Speaker
Description
The ability to quantify irradiation damage and recovery of thermal transport and elastic response in tungsten is essential for understanding and accurately predicting stress evolution, heat management, and even failure modes in fusion plasma-facing components. Transient grating spectroscopy (TGS) non-destructively quantifies material properties in the first few microns [1]. Whereas previous TGS works on tungsten (W) [2-4] have focused on thermal diffusivity (α) alone, this work also determined Poisson’s ratio (𝝂) and Young’s modulus (Ε). In addition to the surface acoustic wave (SAW) typically reported, another higher frequency peak is clearly discerned in the Fourier spectra of the TGS signal. TGS measurements on both Si and W confirm this frequency is due to a surface skimming longitudinal wave, constraining the analytical SAW equations and allowing both 𝝂 and Ε to be extracted.
Polycrystalline W (PCW) and single-crystal W (SCW) samples were partially masked during self-damage to preserve a pristine region, used for normalizing results. PCW samples were self-damaged with W ions at 20 MeV, while the SCW samples were self-damaged with 11 MeV ions. To study recovery, a 0.020 dpa SCW sample was annealed in 100 C increments. X-ray diffuse scattering quantified dislocation loop size and concentration in the SCW samples. TGS measurements were performed ex-situ with varied penetration depths from ~0.6 to 1.9 μm to probe within and beyond the induced-defect region.
Thermal diffusivity was found to decrease for all self-ion damaged samples. Previously reported 𝝂 and Ε values for neutron or self-ion irradiated W at elevated temperatures resulted in no change within the uncertainty of the impulse excitation technique or cantilever measurements [5-6]. For self-ion damage performed at room temperature, we measured a reduction in Ε of ~0.8, 1.4, and 2.0% for 0.008 dpa SCW, 0.020 dpa SCW, and 0.23 dpa PCW, respectively. Annealing the 0.020 dpa SCW sample showed partial recovery of α and E. All samples measured showed 𝝂 remained effectively unchanged within the measurement uncertainty, well below 1%. Additional results for higher dpa PCW samples will also be presented.
Work is supported by US-DOE-FES No. DE-SC0022528.
[1] Käding et al., Applied Physics A 61 (1995) 253–261
[2] F. Hoffmann et al., Sci. Rep. 5 (2015) 1-7
[3] Dennett et al., Appl. Phys. Lett. 110 (2017) 211106
[4] Reza et al., Acta Mater. 232 (2022) 117926
[5] Dellis et al., J. Nucl. Mater. 551 (2021) 152985
[6] Gibson et al., Phys. Scr. T159 (2014) 014056