Non-linear MHD modelling of edge localized modes suppression by resonant magnetic perturbations in ITER

Abstract

Edge Localized Modes (ELMs) suppression by Resonant Magnetic Perturbations (RMPs) was studied with the non-linear MHD code JOREK for the ITER H-mode scenarios at 15MA,12.5MA,10MA/5.3T. The main aim of this work was to demonstrate that ELMs can be suppressed by RMPs while the divertor 3D footprints of heat and particle fluxes remain within divertor material limits. The unstable peeling-ballooning modes responsible for ELMs without RMPs were modelled first for each scenario using numerically accessible parameters for ITER. Then the stabilization of ELMs by RMPs was modelled with the same parameters. RMP spectra, optimized by the linear MHD MARS-F code, with main toroidal harmonics N=2, N=3, N=4 have been used as boundary conditions of the computational domain of JOREK, including realistic RMP coils, main plasma, Scrape Off Layer (SOL) divertor and realistic first wall. The model includes all relevant plasma flows: toroidal rotation, two fluid diamagnetic effects and neoclassical poloidal friction. With RMPs, the main toroidal harmonic and the non-linearly coupled harmonics remain dominant at the plasma edge, producing saturated modes and a continuous MHD turbulent transport thereby avoiding ELM crashes in all scenarios considered here. The threshold for ELM suppression was found at a maximum RMP coils current of 45kAt-60kAt compared to the coils maximum capability of 90kAt. In the high beta poloidal steady-state 10MA/5.3T scenario, a rotating QH-mode without ELMs was observed even without RMPs. In this scenario with RMPs N=3, N=4 at 20kAt maximum current in RMP coils, similar QH-mode behavior was observed however with dominant edge harmonic corresponding to the main toroidal number of RMPs. The 3D footprints with RMPs show the characteristic splitting with the main RMP toroidal symmetry. The maximum radial extension of the footprints typically was ~20 cm in inner divertor and ~40 cm in outer divertor with stationary heat fluxes decreasing further out from the initial strike point from ~5MW/m2 to ~1MW/m2 assuming a total power in the divertor and walls is 50MW.

Numerical investigation of toroidal plasma response for ELM control via magnetic perturbations in the DTT Tokamak

“…As a final remark, we note that a full picture of RMP-plasma interaction and first-principle prediction of coil current for ELM control can only be achieved with non-linear MHD modeling. An example of this is reported in [9] where the JOREK code is applied to ITER. This is at the moment beyond the scope of the study presented here and can be the subject of future work.…”

“…Suppression instead requires that the pedestal pressure is kept below a given threshold for peelingballooning modes. This is achieved with transport and many channels are possible, such as magnetic islands in the pedestal region [7,8] or MHD perturbations with non-linear mode coupling [9]. Edge-peeling plasma response is a criterion that can be applied for both applications, since it correlates with plasma displacement in the pedestal region (thus with ballooning instabilities and mitigation) but also with the size of magnetic islands near the edge [10].…”

Effect of resonant magnetic perturbations including toroidal sidebands on magnetic footprints and fast ion losses in HL-2M

“…The RMP coil efficiency depends on both the amplitude and spectrum of field perturbations, which are mainly determined by the plasma equilibrium parameters and by the RMP coil configuration [12][13][14][15][16][17][18][19][20][21][22]. The RMP technique will be applied to control ELMs in the International Thermonuclear Experimental Reactor (ITER) [23]. For a given equilibrium with fixed RMP coil geometry parameters, a significant aspect to consider when optimizing the RMP field spectrum is the toroidal phasing of the RMP coil current.…”

Toroidal modeling of plasma flow damping and density pump-out by RMP during ELM mitigation in HL-2A

“…Resonant magnetic perturbation (RMP) coils have been installed in many present-day magnetic confinement fusion devices, for the main purpose of actively controlling the edge localized mode (ELM) in H-mode plasmas [1][2][3][4][5][6][7]. This technique is also planned to be applied in ITER [8][9][10][11]. On the other hand, the toroidal asymmetry produced by three dimensional (3D) RMP fields can cause substantial side effects on the plasma transport, such as reductions of the plasma density and/or the toroidal flow speed, which in turn impacts the plasma energy confinement and stability [12,13].…”