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A computational model for nanosecond pulse laser-plasma interactions. (English) Zbl 1453.76103
Summary: A multi-physics numerical model for laser-induced optical breakdown and laser-plasma interaction in a non-equilibrium gas is presented, accounting for: production of priming electrons via multi-photon ionization, energy absorption, cascade ionization, induced hydrodynamic response, and shock formation and propagation. The gas is governed by the Navier-Stokes equations, with non-equilibrium effects taken into account by means of a two-temperature model. The space-time dependence of the laser beam is modeled with a flux-tube formulation for the Radiative Transfer Equation. The flow governing equations are discretized in space using a second-order finite volume method. The semi-discrete equations are marched in time using an implicit-explicit (IMEX) dual time-stepping strategy, where diffusion and chemistry are solved implicitly, whereas convection is explicit. Application to a 20 ns long 50 mJ pulse laser-induced breakdown in quiescent $$O_2$$ shows the advantages of this temporal discretization during and just after the laser pulse, while a less-expensive symmetric Strang splitting (with implicit chemistry) is sufficient for the post-breakdown gas dynamics after $$\simeq 0.1 \mu$$ s. The integrated model is shown to reproduce key features of corresponding experiments.
##### MSC:
 76M12 Finite volume methods applied to problems in fluid mechanics 76X05 Ionized gas flow in electromagnetic fields; plasmic flow 76N06 Compressible Navier-Stokes equations 82C40 Kinetic theory of gases in time-dependent statistical mechanics
##### Software:
AUSM; LOGOS; LSODE; PETSc; RKC; SUNDIALS
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