Author: Dmitrii I Kiramov
Requested Type: Poster
Submitted: 2018-03-01 11:48:00
Co-authors: B.N. Breizman
NRC "Kurchatov Institute"
Ploshchad' Akademika Kurchatov
Vertical motion of the disruptive plasma plays an important role in the current quench phase of tokamak disruptions. Generation of significant currents in the conductive wall structures and on the open flux surfaces is expected during these events. Past studies claim that the corresponding electromagnetic loads due to the high amplitude of halo currents bound the upper time limit for safe mitigation (~150 ms). Yet it is still unclear whether induction or direct current inflow through the plasma periphery region to the wall is the main mechanism of the plasma current conversion to the wall current.
The disruptive plasma motion is essentially force free since the characteristic timescale of disruption is rather resistive than Alfvenic. That allows us to describe the plasma motion as a sequence of force-free states that evolve in step with magnetic field diffusion, while the force-free constraint determines the plasma velocity profile. This work describes such time-dependent flows and corresponding current profiles in toroidal geometry for purely ohmic dissipation of the plasma current. Our special attention is given to the current evolution on the open magnetic flux surfaces that intersect the first wall.
This work was supported by the U.S. Department of Energy Contracts DEFG02-04ER54742 and DE-SC0016283.