Modeling of Pressure Evolution during Nanosecond Laser Ablation of Metal Films

Hendijanifard, M., Willis, D.A., “Modeling of Pressure Evolution during Nanosecond Laser Ablation of Metal Films”, Proceedings of the HT2009 (Presented at Summer Heat Transfer Conference, July, 2009).

Hendijanifard HT2009 paper.pdf
#-Link-Snipped-#
ABSTRACT
Nanosecond laser ablation is studied using a theoretical
model combined with experimental data from laser ablation of
metal films. The purpose of the research is to obtain the recoil
pressure boundary condition resulting from explosive phase
change. The ablation experiments are performed using a
Nd:YAG laser of 1064 nm wavelength and 7 ns pulse width at
full width half maximum. Three samples, 200 and 1000 nm
aluminum films and 1000 nm nickel films, are used in the
experiments. The transient shock wave positions are obtained
by a time-resolved shadowgraph technique. A N2-laser pumped
dye laser with 3 ns pulse width is used as an illumination source
and is synchronized with the ablation laser to obtain the
transient shock wave position with nanosecond resolution. The
transient shock position is used in a model for finding the shock
wave speed as well as the pressure, temperature, and velocity
just behind the shock wave. A power law is used for fitting
curves on the experimentally obtained shock wave position.
Knowing the shock wave position, the normal shock equations
are used to calculate the thermo-fluid properties behind the
shock wave. The solutions are compared with the Taylor-Sedov
solution for spherical shocks and the reason for the deviation is
described. The thermo-fluid property results show similar
trends for all tested samples. The results show that the Taylor-
Sedov solution under-estimates the pressure behind the shock
wave when compared to the normal shock results.