Bifurcation behaviour of resonant magnetic perturbation control of edge localized modes in tokamaks: nonlinear simulation results

Abstract

In this article, some novel results of two fluid nonlinear simulations on the control of edge localized modes (ELMs) in tokamaks by resonant magnetic perturbations (RMPs) are presented. Many experiments around the world have demonstrated that RMPs are effective in possibly mitigating or even completely suppressing strong (type I) ELMs that would seriously degrade confinement and could cause other heat-flux problems in both present (e.g. JET) and planned future tokamaks (ITER). Our simulations demonstrate that non-axisymmetric RMPs with toroidal mode numbers n = 2 , 3 , 4 and suitable field-strengths (kAturns) at the plasma wall imply significant bifurcations in their ability to mitigate or even suppress type-I ELMs, qualitatively similar to RMP effects on ELMs reported in experiments. This article is part of a discussion meeting issue ‘H-mode transition and pedestal studies in fusion plasmas’.

H-mode transition and pedestal studies

“…Thyagaraja et al [ 4 ] report CUTIE simulation results on edge localized mode (ELM) control by resonant magnetic perturbations (RMP) fields, highlighting the bifurcation phenomenon in the RMP amplitude in ELM suppression; Andrew et al [ 5 ] present the first experimental results of transition from L-mode to dithering H-modes on the compact, spherical tokamak ST40 and extend the L-H transition predator–prey model to include the contribution from MHD instabilities and pedestal pressure gradient. A comprehensive review of the role of sheared plasma flow on the evolution of confinement from the L-H transition to the H-mode density limit is provided by Diamond et al in [ 6 ].…”