Stability boundaries and development of the ITER baseline scenario

Plasmas stable to $m/n=2/1$ tearing modes (TMs), in the ITER baseline scenario (IBS) with ITER similar $I_p/aB_T$, have been demonstrated in DIII-D, evolving to stationary conditions. Previous studies showed the possibility that long pulse IBS plasmas might be susceptible to TMs. However within a defined stability boundary, most of these longer duration discharges have achieved stationary conditions ($\Delta\tau_{duration}\leq 7.5$~s and $\leq 11\tau_R$) with high Co-beam torque and without the need for ECCD. To mitigate 2/1 TMs at reduced torque, broad ECCD deposition was found to be most effective when positioned near the $q=3/2$ flux surface, although a subset of low torque pulses were also obtained without ECCD. The DIII D internal coils (I coils) were used to achieve ELM suppression in IBS plasmas with ECCD at $q_{95}=3.15$ for durations up to 1 s with only the upper row of I coils, providing a broad $n=3$ spectrum. Conditions stable to $n=1$ tearing modes in IBS discharges and the effect of $Z_{eff}$, density, and other parameters are discussed.