2, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States
At ion energies typically used to emulate fast neutron damage, fission damage or alpha-decay damage in nuclear ceramics, the electronic and nuclear energy losses are often comparable, and local ionization along the ion path can affect damage production and evolution. Experimental and computational approaches are used to investigate the separate and combined effects of nuclear and electronic energy loss on radiation damage in ceramics relevant to nuclear applications. Defect production and damage accumulation have been investigated as functions of electronic energy loss, Se, nuclear energy loss, Sn, the ratio of electronic-to-nuclear energy loss, Se/Sn, and the damage energy, ED. Experimentally, ion mass and energy are controlled to vary electronic and nuclear energy loss, and large-scale atomistic simulations that combine ionization-induced thermal spike and atomic collision processes are used to model these effects. The results demonstrate that electronic energy loss, typical of MeV ions, can lead to competitive damage recovery processes or additive damage production effects in many nuclear-relevant ceramics. An important factor in the effectiveness of the damage recovery or production processes for a single ion event is the spatial coupling of electronic energy dissipation (via electron phonon coupling) and damage energy dissipation (via elastic scattering events) along the ion trajectory. As the radiation damage evolves, electronic energy deposition density can increase, and the dissipation of electronic energy to the lattice can further anneal existing defects along the ion trajectory or interact synergistically with the defects to enhance damage production. These results have significant implications for interpreting and modeling the radiation response of nuclear ceramics in accelerated testing using MeV ion irradiation.
This work was supported by the U.S. DOE, BES, MSED.