Тhe results of an experimental study of tungsten as a coating material for the divertor and the first wall of a thermonuclear tokamak reactor are presented. A method for modeling radiation damage of a material by thermonuclear neutrons based on the use of accelerated protons has been developed. A technique for irradiating tungsten samples (PLANSEE) with protons is developed at the cyclotron of the National Research Center Kurchatov Institute. During irradiation, protons with an energy of 3.7 MeV and the total fluence of 10 18 protons/cm 2 are used. The samples irradiated (0.05 dpa) are studied in deuterium plasma on the LENTA device. The results of irradiation and plasma exposure on the surface and the accumulation of deuterium in the irradiated material are presented.

Results of the complex experimental research of plasma impact on fusion reactor materials are presented. The near-wall plasma of a tokamak reactor is simulated on the linear plasma device LENTA (National Research Center Kurchatov Institute). Plasma fluence of 10 22 –10 23 cm –2 to the material surface is provided at 10 12 –10 13 cm –3 of plasma density in steady-state operation of the device, thus simulating the continuous regime of the fusion reactor plasma-wall conditions. The neutron effect on the first wall material (radiation damage) is also simulated by irradiation with high-energy ions accelerated by a cyclotron to MeV-range energies. The work is centered mainly on tungsten being a candidate for coating of the divertor region in the tokamak reactor. Samples irradiated at doses of 10 21 –10 23 ion/cm 2 to a high damage level from 0.1 to 80–100 displacements per atom characteristic of a durable operation of the reactor have been obtained on the cyclotron at the National Research Center Kurchatov Institute. Helium, carbon, and nitrogen ions and protons whose defect generation mechanisms are very different have been used in irradiations. Erosion data (erosion rate, erosion yield), swelling characteristics (profilometry), and microstructure changes (SEM) of the damaged surface layer are given for tungsten preirradiated with fast nitrogen ions. Proton-irradiated silicon carbide SiC has also been studied in deuterium plasma, and changes in its microstructure are found.

The effect of deuterium plasma on tungsten with high levels of radiation damage was studied experimentally. Tungsten was examined as a candidate plasma-facing material for a fusion reactor. The effect of damage accumulation in a material irradiated with fusion neutrons was simulated using high-energy ions. Primary radiation defects of 1–100 dpa were produced in tungsten irradiated with He2+ and C3+ ions accelerated to 3–10 MeV in the cyclotron at the Kurchatov Institute with a fluence of 1017–1019 ion/cm2. The irradiated material was exposed to deuterium plasma at the LENTA linear plasma facility operated in the continuous regime and providing a plasma flux of 1021–1022 D/cm2. The erosion dynamics, the development of surface microstructure, and the accumulation of deuterium in tungsten were studied. Enhanced retention of deuterium was observed in the samples damaged both by helium and carbon ions at room temperature (ERDA). The effect of deuterium retention was suppressed in the damaged tungsten samples processed at a temperature of 500°C.

The paper presents the development of experimental investigations and recent results of the impact on tungsten at high level of radiation damage under steady-state deuterium plasma. Tungsten is considered as a plasma facing material for a fusion reactor. The effect of fusion neutron impact is simulated by surrogate irradiations with high-energy ions. The primary defects at 1-100 dpa were produced in tungsten samples by He and C ions accelerated in the Kurchatov cyclotron to 3-10 MeV at the total fluence of 1017-1019 cm-2. The irradiated material was studied in deuterium plasma on the LENTA linear divertor simulator at the plasma fluence 1021-1022 D/cm2. Erosion dynamics, development of the surface microstructure and deuterium retention were analyzed. Increased deuterium retention detected previously in tungsten pre-irradiated by He ions was also registered (ERDA) on C-irradiated samples at 2-3 dpa. In contrast, a significant decrease in the D uptake has been observed on those samples operated in the experiments at 500°C.

Effect of radiation damage on tungsten response to plasma exposure is examined. Samples of tungsten W 99.95wt% were irradiated with fast 12C3+ ions at 10MeV to fluence of (1–2)×1017ion/cm2 to produce damage in the range 1–40dpa relevant to the level of interest for fusion research. Exposure of the irradiated tungsten to deuterium plasma on linear simulator in erosion condition provided D-ion total fluence (1–3)×1021D+/cm2 at ion energy 250eV. Swelling effect has been observed, and important changes in the structure of the irradiated material have been found (SEM). Erosion of the damaged layer was evaluated at Yd-w≅(3–5)⋅10−3at/ion. The retained deuterium profiles have been taken by ERDA, maximal deuterium concentration reached 6–8at.% in the layer ∼30nm deep corresponding to 2–3dpa. Comparison of D-retention was made for C- and He-irradiated tungsten for this level of damage.

