Speaker
Alexander Martynov
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P2.1038.pdf
External kink mode stability in a tokamak with a finite current density
in the SOL
A.A. Martynov1,2, S.Yu.Medvedev1,2, S.V. Konovalov2, A.S. Kukushkin2,3,
A. Loarte4, A. R. Polevoi4, J.C. Hillesheim5, S. Saarelma5 and JET Contributors*
1
Keldysh Institute of Applied Mathematics, Moscow, Russia
2
National Research Centre Kurchatov Institute, Moscow, Russia
3
National Research Nuclear University MEPhI, Moscow, Russia
4
ITER Organization, 13067 St. Paul Lez Durance Cedex, France
5
CCFE, Culham Science Centre, Abingdon OX14 3DB, United Kingdom
A conducting plasma outside the separatrix affects the stability of the external kink
modes in tokamaks with a divertor. Large values of the pressure gradient and current density
in the scrape-off layer (SOL) region driven by both the thermoelectric current between the
divertor plates with different plasma temperatures and the bootstrap current can be expected
according to the transport simulations [1]. Here we apply the equilibrium and stability codes
CAXE-SOL/KINX-SOL [2] to study in a systematic way the dependence of the stability of
the peeling-ballooning (PB) mode localized in the pedestal region on the plasma parameters
in the SOL. We show that the limiting pressure pedestal height is not very sensitive to the
pressure gradient distribution over the SOL and pedestal region, but a high current density
parallel to the magnetic field in the SOL leads to the instability of the external kink modes
localized at the conducting plasma edge. The development of such instabilities can be an
alternative trigger for the ELMs, in addition to the standard model based on destabilization of
the Peeling-Ballooning (PB) modes. For reconstructed JET H-mode equilibria including the
pedestal, the possibility of ELMs being triggered due to the existence of currents in the SOL
has been studied and found to be a viable mechanism, particularly for the cases when the
pedestal height is insufficient to destabilize the PB modes [3]. The same finding is
reproduced for typical NSTX H-mode plasma conditions. Since accurate measurements and
estimates of the current density in the SOL are not available, the stability limits and their
sensitivity to variations of the current profiles and of the width of the conducting plasma layer
outside the separatrix are investigated. This analysis will also be performed in the paper for
ITER plasma equilibria in reference H-mode operational conditions including various levels
of SOL current density.
ITER is a Nuclear Facility INB-174. The views and opinions expressed herein do not
necessarily reflect those of the ITER Organization.
[1] A. Loarte, F. Liu, G.T.A. Huijsmans, A.S. Kukushkin and R.A. Pitts. J. Nucl. Mater. 463 (2015) 401.
[2] S.Yu. Medvedev et al. Plasma Phys. Control. Fusion 59 (2017) 025018.
[3] C. Bowman et al. Nucl. Fusion 58 (2018) 016021.
*
See the author list of “X. Litaudon et al. 2017 Nucl. Fusion 57 102001”
