July 25, 2023
IGNIS, a facility for in-situ measurement of plasma-material interactions at the University of Illinois at Urbana-Champaign (UIUC), will be used to measure the interaction of hydrogen plasmas with titanium samples. TAE’s C2-W uses titanium gettering to reduce impurities and control hydrogen recycling from vessel walls and plasma facing components such as limiters and divertor plates.. Titanium offers a safe and effective wall conditioning for TAE’s Advanced FRCs, but titanium as a plasma-facing material has been understudied since the widespread adoption of high-Z materials such as tungsten and low-Z coatings such as boron or lithium in the fusion community. TAE’s next-step machine, Copernicus, will use similar wall conditioning to C2-W, but in plasma conditions beyond those observed in C2-W. TAE has developed a numerical model of hydrogen-titanium interactions that includes implantation, reflection, and sputtering simulated using a free and open-source Binary Collision Approximation code, RustBCA, coupled to an in-house model of hydrogen diffusion and outgassing that is being used to understand the physics of the plasma-material interface in C2-W and make predictions of plasma-material interactions (PMI) for the conditions expected in Copernicus. However, validation of the model using C2-W results is challenging, due to the inability to separate the plasma-material interface from the larger plasma physics of the machine; there is a crucial need to validate the model decoupled from the plasma physics to increase confidence in integrated models including PMI and predictions for Copernicus, and for application to other materials. The IGNIS facility at UIUC was purpose-built for experiments complementary to fusion PMI and offers a suite of sources and diagnostics appropriate for model validation. In this partnership, scientific contributions from the University of Illinois will both advance confidence in a free and open-source code that is of wide interest to the fusion community and improve TAE’s modeling of the specific plasma-material interface in our devices, advancing our ability to understand and predict PMI in future fusion machines. Additionally, this type of model, consisting of a BCA coupled to a diffusion model, may be broadly useful in the modeling of other fusion-relevant materials, such as boron.