Modeling Gaseous Optics for Inertial Fusion Energy Applications

The survivability of final optics is a critical challenge for future inertial fusion energy systems. Gaseous optics are created by interfering ultraviolet laser beams that induce density modulations in an ozone–oxygen mixture and act as transient volume diffraction gratings. These optics provide a promising alternative to solid optics because of their high damage threshold, transient nature, and resistance to debris. We perform two-dimensional hydrodynamic simulations using PIAFS, a conservative finite-difference solver for the compressible Navier–Stokes equations with a heat source term, to model gas lens formation. Writing beam interference patterns are obtained from experimental data and used as initial condition in PIAFS. The simulations yield the resulting density modulation, which is then used to model the propagation of laser beams through the gas lens with a three-dimensional paraxial propagation code. Comparisons with preliminary experiments show good agreement, and these simulations will help design experiments targeting kilojoule-class laser systems to ensure they are optimized for future high-energy laser applications.