Exploring a broad spectrum of design options for DEMO

In the pursuit of realistically achievable design options for demonstrating fusion electricity generation and tritium self-sufficiency in a device to follow ITER, it is vital to explore as fully as possible the available design space and technology options which might lead to a fusion power plant within the timescales envisioned by the EU Roadmap to Fusion Energy. The usual tool for exploring this space is a systems code, such as PROCESS, which seeks to model all important plant systems and physics to provide an integrated power plant design point. However, currently many of these models are tied to assumptions of ITER-like technology and therefore tend to lead to ITER-like plant solutions. This contribution describes a broader set of plant configurations being considered alongside the main baseline design, investigating the impacts on design and costs of designing for (1) flexi-pulsed-steady-state operation, (2) double-null divertors, and (3) the use of high-temperature superconductors. The focus of the work presented here, however, is on (4) advanced magnetic configurations such as snowflake and super-X divertors. We discuss the modifications necessary for the systems code to simulate these configurations and their performance, particularly the divertor geometry and power handling capability; rapid engineering analysis of TF and PF coil positions which can achieve both the required equilibrium and remote-handling access; and initial wider analysis of the physics, neutronics, and other considerations. The reductions in wall area available for breeding tritium affect the choice of blanket technology, and remote handling considerations have a strong impact on the configurations which can be considered reasonable from an engineering and availability perspective. The benefits, disadvantages, risks, and power plant relevance of each configuration over the baseline DEMO design are discussed.