Impurity effects on residual zonal flow in deuterium (D)-tritium (T) plasmas

TL;DR

This study investigates how impurities influence residual zonal flow levels in D-T plasmas, revealing that impurity size and concentration can significantly modify turbulence regulation and plasma confinement.

Contribution

It provides new insights into impurity effects on residual zonal flow levels in D-T plasmas, highlighting the impact of impurity size and concentration on turbulence suppression.

Findings

Impurities with larger (smaller) gyroradii increase (decrease) residual ZF at intermediate scales.

Most impurities increase residual ZF at short scales.

Heavy impurities weaken the trend of stronger residual ZF in D-T plasmas.

Abstract

Significant effects of impurities on residual zonal flow (ZF) in deuterium (D)-tritium (T) plasmas are found. When the gyroradius of impurities is larger (smaller) than that of main ions, the intermediate scale (radial wavelength between trapped ion radial width $\rho_{bi}$ and trapped electron radial width $\rho_{be}$) residual ZF level is increased (decreased) due to the presence of various impurities with the tolerance concentration in JET and ITER, even for trace tungsten (W). For short scale (radial wavelength comparable to $\rho_{be}$) region, the residual ZF level is increased by most of the impurities. Moreover, the trend of stronger intermediate residual ZF in D-T plasmas with heavier effective isotope mass is weakened by non-trace impurities, but is not influenced by trace W. These results reveal that the presence of impurities can modify residual ZF, and possibly further affect the ZF regulation of turbulence as well as the associated anomalous transport and confinement in magnetic fusion plasmas. The potential relevance of our findings to experimental observations and simulation results is discussed.