Electric fields and currents in the detached regime of a tokamak

The structure of currents and electric fields in the edge tokamak plasma is analysed for detached regimes of a tokamak. Strong electric fields in the divertor regions and near the X-point are typical for detached regimes. It is shown that the value of the poloidal electric field in the regions with the temperature 1-2 eV is determined by the Spitzer conductivity and parallel currents. The latter are a combination of thermal and Pfirsch-Schluter (PS) currents. The E x B drifts have a significant impact on the distribution of the plasma in the divertor. Stability of the detached regimes with strong electric fields is also analysed. It has been demonstrated that the so-called PS instability caused by PS current can develop in the cold low-temperature regions of the detached divertor.