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Spatially-resolved uranium isotopic analysis of contaminated scrap metal using laser ablation multi-collector ICP-MS
摘要： Laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) was applied to the detailed investigation of the uranium (U) isotopic composition (234U, 235U, 236U, and 238U) of five contaminated scrap metal samples found within the European Union. Pressed pellets of the two certified U isotopic reference materials CRM U-020 and CRM U-030 were included in the measurement protocol for mass bias correction, calculation of the ion counter gains and for quality assurance. Since the investigated samples had low U content (0.15–14.3 wt%) compared to typically analysed pure U compounds (>60 wt%), the applied experimental parameters had to be adjusted. Spatially-resolved U isotopic information was obtained by line scan analysis of each sample. While other analytical techniques used typically in nuclear forensic investigations, such as g-spectrometry and thermal ionisation mass spectrometry (TIMS) yielded average U isotopic compositions of the entire sample, LA-MC-ICP-MS provided substantial added value, highlighting the inhomogeneous distribution of U isotopes within various scrap metal samples. Analysis of individual particles via secondary ion mass spectrometry (SIMS) confirmed the large range of 235U enrichment levels in heterogeneous scrap metal samples. Four out of five scrap metal samples contained 236U ((cid:1)0.05–(cid:1)0.11 wt%), indicating the presence of reprocessed U. Taken together, LA-MC-ICP-MS analysis provided fast and accurate spatially-resolved U isotopic information without consuming or altering the scrap metal samples, a key feature for nuclear forensics investigations.
关键词： nuclear forensics,Laser ablation,multi-collector ICP-MS,uranium isotopic analysis,scrap metal
更新于2025-09-23 15:21:01
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A high performance method for the accurate and precise determination of silicon isotopic compositions in bulk silicate rock samples using laser ablation MC-ICP-MS
摘要： MC-ICP-MS has become one of the most powerful analytical methods for Si isotopes in bulk liquid and solid samples in the past decade. Laser ablation provides direct sampling of solid samples, avoiding laborious chemical digestion procedures. As for powder bulk samples, the preparation of stable and homogeneous targets prior to measurements, and strategies to minimize potential matrix effects, are critical for accurate isotopic analysis. In this study, an accurate and precise method for Si isotope ratio measurements by fs-LA-MC-ICP-MS of bulk silicate rock samples was established. A new laser fusion sample preparation technique was developed to achieve fast and homogeneous fusion of silicate rock powders (including granite and granodiorite that contain abundant refractory minerals) into glasses. Compared to the pressed pellet technique, the measurement precision for fused glasses was improved ~5.7-fold. Matrix effects during Si isotopic analysis were observed when using non-matrix matched calibration protocols under normal dry-plasma instrument conditions with both ns- and fs-laser using a raster ablation mode. Matrix effects were eliminated by the addition of water vapor into the plasma, realizing accurate non-matrix matched calibration. In addition, fs-laser provided better measurement precisions, with the internal and external precisions being improved ~1.85 and ~2.4 fold compared to ns-laser at nearly equal signal intensities. Five well characterized silicate rock reference materials were analyzed using fs-LA-MC-ICP-MS calibrated against NBS-28 and BHVO-2G. Results obtained for =29Si and =30Si for these five reference materials were in agreement with previously reported values, confirming the accuracy of the proposed method.
关键词： matrix effects,Silicon isotopic analysis,water vapor addition,laser ablation MC-ICP-MS,silicate rock samples
更新于2025-09-23 15:21:01
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A Technical Look at Fetoscopic Laser Ablation for Fetal Laryngeal Surgical Recanalization in Congenital High Airway Obstruction Syndrome
摘要： Background: Congenital high airway obstruction syndrome (CHAOS) is a rare condition characterized by complete obstruction of the upper fetal airways. Left untreated, it is uniformly fatal. Ex utero intrapartum treatment (EXIT) has been used to establish a surgical airway in affected fetuses during delivery. While this procedure bene?ts those fetuses that survive to delivery, high mortality in the prenatal period necessitates earlier innovative strategies. Herein, we report a novel technique for in utero intervention. Methods: A fetoscopic intervention was performed at 28 weeks on a 35-year-old G1P0 woman with fetal CHAOS from a laryngeal obstruction measuring 11 mm in length on prenatal imaging. Under ultrasound guidance, a 3.3-mm curved fetoscope was used to access the uterine cavity through a single subcentimeter maternal skin incision. The scope was driven through the fetal oral cavity and manipulated to attain a view of the vocal cords. A subglottic obstruction was observed. A 600-micron laser ?ber was passed through the working channel of the scope and used to ablate the obstructed airway. Using the laser ?ber and a guidewire, the ablated opening was traversed with the fetoscope to the level of the carina. Results: Postoperatively, the lungs became less hyperin?ated. There was improvement in ascites and diaphragmatic eversion. At 31 1/7 weeks’ gestation, the mother experienced preterm premature rupture of membranes with active labor and the fetus was delivered through EXIT to tracheostomy. The infant was managed on mechanical ventilation and is currently thriving at home with a tracheostomy at 2 years of age. Conclusion: Fetoscopy with laser ablation of the airway obstruction is an effective prenatal management strategy that offers the potential to alter the devastating natural course of CHAOS.
