Transport modeling of the DIII-D high β_p scenario and extrapolations to ITER steady-state operation

Transport modeling of a proposed ITER steady-state scenario based on DIII-D high poloidalbeta (β_p) discharges finds that ITB formation can occur with either sufficient rotation or a negative central shear q-profile. The high β_p scenario is characterized by a large bootstrap current fraction ( 80%) which reduces the demands on the external current drive, and a large radius internal transport barrier which is associated with excellent normalized confinement. Modeling predictions of the electron transport in the high β_p scenario improve as q₉₅approaches levels similar to typical existing models of ITER steady-state and the ion transport is turbulence dominated. Typical temperature and density profiles from the non-inductive high β_p scenario on DIII-D are scaled according to 0D modeling predictions of the requirements for achieving a Q = 5 steady-state fusion gain in ITER with "day one" heating and current drive capabilities. Then, TGLF turbulence modeling is carried out under systematic variations of the toroidal rotation and the core q-profile. A high bootstrap fraction, high β_p scenario is found to be near an ITB formation threshold, and either strong negative central magnetic shear or rotation in a high bootstrap fraction are found to successfully provide the turbulence suppression required to achieve Q = 5.