Research of SiC Neutron Detectors Based on Boron Carbide Conversion Materials

In order to ensure the long-term, stable and safe operation of compact all-solid-state reactors, real-time monitoring of neutron fluxes within the reactor is essential. Neutron flux not only reflects the nuclear activity of the reactor, but is also directly related to the safety and efficiency of the reactor. Among the existing neutron detector technologies, there are some limitations in the application of 3He proportional counting tubes, fission gas ionization chambers, and traditional Si and Ge semiconductor detectors in high-temperature and strong radiation environments, such as the noise of gas detectors will increase significantly in high-temperature environments, which affects the detection accuracy. Although the traditional Si and Ge semiconductor detectors have good energy resolution in low temperature environments, the leakage current becomes larger in high temperature and strong irradiation environments, and the introduced noise will increase significantly, thus limiting their application in extreme environments. As a wide band-gap semiconductor material, SiC detector has the characteristics of large band gap, strong radiation resistance, high breakdown electric field strength and large saturated electron drift velocity, which makes it have excellent high temperature resistance and radiation resistance in extreme environments. The purpose of this study is to design a SiC neutron detector based on the 10B4C conversion layer and optimize its structural parameters to achieve high-precision real-time monitoring of neutron flux in the reactor. The energy spectrum of thermal neutrons in the sensitive volume of 10B4C coating with different thicknesses was simulated by Geant4 simulation software, and the relationship between the energy spectrum of γ rays of different energies in the sensitive volume of SiC and the variation of thermal neutron detection efficiency with the thickness of 10B4C coating under different thresholds were analyzed to determine the optimal thickness values of SiC epitaxial layer and 10B4C conversion layer. Combined with the dismantling of the conversion layer, the SiC detector was used to detect γ rays and thermal neutrons using 60Co, 137Cs, 22Na radioactive sources and neutron sources. By comparing the energy deposition of SiC for thermal neutron detection at different layer thicknesses, the accuracy of the simulation results was verified and experimental basis for subsequent applications was provided. The simulation and experimental results show that the optimal thickness of the conversion layer is 2 μm, 300 keV can be used as the screening γ ray threshold, the air gap has great influence on the energy deposition of nuclear reaction products, and the energy resolution of SiC can reach 2.08% when working at low pressure of 20 V. The overall results verify the feasibility of the design parameters of the SiC neutron detector, and realize the detection of neutron energy spectrum and flux.