Experimental Characterization of a GRCop42-W Multi-Materials Junction, Produced by PBF-LB, for Particle Accelerator Target Assembly

Powder Bed Fusion–Laser-Based (PBF-LB) technology is widely employed in many fields, but specific highly demanding applications, such as multi-materials (MM), are still not fully investigated. In basic-physics research, experiments operate under extreme conditions to reduce external influences on detectors and to achieve high interaction energies between particles. The opportunity to combine different materials could allow the development of new highly customized components, where the physical properties gradually change along the three directions (x, y, z). Among components that can benefit from this last MM production, there are target holders, beam stops, and target backings. These components must withstand high temperatures and strong thermal gradients without being damaged. All of them must be as transparent as possible to the radiation emitted in the nuclear reactions of interest on its way to the detectors, but beam stops and backings must also be able to stop the beam. High-density or refractory materials, such as tungsten (W) and tantalum, can be used to stop the beam or as target backings. The aim of the paper is experimental characterization of a MM junction between Glenn Research Center Copper (GRCop42) alloy and pure W, produced by PBF-LB technology, for the design of a particle accelerator target assembly. In particular, the 12C+12C fusion reaction measurement case study of the Laboratory for Underground Nuclear Astrophysics has been considered. The MM junction has been characterized by metallographic analyses and three point bending tests, from room temperature to +300°C. GRCop42 alloy has been selected for its excellent thermal properties, great creep resistance, and strength at high temperatures, while pure W has been selected for its high atomic number, which prevents parasitic reactions on the beam stop. The results show that although W is difficult to process with an ordinary PBF-LB machine because of the high presence of porosity and internal defects, the presence of a thin layer of W on a GRCop42 substrate changes the strain behavior compared to GRCop42 alone. For instance, deformation is less influenced by high temperatures. Furthermore, while the GRCop42-W junction is less continuous than in other MM examples, it still allows sufficient W deposition to completely stop the ion beam.