The effects occurring on the surface of tungsten under irradiation with fast ions with an energy in the megaelectrolvolt range and with high fluxes of hydrogen (deuterium) plasma are considered. These effects are radiation damage of the surface layer of the material, its erosion and deuterium retention in it. Irradiation with helium 4He2+ (3.2–4.0 MeV) and carbon 12C3+ (10 MeV) ions is performed using a cyclotron at the National Research Center Kurchatov Institute. The thickness of the damaged layer is 3.5–6 μm. The irradiated samples are exposed to steady-state deuterium plasma using a LENTA linear plasma facility to reach a plasma ion fluence of 1021–1022 cm−2. Tungsten erosion and modification of the structure of the damaged layer are analyzed at a plasma-ion energy of 250 eV. Deuterium retention in the damaged layer is studied by elastic recoil detection analysis. The deuterium concentration and its penetration depth into the material are measured. The data obtained for different kinds of fast ions used in the work are compared.

A new method for creating nanostructures in a plasma focus discharge is proposed. It is shown that the material of a micron-size dust target produced at the discharge axis efficiently evaporates and is then involved in the pinching process. After the pinch decays, the plasma expands with the thermal velocity and the evaporated dust material is deposited on the collectors in the form of fractal particles or nanoclusters organized into various structures. Such structures have a well-developed surface, which is important for various technological applications.

Experimental study aimed at investigation of neutron induced damage influence on fusion reactor plasma facing materials is reported. Displacement damage was produced in tungsten by high-energy helium and carbon ions at 3–10MeV. The reached level of displacement damage ranged from several dpa to 600dpa. The properties of the irradiated tungsten were studied in steady-state deuterium plasma on the LENTA linear divertor simulator. Plasma exposures were made at 250eV of ion energy to fluence 1021–1022ion/сm2. Erosion dynamics of the damaged layer and deuterium retention were observed. Surface microstructure modifications and important damage of the 5μm layer shown. Deuterium retention in helium-damaged tungsten (ERD) showed its complex behavior (increase or decrease) depending on implanted helium quantity and the structure of the surface layer.

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.

Experimental study of tungsten at high level of displacement damage is reported. The damage of 1–80dpa was produced by high-energy helium ions 4He2+ (3–4MeV) from cyclotron. Properties of the irradiated tungsten were studied in deuterium plasma on the LENTA linear divertor simulator. Plasma exposures were made at 250eV of ion energy to reach fluence 1025–1026ion/m2. Erosion dynamics of the damaged layer and deuterium retention were studied. Surface modifications have been observed in the damaged material. Increased deuterium retention was detected on damaged tungsten by nuclear analysis methods; implanted helium accumulation was also measured.

14 MeV-neutrons from DT fusion reaction present a serious concern for materials of the first wall and divertor in a tokamak fusion reactor operating in steady state because of the damage produced in material structure. However, there is lack of information on radiation damage of plasma facing materials and their behavior under plasma impact. This paper is devoted to experimental investigation of tungsten at high level of radiation damage under steady state deuterium plasma. Tungsten is one of the important candidates as plasma facing material for application in ITER and, probably, beyond. The displacement damage of 1-80 dpa was produced in tungsten samples W (99,95% wt) by high-energy alpha particles He (3-4 MeV) from accelerator at Kurchatov Institute (cyclotron). The irradiated samples were then studied in deuterium plasma on the LENTA linear divertor simulator. Plasma exposures were made at 250 eV of ion energy and fluence 10-10 ion/cm. Erosion dynamics of the damaged surface layer (~6 μm) as well as deuterium retention were studied. Surface modifications have been observed in the damaged material. Increased deuterium retention was detected on damaged tungsten by nuclear analysis methods; implanted helium accumulation was also measured.

Plasma facing materials in a fusion reactor will suffer from both plasma fluxes and DT-neutron irradiations. Experimental investigations have been initiated aiming at assessment of the combined effect of high-level radiation damage and plasma induced erosion on these materials. Complex modeling studies were performed on the ion cyclotron and LENTA plasma simulator at Kurchatov Institute. Carbon materials and tungsten have been irradiated with 3–5MeV ions to reach 1–10dpa of radiation damage. The features of irradiated materials are described. Irradiated materials response to deuterium plasma (100–250eV D+ ions) at fluence 1025 ion/m2 was studied. Deformation effect and surface microstructure modification have been observed. Evaluation of erosion rate indicated erosion enhancement for radiation-damaged materials.

