Prototype design of satellite payload for neutron spectrum acquisition

In recent years, there have been fewer missions to detect neutrons in low Earth orbits (LEO), and the data obtained have been extremely limited. Studying the distribution of the neutron energy spectrum in LEO satellites through detection can help solve three major seientifie problems: the source of particles in the inner radiation belt, information on solar-accelerated particles, and the proportion of neutrons from dilferent sources in near-Earth space. The detection eficiency and accuracy of neutrons are affected by charged and primary particles in the environment and secondary neutrons produced by the spacecraft itself, which has been a hot research topic. The neutron spectrometer developed in this study adopts two combinations of 15 silicon detectors interms of detector type and arrangement, which are used for neutron detection via the nuclear reaction method and recoil proton method, respectively, in which a 27-μm-thick 6Lif conversion layer is used for thermal neutron detection up to 0.4 eV and a 300-μm-thick high-density polyethylene conversion layer is used for fast neutron detection up to 14 MeV and below. The design of the detector set can also remove the influence of primary charged particles and secondary neutrons in the detectionenvironment to a certain extent, thereby improving the accuracy of neutron detection. In this study, the neutron spectrometer hardware, firmware, software design, and basic performance of the front-end readout chip SKlROC2A were tested. The readout circuit of each channel baseline ADC code was less than 17; thus, the channel consistency was good. The RMS noise of the channel baseline was only 7.1 mV and exhibited good stability. The maximum number of events that could be processed per second is 75. The overall power consumption was 3 W, the weight was 792 g, and the volume was less than 1 dm3. Furthermore, the neutron spectrometer was tested for principle and detection efficiency using various neutron sources, such as 241Am-Be neutron source, 2.5 MeV neutron beam current, and 14 MeV neutron beam current, and the experiments were analyzed with corresponding simulations, The experimental data and simulation results were in good agreement and met the design requirements, The intrinsic detection efficiency of the probes used in the neutron spectrometer was 1.05% for 14 MeV fast neutrons.