Integrated modeling of RF-Induced Tungsten Erosion at ICRH Antenna Structures in the WEST Tokamak

TL;DR

This paper presents STRIPE, a comprehensive modeling framework that predicts RF-induced tungsten erosion and impurity transport in fusion devices, validated against experimental data from the WEST Tokamak, aiding future RF antenna design and impurity management.

Contribution

The paper introduces the integrated STRIPE framework combining multiple physics models to simulate RF-induced tungsten erosion and impurity transport in fusion devices, validated with experimental data.

Findings

RF sheath rectification increases tungsten erosion tenfold.

Highly charged oxygen ions significantly contribute to tungsten sputtering.

Model predictions closely match spectroscopic measurements of tungsten impurities.

Abstract

This paper introduces STRIPE (Simulated Transport of RF Impurity Production and Emission), an advanced modeling framework designed to analyze material erosion and the global transport of eroded impurities originating from radio-frequency (RF) antenna structures in magnetic confinement fusion devices. STRIPE integrates multiple computational tools, each addressing different levels of physics fidelity: SolEdge3x for scrape-off-layer plasma profiles, COMSOL for 3D RF rectified voltage fields, RustBCA code for erosion yields and surface interactions, and GITR for 3D ion energy-angle distributions and global impurity transport. The framework is applied to an ion cyclotron RF heated, L-mode discharge #57877 in the WEST Tokamak, where it predicts a tenfold increase in tungsten erosion at RF antenna limiters under RF-sheath rectification conditions, compared to cases with only a thermal sheath. Highly charged oxygen ions (O6+ and higher) emerge as dominant contributors to tungsten sputtering at the antenna limiters. To verify model accuracy, a synthetic diagnostic tool based on inverse photon efficiency or S/XB coefficients from the ColRadPy-collisional radiative model enables direct comparisons between simulation results and experimental spectroscopic data. Model predictions, assuming plasma composition of 1% oxygen and 99% deuterium, align closely with measured neutral tungsten (W-I) spectroscopic data for the discharge #57877, validating the framework's accuracy. Currently, the STRIPE framework is being extended to investigate plasma-material interactions in other RF-heated linear and toroidal devices, offering valuable insights for RF antenna design, impurity control, and performance optimization in future fusion reactors.