Preventing H-mode with Negative Triangularity to Improve Exhaust Handling at High Core Plasma Performance

Negative triangularity (NT) plasmas are typically characterized by high core plasma performance while simultaneously maintaining an L-mode edge. In this work, we explore the potential to establish this regime in reactor-like conditions through two studies. First, we explore the potential for robust NT L-mode reactor operation by modeling infinite-n ballooning stability as a function of internal profiles and equilibrium shape using a combination of the CHEASE and BALOO codes. These modes prevent the growth of pedestal gradients while still allowing for strong core performance, and are found to be essential to edge behavior in the simulated NT plasmas. Second, the gradient-limiting mechanism of the infinite-n ballooning modes is expanded to 1D modeling of NT reactor scenarios using the STEP code. Self-consistent reactor operating scenarios are established by comparing converged STEP simulations with POPCON-style regime descriptions, demonstrating a wide range of conditions accessible for an NT reactor. Comments on the integration of these high performance core scenarios with a reactor-friendly exhaust scheme are presented, highlighting the potential benefits of an L-mode edge in the reactor environment.