The Design And Development Of A Portable Water-injection Neutron Spectrometer

The fields in which neutron physics plays a vital role like basic research,nuclear energy exploitation,defense construction and technological applications,and where the measurement of neutron energy spectrum is critical.However,existing devices suffer from many issues such as low accuracy,high cost and large size.In this work,we developed a prototype of a portable water-injected neutron spectrometer which based on BF₃ counting tubes and a multi-layered water-injection moderating columnar structure The main research contents are as follows:The First part is the detector design and entity processing.simulating the effect factors in a multi-layered structure for neutron energy response such as air,moderating material and thickness of the detector with MCNP,proposing a scheme of a seven-layer concentric column structure neutron spectrometer suitable for neutron detection in the0～10 Me V energy region.A set of prototypes was fabricated based on the optimized parameters and re-modeled on the basis of the material and geometric parameters of the physical prototype for verification.The results show that the principle prototype meets the expected design objectives.The second part is the signal processing system design.Key features of the signal to be processed were extracted using Python and a matching signal processing circuit was designed.This includes a pre-amplification circuit,an amplification and filtering circuit,a comparison circuit and a triggering circuit.The Multisim simulation results show that small currents of n A levels can be shaped into standard TTL signals after passing through the signal processing circuit.Based on the simulation,the PCB board was drawn using Altium Designer software,and the debugging and testing of the physical circuit board were completed.The results show that the signal shaping effect is perfect.The third part is the data acquisition system design.The counting and acquisition firmware was designed using FPGA development board written in Verilog language.It includes test signal module,counting module,data transmission module and digital tube display module.For the hardware part,the acquisition software for real-time monitoring and data storage was designed using Python.The results show that the pulse counting function is good.The last part is the whole machine test and energy spectrum acquisition.Experimental measurements were carried out using an Am-Be neutron source on the prototype for background acquisition and efficiency scaling.The experimental data was used with UMG software to analyze the neutron radiation field and the obtained neutron spectrum was agreement with the expected spectrum.The results show that the principle prototype of the portable water-injected neutron spectrometer achieves the expected design goals and can be used for neutron detection in the 0～10 MeV energy range.