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

Transport modeling of a proposed ITER steady-state scenario based on DIII-D high poloidal-beta (βp) discharges finds that ITB formation can occur with either sufficient rotation or a negative central shear q-profile. The high βp 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 βp scenario improve as q95 approaches 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 βp 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 βp 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.