Spectroscopy and Spectral Analysis, Volume. 43, Issue 5, 1394(2023)

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, LYU Yan, HAI Ran, LI Cong, FENG Chun-lei, and DING Hong-bin
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    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.

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    YUAN Shu, WU Ding, WU Hua-ce, LIU Jia-min, LYU 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[J]. Spectroscopy and Spectral Analysis, 2023, 43(5): 1394

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    Paper Information

    Received: Mar. 3, 2022

    Accepted: --

    Published Online: Jan. 7, 2024

    The Author Email:

    DOI:10.3964/j.issn.1000-0593(2023)05-1394-07

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