Design of the data acquisition system of acceleration grid power supply for CFETR N-NBI prototype

Abstract

The Acceleration Grid Power Supply (AGPS) of the China Fusion Engineering Test Reactor (CFETR) negative-ion-based neutral beam injector (N-NBI) prototype is a high-voltage power supply rated at -200 kV/25 A. The output voltage measurement and state detection of AGPS are required to safely operate for the N-NBI system. Hence, a high-performance data acquisition system is essential. The performance requirements of the data acquisition system becomes remarkable when the output voltage increases and electromagnetic interference enhance. This paper proposes an effective data acquisition method based on field programmable gate array (FPGA) technology and PCI extensions for instrumentation (PXI) series hardware used in the existing control system. Compared with traditional voltage-to-frequency (VF) conversion methods, the frequency output by the proposed method can maintain a consistently high standard when a lower reference output voltage is required. The principle test and high voltage test on the pulse step modulation (PSM) power supply of the J-TEXT Tokamak indicate that the delay of the data acquisition system is no more than 20 μs, which fulfills the requirements.