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The non-uniformity and transient nature of laser-produced plasma are critical factors that affect the analysis of the extreme ultraviolet spectra of highly charged ions and the diagnosis of plasma states. This paper systematically investigates the characteristics of extreme ultraviolet radiation and the hydrodynamic evolution of laser-produced nickel plasmas from two perspectives: high-spatio-temporal-resolution extreme-ultraviolet spectroscopic measurement and radiation hydrodynamics simulation. The consistency between the four-band experimental spectra and their theoretically simulated spectra confirms the accuracy of the atomic structure parameters and plasma state parameters. We also analyze the significant contribution of the 3d-4f double-excited state radiation to the spectral profile and discuss the influence of the self-absorption caused by plasma opacity on the characteristics of extreme ultraviolet radiation. The findings are crucial for accurately understanding the characteristics of extreme ultraviolet radiation, the hydrodynamic evolution, and the application of medium- and high-Z laser-produced plasma as a pulsed short-wavelength light source.
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We introduce a method for the analysis and simulation of transient images of laser-produced plasma (LPP) plumes. This method comprises three steps: (i) calculating the two-dimensional distribution of plasma parameters using a radiation hydrodynamics model, (ii) constructing radiation paths through ray tracing, and (iii) solving the radiation transport equation along these paths. In our simulations, we have meticulously considered factors that could influence the imaging results, including the quantum efficiency to different radiation wavelengths, the imaging lens' transmittance, the target surface's reflectivity, and the absorption, emission, and scattering quantum effect of the detector processes occurring in the plasma. We applied this method to analyze and simulate the transient images of aluminum plasma plumes in a background air environment at a pressure of 2000â Pa. The results demonstrate that our method not only produces simulated images that align with experimental results but also provides a reliable distribution of plasma state parameters and clearly identifies the ion species radiating in different bands. Given its capability in transient image reconstruction and its adaptability as a tool for spectral simulation and analysis of LPPs, we believe this method holds significant potential for spectral diagnostics in fields such as laser-induced breakdown spectroscopy, extreme ultraviolet lithography sources, and high-energy-density physics, among others.
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We developed a post-processing optical imaging model based on two-dimensional axisymmetric radiation hydrodynamics. Simulation and program benchmarks were performed using laser-produced Al plasma optical images obtained via transient imaging. The emission profiles of a laser-produced Al plasma plume in air at atmospheric pressure were reproduced, and the influence of plasma state parameters on radiation characteristics were clarified. In this model, the radiation transport equation is solved on the real optical path, which is mainly used to study the radiation of luminescent particles during plasma expansion. The model outputs consist of the electron temperature, particle density, charge distribution, absorption coefficient, and corresponding spatio-temporal evolution of the optical radiation profile. The model helps with understanding element detection and quantitative analysis of laser-induced breakdown spectroscopy.
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The radiation and dynamic properties of C VI, C V, Si VI and Si V ions from laser-produced SiC plasmas in a vacuum are studied both experimentally and theoretically. The EUV emission spectra of SiC plasmas are measured using the spatio-temporally resolved laser-produced plasma spectroscopy technique. To explore the dynamic evolution of highly-charged ions in such plasmas, an extended radiation hydrodynamics model is developed. The comparison of theoretical and experimental time-space evolved spectral profiles provides the temporal evolution of plasma temperature and electron density, the distribution of various transient ions and their velocities. The results show that the present radiation hydrodynamics model for a multi-element target reflects the dynamic evolution processes of their laser-produced plasmas, which make it an effective tool for plasma diagnostics.
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We present a simplified radiation hydrodynamic model based on the fluid dynamic equations and the radiative transfer equation, which can be used to investigate the radiation properties and dynamics evolution of highly charged ions in a laser-produced plasma in vacuum. The outputs of the model consist of the evolution of the electron temperature, atom, and ion density, and the temporal and spatial evolution of various transient particles in plasma, as well as the simulated spectrum related to certain experimental conditions in a specified spectral window. In order to test the model and provide valuable experimental feedback, a series of EUV emission spectra of silicon plasmas have been measured using the spatio-temporally resolved laser produced plasma technique. The temporal and spatial evolution of the plasma is reliably reconstructed by using this model.
