Abstract
Several parametric scans have been performed to study momentum transport on JET. A neutral beam injection
modulation technique has been applied to separate the diffusive and convective momentum transport terms. The
magnitude of the inward momentum pinch depends strongly on the inverse density gradient length, with an
experimental scaling for the pinch number being -Rvpinch/χφ = 1.2R/Ln +1.4. There is no dependence of the pinch
number on collisionality, whereas the pinch seems to depend weakly on q-profile, the pinch number decreasing with
increasing q. The Prandtl number was not found to depend either on R/Ln, collisionality or on q. The gyro-kinetic
simulations show qualitatively similar dependence of the pinch number on R/Ln, but the dependence is weaker in
the simulations. Gyro-kinetic simulations do not find any clear parametric dependence in the Prandtl number, in
agreement with experiments, but the experimental values are larger than the simulated ones, in particular in L-mode
plasmas. The extrapolation of these results to ITER illustrates that at large enough R/Ln > 2 the pinch number
becomes large enough (>3–4) to make the rotation profile peaked, provided that the edge rotation is non-zero. And
this rotation peaking can be achieved with small or even with no core torque source. The absolute value of the
core rotation is still very challenging to predict partly due to the lack of the present knowledge of the rotation at the
plasma edge, partly due to insufficient understanding of 3D effects like braking and partly due to the uncertainties
in the extrapolation of the present momentum transport results to a larger device.
Original language | English |
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Journal | Nuclear Fusion |
Volume | 51 |
Pages (from-to) | 123002 |
ISSN | 0029-5515 |
DOIs | |
Publication status | Published - 2011 |