Hardware System Design For Carborne γ-ray Spectrometer

With the rapid development of China’s nuclear power industry and environmental protection increasingly attention,environmental radioactive testing requires a fast,highly sensitive measurement means.In recent years,vehicle gamma spectrometry has developed into a survey and evaluation of radiation environmental pollution(such as estimating the rate of absorption of terrestrial Gamma air),monitoring of nuclear facilities,emergency monitoring of nuclear accidents,emergency monitoring of anti-nuclear terrorist attacks and neighboring nuclear tests Caused by the main support technology for nuclear pollution monitoring.The topic of this thesis is from the National Natural Science Foundation of China,"Research on Gamma-ray Field and Geological Response of Earth and Moon"(Item No.41374136)and National 863 Project "High-precision Spectrum Detection Instrument Development"(subject number : 2012AA061803).In view of China’s radiation environmental monitoring,nuclear emergency,radioactive earth exploration and other special application requirements,to carry out vehicle gamma spectrometer research and development.In this paper,the whole structure of the vehicle gamma spectrometer is introduced,and the selection of the gamma ray detector and the multi-channel pulse amplitude analyzer is analyzed and discussed.The power supply circuit of the vehicle γ spectrometer,the main controller circuit,Communication circuits and other hardware systems,as well as the main controller program code,measurement control,data cache and transmission functions such as programming.The main research work and research results are as follows:1.The signal readout and energy spectrum acquisition functions for a number of large volume Na I(Tl)detectors are realized,and the bus networking function between the multi-channel spectrum acquisition devices is realized based on CAN bus.2.In order to realize the automatic station and mobile patrol working mode of the vehicle γ spectrometer,the system should meet the requirements of auto power function and self-power supply.This system has built a 12 V,80AH large capacity lithium battery pack,and designed a multi-channelpower supply and charging channel,to achieve different power supply voltage,different interface mode of automatic adjustment and switching,in order to achieve a stable energy spectrometer power supply design The In order to meet the requirements of the long-term field work of the vehicle γ spectrometer,this paper also designed a 500 W DC/AC inverter power supply to charge the military notebook computer in the system and realize the continuous measurement.3.To ensure the timing of energy spectrum acquisition and processing analysis,the main control system uses Cortex-M4 core,180 MHz frequency,32-bit RISC architecture STM32F429 IG,external expansion of 64 MB SDRAM for data cache.In order to ensure the quality of the dose mapping and the GIS dose trajectory,the BD910 high precision differential GPS receiver is used.The positioning accuracy is 0.5m(SBAS),0.25m(DGNSS),0.008m(Single Baseline RTK),with 20 Hz positioning information output,Equipped with a 40 d B high gain antenna,the direction of the beam width,low elevation signal reception effect is excellent,can ensure that the block in the case of serious normal search stars.4.The system designed a CAN bus communication circuit for 10 energy spectrum detectors.The pre-transmission command is designed to eliminate the problem that the sampling time of multiple energy spectrum detectors due to time consuming data communication is not synchronized.In order to improve the reliability and convenience of communication,the main control system and military notebook can communicate with each other through Wi Fi,serial port and Ethernet,and set the priority to realize automatic switching.The spectrometer system uses 3G communication technology to realize the data interaction between the vehicle system measurement data and the remote local data center.5.The system combined with GIS geographic information and measurement of energy spectrum data to achieve the color difference spectrum,the dose trajectory map and dose mapping.In the chromatic aberration spectrum spectrum can quickly detect radioactive anomalies and to achieve rapid identification of nuclides and activity calculation;the system can automatically converted into a dose according to the spectrum,combined with the vehicle’s measurement trajectory to draw the dose trajectory map,built Surfer8 mapping Software,automatic mapping interface to achieve dose mapping function.