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Physical Characteristics of Coupled Plasma and Its Influence on Weld Formation in Hybrid Laser-Double-Arc Welding
摘要： Hybrid laser-double-arc welding (HLDAW) is an e?cient welding method with multi-heat sources comprised of two arcs and a laser beam, which is an intricate process with much randomness and uncertainty due to the mutual e?ect between multi-plasmas. Compared with double-arc welding (DAW), HLDAW can generally obtain a more stable welding process and deeper weld penetration, which is directly a?ected by the synergistic e?ect of multiple heat sources; however, the mechanism has not been systematically studied. In this study, the multi-information analysis method is adopted to study the distribution of electron temperatures, electron densities and electrical conductivity of double-arc welding (DAW) and HLDAW by utilizing synchronous radiation spectrum, high-speed photography and electrical signal sensing technology. The results indicated that the high concentration of charged particles provided a conductive channel for the two arcs to achieve a more stable welding process in HLDAW. The synergy between the laser and the arc changed the ?ow mode of the weld pool, which facilitated the molten metal ?owing toward the bottom of the molten pool. Obtaining the same melting depth, the line energy input of HLDAW was 13% lower than that of DAW; the heat a?ected zone is narrower and the grain size is smaller. The weld penetration depth was improved in HLDAW, which was 1.8 times that of DAW and 1.5 times that of pure laser welding under the laser power of 1.5 kW. The weld penetration of HLDAW increased with laser power.
关键词： hybrid laser-double-arc welding,electron density,coupled plasma,arc shape,electron temperature
更新于2025-09-19 17:13:59
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STUDY OF PROPERTIES OF LASER-INDUCED PLASMA CHANNELS FODMED BY FEMTOSECOND LASER RADIATION
摘要： Laser-induced plasma channels (LIPC) formed during the interaction of ultrashort laser pulses with argon are studied. LIPC characteristics are studied at various pressures.
关键词： laser-induced plasma channel,electron concentration,electron temperature,optical breakdown
更新于2025-09-19 17:13:59
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Laser beam self-focusing in collisional plasma with periodical density ripple
摘要： In the paper, we applied the paraxial region theory and Wentzel–-Kramers–-Brillouin approximation to study laser beam self-focusing in the interaction of laser and collisional plasma with periodical density ripple. The results have shown that, under the influence of collision nonlinear effect, laser presents stable self-focusing, self-defocusing, and oscillational self-focusing in the plasma. Besides, the parameters of plasma with periodical density ripple have a greater impact on the effect of self-defocusing and oscillational self-focusing than stable self-focusing. In certain conditions, beam self-defocusing and oscillational self-focusing would decline and even disappear, and stable self-focusing would further be strengthened. Hence, selecting a suitable periodic plasma system is advantageous for separating self-defocusing and oscillational self-focusing, and for the formation of a more stable collisional self-focusing.
关键词： self-focusing,dielectric function,Collisional plasma,periodical density ripple,electron temperature
更新于2025-09-19 17:13:59
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Comparative study of electron temperature in cascaded arc Ar/N <sub/>2</sub> plasma using laser Thomson scattering combined optical emission spectroscopy approach
摘要： The expanding cascaded arc Ar/N2 plasma has been investigated by both the active and passive optical diagnostic technologies. In the investigation, the laser Thomson scattering (LTS) and optical emission spectroscopy (OES) have been adopted to measure electron temperature (Te) and electron excitation temperature (Texc), respectively. The LTS measurements show that a remarkable nonlinear behavior of Te as a function of the N2/(Ar + N2) ratio is found, which is caused by the collective interaction between the superelastic collision and the electron-impact excitation. The superelastic collisions by the highly excited vibrational nitrogen molecules can effectively heat the free electrons, while the electron kinetic energy can be transferred to N2 molecular internal energy via the electron impact with N2 in the ground state. The difference between Texc and Te demonstrates that the cascaded arc Ar/N2 plasma significantly deviates from the local thermodynamic equilibrium. This would be useful for improving our further understanding of nonequilibrium plasma and extending applications of the cascaded arc Ar/N2 plasma.
关键词： cascaded arc Ar/N2 plasma,local thermodynamic equilibrium,laser Thomson scattering,electron temperature,optical emission spectroscopy
更新于2025-09-19 17:13:59
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Three-dimensional measurements of plasma parameters in an inductively coupled plasma processing chamber
摘要： Inductively coupled plasmas (ICPs) are extensively used for materials processing and microelectronics fabrication. However, their electromagnetic properties have not been fully characterized. In this regard, we have performed fully three dimensional (3D), time dependent measurements of the magnetic ?eld, electron density, and electron temperature for an ICP sustained in argon in an industrial reactor designed for plasma etching in microelectronics fabrication. These measurements were compared to modeling results. The plasma was generated using pulsed power delivered at 2 MHz by a planar coil. The magnetic ?eld was measured using a three axis magnetic probe at 15 366 locations throughout the plasma volume during the H-mode portion of the pulse at temporal intervals of 2 ns. A swept Langmuir probe was used to measure plasma parameters at the same locations. The plasma density measurement was calibrated with line-integrated densities obtained using a 96 GHz interferometer. During a single radio frequency (RF) cycle, the 3D current density [derived from Be~r; tT]is initially maximum just below the coil and moves downward toward the center of the chamber. Isosurfaces of current are nearly symmetric toroids. The total electric ?eld, space charge ?eld, and inductive electric ?eld were derived and used to calculate the dissipated power, plasma current, and Poynting ?ux. Computer modeling of the experiment reproduces the phase dependent behavior. Animations showing the time dependent 3D measurements are presented in the supplementary material.
