Control system of neoclassical tearing modes in real time on HL-2A tokamak

Abstract

The stability and performance of tokamak plasmas are routinely limited by various magneto-hydrodynamic instabilities, such as neoclassical tearing modes (NTMs). This paper presents a rather simple method to control the NTMs in real time (RT) on a tokamak, including the control principle of a feedback approach for RT suppression and stabilization for the NTMs. The control system combines Mirnov, electron cyclotron emission, and soft X-ray diagnostics used for determining the NTM positions. A methodology for fast detection of 2/1 or 3/2 NTM positions with 129 × 129 grid reconstruction is elucidated. The forty poloidal angles for steering the electron cyclotron resonance heating (ECRH)/electron cyclotron current drive launcher are used to establish the alignment of antenna mirrors with the center of the NTM and to ensure launcher emission intersecting with the rational surface of a magnetic island. Pilot experiments demonstrate the RT control capability to trace the conventional tearing modes (CTMs) in the HL-2A tokamak. The 2/1 CTMs have been suppressed or stabilized by the ECRH power deposition on site or with the steerable launcher.

27th IAEA Fusion Energy Conference: summary of sessions EX/C, EX/S and PPC

“…Teams from several devices also presented results from their implementation of real-time control of NTMs, e.g. TCV [90], HL-2A [145] and J-TEXT [146], and these activities will be discussed in section 4.5.…”

Summary of the fundamental plasma physics session in the first AAPPS-DPP conference

“…Song reported the results on the real-time control of neoclassical tearing mode(NTM) by the Electron Cyclotron Current Drive(ECCD) technique on the HL-2A device 42 . The instabilities are successfully suppressed by the ECCD system ( Fig.…”

Progress of microwave diagnostics development on the HL-2A tokamak

“…The features of electron heat transport in H-mode pedestal and long-range correlation of turbulence during nonlocal transport have been studied for the first time by using the new ECE system [8,[40][41][42][43]. Due to its high spatial resolution and local measurement, the locations of the MHD modes such as fishbone, tearing mode, and neoclassical tearing mode (NTM), and the turbulence transport inside the magnetic island, have been observed [27,44,45].…”