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A magnetic field configuration in a tokamak that allows the removal of impurities from the plasma in both the upper and lower parts of the vacuum vessel by a divertor. By installing an additional poloidal magnetic coil, the magnetic lines of the last closed magnetic surface, called the separatrix, are crossed. The particles located at the separatrix are then guided beyond the crossing point, called the X-point, and from there on to the divertor, which takes care of their removal from the plasma. In this way, the purity of the plasma is maintained. The double-null configuration allows the divertor to be installed in both the top and bottom of the vacuum chamber. This spreads the heat load between two divertor plates.