Product Code: ICAL07_M1003
Spatial-confinement Effects in Laser-induced Breakdown Spectroscopy
X.K. Shen, University of Nebraska - Lincoln; Lincoln NE USA
J. Sun, University of Nebraska - Lincoln; Lincoln NE USA
Yongfeng Lu, University of Nebraska - Lincoln; Lincoln NE USA
Presented at ICALEO 2007
The spatial confinement effects in laser-induced breakdown of aluminum (Al) targets in air have been investigated both by optical emission spectroscopy and fast photography. KrF excimer laser pulses with a pulse duration of 23 ns and a wavelength of 248 nm were used to produce plasmas from Al targets. Al atomic emission lines show an obvious enhancement in the intensity of optical emission when a round pipe of 9.2 mm diameter is placed to spatially confine the plasma plumes. Temporal evolution of the optical emission lines shows a continuous enhancement in emission intensity at time delays of 5-16 μs after the incident laser pulse when the pipe presents. The maximum enhance factor in emission intensity of Al atomic line (Al I, 394.4 nm) is around 4. Fast photography of the laser-induced Al plasmas shows that the plasma evolves into a torus shape without a round pipe. While with the presence of a round pipe, the plasma plumes are compressed at the center. The confinement effects are also dependent on the pipe diameter. As the pipe diameter decreases, the confinement effects occur at earlier time delay and the enhancement effects are stronger. The mechanism for the confinement effects was discussed using the shock wave theory.
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