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

The DIII-D program is pursuing an ambitious plan to rapidly close critical design gaps to a Fusion Pilot Plant (FPP). Over the next three years, seven major facility upgrades will allow DIII-D to access reactor-relevant physics regimes with increased flexibilities. The electron cyclotron heating will be doubled to 10 gyrotrons totaling 7 MW to furnish low-torque electron heating and profile control, and the NBI power will be increased to 25 MW using new RF sources. The upper Shape & Volume Rise divertor will be swapped out for a Dissipation Focused Divertor to investigate detachment front stability while preserving high core confinement using upstream cryopumping. Additionally, a closed, pumped lower divertor at large major radius will allow negative triangularity plasmas to explore detached conditions. The installation of a unique runaway electron mitigation coil and the first test of spin polarized fusion in a magnetically confined fusion device are also planned. Finally, in 2027 there will be a full wall change out of the graphite walls to test the compatibility of reactor relevant materials (chosen with input from the community) with advanced core-edge scenarios. Together these elements will enable reactor solutions to be pioneered and projected with confidence.