A Unified Model for Ion Deposition and Theromomechanical Response in Dry Wall Laser IFE Chambers

Abstract

Dry wall laser IFE chambers will experience large, transient heat and particle fluxes as the target yield products reach the wall. These threats, consisting of x-rays, ions, and neutrons, can lead to wall failure caused by transient stresses or as a result of deposited ions in the near-surface layer. We have developed a unified model for the calculation of temperatures, stresses, strains, and fracture behavior in a solid IFE chamber wall. The model is also coupled with ion transport sub-models that assess the effects of ions on the morphology of the wall materials. This paper describes the models incorporated into the new unified simulation and, in particular, presents new fracture models that permit fracture calculations without the need for an advanced finite element calculation. This fracture model assumes that an array of surface cracks is present in the wall surface and uses superposition to calculate the stress intensity factor via a numerical integration of the stress profile computed for an un-cracked geometry. We also describe approaches for computing the stresses due to inertial effects resulting from the rapid heating associated with the IFE threats. In some cases, these inertial effects lead to stress waves that can lead to premature wall damage and must be accounted for in the analysis. This model is based on semi-analytical solutions for stress waves due to shallow heating in a relatively thick solid. The combined thermomechanical model gives us detailed understanding of the fundamental mechanics of rapidly heated surfaces.