| Space radiation is one of the most important risk factors for space exploration and manned space flight.Space particle detection is vital important to ensure the normal progress of space activities and the life safety of astronauts,reduce or eliminate the harm of charged particles to spacecraft and astronauts,and carry out other scientific research.At present,the payload volume of space particle detectors on satellites is relatively large,which is difficult to meet the needs of astronauts.To solve this problem,this thesis takes charged particles in low earth orbit(LEO)space as monitor the target,and designs a portable low-noise and low-power dosimeter and a multi-channel pulse measurement spectrometer based on Silicon(Si)detector.The main work done is as follows:First of all,this thesis analyzes the energy and flux of charged particles in LEO space.Compared with the several detectors,and chooses Si as the sensor to detect charged particles.The deposition energy of protons and electrons in Si is simulated by Geant4,and the energy range of charged particles detected by Si is 100KeV-6MeV.Simultaneously,according to the Si and the energy range of detecting particles,designs a radiation detection system that matches them.Secondly,for astronauts to carry and measure in real time,this thesis proposes a low-power and low-noise portable dosimeter design scheme,which uses low-power MSP430FR6989 as the core controller,combined with amplification circuit,particle energy screening circuit and bias circuit to measure charged particles.Among them,this thesis designs a transformer with voltage doubling circuit provides 30V bias voltage for Si;To measure the deposited energy of particles in an Si,this thesis designs a kind of low-power,low-noise charge sensitive preamplifier(CSA)circuit and filter shaping circuit,the accuracy of the circuit design is verified by simulation;To improve the energy resolution and measurement accuracy,this thesis designs a kind of particle energy discriminator circuit,set the programmable threshold voltage,by measuring the width of the pulse signal to replace the traditional pulse signal amplitude,greatly reduces the power consumption measurement.According to the measured pulse signal width calculated charged particles deposited energy in the Si detector,and calculate the dose,dose rate and cumulative dose rate information.Thirdly,in order to detect the radiation dose of astronauts’ key organs in space,this thesis designs a multi-channel spectrometer to measure the pulse signal of the measurement.The structure of the Si detector and its bias voltage and front-end readout amplifier circuit are consistent with that of the dosimeter.In addition,this thesis designs ADC conversion circuit based on LTC2295 and FPGA peripheral circuit based on XC7K325TFFG900 core board.The ADC conversion circuit to collects the amplified pulse signal and FPGA realizes the functions of peak value extraction,data storage,counting and energy spectrum shaping.This thesis designed a FPGA particle detecting PC software,realize the PC and the FPGA command control and data transmission.Finally,in order to verify the validity and accuracy of the dosimeter and energy spectrometer design,this thesis establish the test space particle radiation detection experimental platform.Firstly,the dark current and energy resolution of Si detector were tested;Then,the dosimeter and energy spectrometer were tested with 241Am(5486KeV),239Pu(5155 KeV)and function signal generator.The experimental results show that the design of a portable dosimeter the machine running on the total power consumption of about 2.16 mW,the linear fitting degree is up to 99.5%,and the 241Am energy resolution is about 2.63%.The energy spectrometer can collect the amplitude value of the pulse signal through the multi-channel ADC,and get the peak value of the pulse signal by the peak extraction algorithm in FPGA,and finally upload the data to the FPGA particle detection software for analysis and processing. |
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