Upgrading DIII-D to Close Physics Gaps to Future Fusion Reactors

A proposed ten-year timeline of upgrades will allow DIII-D to reach its full potential to narrow the existing physics gaps to a Fusion Pilot Plant (FPP). Large strides in closing core-edge gaps can be made by increasing the elongation, triangularity and volume to allow higher current and density, which can be combined with a magnetic field rise to 2.5 T to achieve ITER-relevant pedestal collisionality and density simultaneously. Raising the heating power is also critical to attain high beta & current drive at the higher field & density, while new methods of FPP-relevant off-axis current drive will be investigated. A modular closed divertor will enable exploration of multiple dissipation concepts, including increased baffling for better core/edge isolation and an option for a long-legged divertor. New solid PMI materials can be rapidly prototyped using rapid tile change-out, robotics, DiMES and WITS to accelerate the theory/experiment validation cycle. Midplane 3D coils, 2D/3D power supplies, control upgrades and a disruption mitigation testbed are planned for more aggressive development of reactor transient solutions. With these new capabilities, DIII-D can address critical challenges to prepare for ITER and resolve the physics basis for a FPP.