Investigation of triangularity impact on impurity content in JET-ILW H, D, T, and DT plasmas

Abstract

The work presents the recent outcome of the research on Joint European Torus with ITER-like wall (JET-ILW) concerning Be, mid-Z (Ni, Cu, Fe), and high-Z (W) impurities for a selection of Neutral Beam Injection-heated, ELMy H-mode pulses using visible and vacuum–ultraviolet spectroscopy together with bolometry diagnostic. The investigation is focused on the evaluation of the plasma triangularity (δ) impact on the impurity radiation in hydrogen (H), deuterium (D), tritium (T), and deuterium–tritium (DT) plasmas for pulses described in [P. A. Schneider, Nucl. Fusion 63, 112010 (2023)]. The variations of δ were in the range of 0.21–0.31 for different time windows with low magnetic toroidal field (Bt=1.7 T) and plasma current (Ip=1.4 MA) in the corner–corner configuration, that is with both the inner and outer strike points on the horizontal W-coated divertor target plates. The results confirm the rise in Be flux with plasma isotope and lower δ leading to higher plasma density close to the plasma wall. The dominant role of W as a source of plasma radiation has also been confirmed. For mid-Z impurities and W, the variations in their densities due to δ change are negligible and the rise in their densities is observed with higher isotope mass, although this effect is often masked by the dominant role of ELM frequency on the impurity level. The impurity radiation losses based on bolometry together with the W intensity are ruled by the changes in the electron density and are well correlated when the Te profiles are conserved.