Recoil energy dependence of primary radiation damage in tungsten from cascade overlap with voids

Models of radiation damage accumulation often assume a constant rate of additional primary damage formation during prolonged irradiation. However, molecular dynamics simulations have shown that the presence of pre-existing radiation-induced defects modifies the numbers of additional defects formed from individual cascades. In this work, we study the formation of defects in tungsten for a range of primary recoil energies, for cascades that fully overlap with pre-existing voids of different sizes. We extend a recent model describing defect production in the presence of pre-existing damage to also account for the recoil energy dependence, and parametrize the extension based on our simulation data. We also analyze the morphology of the primary damage from cascades overlapping with voids, and show that the in-cascade formation of 〈100〉 dislocation loops in such events is more dependent on the size of the pre-existing void, than on the energy of the primary recoil.