Effect of D on the evolution of radiation damage in W during high temperature annealing. (21st September 2020)

• Record Type: Journal Article
• Authors: Pečovnik, M.; Markelj, S.; Kelemen, M.; Schwarz-Selinger, T.
• Is Part Of: Nuclear fusion. Volume 60:Number 10(2020)
• Publication Date: 2020-09-21
• Subjects: tungsten -- deuterium retention -- displacement damage -- macroscopic rate-equations; Nuclear fusion -- Periodicals; 621.48405
• DOI: 10.1088/1741-4326/abaff6
• Languages: English
• ISSNs: 0029-5515

Abstract

Abstract: The effect of deuterium (D) on the annealing of radiation damage was studied. Tungsten (W) samples were sequentially irradiated with 20 MeV W ions at room temperature and loaded with a low-temperature D plasma at 370 K to decorate the created defects. After this, half of each sample was W irradiated at room temperature again to create additional radiation damage. To study the evolution of the created defects with D being present, samples were annealed by heating them to a desired temperature and held for 2 h. The surviving displacement damage was decorated by re-exposing the samples to the same D plasma as before. At various steps of the experiment the D depth profiles were measured using nuclear reaction analysis and after the last re-exposure a thermal desorption spectroscopy analysis was done to determine the D desorption spectra. D release is dominated by two desorption peaks centred at 520 K and 780 K for a 3 K min −1 temperature ramp. For temperature holds below 500 K no measurable change in the intensity of the desorption peaks was measured. For temperature holds above 500 K, the low temperature D desorption peak started to reduce in intensity. The high temperature D desorption peak showed signs of evolution only for temperature holds above 600 K. This behaviour was independent of the number of W irradiations used. A macroscopic rate equation model was used to recreate the experimental results. Using the fill-level dependant D-defect interaction picture we were able to determine that three distinct defect types with several fill-levels each are sufficient to describe the results. The concentrations of defect 1 (vacancies) and defect 2 (small vacancy clusters) reduced by 50% and 35%, respectively, after an 800 K temperature hold. No reduction was found for defect 3 (large vacancy clusters).