Gyrokinetic study of the role of {beta} on electron particle transport in tokamaks

Journal Article · Fri Oct 15 00:00:00 EDT 2010 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.3503622· OSTI ID:21421250

Hein, T; Angioni, C; Fable, E ^[1]; Candy, J ^[2]

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1. Max-Planck-Institut fuer Plasmaphysik, IPP-EURATOM Association, D-85748 Garching (Germany)
2. General Atomics, P.O. Box 85608, San Diego, California (United States)

Electromagnetic effects on the radial transport of electrons in the core of tokamak plasmas are studied by means of linear and nonlinear gyrokinetic simulations with the code GYRO[J. Candy and R. E. Waltz, J. Comput. Phys. 186, 545 (2003)] and by an analytical derivation. The impact of a finite {beta}, that is, a finite ratio of the plasma pressure to the magnetic pressure, is considered on the fluctuations of the magnetic field through Ampere's law, as well as on the geometrical modification of the vertical drift produced by the Shafranov shift in the magnetic equilibrium, which, for realistic descriptions, has to be included in both electrostatic and electromagnetic modeling. The condition of turbulent particle flux at the null, which allows the determination of stationary logarithmic density gradients when neoclassical transport and particle sources are negligible, is investigated for increasing values of {beta}, in regimes of ion temperature gradient and trapped electron mode turbulence. The loss of adiabaticity of passing electrons produced by fluctuations in the magnetic vector potential produces an outward convection. When the magnetic equilibrium geometry is kept fixed, this induces a strong reduction of the stationary logarithmic density gradient with increasing {beta}. This effect is partly compensated by the geometrical effect on the vertical drift. This compensation effect, however, is significantly weaker in nonlinear simulations as compared to quasilinear calculations. A detailed comparison between quasilinear and nonlinear results reveals that the predicted value of the logarithmic density gradient is highly sensitive on the assumptions on the wave number spectrum applied in the quasilinear model. The qualitative consistency of the theoretical predictions with the experimental results obtained so far on the dependence of density peaking on {beta} is discussed by considering the additional impact, with increasing {beta}, of a particle source delivered by neutral beam injection heating. (Some figures in this article are in color only in the electronic version.)

• OSTI ID: 21421250
• Journal Information: Physics of Plasmas, Vol. 17, Issue 10; Other Information: DOI: 10.1063/1.3503622; (c) 2010 American Institute of Physics; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
BEAM INJECTION HEATING
CHARGED-PARTICLE TRANSPORT
CONVECTION
ION TEMPERATURE
MAGNETOHYDRODYNAMICS
PLASMA
PLASMA DENSITY
PLASMA SIMULATION
TEMPERATURE GRADIENTS
TOKAMAK DEVICES
TRAPPED ELECTRONS
TURBULENCE
CLOSED PLASMA DEVICES
ELECTRONS
ELEMENTARY PARTICLES
ENERGY TRANSFER
FERMIONS
FLUID MECHANICS
HEAT TRANSFER
HEATING
HYDRODYNAMICS
LEPTONS
MASS TRANSFER
MECHANICS
PLASMA HEATING
RADIATION TRANSPORT
SIMULATION
THERMONUCLEAR DEVICES