Short positron lifetime at vacancies observed in electron-irradiated tungsten: Experiments and first-principles calculations

JOURNAL OF NUCLEAR MATERIALS

卷:542

Article

Yabuuchi, A.¹  Tanaka, M.¹  Kinomura, A.¹ 

[1] Kyoto Univ, Inst Integrated Radiat & Nucl Sci, Kumatori, Osaka 5900494, Japan

关键词: Tungsten;    Electron-irradiation;    Vacancy-impurity complex;    Dissociation energy;    Positron annihilation lifetime spectroscopy;    First-principles calculation;   

DOI  :  10.1016/j.jnucmat.2020.152473

来源: Elsevier

【 摘 要 】

A positron lifetime component of similar to 170 ps has been reported for irradiated tungsten (W) in some studies. This value is considerably shorter than that calculated for isolated monovacancies (similar to 200 ps). In this study, positron annihilation lifetime spectroscopy was used to investigate the recovery behavior of the defects with a short positron lifetime of similar to 170 ps in electron-irradiated W. The binding energies and positron lifetimes of vacancy-impurity complexes decorated with impurity atoms were calculated. A positron lifetime of 169 ps, which was similar to the experimentally observed lifetime of 171 +/- 1 ps, was calculated for defect complexes comprising a monovacancy decorated with two hydrogen atoms (V-2H complexes). In addition, a value of 1.42 eV was calculated for the dissociation energy of a hydrogen atom from the V-H and V-2H complexes, and the defects with a positron lifetime of similar to 170 ps were experimentally observed to migrate at 623 K. These were consistent with previously reported dissociation energy and desorption temperature of deuterium from vacancies in W studied by thermal desorption spectroscopy. These results suggested that the vacancies observed in the electron-irradiated W were hydrogen-decorated V-nH complexes. (C) 2020 Elsevier B.V. All rights reserved.

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