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[IEEE 2019 International Conference on Optical MEMS and Nanophotonics (OMN) - Daejeon, Korea (South) (2019.7.28-2019.8.1)] 2019 International Conference on Optical MEMS and Nanophotonics (OMN) - Monolithic integration of III-V microdisk lasers on silicon
摘要： Channel electron multiplier (CEM) and microchannel plate (MCP) detectors are routinely used in space instrumentation for measurement of space plasmas. Our goal is to understand the relative sensitivities of these detectors to penetrating radiation in space, which can generate background counts and shorten detector lifetime. We use keV -rays as a proxy for penetrating radiation such as -rays, cosmic rays, and high-energy electrons and protons that are ubiquitous in the space environment. We ?nd that MCP detectors are times more sensitive to keV -rays than CEM detectors. This is attributed to the larger total area of multiplication channels in an MCP detector that is sensitive to electronic excitation and ionization resulting from the interaction of penetrating radiation with the detector material. In contrast to the CEM detector, whose quantum ef?ciency keV -rays is found to be 0.00175 and largely independent of detector bias, the quantum ef?ciency of the MCP detector is strongly dependent on the detector bias, with a power law index of 5.5. Background counts in MCP detectors from penetrating radiation can be reduced using MCP geometries with higher pitch and smaller channel diameter.
关键词： radiation effects,Electron multipliers,gamma-ray effects,plasma measurements
更新于2025-09-23 15:21:01
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Structural dynamics in proteins induced by and probed with X-ray free-electron laser pulses
摘要： X-ray free-electron lasers (XFELs) enable crystallographic structure determination beyond the limitations imposed upon synchrotron measurements by radiation damage. The need for very short XFEL pulses is relieved through gating of Bragg diffraction by loss of crystalline order as damage progresses, but not if ionization events are spatially non-uniform due to underlying elemental distributions, as in biological samples. Indeed, correlated movements of iron and sulfur ions were observed in XFEL-irradiated ferredoxin microcrystals using unusually long pulses of 80 fs. Here, we report a femtosecond time-resolved X-ray pump/X-ray probe experiment on protein nanocrystals. We observe changes in the protein backbone and aromatic residues as well as disulfide bridges. Simulations show that the latter’s correlated structural dynamics are much slower than expected for the predicted high atomic charge states due to significant impact of ion caging and plasma electron screening. This indicates that dense-environment effects can strongly affect local radiation damage-induced structural dynamics.
关键词： plasma electron screening,radiation damage,ion caging,structural dynamics,protein nanocrystals,X-ray free-electron lasers
更新于2025-09-23 15:21:01
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Rotation of electromagnetic energy initiated by azimuthal surface waves in coaxial metal waveguides entirely filled by plasma
摘要： Azimuthal surface waves are well-known to be eigenwaves of coaxial metal waveguides entirely ?lled by plasma. The present study of electro-magnetic energy transfer complements the investigation of the wave dispersion properties carried out earlier. The angular velocity of energy transfer is analyzed as a function of the coaxial-line parameters and compared with three limiting cases. One case is a metal waveguide entirely ?lled by plasma. The second case is a metal rod placed into in?nite plasma along an external static magnetic ?eld. Finally, the third one is a thin coaxial waveguide.
关键词： azimuthal surface waves,angular velocity,coaxial metal waveguides,electromagnetic energy transfer,plasma
更新于2025-09-23 15:21:01
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EXPRESS: Potentialities of a Laser-Induced Breakdown Spectroscopy Technique in the Study of Polymer Composites
摘要： A laser-induced breakdown spectroscopy (LIBS) technique was used to evaluate the filler content in particulate epoxy–copper composites. A potential application for a direct and fast measurement of the filler in composites through the LIBS results is suggested using calibrated samples. The methodology used in this work makes possible the incorporation of LIBS as a quantitative technique for the study of particle metal filled epoxy composites, providing a method to obtain a direct estimation of the filler volume fraction.
