NUMERICAL THERMAL STABILITY STUDIES OF THE NATIONAL IGNITION FACILITY FINAL OPTICS ASSEMBLY

摘要

The National Ignition Facility (NIF), the world's most powerful laser system, is being built at Lawrence Livermore National Laboratory (LLNL) to study inertial fusion and high-energy-density science. This billion-dollar facility consists of 192 beams focusing 1.8 MJ on a fusion target. The Final Optics Assembly (FOA), the last mechanical apparatus before the target chamber, converts the light from an incoming frequency of 1ω to a target-ready 3ω, and focuses the laser beam. The performance of the frequency conversion crystals is very sensitive to temperature changes; crystal temperature must be maintained within a 0.1°C of a nominal temperature prior to a laser shot. To insure system availability, it is important to have an estimate of the thermal recovery time to operating temperature of the FOA after thermal disturbances caused by normal and maintenance operations. This paper presents Computational Fluids Dynamics (CFD) fluid and thermal design calculations for both normal and maintenance operations of the NIF FOA.