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Tungsten-based materials are possible candidates as PFCs in future fusion devices. LIBS is one of the most suitable techniques for monitoring erosion and deposition processes including fuel retention, due to its versatility and ability to perform in situ measurements. By deploying ps-LIBS, instead of ns, the laser ablation occurs with fewer melting effects. This work compares ns- and ps- (CF)-LIBS characterization of WZr(D) samples, at the linear plasma generator at Magnum-PSI at the DIFFER. The laser energy has been optimized for both laser regimes, lowering the laser energy for the ns regime (from 19.9 mJ pulse−1 to 7.4 mJ pulse−1) to approximate to ps regime (0.3 mJ pulse−1). All the experimental measurements have been performed at Patm. The pure WZr samples have been analyzed in ambient air, while the WZrD sample measurements have been performed under Ar gas flow. The retained deuterium content varies from 4 at% to 0.3 at%.

The elemental analysis of plasma-facing components (PFCs) with deposits is vital for the study of the material erosion, deposition, and fuel retention. For ITER-like divertor, first wall is formed by W-based deposit containing Be, O, D, H and other impurities. The quantification of fuel retention in these materials, including the depth dependence of the fuel retention and the elemental composition, is important. Calibration free laser-induced breakdown spectroscopy (CF-LIBS) is the only technique possible for online remote diagnostics with recognition of the hydrogen isotopes. But the most commonly used ns-LIBS leads to material's overheating; thus, larger non-realistic retention of hydrogen isotopes is generally obtained. In this work, we report the quantitative ps- and ns-CF LIBS analysis of W-based model material (WCu). A WCu alloy has been selected to permit the analysis of tungsten spectral lines in a binary alloy with an element with not too many weak lines. Surface experiments are performed by LIBS using ~30 ps and 5 ns, 1064 nm laser pulses at atmospheric pressure. One of the advantages of ps laser is that it ablates the surface more efficiently, without overheating the ablated material. The laser ablation threshold for the plasma creation in the ps regime is situated at lower energy, thus less material is needed and better depth resolution can be obtained. Suitable Cu and W spectral lines have been selected for the precise evaluation of the electron temperature using the Saha-Boltzmman plots. The electron density values were found from the Saha-Boltzmann plots and the Stark broadening of the Hα spectral line. The results demonstrate the successful detection of W and Cu spectral lines using ps- and ns-LIBS and its quantification.

In this paper we discuss ion-induced ultra fast demagnetization and present an approach for experimental investigation of the following magnetization dynamics. The effect, if confirmed, might have applications in spintronics, micro-scale power generation or communication and for basic research in the area of ion track formation as a mean to observe thermodynamics in ion tracks. The proposed approach lies in using magnetic antenna for detection of the field change induced by ion stopping and converting the field change to electrical signal. The approach was confirmed feasible, providing temporal resolution below 100ps in tests with other fast impulse heat source – a femtosecond laser. Presented experimental results and simulations based on ion-induced thermal spike model show a necessity to develop broadband antennas with high sensitivity and micro-scale dimensions together with specialized high frequency amplifier electronics, in order to allow observation of ultra-fast ion-induced demagnetization.

The aim of this contribution is a theoretical study for the estimation of the dynamic stress intensity factor (DSIF) using results from an experimental measurement. Using optical methods, it is possible to determine individual displacements of crack surfaces in multiple distances from the crack tip. Based on the theoretical distribution of displacements in the crack front, the DSIF can be estimated using the displacement extrapolation method at each time step. The main motivation for this methodology is the difficulty of estimation DSIF in real structures. The described approach is consequently compared with conventional numerical methods and the applicability is evaluated.

Femtosecond laser-induced magnetization dynamics is a popular research topic, due to its potential applications in fast magnetic storage devices and the field of spintronics. In the article we present a novel technique for time-resolved measurement of femtosecond laser-induced magnetization dynamics, based on inductive sensing by a loop antenna. It allows performing investigation of magnetization dynamics in highly absorbing samples, samples with patterned surfaces and samples coated by a thin metallic layer, which are difficult to study using optical techniques. To test the technique, both thick and thin films made of highly absorbing and diffusing materials, were used. Results of tests for several ferromagnetic materials including Gadolinium are discussed in the article. The test results prove that the method provides a simple tool to observe and study magnetization dynamics phenomena in the vicinity of the materials’ Curie temperature.

