A major challenge facing the design and operation of next-step high-power steady-state fusion devices is to develop a viable divertor solution with order-of-magnitude increases in power handling capability relative to present experience, while having acceptable divertor target plate erosion and being compatible with maintaining good core plasma confinement. A new initiative has been launched on DIII-D to develop the scientific basis for design, installation, and operation of an advanced divertor to evaluate boundary plasma solutions applicable to next step fusion experiments beyond ITER. Developing the scientific basis for fusion reactor divertor solutions must necessarily follow three lines of research, which we plan to pursue in DIII-D: (1) Advance scientific understanding and predictive capability through development and comparison between state-of-the art computational models and enhanced measurements using targeted parametric scans; (2) Develop and validate key divertor design concepts and codes through innovative variations in physical structure and magnetic geometry; (3) Assess candidate materials, determining the implications for core plasma operation and control, and develop mitigation techniques for any deleterious effects, incorporating development of plasma-material interaction models. These efforts will lead to design, installation, and evaluation of an advanced divertor for DIII-D to enable highly dissipative divertor operation at core density (n e/n GW), neutral fueling and impurity influx most compatible with high performance plasma scenarios and reactor relevant plasma facing components (PFCs). This paper highlights the current progress and near-term strategies of boundary/PMI research on DIII-D.
Many ideas for liquid surface PFCs are for divertors. First walls are likely to be more challenging technologically because long flow paths are necessary for fast flowing systems and the first wall must be an integral structure with the blanket. Maximum tolerable heat loads are a critical concern. This paper describes several processes at work in walls with fast-flowing or slow-flowing liquid plasma-facing surfaces, and the considerations imposed by heat transfer and the power balance for the PFC as well as the structure needed for an integrated first wall and blanket, and uses thermal modeling of a generic PFC structure to illustrate the issues and support the conclusions.
Until 2012, Sandia participated regularly in non-fusion R&D that was supported primarily through our collaborations with companies in the DOE program for Small Business Innovative Research but also in some work-for-others contracts. In this work, funds were recovered from collaborating institutions for the staff time and materials used, but FES had supported the facility itself and in doing so enabled the contributions to the non-fusion R&D below.
