Numerical modelling of low-temperature laser-produced magnesium plasma

The two-dimensional laser-plasma-interaction hydrodynamic code POLLUX has been used to simulate the ablation of a magnesium target by a 30-ns, 248-nm KrF excimer laser at low laser fluences of less than or equal to 10 J cm(2). This code, originally written for much higher laser intensities, has been recently extended to include a detailed description of the equation of state in order to treat changes of phase within the target material, and also includes a Thomas Fermi description of the electrons. The simulated temporal and spatial evolution of the plasma plume in the early phase of the expansion (less than or equal to 100 ns) is compared with experimental interferometric measurements of electron density. The expansion dynamics are in good agreement, although the simulated electron number density is about 2.5 times higher than the experimental values.