Fusion Science and Technology / Volume 52 / Number 3 / October 2007 / Pages 579-583
Technical Paper / The Technology of Fusion Energy - High Heat Flux Components
Tungsten is a candidate material for a variety of applications in Magnetic and Inertial Fusion Energy systems. Experimental data show that the surface of tungsten exposed to laser, ion, and X-ray irradiation undergoes substantial roughening. Control of surface conditions is essential to the design of these systems, since it can lead to crack formation, adverse effects on heat absorption because of emissivity changes, and eventual failure.
We first review recent experimental data on the effects of laser, ion and X-ray energetic pulses on the evolution of a surface to identify the variety of patterns and length scales and their dependence on the type and magnitude of irradiation pulses. Then we present a model for the evolution of surface roughness as a result of the balance between destabilizing elastic strain energy caused by thermomechanical strains and near surface accumulation of defects on the one hand, and stabilizing surface and near surface atomic diffusion on the other. Results of the model determine the conditions for surface roughness evolution and the effects of radiation fluence and pulse intensity on surface morphology.