Low-frequency percolation scaling for particle diffusion in electrostatic turbulence
An important point for turbulent transport is determining the scaling law for the diffusion coefficient D due to electrostatic turbulence. Recently a percolation critical exponent (gamma=7/10) has been predicted by Isichenko. The aim of this work consists of testing this prediction for a given realistic model and is studied here by direct simulation of particle trajectories. Guiding centre diffusion in a spectrum of electrostatic turbulence is computed for test particles in a model spectrum, by means of a new parallelized code RADIGUET 2 described here. The spectrum involves only one frequency omega but a large number of randomly phased electrostatic plane waves, propagating isotropically in the plane perpendicular to the confining strong magnetic field. This ensures chaotic trajectories. This set of waves represents standing waves. Their amplitudes depend on wavelength in order to reproduce the k(-3) domain of the observed spectrum in tokamaks. The results indicate a continuous transition for large amplitudes toward a value of gamma=0.704 +/- 0.030 which is compatible with the Isichenko percolation prediction.
Bibliographic Reference: Article: Physical Review E, Vol. 54 (1996) No. 2, pp. 1857-1869
Record Number: 199611255 / Last updated on: 1996-10-29
Original language: en
Available languages: en