The role of spatial confinement on nanosecond YAG laser-induced Cu plasma

Abstract

The role of spatial confinement in nanosecond laser-induced Cu plasma is investigated by optical emission spectroscopy, fast imaging and optical shadow imaging. Significant spectral enhancements of the atomic and ionic emissions are observed when two Al-plates are used to confine the plasma. The experimental results show that parameters such as the plasma temperature, electron density, and spectral signal-to-background ratio all increase in the presence of spatial confinement, and the distance of the two walls are critical for the spectral enhancement, the enhancement time duration, and the delay time at which the maximum spectral enhancement is observed. These effects occur later and become weaker with increasing wall distance. The fast imaging and shadowgraph results show that the shape of the plasma plume becomes narrower and longer with spatial confinement, and is also dependent on the wall distance. The spectral enhancement is attributed to the reflection of the shock wave by the wall plates, which compresses the plasma to a small local region and induces further collision excitation.