关键词： plasma etching,electron density,magnetic field,electron temperature,microelectronics fabrication,Inductively coupled plasmas
更新于2025-09-16 10:30:52
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Spectral characteristics of laser-induced plasma under the combination of Au-nanoparticles and cavity confinement
摘要： To enhance the emission spectrum intensity of laser-induced plasma, a method of combining cavity-enhanced laser-induced breakdown spectroscopy (LIBS) with nanoparticles-enhanced LIBS (NELIBS) was proposed. In this paper, the brass with Au-nanoparticles deposited on the surface is placed under the condition of cavity confinement and cavity-free confinement, and the differences between various performances are analyzed. The experimental results show that spectral line enhancement effect is the best when cavity confinement diameter is 5 mm. When cavity-enhanced LIBS is combined with NELIBS, the plasma intensity is effectively enhanced, and the enhancement factor is up to 20.24 (Cu I 515.4 nm); signal-to-noise ratio (SNR) is improved significantly, and it reaches 337.21 when pulse energy is 60 mJ. Electron temperature is in the range of 12,040–14,260 K and electron density is increased, the ability of detect trace elements is greatly improved.
关键词： Cavity confinement,Electron temperature,LIBS,SNR,Au-nanoparticles
更新于2025-09-16 10:30:52
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Effects of plasma electron temperature and magnetic field on the propagation dynamics of Gaussian laser beam in weakly relativistic cold quantum plasma
摘要： Self-focusing of Gaussian laser beam has been investigated in quantum plasma under the effect of applied axial magnetic field. The nonlinear differential equation has been derived for studying the variations in the beam-width parameter. The effect of initial plasma electron temperature and the axial magnetic field on self-focusing and normalized intensity are studied. Our investigation reveals that normalized intensity increases to tenfolds where quantum effects are dominant. The normalized intensity further increases to twelvefolds on increasing the magnetic field.
关键词： electron temperature,weakly relativistic,Gaussian,self-focusing,Cold quantum plasma
更新于2025-09-12 10:27:22
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Variable location channels to improve efficiency and precision for direct ? <i>T</i> <sub/><i>e</i> </sub> measurements and high spatial resolution <i>T</i> <sub/><i>e</i> </sub> -profile measurements using electron cyclotron emission
摘要： Electron cyclotron emission (ECE) diagnostics that use variable location channels based on yttrium iron garnet (YIG) bandpass filters improve the precision and the efficiency of measurements of electron temperature (Te) profiles and fluctuations (δTe). These variable frequency filters were substituted for fixed frequency filters in the intermediate frequency section to achieve the required higher resolution over a target radial range, just before the experiment. Here, we present the proof-of-principle for high temporal resolution measurement of the electron temperature gradient, via real-time slewing of a YIG filter for relocation of an ECE channel during a long pulse. The key component is the application of YIG tunable filters with their narrow bandwidth and capability for a high slew rate of their center frequency. This application permits fast relocation of the ECE channels for direct measurement of the gradient and close spacing of channels to investigate the magnetic island’s dynamic behavior.
关键词： Electron cyclotron emission,YIG bandpass filters,electron temperature gradient,high spatial resolution
更新于2025-09-10 09:29:36
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Investigation on the dynamic characteristics of LIBS for heavy metal Mn in liquid matrix
摘要： Laser-induced breakdown spectroscopy in composition analysis of materials has many advantages over other analytical methods.Based on our Laser Induced Breakdown Spectroscopy (LIBS) survey system of heavy metals in the mixed solution and the optimum experimental parameters, we measured the integrated intensities of partial spectral lines of Mn when the ICCD gate delay time and the sample ?ow rate were ranged from 500ns to 2500ns, 35ml/min to 55ml/min respectively. With increasing the time delay, the electron temperature of the plasma decreases gradually, the electron density decreases ?rstly,then the change amplitude tends to be ?at.As the ?ow rate continue increasing,the electron temperature of plasma increases ?rstly, then the change tends to be ?at, the electron density increase gradually.The element particle density ratio of Mn at ?rst ionization state to ground state and Mn at ?rst ionization state are also obtained respectively. Finally, by comparing the experimental value of spectral line intensity ratio of Mn with the calculated value, the nonexistent conditions of local thermal equilibrium and self-absorption of laser plasma are veri?ed.It provides the suppuration for forward quantitative analysis of the trace heavy metal elements in liquid matrix.
关键词： Liquid matrix,Laser induced breakdown spectroscopy,Elements particle density ratio,Electron temperature,Electron density
更新于2025-09-09 09:28:46
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Non-equilibrium photoexcited carrier effects in a graphene-based Josephson junction
摘要： We studied the superconducting proximity effect under photoexcitation by illuminating a superconductor/monolayer graphene/superconductor (SGS) Josephson junction with monochromatic light at a wavelength of 1.31 lm. Although the critical current Ic can be controlled by the irradiation power P, its variation cannot be explained by modi?cation of the carrier density, which has been reported for semiconductor-based Josephson junctions. The estimated electron temperature of gra- phene is proportional to Pd, where d ’ 1=3. This relation clearly indicates that photogenerated non- equilibrium carrier dynamics are responsible for the variation of Ic with P. We suggest that the SGS junction can directly mediate interactions between the optical ?eld and the superconducting state.
关键词： electron temperature,photoexcitation,critical current,graphene,Josephson junction,superconducting proximity effect
更新于2025-09-09 09:28:46