Non-linear magnetohydrodynamic modeling of plasma response to resonant magnetic perturbations

Abstract

The interaction of static Resonant Magnetic Perturbations (RMPs) with the plasma flows is modeled in toroidal geometry, using the non-linear resistive MHD code JOREK, which includes the X-point and the Scrape-Off-Layer. Two-fluid diamagnetic effects, the neoclassical poloidal friction and a source of toroidal rotation are introduced in the model to describe realistic plasma flows. RMP penetration is studied taking self-consistently into account the effects of these flows and the radial electric field evolution. JET-like, MAST and ITER parameters are used in modeling. For JET-like parameters, three regimes of plasma response are found depending on the plasma resistivity and the diamagnetic rotation: at high resistivity and slow rotation, the islands generated by the RMPs at the edge resonant surfaces rotate in the ion diamagnetic direction and their size oscillates. At faster rotation, the generated islands are static and are more screened by the plasma. An intermediate regime with static islands which slightly oscillate is found at lower resistivity. In ITER simulations, the RMPs generate static islands, which forms an ergodic layer at the very edge (ψ ≥ 0.96) characterized by lobe structures near the X-point and results in a small strike point splitting on the divertor targets. In MAST DND geometry, lobes are also found near the X-point and the 3D-deformation of the density and temperature profiles is observed.

Mechanism of Edge Localized Mode Mitigation by Resonant Magnetic Perturbations

“…The JOREK model used here includes two-fluid diamagnetic effects important in the pedestal region and is described in details in [18]. The realistic JET pulse #77329 parameters used as in [17,18,19] 7 , which for numerical reasons is lower compared to the experimental value (S=10 9 ). In the typical JOREK run initially the equilibrium with flows is obtained for the toroidal harmonic n=0 (axisymmetric component) on a time scale of ~1ms [18].…”

“…The realistic JET pulse #77329 parameters used as in [17,18,19] 7 , which for numerical reasons is lower compared to the experimental value (S=10 9 ). In the typical JOREK run initially the equilibrium with flows is obtained for the toroidal harmonic n=0 (axisymmetric component) on a time scale of ~1ms [18]. After that, for ELMs modelling, other harmonics are initialized in plasma at "noise" level (~10 -25 ).…”

“…Recently the application of Resonant Magnetic Perturbations (RMPs) demonstrated the possibility of total ELMs suppression or strong mitigation of their size [3][4][5][6][7][8][9], motivating the use of this method in ITER [1]. In the last decade, the non-linear MHD theory and modeling have made a significant progress to refine the understanding of ELM [10][11][12][13][14] and RMP [15][16][17][18][19][20] physics. However the understanding of RMP interaction with ELMs is still missing and was not modeled so far, motivating work we are presenting here.…”

“…After that, for ELMs modelling, other harmonics are initialized in plasma at "noise" level (~10 -25 ). In the case of RMPs vacuum amplitude for corresponding harmonic (here n=2 from EFCC [6,17,19]) is set at the boundary and increased in time until the stationary conditions are reached [18], resulting in a 3D equilibrium, then other harmonics were initialized to study interaction of ELMs with RMPs. 2.…”

“…The results we found in modelling correspond to generic features observed in high collisionality RMP experiments. The JOREK model used here includes two-fluid diamagnetic effects important in the pedestal region and is described in details in [18]. The realistic JET pulse #77329 parameters used as in [17,18,19]: R 0 =2.9m, a=0.89m, B tor =1.8T, q 95 =3.8.…”