Isotope Effects on Intrinsic Toroidal Rotation and Rotation Reversals

The isotope mass effect on intrinsic rotation was investigated in JET Ohmic plasmas matched in H, D and T. This was the first time that accurate measurements of main ion rotation were obtained in Tritium plasmas. It was concluded that intrinsic rotation is affected by ion mass. Counter-current rotation increases with ion mass, which is a core effect. With respect to density scans, that covered both the linear and the saturated Ohmic confinement regimes, the observations can be summarized as follows. As the density increases, two rotation reversals are seen for each isotope mass. Within the experimental uncertainties the first reversal, from peaked/flat to hollow rotation profiles, occurs at the same density. The critical density for the second reversal, from hollow to peaked/flat rotation profiles, is shifted with ion mass. This results in Tritium requiring a higher density for access to the second regime of co-current rotation.