Characterization of Core Transport in Compact Tokamak Reactor Scenarios

Work previously reported at the 2021 APS-DPP meeting [1] identified self-consistent core transport and equilibrium solutions capable of producing 200 MW or more net electric power in a B₀ = 8 T, R_maj = 4 m device. For both pulsed and steady-state scenarios we find there is significant ion thermal transport through the plasma core, even though alpha heating of electrons is the dominant heating source. Additionally, the low collisionality of these plasmas leads to negligible core neoclassical transport. The combination of these conditions then requires that transport be dominated by microturbulence instabilities capable of driving significant ion to electron thermal transport ratios, i.e. ion temperature gradient and/or kinetic ballooning modes. Finally, it is shown that the transport is sufficiently large for these cases that differences in the stiffness predicted by different TGLF saturation rules leads to significantly different scenario predictions. Ongoing work benchmarking TGLF and CGYRO predictions for these cases will be presented, as well as implications for density peaking and core-edge integration.



[1] C. Holland et al, 63rd Annual APS-DPP Meeting, Pittsburgh, PA Nov 8-12, TP11.00103 (2021)