This paper is focused on the preparation of boron doped diamond (BDD) cantilevers for MEMS applications. Hot filament CVD diamond deposition technique was used for preparation of highly boron doped thin film. The fabrication process consisted only of dry etching steps and masking process, no wet etching of substrate was used. Therefore, it was necessary to optimize both anisotropic and isotropic etching to release the cantilever structure from silicon substrate. Doped diamond cantilevers were etched by reactive ion etching using inductively coupled plasma (ICP RIE) through aluminum etching masks. The optimal properties of fabrication process led to high quality MEMS structures. The resulting cantilevers were investigated by scanning electron microscopy (SEM) and laser vibrometer system. Finally, we demonstrate a BDD cantilever (5 μm width) with the main resonant frequencies at 22.2 kHz, 46.6 kHz, 52.2 kHz and 65.6 kHz.

The paper deals with the measurement and identification of surfaces after machining in a non-contact manner. It presents a new modified measurement method and its implementation, the results of intensity distribution in the defocusing plane, their analysis and interpretation. The scanned intensity distribution at the defocusing plane gives information necessary to assess the second derivatives, and thus, surface functions which can be used to determine groove curvatures of the real surface morphology. The proposed method of measurement has proved to be very sensitive in evaluating the differences between surface finishing methods by which the measured surface standards (etalons) were machined. Two methods of machining were chosen: face grinding and planning. By comparing the roughness standard values Ra, there were obtained relationships between these values and the parameter of the characteristic frequency of vertical inequality being measured according to the presented method. A good correlation between the measured and surface standard values with the correlation coefficient taking a range of values from 0.8 to 1 was achieved. Web of Science 12 5 188 184

The problem of heat convection from surface to air at very low temperature differences has been solved by experimental/numerical approach. The laser-based probing technique of laser beam deviation detection was developed for the measurement of air refractive index gradients. The data obtained were processed by interactive coupling with numerical modelling tools. As it was approved, the key properties of the boundary layer such as temperature and temperature gradient profiles can be analysed in detail and the impact of various factors can be studied. The numerical simulation and the experimental data comparison had shown good coincidence; nevertheless, at a temperature difference of only few degrees, the influence of ambient air movement has to be considered in simulation process. The presented boundary layer analysis can be successfully applied at specific conditions of building physics with the low temperature differences.

The influence of the deposition parameters on the growth, structure and mechanical properties of the TiBx coatings is studied. The TiBx coatings represent a nanocomposite system, in which random or oriented TiB2 nanocrystallites are embedded in an amorphous matrix as is revealed by cross-sectional transmission electron microscopy. We show that low-energy ion bombardment (Ei ) of growing TiBx coating, influences the preferred orientation of TiB2 crystallites. The increase of ion current density (is) by means of negative substrate bias voltage (Us) leads to change from random to the (0001) preferred crystal orientation whereby the electrical biasing promotes crystal growth in the coating and the (0001) texture appears gradually during the film growth. Together with the (0001) preferred orientation selection the composition B/Ti ratio was changed from 2.9 (floating potential, Ei = 8 eV) to 2.4 (Ei = 94 eV). The highest amount of oriented (0001) crystallites and highest hardness H = 53 GPa exhibit TiBx coatings deposited at Ei = 94 eV and is = 2.69 mA.cm−2.

Superhard titanium diboride (TiB2) coatings (Hv> 40 GPa) were deposited in Ar atmosphere from stoichiometric TiB2 target using an unbalanced direct current (d. c.) magnetron. Polished Si (0 0 1), stainless steel, high-speed steel (HSS) and tungsten carbide (WC) substrates were used for deposition. The influence of negative substrate bias, Us, and substrate temperature, Ts, on mechanical properties of TiB2 coatings was studied. X-ray diffraction (XRD) analysis showed hexagonal TiB2 structure with (0 0 01) preferred orientation. The texture of TiB2 coatings was dependent upon the ion bombardment (Us increased from 0 to −300 V) and the substrate heating (Ts increased from room temperature (RT) to 700 °C). All TiB2 coatings were measured using microhardness tester Fischerscope H100 equipped with Vickers and Berkovich diamond indenters and exhibited high values of hardness Hv up to 34 GPa, effective Young's modulus E*=E/(1–ν) ranging from 450 to 600 GPa; here E and ν are the Young's modulus and Poisson's ratio, respectively, and elastic recovery We≈80%. TiB2 coating with a maximum hardness Hv≈73 GPa and E*≈580 GPa was sputtered at Us=−200 V and Ts=RT. Macrostresses of coatings σ were measured by an optical wafer curvature technique and evaluated by Stoney equation. All TiB2 coatings exhibited compressive macrostresses.

