The primary technical objective of this project is to produce a new Cu alloy with similar material properties to GRCop-84 but with greatly reduced waste disposal rating (WDR) in a fusion nuclear environment. This would be accomplished by replacing the Nb with another alloying element(s). We use novel alloy creation and assessment methods to identify the best performing materials from a variety of potential alloying elements.
RF antennas have a unique set of materials requirements, namely high thermal conductivity, high electrical conductivity, high strength at elevated temperature, and low activation in a fusion nuclear environment. Currently available materials do not meet all the requirements simultaneously.
The most promising material identified thus far is the GRCop-84 alloy (Cu-8at% Cr-4at% Nb) developed for high temperature rocket nozzles. The GRCop-84 properties are excellent in all regards except for the presence of Nb, which leads to an unacceptably high waste disposal rating (WDR) following neutron irradiation. Allowable concentrations for Nb in fusion reactors are on the order of 1 wppm based on the limits reported by Fetter.
This project will make use of several newly developed techniques to generate and evaluate new alloys with high throughput. To create new alloys, we rely on two methods that generate a large number of samples in an automated manner. The first method uses a physical vapor deposition (PVD) process. The second method uses a suspension of metallic nanoparticles to fill many hemispherical wells on a substrate. After samples are created, we will use high throughput testing methods to evaluate the properties. Transient grating spectroscopy (TGS) uses two counter-propagating laser pulses to generate a shockwave in the surface of the sample. The thermo-elastic properties of the material can be inferred from the oscillation and decay of the shockwave. By taking TGS measurements at discrete points across the sample area, we can develop a 2D map of the material properties. Electrical properties will be measured by four-point conductivity measurements.
Work supported by US Department of Energy, Office of Science, Fusion Energy Sciences award DE-SC0024307.
