[en] Angular distributions of the small-angle critical scattering of 1.25 Å neutrons in cobalt have been measured at temperatures up to 150°C above the Curie point for a large range of scattering vectors (k = 0.03 - 0.6 Å^-1). The experimental data show that the asymptotic form of the instantaneous spin pair correlation function at large distances is that predicted by Fisher. The temperature dependence of the interaction range inferred from experimental data by using the Fisher correlation function is in agreement with theoretical predictions. The exponents of the temperature dependences of the reduced magnetic susceptibility and correlation range are found to be smaller in cobalt than in iron. The critical scattering data are in agreement with classical susceptibility measurements. The angular distributions at relatively large values of the scattering vector show the limited validity of the asymptotic spin correlation function. The variation with k of the position of the maximum scattered intensity as a function of temperature is discussed. (author)

[en] Carbon and tungsten films were deposited sequentially and simultaneously from two separate plasmas produced by the thermionic vacuum arc (TVA) method. Total film thickness and atomic concentration of C and W were measured for different substrate positions and arc parameters and a comparison between sequential and simultaneous deposition of carbon and tungsten is presented. For the simultaneous case, while keeping the same discharge parameters as in the sequential case, the carbon composition percentage is enhanced despite the presence of the tungsten plasma. When only the carbon deposition rate is increased 10 times, the tungsten atomic concentration drops to a lower level, while the content of carbon becomes dominant for the substrates positioned near the carbon anode.

No abstract available

[en] We generated relaxation discharges in different gases using both dc and ac (50 Hz) supplying sources. We followed spectroscopically the plasma behavior in dc discharges, ac discharges and combinations of these discharges with relaxation ones in dichlorodifluoromethane and carbon tetrafluoride gases, mostly used in plasma etching technologies at pressures of around 0.1 torr

No abstract available

[en] Low friction coating materials are new classes of advanced materials, which exhibit a reduced coefficient of friction in dry sliding and raised wear resistance. Due to demand of high power and high-speed automotive engines, the engine moving parts have to be improved in tribological characteristics. Three copper-alloy layers with 15 - 20 μm overlay are widely in use for plain bearing fabrication. The overlay that provides seizure and wear resistance and conformability is usually made by electroplating of 10 - 30 μm thick lead alloy including In, Sn and Cu. The lead matrix is soft and has relatively low fatigue resistance under high-pressure conditions. New materials and new deposition procedures are needed to improve tribological and mechanical characteristics of the overlay. The purpose of this study is to produce low friction coatings to be used as overlays for automobile plain bearings and to realize depositions with high rate by using thermal plasma jet. We previously reported the formation of silver/graphite overlays by plasma sputtering and spray coating of alumina mono-layer with a new type of the reactor based on the forced constricted type plasma jet generator. In this paper, we study further the composite coatings of Ag and graphite by using the new-type spray gun (i.e. the plasma electrode type spray gun). A plot is given showing the reduction of the coefficient of friction of the Ag/graphite overlay at about 20% compared to that of the bronze substrate measured using a CSEM ball-on-disc tribometer in dry sliding (air, 50% humidity). (authors)

[en] Beryllium is a candidate plasma-facing material for the main chamber wall in ITER. It will also be at JET during the ITER-Like Wall (Il) Project aiming at tokamak operation with a full metal wall. Special marker tiles will be used in order to assess the beryllium erosion. These will be solid beryllium tiles coated first with a thin high-Z metal film (acting as an interlayer) and then with a layer of deposited beryllium. The aim of this contribution is to report on the development of a production method for thin beryllium coatings relevant for this application. (authors)

[en] Full text of publication follows: The Joint European Torus (JET) is a large experimental nuclear fusion device. Its aim is to confine and study the behaviour of plasma in conditions and dimensions approaching those required for a fusion reactor. The plasma is created in the toroidal shaped vacuum vessel of the machine in which it is confined by magnetic fields. In preparation for ITER a new ITER-like Wall (ILW) will be installed on Joint European Torus (JET), a wall not having any carbon facing the plasma [1]. In places Inconel tiles are to be installed, these tiles shall be coated with Beryllium. MEdC represented by the National Institute for Laser, Plasma and Radiation Physics, Magurele, Bucharest and in direct cooperation with Nuclear Fuel Plant Pitesti started to coat Inconel tiles with 8 μm of Beryllium in accordance with the requirements of technical specification and fit for installation in the JET machine. This contribution provides an overview of the principles of manufacturing processes using thermal evaporation method in vacuum and the properties of the prepared coatings. The optimization of the manufacturing process (layer thickness, structure and purity) has been carried out on Inconel substrates (polished and sand blasted) The results of the optimization process and analysis (SEM, TEM, XRD, Auger, RBS, AFM) of the coatings will be presented. Reference [1] Takeshi Hirai, H. Maier, M. Rubel, Ph. Mertens, R. Neu, O. Neubauer, E. Gauthier, J. Likonen, C. Lungu, G. Maddaluno, G. F. Matthews, R. Mitteau, G. Piazza, V. Philipps, B. Riccardi, C. Ruset, I. Uytdenhouwen, R and D on full tungsten divertor and beryllium wall for JET TIER-like Wall Project, 24. Symposium on Fusion Technology - 11-15 September 2006 -Warsaw, Poland. (authors)

[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)