High-intensity nanosecond-pulsed laser-induced plasma in air, water, and vacuum: A comparative study of the early-stage evolution using a physics-based predictive model

A comparative study has been performed for properties (temperature, density, and electron Coulomb coupling constant) of plasma induced by high-intensity (similar to GW/cm2) nanosecond laser-metal interactions in air, water, and vacuum. The study is for early-stage (t less than or similar to 30ns) plasma evolution, where the above plasma properties are very difficult to measure experimentally and hence a comparative property study has been rarely reported in literature. In this paper a physics-based predictive model is used as the investigation tool. The model was verified based on experimental measurements for the early-stage plasma pressure and front propagation and the late-stage (t greater than or similar to 30ns) plasma temperature and electron number density, which are relatively easy to measure. Therefore, the experimentally verified model can provide reasonably accurate information on the difficult- to- measure plasma temperature and density in the early-stage at least in the semiquantitative sense, and the information will be very useful for the fundamental laser plasma study and relevant laser applications. It has been found that plasma with very different temperatures and densities can be created in different media. (c) 2008 American Institute of Physics.