Events at Physics
Tokamak fusion reactors will require predictive, integrated models to optimize performance while maintaining robustness against disruptions. The STEP (Stability, Transport, Equilibrium, & Pedestal) module, developed in OMFIT, predicts stable equilibria self-consistently with core-transport and pedestal calculations by coupling together the following codes: ONETWO, TGYRO, EFIT, CHEASE, EPED, DCON, GATO, and CHEF (a current-drive, heating, & fueling module). Each code reads and writes data from a centralized IMAS data structure, allowing codes to be run in arbitrary order and enabling open-loop, feedback, and optimization workflows. Core-pedestal calculations with STEP have been validated against the equilibria and profiles of individual DIII-D discharges and the confinement times of the H98,y2 database. In addition, such workflows have been used to assess performance in ITER and the suppression of turbulence in DIII-D negative-triangularity plasmas. Recent enhancements to STEP have permitted accurate simulations of more exotic scenarios, in particular a negative-central-shear DIII-D scenario. In the near future, STEP calculations of stability in existing and planned tokamak scenarios will allow for the optimization of heating and current drive to maximize plasma pressure while maintaining MHD stability.