Modeling 3D plasma boundary corrugation and tailoring toroidal torque profiles with resonant magnetic perturbation fields in ITER

Abstract

Plasma response to 3D resonant magnetic perturbations (RMPs), applied for the purpose of controlling type-I edge localized modes (ELMs) in ITER with the baseline ELM control coils, is computed using a toroidal, resistive, full magneto-hydrodynamic model. Considered are five representative ITER plasmas, designed for different phases of the ITER exploration. The plasma response, measured by the plasma boundary corrugation, is found to be similar for the two DT scenarios at full plasma current (15 MA) and full toroidal field (5.3 T) but different fusion gain factors (Q = 5 versus Q = 10), indicating similar ELM control performance with the same RMP coil current configuration. The other plasma scenarios, with proportionally scaled down plasma current and toroidal field, can have different plasma boundary corrugation. The key plasma parameter affecting the response is the plasma toroidal flow near the pedestal region, which significantly varies depending on the transport model assumption for the toroidal momentum. Lower pedestal flow leads to a stronger edge peeling response from the plasma and thus probably a better ELM control. The optimal coil configuration for controlling type-I ELMs is similar for all four ITER plasmas with similar safety factor but different current levels, but is significantly different for the case at half plasma current (7.5 MA) and full field (5.3 T). On the other hand, for the purpose of controlling the radial profile of the plasma toroidal rotation in ITER using 3D fields, the relative amplitude of the toroidal torque density, between the plasma core and edge region, is optimized. Generally, a strong coupling between the core and edge torques is observed, largely due to the middle row ELM control coils. The best decoupling scheme of the core-edge torque distribution thus de-emphasizes the role of the middle row coils. Optimal coil current configurations are found for the ITER 15 MA/5.3 T Q = 10 plasma, that synergistically maximize the plasma edge-peeling response (indication for good ELM control) and the toroidal torque near the plasma edge (good for RMP field penetration through pedestal).

Effect of non-axisymmetric perturbations on the ambipolar E r and neoclassical particle flux inside the ITER pedestal region

“…This excludes the effect of magnetic islands or peripheral ergodic regions, which are observed when RMP fields are applied for ELM control [10,11]. Since ergodic regions only occur in the very outer layers of the confined plasma, well away from the pedestal top, and a similar picture is expected for ITER when appropriate screening is included [12] we do not expect our limitation in the modelling of these layers to have a significant impact on the results presented in this paper. In this approximation, the non-axi-symmetric perturbations to the tokamak equilibria allow the apparition of different solutions for the ambipolar E r (roots).…”

“…Here, we will focus on the so called baseline scenario for inductive operation, which targets fusion gain Q ≈ 10 and I p = 15MA plasma current, with a toroidal field of B t = 5.3T. The Mach number for toroidal plasma rotation in ITER is modelled to be low despite the sizeable rotation frequency [12], since the plasma temperature is very high. Thus, toroidal rotation is not considered in our equilibrium nor neoclassical transport modelling.…”

“…Figure12. Collisionality ν * profiles for test particles in the pedestal region, labelled with the NRL Plasma Formulary[48] convention α\β.…”

LOCUST-GPU predictions of fast-ion transport and power loads due to ELM-control coils in ITER

“…The 3D magnetic fields created by the ITER ECC system used herein have been calculated previously [21,22]. The plasma response was calculated by MARS-F [23,24] using plasma parameters determined by ASTRA [25] under various assumptions of plasma Prandtl number (ratio of toroidal momentum to thermal diffusivity in the core) and ratio of toroidal momentum to thermal confinement times-(τ φ /τ E ).…”

Modeling plasma toroidal flow profile control via NTV torque with n = 2 3D fields in MAST-U

“…The 3D field produced by the EFCC is the most likely reason for causing the on-axis flow damping. The 3D coils located at the outboard mid-plane is known to produce field spectrum that facilitates the plasma core flow damping [33].…”