Influence of toroidal rotation on transport and stability in hybrid scenario plasmas in DIII-D

We report the results of the first experiments on the DIII-D tokamak to examine the dependence of the transport and stability characteristics of ITER hybrid scenario plasmas on the toroidal flow (or rotation) of the plasma. With the new DIII-D capability to independently vary the neutral beam torque and power, the central rotation has been reduced by as much as a factor of 4.6 compared with discharges with unidirectional beams. Although energy confinement decreases and the m/n = 3/2 NTM amplitude increases for low rotation speed, the fusion performance figure of merit, G-βNH89p/q952, still exceeds the value required on ITER for Qfus = 10. These observations provide optimism about the projections of the hybrid scenario to low rotation plasmas in ITER, but they also indicate the need for a better understanding of the physics of toroidal rotation in order to project present-day results to future experiments