关键词： LIBS,Laser-induced breakdown spectroscopy,epoxy composites,copper,plasma
更新于2025-09-23 15:21:01
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Temperature evolution in a pulsed CO<sub>2</sub>-N<sub>2</sub> glow discharge measured using quantum cascade laser absorption spectroscopy
摘要： This work uses in situ narrowband Quantum Cascade Laser (QCL) absorption spectroscopy to study the effect of N2 on the time evolution of gas temperature, rotational temperature and the vibrational temperatures of CO2 and CO in a pulsed glow discharge. Three colinear QCLs are used to scan three regions of about 1 cm?1 between 2179.20 and 2253.51 cm?1, including (v1, vl2 2 , v3 + 1) → (v1, vl2 2 , v3) CO2 transitions up to the asymmetric stretch level v3 = 6, as well as (vCO) → (vCO +1) CO transitions up to vCO = 1. A fitting routine is used to extract temperatures from the measured absorption spectra. The time resolved measurements are performed in CO2, admixed with up to 90% N2, with the plasma operated with a 5-10 ms on-off cycle, a discharge current of 50 mA and a pressure of around 6.7 mbar. The time evolution of the gas temperature has been measured and agrees well with the time evolution of the rotational temperature. The asymmetric stretch vibrational temperature T3 of CO2 reaches a maximum of 1060 K at 0.7 ms for pure CO2, while T3 goes up to 2250 K for a N2 content of 90% and stays constant until the plasma is switched off. Both T3 and the vibrational temperature of CO TCO show a clear non-equilibrium with respect to the rotational temperature Trot. Both do not equilibrate with the rotational temperature Trot between consecutive plasma cycles for a N2 content above 70%, although T3 and TCO always equilibrate with each other in the afterglow. The symmetric stretch and bending mode temperature T12 is elevated more with respect to the rotational temperature for increasing N2 content, while the maximum of the rotational temperature decreases for increasing N2 admixtures, which might be attributed to the energy stored in the vibrational modes of N2, CO2 and CO. Additionally, an indication of an increase in the total pressure during the plasma on-time due to heating and a subsequent decrease in the afterglow due to cooling was found for a pure CO2 plasma.
关键词： glow discharge,carbon dioxide plasma,vibrational temperature,gas temperature,quantum cascade laser
更新于2025-09-23 15:21:01
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Gain of electron orbital angular momentum in a direct laser acceleration process
摘要： Three-dimensional “particle in cell” simulations show that a quasistatic magnetic ?eld can be generated in a plasma irradiated by a linearly polarized Laguerre-Gauss beam with a nonzero orbital angular momentum (OAM). Perturbative analysis of the electron dynamics in the low intensity limit and detailed numerical analysis predict a laser to electrons OAM transfer. Plasma electrons gain angular velocity thanks to the dephasing process induced by the combined action of the ponderomotive force and the laser induced–radial oscillation. Similar to the “direct laser acceleration,” where Gaussian laser beams transmit part of its axial momentum to electrons, Laguerre-Gaussian beams transfer a part of their orbital angular momentum to electrons through the dephasing process.
关键词： orbital angular momentum,electron dynamics,magnetic field generation,Laguerre-Gauss beam,plasma
更新于2025-09-23 15:21:01
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Effects of the inductively coupled Ar plasma etching on the performance of (111) face CdZnTe detector
摘要： The effect of inductively coupled Ar plasma etching (ICP-Ar) instead of traditional Br–MeOH etching on the performance of CdZnTe detectors was studied. The optimal ICP etching parameters were determined by experiments. The XPS results indicated that the surface composition of CdZnTe etched by ICP-Ar had no obvious TeOx peak and was closer to stoichiometric ratio than that etched by Br–MeOH. The leakage current of ICP-Ar etched CdZnTe surface was significantly reduced, and the detection performance with the energy resolution was improved by 12%, as compared to Br–MeOH etched sample. Moreover, ICP-Ar etching abandoned the drawbacks of Br–MeOH by producing corrosive gases, making it safer and more environmentally friendly. Therefore, inductively coupled Ar plasma etching is expected to replace Br–MeOH etching and become an effective method for CdZnTe surface treatment.
