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Highlights: [•] W samples were pre-irradiated with 4.8 and 20MeV W ions to various displacements per atom (dpa). [•] Under following exposure to D plasmas radiation-induced defects were occupied by diffusing D atoms. [•] At ⩾0.1dpa, the D concentration in the damage zone demonstrated weak dependence on the damage level. [ABSTRACT FROM AUTHOR]

Abstract: Samples prepared from polycrystalline ITER-grade tungsten were damaged by irradiation with 20MeVW ions at room temperature to a fluence of 1.4×1018 W/m2. Due to the irradiation, displacement damage peaked near the end-of-range, 1.35μm beneath the surface, at 0.89 displacements per atom. The damaged as well as undamaged W samples were then exposed to low-energy, high-flux (1022 D/m2 s) pure D and helium-seeded D plasmas to an ion fluence of 3×1026 D/m2 at various temperatures. Trapping of deuterium was examined by the D(3He,p)4He nuclear reaction at 3He energies varied from 0.69 to 4.0MeV allowing determination of the D concentration at depths up to 6μm. It has been found that (i) addition of 10% helium ions into the D plasma at exposure temperatures of 440–650K significantly reduces the D concentration at depths of 0.5–6μm compared to that for the pure plasma exposure; (ii) generation of the W-ion-induced displacement damage significantly increases the D concentration at depths up to 2μm (i.e., in the damage zone) under subsequent exposures to both pure D and D–He plasmas. [Copyright &y& Elsevier]

Abstract: Depth profiles of deuterium trapped in single crystal Mo, polycrystalline Mo, and molybdenum trioxide film on polycrystalline Mo irradiated with 200eV D ions have been measured up to a depth of 8μm using the D(3He,p)4He nuclear reaction at a 3He energy varied from 0.69 to 4.0MeV. For the D ion irradiation at 323K to the highest ion fluence of 5×1024 D/m2, the D concentration decreases from several at.% in the near-surface layer to bulk values below 10−4 at.% for single crystal Mo and about 10−2 at.% for polycrystalline Mo. The maximum D concentration in molybdenum trioxide film differs little in value from that for polycrystalline Mo. Blister formation at high fluences is observed for polycrystalline Mo and molybdenum trioxide film, but not for single crystal Mo. As the irradiation temperature increases from 323 to 493K, the D retention in the polycrystalline Mo decreases from about 3×1021 down to about 2×1018 D/m2. [Copyright &y& Elsevier]

Abstract: Plasma-facing carbon fibre composites (CFC) are used for Tore Supra (CFC N11), ASDEX Upgrade (CFC DMS 701) and foreseen for ITER (CFC NB31). Therefore, deuterium retention in the CFC NB31 and N11 was studied by irradiation with 30–200eV D ions, both from ion beams and plasma devices (PISCES-A, Magnetron plasma device), using methods of the thermal desorption spectrometry and D(3He,p)4He nuclear reaction in a resonance-like technique. It is found that at each irradiation temperatures in the range from 50 to 450°C the amount of deuterium trapped in the CFCs increases with the ion fluence, Γ. No saturation is reached as observed in pyrolytic graphite. At room temperature the retention at high fluence increases proportional to Γ 0.5. Depth profiles show that saturation occurs only within a near-surface layer corresponding to the ion range. The increase in total retention is accompanied by an increasing long profile tail extending beyond 14μm with the D concentration above 10−1 at.% at fluences above 1024 D/m2. Analysis of CFC and fine-grain graphite tiles removed from identical strike-point positions in the outer ASDEX Upgrade divertor show an order of magnitude higher retention in the CFC and profiles extending into the bulk with concentrations of 0.1at.% well beyond the measurable depth of 14μm. [Copyright &y& Elsevier]

Fe–W binary mixed layers were prepared as a model system for reduced-activation ferritic–martensitic (RAFM) steel for studying their dynamic erosion behavior resulting from energetic deuterium (D) irradiation. This investigation aims toward an assessment of RAFM steels as plasma-facing material. The surface composition of the model layers is modified by D irradiation. W is enriched at the surface with D irradiation fluence due to the preferential sputtering of Fe. It depends on the D impinging energy as well as the initial W fraction of the Fe–W layer. No significant development of surface topography was observed within the examined conditions. The erosion yield of a Fe–W layer is comparable to that of pure Fe in the low-fluence range and decreases with increasing D fluence. These results indicate that the dynamic change of erosion yield is significantly correlated with the surface W enrichment. [ABSTRACT FROM AUTHOR]