Study on the Temporal and Spatial Evolution of Optical Emission From the Laser Induced Multi-Component Plasma of Tungsten Carbide Copper Alloy in Vacuum
YUAN Shu, WU Ding*, WU Hua-ce, LIU Jia-min, LÜ Yan, HAI Ran, LI Cong, FENG Chun-lei, DING Hong-bin
School of Physics, Dalian University of Technology, Dalian 116024, China
Abstract：The Laser-induced breakdown spectroscopy technique has been used for the wall diagnosis in EAST Tokamak.Improving the accuracy of LIBS analysis in a vacuumis one of the bottlenecks for further development and application. In a vacuum, laser-induced plasma evolution highly depends on time and space. Studying the spatial-temporal evolution of plasma and understanding the species’ behavior is necessary to improve the LIBS accuracy further.Considering different elements related to the first wall and diverter used in Tokamak, the sample of ternary alloy-tungsten carbide copper ((WC)70Cu30) was used in this work. Multi-component plasma was produced by nanosecond laser ablation in a vacuum with a wavelength of 1 064 nm, the pulse width of 5 ns, and power density of 6.3 GW·cm-2. The temporal and spatial resolution measurement has been achieved using a linear fibre bundle.Six lines of C Ⅰ 833.51 nm, C Ⅱ 657.81 nm, Cu Ⅰ 515.32 nm, Cu Ⅱ 512.45 nm, W Ⅰ 429.46 nm and W Ⅱ 434.81 nm were selected to analyze the emission time scales. Moreover, the element separation in space and ion acceleration phenomena were also investigated. According to the spectrally-resolved time evolution results, it was found that continuous radiation mainly occurs in the early time of 80 ns, ionic emissions are 30~300 ns, and atomic emissions are 100～1 000 ns. The spatial distribution of atoms and ions corresponding to C, Cu and W elements are all different, indicating the separated species occurs during multi-component plasma expansion. The peak position and time for the six lines have been linearly fitted to obtain the corresponding species velocity, which ranges from 4.2 to 34.9 km·s-1. The results also show that the smaller the relative atomic mass, the faster the corresponding expansion velocity. (C Ⅰ>Cu Ⅰ>W Ⅰ, C Ⅱ>Cu Ⅱ>W Ⅱ); the ion velocity is greater than its atomic velocity (C Ⅱ>C Ⅰ, Cu Ⅱ>Cu Ⅰ, W Ⅱ>W Ⅰ). The element separation in space and ion acceleration is attributed to the element mass separation effect and transient sheath acceleration, which also reveals the spatial heterogeneity property of laser-produced plasma. The results provide important information for the LIBS theoretical model and a new idea for improving the accuracy of vacuum LIBS quantitative analysis.
Key words：Laser-induced breakdown spectroscopy; Copper tungsten carbide alloy; Multicomponent plasma; Temporal-spatial evolution; Mass separation effect; Ion acceleration
袁 舒，吴 鼎，武华策，刘佳敏，吕 燕，海 然，李 聪，冯春雷，丁洪斌. 真空下激光烧蚀碳化钨铜多组分等离子体发射光谱的时空演化研究[J]. 光谱学与光谱分析, 2023, 43(05): 1394-1400.
YUAN Shu, WU Ding, WU Hua-ce, LIU Jia-min, LÜ Yan, HAI Ran, LI Cong, FENG Chun-lei, DING Hong-bin. Study on the Temporal and Spatial Evolution of Optical Emission From the Laser Induced Multi-Component Plasma of Tungsten Carbide Copper Alloy in Vacuum. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2023, 43(05): 1394-1400.
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