Sheath-Driven Impurity Modeling for Radiofrequency Heating in Fusion Systems

High-power radiofrequency (RF) heating is important in fusion devices, as it is critical to attain plasma temperatures relevant to future fusion reactors. However, challenges such as RF sheath rectification can generate potentials on RF antenna structures of a few hundred eV in existing devices and are projected to reach several keV in ITER. This enhances plasma–material interactions (PMI) and material erosion at the antenna, with eroded material transported into the core plasma and degrading performance. To address this, a novel integrated PMI modeling framework, STRIPE [1], has been developed. STRIPE couples plasma backgrounds from SOLPS/SOLEDGE, RF sheath voltages from COMSOL, surface response from RustBCA, and impurity transport from GITR, while also incorporating ionization balance and ion-energy angle distributions (IEADs) to capture multi-charge sputtering. Applied to WEST, DIII-D, and ITER, STRIPE reproduces key experimental signatures and provides predictive capability for RF-compatible antenna design and impurity control in future devices.

[1] Kumar, A., et al., Integrated modeling of RF-Induced Tungsten erosion at ICRH Antenna structures in the WEST tokamak. Nuclear Fusion, vol. 65, no. 7, 2025, pp. 1-4.