Understanding disruptions in tokamaks

Abstract

This paper describes progress achieved since 2007 in understanding disruptions in tokamaks, when the effect of plasma current sharing with the wall was introduced into theory. As a result, the toroidal asymmetry of the plasma current measurements during vertical disruption event (VDE) on the Joint European Torus was explained. A new kind of plasma equilibria and mode coupling was introduced into theory, which can explain the duration of the external kink 1/1 mode during VDE. The paper presents first results of numerical simulations using a free boundary plasma model, relevant to disruptions.

Analytical model of wall forces produced by kink perturbations in tokamaks

“…The sideways force was found to be largest when cs w $ 1, and this was claimed to be in qualitative agreement with the simulations using the M3D code. 17 The proposed formula, however, apparently disagrees with other relevant results [2][3][4][5]7,9,19,23 in the proper limits of ideal wall or no-wall. In particular, the expressions for the force in Refs.…”

“…This is a local volume density of the force, but estimates are typically presented for the net horizontal force [2][3][4][5][9][10][11][12][13][14][15][16][17][18][19]21,23,30,31 …”

“…[1][2][3][4][5][6][7][8][9][10][11][12][13] Evaluations for ITER give worrisome numbers at the level of hundred MN. [12][13][14][15][16][17][18][19][20][21] There are several approaches [2][3][4][5]7,9,17,19,[21][22][23][24] to calculating the instability-induced electromagnetic forces on the vessel components in tokamaks, but some issues remain unresolved. 13,20 One of them was recently raised in Refs.…”

Edge equilibrium code for tokamaks

“…(33)-(35) at the plasma-vacuum interface are not different from the matching conditions at the virtual boundary, but this mode of operation has not been tested yet. It will be fully developed in conjunction with simulations of the vertical disruptions on EAST tokamak, where the Hiro currents 37 were measured for the first time.…”

“…This emerging objective requires fast equilibrium reconstruction together with fast simultaneous transport simulations and variance analysis. 6 Another important topic is the simulation of vertical disruptions and wall touching vertical mode 37 where the use of adaptive grids is necessary for reproducing the Hiro currents.…”