Exploration of steady-state scenarios for the Fusion Development Facility (FDF)

A Fusion Nuclear Science Facility (FNSF) has to operate at $10^5$ times longer duration than that of present tokamak discharges. The scalability of plasma sustainment to such a long time is an issue that needs to be resolved by scientific understanding. We carry out steady-state (SS) scenario development of the FDF (a candidate for FNSF-AT) using an iterative process toward a self-consistent solution via alternating temperature profiles and current profile evolution. The temperature profile evolves according to a physics-based transport model GLF23. SS requires large off-axis current drive (CD). To achieve this with no NBI is highly challenging. It however simplifies tritium containment, increases area for tritium breeding, and avoids costly negative-ion NBI technology. We find that with ECH/ECCD only, too much power is required. A SS baseline equilibrium is found by adding LHCD: $Q_{fus}\sim 4$, $H_{98y2}\sim 1.2$, $f_{BS}\sim 70$\%, $P_{fus}\sim 260$ MW, $P_{EC} =35$ MW, $P_{LH} =21$ MW. The GATO ideal MHD code finds the equilibrium stable to $n=1$ internal kink at $\kappa =2.3$.