Transport Variations in High q_min>1.5 Plasmas with Heating and Current Drive Actuators

‘Predict-first’ methodology was employed to develop an experimental plan on DIII-D to study the effect of heating and current drive actuators on the current and pressure profiles of high-q_min>1.5, β_N>3 plasmas, with the goal of achieving stable unchanging V_loop profiles as early in the discharge as possible to avoid the appearance of deleterious tearing modes. Predictive transport modeling conducted with TGLF in TRANSP indicated how varying the I_p ramp rate, ECCD timing, and NBI timing would change these profiles. During the experiment, q_min>2 discharges were sustained and their tearing instability, q_min, and performance was altered by these actuators. Changing the I_p ramp rate had little effect on the discharge but applying ECCD and/or NBI earlier increased q_min and improved n=2 tearing stability. TGLF predicted the effect of ECCD but not the other results. Increased fast-ion transport was also observed. Comparison of pre-experiment modeling, experimental results including turbulence data, and post-experiment simulations will be discussed in detail. These results will be used to validate transport models in this regime and to prepare for the upcoming 2019 campaign when increased off-axis co-I_p NBI power will be available.