b'UnderstandingInnovative experimental method quantifies material damage during irradiation.Non-equilibrium, NanoscaleR adiation effects in materials are a concern for any structure exposed to Defects in Bulk Metals ionizing radiation. Nuclear power applications, accelerators, space nuclear applications, and isotope production facilities all share a common concern of materials property changes during exposure to radiation. Neutron, ion, and electron radiation can transfer energy to atoms in a crystal lattice. If the transferred energy exceeds the displacement energy of the atom, an atomic displacement is produced, which leads to vacancies and interstitials. The quantity of vacancies and interstitials depends on the type of radiation, incoming energy, and the host PROJECT NUMBER:material. Following the initial displacement, only a fraction of the generated 21P1064-008 vacancies and interstitials remain and build to a non-equilibrium steady-state TOTAL APPROVED AMOUNT:concentration of point defects. After the irradiation, when defect generation ceases, $88,500 over 1 year the vacancy and interstitial content reduces toward thermodynamic equilibrium. However, it is this initial non-equilibrium defect concentration that is responsible PRINCIPAL INVESTIGATOR:for the formation of larger defects, such as voids or dislocation loops, which can Cody Dennett significantly alter material properties. Therefore, understanding and quantifying the non-equilibrium defects in a material is key to predicting long-term property changes. Quantifying non-equilibrium vacancies during irradiation using methods such as in situ positron annihilation spectroscopy can provide partial validation of rate theory models. However, full validation for both vacancies and interstitials must rely on different methods due to the nature of positron-electron recombination. Researchers used pulsed ion beam irradiation to generate transient elevated populations of nanoscale defects in pure single crystal nickel while in situ laser metrology continuously captured the resulting change in elastic moduli, which are sensitive to both vacancies and interstitials. An initial demonstration of this measurement was completed, but a detailed exploration of defect generation, temperature, ion beam energy, and host material is required. Such data can be used to validate this methodology as a companion for positron annihilation measurements of vacancy concentration and as a benchmark for defect accumulation and evolution codes such as cluster dynamics. These experiments offer a singular lens into the type of transient defect generation and evolution that plays a deterministic role in nuclear system performance.48'