V. S. Kulikauskas

Application of the particle backscattering methods for the study of new oxide protective coatings at the surface of Al and Mg alloys

Abstract Rutherford (1.5 MeV 4He+) and Nuclear (7.7 MeV H+) Backscattering Spectrometry were used for investigation of oxide protective coatings on the surface of Al and Mg alloys obtained by microarc oxidation (MAO). A model of microarc coating formation is proposed. For Mg alloy, the structure of MAO coating with very high corrosion resistance was determined.

Angular distributions of Ni and Ti atoms sputtered from a NiTi alloy under He+ and Ar+ ion bombardment

Abstract The angular distributions of sputtered components were measured for NiTi polycrystalline alloy under 9 keV Ar + and He + ions bombardments with various fluences in ultrahigh vacuum. Combination of Rutherford Backscattering Spectrometry (RBS) and Auger Electron Spectrometry (AES) techniques allowed us to observe enhanced concentration of Ni over a layer with thickness comparable to a primary He + ions penetration depth due to selective sputtering of Ti atoms and radiation-induced diffusion processes. A preferential emission of Ni atoms towards the surface normal was observed during bombardment by both He + and Ar + ions. More forward-peaked “over-cosine” angular distributions of sputtered Ni in comparison with those for Ti atoms have been measured. Nonstoichiometric sputtering of NiTi alloy dependent on emission angle was observed for bombardment fluence of He + well below that needed for the steady-state altered layer formation. To explain the peculiarities of NiTi sputtering, an interpretation is discussed in terms of sputtering due to backscattered He + ions.

Peculiarity of deuterium ions interaction with tungsten surface in the condition Imitating combination of normal operation with plasma disruption in ITER

Tungsten is a candidate material for the ITER divertor. For the simulation of ITER normal operation conditions in combination with plasma disruptions samples of various types of tungsten were exposed to both steady-state and high power pulsed deuterium plasmas. Tungsten samples were first exposed in a steady-state plasma with an ion current density 10 21 m -2 s -1 up to a dose of 10 25 m - 2 at a temperature of 770 K. The energy of deuterium ions was 150 eV. The additional exposure of the samples to 10 pulses of deuterium plasma was performed in the electrodynamical plasma accelerator with an energy flux 0.45 MJ/m 2 per pulse. Samples of four types of tungsten (W-1%La 2 O 3 , W-131. monocrystalline W(1 1 1) and W-10%Re) were investigated. The least destruction of the surface was observed for W(1 1 1). The concentration of retained deuterium in tungsten decreased from 2.5 x 10 19 m - 2 to 1.07 × 10 19 m -2 (for W(1 1 1)) as a result of the additional pulsed plasma irradiation. Investigation of the tungsten erosion products after the high power pulsed plasma shots was also carried out.

On carbon nitride synthesis at high-dose ion implantation

Abstract Rutherford backscattering spectrometry was used for the study of high dose 35 keV nitrogen ions implantation into graphites and glassy carbon. Quantitative data on depth profiles and its dependencies on irradiation fluence and ion beam density were obtained. The stationary dome-shaped depth profile with maximum nitrogen concentration 22–27 at.% and half-width more than twice exceeding projected range of ions is reached at fluence Φ ∼10 18 cm −2 . The dependence of the maximum concentration in the profile on ion current density was studied. The largest concentration was obtained at reduced ion current density.

Deuterium accumulation in beryllium in contact with atomic deuterium at 740 K

The interaction of deuterium atoms with type TIP-30 beryllium has been studied. A plasma source with a heated cathode was used to produce deuterium atoms. The sample was under positive potential of +80 V to repulse the deuterium ions. The atomic flux was estimated at 1016 cm−2 s−1. After exposures to different doses at 740 K, the deuterium distribution and inventory in the samples were measured by means of elastic recoil detection (ERD) and thermal desorption spectroscopy (TDS) methods. The experiments showed that when in contact with atomic deuterium, beryllium absorbs deuterium up to concentrations of (6–8) × 1021 D/cm3. Deuterium penetrates deeply into the beryllium bulk. The penetration depth depends on the exposure time and reaches 400 nm after 240 min exposure. The main features of deuterium accumulation in beryllium during the atom exposure are very similar to those during the deuterium ion implantation, and this points out the similarity of the mechanisms of deuterium spread into beryllium, perhaps through the formation of the bubbles.

