Design Of Small Radiation Dosimeter For Human Spaceflight

Space radiation environment will not only do harm to spacecraft in orbit,but also threaten the health or even life of astronauts.With the development Aerospace Science and technology,the number of manned space missions is increasing.And the real-time radiation dose detector provides an effective guarantee for the health of astronauts.In this paper,a new personal radiation dosimeter for astronauts is designed by using plastic scintillator,SIPM and FPGA.It has the advantages of being sensitive to a variety of radiation particles,small size,and is more stable and radiation resistant than semiconductor radiation detector.Simplify the area of peripheral circuit by using FPGA.First of all,adopt the scheme of probe size and reflector with good light collection efficiency to build the probe of the detector.The energy response of plastic scintillator to neutron andγis simulated by GEANT4 to determine the feasibility of the scheme.With the stability of the amplifier and filter circuit considered,design the amplifier unit and select components.The theoretical noise estimate of the pre-amplifier circuit is 2.89mv.In the test,the noise is less than 3m V,which is consistent with the theoretical estimate.Secondly,the hardware system of the dosimeter’s sampling module,data processing module and display module is mainly constructed by the SOPC system on FPGA,which is mainly composed of Avalon Data Bus,SDRAM Controller,PIO,EPCS Controller,AD Conversion Controller,LCD Controller,etc.The main algorithms used in the program are Coincidence Measurement,Double-end Energy Combination,etc.Thirdly,the transmission system of radiation dosimeter is designed,which transmits radiation detection data to network through Gigabit Ethernet,and the effective data transmission rate reaches800Mbit/s.The ADC with 25 MSPS is used with double-end sampling,and the FIFO buffer is used to realize the matching of different data width and clock frequency.Finally,²²Na source was used for debugging and experimental test.The test of pulse waveform is normal.The energy spectrum response range of the detector are estimated by simulation and experiment.Energy spectrum response range of the detector forγis 12.78Me V to 0.192Me V.The Energy spectrum response range of neutron is 1.52Me V to 19.63Me V by using nonlinear calibration.After experimental test with single source and double sources,the radiation dose,particle numbers and ²²Na energy spectrum are obtained.