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Laser cooling arc plasma effect in laser-arc hybrid welding of 316L stainless steel
摘要： Current laser-plasma interaction theory supports that the plasma energy e.g. electron temperature would increase by the effect of inverse bremsstrahlung (IB) absorption, when a laser beam passed through the plasma. However, in this paper, we found an interesting laser cooling arc plasma effect (LCAPE) during kilo-Watt fiber laser-TIG hybrid welding. Based on theoretical modelling and experiments, we observed that a temperature decrease of more than 5000 K at the tail of the argon plasma occurred under different process parameters during hybrid welding of 316L stainless steel. We proposed the LCAPE is caused by the laser-induced metal vapor. The mechanism mainly includes the convection cooling and enhanced radiation of the arc plasma by the metal vapor. Our findings could broaden the theory of laser-plasma interaction and provide a theoretical reference to the modulation and control of plasma in industries.
关键词： Cooling effect,Stainless steel,Laser-arc hybrid welding,Arc plasma,Fiber laser
更新于2025-11-28 14:24:20
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3D spectroscopic measurement of argon and metal vapour in MIG welding
摘要： Spectroscopic measurements for gas-metal arc (GMA) phenomena have been recently performed. The studies have reported that the metal vapour behaviour greatly affects the arc properties. However, they can be applied only to axially symmetric phenomena because of the assumption used for the measurement. GMA welding are normally performed with a travel speed, and most of the phenomena become axially asymmetric. This study constructed the simultaneous and multidirectional measurement system by 12 CCD cameras which can capture such axially asymmetric GMA phenomena. We measured the metal inert gas welding process with use of two types of narrowband interference filters for Ar I and Fe I during the one measurement, and observed axially asymmetrical intensity distributions in the globular and the spray transfer mode. We found that the globular transfer mode that is seemingly chaotic distribution can be regarded as the distribution where the deviation of Ar I is larger than Fe I from the axially symmetric double-ring distribution that consists of Ar I and Fe I.
关键词： image reconstruction,ML-EM method,CCD camera,globular transfer,interference filter,axially asymmetrical arc plasma,spray transfer,Optical emission spectroscopy
更新于2025-09-23 15:21:21
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Vacuum Arc Plasma Heated by Sub-Terahertz Radiation as a Source of Extreme Ultraviolet Light
摘要： This paper presents the results of the ?rst experimental studies of the interaction of a powerful sub-terahertz radiation with expanding highly inhomogeneous plasma of vacuum arc discharge. The tantalum plasma of a vacuum arc discharge additionally heated by the focused sub-terahertz radiation of a gyrotron, the radiation power is up to 250 kW, and the wavelength is 1.2 mm. Characteristics of the light emission in the extreme ultraviolet range are presented.
关键词： gyrotron,vacuum arc plasma,Extreme ultraviolet light,sub-terahertz radiation
更新于2025-09-23 15:21:01
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[IEEE 2018 28th International Symposium on Discharges and Electrical Insulation in Vacuum (ISDEIV) - Greifswald, Germany (2018.9.23-2018.9.28)] 2018 28th International Symposium on Discharges and Electrical Insulation in Vacuum (ISDEIV) - 2-D Lengmuir Probe Set for Diagnostics of Plasma Density Distribution and Cathode Sheath Expansion after Current Zero in a Vacuum Interrupter
摘要： Two-dimensional set of miniature Langmuir probes for the diagnostics of evolution of plasma distribution during current zero (CZ) transition in vacuum interrupter is presented. The electron saturation probe currents are traced just before and after current zero during the transient recovery voltage (TRV) rise in a gap with copper-chromium electrodes. Probe measurements are accompanied with the tracing of post-arc currents. By processing the probe current traces, the evolution of plasma density distribution as well as cathode sheath dynamics after CZ are reconstructed in real-time 2-D mode. Plasma density distribution and its dynamics during CZ transition are discussed as depended on arc parameters, such as arc current amplitude and duration, TRV rise rate and arc stabilization by axial magnetic field.
关键词： post-arc plasma,current-zero transition,high-current vacuum arc,vacuum circuit breakers,cathode sheath
更新于2025-09-09 09:28:46
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[IEEE 2018 28th International Symposium on Discharges and Electrical Insulation in Vacuum (ISDEIV) - Greifswald, Germany (2018.9.23-2018.9.28)] 2018 28th International Symposium on Discharges and Electrical Insulation in Vacuum (ISDEIV) - Vacuum-Arc Anode Phenomena: New Findings and New Applications
摘要： The vacuum arc modes from the viewpoint of anode activity have traditionally been considered as a diffuse arc, footpoints, anode spots, and an intense arc. Recent studies carried out jointly by the IHCE SB RAS and the INP-Greifswald have made it possible to identify anodic plume and anode spot type 2 as new modes of a high-current vacuum arc, specific for electrodes made of a copper-chromium composition. The anode plume appears either immediately before the anode spot of type 2, or immediately after the extinction of the anode spot of type 2. The appearance of the plume before the spot is unstable, while after the spot the plume is stable. Appearance of the plume is an indicator of the intense vapor flux of the anode material, which can reduce the breaking capacity of the vacuum circuit breaker (VCB). Implementation of the VCB operating mode free of both the anode spot type 2 and anode plume allows a more successful recovering of the electric strength of the VCB after current zero.
关键词： vacuum arc,plasma diagnostics,plasma sources,circuit breakers
更新于2025-09-09 09:28:46
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High-density cascade arc plasma sources for application to plasma windows for virtual vacuum interfaces
摘要： We develop two cascade arc plasma sources for application to plasma windows for virtual vacuum interfaces. For windowless vacuum–atmosphere separation, a compact arc discharge source having a channel diameter of 3 mm is fabricated, and an atmospheric Ar thermal plasma is generated. For an alternative differential pumping system, separating low- and high-pressure vacuum chambers, a larger arc device with an 8-mm diameter is also constructed, producing a high-density He plasma. The performances of the two cascade arcs as plasma windows are investigated. The 3-mm arc discharge generates a steep pressure gradient of Ar 100 kPa–100 Pa through the discharge channel, while the 8-mm discharge apparatus isolates the high-pressure side at 7 kPa from the lower pressure of 54 Pa. Emission spectroscopy of visible and vacuum UV radiation reveals the characteristics of the Ar and He plasmas. Spectral analysis yields a plasma temperature of around 1 eV in both discharges. Stark broadenings of the H-b and Ar I lines give an electron density of 6.5 (cid:2) 1016 cm(cid:3)3 for Ar 60 A with a gas ?ow rate of 1.0 l/min and 4.7 (cid:2) 1013 cm(cid:3)3 under a He 100-A and 0.45-l/min condition.
关键词： electron density,plasma temperature,emission spectroscopy,virtual vacuum interfaces,He plasma,cascade arc plasma sources,plasma windows,Ar thermal plasma
更新于2025-09-04 15:30:14