Momentum Transport Studies in JET H-Mode Discharges with an
Enhanced Toroidal Field Ripple
P.C. de Vries, T.W. Versloot, A. Salmi, M-D. Hua, D.H. Howell, C. Giroud,
V. Parail, G. Saibene, T. Tala and JET EFDA contributors
The study of plasma rotation and momentum transport has gained interest over the last few
years as rotation is thought to play an important role in the stability of Tokamak plasmas while it
may also affect transport properties via the stabilization of turbulence. A proper understanding of
all aspects that affect the rotation of Tokamak plasmas, in particular rotation sources and
momentum transport, is important if one wants to make an accurate prediction of the rotation in ITER.
The assumption that momentum transport is similar to the turbulence driven ion heat transport
is a strong simplification and usually in JET it is found that the effective momentum diffusivity
is significantly smaller than the ion heat diffusivity. This observation can be attributed to the
existence of an inward momentum pinch. Clear experimental evidence for such a momentum
pinch in JET was obtained in earlier experiments. JET has the unique capability to change its Toroidal
Field (TF) ripple. It was shown that an increased TF ripple has a strong impact on the overall
toroidal rotation at JET. This paper will not deal in detail with mechanisms of TF ripple induced
torque on the plasma, which is described elsewhere, but utilize TF ripple as a tool, in order to reveal
the impact of the momentum pinch on the rotation profiles in H-mode JET discharges. Besides
this an estimation of the magnitude of the momentum pinch can be made for each entry in the
JET rotation database , which enables us to look into the basic scaling of this parameter.
Preprint of Paper to be submitted for publication in Proceedings of the
37th EPS Conference on Plasma Physics, Dublin, Ireland.
(21st June 2010 - 25th June 2010)