The impact of boron intermixing in PFC on atomic, structural and mechanical features

Project title: The impact of boron intermixing in PFC on atomic, structural and mechanical features: sputter yields, near-surface morphology, and fuel retention
Main applicant: Eduardo Pitthan Filho, Division of Applied Nuclear Physics
Grant Amount: 4.2 million SEK for the period 2024-2025

Nuclear fusion has the potential to become a safe and CO2-free source of energy for humanity. The plasma, in which the fusion process takes place, can reach temperatures of up to 150 million degrees Celsius making the design of a fusion reactor a technical challenge. Even though the plasma itself is confined by a magnetic field, the reactor walls, also called plasma facing components (PFC), are subject to extreme conditions that require both a careful selection of the materials that they are made of and precise knowledge of the changes that occur in the materials when it comes in contact with the plasma.

The interactions of the plasma with the PFC result in material migration processes comprising of erosion and re-deposition of wall materials accompanied by co-deposition of plasma fuel atoms (hydrogen isotopes). The resulting modifications of the PFC are an active field of experimental and theoretical research. The present project, which includes researchers from Uppsala University, Vienna University of Technology, Austria, and Aalto University, Finland, will study the morphology of the mixed layers that will accumulate on different parts of the reactor walls as a result of the mentioned re-deposition and co-deposition processes. Such layers will show different chemical composition and structure than the bulk of the reactor walls, and they can be expected to change further under exposure to the reactor environment.

Two promising candidates for the PFC material are tungsten and a special type of steel called EUROFER97. To further improve the performance of the reactor, it is possible to apply a coating containing boron to the wall material. Eduardo Pitthan Filho and his colleagues will therefore focus especially on material layers containing boron. The present project combines experiments with computational modelling. The researchers will among others use the infrastructure at the Tandem Laboratory at Uppsala University to both fabricate such samples as well as to study how they change under ion bombardment or heat. Researchers at Aalto University and Vienna University of Technology will perform complementary simulations using molecular dynamics and binary collision approximation approaches. Both the experiments and the calculations will pay special attention to the sputter yield to try to quantify the erosion of the PFC by ions contained in the plasma.