Surface modification of a polycrystalline tungsten (W) mirror due to low-energy helium plasma irradiation has been studied in the compact plasma-wall interaction (PWI) simulator APSEDAS. Many fine irregularities of a few μm are generated on the W surface at Ts∼1400 K due to He bubble formation. On the other hand, a distinctive change in the surface morphology cannot be seen from the SEM micrograph on a W mirror exposed at T s<710 K. In both samples, the optical reflectivity with the incident angle θ=5° decreases more at shorter wavelength. From in situ measurement of the optical reflectivity with θ=75°, it is found that the optical reflectivity at λ∼555 nm of the low Ts exposure increased by ∼6% and decreased to the original level at a fluence of ∼3×1024 He+ m-2, and then increased again by ∼6% with the fluence up to ∼1.6×1026 He+ m-2. Calculations using a model of the multiple reflection in the modification region suggest that the thickness of the modification layer of the low Ts sample exceeds 70 nm.
|ジャーナル||Physica Scripta T|
|出版ステータス||出版済み - 2009|
|イベント||12th International Workshop on Plasma-Facing Materials and Components for Fusion Applications, PFMC-12 - Julich, ドイツ|
継続期間: 5月 11 2009 → 5月 14 2009
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