关键词： Surface treatment,CdZnTe,ICP plasma
更新于2025-09-23 15:21:01
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Analysis of Yttria-Stabilized Zirconia by Inductively Coupled Plasma Atomic Emission Spectrometry
摘要： A method for determination of aluminum, hafnium, iron, yttrium, calcium, magnesium, and titanium by inductively coupled plasma atomic emission spectrometry (ICP-AES) is described. Conditions for the decomposition of two modifications of the analyzed material—unburnt and subjected to stabilizing firing—have been studied. It has been found that the unburnt zirconia dissolves in sulfuric acid, and the burnt sample can be converted to solution only by fusing with potassium pyrosulfate or potassium bifluoride. However, the application of these reagents leads to high values of the control experiment correction for trace impurities (at the level of tenths and hundredths of a percent). In this connection, we have studied the possibility of acid dissolution of the burnt sample under microwave decomposition, varying the qualitative and quantitative composition of the acid mixture, reaction temperature, and time to reach and maintain the required temperature. It has been found that the decomposition in the mixture of hydrofluoric and sulfuric acids (2 : 1) in the microwave system with stepwise heating of the reaction mixture ensures quantitative dissolution of the burnt sample and sufficiently low values of the control experiment correction for trace impurities. The analytical lines have been chosen taking into account their relative intensity, possible spectral overlaps, and the matrix effect in the analysis of model solutions containing 1.3 mg/cm3 Zr, 0.2 mg/cm3 Y, and from 0.2 to 20 mg/cm3 impurities. As a result, the following analytical lines have been chosen: Al II 167.079 nm and Al I 308.215 nm, Ca II 184.006 nm and 393.366 nm, Fe II 238.204 nm, Mg II 279.553 nm, Ti II 334.941 nm, Y II 371.030 nm, and Hf II 232.247 nm. The developed method for the analysis of yttria-stabilized zirconia by ICP-AES allows simultaneously determining aluminum, iron, magnesium, and titanium in the range of 0.01–1.0%; calcium, 0.02–1.0%; hafnium, 0.1–5.0%; and yttrium, 2.0–15% with a relative standard deviation of 6–30 rel % (for Al, Fe, Mg, Ti, and Ca), 2–7 rel % (Hg), and 2–4 rel % (Y). The correctness of the method is confirmed by the standard addition technique.
关键词： zirconium dioxide stabilized by yttrium dioxide,inductively coupled plasma atomic emission spectroscopy (ICP-AES),microwave sample preparation
更新于2025-09-23 15:21:01
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Laser Ablation of Stainless Steel in Water and Hexane: Characterization of Surface Modification and Nanoparticles for Various Applications
摘要： This work investigates the effect of a liquid medium on the roughness and the chemical composition of an ablated, stainless steel target, as well as on various properties of the laser-generated nanoparticles, such as absorption, hardness, and yield; in addition, some possible applications of laser ablation in both water and hexane are suggested. It is found that changing the liquid medium from hexane to distilled water not only changes the chemical composition of the target, but also reduces the mass ejected from the target by roughly 25%. Further, this change leads to a “smoother” ablation process and reduces the roughness of the target. Finally, mixed results were obtained when changing the liquid medium. Nanoparticle properties such as yield and absorption were found to be greatly affected, while mechanical properties, such as hardness, are not dependent on the liquid medium.
关键词： confined plasma,nanohardness,stainless steel,laser ablation in liquid,surface roughness
更新于2025-09-23 15:21:01
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One-step synthesis and deposition of ZnFe2O4 related composite films via SPPS route for photodegradation application
摘要： Binary spinel-type metal oxides (AB2O4) related materials, including ferrites (AFe2O4), are attractive photocatalysts thanks to their excellent visible light response for the photodegradation of organic pollutants. Currently, these materials are synthesized via conventional chemical routes suffering from long preparation duration and multistep. Solution Precursor Plasma Spray (SPPS) process is a single-step method for depositing photocatalytically active zinc ferrite-based films within several minutes. The influence of the precursor ratio on the microstructures and phase compositions of the ZnFe2O4 films was investigated by XRD and Raman analyses. In addition, two optimized ZnFe2O4 films were prepared by increasing the ZnO loading and tailoring injection pattern of the precursor solution. The surface morphologies and optical bandgap were also determined by SEM and UV-visible spectroscopy. The photocatalytic activities of the ZnFe2O4 films were evaluated through the degradation of the Orange II dye and of tetracycline hydrochloride under UV or visible light irradiation. The results show that compositional ratios and composition distribution of the ZnFe2O4 films prepared via SPPS played a key role on the photocatalytic activity. The SPPS route was demonstrated to be a promising method for the synthesis and the deposition of metal oxide (i.e. perovskite type and spinel type) films within a single-step for functional applications.
关键词： Solution Precursor Plasma Spray,Photocatalytic degradation,zinc ferrite,composite films
更新于2025-09-23 15:21:01