RF Validation of a Monolithic Additive Manufactured LHCD Launcher

Additive Manufacture (AM) of Radio Frequency (RF) launchers enabled the HFS LHCD launchers installed on DIII-D. Increased L-PBF build volume enabled monolithic AM of launchers and chemical polishing (CP) mitigated residual surface roughness from the AM process for RF loss equivalent to extruded OFC. The CP process required an addition of 250µm of surface material during AM to be polished off to the final dimensions; the combined accuracy of L-PBF AM and CP surface refinement determine the accuracy of the RF tuning elements and phase shifters in the launcher. Launcher validation is accomplished through RF measurements of power splitter resonance locations and phase shifts with a vector network analyzer that are compared against COMSOL simulations. Neutron activation of the niobium on the current GRCop42 alloy results in long-lived waste; replacement AMed copper alloys are sought as a replacement. Three new reduced-activation copper alloys were developed using TiCr₂, TaCr₂, or TaV₂ Laves phase precipitates to replace NbCr₂ in current GRCop alloys to mitigate high level waste generation. FIB sectioning of gas atomized and L-PBF precipitates showed precipitate refinement similar to GRCop implying similar tensile properties. Work supported by US DOE under DE-SC0014264.