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Including electron kinetic effects in FRC simulations

Author: Elena V Belova
Requested Type: Poster Only
Submitted: 2011-06-10 20:50:39

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Contact Info:
PPPL
PO Box 451
Princeton, NJ   08543
USA

Abstract Text:
A kinetic description for the electrons has been implemented in the 3D nonlinear hybrid HYM code. In the code, the electrons are described as delta-f drift kinetic particles, and their trajectories are advanced using a second-order time-centered scheme with a time step smaller than the ion time step (sub-cycling). The electron pressure and ion current density are calculated at the ion time step, and used to advance the field equations. Electrons equations are parallelized using MPI with one-dimensional domain decomposition. Initial conditions are generated assuming that electron distribution function is a function of the three integrals of motion, and the electron temperature is fraction of the ion temperature. Numerical benchmarks have been performed in order to verify conservation laws, and study the accuracy of electron orbit integration depending on the electron time step. A new version of the HYM code with drift-kinetic electron description has been used to study the effects of kinetic electrons on FRC equilibrium and relaxation. Simulations have been performed using a fluid description for the thermal ions and drift-kinetic equations for the thermal electrons. It is shown that both parallel and perpendicular electron pressure evolves from the initial peaked profile towards hollow profiles with local minimum near the FRC magnetic null point. Similar behavior is observed in the electron density evolution. Comparisons of the two-fluid simulation results and the drift-kinetic electrons simulation results demonstrate that the ions spin up faster, when the drift-kinetic electron model is used. This could be explained by the deviation of the initial configuration from true equilibrium, which results in the evolution of the plasma density in such a way, that it is no longer a function of the poloidal flux. A significant ion toroidal spin-up is obtained even in the simulations with low plasma resistivity when the drift-kinetic electron version of the HYM is used. Initial results of 3D simulations studying the effects of kinetic electrons on the FRC stability will be presented.

Characterization: A7

Comments:

University of Washington

Workshop on Innovation in Fusion Science (ICC2011) and
US-Japan Workshop on Compact Torus Plasma
August 16-19, 2011
Seattle, Washington

ICC 2011