The absorption and radiation of a tungsten plasma plume during nanosecond laser ablation
- Institute of Fundamental Technological Research PAS, Pawinskiego 5B, 02-106 Warsaw (Poland)
In this paper, the effect of absorption of the laser beam and subsequent radiation on the dynamics of a tungsten plasma plume during pulsed laser ablation is analyzed. Different laser wavelengths are taken into consideration. The absorption and emission coefficients of tungsten plasma in a pressure range of 0.1–100 MPa and temperature up to 70 000 K are presented. The shielding effects due to the absorption and radiation of plasma may have an impact on the course of ablation. The numerical model that describes the tungsten target heating and the formation of the plasma and its expansion were made for 355 nm and 1064 nm wavelengths of a Nd:YAG laser. The laser beam with a Gaussian profile was focused to a spot size of 0.055 mm{sup 2} with a power density of 1 × 10{sup 9 }W/cm{sup 2} (10 ns full width half maximum pulse duration). The plasma expands into air at ambient pressure of 1 mPa. The use of the shorter wavelength causes faster heating of the target, thus the higher ablation rate. The consequences of a higher ablation rate are slower expansion and smaller dimensions of the plasma plume. The higher plasma temperature in the case of 1064 nm is due to the lower density and lower plasma radiation. In the initial phase of propagation of the plasma plume, when both the temperature and pressure are very high, the dominant radiation is emission due to photo-recombination. However, for a 1064 nm laser wavelength after 100 ns of plasma expansion, the radiation of the spectral lines is up to 46.5% of the total plasma radiation and should not be neglected.
- OSTI ID:
- 22486467
- Journal Information:
- Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 10 Vol. 22; ISSN PHPAEN; ISSN 1070-664X
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ABSORPTION
AIR
ELECTRON TEMPERATURE
EMISSION
ION TEMPERATURE
LASER TARGETS
LASER-RADIATION HEATING
NEODYMIUM LASERS
PHOTON BEAMS
PLASMA
PLASMA EXPANSION
POWER DENSITY
PRESSURE RANGE MEGA PA
RECOMBINATION
SHIELDING
TEMPERATURE RANGE OVER 4000 K
TUNGSTEN
WAVELENGTHS