Plasma-facing materials (PFM’s) of a fusion reactor will be affected by high heat flux, fast particles and 14 MeV-neutron irradiation. All these factors are crucial for the lifetime of the reactor components. This paper is devoted to the experimental studying the r adiation damage effect on erosion of materials under plasma impact. To obtain a high level of radiation damage, we simulated an accumulation of radiation damage under fast neutron irradiation by fast ions with energies in the interval of 1 -60 MeV accelerated on the cyclotron at Kurchatov Institute. Using this method we can accumulate the radiation damage at the level equivalent to fast neutron effect at the dose of up to 10 22 neutron/cm in a few days operation of the cyclotron. Both carbon materials and tungsten were taken for the study as the targets: MPG -8 (Russian graphite), SEP NB-31 (ITER PFM candidate) and W (99,95% wt). Irradiation on the cyclotron has been performed by 5 MeV carbon ions for carbon materials and 3-4 MeV alpha particles for tungsten. The plasma experiments have been performed on the materials having accumulated 0,1 -10 dpa of radiation damage. Plasma erosion was studied on the linear plasma simulator LENTA. Irradiated samples were exposed to a steady-state deuterium plasma at 100 eV (D + ions) on carbon materials and 250 eV on tungsten to dose of up to 10 -10 ion/cm. Surface microstructure modification has been observed and comparison was made of damaged and non -irradiated materials. The evidences of radiation damage influence on the erosion process have been found by analysis of deformation, surface modification and erosion data. The study of erosion characteristics in plasma showed enhancement of erosion yield on carbon materials and structure damage on tungsten. New experimental approach developed in this work to explore the plasma-facing materials for accounting of neutron effect and the results obtained appear to be important for the further studies of the combined plasma and neutron irradiation effect on fusion PFM’s .

Plasma-facing materials (PFM’s) of a fusion reactor will be affected by high heat flux, fast particles and 14 MeV-neutron irradiation. All these factors are crucial for the lifetime of the reactor components. This paper is devoted to the experimental studying the radiation damage effect on erosion of materials under plasma impact. To obtain a high level of radiation damage, we simulated an accumulation of radiation damage under fast neutron irradiation by fast ions with energies in the interval of 1-60 MeV accelerated on the cyclotron at Kurchatov Institute. Using this method we can accumulate the radiation damage at the level equivalent to fast neutron effect at the dose of up to 10 neutron/cm in a few days operation of the cyclotron. Both carbon materials and tungsten were taken for the study as the targets: MPG-8 (Russian graphite), SEP NB-31 (ITER PFM candidate) and W (99,95% wt). Irradiation on the cyclotron has been performed by 5 MeV carbon ions for carbon materials and 3-4 MeV alpha particles for tungsten. The plasma experiments have been performed on the materials having accumulated 0,1-10 dpa of radiation damage. Plasma erosion was studied on the linear plasma simulator LENTA. Irradiated samples were exposed to a steady-state deuterium plasma at 100 eV (D ions) on carbon materials and 250 eV on tungsten to dose of up to 10-10 ion/cm. Surface microstructure modification has been observed and comparison was made of damaged and non-irradiated materials. The evidences of radiation damage influence on the erosion process have been found by analysis of deformation, surface modification and erosion data. The study of erosion characteristics in plasma showed enhancement of erosion yield on carbon materials and structure damage on tungsten. New experimental approach developed in this work to explore the plasma-facing materials for accounting of neutron effect and the results obtained appear to be important for the further studies of the combined plasma and neutron irradiation effect on fusion PFM’s .

The experimental date on structure, chemical and X-ray analysis of re-deposited material from eroded CFC and W macrobrush plates designed and manufactured in EU under ITER ELMs and disruptions heat loads are presented. Experiments were realized in plasma gun QSPA facility. Each targets were exposed to a large number of repetitive pulse of heat loads 0.5-2.0 MJ/m with 0.5 msec time duration. The principal result of impact I type ELMs-like plasma on material was in formation the films, consisted of the dust particles with spherical shapes, typical dimensions of 0.02-2.0 mkm and fractal surface structures (“cauliflower”). In dust particles the Auger spectrometer/SIMS analysis found out many of elements from vacuum chamber surface. X-ray crystal analysis show that tungsten re-eroded in the form of tungstencarbide (nearby 70%). The analysis of small angle scattering gives “halo” picture, which indicate of 10-20 nm clusters. The calculation for ITER of sorption surfaces (SSA) of dust particles are presented.