Plasma impact on materials damaged by high-energy ions

We present a short review of experimental research carried out at the NRC Kurchatov Institute over recent years on the behavior of plasma-facing materials (PFMs) when a high level of radiation damage in plasma. Neutron-induced damage was modeled with accelerated ions (in the MeV range) and covered a 1–80 dpa interval. Irradiated carbon materials and tungsten were exposed to deuterium steady-state plasma at deuterium ion energies of 100–250 eV. The work focused on the damaging effect on erosion and on deuterium retention in irradiated materials. The influence of displacement damage was found on the erosion of carbon materials after their bombardment with C+ ions. Changes in deuterium retention were observed on tungsten damaged by 3–4 MeV helium ions. The experiments and results show the efficiency of the method for investigating plasma influence on PFMs for fusion applications taking into account the effect of accumulated radiation damage.

Plasma-driven superpermeation of hydrogen through Nb membranes: bulk effects

A non-monotonic temperature dependence of the steady-state plasma-driven superpermeation of hydrogen through an Nb membrane is observed for the first time. Such a permeation behavior is related not only to the surface properties of the membrane, but also to its bulk properties and defects.

Angular distributions of particles sputtered from polycrystalline platinum

Abstract The angular distributions of sputtered particles for 3–10 keV argon-ion bombardment of polycrystalline platinum at normal incidence have been investigated both experimentally and by computer simulation using the program TRIM.SP. Two types of targets were used. One is a fine-grained Pt polycrystal, the other is rolled sheet Pt. The angular distributions were measured applying RBS of the material deposited on a collector. For fine-grained platinum the angular distributions are cupola shaped and slightly overcosine. For rolled platinum the distributions are much more overcosine with a strong central Wehner spot due to the texture caused by rolling. Results from computer simulation show that the effect of the surface binding energy on the shape of the angular distribution is negligible. The dependence of the shape of the angular distribution on the ion energy interval from 3.5 to 10 keV was also found to be very weak. Good agreement has been found between the experimental and computed results for fine-grained platinum.

Investigation of the beryllium ion-surface interaction

Abstract The energy and temperature dependence of self-sputtering yields of beryllium were measured. The energy dependence of the beryllium self-sputtering yield agrees well with that calculated by Eckstein et al. Below 770 K the self-sputtering yields are temperature independent; at T irr. > 870 K the yield increases steeply. Beryllium samples were implanted at 370 K with monoenergetic 5 keV hydrogen ions and with a stationary hydrogen plasma power flux of about 5 MW/m 2 . In the fluence range of 5 × 10 22 -1.5 × 10 25 m −2 the depth profile is shifted towards the surface with increasing fluence and the concentration of trapped hydrogen atoms is reduced from 3.3 × 10 21 to 7.4 × 10 20 m −2 . About 95% of the trapped hydrogen is located within bubbles and only ∼ 5% is trapped as atoms. With increasing implantation fluence the bubbles coalesce, producing channels through which hydrogen escapes.

Nanoparticle process formation in zinc implanted silicon with followed thermal annealing

Results of temperature treatment effect on near surface layer properties of Zn ion implanted Si substrate are presented. Radiation induced point defects and Zn in depth profile was studied by Rutherford back scattering (RBS) method with use of channeling technique. Topology of substrate surface was studied by atomic force microscopy (AFM) and scaning electron microscope (SEM). Phase composition of samples was test by x-ray diffraction in grazing geometry.