Fast Integrated Modeling of Light to Medium Impurities in FUSE for Future Reactors

In tokamak fusion devices, impurities play a critical role in determining plasma performance. To address challenges in impurity transport modeling, including the computational cost of tracking multiple charge states and reliance on computed transport coefficients, we present a time-efficient method based on an impurity bundling technique. The method simplifies impurity transport by assuming a single average charge state, valid when the particle confinement time is much longer than ionization and recombination timescales—a condition expected to hold in future fusion devices. The method has been applied in the power balance solvers TGYRO and FluxMatcher, the latter embedded in the whole-device modeling framework FUSE. This eliminates the need to calculate individual charge states and transport coefficients, reducing simulation complexity. Validation against the Aurora model using DIII-D data shows that the method captures key impurity transport features, with Root Mean Square Error below 2 percent. Its computational efficiency and accuracy make it well suited for integrated modeling of future reactors such as ITER and the Fusion Pilot Plant.