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Repulsive magnetic field–assisted laser-induced plasma micromachining for high-quality microfabrication
摘要： Surface micro-/nanostructures are widely used in the fabrication of various functional microsystems. Laser-induced plasma micromachining can greatly improve surface quality in terms of recast layers and thermal defects compared with laser direct writing. Magnetic field has the ability to constrain plasma diffusion and can ensure the stability of laser-induced plasma processing. This paper compares the effects of laser direct–writing processing and laser-induced plasma processing of single-crystal silicon at the micro-/nanoscale, and emphatically analyzes the material removal mechanism of repulsive magnetic field–assisted laser-induced plasma micromachining. It is shown that the volume of the laser-induced plasma was constrained under the influence of Lorentz force, a high-quality smooth microgroove without thermal defects was obtained, and its line width was reduced by 30%.
关键词： Laser-induced plasma micromachining,Magnetic confinement,Thermal defects,Micro-/nanofabrication
更新于2025-11-21 11:24:58
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[IEEE 2019 International Conference on Microwave and Millimeter Wave Technology (ICMMT) - Guangzhou, China (2019.5.19-2019.5.22)] 2019 International Conference on Microwave and Millimeter Wave Technology (ICMMT) - Design of an Ultra-Wideband Tightly Coupled Dipole Array
摘要： The superconducting stellarator Wendelstein 7-X is currently being commissioned. First plasmas are expected for the second half of 2015. W7-X is designed to overcome the main drawbacks of the stellarator concept and simultaneously demonstrate its intrinsic advantages relative to the tokamak—i.e., steady-state operation without the requirement of current drive or stability control. An elaborate optimization procedure was used to avoid excessive neoclassical transport losses at high plasma temperature, while simultaneously achieving satisfactory equilibrium and stability properties at high β in combination with a viable divertor concept. In addition, fast-ion confinement must be consistent with the requirements of alpha-heating in a power plant. Plasma operation of Wendelstein 7-X follows a staged approach following the successive completion of the in-vessel components. The main objective of Wendelstein 7-X is the demonstration of steady-state plasma at fusion relevant plasma parameters. Wendelstein 7-X will address major questions for the extrapolation of the concept to a power plant. These include divertor operation at high densities, plasma fueling at high central temperatures, avoiding impurity accumulation, and an assessment of the effect of neoclassical optimization on turbulent transport and fast-ion confinement. A power plant concept based on an extrapolation from Wendelstein 7-X, the helical advanced stellarator, has been developed.
关键词： Fusion power plant,steady-state magnetic confinement,stellarator
更新于2025-09-23 15:21:01
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Brazing, Laser, and Electron-Beam Welding of Additively Manufactured GRCop-84 Copper for Phased Array Lower Hybrid Launchers
摘要： Recent advances in selective laser melting 3-D printing technology allow additive manufacturing of lower hybrid current drive (LHCD) RF launchers from a new material, Glenn Research Copper 84 (GRCop-84), a Cr2Nb (8 at. % Cr, 4 at. % Nb) precipitation hardened alloy, in configurations unachievable by conventional machining. Cr2Nb crystals pin grain boundaries within the copper matrix resulting in high tensile strength and resistance to annealing at elevated temperatures. Brazing, laser, and electron-beam welding (EBW) techniques are explored for joining a thin-walled GRCop-84 waveguide with zero porosity and minimal internal surface roughness. GRCop-84 wets well with the silver solder, CuSil, and Cusil-ABA brazes, once the durable surface oxide is mechanically removed. GRCop-84 melt pool size and flow during EBW is reduced compared to oxygen-free copper (OFC). Pulsed laser and e-beam welding maintains the Cr2Nb precipitate size; precipitate coarsening occurs in conduction mode e-beam welding.
关键词： joining processes,fusion reactor design,magnetic confinement,Annealing,tokamaks,copper alloys,melt processing,materials processing,phased arrays,waveguide
更新于2025-09-23 15:21:01