86,589 research outputs found
Characterization and discrimination of plastic materials using laser-induced fluorescence
No full textThe most meaningful spectral components in laser-induced fluorescence (LIF) spectra for several different commercial plastics have been individuated and used to automatically discriminate among different plastic materials and between plastics and complex organic materials, such as woods. Starting from LIF measurements on known samples, a number of significant wavelengths have been identified by principal component analysis (PCA). These have been used to produce intensity ratios functional to the discrimination. Threshold values for such ratios have been individuated in order to obtain an automatic recognition of plastics. The work done has been preparatory to the design and development of a multispectral imaging LIF system for fast detection of plastic debris in a post-blast scene. © The Author(s) 2016
Synthesis and characterization of ZnO nanorods with a narrow size distribution
No full textThe development of novel materials for energy harvesting applications or strain sensing has generated great interest towards zinc oxide (ZnO) nanostructures, and in particular towards the synthesis of ZnO nanowires or nanorods with well controlled morphology and properties. The high-yield mass production of such nanostructures by catalyst-free methods is a crucial aspect to enable a cost-effective large-scale development of new ZnO-based piezoelectric devices and materials. In the present work, we propose a method for the mass-production of high-purity ZnO-nanorods with a uniform size distribution, based on the combination of thermal decomposition of zinc acetate dihydrate and probe sonication in acetone. The quality of the produced ZnO nanorods is assessed through multi-technique characterization using field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and photo-luminescence spectroscopy (PL). The adopted synthesis method is simple, cost effective and feasible for large-scale production. Various process parameters such as precursor amount and growth time have been found to play an important role in controlling the formation of the as grown nanostructures with high uniformity in size and morphology. Size distribution curves were employed to depict the effect of various process parameters for tailoring the morphology, homogeneity and aspect ratio of the nanorods. Our results reveal that the high crystallographic quality of ZnO nanorods grown by a long-time thermal decomposition method is not affected by probe sonication, which is proposed as a post-synthesis step necessary to produce ZnO nanorod powder with a uniform distribution of diameters and lengths. © 2015 The Royal Society of Chemistry
Improvement of ENEA laser-induced fluorescence prototypes: An intercalibration between a hyperspectral and a multispectral scanning system
No full textLaser-induced fluorescence (LIF) is a well-recognised spectroscopic technique used in cultural heritage for non-destructive surface chemical analysis. It is particularly suitable for in situ analysis of delicate items such as artworks because it does not require any sample preparation or contact and can be used at a distance in situations where only optical access is available. Recently, ENEA has developed two LIF prototypes with multispectral (Forlab) and hyperspectral (Lifart) scanning systems that each return different types of results, making them necessary for and dependent on each other. Forlab's motorised optics enable the rapid acquisition of fluorescence maps and images of large surfaces in specific spectral wavelengths, while Lifart returns complete fluorescence spectra, providing the complete spectral information of an object. In this paper, the intercalibration of the two systems is reported together with a data analysis of the calibration samples and a software that automatically corrects imaging data, taking Forlab's filter passband and optical efficiencies into account in order to make these two configurations as easy to compare as possible. The new correcting algorithm is also tested on LIF measurements carried out on an Egyptian casket and sarcophagus, obtaining higher quality fluorescence images
Intercalibration of hyperspectral and multispectral systems for Laser Induced Fluorescence imaging
No full textLaser Induced Fluorescence (LIF) is a well-recognized spectroscopic technique for non-destructive surface chemical analysis. It is particularly suitable for in situ analysis on delicate targets as artworks, because it does not need any sample preparation nor contact, working remotely also where only optical access is available. Hyperspectral systems have the advantage to provide whole spectra of the analysed point, and thanks to motorized optics can produce fluorescence images and map of surfaces. Since the early 2000s ENEA has developed hyperspectral LIF scanning systems. To shorten significantly analysis time, overall on very large CH surfaces as building facades, ENEA DIM Laboratory has developed an imaging multispectral LIF system. Here we present intercalibration, data analysis and software to automatically correct such imaging data and take into account filter’s bandpass and optical efficiencies with respect to systems based on the use of spectrometers, avoiding lack of selectivity and accuracy due to the absence of whole spectra
