The effect of high-power pulsed-laser irradiation generated in a GOS 1001 installation in the Q‑switched mode (power density q 1.2 × 1012 W/m2, pulse duration of τ0 = 50 ns, number of pulses N = 1–4) in vacuum on the porous structure of the vanadium sample surface is studied, as well as on its hardness determined in two ways based on the restored-imprint method and on the kinetic indentation method. The porous structure is formed during the implantation of helium ions (energy 30 keV, dose 2.0 × 1023 m–2, ion-flux density 4.8 × 1018 m–2 s–1, temperature 500 K). It is shown that irradiation with helium ions causes vanadium hardening by about a factor of two, and the microhardness values determined by the restored-imprint method are slightly lower than the kinetic hardness values. It is found that a common feature of target destruction under laser radiation, a crater appearance, surrounded by a ridge, behind which there is a zone of thermal influence. Erosion observed in this zone, caused by the destruction of domes of blister bubbles filled with implanted helium and impurity atoms (C, O, N) which are present in the liquid metal. It is found that with an increase in the number of laser pulses, the microhardness in the crater decreases, while the narrow area around it hardens, and with further distance from the crater, the microhardness approaches values corresponding to that of vanadium implanted with helium ions.

The features of damageability of niobium by pulsed fluxes of laser radiation (LR) in free-running (power density qFR = 105–106 W/cm2 with pulse duration τFR = 700 μs) and Q-switched (q = 108–109 W/cm2, τQS = 80 ns) modes in comparison with pulsed effects of helium ion (HI) and helium plasma (HP) fluxes in the Plasma Focus (PF) setup at a flux power density qi ~ 108 W/cm2 and qp ~ 107 W/cm2, respectively, and pulse durations τi ≈ 30–50 ns and τp ≈ 100 ns were studied. LR fluxes were exposed to Nb in air; the working gas in the PF chamber was helium. It is shown that, in contrast to the effect of helium ion and helium plasma fluxes on niobium in the PF installation, which contribute to the erosion of the material, irradiation of niobium with pulsed LR in air fluxes under the implemented conditions does not cause noticeable surface erosion. When Nb is exposed to pulsed LR in the FR mode, the melt interacts with air and forms a thin film of elements of liquid and gas phases on the irradiated surface. A similar nature of Nb damageability under conditions of laser and beam-plasma treatment was found: a wavy relief of the irradiated surface with the presence of droplike fragments on it, extended wave crests, and microcracks. Irradiation of Nb with pulsed LR fluxes in the FR mode leads to formation of sections with block and cellular structures in the surface layer (SL), which are also formed after experiments in the PF chamber. It was found that, after laser treatment in the FR and Q-switched modes, bubbles (blisters) are not formed in the SL of niobium, which are always present on the irradiated surface when exposed to pulsed fluxes of HI and HP in the PF chamber owing to implantation of helium ions into Nb. It is noted that, in laser experiments, there is no possibility of implanting working gas ions into the material, which is typical of beam-plasma impacts in PF devices, which affects damageability parameters and modification of the structure of the irradiated SL.

Changes in the morphology of the vanadium surface are studied as a result of the separate and sequential action of helium ions (for an energy of 30 keV, a dose of 1.0 × 1022 m–2, an ion-flux density of 4.8 × 1018 m–2 s –1, and a temperature of ~500 K) and high-power pulsed laser radiation in the Q-switched mode (power density of q = 1.2 × 1012 W/m2, pulse duration of τ0 = 50 ns, and a pulse number N varying from 1 to 4). It is found that the effect of laser irradiation on vanadium samples before and after ion implantation (resulting in the formation of a crater with a rim due to the splashing of melted metal) is identical. In the case of the preliminary introduction of helium into the material the splash of metal is more intense. Helium implanted into the samples causes radiation blistering; the subsequent influence of laser pulses intensifies material erosion in the area located immediately behind the rim (resulting in a growing number of peeled layers, merging blisters, etc.), which is probably triggered by high temperatures and thermal stresses emerging in this area (even after discontinuing laser irradiation). Under reactor operating conditions this effect can lead to increased plasma contamination. It is shown that the damage of a target inside the craters in the initial vanadium samples feature occasional cracks, wavy and droplet structures, as well as beading, whereas along with the above changes the samples pre-irradiated with helium contain no cracks inside the crater although areas showing boiling of the material are clearly visible.

