| In the material analysis and identification,environmental radioactive detection,nuclear equipment radioactive detection and prevention of nuclear terrorism and other aspects,the radionuclide identification technology has a wide range of applications.Radionuclide identification is based on the gamma spectrum which measures the spectral information to determine the material or the environment of radioactive material species and strength.The topic is from the National Natural Science Foundation of China “Earth and lunar surface induced gamma radiation field And its geological response”(Item no:41374136)and National 863 project "high-precision energy spectrum detection equipment research and development"(Project Number:2012AA061803).According to the IAEA requirements for portable energy spectrometer,for the Na I(Tl)and La Br3(Ce)detector's features,major in the smoothing spectrum?finding peak position and boundary?the energy scale?the efficiency scale?peak area function fitting and peak area solution,and get good results.(1)The Least-squares fitting and the five-point fitting method are used to fit the spectral line to achieve the characteristics of smoothing fast,good effect and keeping the original peak shape.In the method of finding the peak,the derivative method is fast,the calculation is simple and it is suitable for the computer to find the peak automatically.On the basic of original derivative method,adding peak width and minimum threshold to improve the accuracy of the peak.(2)We improve the SNIP algorithm based on the original algorithm.The window width is determined dynamically by the peak boundary count,it improves the shortcomings of SNIP that energy window is fixed.,and uses the decreasing method to iterate the calculation.Finally,the fourth order filter function is used to calculate instead of the original second order filter function,background deduction on the above of 95%.Whe we calculating the peak area,we firstly judge whether it is a single peak or an overlapping peak.For the single peak,we calculation the peak area by universal peak area method.For the overlapping peak,the area is calculated by combining the Gaussian fitting and SNIP with the straight line background.This way has advantage which can reduce the computational complexity?accelerate the calculation speed and calculate accurately.The results show that the error can be control within the 8.9%(Na I(Tl))and 3.7%(La Br3(Ce)).(3)The linearity of the detector is improved by energizing the Na I detector on U?Th?K natural background and mixed models(better than0.9998).And Am-241 was used to confirm the detection limit of the detector which is 50 ke V.Ra-226 was used to detect the efficiency of the detector(better 0.997).(4)According to the IAEA standard,a nuclide identification method is adopted which uses feature peaks?The algorithm completes the IAEA requirements for nuclide identification of Na I portable instrument by qualitative analysis.At the same time,we can identify more extensive ranges of nuclides and combinations by the quantitative analysis.The least squares-inverse matrix method is used to carry out the solution,which greatly reduces the operation steps and times.The algorithm can calculate the result on the mobile device within 1 seconds The algorithm's adaptive is good and suits for Na I(Tl)and La Br3(Ce)detectors.In this paper,a nuclide Identification algorithms for Na I(Tl)and La Br3(Ce)detectors is developed to meet the requirements of IAEA nuclide identification.For different scintillation detectors,the algorithm can be embedded to other instruments by adjusting the peak width parameter according to the energy resolution. |
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