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[IEEE 2018 9th International Conference on Ultrawideband and Ultrashort Impulse Signals (UWBUSIS) - Odessa, Ukraine (2018.9.4-2018.9.7)] 2018 9th International Conference on Ultrawideband and Ultrashort Impulse Signals (UWBUSIS) - The Action of Ultra-Short Super-Powerful Radio Pulses on the Earth's Atmosphere and Ionosphere
摘要： Numerical simulations of disturbances in the electron temperature and density arising from the action of ultra-short super-powerful radio pulses with different durations and powers on the Earth's atmosphere and ionosphere are presented. It is demonstrated that the electron density in the 30–60 km altitude range can be increased by 12 orders of magnitude, while the electron temperature shows an increase of the order of 10 to 100 times. The pulse durations and powers needed to create artificial ionized layers have been estimated.
关键词： ultra-short radio pulse,disturbances,numerical simulation,atmosphere,electron temperature,ionosphere,super-powerful radio pulse,electron density
更新于2025-09-23 15:21:21
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Experiment and simulation calculation of micro-cavity dielectric barrier discharge
摘要： In order to study the discharge mechanism and discharge parameters evolution of micro-cavity dielectric barrier discharge(MDBD), an experimental platform based on the dielectric panel surface grid micro-structure electrode device was built. Discharge equivalent circuit of the MDBD was established based on the deep analysis of the discharge physical process and experimental results. Then, using Matlab/Simulink and BOLSIG+ software， we solved the Kirchhoff’s voltage equation, Boltzmann equation and the electronic continuity equation to obtain the variation of the discharge characteristic parameters, including air gap voltage, the dielectric surface voltage, the electron density and the electron temperature. The results show that the gas gap voltage and dielectric surface voltage are decreased slightly during discharge, the electron temperature and electron density are consistent with the variation of discharge current. The maximum electron temperature is about 3.0eV, the average value is about 1.6eV, and its value is lower than the conventional dielectric barrier discharge(DBD).
关键词： Micro-cavity,Electron Temperature,Dielectric Barrier Discharge,Gas Gap Voltage,Electron Density
更新于2025-09-23 15:21:21
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Investigation into the Effect of Increasing Target Temperature and the Size of Cavity Confinements on Laser-Induced Plasmas
摘要： In this work, the effect of the sample temperature on the magnesium (Mg) and titanium (Ti) plasmas generated by a Q-switched Neodymium-doped Yttrium Aluminum Garnet (Nd:YAG) laser operating at its fundamental wavelength of 1064 nm has been investigated. We observed that increasing the sample temperature significantly enhanced the emission intensities of the plasmas. Comparing the emission peak intensities of the case of 100°C to the case of 300°C, we recorded a substantial enhancement of the peak intensities of the latter compared to the former. From these results it can be observed that increasing the sample temperature has a significant effect on the emission intensities of the plasmas. We also studied the plasma dynamics and found that increasing the sample temperature also decreases the air density around the Mg sample surface. The reduction in the air density resulted in a decrease in the radiation process and lowers collision probability. Furthermore, as the plasma expands, the plasma pressure also decreases. In addition, we also employed circular and square cavities to confine the titanium plasma, and investigated the effect of the sizes of the circular and square cavities on the titanium plasma. We observed a general improvement in the emission intensities with both the circular and square cavities and attributed this improvement to the plasma compression effect of the shock waves produced by the plasma within the cavities.
关键词： electron temperature,LIBS,Mg-alloy,electron density,cavity confinement,Ti-alloy
更新于2025-09-23 15:21:01
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Investigation on the effects of laser parameters on the plasma profile of copper using picosecond laser induced plasma spectroscopy
摘要： Laser induced plasma generation and characterization, affected by laser parameters and sample physical properties, represent important phenomena in many fields of applications. In this work, we present new studies on the effects of an appropriate combination of laser wavelengths and pulse energies on the generated plasma characterization using a single shot picosecond Nd:YAG laser. The plasma plume of a pure copper sample has been generated by laser induced plasma spectroscopy (LIPS) using a single shot 170 ps laser pulse with wavelengths (266, 355, 532 and 1064 nm) and varying laser fluence (10–41 J/cm2). The spectral intensities of Cu I 324.75, 327.39, 515.32 and 521.82 nm have been observed. The plasma electron temperature and density have been determined from the Boltzmann plots and Stark-broadening profiles of the plasma spectral lines, respectively, assuming the local thermodynamic equilibrium (LTE) condition. It has been found that the electron temperature and electron density values increase from around 10,000 to 20,000 K and around 2 × 1017 to 1.5 × 1018 cm?3, respectively, with the increase in the laser wavelength and pulse fluence gradually. These observations can be understood due to the variations of mass-ablation rates, inverse-Bremsstrahlung, and photo-ionization with the studied pulse wavelength and pulse energy. The obtained results explore the opportunity to control specific generated plasma parameters by applying proper picosecond pulse parameters which can be considered in many fields of material science spectroscopic analysis and control the plasma interaction dynamics.
