Physics Modeling of Tokamak Transport, a Grand Challenge for Controlled Fusion

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Abstract
A challenge facing fusion is accurate prediction and understanding of plasma and heat confinement. Com puters and modeling techniques have advanced to where we can envision simulating real Tokamaks start ing from fundamental physics models. Charged parti cles in magnetic fields execute rapidly gyrating mo tions about the field. These orbits gradually drift where electric fields and magnetic nonuniformities exist. The gyrokinetic model averages out the rapid gyration and treats the plasma as a large number of drifting rings of charge and current; large numbers (approx. 106) of such rings are followed in their self-consistent electric and magnetic fields. Three-dimensional simulations of plasma and heat confinement for situations relevant to fusion give turbulence spectra and transport coeffi cients similar to experiments. Simpler particle models of plasma run on hypercubes achieves a high degree of parallelism (95%). With new parallel machines sub stantial gains in speed and memory can be expected; modeling of real Tokamaks should be possible.