Research And Development Of Single Sphere Neutron Spectrometer

Neutron is an important part of space radiation.The neutron energy spectrum measurement in space radiation was significant for the study of space radiation environment and ensuring long-term safety of astronauts and the spacecrafts.Due to the high-energy charged particles and gamma ray in cosmic ray,the conventional neutron detectors such as³He proportional counters can't discriminate neutron events from charged particles in mixed radiation field.Moreover,because the room in the spacecraft is limited,the neutron spectrometer should be compact and easily operational.The neutron energy spectrometer used in spacecraft was developed based on the research of neutron spectrometer.The single sphere neutron spectrometer?SSNS?utilizes the single moderating sphere with mulit-pairs of ⁶Li-and ⁷Li-glass scintillator detectors to measure the neutron energy spectrum just like Bonner sphere spectrometer.This spectrometer can discriminate neutron events in mixed radiation field including neutron,gamma and charged particles baesd on the response's difference between ⁶Li and ⁷Li glass scintillator.The neutron energy response and the angular response of spectrometer were studied by Monte Carlo simulation using MCNP code.According to the simulation results,the structure of SSNS and the parameters of related materials were determined.The high voltage power supply circuit for each detector and the signal readout system based on charge division were designed.The SSNS was calibrated in the monoenergetic neutron reference radiation fields at Radiation Metrology Department of China Institute of Atomic Energy,and was used to measure neutron energy spectrum in the ²⁴¹Am-Be field.The measurement result was converted to ambient dose equivalent rate by fluence-dose conversion coefficients in ICRP publication 74.The dose equivalent rate values were deviated from the reference values by a maximum of 2.6%.The experimental results showed that the SSNS can be a radiation protection monitor.