Development of a wide-range and fast-response digitizing pulse signal acquisition and processing system for neutron flux monitoring on EAST

Abstract

The neutron count rate fluctuation reaches six orders of magnitude between the ohmic plasma scenario and high power of auxiliary heating on an experimental advanced superconducting tokamak (EAST). The measurement result of neutron flux monitoring (NFM) is a significant feedback parameter related to the acquisition of radiation protection-related information and rapid fluctuations in neutron emission induced by plasma magnetohydrodynamic activity. Therefore, a wide range and high time resolution are required for the NFM system on EAST. To satisfy these requirements, a digital pulse signal acquisition and processing system with a wide dynamic range and fast response time was developed. The present study was conducted using a field-programmable gate array (FPGA) and peripheral component interconnect extension for instrument express (PXIe) platform. The digital dual measurement modes, which are composed of the pulse-counting mode and AC coupled square integral’s Campbelling mode, were designed to expand the measurement range of the signal acquisition and processing system. The time resolution of the signal acquisition and processing system was improved from 10 to 1 ms owing to utilizing high-speed analog-to-digital converters (ADCs), a high-speed PXIe communication with a direct memory access (DMA) mode, and online data preprocessing technology of FPGA. The signal acquisition and processing system was tested experimentally in the EAST radiation field. The test results showed that the time resolution of NFM was improved to 1 ms, and the dynamic range of the neutron counts rate was expanded to more than 10^{6} counts per second. The Campbelling mode was calibrated using a multipoint average linear fitting method; subsequently, the fitting coefficient reached 0.9911. Therefore, the newly developed pulse signal acquisition and processing system ensures that the NFM system meets the requirements of high-parameter experiments conducted on EAST more effectively.