研究目的
Investigating the expansion dynamics and chemical evolution of filament-produced uranium (U) plasmas for remote detection of materials.
研究成果
The study successfully characterized the expansion dynamics and chemical evolution of filament-produced U plasmas, revealing a cylindrical plasma plume morphology with plume splitting into slow and fast moving components. The co-existence of U atoms and U oxide molecules in the plasma was attributed to low-temperature plasma conditions during filament ablation. The findings contribute to the understanding of filament ablation for remote detection applications.
研究不足
The study is limited to laboratory settings and may not fully replicate conditions in real-world standoff detection scenarios. The intensity clamping effect during filament generation may limit the peak intensities available for ablation.
1：Experimental Design and Method Selection:
Ultrafast laser filaments were generated in the laboratory by loosely focusing 35 femtosecond (fs), 6 milli Joule (mJ) pulses in air. Two-dimensional spectrally-integrated and time-resolved imaging was performed to study hydrodynamics and evolution of U atomic and UO molecular emission in filament-produced U plasmas.
2：Sample Selection and Data Sources:
The target material for ablation was a natural U metal sample (0.7% 235U and 99.3% 238U). The target was housed in a cubic vacuum chamber filled with air at 700 Torr pressure.
3：7% 235U and 3% 238U). The target was housed in a cubic vacuum chamber filled with air at 700 Torr pressure.
List of Experimental Equipment and Materials:
3. List of Experimental Equipment and Materials: A fs Ti:Sapphire laser system (Coherent Astrella) with ~ 800 nm wavelength and ~35 fs full width half maximum (FWHM) pulse width was operated at 10 Hz for generating filaments. An anti-reflection coated plano-convex lens with f=1 m was used to generate filaments in air. The spectrograph was coupled to an intensified charged coupled device (ICCD) camera (PIMAX4, 1024 × 1024 pixels) for recording time-resolved 2D spectral images.
4：Experimental Procedures and Operational Workflow:
The vacuum chamber was equipped with optical windows for laser ablation and light collection. Fast-gated imaging was performed to evaluate plume expansion dynamics, and 2D spectral imaging was used to study the spatially and temporally resolved emission dynamics of U atoms and U oxide molecules.
5：Data Analysis Methods:
The spatio-temporal evolution of U I, UO, and broadband emission intensities was analyzed to understand the role of plume chemistry on emission dynamics.
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