The Key Technology And System Implementation Of Digital Multi-Channel Pulse Amplitude Analyzer Based On FPGA

The digital multi-channel pulse amplitude analyzer as the core component of digital nuclear instruments,which design performance will directly affect the function realization and the performance improvement,especially in the case of high counting rate,the design and implementation of multi-channel pulse amplitude analyzer based on FPGA has significantly improved the performance of nuclear instrument in ballistic deficit and pulse pile-up,and further improved the integration and stability of the instrument system.The thesis mainly completed the following work:（1）Based on the analysis of nuclear radiation detection technology and multi-channel pulse amplitude analyzer,the design scheme of digital multi-channel pulse amplitude analyzer system based on FPGA is determined.And divided the system function into A/D conversion control,trapezoidal shaping,baseline estimation,pile-up rejection,amplitude extraction,spectral line storage and communication control modules.And completed the simulation analysis and hardware implementation of the logic,according to the implementation principle and implementation method of each module.（2）Completed the hardware logic circuit design and PCB circuit board production of the digital multi-channel pulse amplitude analyzer,and put the main nuclear pulse signal processing logic implementation into the FPGA.（3）The Matlab/Simulink simulation platform,DSP Builder system-level model development kit,Cypress-USB development kit,and Quartus II integrated development software environment were used in the module design process,which realized the integrated design of software simulation and system implementation.（4）After the design was completed,the NaI（Tl）gamma spectroscopy experimental test platform was built by using the NaI（Tl）detector as the front-end analog nuclear signal processing unit in the paper.Finally,the paper uses ¹³⁷Cs as the radio source to perform functional test and performance test on the designed digital multi-channel pulse amplitude analyzer.In the functional test,the fast and slow trapezoidal shaping effect,the peak extraction effect and the USB2.0 data transmission effect were measured,and the results showed that the test effect was good.In the performance test,the instrument energy resolution of the Gaussian shaping method was tested at about 7.64%,and the instrumental energy resolution of the trapezoidal shaping method was 7.31%,which verified that the trapezoidal shaping method has higher energy resolution;in 24 hours,the ¹³⁷Cs source was tested every 2 hours,and the results showed that the address was shifted by only one channel,which verifies the stability of the system;through the curve fitting of the corresponding relation between energy and the channel address of ¹³⁷Cs and ⁶⁰Co,The results showed that the fitting degree is 95%and the energy linearity is good.The instrument test results showed that the digital multi-channel pulse amplitude analyzer based on FPGA have met the system design requirements,optimized the trapezoidal digital shaping algorithm,improved the performance of the light weight digital system,increased the pass rate of digital pulse of the system and has good detection effect.