Database study of impurity confinement time scaling on the DIII-D tokamak

Understanding and predicting energy confinement time (τ_E) and impurity confinement time (τ_imp) are essential for ITER and future fusion reactors, as impurities strongly influence plasma performance and fusion gain. While τ_E has been extensively studied, τ_imp remains less understood due to measurement challenges and limited database studies. In this work, we present a comprehensive impurity confinement database from the DIII-D tokamak, compiled from about 500 impurity injections across a broad range of plasma scenarios, including laser blow-off (LBO), non-recycling gas puffs, and spontaneous impurity events. The dataset spans all major DIII-D regimes, such as ELMy H-mode, RMP H-mode, hybrid, L-mode, negative triangularity, QH-mode, WPQH-mode, high-β_p, and super H-mode. Impurities range from low-Z elements like fluorine (Z=9) to high-Z elements like tungsten (Z~45). We apply data-driven modeling and statistical analysis to extract scaling laws and identify predictive trends in impurity confinement, using both dimensional and dimensionless plasma parameters. This work enhances impurity transport modeling and supports scenario development and impurity control strategies for high-performance fusion plasmas.





Category: undergraduate research

The work supported in part by US DoE under the Science Undergraduate Laboratory Internship (SULI) program under DE-FC02-04ER54698, DE-SC0014264