Research on dual-mode cross-calibration method for neutron flux monitoring systems in fission chambers

Abstract The neutron flux monitoring (NFM) system of the fission chamber in the Experimental Advanced Superconducting Tokamak (EAST) operates in a dual-mode configuration that combines pulse counting and Campbell modes, enabling wide-range measurements across eight orders of magnitude. The accuracy of cross-calibration between these two modes is of paramount importance. Conventional calibration studies typically employ simulated signals based on idealized Gaussian amplitude distribution (GD) models, which deviate from the asymmetric response characteristics of practical detectors. To address this limitation, a parametric neutron signal generation system was developed in this study. By integrating a programmable signal source capable of outputting GD and experimentally amplitude distribution (EAD) pulse signals, the system enables a comprehensive evaluation of their respective impacts on dual-mode cross-calibration intervals and error margins. The results show that the effective calibration interval for the GD source extends from 5 × 10 4 to 5 × 10 5 cps, while that for the EAD source shifts to 2 × 10 4 to 4 × 10 5 cps. Compared with the conventional GD-based calibration approach, the EAD method reduces the cross-calibration error in converting the mean square voltage integral of neutron pulse signals collected in Campbell mode into pulse count rate by 1.07%, representing a relative reduction of 15.59%. These findings demonstrate that the EAD calibration method significantly enhances the accuracy of dual-mode calibration in the fission chamber.