关键词： Stark-broadening,Picosecond,Boltzmann plot,Electron temperature,LTE,Laser induced plasma spectroscopy,Copper,Electron density,Plasma plume,LIPS
更新于2025-09-23 15:21:01
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Evaluation of electron temperature and electron density of laser-ablated Zr plasma by Langmuir probe characterization and its correlation with surface modifications
摘要： The plasma parameters of laser-ablated Zirconium (Zr) using a Langmuir probe technique have been investigated by employing a Q-switched Nd:YAG laser (532 nm, 6 ns) at various irradiances ranging from 8.6 to 15.5 GW/cm2. All the measurements have been performed under an ultra-high vacuum condition while keeping the probe at a fixed distance of 4 mm from the target. By varying the biasing voltages from 1 to 75 V, the corresponding values of electric currents are measured by the probe on the oscilloscope. Laser-induced Zr plasma parameters such as electron temperature, electron number density, plasma potential, Debye length, and thermal velocity have been evaluated from I–V characteristic curves of Langmuir probe data. It is found that both the electron temperature and thermal velocity of Zr plasma reveal an increasing trend from 18 to 41 eV and 2.8 × 108 to 4.3 × 108 cm/s, respectively, with increasing laser irradiance which is attributed to more energy deposition and enhanced ablation rate. However, the electron number density of Zr plasma exhibits a non-significant increase from 6.5 × 1014 to 6.7 × 1014 cm?3 with increasing irradiance from 8.6 to 10.9 GW/cm2. A further increase in irradiance from 12 to 15.5 GW/cm2 causes a reduction in the number density of Zr plasma from 6.1 × 1014 to 5.6 × 1014 cm?3 which is attributed to the formation of thick sheath, ambipolar electric field, and laser-supported detonation waves (Shock front). Scanning electron microscope analysis has been performed to reveal the surface morphology of irradiated Zr. It reveals the formation of cracks, ridges, cones, and grains. It was observed at high irradiances the ridges are vanished, whereas cones and cracks are dominant features. By controlling plasma parameters, surface structuring of materials can be controlled, which has a vast range of applications in the industry and medicine.
关键词： electron temperature,Langmuir probe,laser-produced plasma,plasma parameters,Electron number density
更新于2025-09-23 15:19:57
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[IEEE 2019 IEEE Pulsed Power & Plasma Science (PPPS) - Orlando, FL, USA (2019.6.23-2019.6.29)] 2019 IEEE Pulsed Power & Plasma Science (PPPS) - Laser Thomson Scattering Diagnostics for Streamer Discharge in HE Gas
摘要： Streamer discharge plasma, a type of non-thermal plasma, has received global attention as a source of reactive radicals, and is used for many applications such as ozone generation, decomposition of NOx and other gas pollutants, cleaning water, disinfection, deodorization, and medical applications. The tip of streamer discharge, known as the streamer head, in particular contributes to radical production. The peak electric field is located on the streamer head on the axis of symmetry of the discharge, likely resulting in many radical types. Very remarkable results in NO removal efficiency and superior ozone generation yield performed by streamer discharge have reported. Improving gas treatment methods requires understanding of physical characteristics of streamer discharge and streamer head, for example, electron temperature and electron density. This study investigates characteristics of streamer discharge by observing the propagation process of streamer head in a needle to conic electrode with positive voltage using a high speed gated emICCD camera. Then, incoherent laser Thomson scattering (LTS) diagnostic for streamer discharge and streamer head with positive voltage was performed. LTS diagnostic is considered to be the most reliable technique measuring electron temperature and density in plasma simultaneously. In addition, LTS diagnostic has high resolution temporally and spatially, therefore, LTS diagnostic can measure location dependence of electron temperature and density in streamer discharge including streamer head. The measurement point was 1 mm and 2 mm from tip of the high voltage needle electrode, and Thomson scattering signals were measured at the point of initial phase of streamer head propagation. In the results, electron temperature of streamer discharge was 4 to 6 eV, electron density of streamer discharge was 1021 m-3 order. This study has proven that LTS diagnostic can measure electron temperature and density in streamer discharge plasma.
