Scaling and manipulation of turbulent structures in the torsatron TJ-K

In this work, the scaling properties of characteristic turbulent structures and the influence of sheared plasma flows on them were investigated. Analyses were carried out on data with high temporal resolution, which were acquired simultaneously from an 8 x 8 Langmuir probe array. The analyses reveal the spatio-temporal evolution of propagating density structures. For small ion masses, the scaling properties of these characteristic structures turned out to be consistent with the prediction for drift-wave turbulence. The influence of shear flows on turbulence was demonstrated in simulations and in the experiment. In order to study the mechanism of the transport reduction due to shear flows, electric fields were induced. It was shown that shear flows change the correlation time and the cross-phase between poloidal electric field and density fluctuations rather than the correlation length as it is usually assumed. (Orig.)