Recent research work on the J-TEXT tokamak

Abstract

An overview of the recent research work on the J-TEXT tokamak over the last two years is presented. A series of experiments and simulations of the interaction between resonant magnetic perturbations (RMPs) and plasma were carried out on the J-TEXT tokamak. The results show that the m/n = 2/1 (m and n are the poloidal and toroidal mode numbers, respectively) mode locking is obtained with sufficiently large RMPs. And suppression of the m/n = 2/1 tearing mode by moderate magnetic perturbation amplitude is also observed. With experimental parameters as input, both mode locking and mode suppression by RMPs are simulated by nonlinear numerical modelling based on reduced magnetohydrodynamic equations. The simulations are in good agreement with the experimental observations. Density modulation using gas puffing is carried out on J-TEXT to evaluate the particle transport parameters in a typical J-TEXT discharge, including diffusion coefficient and convective velocity. Inverse sawtooth-like activity caused by neon gas injection is observed. The inverse sawtooth-like activity occurs only when the amount of neon impurity exceeds a threshold. Nevertheless, other impurities such as helium and argon cannot trigger such events. With the aid of a soft x-ray detector array, the runaway electron beam following disruptions is visible directly. A high-resolution far infrared polarimeter/interferometer, based on a three-wave technique, was developed and it observes the perturbations associated with sawtooth and tearing mode activities; the first result of the current density profile reconstruction is provided. An x-ray imaging crystal spectrometer is designed to receive the Kα line of Ar XVII and its satellites. The electron temperature obtained from line ratios of the W line to its satellites is 750 eV, and the ion temperature deduced from the Doppler broadening of the W line is 330 eV.

Overview of the J-TEXT progress on RMP and disruption physics

“…By feeding AC currents to the DRMP coils with proper phases, a 2/1 RMP rotating at a few kilohertz, e.g. [1][2][3][4][5][6] kHz, can be produced with the amplitude around 0.5 Gauss/kA. The RMP could rotate in either electron or ions diamagnetic directions.…”

Single-shot calibration of soft x-ray mirrors using a sinusoidal transmission grating

“…The well established laser polarimetry method proposed by Dodel and Kunz, 5 and the laser cavity offset heterodyne method developed by Lehecka et al 6 are adopted to achieve high sensitivity and high time resolution. The system setup is illustrated in Fig.…”

Plans for the electron cyclotron heating system on J-TEXT

“…Also, ECRH is proved to be helpful for current profile control, MHD stability, transport study, etc [7]. To fulfill the requirements of heating power on J-TEXT tokamak,…”