GPU-accelerated analysis of vertical instabilities in ITER including three-dimensional volumetric conducting structures

Abstract

In this paper, we study the axisymmetric vertical instability of elongated configurations, including the effect of volumetric three-dimensional conducting structures surrounding the plasma. In order to deal with the huge computational models arising from the realistic geometrical description, a GPU-based (graphics processing units) acceleration is pursued. The method is applied to some ITER configurations, for which the open-loop growth rates, the input-output transfer functions and the gain and phase margins are computed.

3D passive stabilization of n = 0 MHD modes in EAST tokamak

“…The CarMa0 code 6 is the n = 0 particularization of the CarMa code 8 , successfully applied to several devices and experimentally validated 9 . It is based on the coupling surface approach: a surface S is introduced in between the plasma and the conductors.…”

“…An equivalent surface current distribution on S is computed, able to provide the same magnetic field as plasma outside S . Assuming no active coils, the final form of the model 6 is:…”

“…The aim of this paper is to prove that this happens even with the new geometry of the conductors of EAST, providing a deep physical insight in the phenomenon to support this conclusion. To this purpose, a suitable computational tool will be used, called CarMa0 6 , which has the unique feature of including the effect of 3D conductors on the evolution of fusion plasmas. A careful analysis of the stabilizing current density patterns in the structures and the derivation of an equivalent axisymmetric model allows a clear interpretation and a precise quantification of this effect.…”

Plasma stability theory including the resistive wall effects

“…To distinguish between them, one has to separate the sinks and sources of the momentum and energy. From various unknowns, the wall influence on the plasma dynamics must be the easiest to evaluate with codes such as CarMa [69–71, 108, 116, 118, 120, 121], taking rigorous account of the skin effect and 3-D features of the conducting structures surrounding the plasma.…”

“…This extends even to the majority of stability codes. For example, the walls are often treated as axisymmetric and poloidally continuous [49,76,78,88,108,116,[118][119][120][121]. Sometimes, the 2-D wall approximation is qualitatively not good enough to describe even the wall response itself (i.e.…”