Bayreuth 1998 – scientific programme
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P: Plasmaphysik
P 14: Magnetischer Einschluß III
P 14.2: Talk
Wednesday, March 11, 1998, 14:30–14:45, H 14
Demonstration of the role of E→×B→ flow shear in improved confinement — •S. Jachmich1, G. Van Oost2, and R. Weynants2 — 1Institut für Plasmaphysik, Forschungszentrum Jülich GmbH, 52425 Jülich — 2Laboratoire de Physique des Plasmas, Association “Euratom – Belgian State”, Ecole Royale Militaire – Koninklijke Militaire School, B–1000 Brussels, Belgium
Recent polarisation experiments at Textor–94 clearly show the role of E→×B→ shear in establishing transport barriers. It is observed that the global particle confinement reacts to a reduction of the diffusivity in a narrow radial region, the position of which is strongly correlated to the location of the electric field layer, i.e., that region where the electric field is built up. However the particle transport barrier region shows an internal structure, such that, instead of a single steepening of the density profile, two maxima in the density gradient develop separated by a minimum. This minimum is located where the electric field is maximum, whereas the maximal density response coincides temporarily robust; in particular, if the electric field layer moves radially the density pattern moves accordingly. In this contribution we will compare these experimental findings with various theories of turbulence suppression and with experimental data from other machines. The quantitative comparison of the D(∇ Er) dependence has shown a good agreement with theory. It was also found that the maximal changes in the diffusion coefficient happen at the critical electric field shear, where the theory predicts it to be.