The Fast Nuclide Identification Method And Instrument Development Based On FPGA

The fast ? nuclide identification instrument is a portable nuclear detection and analysis instrument based on multi-channel spectrometer.The instrument is mainly used in the locale of field measurement environment,can achieve radioactivity detection,radioactive source positioning,energy spectrum display and nuclide identification and other functions.In addition,the instrument is also widely used in resource exploration,medical and health,environmental monitoring and other fields.The system uses the CH158-06 Na I(Tl)scintillation detector which is produced by Beijing Hamamatsu Electronics as a detection module to detect ?-ray and produce nuclear pulse signals.The AD8022 operational amplifier is used to implement inverse and amplification of the nuclear pulse signals.ADI's AD9235-20 analog-to-digital converter achieves high-speed sampling of nuclear pulse signals;Altera's FPGA chip(EP2C8Q208C8N)is used as the control core to process digital nuclear pulse signals;HC-05 Bluetooth module is used as a wireless communication module,to achieve communication between the upper and lower computers;the system uses 24 V lithium battery pack,through a series of power conversion circuit,to achieve the power supply to various components.FPGA internal modules are designed by using Verilog language,which is including: clock frequency division module,sampling control module,Gaussian shaping module,amplitude extraction module,RAM read and write module and serial communication module.The upper computer software is written in Java language to display and analyze the spectrum data.The system uses the Android handheld terminals as information display carriers.This paper introduces a nuclide identification algorithm based on the gamma-ray spectrum,which mainly includes: energy spectrum data smoothing algorithm,peak position determination algorithm,energy calibration algorithm,and nuclide identification algorithm based on characteristic peak matching.After system hardware and software debugged,the system was tested by using three radioactive sources,Cs-137,Eu-155 and Na-22.Mainly tested the three indicators which included spectrum effect comparison,energy resolution,and system stability.The test results show that the energy spectrum display effect is good;The energy resolution of the system for Cs-137 is about 7.03%;The characteristic peak spectrum drifts within 3 channels.The performance of the instrument is stable and reliable,and the measurement is accurate.It is suitable for on-site field measurement environment.