RESUMEN
With the rapid development of space exploration, the detection of space neutron radiation is becoming increasingly important. The currently widely used Bonner sphere spectrometer have drawbacks such as large size and weight, as well as low fault tolerance, when detecting space neutron spectra. This paper describes in detail a new type of space neutron spectrometer (SNS), which has two different specifications to adapt to the directional and non-directional neutron field environment, and can measure the directional neutron energy spectrum. For the directed neutron field, SNS integrates 12 3He thermal neutron counters (diameter 3 cm: 3, diameter 4 cm: 6, diameter 5 cm: 3) and uses cylindrical polyethylene as a moderator. For non-directed neutron fields, SNS integrates 9 3He thermal neutron counters (diameter 3 cm: 4, diameter 4 cm: 3, diameter 5 cm: 2) located in a single structure made of polyethylene, boron-containing polyethylene and gadolinium. The device is capable of providing a strong directional response in the energy range of thermal neutrons up to 20 MeV, with little sensitivity to neutrons coming from directions other than the axis of the cylinder. The Monte Carlo transport code FLUKA was used to determine the final configuration of the instrument, including the arrangement, number, and position of thermal neutron counters. In addition, the response matrix of the instrument was calculated using FLUKA code. This device can replace traditional Bonner sphere spectrometer for measuring space neutrons, and it also provides reference value for downsized and lightweight neutron spectrometers on the ground.
RESUMEN
The currently widely used multi-sphere neutron spectrometers still have many drawbacks, including complex design and processing, the need for multiple moderating spheres, high costs, large volumes, and complicated measurement procedures. This work proposes the portable cylindrical water injection multilayer neutron spectrometer (CWNS) as a promising alternative based on water pumping injection. The structure of CWNS consists of a central thermal neutron detector and a surrounding 6-layer of coaxial cylindrical water bags with varying diameters. During non-measurement periods, this CWNS is convenient to carry due to the absence of the need to inject moderating water. To optimize the CWNS design, we employed FLUKA simulation software to study and refine various parameters, including the thickness of the water bag, the material composition of the water bag, and the parameters of the supporting column. We finally achieved an optimized design. Specifically, the water bag of the CWNS is constructed using a 0.3 mm thick polyethylene film. The supporting column for the water bag is made of aluminum, providing stability and support to the overall structure. These optimized design parameters determine the specific size and configuration of the CWNS. The CWNS offers the benefits of convenient carrying, simplified processing, cost-effectiveness, and straightforward measurement. It has a promising potential use for the directional neutron dose monitoring.