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Open Access Publications from the University of California

Flux-driven simulations of turbulence collapse

  • Author(s): Park, GY
  • Kim, SS
  • Jhang, H
  • Diamond, PH
  • Rhee, T
  • Xu, XQ
  • et al.

Published Web Location

© 2015 AIP Publishing LLC. Using three-dimensional nonlinear simulations of tokamak turbulence, we show that an edge transport barrier (ETB) forms naturally once input power exceeds a threshold value. Profiles, turbulence-driven flows, and neoclassical coefficients are evolved self-consistently. A slow power ramp-up simulation shows that ETB transition is triggered by the turbulence-driven flows via an intermediate phase which involves coherent oscillation of turbulence intensity and E × B flow shear. A novel observation of the evolution is that the turbulence collapses and the ETB transition begins when RT> 1 at t = tR(RT: normalized Reynolds power), while the conventional transition criterion (ω E × B > γ l i n where ω E × B denotes mean flow shear) is satisfied only after t = tC( >tR), when the mean flow shear grows due to positive feedback.

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