Kinetic Simulations of Ion Transport in Fusion Devices by Andrés Bustos Molina

Author:Andrés Bustos Molina
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

3.3.3 Outward Fluxes and Velocity Distribution

The average outward particle () and energy () flux profiles (Figs. 3.9 and 3.10) are also calculated. Both are normalized to the number of particles and all the measurements take place in two times: before the ripple influences the ion motion and around one ion confinement time (around one second, according to Fig. 3.5). In order to increase the statistics and save memory, ISDEP averages the flux profile in the magnetic surface, neglecting any toroidal and poloidal asymmetry. Since in the innermost part of ITER there is no ripple, the fluxes tend to smooth and reduce the local effect of the ripple. The global result is that both fluxes become appreciably larger with the ripple at , causing the enhancement of particle losses. The particle flux grows monotonically with for long times due to the fact that no particle sources or sinks are considered inside the plasma. A flattening of the flux is observed at due to the combination of the gradients at this plasma zone, where the potential and temperature driven fluxes produce a constant flux. The heat flux is not monotonic showing that the kinetic energy of the particles is modified by the presence of the electric field.

In addition, the features of the velocity distribution of the surviving particles are characterized with the cumulants of the distribution function. The cumulants are normalized moments of the distribution which can be used to explore the non-Maxwellian features. In particular, the Binder cumulant is defined as

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