21 research outputs found
LIBS plasma in atmospheric pressure argon, nitrogen and helium: Spatio-temporal distribution of plume emission and Hα linewidth
No full textThis work has been carried out within the framework of the EUROfusion Consortium, funded by the European Union via the Euratom Research and Training Programme (Grant Agreement No 101052200—EUROfusion). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Commission. Neither the European Union nor the European Commission can be held responsible for them.
Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART2.Laser Induced Breakdown Spectroscopy (LIBS) method is considered for assessing the retention of hydrogen isotopes in the ITER plasma-facing components during the maintenance breaks when the reactor is filled with near atmospheric pressure nitrogen or inert gas. At these conditions, the broadening of the spectral lines of hydrogen isotopes and the reduction of line intensities complicates the distinguishing of hydrogen isotopes. The aim of the present study was to investigate the effect of atmospheric pressure nitrogen, argon and helium ambient gas on the spatio-temporal distribution of the LIBS plasma plume emission and linewidths of Hα line, representing the hydrogen isotopes. Nd:YAG laser with 8 ns pulse width was used to ablate the molybdenum (Mo) target with hydrogen impurity. The development of the formed plasma plume was investigated by time and space-resolved emission spectra in the 20 nm range around the 656.28 nm Hα line. For all gases used in the experiments, the intensity and linewidth of Hα line decreased with the delay time between the laser pulse and the spectral registration. At the same linewidth values, the highest intensities were obtained in the helium atmosphere while the lowest intensity was obtained in nitrogen. According to spatially resolved spectral measurements, the Hα line was most intense near the Mo target while the Mo lines peaked farther away. In the case of the helium atmosphere, the plasma plume emission was observed at a longer distance from the target and it decayed faster than in argon and nitrogen atmospheres. According to these results, helium is the most beneficial ambient gas for hydrogen isotope detection by atmospheric pressure LIBS. The use of argon ambient gas may be required when LIBS is used for the simultaneous determination of fuel and He retention in the wall material. --//-- This is an open access article Indrek Jõgi, Jasper Ristkok, Jelena Butikova, Jüri Raud, Peeter Paris, LIBS plasma in atmospheric pressure argon, nitrogen and helium: Spatio-temporal distribution of plume emission and Hα linewidth, Nuclear Materials and Energy, Volume 37,
2023, 101543, ISSN 2352-1791, https://doi.org/10.1016/j.nme.2023.101543 published under the CC BY-NC-ND licence.EUROfusion Consortium Grant Agreement No 101052200; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART2
LASER-INDUCED PLASMA SPECTROSCOPY OF PLASMA FACING MATERIALS
No full textAbstract Qualitative elemental analysis of ASDEX divertor plates' material was performed by laser-induced plasma spectroscopy. The spectra show a decrease in impurity signals and an increase in substrate signal during the layer-by-layer ablation. The selective detection of the plasma light is reasonable for obtaining emission spectra resembling those attained using time-gated detectors
Texture analysis and optical anisotropy measurements of leukocytes for early diagnostics of diabetes mellitus
No full textMonitoring of tritium and impurities in the first wall of fusion devices using a LIBS based diagnostic
No full textLaser-induced breakdown spectroscopy (LIBS) is one of the most promising methods for quantitative in-situ determination of fuel retention in plasma-facing components (PFCs) of magnetically confined fusion devices like ITER and JET. In this article, the current state of understanding in LIBS development for fusion applications will be presented, based on a complete review of existing results and complemented with newly obtained data. The work has been performed as part of a research programme, set up in the EUROfusion Consortium, to address the main requirements for ITER: (a) quantification of fuel from relevant surfaces with high sensitivity, (b) the technical demonstration to perform LIBS with a remote handling system and (c) accurate detection of fuel at ambient pressures relevant for ITER. For the first goal, the elemental composition of ITER-like deposits and proxies to them, including deuterium (D) or helium (He) containing W-Be, W, W-Al and Be-O-C coatings, was successfully determined with a typical depth resolution ranging from 50 up to 250 nm per laser pulse. Deuterium was used as a substitute for tritium (T) and in the LIBS experiments deuterium surface densities below 1016 D/cm2 could be measured with an accuracy of ∼30%, confirming the required high sensitivity for fuel-retention investigations. The performance of different LIBS configurations was explored, comprising LIBS systems based on single pulse (pulse durations: ps-ns) and double pulse lasers with different pulse durations. For the second goal, a remote handling application was demonstrated inside the Frascati-Tokamak-Upgrade (FTU), where a compact, remotely controlled LIBS system was mounted on a multipurpose deployer providing an in-vessel retention monitor system. During a shutdown phase, LIBS was performed at atmospheric pressure, for measuring the composition and fuel content of different area of the stainless-steel FTU first wall, and the titanium zirconium molybdenum alloy tiles of the toroidal limiter. These achievements underline the capability of a LIBS-based retention monitor, which complies with the requirements for JET and ITER operating in DT with a beryllium wall and a tungsten divertor. Concerning the capabilities of LIBS at pressure conditions relevant for ITER, quantitative determination of the composition of PFC materials at ambient pressures up to 100 mbar of N2, the D content could be determined with an accuracy of 25%, while for atmospheric pressure conditions, an accuracy of about 50% was found when using single-pulse lasers. To improve the LIBS performance in atmospheric pressure conditions, a novel approach is proposed for quantitative determination of the retained T and the D/T ratio. This scenario is based on measuring the LIBS plume emission at two different time delays after each laser pulse. On virtue of application of a double pulse LIBS system, for LIBS application at N2 atmospheric pressure the distinguishability of the spectra from H isotopes could be significantly improved, but further systematic research is required
