Additive Manufacture of GRCop Waveguides for Fusion

The high electrical and thermal conductivities of copper make it ideal for plasma facing components such as heat sinks and waveguides. To improve plasma performance and steady state tokamak operation, one path is off-axis current drive for current profile control. Radio-frequency power is among the leading contenders but the harsh environment poses significant challenges. An innovative solution to this complex problem is to launch the lower hybrid waves from the high- field-side instead of the low-field-side of the tokamak. This relocation is predicted to dramatically improve wave penetration, current drive efficiency, and launcher robustness in a reactor environment. For efficient current drive, transmission losses must be minimized. Presently, first wall temperatures may be as high as 800C, where copper is a poor structural material. Recent development of a copper alloy, GRCop-84, provides a potential solution with near copper like electrical and thermal conductivities with significantly improved strength at elevated temperatures. However, components produced from GRCop must be made using powder metallurgy techniques. Additive manufacturing techniques based on powder bed fusion have recently been used to produce GRCop components, but component size is limited. The development of additive manufacturing techniques that can produce meter long GRCop waveguides would be extremely beneficial. Therefore, blown powder techniques based on High Pressure Cold Spray (HPCS), which can produce components 2m in length and greater, will be developed to produce meter size GRCop waveguides. During Phase I, a parameters-characterization-properties development effort will be performed and samples will be produced for testing at MIT-PSFC. During Phase II, the techniques necessary for the HPCS forming of full-size GRCop waveguides will be developed. Tests of these advanced waveguides will then be performed to yield critical data on performance. The additive manufacturing techniques developed during this effort will be applicable to copper and copper alloys as well as other ductile materials for producing large free form components with improved surface finishes for government and commercial applications. These include aerospace, defense, propulsion, power generation, medical, electronic, and corrosion protection coatings.