研究目的
Investigating the relationship between plasma temperature and the continuous Bremsstrahlung background in laser-induced breakdown spectroscopy (LIBS) for element analysis in plasma wall interaction (PWI) of fusion devices.
研究成果
The study found that Bremsstrahlung emission dominates the early stage of laser ablation and decreases exponentially over time. The intensity of spectral lines of W increases, while that of W+ increases first and then decreases. The experimental results agree with numerical predictions, showing that Bremsstrahlung emission is dominant during the early stage of plasma formation. These findings provide guidance for optimizing LIBS applications in PWI diagnosis of fusion devices.
研究不足
The study focuses on the early stage of plasma formation (up to 160 ns) and does not cover the later stages of plasma evolution. The experimental setup is limited to vacuum conditions and may not fully represent conditions in fusion devices.
1：Experimental Design and Method Selection:
A one-dimensional gas-dynamic numerical model was optimized to simulate the Bremsstrahlung emission and spectral lines of W and W+ in a nanosecond laser ablation. The model includes heat conduction equation, Euler equations, and Saha equations to describe temperature distribution, plasma plume properties, and Local Thermal Equilibrium of electrons, W atoms, W+ and W2+ ions.
2：Sample Selection and Data Sources:
Tungsten sample (>
3：5% purity) was ablated using a Q-switch Nd:
YAG pulsed laser. The plasma emission was studied using a spectrometer with an ICCD detector.
4：List of Experimental Equipment and Materials:
Q-switch Nd:YAG pulsed laser (FWHM: 8 ns, wavelength 1064 nm), tungsten sample, spectrometer (Andor iStar, SR750) with ICCD detector (Andor iStar, 340T), digital delay generator (Stanford Research Systems, DG645).
5：5).
Experimental Procedures and Operational Workflow:
4. Experimental Procedures and Operational Workflow: Laser pulses were focused onto the tungsten target surface. The plasma light emissions were guided into an optical fiber bundle and analyzed by the spectrometer. The timing of the experimental system was controlled by the digital delay generator.
6：Data Analysis Methods:
The intensity of Bremsstrahlung emission and spectral lines were analyzed as functions of time and wavelength. The relationship between plasma temperature and Bremsstrahlung emission was investigated.
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