Development of a real time magnetic island identification system for HL-2A tokamak

Abstract

A novel real time magnetic island identification system for HL-2A is introduced. The identification method is based on the measurement of Mirnov probes and the equilibrium flux constructed by the equilibrium fit (EFIT) code. The system consists of an analog front board and a digital processing board connected by a shield cable. Four octal-channel analog-to-digital convertors are utilized for 100 KHz simultaneous sampling of all the probes, and the applications of PCI extensions for Instrumentation platform and reflective memory allow the system to receive EFIT results simultaneously. A high performance field programmable gate array (FPGA) is used to realize the real time identification algorithm. Based on the parallel and pipeline processing of the FPGA, the magnetic island structure can be identified with a cycle time of 3 ms during experiments.

Development of a real-time magnetic island reconstruction system based on PCIe platform for HL-2A tokamak

“…In formula (8), the parameter T is only related to the current filament coordinate and the grid point position, and can be calculated in advance by host computer and sent to FPGA to form a parameter table. When the perturbation flux is to be calculated, the parameter T can be read from the parameter table according to the current filament position.…”

“…At present, the common methods to identify the magnetic island structure include soft x-ray tomography and electron cyclotron radiation [3][4][5][6]. In the HL-2A tokamak device, the MHD instabilities, especially the tearing modes, are investigated by Mirnov probes, and the magnetic island reconstruction (MIR) method on the basis of Mirnov signals and the equilibrium fit (EFIT) code has been developed gradually in recent years [7][8][9]. In this method, the mode number of the tearing mode can be firstly obtained by analyzing the Mirnov signals, and the real perturbation field is simulated by the magnetic field induced by the perturbation current distributed on the rational surface.…”

A novel magnetic island structure identification system based on Mirnov probes and DDR3 look-up table for HL-2A tokamak

“…The identification method above was realized as an offline analysis program and furtherly applied in a system of 65 × 65 EFIT grid covering a poloidal cross section of 1.3 m ×1.75 m on the HL-2A device, proving its validity [11,12]. In order to further improve the accuracy of the magnetic island structure, the number of EFIT grid increases to 129 × 129, which can also make the control of ECRH injection more precise.…”