关键词： Streamer discharge,Electron temperature,Laser Thomson scattering,Non-thermal plasma,Electron density
更新于2025-09-23 15:19:57
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Optical control of layered nanomaterial generation by pulsed-laser ablation in liquids
摘要： Pulsed-laser ablation in liquids capitalizes on combining chemical and optical control to rapidly generate size, composition, and phase-controlled nanostructures, without the need for surfactants. Very high temperatures, which we determined to be ca. (8,400 ± 1,300) K, pressures, and ion densities exist in the laser-induced liquid-confined plasma. These unique conditions, coupled with the rapid cooling during which nanoparticles are formed, permitted access to new extreme regions of materials’ phase diagrams. This way, we produced metastable layered copper and zinc hydroxide-based nanocrystals with interesting physical properties that can serve as precursors for two-dimensional inorganic semiconductor nanomaterials.
关键词： LTE spectra,optical control,electron temperature,layered nanocrystals,Pulsed-laser ablation in liquids,laser-induced plasma
更新于2025-09-23 15:19:57
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Characteristics of laser induced discharge tin plasma and its extreme ultraviolet radiation
摘要： In this paper, a CO2 laser induced discharge plasma extreme ultraviolet (EUV) source experimental device was established. The optical emission spectroscopy was used to diagnose the characteristics of the plasma, and the evolution of electron temperature and electron density with time was obtained. The in?uence of discharge voltage on plasma parameters was analyzed and discussed. The EUV radiation characteristics of the plasma were investigated by self-made grazing incidence EUV spectrometer. The EUV radiation intensity and conversion ef?ciency were discussed.
关键词： laser induced discharge plasma,extreme ultraviolet (EUV) radiation,electron temperature and density,optical emission spectroscopy
更新于2025-09-23 15:19:57
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Optimization of self-consistent approach for quantum cascade laser using shooting method and particle swarm optimization
摘要： We present a numerical optimization approach to simulate the output characteristics of a mid-infrared quantum cascade laser, taking into account the effect of subband electron temperature (Tei). The shooting method is used to simplify the calculation. The results give accurate subband electron temperatures when the external electric field is above the threshold. The results of the calculations are consistent with experimental results, thereby confirming that consideration of the subband electron temperature can improve our understanding of quantum cascade lasers and help guide future experimental work.
关键词： electron temperature,quantum cascade laser,infrared,shooting method
更新于2025-09-23 15:19:57
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Anti-Stokes Emission from Hot Carriers in Gold Nanorods
摘要： The origin of light emission from plasmonic nanoparticles has been strongly debated lately. It is present as the background of surface enhanced Raman scattering, and, despite the low yield, has been used for novel sensing and imaging application because of its photostability. While the role of surface plasmons as an enhancing antenna is widely accepted, the main controversy regarding the mechanism of the emission is its assignment to either radiative recombination of hot carriers (photoluminescence) or electronic Raman scattering (inelastic light scattering). We have previously interpreted the Stokes shifted emission from gold nanorods as the Purcell effect enhanced radiative recombination of hot carriers. Here we specifically focused on the anti-Stokes emission from single gold nanorods of varying aspect ratios with excitation wavelengths below and above the inter-band transitions threshold while still employing continuous wave lasers. Analysis of the intensity ratios between Stokes and anti-Stokes emission yields temperatures that can only be interpreted as originating from the excited electron distribution and not a thermally equilibrated phonon population despite not using pulsed laser excitation. Consistent with this result as well as previous emission studies using ultrafast lasers, the power-dependence of the upconverted emission is nonlinear and gives the average number of participating photons as a function of emission wavelength. Our findings thus show that hot carriers and photoluminescence play a major role in the upconverted emission.
关键词： surface plasmon resonance,anti-Stokes photoluminescence,interband transition,intraband transition,hot electron temperature,gold nanoparticle
更新于2025-09-19 17:15:36