[en] Some preliminary measurements are reported on the density of helium in bubbles in metal films using optical spectroscopy in the far vacuum ultra-violet. The technique consists of measuring (by transmission through the films) the optical absorption resulting from the transition 1¹S₀ → 2¹P₁ due to the helium in the bubbles. This transition, in a rarefied gas, occurs at 584 Angstroem (21,2 eV) but because of the gas density in the bubbles is observed to be broadened and shifted to higher energy (blue shifted). The measurements imply, for specimen with high gas concentrations (0,5-3 at% He), a gas density in the bubbles greater than 10²³ atoms cm^-3. (orig.)

[en] Up to now, blister formation on rough or technical tungsten surfaces exposed to hydrogen isotope plasma was believed to be completely suppressed. The few dedicated experiments on this issue that can be found in literature appear to support that claim. Using a novel technique of 3D difference imaging of tungsten surfaces, we now demonstrate that roughness introduced by chemical etching, i.e. without the associated mechanical deformation layer introduced by grinding, only moderately reduces blistering. A technical surface with comparable roughness produced by precision grinding (R _a  ⩽  1.6 µm) led to a strong reduction in blister size and density, but blisters were found nevertheless. In this article we give a detailed description of the investigated rough W surfaces and present a statistical evaluation of blistering on these surfaces after exposure to a low-temperature deuterium plasma. (paper)

[en] Short communication

[en] Energetic particle produce ionization, dislocation loops and cavities in the surface of Zr, it may alter the structural characteristics of the material. Therefore, it is very important to investigate the hydrogen ion irradiation effects on the surface and structural properties of zirconium. The effect of hydrogen ions blisters on surface and structural properties of Zr has been investigated. Low dose of ions cause blisters on the surface of Zr. At the maximum dose, cavity/cracks formed on the surface. XRD analysis illustrates that induced stresses have been generated due to the hydrogen ions irradiation. However, new phases are not introduced in the Zr due to irradiation. The decreasing trend of crystalline size shows that the hydrogen ions diffusivity increases into the interstitial sites and causes peak broadening with the increase of radiation fluence. It is also evident that anomaly in crystalline size due to the recombination of vacancy process by increasing radiation fluence. Decrease in elastic modulus indicates the transformation of crystalline structure to partial amorphization, but there is no significant was observed in the structure of the material due to irradiation

[en] Surface morphology and deuterium retention in tungsten exposed at surface temperature of ∼550 K to mixed deuterium–neon plasmas of different neon concentrations are investigated. It is found that the addition of neon up to 20% mitigates blistering on the surface. Cross-section view of the surface shows the formation of pores near the surface in the depth less than 100 nm. Deuterium depth profile is featured by an enhanced deuterium concentration within a depth of 16 nm but a mitigated penetration in depth larger than 1 µm. Deuterium retention is reduced by up to a factor of four. It is suggested the open pores formed in the surface serves as an escaping channel, mitigates deuterium penetration towards bulk and retention in the bulk. (paper)

[en] A new concept of a beam bump for high current proton beams is presented. A beam dump prototype was built and tested with electron and proton beams up to 1.5 kW and 1 kW respectively. The tests demonstrated that the new concept satisfies the main requirements for the beam dump: acceptance of high beam intensity, low prompt and residual radiation at a few MeV beam energy and non-susceptibility to the blistering phenomenon. In addition, some diagnostic possibilities were demonstrated

[en] A new divertor concept is proposed that introduces minimal added complexity (and hence cost) to the design of a tokamak. This concept is based on the creation of a localized region of enhanced toroidal field ripple by increasing the bore size of one or more of the toroidal field coils. Plasma particles that are trapped in the enhanced-ripple region, which we call a blister, experience strong drift motions which provide a means for collecting these particles. The results of model calculations that demonstrate the feasibility of producing the required blister region and a preliminary evaluation of the divertor collection efficiency are presented. (author)

[en] The results of an experimental investigation of helium-induced blistering are presented. The goal of the research was to examine the mechanisms involved in blistering by observing the microstructure of the implanted region using transmission electron microscopy (TEM). In particular, the volume swelling was measured as a function of the implant depth, and compared to experimental skin thicknesses in order to determine if the skin separated at the maximum volume swelling, or at the end of the swelling profile

[en] Platelets of helium in molybdenum have been observed to collapse into several small helium bubbles rather than into a single bubble [10]. We show that the driving force for collapse into n bubbles increases as n decreases. However, kinetic factors associated with the nucleation of ledges on the flat faces of the platelets ensure that the frequency of nucleation of several small bubbles far exceeds that for a single bubble. The temperature at which this collapse is expected correlates well with the observed platelet behaviour. (orig.)

[en] The present work performs the investigation results on monocrystal molybdenum as model material which has been implanted at ambient temperatures by argon ions (5·10¹⁷ cm^-3) with energy 110 KeV. The post implantation annealing is carried out in two regimes: in isochronous one (1 hour) in the temperature range 200-1200 deg C and in pulsed electronic regime at the acceleration energy 140 keV, the mean current density 15 A·cm^-2, in the range of pulse duration 6-16 μ·s by step 2μs, that according to preliminary fulfilled experiments and theoretical evaluations, corresponds to the surface layer heating range in the temperature interval 950-2530 deg C. As experimental methods, the method of X-ray structural analysis using a sliding beam and the method of scanning electronic microscopy were been involved. The investigation of sample' microstructure has shown that surface roughness, caused by evaporation, is visible. The application of the pulsed annealing with the diverse duration are studied. The analysis of obtained results has enabled: to reveal the principal regularities of blisters, arising and processing to explain the two-step mechanism of their appearance, to determine their formation times, and to establish the reasons and the character of arising deformation