Breakdown Resistant Refractory Metal Coatings for Field-Aligned ICRF Antennas

In fusion plasmas, ion cyclotron range of frequency (ICRF) and lower hybrid range of frequency (LHRF) power is anticipated to be a primary auxiliary heating and current drive sources in next step tokamak experiments like ITER. From a technological perspective, several challenges remain including electrical breakdown and material compatibility with a nuclear environment. Copper has been the primary material used in present experiments due to its high thermal and electrical conductivity. In a nuclear reactor, copper will be restricted to thin coatings due to material swelling from neutron bombardment and poor mechanical strength at high temperature expected in fusion reactors. Recent experimental results suggest that high magnetic field or pulsed surface heating limits the attainable electric fields. Copper alloys with higher tolerance to surface fatigue have indeed shown improvements. The natural extension is to develop high strength and high melting temperature refractory metal coatings that are more tolerant to surface fatigue and compatible with nuclear environment. Recent testing at the Massachusetts Institute of Technology (MIT) has shown considerable promise for refractory metal coatings. However, improvements in density and conductivity are needed. During Phase I, innovative electrochemical forming (EL-Form) techniques will be developed to enable the deposition of 100% dense, high purity, well-adhered refractory metal coatings on Inconel substrates. Plasma Processes will partner with MIT Plasma Science and Fusion Center (PSFC) for this effort. During Phase II, refractory metal coated ICRF antennas will be produced and tested. Commercial Applications and Other Benefits: The development of dense, well-bonded refractory metal coatings on Inconel substrates will enable the fabrication of ICRF antennas with improved breakdown resistance and performance. In addition, the same techniques used to produce these deposits on Inconel substrates can be used for other applications including aerospace, defense, propulsion, power generation, electrical contact and switch gear, semiconductor, crucibles, heat shields, x-ray targets, wear and corrosion protection coatings.