The features of the destructive effect on metal materials have been studied at high pressures generated in two similar conditions, namely, upon irradiation of the target samples with pulsed laser radiation and beam-plasma flows created in plasma focus (PF) installations. In both cases, similar parameters of radiation-heat treatment were set: power density q ~ 1010–1011 W/cm2 and pulse duration τ ~ 10–100 ns. It has been shown that the double exposure to laser radiation of vanadium and molybdenum thin samples with the thickness of 0.3 and 0.1 mm, respectively, leads to formation of molten zones in the materials that have deep craters inside. The craters extend over the entire thickness of the samples, on the back side of which the recesses end up with holes with diameters of ~0.1 mm for V and 0.2 mm for Mo. In a tungsten sample 0.2 mm thick, the depth of the craters in the molten zone is smaller than its thickness, but there are microcracks on the back of the sample. On the basis of numerical estimates of the process under study, it has been suggested that the observed effects are associated with the creation of high pressure zones of ~1–10 GPa in the irradiated targets, localized in microregions of radius r ~ 0.1 mm. In these zones, the high pressure behavior of the solid phase of the target materials with the tensile strength magnitude σB ≤ 1 GPa (V, Mo, W) is similar to the behavior of liquid. The pseudo-liquid phase of the material is displaced from the center of the crater, where the pressure is maximal, to its peripheral region of low pressure with the subsequent release of matter from the target through the irradiated surface at speed of ~103 m/s. In experiments using the PF, the mechanism responsible for the formation of craters when a powerful pulsed laser radiation is applied to the target is not realized owing to the different nature of the distribution of the absorbed energy density in the surface layer of the irradiated sample. The region in which the energy is absorbed during the implantation of particles into the material is determined mainly by the average energy and the diameter of the ion beam (Еi ≈ 100 keV, d ~ 2–10 mm) and exceeds the corresponding impact region obtained under laser irradiation by one to two orders of magnitude.

The features of the damage of the surface layer of vanadium under the action of pulsed laser radiation are studied. Laser irradiation is carried out in air using a GOS 1001 setup in the Q-switching mode with the following parameters: flux power density q = 1.2 × 108 W/cm2, pulse duration τ0 = 50 ns, and number of pulses N = 1–6. The typical surface damages induced by the laser pulses are found to include the melting of material, a microcrack network, a wavy relief, and drop-like particles. The central region characterized by the greatest degree of damage contains also individual drops of metal, which crystallized like a spiral. The heat-affected zone (HAZ) adjacent to the central one is damaged to a significantly weaker extent. Surface degradation increases as the number of pulses increases. Laser irradiation is revealed to change the X-ray diffraction (XRD) patterns: loss of texture, presence of vanadium-oxide signal, peak broadening, and lattice parameter increase (from 3.022(2) to 3.027(3) Å). It is shown that preliminary irradiation with argon ions (dose of 1022 m–2, E = 20 keV) affects no surface damage of the central region, while in the adjacent heat-affected zone, there is a spallation of local surface regions.

Specimens of materials for prospective use in chambers of nuclear fusion reactors with inertial plasma confinement,namely,W,ODS steels,Eurofer 97 steel,a number of ceramics,etc.,have been irradiated by dense plasma focus devices and a laser in the Q-switched mode of operation with a wide range of parameters,including some that noticeably exceeded those expected in reactors.By means of 1-ns laser interferometry and neutron measurements,the characteristics of plasma streams and fast ion beams,as well as the dynamics of their interaction with solid-state targets,have been investigated.3D profilometry,optical and scanning electron microscopy,atomic emission spectroscopy,X-ray elemental and structural analyses,and precise weighing of specimens before and after irradiation have provided data on the roughening threshold and the susceptibility to damage of the materials under investigation.Analysis of the results,together with numerical modeling,has revealed the important role of shock waves in the damage processes.It has been shown that a so-called integral damage factor may be used only within restricted ranges of the irradiation parameters.It has also been found that in the irradiation regime with well-developed gasdynamic motion of secondary plasma,the overall amount of radiation energy is spent preferentially either on removing large masses of cool matter from the material surface or on heating a small amount of plasma to high temperature(and,consequently,imparting to it a high velocity),depending on the power flux density and characteristics of the pulsed irradiation.

The copper vapor laser (λ=271 nm) “KULON-10Cu-M” was used to modify 32Li2O-26Nb2O5-42SiO2 glass. Morphology of the modified area studied using polarization optical microscopy. Discovered ablation, the refractive index change and crystals haze. μ-Raman spectroscopy for the laser irradiated parts indicates that only a single phase of LiNbO3 is observed.

The following investigation of the damageability of the Al2O3 oxide ceramic coating on the aluminum substrate under the influence of the concentrated energy fluxes of different nature and pulse duration performed: pulsed laser radiation in the free running mode (at the power density of q = 105–2 × 106 W/cm2 and pulse duration of τi = 0.7 ms) and modulated Q-switched mode (q = 107–108 W/cm2, τi = 80 ns), as well as the beam-plasma influence at q = 107–109 W/cm2, τ = 50–100 ns. It is shown that, under the influence of laser radiation within the millisecond and nanosecond ranges of the pulse impact on a semitransparent ceramic coating, the partial destruction and peeling of the ceramic layer from the metal substrate is observed. The mechanisms of the observed damageability are determined. The threshold values of the laser radiation flux at which the coating is damaged, caused by peeling, are experimentally estimated. The distribution of the temperature in the surface layer of the samples was calculated by numerical simulation, and it was shown that during laser irradiation the temperature reaches its maximum values at the depth corresponding to the contact area between the coating and substrate. It was established that the impact on the aluminum samples with the ceramic coating from the fast deuterium ion fluxes and high temperature deuterium plasma in the plasma focus device results in melting and partial evaporation of the coating surface layer; but in this case, no cracking or peeling from the aluminum substrate is observed.

