Integrated modeling of impurity transport in KSTAR Carbon and Tungsten divertor plasmas

Tungsten (W) is selected as the divertor material in high performance tokamak device considering its ability to endure high heat flux from edge plasma with low erosion rate and low hydrogen isotope retention. However, excessive accumulation of W impurities in the core region can degrade overall plasma performance, challenging the sustainment of H-mode confinement and potentially leading to radiative collapse of the plasma [1][2]. The tungsten impurities in KSTAR plasmas exhibit strong poloidal asymmetry mainly due to their high mass and charge, and in the presence of toroidal rotation [3] neoclassical inward convection can be enhanced by up to an order of magnitude [4]. In this study, the JINTRAC [5] integrated modeling suite is applied to the KSTAR plasmas firstly to find valid modelling assumptions and settings by comparing with experimental data and results from other codes, then to study the transport characteristics of W impurities and their impact on plasma performance both in the KSTAR carbon and tungsten divertor plasmas. To model the tungsten transport influenced by KSTAR’s high toroidal rotation, a high fidelity neoclassical model accounting for the poloidal asymmetry of impurities, NEO [6], is employed. This study focuses on the verification of the JINTRAC modelling assumptions and setting, and validation of the applied physics models through quantitative assessment of the impacts of impurity accumulation in KSTAR plasmas, and contributes to developing high-performance KSTAR operation scenarios by investigating potential solutions avoiding excessive tungsten influx.