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A semi-analytic power balance model for low (L) to high (H) mode transition power threshold

  • Author(s): Singh, R
  • Jhang, H
  • Kaw, PK
  • Diamond, PH
  • Nordman, H
  • Bourdelle, C
  • Loarte, A
  • et al.

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We present a semi-analytic model for low (L) to high (H) mode transition power threshold (Pth). Two main assumptions are made in our study. First, high poloidal mode number drift resistive ballooning modes (high-m DRBM) are assumed to be the dominant turbulence driver in a narrow edge region near to last closed flux surface. Second, the pre-transition edge profile and turbulent diffusivity at the narrow edge region pertain to turbulent equipartition. An edge power balance relation is derived by calculating the dissipated power flux through both turbulent conduction and convection, and radiation in the edge region. Pthis obtained by imposing the turbulence quench rule due to sheared E × B rotation. Evaluation of Pthshows a good agreement with experimental results in existing machines. Increase of Pthat low density (i.e., the existence of roll-over density in Pthvs. density) is shown to originate from the longer scale length of the density profile than that of the temperature profile. © 2014 AIP Publishing LLC.

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