Resonant magnetic perturbations of edge-plasmas in toroidal confinement devices

Abstract

The image shown in figure 15 on page 18 was inadvertently replaced by the same image shown in figure 16 during the production process of the paper by the typesetters. A corrected version of figure 15, including the original (as published) figure caption is provided below. This change in figure 15 does not affect the scientific results presented in the paper.

Validation metrics for turbulent plasma transport

“…For instance, the H 89 and H 98ðy;2Þ measures are the ratios of the energy confinement time in a given plasma to the empirical ITER89P 16 or IPB98(y,2) 20 scaling laws for s E which have been extensively used in the design of ITER target scenarios. 26 Each of these measures provides a basis for assessing the level of confinement achieved in a given experiment relative to what is required for a given ITER operational scenario, and a significant fraction of current experimental work is focused on demonstrating plasmas which can maintain these normalized confinement levels in different operational scenarios (such as non-inductive steady-state operation, 27 edge localized mode (ELM) 28 suppression via application of resonant magnetic perturbations, 29 or operation in the presence of "ITER-like" metal walls 30 ).…”

“…The primary drawback is that the idealized physical situation this ordering describes-the slow evolution of equilibrium profiles on perfectly nested axisymmetric flux surfaces due only to neoclassical and small-amplitude fluctuations-is in practice almost never realized experimentally. For example, large-amplitude fluctuations near the LCFS, non-axisymmetric equilibria arising from both internal (e.g., sawteeth 47 and tearing modes 48 ) and external (e.g., error fields 49 and resonant magnetic perturbations 29 ) processes, 50 and rapidly varying external heating sources operated in feedback to maintain plasma performance 51 all lead to violations of the formal ordering outlined above in different regions of the plasma. However, in many cases, these violations are weak, or localized to certain regions of the plasma, and the underlying physical picture embodied in this model is believed to represent a useful practical paradigm for understanding and predicting plasma confinement.…”

Impact of three-dimensional magnetic perturbations on turbulence in tokamak edge plasmas

“…These MPs are called resonant when they resonate with the field on a given magnetic flux surface, usually located in the plasma edge region. The efficiency of these MPs at controlling ELMs depends on different conditions (see [7]) and the 3D full understanding of the complex interaction between RMP and the plasma remains a challenging task. Several experimental studies have underlined 3D changes on the heat flux and particle distribution at the egde plasma, for different tokamaks [8][9][10].…”

Helical plasma-wall interaction in the RFX-mod: effects of high-n mode locking

“…The edge of magnetically confined plasmas in toroidal configurations can be characterized by the presence of magnetic perturbations (MPs) with helicity m/n, with m and n the poloidal and toroidal mode numbers respectively. These MPs appear spontaneously in the Reversed Field Pinch (RFP) [1] but can also be produced on purpose in Tokamaks [2] and Stellarators [3]. In the Reversed Field Pinch RFX-mod device (R=2m, a=0.46m), during high-current discharges (Ip>1MA, n/n G <0.3), an almost monochromatic magnetic spectrum spontaneously develops, with a (m/n)=(1/7) dominant mode rotating along the toroidal direction at a frequency of a few tens Hz; this is the so-called quasi-single helicity (QSH) plasma (which is characterized by higher energy confinement time than the chaotic multiply helicity (MH) state).…”