Integrated simulation of HL-3 reversed magnetic shear configuration achieved by ion cyclotron wave and electron cyclotron wave combined injection

Abstract

The reversed magnetic shear configuration with internal transport barriers (ITBs), high specific pressure, and high bootstrap current is an important means to achieve high parameter operation in tokamaks. In this paper, based on the METIS integrated simulation platform, combined with the parameters of the HL-3 device, the joint injection of ion cyclotron wave (ICW) and electron cyclotron wave (ECW) to achieve the reversed magnetic shear configuration is investigated. By analyzing the effects of the ICW injection time, the ECW injection time, and the direction of the electron cyclotron current drive (ECCD) on the confinement, the reversed magnetic shear scenario of the high parameter is obtained, with the bootstrap current up to 45%, and the β_N up to 3.2. The results show that the injection of ICW at the start-up stage can increase the plasma temperature and the magnetic diffusion time, which is conducive to maintaining the reversed magnetic shear configuration; when the off-axis ECW are injected timely in the magnetic diffusion stage, a strong drive current can be generated, so that the internal transport barrier, the high bootstrap current, and the reversed magnetic shear promote each other, maintain the reversed magnetic shear, and achieve the high confinement operation; when the ICW injection is delayed, the on-axis counter-ECCD can also form a good reversed magnetic shear. The results provide a reference for future reversed magnetic shear experiments in HL-3 to improve the discharge performance.