关键词： fetoscopy,in utero intervention,CHAOS,laser ablation
更新于2025-09-23 15:21:01
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UV post-ionization laser ablation ionization mass spectrometry for improved nm-depth profiling resolution on Cr/Ni reference standard
摘要： Laser ablation combined with mass spectrometry forms a promising tool for chemical depth profiling of solids. At irradiations near the ablation threshold, high depth resolutions are achieved. However, at these conditions, a large fraction of ablated species is neutral and therefore invisible to the instrument. To compensate for this effect, an additional ionization step can be introduced. Double pulse laser ablation is frequently used in material sciences to produce shallow craters. We apply double pulse UV fs-Laser Ablation Ionization Mass Spectrometry to investigate the depth profiling performance. The first pulse energy is set to gentle ablation conditions, whereas the second pulse is applied at a delay and a pulse energy promoting highest possible ion yield. The experiments are performed on a Cr/Ni multi-layered standard. For a mean ablation rate of ~3 nm/pulse (~72 nJ/pulse), a delay of ~73 ps provided optimal results. By further increasing the energy of the second pulse (5–30% higher with respect to the first pulse) an enhancement of ~10 times the single pulse intensity was achieved. These conditions resulted in mean depth resolutions of ~37 and ~30 nm for the Cr and Ni layers, respectively. It is demonstrated on the thin film standard that the double pulse excitation scheme substantially enhances the chemical depth profiling resolution of LIMS with respect to the single pulse scheme. The post-ionization allows for extraordinarily low ablation rates and for quantitative and stoichiometric analysis of nm thick films/coatings.
关键词： thin layers,double pulse,depth profiling,Laser ablation,LIMS,post-ionization
更新于2025-09-23 15:21:01
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Color tunable upconversion luminescence and optical thermometry properties of mixed Gd2O3:Yb3+/Ho3+/Er3+ nanoparticles prepared via laser ablation in liquid
摘要： The mixtures of Gd2O3:Yb3+/Er3+ and Gd2O3:Yb3+/Ho3+ nanoparticles were successfully prepared via pulsed laser ablation in liquid followed by solution mixing. Under excitation of 980 nm diode laser, tunable color from green to red emission was achieved. Based on the thermal linked energy levels, the temperature sensitive upconversion emission was observed. The fluorescence intensity ratio (FIR) of I513–530 nm/I530–580 nm increased as the elevation of temperature. The absolute sensitivity and relative sensitivity were derived from temperature dependent FIR. The results show that the mixture of Gd2O3:Yb3+/Er3+ and Gd2O3:Yb3+/Ho3+ nanoparticles are not only potential candidates for multicolor upconversion luminescence but also promising optical materials for non-contact optical thermometry.
关键词： Gd2O3 nanoparticles,Color tunable emission,Pulsed laser ablation in liquid,Optical thermometry,Upconversion luminescence
更新于2025-09-23 15:21:01
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A low-temperature limit for growth of ZnO nanowires by using of laser ablation processes
摘要： The contribution deals with growth of ZnO nanowires on metal catalysts by using of pulsed laser deposition and with the influence of growth temperature. The process of nanowires preparation comprised two technological steps—both were based on pulsed laser ablation processes: (1) production of metal nanoparticles by laser ablation in liquids and (2) pulsed laser deposition of ZnO nanowires by ablation of ZnO target on substrate with metal nanoparticles. Nanoparticles from various metals (Au, Ag, Ni, Cu, Al, Mg, Zn, Sn and BiSn alloy) were prepared by pulsed laser ablation at 1064 nm in deionised water. Colloids contained metal nanoparticles were applied on Si (100) substrates, and after drying, nanoparticles served as catalysts of VLS crystallisation. Temperatures in interval 600—200 °C were experimentally compared for the nanowires growth with applied ablation laser working at 248 nm. The lowest achieved temperature value for growth of ZnO nanowires was 425–450 °C. However, among applied metals Cu and Al nanoparticles only successfully catalysed ZnO nanowires at this temperature. Properties of prepared samples were investigated by scanning electron microscopy and photoluminescence. Experimental results revealed that along with the growth temperature, selection of proper metal catalyst is also important factor for nanowires crystallisation.
