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Abstract

In the core of a burning fusion plasma, the contamination by impurities has to be kept below a critical level. Understanding and control of impurity transport and accumulation are thus an essential issue. Impurity injection experiments have been performed to determine the impurity transport coefficients in the core and in the steep gradient region of H-mode plasmas. The measurements in the edge were edge-localized-mode resolved, and in the center, sawtooth-resolved transport coefficients were obtained for several species covering a wide range of ion charges. Comparison of the experimental values with impurity transport simulations revealed the contribution of anomalous and neoclassical transport in the different parts of the plasma. Discharge scenarios, which show impurity accumulation, were identified and control schemes were demonstrated.