LNF:Fuelling and Impurity Control Studies in the stellarators TJ-II and W7-X using Cryogenic Pellets and Tracer-Encapsulated Solid Pellets (TESPEL): Difference between revisions

6. Experiments in the LHD with continuous lithium power dropping have allowed the creation of a reactor-relevant high-density plasma regime [14, 15]. This is characterized by increased energy confinement as well as surpressed turbulence and reduced impurity confinement. The transition to this regime is driven by the continuous dropping of Li-powder grains into the plasma. When such plasmas are compared to plasmas without Li-powder the achieved high-performance characteristics include: increased plasma energy & core electron temperature, reduced plasma-wall interaction, and an up to one order of magnitude reduction in plasma turbulence across the whole plasma radius in the frequency range 5 to 500 kHz. In addition, and contrary to expectations for high-density plasmas in stellarators, it is seen, when injecting TESPELs to deposit tracers in the core of this high-performance phase, that impurity confinement is significantly reduced for plasmas with Li powder when compared to confinement in discharges without Li-powder. These new results demonstrate the potential of continuous dropping of Li-powder into stellarator plasmas for simultaneously accessing enhanced confinement regimes while avoiding impurity accumulation.

== Peer-reviewed articles associated to this Project (since 2022) ==

[15] Reduction of impurity confinement times in lithium-powder induced reduced-turbulence plasmas in the LHD, D. Medina-Roque, F. Nespoli, I. García-Cortés, K. J. McCarthy, N. Tamura, C. Suzuki, M. Goto, T. Kawate, Y. Kawamoto, M. Yoshinuma, K. Ida, K. Tanaka, T. Tokuzawa, H. Funaba, I. Yamada and the LHD team, in preparation for Nucl. Fusion Lett.