Thermal evolution of helium bubbles in tungsten by GISAXS and TDS

• Published in: Journal of nuclear materials 2025-01, Vol.604, p.155524, Article 155524
• Main Authors: Teo, Soon Han Bryan, Thompson, Matt Andrew Trevor, Kirby, Nigel, Hughes, Danielle Rose, Hammoud, Nour, Khan, Aneeqa, Tanaka, Hirohiko, Ohno, Noriyasu, Mummery, Paul, Harmer, Sarah Louise, Corr, Cormac Seamus
• Format: Article
• Language: English
• Subjects: Annealing; GISAXS; Helium bubbles; Plasma-material interactions; TDS; Tungsten
• ISSN: 0022-3115
• DOI: 10.1016/j.jnucmat.2024.155524

Grazing-incidence small-angle x-ray scattering (GISAXS) and thermal desorption spectroscopy (TDS) were used to study the thermal evolution of helium (He) bubbles in tungsten (W). W samples were exposed to a low ion energy (∼20 eV, sheath accelerated) He plasma at two sample temperatures: 573 K (low-temperature) and 1050 K (high-temperature). They were then annealed to temperatures of 773 K, 873 K and 998 K. GISAXS analysis showed an increase in the median bubble radius of the high-temperature samples from 6.42 Å to 12.87 Å as a result of annealing to 998 K. No changes in the bubble radii distributions were observed for the low-temperature samples and the median radius remained at ∼4 Å even after annealing. TDS showed that the desorption behaviour of He in W has a dependence on the sample temperature during plasma irradiation. The higher-temperature sample experienced a maximum desorption rate that is an order of magnitude larger than the low-temperature sample. The desorption profile of the high-temperature sample spanned a wider temperature range, 500 K - 1500 K, than the low-temperature sample, 500 K - 750 K. The formation and thermal evolution of He bubbles in W have a clear dependence on sample temperature during plasma exposure. The differences in annealing behaviour observed in this work agree with prior in-situ TEM annealing experiments and help explain macroscopic plasma-material interaction effects such as recrystallisation suppression. •Annealing causes growth in He bubbles in W exposed to plasma at 1050 K.•No growth in He bubbles after annealing W exposed to He plasma at 573 K.•He desorption by annealing is higher in W exposed at 1050 K than at 573 K.•He desorption in W exposed to 1050 K is a symptom of the bubble growth mechanism.•GISAXS trends agree with prior in-situ TEM annealing experiments.