China International Youth Conference on Electrical Engineering (CIYCEE 2020)

Magnetohydrodynamics (MHD) instabilities are widely observed in the tokamak plasma operation. The magnetic diagnostics provide important information for the understanding and control of MHD instabilities. This paper presents the current status of the magnetic diagnostics dedicated for measuring the MHD instabilities on the J-TEXT tokamak, which consist of five Mirnov probe arrays for measuring high frequency magnetic perturbations and two locked-mode saddle loop arrays for low-frequency magnetic perturbations. During the past 4 years, a series of upgrades have been carried out towards better spatial resolution on the measurement of MHD instabilities. Due to the installation of the high field side (HFS) divertor targets in early 2019, some of the probes were removed while an HFS Mirnov array has been designed and installed behind the targets. Owing to the preferable toroidal symmetry, the HFS Mirnov array provides valuable new information of the locked mode or quasi-static mode from the HFS for the first time in J-TEXT. By including the HFS information, the 2/1 resonant magnetic perturbation (RMP) induced locked mode was measured to have a poloidal mode number m of ~2.