Study on neutron sensitivity of a composite neutron detector based on⁴He gas scintillator

[Background] A radiation field with a significant mixture of neutrons and gamma rays exhibits the following characteristics: a wide range of neutron energy, serious mixing of neutron and gamma ray, etc. Therefore, to measure the total neutron emission from such a source with relatively high precision, the detector must possess high neutron sensitivity, a flat energy response, and a strong n/γ discrimination capability. [Purpose] To this end, a neutron detector based on a combined⁴He gas scintillator is proposed, which has the advantages of a flat neutron energy response and high n/γ resolution. The neutron sensitivity of the detector is studied in this paper. [Methods] Using the Monte Carlo method, simulations were conducted to calculate the energy deposition of recoil protons and recoil helium nuclei generated by interactions of neutrons with polyethylene targets and⁴He nuclei in the gas, as well as the neutron sensitivity of the detector. [Results] The computational results indicate that the energy deposition curve for 1–15 MeV neutrons in the⁴He gas is remarkably flat, with the detector’s neutron sensitivity to 1–15 MeV neutrons reaching approximately 4.0×10⁻¹⁵ C·cm². Experimental calibration of the detector’s neutron sensitivity was performed using the K600 high-voltage multiplier at the China Institute of Atomic Energy. [Conclusions] The theoretical results of neutron sensitivity are in good agreement with the experimental results. The theoretical calculation model of the detector proposed in this paper correctly calculates the neutron sensitivity, and the detector's performance meets the expected targets.