EXC/3-5 Characterization of the Effective Torque Profile Associated With Driving Intrinsic Rotation on DIII-D

Recent experiments on DIII-D have focused on elucidating the drive mechanisms for intrinsic rotation in tokamak fusion plasmas. For a wide range of DIII-D H-mode plasmas, the effective torque at the edge ( >0.8) associated with the intrinsic rotation shows a dependence on the edge pressure gradient, which is qualitatively consistent with models describing E B shear as a means of creating “residual stress” and in turn driving intrinsic rotation., This is not the full picture, however, as recent probe measurements indicate that additional mechanisms may be necessary to completely understand edge intrinsic rotation generation. The intrinsic torque in the core ( <0.5) of H-mode plasmas appears to be much more complex than the edge. Even though the core intrinsic torque tends to be much smaller than observed at the edge, some examples have been found where it is large enough to modify the rotation profile. For instance, in certain plasmas with electron cyclotron heating, a significant counter intrinsic torque has been observed in the inner region of the plasma. Large intrinsic torques have also been observed in the core of quiescent H-mode (QH-mode) plasmas and hybrid scenario plasmas. Studies of the residual stress with the global gyrokinetic code GYRO, have uncovered a novel result; namely that nonlocal profile variations appear capable of generating large residual stresses and associated momentum flows.