Erosion Measurements of W and SiC Materials for RF Antenna Applications

Antennas in fusion reactors generate radio frequency (RF) fields and plasma sheaths that interact with the local plasma which can result in increased erosion of the antenna structure. The RF Plasma Interaction Experiment (RF PIE) at Oak Ridge National Lab (ORNL) is used to simulate this RF antenna structure. RF PIE is an Electron Cyclotron Resonance microwave-based plasma source (2.45 GHz, <5 kW) with an RF biased electrode. RF PIE can provide relatively clean spectral plasmas and a simplified viewing geometry with a large solid angle making spectral measurements easier to capture. One side effect of RF fields and the RF sheaths they produce is increased sputtering rates. Antennas are commonly made of tungsten which can withstand the high temperatures from a fusion plasma, but as a high-Z material it will result in excessive radiative power losses in the plasma when introduced as an impurity. Alternatively, silicon carbide (SiC) is a lower-Z material that will result in lower radiative emission and also has been demonstrated to be less susceptible to neutron damage. Pure silicon carbide will be compared with an alternate manufacturing technique that uses SiC fibers to reinforce the SiC matrix. Adding the fiber-reinforcement has been shown to increase the material’s sputter resistance and overall mechanical strength. This presentation will show a comparison between pure tungsten, SiC, and fiber-reinforced SiC with regards to its manufacturability and suitability for an RF plasma environment.