Neutron Fluence Measurement and Analysis of Scattered Neutrons Influence in Accelerator Neutron Sources Based on Gold Activation Method

Using the gold activation method and offline gamma-ray spectroscopy technique, the neutron fluence produced by the reactions \mathrmT\left(\mathrmp,\mathrmn\right)^3\mathrmH\mathrme and \mathrmT\left(\mathrmd,\mathrmn\right)^4\mathrmH\mathrme on the 3 MV tandem accelerator at Sichuan University was measured, with a minimum measurement error of 3.041%. The factors affecting neutron fluence measurements, such as multiple scattering effects and self-shielding effects, were simulated and corrected using the MCNP5 program. Detailed analysis was conducted on the correlation between experimental conditions such as target material, thickness of the cooling water layer, sample position, and multiple scattering effects. The research results indicate that the correction due to multiple scattering effects can reach up to 30%. Multiple scattering effects of neutrons on the target material and cooling water layer can affect the monochromaticity of neutron energy at the location of the activation foil, which can significantly interfere with the determination of standard reaction cross-sections, thus impacting the results of neutron fluence measurement. Therefore, in experiments, it is advisable to minimize the use of target material and the thickness of the cooling water layer as much as possible, and to prioritize irradiation at the 0° position.