Speaker
Vladimir D. Pustovitov
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P2.1036.pdf
Filament representation of the plasma in the tokamak disruption studies
V.D. Pustovitov
U
National Research Centre Kurchatov Institute and National Research Nuclear University
MEPhI (Moscow Engineering Physics Institute), Moscow, Russia
It is well known that the plasma-produced poloidal field outside the tokamak plasma
can be quite accurately approximated by the field of a set of the distributed toroidal currents
(filaments or circular loops) [1]. This is justified by referring to the fact that the tokamak plasma
looks like a toroidal current and needs a proper electromagnetic treatment for suppressing the
outward expansion. An additional argument in favour of such image is that, with a desirable
axisymmetry, the magnetic field due to the plasma poloidal current always remains completely
‘hidden’ inside.
The force balance requires that this current must vary reacting on the plasma changes. It
will inevitably generate the poloidal electric field outside, which is not accounted for in the
models with plasma replaced by current filaments. Such models are often used in calculations
of the disruption-induced forces on the tokamak wall [2–5]. Here we analyze the accuracy of
this approach.
We treat the problem within the standard large-aspect-ratio tokamak model assuming
that both the plasma and the wall are circular in the perpendicular cross-sections. The magnetic
pressure on the wall during thermal quench (TQ) and current quench (CQ) is analytically
calculated by following the approach described in [6]. The rapid events are considered when the
penetration of the plasma-driven perturbation through the vessel outwards is weak due to the
skin effect in the wall. The derived formulas allow comparison of the disruption-induced forces
calculated differently: with plasma described by the MHD equilibrium equations as opposed to
the plasma modelled by a set of filaments. The differences in the results are discussed and
explained. It is explicitly demonstrated that the filamentary model of the plasma (or disregard
of the poloidal current in the plasma) gives unacceptably large errors in the simulated forces for
both TQs and CQs.
[1] B. J. Braams, Plasma Phys. Control. Fusion 33, 715 (1991).
[2] R. Albanese, et al., Fusion Eng. Des. 94, 7 (2015).
[3] V. Rozov and A. Alekseev, Nucl. Fusion 55, 083022 (2015).
[4] S. N. Gerasimov, et al., Nucl. Fusion 55, 113006 (2015).
[5] R. Roccella, et al., Nucl. Fusion 56, 106010 (2016).
[6] V. D. Pustovitov and D. I. Kiramov, submitted to Plasma Phys. Control. Fusion (2018).
