Halo current

This article represents an overview of halo current which is the most dangerous current for plasma facing components. The halo current flows into the vacuum vessel from the plasma through the plasma facing components. It induces a large electromagnetic force through the coupling with the toroidal field. The halo current is driven by a fast change of magnetic flux surfaces due to a vertical displacement event (VDE) and the current quench. The toroidal asymmetry, the width of current channel and the scalings have been investigated recently. Some methods of reduction and/or avoidance of halo current are proposed. (author)