量研学術機関リポジトリ「QST-Repository」は、国立研究開発法人 量子科学技術研究開発機構に所属する職員等が生み出した学術成果（学会誌発表論文、学会発表、研究開発報告書、特許等）を集積しインターネット上で広く公開するサービスです。 Welcome to QST-Repository where we accumulates and discloses the academic research results(Journal Publications, Conference presentation, Research and Development Report, Patent, etc.) of the members of National Institutes for Quantum Science and Technology.
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We report the systematic experimental study of the surface modifications resulting by interactions of both femtosecond and picosecond soft x-ray laser pulses with matters. When the femtosecond free electron soft x-ray laser pulse irradiated onto the LiF crystal, the surface modification structures appeared by the fluence of around 10 mJ/cm2. This value was in good accord with the value obtained by the picosecond soft x-ray laser pulse. The ablation process occurring on LiF crystals can be explained by the spallation model. The driving force of the spallation is an increasing inertial pressure appearing inside of the irradiated heating layer. The damage structures on Al formed by the picosecond and femtosecond soft x-ray laser pulses were the almost the same, and ablation thresholds were also the same. However, these ablation threshold values were smaller than the model calculation. The threshold of Al surface, also of the Au surface, was near the melting threshold, and the modification depths agreed with melting depths. In the low fluence ablation regime, it is considered that the first change of the surface structure is the melting of the surface and is probably due to splash of the molten layer.
Short pulse soft x-ray laser ablation at low fluence region
