Particle drift trajectories in the rotating field of the dynamic ergodic divertor in the TEXTOR tokamak - A Monte Carlo study

Statistical properties of the guide center trajectories are analyzed in the boundary region of the TEXTOR tokamak. The magnetic configuration investigated is a static magnetic field model consisting of a typical TEXTOR equilibrium with the following parameters: B-T= 2.2 T at the magnetic axis, and a limiter q value of q(a) = 4.2 and a perturbation. The perturbing field is created by the dynamic ergodization divertor (DED) coil system with a nominal current value of 10 kA. Both of the possible methods of operation: the static and the rotating one have been analyzed. Based on a randomly generated ensemble of 7 x 10(3) initial conditions the main statistical properties of the trajectories are reported. (C) 1997 Elsevier Science S.A

Test particle transport in perturbed magnetic fields in tokamaks

Numerical calculations of magnetic field line trajectories in a tokamak are used to investigate the common hypotheses that (i) field lines in a chaotic field make a Gaussian random walk and (ii) that the poloidal component of the magnetic field is uniform in regions with a chaotic magnetic field. Both hypotheses are found invalid in typical tokamak conditions. A test particle transport model in the so-called "collisionless diffusion" limit is presented, based on the field line excursions in numerical simulations. Decorrelation mechanisms that effectively enhance the transport in a stochastic field are investigated. (C) 1999 American Institute of Physics. [S1070-664X(99)02406-4]