Some aspects of pulsed laser deposition of Si nanocrystalline films
No full textNanocrystalline silicon films were deposited by a picosecond laser ablation
on different substrates in vacuum at room temperature. A nanocrystalline
structure of the films was evidenced by atomic force microscopy (AFM),
optical and Raman spectroscopies. A blue shift of the absorption edge was
observed in optical absorption spectra, and a decrease of the optical phonon
energy at the Brillouin zone centre was detected by Raman scattering. Early
stages of nanocrystalline film formation on mica and HOPG substrates were
studied by AFM. Mechanism of nanocrystal growth on substrate is discussed
Comprehensive optical characterization of organic thin films for OLED applications via spectroscopic ellipsometryZenodoZenodo
No full textIn this study, spectroscopic ellipsometry was employed to characterize the optical properties of 19 different organic thin films used in the fabrication of organic light-emitting diodes (OLEDs). The films were deposited via thermal evaporation onto quartz and soda lime float glass substrates coated with a SiO2 buffer layer and indium tin oxide (ITO). The analysis included a range of organic compounds, from widely studied materials such as CBP (4,4′-Bis(N-carbazolyl)-1,1′-biphenyl) to less-explored compounds such as TAZ (3-(Biphenyl-4-yl)-5-(4-tert-butylphenyl)-4-phenyl-4H-1,2,4-triazole), PO-T2T ((1,3,5-Triazine-2,4,6-triyl)tris(benzene-3,1-diyl)tris(diphenylphosphine oxide)), CzSi (9-(4-tert-butylphenyl)-3,6-bis(triphenylsilyl)-9H-carbazole), and NBphen (2,9-Dinaphthalen-2-yl-4,7-diphenyl-1,10-phenanthroline). Attention was given to the influence of substrate material on the complex refractive index - specifically, the refractive index (n) and extinction coefficient (k) - across a broad spectral range (210–1690 nm, 0.7–5.9 eV). The results reveal critical insights into substrate-dependent variations, including the presence of refractive index gradients and anisotropic optical behavior in selected organic thin films
Influence of swift heavy ions irradiation on optical and luminescence properties of YAlO single crystals
No full textOptical and luminescence properties of YAlO (YAG) single crystals preliminary irradiated by swift heavy ionswere studied. Swift heavy Xe ions with fluences ranging from 6 x 10 to 2 x 10 ions/cm were utilized for theirradiation of nominally undoped YAG single crystals. A stable strong induced absorption observed in the 200–600 nm spectral range correlates with the irradiation fluence. It is suggested that several centers areresponsible for this induced absorption in YAG single crystals and their possible origin (F-type centers) is proposed and discussed. The swift heavy ions irradiation strongly modifies the luminescence properties of YAG, namely, the excitonic emission at liquid helium temperature is drastically suppressed in heavily irradiatedcrystals
Spatial mapping of optical constants and thickness variations in ITO films and SiO2 buffer layers
No full textIn this work, we present detailed spectroscopic ellipsometry (SE) measurements across thirty indium tin oxide In2O3–SnO2 (ITO) substrates, providing insights into variations in the complex refractive index N˜ for the same commercial ITO material. This study includes an analysis of the distribution of ITO surface roughness, ITO thickness, SiO2 buffer layer thickness, and the complex refractive index of ITO including electrical resistivity and its gradient. The SE mapping, conducted over a (1.5 × 1.5) cm scan area on multiple substrates of (2.5 × 2.5) cm size, reveals uniformity in above parameters within single ITO substrate. However, substantial thickness variations in the SiO2 buffer layer along with fluctuations in the Ñ of ITO are observed across the set of substrates. Our findings underscore the importance of individually assessing each ITO substrate's optical properties prior to additional layer deposition, as this precision is essential for reliable investigations of other materials, such as organic compounds in OLEDs, in both ex-situ and in-situ studies. Additionally, this article provides comprehensive optical property data for ITO substrates consisting of soda lime float glass coated with a thin SiO2 buffer layer
Amorphous ultra-wide bandgap ZnOx thin films deposited at cryogenic temperatures
No full textCrystalline wurtzite zinc oxide (w-ZnO) can be used as a wide band gap
semiconductor for light emitting devices and for transparent or high
temperature electronics. The use of amorphous zinc oxide (a-ZnO) can be an
advantage in these applications. In this paper we report on X-ray amorphous
a-ZnOx thin films (~500 nm) deposited at cryogenic temperatures by reactive
magnetron sputtering. The substrates were cooled by a nitrogen flow through the
copper substrate holder during the deposition. The films were characterized by
X-ray diffraction (XRD), Raman, infrared, UV-Vis-NIR spectroscopies, and
ellipsometry. The a-ZnOx films on glass and Ti substrates were obtained at the
substrate holder temperature of approximately -100 oC. New vibration bands at
201, 372, and 473 cm-1 as well as O-H stretch and bend absorption bands in the
a-ZnOx films were detected by FTIR spectroscopy. Raman spectra showed
characteristic ZnO2 peaks at 386 and 858 cm-1 attributed to the peroxide ion
O22- stretching and libration modes, respectively. In addition, the films
contain neutral and ionized O2 and O2- species. The a-ZnOx films are highly
transparent in the visible light range (approx. 87%) and exhibit a refractive
index of 1.68 at 2.25 eV (550 nm). An optical band gaps is 4.65 eV with an
additional band edge absorption feature at 3.50 eV. It has been shown that the
deposition on actively cooled substrates can be a suitable technique to obtain
low temperature phases that cannot be deposited at room temperature.Comment: 24 pages, 8 figure