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A laser induced breakdown spectroscopy experiment was carried out using Nd:YAG laser in air, and time-resolved spectra were measured. Based on local thermodynamic equilibrium assumption, a method used to simulate LIBS spectra is proposed. A LIBS spectrum of air in the wavelength range of 700~900 nm was simulated using this method. A good agreement between experiment and simulation was obtained, and moreover, the relative concentrations of the N, O and Ar in air were obtained.
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Information on pigment sizes in mural samples is a key factor in determining the suitable processes of possible restoration and conservation on ancient murals and is also significant for the investigation of a mural's historic value and analysis of its technical process. Thus, in this paper, the green painted layers composed of different pigment sizes were analyzed by laser-induced breakdown spectroscopy. First, a parametric study was undertaken to optimize the LIBS signal to noise ratio and decrease fluctuations. Then, the variation of LIBS signal with pigment size was studied on simulated mural samples. Finally, a classifiable model of pigment sizes was built by coupling with the PCA method and was successfully applied to classify pigment sizes on real mural pieces.
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Large-area horizontal-aligned ZnO nanotubes (ZNTs), TiO2 nanotubes (TNTs), TiO2-ZnO core-shell nanotubes (TZNTs) and ZnO-TiO2 core-shell nanotubes (ZTNTs) were successfully synthesized by electrospinning combined with pulsed-laser deposition. The morphology, structure, and composition of the samples were characterized by scanning electron microscopy, high-resolution transmission electron microscopy, and Raman spectroscopy. The photoluminescence (PL) spectra of these samples indicate that the addition of a TiO2 layer greatly decreases the recombination of photogenerated carriers in the heterojunction nanotubes. The photodetectors (PDs) were fabricated by assembling horizontally ordered nanotubes on the gold interdigital electrode, and their ultraviolet (UV) detection performances were compared. The test results at room temperature show that the PD with aligned ZTNTs have the best UV response and a short response recovery time. In addition, the performance of ZTNT PDs and TZNT PDs are further improved under heating. The photo/dark current ratio, responsivity (Rλ), detectivity (D*), and external quantum efficiency (EQE) of ZTNTs increased to 388, 450 uA·W-1, 1.1 × 1010 cm·Hz1/2·W-1, and 0.15%, respectively, under the condition of 365 nm UV radiation with a power density of 4.9 mW·cm-2 and a 1 V bias at 90 °C. The UV response mechanism and structural superiority of the horizontally ordered coaxial heteronanotube were also discussed. In addition, this work provides an important method for the design of other ordered nanomaterials and structures, which have a wide range of applications in the fields of sensors, transistors, transparent flexible electrodes, and other multifunctional devices.
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Spectra of return strokes for artificial triggered lightning were obtained by optical multi-channel analyzer (OMA) in Shandong region. Compared with previous spectra of natural lightning, additional lines of ArI 602.5 nm and ArII 666.5 nm were observed. Under the model of local thermodynamic equilibrium, electronic temperatures of the lightning channel plasma were obtained according to the relative line intensities. Meanwhile, with semi-empirical method the electron density was obtained by Halpha line Stark broadening. In combination with plasma theory, electrical conductivity of the lightning channel has been calculated for the first time, and the characteristic of conductivity for lightning channel was also discussed. The relation between the electrical conductivity of channel and the return stroke current was analyzed, providing reference data for further work on computing return stroke current. Results show that the lightning channel is a good conductor, and electrons are the main carrier of channel current. The brightness of artificial triggered lightning channel is usually higher than that of natural lightning, and its current is smaller than that of the natural lightning.