Development of Calibration-Free Laser-Induced-Breakdown-Spectroscopy based techniques for deposited layers diagnostics on ITER-like tiles
No full textHigh temperature plasma in hydrogen isotopes is peculiar of thermonuclear fusion devices. The study of plasma-wall interaction is of paramount importance for avoiding both damage of plasma facing components (PFCs) and pollution of the plasma. To assure continuous and fault-free operation a strict control must be exerted on the amount of impurities deposited on, and of the fuel retained in the PFCs. This requirement makes Laser-Induced-Breakdown-Spectroscopy (LIBS) an ideal candidate for on-line quantitative monitoring of the walls of the current as well as of the next generation fusion devices like the International Thermonuclear Experimental Reactor (ITER). An experimental setup has been designed and realized in order to optimize the characteristics of a LIBS system working at low pressure and remotely, and it has been utilized in combination with calibration free procedures for quantitative analysis. In this work, a partial calibration free method has been developed for single shot analysis of hydrogen isotopes retention at the PFCs-like surfaces, based on the acquisition of high resolution spectra in a narrow wavelength range. Results of calibration free and partial calibration free have been obtained on suitably deuterated samples; preliminary spectroscopic considerations on tritium detection are also presented. © 2013 Elsevier B.V. All rights reserved
In Situ study of modern synthetic materials and pigments in contemporary paintings by laser-induced fluorescence scanning
No full textLaser-induced fluorescence (LIF) has found, in the recent years, widespread application to the field of material study and characterization. In particular, LIF has been applied to the assessment of damage, biological growth, and the analysis of specific materials on various surfaces in cultural heritages. Only a few papers deal with the application of LIF to the study of modern synthetic materials (mostly plastics) and pigments, and the analysis of contemporary works of art. Preliminary laboratory measurements on a wide range of plastic and cellulose-based materials, solvents, resins, and varnishes have been performed for rapid material characterization during in situ measurement campaigns in cultural heritage, security, and forensic contexts. Four paintings by Gastone Novelli, in the National Gallery of Modern and Contemporary Art, Rome, have been investigated by a compact LIDAR fluorosensor scanning system developed at the Laboratory of Diagnostic and Metrology in the ENEA Centre of Frascati (UTAPRAD-DIM Laboratory) for LIF measurements. Results and the relative data processing have provided fluorescence images, false color images, and punctual spectral information. The comparison with data and spectra from purpose-built reference databases has enabled recognition of materials on the paintings, and provided information on their production. © The International Institute for Conservation of Historic and Artistic Works 2015
Double pulse Laser Induced Breakdown Spectroscopy measurements on ITER-like samples
No full textLaser Induced Breakdown Spectroscopy (LIBS) is an attractive analytical technique for the in situ analysis of the chemical composition of the components inside the vacuum vessel of ITER and for estimating the tritium content in the machine. To improve its sensitivity a dual pulse (DP) configuration, with two laser pulses delayed in the range of nanosecond to several microseconds can be used. In this work DP measurements carried out jointly by ENEA and IPPLM associations in the frame of EFDA task WP13-IPH-A01-P3-01 on samples resembling ITER in vessel components after material re-deposition (still including carbon) are presented. A DP Nd:YAG laser, operating at 1064 nm, with delay between pulses ranging from 20 ns to 80 ms and pulse duration of 8-12 ns was used to interact with tungsten sample coated with 3 μm thick mixed layer of C/Al/W (Al was used instead of Be). An enhancement of the spectroscopic emission of the elements was observed compared to the standard LIBS measurements. A Calibration Free method was applied to the data for getting the concentration of each element. Results are in good agreement with the concentrations found by the post-mortem energy dispersive X-ray (EDX) analysis. © 2015 Elsevier B.V. All rights reserved
