Development Of Digital Spectrometer Based On LASO Detector

Nowadays,the nuclear science and technology have been widely used in many fields,such as medicine,physics,agriculture,industry,environmental science,and customs security.The application of nuclear technology,on the one hand,have been making great contribution to our world,on other hand,it also poses a number of threats to the world,in which the illegal transfer of radioactive nuclear materials and the nuclear accidents have posed various challenges to customs security and nuclear power plants.Therefore,a new portable LASO detector which can measures the neutron / gamma spectra in the mixing field have been developed.This detector which can monitor the complex radioactive materials can be used for the detection of customs security and the measuring abnormal leakage of radioactive materials in the nuclear power plants.At present,dual probe technology is used to detect neutron and gamma at the same time,that is,neutron detector and gamma detector are used to detect neutrons and gamma rays respectively.But it not only increases the volume and weight of the detection system,but also makes the detection system more expensive and more complex.Therefore,a single probe technology based on the LASO scintillator detector is proposed in this paper,and the digital processing technology of the spectrometer was combined to actualize the measurement of the neutron-gamma mixture field.At first,in this paper,the advantages and disadvantages of single detector technology and dual detector technology have been compared,and a design scheme of single probe digital spectrometer which can measure neutron / gamma spectra in a mixed field is proposed.Secondly,the technical points of system design are proposed.The energy spectra system includes the hardware system,the discrimination algorithm and the software system.The hardware system of the spectrometer includes power supply circuit,high voltage circuit,filter circuit,signal conditioning circuit,high speed ADC acquisition circuit,FPGA signal processing circuit,communication circuit,and MCU main control circuit.The hardware system above can adjust,collect,process,store,display and transmit the detector signals.Among these hardware system,the high-voltage circuit and power circuit have the advantages of simple structure,adjustable voltage output,small volume,low noise and low cost.The LRC filter circuit has better filtering effect on noise and ripple in DC voltage.To remove the interference between neutron and gamma ray measurement,neutron gamma discrimination algorithms were studied.The principles and characteristics of the screening methods are stated,which have a practical and simple amplitude discriminating method.Finally,the μC/OS-Ⅱ multi task real-time operating system software and user-based-on interface layer were designed The μC/OS-Ⅱ operating system was transplanted to the ARM controller.With the multi-task software function layer,data acquisition,processing,storage,transmission,spectra display and other functions can be realized.The introduction of μC/OS-Ⅱ operating system makes the spectrometer software more stable and more easier to develop.After the design work of whole detection system,the digitized spectrometer has been presented and introduced in this paper,which includes power supply board,the digital multichannel board,the main control board and the internal structure of the instrument.Then,some hardware circuits were tested.The high voltage circuit and the output voltage of the power circuit reach the desired design goal.The filter circuit has a good effect on reducing the noise ripple of the high voltage circuit and the output voltage of the power circuit.When the LASO detector detects the gamma rays generated by the Cs source,the pulse signal outputs normally,and after the signal conditioning circuit,the pulse waveform meeting the design requirements can be output.Finally,in the mixed field containing neutron and gamma ray,the analysis of the test results shows that the digital energy spectrometer based on LASO detector can realize the discrimination of neutron-gamma ray and the energy spectra measurement.