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The use of liquid Li-Sn alloys for nuclear fusion applications may be hampered by the high melting point of Li-rich intermetallics. Aiming to inhibit their formation, the blend of pure Li (as high as 15 at.%) with pure Sn was controlled via mechanical alloying at room temperature under a dry Ar atmosphere. The depth profiling of Li down to depths near 15–20 μm was followed by nuclear reaction analysis, while elastic backscattering spectroscopy indicated the absence of O within the alloys. Elemental mapping using a nuclear microprobe evidenced the lateral spread of Li in the Sn matrix and identified Cr, Fe and Pb as the only contaminants with contents lower than 0.05 at.%. Despite the competing 2H(3He,p)4He, 6Li(3He,p)8Be, 7Li(3He,p)9Be and 7Li(3He,d)8Be nuclear reactions, retained amounts of deuterium in irradiated surfaces may be quantified with incident 3He+ ion beams in the 0.7 MeV–1.0 MeV energy range.

Tungsten-coated divertor files exposed during the third JET ITER-Like Wall (ILW) campaign in 2015-2016 (ILW-3) were studied with Secondary Ion Mass Spectrometry (SIMS). ILW-3 campaign contained more high-power plasma discharges and longer plasma time than the earlier ILW campaigns. Measurements showed increased beryllium (Be) deposition on the upper inner divertor, whereas on the outer divertor, Be deposition was lower than during the second campaign in 2013-2014 (ILW-2). Increased intensifies of nickel, molybdenum and tungsten were observed at the surface layer of the inner divertor Be dominated deposits. These layers are probably formed during the high-power plasma discharge phase near the end of the ILW-3 campaign. Compared to the earlier campaigns, D retention on the upper inner divertor was observed to on a similar level than after ILW-2, whereas at the lower inner divertor and most parts of the outer divertor, D retention was lower for ILW-3 than ILW-2. D retention was increased at lower part of outer divertor Tile 7, where Be deposition was slightly increased. Probable reason for the reduction is the higher surface temperature of the files due to higher powers used.

The plasma-facing materials in the ITER divertor area must withstand unusual events, such as the edge-localized modes (ELMS). At the point when an ELM occurs, up to 30% of the energy can be deposited on the plasma-facing boundary in the form of the heat and particle load causing material loss due to sublimation. Tungsten is a promising candidate as a plasma-facing material in the ITER divertor area since it has a high melting point, good thermal conductivity and low sputtering yield, which minimizes the plasma contamination. However their brittleness at low temperatures which is worsened by irradiation is an issue. One strategy to modulate the properties of tungsten is alloying this element with other refractory metals, such as tantalum that shows higher toughness, lower activation and higher radiation resistance. In the present study tungsten-tantalum alloys (W-Ta) were produced by Ta implantation. The fundamental mechanisms which govern the behaviour of defect dynamics in W-Ta materials under reactor conditions, were simulated by the implantation of He and D. The microstructure observations of the W plates that after single Ta implantation revealed crater-like cavities and a more severe effect after D implantation. The effect increase with the increasing of D fluence. However at fluences higher than 1021D/m the effect is reduced. In addition, blistering was observed in W-Ta plates implanted with He. The D retention in the W-Ta alloys increases with the implanted fluence with tendency for saturation for high fluences. Moreover the results show that D retention is higher after sequential He and D implantation than for single D implantation. The diffractogram of W-Ta alloys implanted with He evidenced the presence of broadened W peaks associated with stress induced by irradiation, which may cause internal stress field resulting in a distortion of the crystal lattice. These irradiation defects can be observed in the D release spectra where three peaks are associated with three types of defects in W and W-Ta implanted with He and D.

International audience; Epitaxial GaN layers with a-, c- and m-plane surface orientations were implanted with 300 keV Ar-ions at 15 K with fluences ranging from 2 × 1012 to 4 × 1016 at/cm2. Damage build-up proceeds in three steps separated by wide fluence regions where the maximum damage level, measured by in situ Rutherford Backscattering Spectrometry/Channelling, saturates. The three steps occur at similar fluences for the three crystal orientations and similar defect formation rates for the lowest fluences are observed. Surprisingly, the second saturation regime reveals a significantly lower damage level in a-plane layers while m- and c-plane samples suffer more than 4 times higher damage levels. The strong radiation resistance of a-plane GaN was attributed to very efficient dynamic annealing of point defects during the implantation even at 15 K. The migration and aggregation of point defects also lead to distinct defect microstructures as evidenced by transmission electron microscopy. Besides point defects and their clusters the dominant extended defects caused by implantation in c-plane GaN are basal stacking faults while dislocation loops are formed in a-plane material. m-plane GaN presents a mixture of planar defects and dislocation loops after implantation.

