Design And Performance Study Of Portable Single-sphere Neutron Spectrometer

The neutron energy spectrum measurement in the near space radiation field is of great significance to the study of solar activity and cosmic rays.Meanwhile,it can used to assess the damage assessment of space neutron to spacecraft components and the radiation protection level of space crew.The space neutron radiation field,the near-space neutron radiation field and the high-altitude?below 20km?neutron radiation field are limited by the space and load power of the flight test platform?space station,spacecraft,aircraft,helium balloon and hot air balloon flight paltform?,so the traditional multi-sphere neutron spectrometer cannot meet the usage requirements,which has a large volume and high power consumption.At the same time,the radiation composition of the space neutron radiation field is complex,so the neutron measuring equipment should be equipped with a variety of particle discrimination capabilities.In this paper,a portable single-sphere neutron spectrometer system is designed for the measurement of neutron energy spectrum in the neutron radiation field near space.Portable single-sphere neutron spectrometer system is improved on the basis of multi-sphere neutron spectrometer.Multiple ⁶Li glass scintillator are distribution in the three axis of two vertical upward of a single polyethylene slows ball,the single-sphere is divided into multiple shells to achieve the measurement effect similar to that of the multi-sphere neutron spectrometer.A pair of ⁶Li and ⁷Li glass scintillator is arranged in the center of the sphere,which neutron discrimination by ⁶Li and ⁷Li double glass scintillator?compensation method.Silicon photomultiplier?SiPM?with small size,low power consumption and high gain is used as photoelectric conversion device of lithium glass scintillator.This work has completed the performance study of neutron detector of the single-sphere spectrometer,as well as the structure design and performance study of the single-sphere spectrometer.The performance of neutron detector was tested in the?source and neutron source radiation fields respectively,studied the influence of the lithium glass scintillator coupled SiPM of neutron detector on the neutron source energy spectrum;used the MCNP5to analyzed the response function?from thermal to 20 MeV?of single-sphere spectrometer based on lithium glass scintillator with different diameters;simulated the performance of single-sphere spectrometer with a diameter of 30cm;simulated the influence of the payload bay of the flight test platform mounted on a helium balloon on the neutron radiation field measured by the single-sphere spectrometer in near space;in the field of single energy neutron radiation,the energy response of the single-sphere spectrometer is calibrated,the simulated response was calibrated by the experimental response,and the energy spectrum of the ²⁴¹Am-Be neutron radiation field was measured.The results show,the method of lithium glass scintillator coupling SiPM is adopted to meet the design requirements of the single-sphere spectrometer,and the neutron energy spectrum measured by the neutron detector is beneficial to neutron discrimination by means of silicon rubber coupling lithium glass scintillator and SiPM;it was found that the single-sphere neutron spectrometer of 30cm diameter can obtain a neutron energy spectrum close to the incident neutron source by UMG?lower than 20MeV?;after modifying the response function of the single-sphere spectrometer in the payload,the reasonable and reliable results of spectrum resolution can be obtained;the response function of the single-sphere spectrometer obtained from the calibration experiment of single energy neutron radiation field is consistent with the law of simulated response;for the measurement of energy spectrum of neutron radiation field of ²⁴¹Am-Be source,a reasonable unfolded result is obtained by UMG with response function calibrated by experiment.