The implementation of the metal additive manufacturing for the DTT experiment: NBI, and ECRH components

Nuclear fusion faces many challenges, one of which is the production of reactor components. Due to the extreme operating conditions, the geometrical aspect is of great importance. Some important components are, for example, the accelerating grids of the Negative Ions Neutral Beam (NBI) Injection system. To guarantee the most appropriate beam optics and optimized cooling, the grids must be built with a shape that would be impossible to obtain with traditional manufacturing approaches. Additive manufacturing technologies allow producing very geometrically complex components, with high dimensional accuracy and an optimized shape considering also the design-for-assembly point of view. However, these innovative technologies are not free from challenges. A key point is the optimization of the process parameters, which are specific for each material and powder; this preliminary research is fundamental to obtain the best quality and performance from a material. Additive manufacturing represents a highly promising production method also for the fabrication of components made of refractory metals. Indeed, this special class of materials is extremely difficult to form due to their unique characteristics; moreover, they are usually very expensive, so waste should be reduced as much as possible. In nuclear fusion, refractory metals are good candidates for plasma-facing and divertor applications, for example, where the operative conditions are prohibitive. In this work, the studies related to the characterization of materials processed with Laser Powder Bed Fusion (LPBF) technique are presented, for what concerns copper alloys and refractory metals. The latest updates on the innovative design specially developed for additive manufacturing of the accelerating grids for the NBI system of DTT are also described.