. Futatani

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

The injection of small deuterium pellets at high repetition rates up to 12× the natural edge localized mode (ELM) frequency has been used to trigger high-frequency ELMs in otherwise low natural ELM frequency H-mode deuterium discharges in the DIII-D tokamak [J. L. Luxon and L. G. Davis, Fusion Technol. 8, 441 (1985)]. The resulting pellet-triggered ELMs result in up to 12× lower energy and particle fluxes to the divertor than the natural ELMs. The plasma global energy confinement and density are not strongly affected by the pellet perturbations. The plasma core impurity density is strongly reduced with the application of the pellets. These experiments were performed with pellets injected from the low field side pellet in plasmas designed to match the ITER baseline configuration in shape and normalized β operation with input heating power just above the H-mode power threshold. Nonlinear MHD simulations of the injected pellets show that destabilization of ballooning modes by a local pressure perturbation is responsible for the pellet ELM triggering. This strongly reduced ELM intensity shows promise for exploitation in ITER to control ELM size while maintaining high plasma purity and performance.
Original languageEnglish
Article number82513
JournalPhysics of Plasmas
Volume20
Issue number8
DOIs
Publication statusPublished - 1 Aug 2013
Externally publishedYes

Keywords

  • ballooning instability
  • high-frequency discharges
  • plasma beam injection heating
  • plasma density
  • plasma impurities
  • plasma magnetohydrodynamics
  • plasma simulation
  • plasma toroidal confinement
  • Tokamak devices
  • Tokamaks spherical tokamaks
  • Magnetohydrodynamic and fluid equation
  • Impurities in plasmas
  • Magnetohydrodynamics
  • Macroinstabilities
  • Plasma heating by particle beams

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