Experimental study of the surface quality produced by abrasive waterjet (AWJ) on metallic materials has been performed. The surface roughness/waviness was quantitatively evaluated by using the contactless optical measurement. In order to characterize the cut surface qualities, a single-parameter criterion has been proposed. Based on root mean square (RMS) roughness evaluation of the worst cut surface zone, the dimensionless statistical parameter C can be calculated as a basic quantity for AWJ surface cut characterization. As it was approved, besides its dependency on depth of AWJ trace, the value of C-parameter for the specific material is noticeably related also to the traverse speed of the cutting head. Such a relationship can be potentially used for adjusting the cutting speed of the machining process.

The problem of retrieving the particle size distribution is solved by using the optical diffraction method. Angular distribution of scattered laser beam (670 nm) is measured by ring-gap photodetector movable along the laser beam. The elimination of undesirable optic reflections using lens-less concept, keeping the geometry of ring-gap diaphragm as well as integral power spectrum measurement stable, and the possibility of measuring relatively large depths of scene are the main advantages of such a measuring scheme. The numerical solution of this ill-posed inverse problem in small scattering angle approximation is based on regularization method, minimizing the Tikhonov's functional. It is shown that the inverse problem of separation of particle size fractions dispersed in a deep volume is solvable with reasonable accuracy maintaining the stability of the solution.

The aim of the study was to evaluate the effect of a cell-free hyaluronate/type I collagen/fibrin composite scaffold containing polyvinyl alcohol (PVA) nanofibers enriched with liposomes, basic fibroblast growth factor (bFGF) and insulin on the regeneration of osteochondral defects. A novel drug delivery system was developed on the basis of the intake effect of liposomes encapsulated in PVA nanofibers. Time-controlled release of insulin and bFGF improved MSC viability in vitro. Nanofibers functionalized with liposomes also improved the mechanical characteristics of the composite gel scaffold. In addition, time-controlled release of insulin and bFGF stimulated MSC recruitment from bone marrow in vivo. Cell-free composite scaffolds containing PVA nanofibers enriched with liposomes, bFGF, and insulin were implanted into seven osteochondral defects of miniature pigs. Control defects were left untreated. After 12 weeks, the composite scaffold had enhanced osteochondral regeneration towards hyaline cartilage and/or fibrocartilage compared with untreated defects that were filled predominantly with fibrous tissue. The cell-free composite scaffold containing PVA nanofibers, liposomes and growth factors enhanced migration of the cells into the defect, and their differentiation into chondrocytes; the scaffold was able to enhance the regeneration of osteochondral defects in minipigs.

Improved staging of cartilage degeneration is required, particularly during the early stages. We correlated mechanical properties with histological and macroscopic findings.One hundred and twenty cartilage samples were obtained during total knee arthroplasty. Two adjacent plugs were harvested--one for histological classification and one for macroscopic and biomechanical purposes. Dynamic impact testing was performed; normal stress, dissipated energy (∆E), tangent modulus and stiffness were evaluated.Samples were classified according to six categories of the ICRS histological scale. Mechanical characteristics revealing significant differences between the groups (p0.01) were specific damping and related absolute ∆E. A significant correlation was found between the macroscopic score and specific damping, as well as absolute and relative ∆E (p0.01). A strong relation was revealed between relative ∆E and cartilage thickness (p0.001; R (2) = 0.69).Only ∆E correlated with the condition of the cartilage--the value increased with decreasing quality-and is the most suitable characteristic. This change appears substantial in initial stages of cartilage deterioration.

Investigation of joint cartilage properties is of prime importance due to facilitation of its routine diagnostics and artificial tissue engineering. This experiment is based on our previous work in which we have developed new technique for dynamic testing of cartilage tissue biomechanical properties using blunt impact approach. Obtained data are confronted with ICRS histological classification of examined knee cartilage samples.

The paper deals with results obtained by means of contactless optical shadow method and by commercial methods, namely by using an optical commercial profilometer MicroProf (FRT) and a contact profilometer HOMMEL TESTER T8000. The main emphasis is put on the analysis of results for defining the process of creation of a new surface generated by the stream of abrasive waterjet, including its geometric parameters and mechanisms of cutting tool-material interaction. New possibilities of the surface quality evaluation and optimizing the technological parameters selection of the cutting process appear.

