First Measurements of Hiro Currents in Vertical Displacement
 Event in Tokamaks

Authors: Hao Xiong, Guosheng Xu, Huiqian Wang, 
Leonid E. Zakharov, Xujing Li

Abstract: Specially designed tiles were setup in the 2012 campaign of the EAST tokamak, to directly measure the toroidal surface currents during the disruptions. Hiro currents with direction opposite to the plasma currents have been observed, confirming the sign prediction by the Wall Touching Vertical Mode (WTVM) theory and numerical simulations. During the initial phase of the disruption, when the plasma begins to touch the wall, the surface currents can be excited by WTVM along the plasma facing tile surface, varying with the mode magnitude. The currents are not observed in the cases when the plasma moves away from the tile surface. This discovery addresses the importance of the plasma motion into the wall in vertical disruptions. WTVM, acting as a current generator, forces the Hiro currents to flow through the gaps between tiles. This effect, being overlooked so far in disruption analysis, may damage the edges of the tiles and is important for the ITER device.
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Submitted to: Physics of Plasmas
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Download PPPL-5129 (pdf 2 MB 7 pp)
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