The neutron energy spectrum and fluence of the atmospheric neutron irradiation spectrometer at China Spallation Neutron Source cover the energy range from meV to GeV. The evaluation of the neutron energy spectrum and fluence in an energy region above 1 MeV is of great significance for studying single event effect of atmospheric neutrons. Due to the limitations of the proton beam time structure of the CSNS and the engineering reality of the ANIS, it is impossible to achieve the neutron energy spectrum and fluence above 1 MeV through absolute measurements. Therefore, it is necessary to adopt a combination of theoretical simulations and partial experiments to provide reference values. This work covers the following aspects. 1) Based on the measured neutron energy spectrum data from the ICE beamline at LANSCE WNR, the physical models, tally types, and cross-section data files suitable for the calculation of high energy neutron energy spectra and fluence are explored using MCNPX2.5.0; 2) A secondary source with energy distribution, angular distribution, and spatial distribution for neutron energy spectrum and fluence evaluation is developed and verified. 3) Using the obtained neutron energy spectrum and fluence and the combination of existing facilities and JSED89A reference neutron energy spectrum, the performance of the ANIS facility is evaluated from the perspectives of spectrum shape and radiation effect. 4) An experiment on neutron induced single-event upset cross-section measurement of configuration memory on Xilinx 2nd generation FPGAs is conducted using the ANIS. The results are consistent with test results of the same chip series on similar international facilities.

In summary, it can be concluded that the ANIS at CSNS may be the facility with the neutron energy spectrum closest to the natural atmospheric neutron energy spectrum among similar facilities in the world, and it has also been confirmed that the test results of ANIS from CSNS show excellent consistency with results obtained from other facilities. Therefore, the research results on atmospheric neutron single-particle effects and engineering acceleration tests based on ANIS at CSNS can be directly applied to high-reliability fields such as aviation, aerospace, military, and civil, contributing to the development of new quality productive forces.