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

Abstract

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, , 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.

Development of advanced inductive scenarios for ITER

“…Given this, it is not too surprising that drift-wave models such as GLF23 and the Weiland model had difficulty reproducing the electron and ion temperature profiles in these plasmas. The ion temperature variation in DIII-D plasmas with an intentional reduction in the applied torque shows the variation in the ion temperature is described well by the GLF23 model only when the effects of € E × B shearing are included in the calculation [23].…”

Ion temperature profile stiffness: non-linear gyrokinetic simulations and comparison with experiment

“…While improved global confinement in hybrid scenarios due to flow shear has been observed at DIII-D [22], experiments involving JET standard H-modes showed a lack of significant variation in global confinement even when significantly varying the rotation profiles and maintaining constant total power [23].…”

Observation of ion cyclotron range of frequencies mode conversion plasma flow drive on Alcator C-Mod

“…Tokamak-60 Upgrade (JT60-U) [9] and Joint European Torus (JET) [10], and 50-60 km/s per MW in medium-sized tokamaks like ASDEX-Upgrade [11] and DIII-D [12]. However, for ITER and future reactors, the beam energy will be significantly higher in order to penetrate the expected higher density plasma and larger machine size.…”