Refractive index changes and nuclear activation upon irradiation of lithium niobate crystals with different low-mass, high-energy ions

Refractive index changes $$\Delta n$$ in lithium niobate crystals upon irradiation with high-energy protons, deuterons, $$^3$$ He, and $$^4\alpha $$ particles (up to 14 MeV/nucleon) are created, and the accompanying, unwanted nuclear activation is investigated. The measurements give answers to the question which ion is the best choice depending on the requirements: largest values of $$\Delta n$$ are achieved with $$^4\alpha $$ particles, low nuclear activation with deuterons, or the best tradeoff between $$\Delta n$$ and activation with $$^3$$ He, respectively.