Next-generation material testing capabilities on the DIII-D tokamak

Upgrades to integrated material evaluation on the DIII-D tokamak are being evaluated to support increased demand and investment from private industry and the larger fusion community. Most plasma-facing material (PFM) qualification at DIII-D is currently performed using the Divertor Materials Evaluation System (DiMES), which is a removable sample exposure station in the lower divertor. Increasing sample throughput and diagnostic access requires upgrading DiMES and/or building a second station at a different location. An in vacuo rotary or linear sample exchange tray that holds several sets of samples would reduce time spent changing samples and increase sample throughput/plasma fluence. Additionally, a second exposure station could double the number of exposed samples in a discharge. Utilizing coupon-scale samples (1-5 cm) ensures that eroded material from one station is unlikely to deposit on another station. A new system opens the door to new diagnostics that do not fit in the existing DiMES location. Assuming toroidal symmetry means that existing diagnostics can be leveraged to characterize plasma conditions at both stations. Designs for a second-generation DiMES system will be presented, which will enable more rapid and insightful qualification of promising PFMs, supporting the industrial development of reactor-scale devices.