Fabrication Process of Niobium-Gallium Capsule Targets for Cyclotron Production of ⁶⁸Ge

⁶⁸Ge serves as the pivotal parent nuclide for the medical positron emitter ⁶⁸Ga, rendering target design and fabrication critical for cyclotron-based production. This study systematically investigates the preparation of sealed Niobium-gallium capsule targets. Firstly, yield simulations using the FLUKA were conducted to the target design. Gradient experiments on gallium cavity depth and filling ratio were performed to determine the optimal target parameters and electron beam welding safe distance. The effect of gallium filling on welding performance was investigated through weld penetration analysis and X-ray diffraction. Subsequently, quality control was implemented through computed tomography imaging, helium mass spectrometry leak testing, and thermal shock experiments to ascertain high-temperature failure reason. Finally, hot experiments verified reliability of targets. The results indicate that excessive gallium will increase weld penetration and form the Ga₅Nb₄ compound, resulting in fracture failure of the target component. The optimal target structure is achieved at a gallium cavity depth of 1.35 mm and a filling ratio of 68%-72%. The target exhibits excellent hermeticity (leak rate <5×10⁻³ Pa·cm³/s) and thermal stability below 400 ℃. Hot experiments yielded approximately 2.7-3.9 GBq of ⁶⁸Ge with radiochemical purity higher than 99.9% and element impurities below 2 ppm. This study demonstrates superior performance of niobium-gallium capsule targets fabricated via electron beam welding, providing critical process support for the scalable and safe production of ⁶⁸Ge.