关键词： Nanoparticles,Zinc oxide,Pulsed laser ablation,Nanowires,Directed growth
更新于2025-09-23 15:21:01
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Simulation studies of the laser ablation ion source at the SHIPTRAP setup
摘要： A gas-filled miniature Radio-Frequency Quadrupole (mini-RFQ) was recently implemented into the SHIPTRAP laser ablation ion source to thermalize the laser-ablated ions and thus improve production efficiency as well as sample preparation. This source provides reference ions of various elements for online experiments with the SHIPTRAP mass spectrometer. In addition, it can be used to provide long-lived rare and radioactive isotopes available only in small sample sizes for high-precision mass measurements or to study systematic uncertainties. The performance of the laser ablation ion source was simulated using the COMSOL Multiphysics modeling software package. These studies indicate that a revised mechanical geometry and an optimized RF field improve the performance significantly.
关键词： Penning traps,Surface ionization ion source,Mass spectrometry,Laser ablation ion source
更新于2025-09-23 15:21:01
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Simultaneous optimization of nanosecond laser ablation and frictional characteristics of tantalum carbide coated graphite substrates
摘要： Tantalum carbide (TaC) is a potential candidate for high temperature applications such as rocket nozzles and thrust petals. Laser surface modi?cation of such transition metal carbides imposes challenges in the selection of laser parameters to achieve controlled microstructure, reduction in porosity, surface roughness and higher wear resistance. The present research focuses on in-vestigating the e?ects of laser ablation parameters such as pulse energy, scanning speed, line spacing and their interactions on surface roughness and CoF of tantalum carbide coated graphite substrates. Regression models were developed to establish a correlation between surface roughness and coe?cient of friction along with laser parameters. The contribution of pulse en-ergy was found to be more signi?cant on CoF, whereas line spacing had a greater in?uence on the surface roughness of the TaC coatings. The optimal condition to obtain minimum surface roughness and CoF was achieved at a higher pulse energy of 250 μJ, lower scanning speed of 100 mm/s and lower line spacing of 10 μm.
关键词： Tantalum carbide,Laser ablation,Friction,Surface roughness
更新于2025-09-23 15:21:01
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Application of high power pulsed nanosecond fibre lasers in processing ultra-thin aluminium foils
摘要： This study is directed at developing a micro-scale laser scoring process and understanding the laser-material interaction in ultra-thin aluminium foils (160 ??m thickness). The research is carried out by the latest generation of nanosecond pulsed ?bre lasers manufactured by SPI Lasers. Presented comparative analysis of 70 W and 120 W laser types gives important insights for laser functionality and can provide recommendations for scalability of the process and quality assurance. High average power lasers were used to meet the requirement of high processing speed in aluminium foils. Scoring in aluminium foils was analysed using the fundamental laser-material interaction parameters that fully determine the way the material responds to the laser energy independent of the laser system. This approach permits transferring the results from the micro-scale laser process between various laser systems. Energy density and laser power density calculated for considered beam spot area at various frequencies were found to be the parameters that determine the scoring ablation depth in the range of 40 ??m–60 ??m. Microscopic examination of the ablation depth and score quality was carried out by an LED illumination 3D microscope. The SEM micrographs indicated minor growth of material debris from the ejected material.
关键词： Aluminium alloy,Scoring,Pulsed wave,Processing,Nanosecond ?bre laser,Ablation
更新于2025-09-23 15:21:01
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Engineering of high quality factor THz metasurfaces by femtosecond laser ablation
摘要： We report on the realization of high Q metasurfaces operating in the THz frequency range by femtosecond laser ablation applied to a nanometric metallic layer over a silicon substrate. Two different fabrication methods are used to develop periodic patterns whose basic elements are in form of an array of through-holes or metallic islands. The response of the resulting structures is characterized using a time-domain spectrometer in the frequency range 0.3–1.5 THz. The experimental findings are compared with the predictions of full wave electromagnetic simulations. The fairly good agreement between simulation predictions and experimental findings evidences that the proposed approach can offer a facile way to the elaboration of THz metasurfaces.
关键词： Femtosecond laser ablation,THz,High quality factor,Metasurfaces
更新于2025-09-23 15:21:01