Low aspect ratio next-step tokamak design studies at PPPL

Recent U.S. magnetic fusion strategic planning reports all recommend that the U.S. should pursue innovative science and technology to enable construction of a Fusion Pilot Plant (FPP) that produces net electricity from fusion at reduced capital cost. Compact tokamaks have been proposed as a means of potentially reducing the capital cost of an FPP. However, compact steady-state tokamak FPPs face the challenge of integrating a high fraction of self-driven current with high core confinement, plasma pressure, and high divertor parallel heat flux. Such integration has not been previously accessed nor is it presently planned to be accessed. This integration is sufficiently challenging that construction and operation of a dedicated sustained-high-power-density (SHPD) tokamak facility has been proposed by the U.S. community to close this integration gap. In this presentation recent systems studies for superconducting low aspect ratio FPPs will be summarized, a preliminary SHPD configuration with substantial flexibility in aspect ratio, shape, and divertor will be discussed, and possible future FPP R&D in the U.S. program and at PPPL will be considered.