Code JOREK Research Articles

Nonlinear MHD simulations of edge-localized-modes in JET

Nonlinear magneto-hydrodynamic (MHD) simulations with the JOREK code may be used to improve our understanding of edge-localized-modes (ELMs) (Huysmans and Czarny 2007 Nucl. Fusion 47 659–66, Huysmans et al 2009 Plasma Phys. Control. Fusion 51 124012, Pamela et al 2010 Plasma Phys. Control. Fusion 52 075006). These H-mode related instabilities may cause some damage to the tungsten divertor of ITER (Bazylev et al 2007 Phys. Scr. T128 229–33), and it was demonstrated experimentally that the ELM energy losses increase with both machine size and decreasing collisionality (ITER Physics Basis Editors and ITER EDA 1999 Nucl. Fusion 39 2175, Loarte et al 2003 Plasma Phys. Control. Fusion 45 1549–69). In sight of producing simulations of ELMs in ITER, in order to give some predictions of ELM size and divertor heat fluxes in the future device, simulations first need to be quantitatively validated against the experimental data of present machines. This paper presents simulations of ELMs in the JET tokamak for the low-collosionality type-I ELMy H-mode pulse #73569. The simulation results are compared with experimental data to provide a qualitative validation of the simulations. This comparison comprises the dynamics of filaments and divertor heat fluxes, the effect of resistivity and collisionality on ELM energy losses and the observation of ELM precursors prior to the pedestal collapse.

Influence of poloidal equilibrium rotation in MHD simulations of edge-localized modes

In nonlinear MHD simulations of edge localized modes (ELMs) with the code JOREK, a strong m = n = 0 poloidal flow localized in the H-mode pedestal region shears density filaments off the separatrix. This flow is nonlinearly induced by the ballooning instability (Huysmans and Czarny 2007 Nucl. Fusion 47 659, Huysmans et al 2009 Plasma Phys. Control. Fusion 51 124012). An approach of the reduced resistive MHD equations used in JOREK leads to an analytical interpretation of the equilibrium flow in both circular and X-point plasmas. Transitions between two different flow structures have been found. Similar transitions between equilibrium flow states had been predicted by Strauss (1995 Phys. Plasmas 2 1229). Finally, results concerning the influence of the equilibrium flow on the linear and nonlinear stabilities of the ELM are presented. ELM-like multiple crashes were simulated.

Magnetohydrodynamics modelling of H-mode plasma response to external resonant magnetic perturbations

The response of an H-mode plasma to Resonant Magnetic Perturbations (RMPs) generated by so-called “I-coils” in DIII-D experiments on type I edge localized modes suppression is modelled using the nonlinear reduced magnetohydrodynamics (with zero-β, i.e. zero plasma temperature, in the version used here) code JOREK in X-point geometry. JOREK self-consistently advances in time the magnetic flux, vorticity, and plasma density in the presence of the RMPs. Without any toroidal rotation, the magnetic response from the plasma does not significantly modify the islands widths. A radial convective E⃗×B⃗ plasma transport is observed to occur in the presence of the RMPs. The possibility that this mechanism could explain the enhanced density transport observed experimentally in DIII-D is discussed. Simulations with a rigid-body-like rotation at a fixed velocity shows evidence of a screening of the RMPs. The extension of our results to realistic parameters is discussed.

Edge localized modes control by resonant magnetic perturbations

A number of designs for external or in-vessel coils generating Resonant Magnetic Perturbations (RMPs) for type I ELMs control in ITER are analyzed. The RMPs generated by the I-coils in the successful DIII-D ELMs control experiments are taken as a reference. The three ITER characteristic scenarios (H-mode, hybrid and steady-state) are studied. In a second part of the paper, the first results of a self-consistent non-linear MHD modelling of the plasma response to the RMPs with the JOREK code, for a DIII-D case, are presented.