DIII-D: Closing the Gaps to Future Fusion Reactors

The DIII-D program is pursuing an ambitious plan to close critical design gaps to a Fusion Pilot Plant (FPP), including integrating performance and exhaust solutions, addressing plasma interacting material and technology issues, and resolving the path to ITER and a high fusion gain pulsed FPP. Increasing ECH power to 10 gyrotrons, with extension to 20 by FY28, will provide low-torque electron heating and profile control, while new reactor-relevant solutions for efficient off-axis current drive will be pioneered by high-field-side LHCD, helicon waves and top launch ECCD to enable FPP steady-state scenarios. A series of closed, modular divertors will allow exploration of innovative plasma solutions for combined core and plasma exhaust in high opacity/low collisionality regimes made possible by stronger shaping to maximize the pedestal pressure and density along with a BT rise to 2.5 T. A dedicated material interaction test station will help close gaps in compatible fusion materials. The control and mitigation of plasma transients will be addressed through a passive runaway electron dissipation coil and exploration of novel disruption mitigation techniques (EM launch, hyper-velocity W pellets,…). An exciting option for a negative triangularity path is being assessed.