Impact of impurities on zonal flow driven by trapped electron mode turbulence

TL;DR

This paper investigates how different impurities affect the generation of zonal flows driven by trapped electron mode turbulence in fusion plasmas, revealing that impurity type and density profiles significantly influence ZF growth rates.

Contribution

It derives an expression for ZF growth rate considering impurities and analyzes how impurity type and profiles alter ZF dynamics in plasma turbulence.

Findings

Fully ionized non-trace light impurities with flat profiles reduce ZF growth rate.

Highly ionized trace tungsten slightly reduces ZF growth rate.

Steep impurity profiles can enhance ZF growth rate.

Abstract

The impact of impurities on the generation of zonal flow (ZF) driven by collisonless trapped electron mode (CTEM) turbulence in deuterium (D)-tritium (T) plasmas is investigated. The expression for ZF growth rate with impurities is derived by balancing the ZF potential shielded by polarization effects and the ZF modulated radial turbulent current. Then, it is shown that the maximum normalized ZF growth rate is reduced by the presence of the fully ionized non-trace light impurities with relatively flat density profile, and slightly reduced by highly ionized trace tungsten (W). While, the maximum normalized ZF growth rate can be also enhanced by fully ionized non-trace light impurities with relatively steep density profile. In particular, the effects of high temperature helium from D-T reaction on ZF depend on the temperature ratio between electron and high temperature helium. The possible relevance of our findings to recent experimental results and future burning plasmas is also discussed.