Paper
22 September 2015 Low electron temperature in ablating materials formed by picosecond soft x-ray laser pulses
Masahiko Ishino, Noboru Hasegawa, Masaharu Nishikino, Tatiana Pikuz, Igor Skobelev, Anatoly Faenov, Nail Inogamov, Tetsuya Kawachi, Mitsuru Yamagiwa
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Abstract
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.
© (2015) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Masahiko Ishino, Noboru Hasegawa, Masaharu Nishikino, Tatiana Pikuz, Igor Skobelev, Anatoly Faenov, Nail Inogamov, Tetsuya Kawachi, and Mitsuru Yamagiwa "Low electron temperature in ablating materials formed by picosecond soft x-ray laser pulses", Proc. SPIE 9589, X-Ray Lasers and Coherent X-Ray Sources: Development and Applications XI, 958904 (22 September 2015); https://doi.org/10.1117/12.2186053
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KEYWORDS
Picosecond phenomena

X-ray lasers

Laser ablation

Laser induced fluorescence

CMOS sensors

Cameras

Aluminum

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