Real-time vacancy concentration evolution revealed via heavy ion irradiation experiments

Abstract

We show that in situ ion irradiation transient grating spectroscopy (I3TGS) can be used to monitor the real-time evolution of vacancy concentration generated by self-ion radiation damage in Cu-based alloys. Surface acoustic wave (SAW) frequencies are shown, using a combination of theory and experiment, to reveal vacancy concentrations and their kinetics in real-time. These results are shown to agree with corresponding kinetic Monte Carlo simulations at similar temperatures and dose rates. These results suggest the utility of TGS as a non-contact, non-destructive tool for real-time defect monitoring.

Figures (14)

• Figure 1: Scheme of TGS coupled with in situ irradiation. Adapted from hofmann_transient_2019.
• Figure 2: Irradiation depth profile as calculated by SRIM and nominal TGS e-folding depth sensitivity for thermal and acoustic wave properties.
• Figure 3: in situ TGS results from 7 MeV Cu$^{3+}$ irradiation at 23.3 mW (a) and from 1.63 MeV proton irradiation (b). Most crucially, these two results show that two experiments with the same beam heating power in Watts produce changes in SAW frequency proportional to their ion stopping powers, and not to beam heating temperature. This isolates the effect of beam heating from vacancy concentration on the changes in SAW frequency and thermal diffusivity. c) 0.2% offset Yield Strength model for GRCop-84 from ellis_aerospace_2001, showing that a 0.4% change in elastic properties would imply an increase in temperature of $140^\circ C$. d) Infrared camera calibration and temperature measurement for different isotopes of copper at 1.68MV terminal potential. This plot shows that the maximum increase in temperature for $Cu^{2+}$ is $13^\circ C$, and just around $1.5^\circ C$ for 15 nA of $Cu^{3+}$ (current conditions used in plots a) and b).
• Figure 4: Periodic pulsed beam experiment, showing how SAW frequency evolves as the Cu-ion beam is cycled on and off. The white background and orange dots represent the periods in which the beam is on, and the grey background and blue dots represent the periods in which the beam is off.
• Figure 5: Vacancy concentration evolution with increasing dose for a periodic pulsed beam experiment. The initial large increase represents the change from only thermal point defects (here we deem this to be negligible) to a high concentration, while the increases at all subsequent doses are much smaller as the proliferation of radiation defects from initial irradiation quickly reduces later vacancy concentrations.