Department of Applied Physics

Plasma turbulence: ELMFIRE

To elucidate the physics behind fundamental transport processes in tokamak plasmas the gyrokinetic ELMFIRE code has been developed within the Fusion and Plasma Physics group and VTT Technical Research Centre of Finland.

Group: Timo Kiviniemi, Laurent Chôné, Susan Leerink
Fluctuations of electron density in gyrokinetic simulation of tokamak turbulence using Elmfire. (poloidal cut)
Turbulent fluctuations of tokamak plasma in ELMFIRE simulation (figure: L. Chôné).

Although regimes exist in current tokamak experiments, in which the plasma is found stable to global MHD modes, the plasma is always in a state of thermodynamic quasi-equilibrium with an abundance of free energy for driving more benign instabilities. These instabilities reduce the confinement time through convection dominated transport (turbulence).

Confinement modes, which are observed to suppress this micro-turbulence (such as the high confinement mode, or H-mode) have been found experimentally. On the other hand, theoretical models of such confinement mode transitions and related phenomena are still incomplete. 

The computational algorithm of the gyrokinetic full-f model ELMFIRE is a Lagrangian explicit/implicit predictor-corrector solver for the reduced Boltzmann equation in a magnetized plasma. For example, it has been applied to numerically investigate on transport phenomena in the tokamak, such as ion temperature gradient and trapped electron modes, zonal flows, and neoclassical feedback to turbulence. 

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