Laser ray tracing and power deposition on an unstructured three-dimensional grid

Area of Science:

• Computational physics
• Plasma physics
• Laser-matter interactions

Background:

• Accurate simulation of laser beam propagation and energy deposition is essential for understanding laser-plasma interactions.
• Existing methods often struggle with complex, three-dimensional unstructured grids common in advanced simulations.

Purpose of the Study:

• To develop and present a novel computational scheme for laser beam evolution and power deposition.
• To handle diverse grid types (hexahedra, prisms, pyramids, tetrahedra) in three-dimensional simulations.
• To accurately model inverse-bremsstrahlung power deposition in non-uniform plasma densities.

Main Methods:

• Utilizes the geometrical-optics approximation to the electromagnetic wave equation for ray propagation.
• Employs a second-order accurate time integration method for ray trajectories, handling density gradients and discontinuities.
• Models inverse-bremsstrahlung with Gaussian quadrature for highly non-uniform deposition rates.

Main Results:

• The scheme successfully simulates laser beam propagation and power deposition on unstructured grids.
• Comparisons with analytic results demonstrate accuracy for density ramps and quadratic-well density troughs.
• The method is capable of handling complex plasma density variations.

Conclusions:

• The presented scheme provides an accurate and flexible tool for simulating laser-plasma interactions in complex geometries.
• This work advances computational capabilities for inertial confinement fusion and other laser-driven plasma applications.
• The method's ability to handle unstructured grids and non-uniform densities is a significant improvement.