The study is focused on the biomechanical aspects of the anterior cruciate ligament (ACL) reconstruction procedures with an emphasis on evaluating the dynamic strain of materials commonly used for this purpose. Separate and multiple, equally tensioned strands of hamstring grafts used for the reconstruction of the ACL were biomechanically tested and compared to original ACL and bone-patellar tendon-bone (BPTB) grafts, using tissue samples from cadavers. The study was focused on measuring such material properties as the strength, stiffness, maximum load, and elongation at maximum load of the original ACL, BPTB graft, and single tendon hamstring (gracilis and semitendinosus) grafts, continued by double strands and finally by four-strand graft (STG) evaluation. Fresh-frozen cadaveric knees were used, which had been clamped and tensioned equally. The measurement was performed by drop-weight testing, using a Laser Doppler Vibrometer as a basic sensor of the dynamic movements of the gripping clamps, with parallel correlation by a piezoelectric transducer. The grafts for experiments were obtained from 21-paired knees. The measurement was performed at room temperature (21 degrees C) after 24 h of thawing at 4 degrees C. All the specimens were measured for their response to the dynamic tensile load. The maximum strength values were obtained and calculated for the appropriate section area of the specimen. The tensioned strands of the original ACL showed a maximum average load of 1,246 +/- 243 N in the section area of about 30 mm(2) (max. stress 41.3 MPa); the strands of BPTB grafts showed values of 3,855 +/- 550 N in the section area of 80 mm(2) (max. stress 40.6 MPa); the gracilis tendons showed 925 +/- 127 N in the section area of 10 mm(2) (max. stress 95.1 MPa) and the semitendinosuss yielded a result of 2,050 +/- 159 N in the area of 20 mm(2) (max. stress 88.7 MPa). Of all the materials, the original ACL have the lowest strength and stiffness in respect of their biomechanical properties. BPTB grafts showed a slightly higher value of maximum stress, while both the gracilis and semitendinosus tendons showed double the value of maximum load per section area-tensile stress. Two- and four- combined hamstring strands clamped together and equally tensioned with a drop-weight had the combined tensile strength properties of the individual strands within the estimated range of measurement errors. No significant changes in maximum loads/stresses were observed under impact loading conditions. The results of this study demonstrate that equally tensioned four-strand hamstring-tendon grafts have higher initial tensile properties than those in other varieties of samples. From a biomechanical point of view, they seem to be a reasonable alternative procedure for ACL reconstruction.

In the paper a contactless method capable to measure a surface unevenness is described. The method is principally based on oblique illumination of the rough surface with normal viewing of the illuminated area by CCD camera. The light intensity distribution in an image read by camera involves inherently information about the surface microprofile. The amount of light scattered to the normal direction of surface follows the relations of light diffraction and shading on surface hills, grains and dimples in microscale scene. In the paper the contribution of these effects on the overall light scattering is discussed and the correlation length of the roughness is used as a criterion to an accounting whether the diffraction is important. A quantitative calibration procedure has been proposed in order to evaluate the main surface roughnesslwaviness parameters.© (2005) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Using of several sophisticated optical techniques is reviewed to test the flatness of semiconductor wafers and to measure thin-film residual stresses, induced by various technological processes. Thin silicon membranes have been also inspected to obtain the membrane tension values and thickness variations. Besides this, experimentally by using of Laser Doppler Vibrometer the dynamics of MEMS microcomponents has been studied, too. In the paper, specific features of the methods, where performances and limitations, together with some remarks, regarding practical experiences of the exploitation, are reported.© (2005) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

For ITER and other future fusion devices, tungsten (W) and its alloys are primary candidates for the first wall in divertor, and molybdenum (Mo) will be used as the background material for erosion mapping and thickness control of the deposited layers and mirror materials. Considering the advantage of on-line analysis, laser-induced breakdown spectroscopy (LIBS) is being considered as the most promising tool to be used at ITER for the monitoring of the erosion and deposition processes and the fuel retention at the first wall. In this paper, picosecond (∼30 ps) and nanosecond (8 ns) time-resolved LIBS spectra were recorded for the characterization and comparison of fusion-related high-Z pure materials (W and Mo) at atmospheric pressure in ambient air. The plasma temperature was calculated using the Boltzmann plots of both neutral and ionic species, while the electron density was evaluated from the Saha equation. In the case of ps laser pulses, lower electron temperature and density were observed. The lower temperature in the ps regime is leading to a higher neutral to ionic ratio. At shorter delay times, the difference between electron densities was smaller, but with the increased delay, the difference became significant. The obtained values of ablation rates show that the ablation rate in ps regime is approximately 4 times lower compared to the ns regime. Lower electron density, also due to the lower ablation rate in the ps regime, leads to less Stark broadening and finally narrower spectral lines in the ps regime than in the ns one. The lower energy for ps laser-plasma generation (0.3 mJ/pulse; equivalent to a fluence of 1.7 Jcm−2) allows to obtain a lower ablation rate, which leads to a better depth resolution, which is crucial for depth analysis of fusion-related materials.