Spectroscopic study of laser-induced Al plasmas with cylindrical confinement

The cylindrical confinement of laser-induced plasmas in round pipes has been investigated by optical emission spectra and fast imaging. An obvious enhancement in the emission intensity of Al atomic lines was observed when a round pipe was placed to confine the laser-induced Al plasmas. The enhancement factor for the emission intensities of the Al atomic lines was measured to be around 9 at a time delay of 12 μs when the pipe diameter is 10.8 mm. Assuming local thermodynamic equilibrium conditions, the plasma temperatures are estimated to be in the range from 4000 to 5800 K. It shows that the plasma temperature increased by around 1000 K when the cylindrical confinement was applied. Images of the laser-induced Al plasmas show that the plasmas were compressed into a smaller volume with a pipe presented. The spatial-confinement effects are attributed to the reflection and compression of the shock wave.