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arXiv · 1801.09495

Oscillatory relaxation of zonal flows in a multi-species stellarator plasma

E. Sánchez·I. Calvo·J. L. Velasco·F. Medina·A. Alonso·P. Monreal·R. Kleiber·the TJ-II team
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Abstract

The low frequency oscillatory relaxation of zonal potential perturbations is studied numerically in the TJ-II stellarator (where it was experimentally detected for the first time). It is studied in full global gyrokinetic simulations of multi-species plasmas. The oscillation frequency obtained is compared with predictions based on single-species simulations using simplified analytical relations. It is shown that the frequency of this oscillation for a multi-species plasma can be accurately obtained from single-species calculations using extrapolation formulas. The damping of the oscillation and the influence of the different inter-species collisions is studied in detail. It is concluded that taking into account multiple kinetic ions and electrons with impurity concentrations realistic for TJ-II plasmas allows to account for the values of frequency and damping rate in zonal flows relaxations observed experimentally.

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E. Sánchez, I. Calvo, J. L. Velasco, F. Medina, A. Alonso, P. Monreal, R. Kleiber, the TJ-II team. 2018-01-29. Oscillatory relaxation of zonal flows in a multi-species stellarator plasma. https://doi.org/10.1088/1361-6587/aad370

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