Integrated modeling of high β_N steady state scenario on DIII-D

Theory-based integrated modeling validated against DIII-D experiments predicts that fully non-inductive DIII-D operation with β_N > 4.5 is possible with certain upgrades. IPS-FASTRAN is a new iterative numerical procedure that integrates models of core transport, edge pedestal, equilibrium, stability, heating, and current drive self-consistently to find steady-state (d/dt = 0) solutions and reproduces most features of DIII-D high β_N discharges with a stationary current profile. Projecting forward to scenarios possible on DIII-D with future upgrades, the high q_min > 2 scenario achieves stable operation at β_N as high as 5 by using a very broad current density profile to improve the ideal-wall stabilization of low-n instabilities along with confinement enhancement from low magnetic shear. This modeling guides the necessary upgrades of the heating and current drive system to realize reactor-relevant high β_N steady-state scenarios on DIII-D by simultaneous optimization of the current and pressure profiles.