Scalings of Spontaneous Rotation in the JET Tokamak
This paper summarises and highlights experimental results from recent JET studies on intrinsic rotation. Levels of intrinsic rotation measured in JET H-modes are generally lower than expected from scaling laws for co-current rotating plasmas that predict that rotation increases with normalised beta. Both co- and counter-current is observed and there aren't significant differences between rotation observed in L-mode and H-mode plasmas. Experimentally several factors have been found to influence intrinsic rotation, such as fast ion losses and toroidal field ripple, suggesting that different physics mechanisms are at play to drive intrinsic rotation and that these should be taken into consideration when extrapolating to future devices. It is also apparent from JET data that independent mechanisms may be driving rotation in the edge and the plasma core. Toroidal field ripple, in particular, was found to have a significant effect on the intrinsic rotation of plasmas without momentum input. JET results suggest that ITER intrinsic rotation may be substantially less than what was previously predicted by the multi-machine rotation scaling of ref.