Mechanisms of phase change during excimer laser ablation
This work examines two phase change mechanisms, surface evaporation and phase explosion, occurring during ablation of nickel by a KrF excimer laser ({lambda} = 248 nm). The velocity of the laser-ablated vapor plume is measured in the laser fluence range between 2 and 10 J/cm{sup 2}. Surface evaporation results in the successive formation of the Knudsen layer, adiabatic expansion of the plume, compression of air, and a shock wave. While during phase explosion, the structure of the laser ablated plume near the target surface is more complicated. Applying gas dynamics analyses to the propagation of laser-ablated vapor and the air flow driven by the vapor, the normal vaporization temperature at the target surface is calculated when the laser fluence is less than the threshold value of phase explosion. The pressure exerted on the target surface is also estimated from the gas dynamics analyses. The calculated pressure is compared to the measured pressure of the compression wave propagating in the target medium. It is concluded that a transition of the dominating ablation mechanism from surface evaporation to phase explosion occurs within the laser energy fluence range used in this work.
- Research Organization:
- Purdue Univ., West Lafayette, IN (US)
- OSTI ID:
- 20002426
- Report Number(s):
- CONF-990805--
- Country of Publication:
- United States
- Language:
- English
Similar Records
Modeling of nanosecond laser ablation with vapor plasma formation
Expansion of the laser ablation vapor plume into a background gas. I. Analysis