聚变能
复合材料
原子物理学
分流器
核工程
辐射损伤
作者
E. Bernard,Ryuichi Sakamoto,Arkadi Kreter,Marie-France Barthe,E. Autissier,Pierre Desgardin,Hiroshi Yamada,S. Garcia-Argote,Grégory Pieters,J. Chêne,Bernard Rousseau,Christian Grisolia
出处
期刊:Physica Scripta
[IOP Publishing]
日期:2017-10-05
卷期号:2017: 014023-
被引量:4
标识
DOI:10.1088/1402-4896/aa89f7
摘要
Plasma-facing materials for next generation fusion devices, like ITER and DEMO, have to withstand intense fluxes of light elements (notably helium and hydrogen isotopes). For tungsten (W), helium (He) irradiation leads to major changes in the material morphology, rising concerns about properties such as material structure conservation and hydrogen (H) retention. The impact of preceeding He irradiation conditions (temperature, flux and fluence) on H trapping were investigated on a set of W samples exposed to the linear plasma device PSI-2. Positron annihilation spectroscopy (PAS) was carried out to probe the free volume of defects created by the He exposure in the W structure at the atomic scale. In parallel, tritium (T) inventory after exposure was evaluated through T gas loading and desorption at the Saclay Tritium Lab. First, we observed that the material preparation prior to He irradiation was crucial, with a major reduction of the T trapping when W was annealed at 1773 K for 2 h compared to the as-received material. PAS study confirms the presence of He in the bubbles created in the material surface layer, whose dimensions were previously characterized by transmission electron microscopy and grazing-incidence small-angle x-ray scattering, and demonstrates that even below the minimal energy for displacement of He in W, defects are created in almost all He irradiation conditions. The T loading study highlights that increasing the He fluence leads to higher T inventory. Also, for a given fluence, increasing the He flux reduces the T trapping. The very first steps of a parametric study were set to understand the mechanisms at stake in those observed material modifications, confirming the need to pursue the study with a more complete set of surface and irradiation conditions.
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