SPIE
SPIE
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国际光学工程学会
DOI：
10.1117/12.2186053
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发表时间：
2015
期刊：
影响因子：
--
通讯作者：
M. Yamagiwa
中科院分区：
文献类型：
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作者：
M. Ishino;N. Hasegawa;M.Nishikino;T.Pikuz;I. Skobelev;A. Faenov;N. Inogamov;T. Kawachi;M. Yamagiwa
为了研究软X射线激光脉冲烧蚀材料的过程，研究了烧蚀材料的电子温度。具有13.9 nm的波长和持续时间为7 ps的聚焦软X射线激光脉冲照射到LiF，Al和Cu表面上，并且我们通过使用光学相机观察到从表面的光发射。在样品表面上，我们可以确认损伤结构，但在烧蚀过程中没有观察到可见光谱范围内的发射信号。在此基础上，我们估算了烧蚀物质中的电子温度。为了考虑来自加热层的辐射，我们假设黑体辐射体是一个物体。计算结果是电子温度估计为低于1 eV和工艺持续时间短于1000 ps。理论模型计算表明，软X射线激光与材料相互作用的烧蚀机理为层裂烧蚀。飞溅的驱动力是加热层中出现的压力增加，表面的变化被认为是由于熔融层的飞溅。模型计算预测，软X射线激光与周围的能量密度烧蚀阈值可以创建一个电子温度约1 eV的材料。实验结果与理论预测吻合较好。我们的研究表明，层裂烧蚀发生在热致密物质非平衡态的低电子温度区。
To study the ablation process induced by the soft x-ray laser pulse, we investigated the electron temperature of the ablating material. Focused soft x-ray laser pulses having a wavelength of 13.9 nm and duration of 7 ps were irradiated onto the LiF, Al, and Cu surfaces, and we observed the optical emission from the surfaces by use of an optical camera. On sample surfaces, we could confirm damage structures, but no emission signal in the visible spectral range during ablation could be observed. Then, we estimated the electron temperature in the ablating matter. To consider the radiation from a heated layer, we supposed a black-body radiator as an object. The calculation result was that the electron temperature was estimated to be lower than 1 eV and the process duration was shorter than 1000 ps. The theoretical model calculation suggests the spallative ablation for the interaction between the soft x-ray laser and materials. The driving force for the spallation is an increasing pressure appearing in the heated layer, and the change of the surface is considered to be due to a splash of a molten layer. The model calculation predicts that the soft x-ray laser with the fluence around the ablation threshold can create an electron temperature around 1 eV in a material. The experimental result is in good accordance with the theoretical prediction. Our investigation implies that the spallative ablation occurs in the low electron temperature region of a non-equilibrium state of warm dense matter.