论文标题

激光产生的等离子体中发射和吸收特征的时空演化

Spatiotemporal evolution of emission and absorption signatures in a laser-produced plasma

论文作者

Harilal, Sivanandan S., Kautz, Elizabeth J., Phillips, Mark C.

论文摘要

我们报告了纳秒(NS)激光生产的血浆(LPP)中Al物种的发射和吸收特征的时空演化。等离子体是从Inconel目标产生的,该目标包含$ \ sim $ 0.4 wt。%al,使用1064 nm,〜6 ns的全宽度最大脉冲,从ND:YAG激光器的AR覆盖气体压力约为34 TORR。 Al I(394.4 nm)的时间分布是从血浆中的各个空间点收集的,采用飞行时间(TOF)发射和激光吸收光谱,它们提供了所选过渡的激发状态和基态种群的动力学。尽管它们出现在等离子体发作后的不同空间位置和时间上,但发射和吸收特征在其时间曲线中显示出多个峰。吸收时间曲线显示出早期特征,代表冲击波传播到环境气体中。我们还使用发射和吸收光谱特征来测量血浆的各种物理特性。吸收光谱轮廓用于测量线宽,柱密度和动力学温度,而发射光谱则用于测量激发温度。激发与动力学温度之间的比较是在血浆中的各个空间点进行的。我们的结果强调,TOF测量值提供了一种足智多谋的工具,可以显示出具有更高空间和时间分辨率的时空LPP动力学,而不是光谱测量值,但是如果没有有关激发温度和线宽的其他信息,则难以解释。因此,吸收和发射TOF和光谱测量值的组合提供了LPP时空动力学的更完整的图像,而不是仅使用任何一种技术。

We report spatiotemporal evolution of emission and absorption signatures of Al species in a nanosecond (ns) laser-produced plasma (LPP). The plasmas were generated from an Inconel target, which contained $\sim $ 0.4 wt.% Al, using 1064 nm, ~ 6 ns full width half maximum pulses from an Nd:YAG laser at an Ar cover gas pressure of ~ 34 Torr. The temporal distributions of the Al I (394.4 nm) transition were collected from various spatial points within the plasma employing time-of-flight (TOF) emission and laser absorption spectroscopy and they provide kinetics of the excited state and ground state population of the selected transition. The emission and absorption signatures showed multiple peaks in their temporal profiles, although they appeared at different spatial locations and times after the plasma onset. The absorption temporal profiles showed an early time signature representing shock wave propagation into the ambient gas. We also used emission and absorption spectral features for measuring various physical properties of the plasma. The absorption spectral profiles are utilized for measuring linewidths, column density, and kinetic temperature while emission spectra were used to measure excitation temperature. A comparison between excitation and the kinetic temperature was made at various spatial points in the plasma. Our results highlight that the TOF measurements provide a resourceful tool for showing the spatiotemporal LPP dynamics with higher spatial and temporal resolution than is possible with spectral measurements but are difficult to interpret without additional information on excitation temperatures and linewidths. The combination of absorption and emission TOF and spectral measurements thus provides a more complete picture of LPP spatiotemporal dynamics than is possible using any one technique alone.

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