Molecular dynamics study of structure transformation and H effects in irradiated silica

Fused silica is a key component in a number of diagnostics for the Safety and Control Systems of the ITER machine as well as in the final focusing optics of lasers for inertial fusion and it will be exposed to high radiation fields (neutron and gamma) in both environments. Silica properties of interest are closely related to the presence of defects and its changing structure. On the other hand, some experimental results show that radiation damage depends on its hydrogen content. In this work we present molecular dynamics (MD) simulations to study the effects of displacement cascades on the ring size distribution and on the presence of the hydrogen atoms. Changes in the ring size distribution and variation of the local relative densities have been observed to be a function of the primary knock-on atom energy. And on the other hand, the effects of the hydrogen atoms in the evolution of numbers of defects have been determined.