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Detecting of melting by changes of rear surface reflectivity in shocked compressed metals using an interferometric diagnostic method

Published online by Cambridge University Press:  01 July 1999

M. WERDIGER ,
S. ELIEZER ,
S. MAMAN ,
Y. HOROVITZ ,
E. MOSHE ,
A. LUDMIRSKY ,
B. ARAD ,
Z. HENIS  and
I.B. GOLDBERG
M. WERDIGER
Affiliation:
Plasma Physics Department, Soreq NRC, Yavne, 81800, Israel
S. ELIEZER
Affiliation:
Plasma Physics Department, Soreq NRC, Yavne, 81800, Israel
S. MAMAN
Affiliation:
Plasma Physics Department, Soreq NRC, Yavne, 81800, Israel
Y. HOROVITZ
Affiliation:
Plasma Physics Department, Soreq NRC, Yavne, 81800, Israel
E. MOSHE
Affiliation:
Plasma Physics Department, Soreq NRC, Yavne, 81800, Israel
A. LUDMIRSKY
Affiliation:
Plasma Physics Department, Soreq NRC, Yavne, 81800, Israel
B. ARAD
Affiliation:
Plasma Physics Department, Soreq NRC, Yavne, 81800, Israel
Z. HENIS
Affiliation:
Plasma Physics Department, Soreq NRC, Yavne, 81800, Israel
I.B. GOLDBERG
Affiliation:
Racah Institute of Physics, Hebrew University, Jerusalem 91904, Israel
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Abstract

When a high power laser (1012 W/cm2) irradiates a target, it induces a shock wave, which reaches the (free) rear surface. The free surface is accelerated and the shock wave is back-reflected as a rarefaction wave. In the shock wave pressure regime involved here, melting of the target during the shock or during the rarefaction may occur. An optically recording velocity interferometric system (ORVIS) has been developed to measure the time evolution of the change in the reflectivity of the free surface. Shock waves of the order of hundreds of kilobars are produced in 50–125 μm thick Sn and Al foils, by a Nd:YAG laser system with a wavelength of 1.06 μm, pulse width of 7 ns (FWHM), and irradiance in the range (1.4–2.4)·1013 W/cm2. The changes in the reflectivity occur along two time scales: a slow one, more than 17 ns in Al and more than 30 ns in Sn, and a rapid one, less than 2.5 ns, in both materials. A possible explanation for the sharp decreases in the time scale is that melting occurs during the release of the free surface.

Type
Research Article
Information
Laser and Particle Beams , Volume 17 , Issue 3 , July 1999 , pp. 547 - 556
Copyright
1999 Cambridge University Press

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