Magnetic structure and transport

Investigations of magnetic field structure and transport have progressed via TEXTOR collaborations. This research covers the change in magnetic topology due to island formation on occasion of a sawtooth crash, impact of global current profile on turbulent transport and the bifurcation nature of confinement. This area of research requires, on one hand, the precise measurement of the magnetic field, which is a unique capability of TEXTOR experiments. At the same time, an advanced theory of turbulent transport and transitions is required and is supplied by Japanese contributions. A general description of the collaboration is provided. Then a typical outcome is explained, taking the case of the formation of a thin current layer at the onset of sawtooth crash as an example. (author)