ALE Simulations of Laser Driven Target Acceleration in Channel

The Arbitrary Lagrangian-Eulerian (ALE) methods are becoming very popular for simulations of laser-plasma simulations. A typical ALE method consists of three steps: a Lagrangian solver, advancing the solution to the next time step; a rezoner, improving geometrical quality of the computational mesh; and a remapper, interpolating conservatively all fluid quantities from the Lagrangian to the rezoned mesh. Due to the Lagrangian solver, the computational mesh naturally follows motion of the fluid, so it is very suitable in case of severe compressions or expansions of the material, often present in the laser-plasma simulations. On the other hand, the Eulerian part of the method (consisting of mesh rezoning and quantity remapping) keeps the mesh smooth and prevents the simulation from failure due to the mesh degeneracy. In our 2D ALE code PALE [1], [2], we are able to perform simulations of high-velocity plasma flows generated by an intense laser beam. This code incorporates a staggered Lagrangian solver [3], treating all thermodynamic quantities in the mesh cell centers, and all kinematic quantities on the mesh nodes. As a mesh rezoner, we use the classical Winslow smoothing employed in warm regions only. For remapping, the swept-region based approach followed by a repair stage enforcing the local-bound preservation requirement [4] is used. The code incorporates the QEOS equation of state, the Spitzer-Harm heat conductivity model with flux limiter, and a laser absorption model on the critical density, in both the Cartesian and cylindrical geometries. We demonstrate the application of the cylindrical PALE code on a series of selected problems, motivated by the experiments performed on the PALS laser facility [5]. Three experimental setups shown in Figure 1 are studied numerically. The first scheme (L-T) represents a direct irradiation of a solid Aluminum target by an intense laser beam. The ablative acceleration