Beryllium and Tungsten have been chosen as the new “plasma facing materials” for fusion reactors. Understanding plasma wall interactions and their effects such as erosion and redeposition leading to the formation of alloys from the different materials present in the reactor chamber, is critical to model the retention of hydrogen isotopes by the wall materials. Determining the amount and the depth profile of Be and other elements deposited in the walls is a mandatory requirement in fusion reactors, making the knowledge of the relevant cross sections essential for IBA analysis. In this work we measured the 9Be(p,p0)9Be, 9Be(p,d0)8Be and 9Be(p,α0)6Li cross sections in the energy range 0.5–2.35 MeV, at an angle of 150°.

Selected Ion Beam Analysis techniques applicable for detecting deuterium and heavier impurities have been used in the post-mortem analyses of tiles removed after the first JET ITER-Like Wall (JET-ILW) campaign. Over half of the retained fuel was measured in the divertor region. The highest figures for fuel retention were obtained from regions with the thickest deposited layers, i.e. in the inner divertor on top of tile 1 and on the High Field Gap Closure tile, which resides deep in the plasma scrape-off layer. Least retention was found in the main chamber high erosion regions, i.e. in the mid-plane of Inner Wall Guard Limiter. The fuel retention values found typically varied with deposition layer thicknesses. The reported retention values support the observed decrease in fuel retention obtained with gas balance experiments of JET-ILW.

The 9 Be( 3 He, p i ) 11 B cross sections for i = 0,1,2,3 at an angle of 135° in the energy range 1–2.5 MeV have been measured using two thin films with different Be thickness at selected energies. The new data extend previous results, that only existed at 90°, 120° and 150° angles, and down to 1.8 MeV, which prevented use of this reaction for samples containing Be at larger depths.

Energetic He + and D + ions were implanted into different W–Ta composites in order to investigate their stability under helium and deuterium irradiation. The results were compared with morphological and chemical modifications arising from exposure of pure W and Ta. Special attention was given to tantalum hydride (Ta 2 H) formation due to its implications for tritium inventory. Three W–Ta composites with 10 and 20 at.% Ta were prepared from elemental W powder and Ta fibre or powder through low-energy ball milling in argon atmosphere. Spark plasma sintering (SPS) was used as the consolidation process in the temperature range from 1473 to 1873 K. The results obtained from pure elemental samples and composites are similar. However, Ta 2 H is easily formed in pure Ta by using a pre-implantation stage of He + , whereas in W–Ta composites the same reaction is clearly reduced, and it can be inhibited by controlling the sintering temperature.

Ar ion implanted GaN and ZnO are studied at 295 K by Rutherford backscattering spectrometry in channelling configuration. Under these conditions in both materials damage formation proceeds in four steps which are characterised by the accumulation of point defects (I), a first saturation of the relative damage concentration at a value well below 10% (II), a second increase of the damage concentration (III) and a second plateau at about 60% for GaN and 40% for ZnO (IV). The results obtained here are compared to those reported previously for Ar ion implantation into these materials performed at 15 K. The main result of our studies is that damage formation is nearly the same for implantation at 295 K and 15 K. This suggests that thermally enhanced defect diffusion is not the main driving force during ion implantation of these materials. The shape of the channelling spectra observed in stages III and IV suggests the existence of both a high concentration of defect clusters and extended defects. The latter are proven to exist after implantation at 295 K. Therefore, there are arguments to conclude that extended defects form already during implantation at 15 K.

Silicon carbide doped with magnetic ions such as Fe, Mn, Ni or Co could make this wide band gap semiconductor part of the diluted magnetic semiconductor family. In this study, we report the implantation of 6H-SiC single crystals with magnetic $^{56}$Fe$^{+}$ ions with an energy of 150 keV. The samples were implanted with 5E14 Fe$^+$/cm$^{2}$ and 1E16 Fe$^+$/cm$^{2}$ at different temperatures to study the damage formation and lattice site location. The samples were subsequently annealed up to 1500°C in vacuum in order to remove the implantation damage. The effect of the annealing was followed by Rutherford Backscattering/Channeling (RBS/C) measurements. The results show that samples implanted above the critical amorphization temperature reveal a high fraction of Fe incorporated into regular sites along the [0001] axis. After the annealing at 1000°C, a maximum fraction of 75%, corresponding to a total of 3.8E14 Fe$^{+}$/cm$^{2}$, was measured in regular sites along the [0001] axis. A comparison is made between the observed annealing behavior and the one measured in low fluence (2E13 cm$^{−2}$) $\beta$- emission channeling experiments using the radioactive isotope $^{59}$Fe (t$_{1/2}$ = 45 d), where the sample was implanted at room temperature and the $\beta$- emission channeling yield was measured by means of a position-sensitive detector.