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Proceedings Paper

Nanospallation induced by a femtosecond laser pulse
Author(s): M. B. Agranat; S. I. Anisimov; S. I. Ashitkov; V. V. Zhakhovskii; N. A. Inogamov; K. Nishihara; Yu. V. Petrov
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Paper Abstract

In the present work phenomena are considered related to the interaction of ultra-short laser pulses, τL~0.1 ps, with metallic targets. The absorption of laser pulse results in formation of thin layer of hot electrons strongly superheated (Te>>Ti) relative to the ion temperature, Ti. Initial thickness of the layer dheat is small, dheat~δ, where δ~10 nm is the skin layer thickness. Subsequent developments include the following stages: (1) Propagation of electron thermal wave which expands the hot layer dheat; (2) Cooling of electrons due to energy transfer to cold ions; (3) Onset of hydrodynamic motion that constitutes the rarefaction wave with positive pressure; (4) Further expansion of target material leading to the appearance of negative pressure; and (5) Long separation process which begins with nucleation of voids and goes on to the total separation of spallation plate. The thickness of the plate is ~10 nm (we call it nanospallation). Theoretical model involves two-temperature hydrodynamic equations with semiempirical EOS for a metal, electron heat conduction and electron-ion energy exchange. The decay of metastable strongly stretched matter is described by molecular dynamics (MD) simulation with extremely large number of atoms. The experimental setup includes femtosecond chromium-forsterite laser operating in the pump-probe regime. The experiments are performed with gold target. Measured ablation threshold for gold is 1.35 J/cm2 of incident pump light at inclination 45°, p-polarization. Calorimeter measurements give for the absorbed fluence Fabs=0.3Finc, therefore the threshold value of Fabs is 0.4 J/cm2.

Paper Details

Date Published: 18 December 2007
PDF: 12 pages
Proc. SPIE 6720, Laser-Induced Damage in Optical Materials: 2007, 672002 (18 December 2007); doi: 10.1117/12.738550
Show Author Affiliations
M. B. Agranat, Joint Institute for High Temperatures (Russia)
S. I. Anisimov, Joint Institute for High Temperatures (Russia)
L.D. Landau Institute for Theoretical Physics (Russia)
S. I. Ashitkov, Joint Institute for High Temperatures (Russia)
V. V. Zhakhovskii, Joint Institute for High Temperatures (Russia)
Osaka Univ. (Japan)
N. A. Inogamov, L.D. Landau Institute for Theoretical Physics (Russia)
K. Nishihara, Osaka Univ. (Japan)
Yu. V. Petrov, L.D. Landau Institute for Theoretical Physics (Russia)

Published in SPIE Proceedings Vol. 6720:
Laser-Induced Damage in Optical Materials: 2007
Gregory J. Exarhos; Arthur H. Guenther; Keith L. Lewis; Detlev Ristau; M. J. Soileau; Christopher J. Stolz, Editor(s)

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