Ultra-Rapid, Physics-Based Development Pathway for Reactor-Relevant RF Antenna Materials

Abstract

This article presents a rapid, atomistically informed, experimental development pathway for fusion reactor-relevant radio-frequency (RF) antenna materials in the Cu-Cr-(Nb,Al,Zr) composition system, with the goal of improving upon GRCop-84. RF antennas in a tokamak fusion reactor will face a unique set of challenges as both structural and functional materials. The desired material must simultaneously achieve and maintain high electrical conductivity, high strength, high thermal conductivity, resist high temperatures, possess low nuclear activation, and incur low damage due to neutron bombardment. The GRCop-84 alloy serves as a starting point for iterative improvement, with the desire to reduce or eliminate Nb from the material to minimize nuclear activation. The rapid development pathway makes use of a multi-target combinatorial thick-film sputtering process to produce full ternary phase diagrams on a Si wafer substrate. Transient grating spectroscopy (TGS), a laser-ultrasonic method, will determine spatially varying thermoelastic properties, while four terminal electrical conductivity measurements will map out the best performing regions of the sample for in-depth study at larger length scales. High-energy proton and self-ion irradiation emulates the effects of neutron damage on the thermal/electric properties. With rapid turnaround time (~days) in terms of mapping radiation damage-induced material property changes in the full ternary system, these techniques allow rapid iteration toward an optimal material, testing hundreds of nearby compositions in the time it took to test one. Focused testing of larger, single composition samples (produced in an arc furnace or by laser sintering) provides data on structural and high-power RF properties and validates our thick-film-based workflow.