Study of thermal diffusivity degradation on Cu-OFE copper due to proton and self-ion irradiation using in situ transient grating spectroscopy

Abstract

The operation of next-generation particle accelerator facilities with increased beam power parameters and emphasis on performance and reliability signifies the need for experimental studies on material property degradation. Literature is particularly scarce regarding the effects of ionizing radiation damage on cavity components at applicable radiation conditions, with even less extant work studying the effect of simultaneous irradiation on primary materials and their physical properties such as thermal transport. This study presents the impact on thermal diffusivity in oxygen-free electronic Cu-OFE specimens due to proton and self-ion ($C{u}^{3+}$) irradiation. Copper samples with the exactly same processing route as the bulk material for European Spallation Source (ESS) Radio-Frequency Quadrupole (RFQ) were characterized with scanning electron microscopy (SEM), X-ray diffraction (XRD) and electron backscatter diffraction (EBSD), followed by irradiation at room temperature with protons and self-ions ($C{u}^{3+}$) with fluences up to 4.25 × 10¹⁷ $\text{p}/{\text{cm}}^2$ and $1.10\times {10}^{15}$ $\text{ions}/{\text{cm}}^2$, $1.69\times {10}^{15}$ $\text{ions}/{\text{cm}}^2$ respectively. In situ ion irradiation transient grating spectroscopy (I³TGS) was used in order to monitor radiation-induced changes in thermal diffusivity in real time. The results indicate a significant thermal diffusivity drop only after the proton irradiation (10.86%) in contrast to the results obtained for self-ions ($C{u}^{3+}$) where no significant changes ($\sim 3\text{\%}$) are reported. The results are compared with existing literature and correlated with the nature of post-irradiation defect structures based on the particle type. In the case of protons the contribution of hydrogen implantation in stabilization of defects and on the reduction of thermal diffusivity is discussed. $I^{3}TGS$ in combination with concurrent ion irradiation offers a powerful online diagnostic tool for the evaluation of the impact of operational parameters in particle accelerator components.