Laser ablation of Cu and plume expansion into 1 atm ambient gas
- Department of Chemistry, University of Antwerp, Universiteitsplein 1, B-2610 Wilrijk-Antwerp (Belgium)
A one-dimensional gas-dynamic model is presented for the laser ablation of Cu and the expansion of the Cu vapor in a background gas (He) at 1 atm. The ionization of Cu and He, the inverse bremsstrahlung absorption processes and photoionization process, and the back flux onto the target are considered simultaneously. The binary diffusion, the viscosity, and the thermal conduction including the electron thermal conduction are considered as well. Numerical results show that the consideration of ionization and laser absorption in the plume greatly influences the gas dynamics. The ionization of Cu enables the recondensation at the target surface to happen even during the laser pulse. The ionization degree of Cu and He may change greatly with the location in the plume. For laser irradiances ranging from 2 to 9x10{sup 12} W/m{sup 2}, the simulations show that the second-order ionization of Cu competes with the first-order ionization. In the region close to the target surface, the first-order ionization of Cu dominates. In the core of the plasma, the second-order ionization of Cu may dominate over the first-order ionization at laser irradiances higher than 7x10{sup 12} W/m{sup 2}. In the mixing layer, the first-order ionization of Cu is always more important than the second-order ionization although the latter increases monotonously with laser irradiance. The ionization of He is only important in the mixing layer. The plume expansion velocity is much larger than that without ionization and laser absorption by the plume. The relative importance of different laser absorption mechanisms may change with time. Close to the surface photoionization and electron-neutral inverse bremsstrahlung are always important. Once the ionization in the plume starts, at later time, electron-ion inverse bremsstrahlung can become more important than photoionization in the plume core until the shock wave front. Unlike in the vacuum case, electron-neutral inverse bremsstrahlung is very strong due to the relatively high number density of neutral atoms in the plume in the presence of a dense ambient gas. A similar laser irradiance threshold is found for the ablation rate and the plasma formation in the plume, which agrees well with the case of nanosecond laser ablation of metals in vacuum.
- OSTI ID:
- 20668242
- Journal Information:
- Journal of Applied Physics, Vol. 97, Issue 6; Other Information: DOI: 10.1063/1.1863419; (c) 2005 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GENERAL PHYSICS
36 MATERIALS SCIENCE
ABLATION
ABSORPTION
BREMSSTRAHLUNG
COPPER
ELECTRONS
EXPANSION
LAYERS
MIXING
ONE-DIMENSIONAL CALCULATIONS
PHOTOIONIZATION
PLASMA
PLASMA PRODUCTION
PLASMA SIMULATION
PLASMA WAVES
PLUMES
PULSES
SHOCK WAVES
THERMAL CONDUCTION
VISCOSITY
WAVE PROPAGATION