Advancement of Wide Pedestal Quiescent H-mode Scenario at Zero Torque to ITER-like Shape*

Recent experiments on DIII-D have advanced the operational limits of wide pedestal QH-mode plasmas towards increased ITER relevance by demonstrating well-matched plasma shape and net zero injected torque simultaneously. Quiescent H-modes (QH-modes) are a candidate regime for ITER and future reactors because they maintain a stationary pedestal without ELMs via additional edge transport generated by either an edge harmonic oscillation (EHO), broadband turbulence, a limit cycle oscillation (LCO), or some combination thereof. Comparing to the traditional double null shape, the ITER-like shape is shown to have 1) a narrower pedestal width, 2) lower frequency LCOs, yet larger density fluctuations, and 3) larger ExB shear in the inner Er well pedestal region. In the peeling-ballooning stability space, the ITER-like shape operates far from the kink/peeling boundary, suggesting much higher power and possibly wider pedestal operation can be achieved in future experiments. The H98y2 confinement factor was shown to increase with pedestal width, suggesting a favorable scaling for ITER in this regime.