[en] Co-MgO granular films presenting TMR effects were prepared by thermo-ionic vacuum arc (TVA) method with the simultaneous ignition of plasma in Co and MgO vapors, respectively. The processing method is suitable for the simultaneous preparation of films of different relative content of Co in the MgO insulating matrix. Morphologic, structural and magnetic behaviors were analyzed in as prepared and annealed samples. The influence of the Co content on the magnetic properties of the prepared films was analyzed, in correlation with tunneling magneto-resistance effects. The tunneling magneto-resistance effect is maximal for certain Co content. This behavior was interpreted by the contrary effects of decreasing the average size of the magnetic grains, and hence the average inter-grains distance at higher Co relative content, and the enhanced magnetic disorder in very fine grains dispersed in the insulating matrix. This mechanism was suggested by the comportment of as prepared and thermally annealed samples

[en] Deuterium retention and release behavior were investigated in this study, for beryllium, tungsten and mixed beryllium/tungsten thin layers which are of concern for next-generation thermonuclear fusion devices like International Thermonuclear Experimental Reactor. The layers prepared with thermionic vacuum arc technology by using two different ion acceleration voltages 0 V and −700 V respectively were subsequently implanted by exposure to a steady-state deuterium plasma with ion energies of 240 eV/D for D₃ and 360 eV/D for D₂ at a specific fluency of 2.85 × 10²⁰ m⁻² s. Morphology is strongly influenced by layer composition and by the ion acceleration voltage applied in-situ during layer deposition. Crystalline structure analysis shows the presence of a polycrystalline W metallic phase and also highlights a dependence between tungsten crystallite size and Be/W atomic ratio. The amount of deuterium in mixed layers is lower than in pure beryllium layers indicating that W is mitigating D binding states. Results extrapolated for a ‘cold chamber and divertor scenario’ indicate a limited desorption efficiency (∼20%), if the wall baking scenario, for tritium removal procedure in ITER, is to be applied to the investigated layers. (paper)

[en] We report for the first time on the ability of Raman microscopy to give information on the structure and composition of Be related samples mimicking plasma facing materials that will be found in ITER. For that purpose, we investigate two types of material. First: Be, W, Be_1W_9, and Be_5W_5 deposits containing a few percents of D or N, and second: a Mo mirror exposed to plasma in the main JET chamber (in the framework of the first mirror test in JET with ITER-like wall). We performed atomic quantifications using ion beam analysis for the first samples. We also did atomic force microscopy. We found defect induced Raman bands in Be, Be_1W_9, and Be_5W_5 deposits. Molybdenum oxide has been identified showing an enhancement due to a resonance effect in the UV domain. (paper)

[en] Full text of publication follows: The JET main wall will be made of solid Be tiles. In order to assess the erosion rate of the thick Be wall tiles due to the plasma, an interlayer of Ni was used under a beryllium coating of a few microns. The 'marker' tiles will be placed in the areas of interest such as Outer Poloidal Limiters (OPL) and Inner Wall Guard Limiters (IWGL). The 'marker' is a Be tile with a stripe of an easily detected heavy metal (Ni) deposited on it as a thin interlayer, and with a few microns layer of the bulk-like Be on top of that. If the outer layer is eroded at the same rate as the bulk, then the erosion rate can be determined by measuring the distance of the interlayer from the final surface, for an eroded layer of a thickness that of the outer. An overview of the principles of manufacturing processes using plasma ignited in pure metal vapors by Thermionic Vacuum Arc (TVA) method [1] and the properties of the prepared coatings will be presented. The optimization of the manufacturing process (layer thickness, structure and purity) has been carried out on various substrates: glass, silicon, metals. The plasma diagnostic (the ion energy and electron temperature) during deposition and the results of the optimization process and analysis (SEM, TEM, XRD, Auger, RBS, AFM) of the coatings will be presented. Reference: [1] C. P. Lungu, I. Mustata, V. Zaroschi, A. M. Lungu, A. Anghel, P. Chiru, M. Rubel, P. Coad G. F. Matthews and JETEFDA contributors, Beryllium Coatings on Metals: Development of Process and Characterizations of Layers, Phys. Scr. T128 (2007) 157-161. (authors)

[en] JET components are removed periodically for surface analysis to assess material migration and fuel retention. This paper describes issues related to handling JET components and procedures for preparing samples for analysis; in particular a newly developed procedure for cutting beryllium tiles is presented. Consideration is also given to the hazards likely due to increased tritium inventory and material activation from 14 MeV neutrons following the planned TT and DT operations (DTE2) in 2017. Conclusions are drawn as to the feasibility of handling components from JET post DTE2. (paper)

[en] Beryllium oxide (BeO) and deuteroxide (BeO_xD_y) have been found on the melted zone of a beryllium tile extracted from the upper dump plate of JET-ILW (2011-2012 campaign). Results have been obtained using Raman microscopy, which is sensitive to both the chemical bond and crystal structure, with a micrometric lateral resolution. BeO is found with a wurtzite crystal structure. BeO_xD_y is found as three different types which are not the beta-phase but behaves as molecular species like Be(OD)₂, O(Be-D)₂ and DBeOD. The presence of a small amount of trapped D₂O is also suspected. Our results therefore strongly suggest that D trapping occurs after melting through the formation of deuteroxides. The temperature increase favors the formation of crystal BeO which favors deuterium trapping through OD bonding. (authors)