Design Of A Random Simulated Nuclear Pulse Signal Generator

Nuclear radiation plays a very important role in the development of modern science.It is widely used in medical nuclear magnetic resonance?NMR?,space exploration,industrial nondestructive testing,national defense safety and so on.Humans can't sense nuclear radiation directly.At present,the nuclear pulse signals used in the laboratory are mainly obtained by using radioactive sources and detectors.But nuclear radiation may cause harm to the health of the experimenters.And the nuclear detector is expensive and easily damaged.At the same time,the existing imitated nuclear pulse signal generator is still in the early stage of research,and the corresponding products are very few.For the above two reasons,this paper designs an imitated nuclear pulse signal generator based on FPGA and C#.The system can produce 9 kinds of imitated nuclear pulse signals,and the method is very simple and the resources used are low.The system lays a foundation for the more powerful and more perfect imitated nuclear pulse signal generator.The design method of imitated nuclear pulse amplitude system is as follows:Firstly,the standard Gauss pulse waveform data based on function expression is generated by mixed programming of C#and MATLAB,and then the communication between computer and FPGA is realized by cy7c68013a chip of Cypress Company.Sending the standard Gauss pulse waveform data and nuclear selection parameters to the FPGA.USB chip working requires USB driver and USB firmware in addition to the chip itself.The USB register is configured by the USB firmware program to control the USB transmission.The FPGA adopts Cyclone IV series chip EP4CE10F17C8N of Altera company.The FPGA digital circuits mainly include USB control module,Gauss pulse waveform data storage module,random number generation module,feature spectrum Gauss pulse generation module and DAC control module.All the FPGA digital modules are verified by Signaltap II logic analyzer of Quartus II.The design method of the imitated nuclear pulse width system is as follows:The system is realized directly based on FPGA which does not involve PC and the communication between host computer and FPGA.The selection of imitated nuclear pulse is realized by matrix keystrokes.The FPGA digital circuits of the system mainly include random number generation module,key scanning module,Characteristic spectrum Gauss pulse generation module and pulse width conversion module.In the experiment part,firstly,the imitated nuclear pulse amplitude system was used to test the performance of four radioactive isotope(²²Na ¹³³Ba ²⁴¹Am ¹³⁷Cs).Through analysis the pulse shape,energy resolution and stability of Gauss pulse to judge performance of the system.The results show that the imitated nuclear pulse signal generator can generate Gauss pulse which simulates the characteristic line of nuclide and characterized by high stability and reliability.Four radioactive isotope(²²Na ¹³³Ba ²⁴¹Am¹³⁷Cs)have been used to test the performance of imitated nuclear pulse width system.The results show that the pulse width is proportional to the main photon energy of the corresponding nuclide.The number of output pulses of various nuclides corresponds to the corresponding characteristic lines of nuclides.