Assessing the Viability of Carbide Dispersion-Strengthened Tungsten Composites as Plasma-Facing Materials for RF Antenna Applications

Radiofrequency (RF) antennas are likely to be essential systems in fusion reactors to provide ion heating to the bulk plasma. They generate RF fields and plasma sheaths that interact with the local plasma in front of the antenna, which can result in increased erosion of the antenna structure compared to the typical DC sheath shielding most components. The RF Plasma Interaction Experiment (RF PIE) at Oak Ridge National Lab (ORNL) simulates this RF antenna environment. RF PIE is an Electron Cyclotron Resonance microwave-based plasma source (2.45 GHz, <5 kW) with an RF biased electrode. Tungsten, commonly used for antennas due to its high-temperature resistance, is a high-Z material that leads to excessive radiative power losses when introduced as an impurity. Carbide dispersion-strengthened tungsten (CDS-W) composites contain <5% SiC, TaC, or TiC and have been shown to increase mechanical strength and resistance to radiation damage. This work compares pure W and CDS-W for RF plasma compatibility and manufacturability.

Among the many factors influencing antenna material selection, this presentation focuses on sputtering resistance and minimizing hydrogen retention. Micro-trenches and depth markers are etched into samples, and SEM images taken before and after exposures measure the net erosion. A spectrometer tracks sputtering rates during exposures to confirm erosion calculations. Thermal desorption spectroscopy (TDS) assesses changes in hydrogenic retention between pre- and post-exposure.