Parallel use of directed plasma/fast ion streams from Dense Plasma Focus and of laser radiation (in a free running and Q-switched modes) for irradiations of targets looks perspective for tests of materials designed to withstand extreme thermal loads in the mainstream fusion reactors with inertial and magnetic plasma confinement. It is so because of a wide range of power flux densities and pulse durations generated by them. Tungsten is counted as the most appropriate material for the plasma-facing components. Main features of degradation of the surface layer of double forged tungsten were determined at different conditions of its irradiation by these streams. Chief similarities and differences in damageability obtained in the regimes are fixed – blisters, craters, porosity, microcracks, and discontinuity flaws etc. – that are peculiar characteristics for each mode of irradiation. The observed resemblances and dissimilarities that are specific for each regime of irradiation are explained with the help of numerical modelling of the treatment processes. It is shown that a so-called Integral Damage Factor may be used only in restricted ranges of parameters of an irradiation. It was found that in the regime of irradiation with the well-developed gas dynamic motion of secondary plasma the overall energy of radiation will be spent preferentially either on mass removal from the material's surface or on heating of a small amount of matter to high temperature (and consequently into its fast movement) depending on power flux density of radiation and its pulse structure.

The degradation of a bilateral pressed tungsten surface layer by pulsed laser irradiation in the free-running mode (power density q = 10 5 –5 × 10 6 W/cm 2 , pulse duration τ = 0.7 ms) and the Q -switched mode ( q = 10 9 –10 10 W/cm 2 , τ = 80 ns) as well as under plasma beam irradiation in a plasma focus (PF) device ( q = 10 8 –10 12 W/cm 2 , τ = 10–100 ns) has been investigated. The features of the degradation, erosion, and structural changes in the tungsten surface layer under different irradiation conditions have been determined. It has been shown that the use of PF devices in combination with laser equipment is promising for the simulation of the extreme radiation–thermal effects in materials that are typical of thermonuclear fusion devices with magnetic and inertial plasma confinement.

The effects of powerful pulsed ion and high-temperature plasma fluxes generated in a plasma focus (PF) device and the effect of free running laser radiation on a corundum (α-Al 2 O 3 ) ceramic produced by powder technology are studied. The power flux density q and acting pulse time τ for plasma stream, ion flux, and laser irradiation were q p ≈ 10 7 W/cm 2 and τ p ≈ 100 ns, q i ≈ 10 8 W/cm 2 and τ i ≈ 20 ns, and q l ≈ (3–5) × 10 5 W/cm 2 and τ l ≈ 0.7 ms, respectively. The resistance of the ceramic to pulsed energy fluxes was estimated by the weight loss of irradiated specimens and by the surface layer defects (damage). The combined use of PF and pulsed laser irradiation is shown to allow simulation of the extreme erosion and damage of materials in thermonuclear fusion facilities (such as ELM effects in ITER or at the first wall of inertial confinement chambers).

The influence of pulsed laser irradiation on mechanical properties of annealed and cold-worked pure aluminum is studied. Mechanical tests are performed by means of a miniaturized disk bend test technique using specimens with the diameter of 3 mm. It is established that laser irradiation does not influence the mechanical properties of annealed aluminum but leads to softening of cold-worked material. After 100 laser pulses, nearly complete recovery of aluminum strength occurs to the value characteristic of the annealed state. The plasticity of cold-worked aluminum is lower than that of annealed material and does not vary upon laser irradiation. Thermal and shock-wave mechanisms of laser impact are estimated, and it follows that, under the given parameters of irradiation, the main contribution to the variation of properties is that of shock-wave mechanism related to generation and propagation of acoustic waves which stimulate athermal annealing and recovery of dislocation structure.

A new method for the creation of composite materials using previously developed laser technology based on their strengthening by their own particles coated with nanothin carbon film is proposed.

OF THE CONDENSATE PRODUCTS. O.I.Yakovlev, L.I.Ivanov, V.P.Kolotov, N.N.Dogadkin, V.K.Karandashev, E.E.Kazilin, and V.S.Popov; Vernadsky Institute of Geochemistry & Analytical Chemistry, RAS, Moscow 119991,Kosygin St.,19 (yakovlev@geokhi.ru); Institute of Metallurgy and Material Sciences RAS, Moscow; Institute of Microelectronics Technology and High Purity Materials, RAS, Chernogolovka (karan@ipmthpm.ac.ru).