Estimating Core Density Profiles of Lithium Using GX Turbulence Simulations

Utilization of lithium in future tokamaks is an attractive approach to mitigate heat flux to the walls and the divertor region while causing minimal disturbance to the core plasma. In lithium divertor concept studies, codes such as SOLPS are often employed to determine and minimize the upstream lithium density through design alteration. This scrape off layer analysis of lithium for such designs is fairly extensive, but there is less understanding of how lithium is transported into the core of the device. To understand and estimate the core lithium density profiles we utilize a local gyrokinetic turbulence code, GX. We use JET geometry and parameters to investigate lithium particle transport into the core of the device due to turbulence driven by the background electron and deuterium temperature and density gradients. We will analyze how the equilibrium lithium gradient scale length (when the radial lithium flux vanishes) depends on these parameters along with others (such as plasma shape) to examine what factors have the most significant impact on lithium transport into the core plasma. We will scan the lithium fraction to check when a trace lithium approximation works. We endeavor to increase our understanding of whole device lithium transport, through these core studies, to the benefit of future lithium-based heat mitigation systems in tokamaks.