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Scrape-off-layer current loops and floating potential in limited tokamak plasmas

  • J. Loizu (a1), J. A. Morales (a2), F. D. Halpern (a3), P. Ricci (a4) and P. Paruta (a4)...


We investigate the question of how plasma currents circulate and close in the scrape-off-layer (SOL) of convection-limited tokamak plasmas. A simplified two-fluid model describes how currents must evacuate charge at the sheaths due to cross-field currents that are not divergence-free. These include turbulence-driven polarization currents and poloidally asymmetric equilibrium diamagnetic currents. The theory provides an estimate for the radial profile of the floating potential, which reveals a dipolar structure like the one observed experimentally. Simulations with a fluid turbulence code provide evidence for the predicted behaviour of currents and floating potential.


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