Investigation of dynamics of laser-produced carbon plasma during the laser irradiation using collective Thomson scattering
Investigation of dynamics of laser-produced carbon plasma during the laser irradiation using collective Thomson scattering
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DOI：
10.1088/1361-6463/aca6f5
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发表时间：
2023-01-12
影响因子：
3.4
通讯作者：
Nishihara, Katsunobu
中科院分区：
文献类型：
--
作者：
Pan, Yiming;Tomita, Kentaro;Nishihara, Katsunobu
等离子体温度、密度和流速是激光产生等离子体（LPP）的关键物理性质，它们揭示了烧蚀动力学、能量传输和流体动力学演化。在激光照射期间以及照射刚结束后的时间窗口内，实验数据非常稀缺，以至于许多理论模型尚未得到验证。在此，我们报告了在激光峰值之后0 - 14纳秒内以及非常靠近靶材（0.13 - 0.6毫米）的区域内LPP膨胀动力学的清晰演化历史。使用一台台式Nd:YAG激光器（强度为6×10⁹瓦/平方厘米，脉冲持续时间为7纳秒）从一个平面石墨靶材产生LPP，该靶材的宽度被设置为小于激光光斑直径，以便在靶材附近产生一维平面膨胀等离子体。利用集体汤姆逊散射的离子特性测量了LPP中的电子密度（\(n_e\)）、温度（\(T_e\)）和漂移速度（\(V_d\)），提供了LPP的空间和时间分辨的二维轮廓。实验观测使得能够将膨胀动力学直接与LPP膨胀模型进行比较。结果表明，在激光脉冲期间，LPP近似等温，并主要在靶材法线方向一维膨胀，其中发现LPP漂移速度随距离线性增加。速度的线性外推表明LPP在初始靶材表面具有相当大的速度；该速度大约是由观测到的\(T_e\)导出的声速。发现实验结果与一维自相似等温膨胀模型适度吻合。观测区域内的内能与动能之比约为0.6，这与等温膨胀模型的预测一致。将实验结果与二维混合代码STAR的结果进行了比较，并取得了良好的一致性。
Plasma temperature, density, and flow velocity are the critical physical properties of laser produced plasma (LPP) to reveal the ablation dynamics, energy transport, and hydrodynamic evolution. In the time window during and just after laser irradiation, experimental data are very scarce so that many theoretical models remain untested. Here we report a clear evolution history of LPP expansion dynamics within 0-14 ns after the laser peak and in a region very close to the target (0.13-0.6 mm). A table-top Nd:YAG laser (intensity 6 x 10(9) W cm(-2), pulse 7 ns) was used to generate the LPP from a planar graphite target, whose width was arranged to be smaller than the laser spot diameter to produce a one-dimensional planar expansion plasma near the target. The electron density (n(e)), temperature (T-e), and drift velocity (V-d) in the LPPs were measured using the ion feature of collective Thomson scattering, providing a space-and time-resolved 2D profile of the LPP. The experimental observations made it possible for the expansion dynamics to be compared directly with the LPP expansion models. The results suggest that during the laser pulse, the LPP is approximately isothermal and expands predominantly one-dimensionally in the target normal direction, in which the LPP drift velocity is found to increase linearly with distance. The linear extrapolation of the velocity indicates that the LPP has a considerable velocity at the initial target surface; this velocity is approximately the speed of sound derived from the observed T-e. The experimental results were found to be in moderate agreement with the 1D self-similar isothermal expansion model. The ratio of the internal to kinetic energy in the observed area was similar to 0.6, as predicted by the isothermal expansion model. The experimental findings were compared with the results of the 2D hybrid code STAR, and good agreement was obtained.