A dual-chopper adjustable-pulse isotopic neutron source to support the development of in-situ planetary exploration payloads

Elemental analysis is crucial for determining planetary composition in deep space exploration. Prompt Gamma Neutron Activation Analysis (PGNAA) enables in-situ qualitative and quantitative measurement of surface elements, suitable for complex space environments. Existing controllable neutron sources are too large and heavy for integration into deep space platforms, while conventional isotopic neutron sources, though compact and stable, lack emission control and pulse adjustment. This study proposes a lightweight, controllable isotopic pulsed neutron source using an 241 AmO 2 -Be layered structure and a dual-disk chopper system to achieve neutron emission switching and adjustable pulse width by varying chopper speed and aperture overlap. Geant4 simulations were used to optimize structural parameters, determining an 241 AmO 2 thickness of 5 μ m, Be layer thickness of 300 μ m, total length of 15 mm, 241 AmO 2 radius of 4 cm, chopper aperture area of 8 π cm 2 , chopper spacing of 1 mm, thickness of 0.1 mm, and 5 mm distance between the chopper and 241 AmO 2 layer. Simulation results show a neutron yield of 2.44 × 10 −5 n/ α with stable and controllable neutron output, offering key technical support for in-situ planetary elemental analysis in deep space missions.