Charge-state independent anomalous transport for a wide range of different impurity species observed at Wendelstein 7-X
A. Langenberg, T. Wegner, N. Pablant, O. Marchuk, B. Geiger, N. Tamura, R. Bussiahn, M. Kubkowska, A. Mollén, P. Traverso, H. M. Smith, G. Fuchert, S. Bozhenkov, H. Damm, E. Pasch, K. J. Brunner, J. Knauer, M. Beurskens, R. Burhenn, R. C. Wolf, W7-X Team
Abstract
In this paper, the plasma volume averaged impurity confinement of selected charge states and impurity species has been characterized for the Stellarator Wendelstein 7-X (W7-X), covering a wide range of atomic charges (Z = 12–44) and atomic masses (M = 28–184). A comparison of the experimental findings to theoretical neoclassical and turbulent transport expectations suggests, aside from/in addition to the neoclassical transport, an additional significant anomalous transport mechanism, which is not inconsistent with the predictions of a turbulence dominated impurity transport and is in agreement with the experimental results from recent transport studies based on the direct measurements of impurity diffusion profiles, performed at W7-X.