Speaker
Sergey Medvedev
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P4.1060.pdf
Plasma stability in a tokamak with q~1 and forces acting on the
conducting wall during disruption
S.Yu.Medvedev1,2, A.A. Martynov1,2, S.V. Konovalov2, V.E. Lukash2, V.D. Pustovitov2,
R.R. Khayrutdinov2
1
Keldysh Institute of Applied Mathematics, Moscow, Russia
2
National Research Centre Kurchatov Institute, Moscow, Russia
The stability of the tokamak plasma in the process of disruption and the sideways
forces acting on the conducting wall due to the eddy currents are investigated. The plasma is
considered to be isolated from the wall and halo currents are not taken into account. The basis
for calculating the stability is the equilibrium configuration, obtained in the simulation of the
disruption in ITER by the DINA code taking into account the generation of runaway
electrons with the corresponding current profile [1]. A plasma with minor radius of 1 m and
almost circular shape with a large current (> 5 MA) and the safety factor of q ~ 1 is close
enough to the wall of the vacuum chamber at its top so that the ideal kink mode n = 1
becomes stable. Using the stability code KINX [2], the conditions for wall stabilization
(stability gaps) at the Alfvén timescale are determined varying the current profile and the
value of q at the plasma boundary. Taking into account a finite conductivity in the thin wall
approximation, the growth rates of resistive wall modes (RWM), the plasma displacement
structure and the currents induced in the wall are calculated. The sideways force acting on the
wall is determined as the Ampere force from the surface current in a thin wall and the
equilibrium field.
The results of the calculations show that for a peaked current density profile in the
plasma there is a gap of ideal stability at q > 1 and a slow RWM can develop. The resonant
harmonic m = 1 dominates the plasma displacement. The sideways force is almost completely
determined by the interaction of the perturbed poloidal surface current and the toroidal field
in the ITER (5.3T). The magnitude of this force with respect to the maximum of the
perturbed radial field at the plasma boundary corresponds to the analytical model [3], despite
the differences in the displacement structure. A possible development of the model with
allowance for a plasma with open magnetic surfaces interacting with the wall is discussed.
[1] S. Konovalov et al. Integrated Modelling of ITER Disruption Mitigation. 25th IAEA Fusion Energy
Conference, TH/P3-31, St. Petersburg, Russian Federation, 2014.
[2] L. Degtyarev et al. Computer Phys. Commun. 103 (1997) 10-27.
[3] D. V. Mironov, V. D. Pustovitov. Physics of Plasmas 24 (2017) 092508.