Plasma-wall interaction studies within the EUROfusion consortium: Progress on plasma-facing components development and qualification
No full textand (iii), the preferential sputtering of Fe in EUROFER steel providing an in situ W surface and a potential first-wall solution for DEMO. © 2017 Forschungszentrum Jülich GmbH.(ii) the progress in understanding of fuel retention, diffusion and outgassing in different W-based materials, including the impact of damage and impurities like NThe provision of a particle and power exhaust solution which is compatible with first-wall components and edge-plasma conditions is a key area of present-day fusion research and mandatory for a successful operation of ITER and DEMO. The work package plasma-facing components (WP PFC) within the European fusion programme complements with laboratory experiments, i.e. in linear plasma devices, electron and ion beam loading facilities, the studies performed in toroidally confined magnetic devices, such as JET, ASDEX Upgrade, WEST etc. The connection of both groups is done via common physics and engineering studies, including the qualification and specification of plasma-facing components, and by modelling codes that simulate edge-plasma conditions and the plasma-material interaction as well as the study of fundamental processes. WP PFC addresses these critical points in order to ensure reliable and efficient use of conventional, solid PFCs in ITER (Be and W) and DEMO (W and steel) with respect to heat-load capabilities (transient and steady-state heat and particle loads), lifetime estimates (erosion, material mixing and surface morphology), and safety aspects (fuel retention, fuel removal, material migration and dust formation) particularly for quasi-steady-state conditions. Alternative scenarios and concepts (liquid Sn or Li as PFCs) for DEMO are developed and tested in the event that the conventional solution turns out to not be functional. Here, we present an overview of the activities with an emphasis on a few key results: (i) the observed synergistic effects in particle and heat loading of ITER-grade W with the available set of exposition devices on material properties such as roughness, ductility and microstructur
Measurements of deuterium retention and surface elemental composition with double pulse laser induced breakdown spectroscopy
No full textEstimating the tritium amount retained in the plasma facing components and their surface layer composition is of crucial importance for ITER. Laser-induced breakdown spectroscopy (LIBS) is an analytical technique suitable for in situ measurements of both these quantities. For improving its sensitivity, the double pulse (DP) variant can be used, instead of the standard single pulse (SP). In this work Mo samples coated with 1.5-1.8 μm thick W-Al (as a proxy for Be) mixed layer, with co-deposited deuterium were analyzed under vacuum (∼5 10-5 mbar) by SP and DP LIBS, showing enhancement of the spectral intensity for the latter. Calibration free method was applied to the LIBS data for getting the elemental concentration of W and Al. Results are in satisfactory agreement with those obtained from preliminary, ion beam analysis measurements. Deuterium concentration was tentatively estimated by accounting for the intensity ratio between Dα and nearby WI lines. © 2016 EUROfusion
Use of ns and fs pulse excitation in laser-induced breakdown spectroscopy to improve its analytical performances: A case study on quaternary bronze alloys
No full textAnalytical performances of Laser Induced Breakdown Spectroscopy (LIBS) resulted not fully satisfactory in some cases such as historical bronzes, therefore, efforts should be focussed on improving ablation efficiency and on better understanding the plasma parameter evolution. To this aim a set of double pulse experiments have been carried out in almost collinear geometry at about 530 nm laser excitation. The first emitting source was either a ns or a fs laser the second a ns one. Data were collected as a function of the interpulse delay, in order to determine the ablation efficiency increase, to study the kinetics of plasma parameters (temperature, electron density) and the decay of atomic and ionic intensities with respect to the optical background. In parallel a previously developed model for laser ablation, ionization and following plasma decay, was implemented, adding a second laser pulse, to analyse the double pulse excitation in the considered geometry, and the time evolution of the same variables was investigated. Model results are able to reproduce the observed experimental trends and support the possibility of improving analytical performances by using the double pulse technique with inter-pulse delays in the entire investigated range. © 2014 Elsevier B.V
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