Effects of edge-localized mode-induced neoclassical toroidal viscosity torque on the toroidal intrinsic rotation in the EAST tokamak

Abstract

Intrinsic rotation has been observed in lower hybrid current-driven (LHCD) H-mode plasmas with type-III edge-localized modes (ELMs) on Experimental Advanced Superconducting Tokamak (EAST), and it is found that the edge toroidal rotation accelerated before the onset of the ELM burst. Magnetic perturbation analysis shows there is a perturbation amplitude growth below 30 kHz corresponding to the edge rotation acceleration. Using the filament model, the neoclassical toroidal viscosity (NTV) code shows there is a co-current NTV torque at the edge, which may be responsible for the edge rotation acceleration. For maximum displacement ∼1 cm and toroidal mode number n=15, the calculated torque density is ∼0.44 N/m2, comparable with the average edge toroidal angular momentum change rate ∼1.24 N/m2. Here, the 1 cm maximum magnetic surface displacement estimated from the experimental observation corresponds to a maximum magnetic perturbation ∼ 10−3–10−2 T, in accordance with magnetic perturbation measurements during ELMs. By varying n from 10 to 20, the magnitude of the edge NTV torque density is mainly ∼0.1–1 N/m2. This significant co-current torque indicates that the NTV theory may be important in rotation problems during ELMs in H-mode plasmas. To better illuminate the problem, magnetic surface deformation obtained from other codes is desired for a more accurate calculation.