A large-volume HPGe detector normally has a severe ballistic deficit due to its long rise time of the output signals.Despite the trapezoidal shaping algorithm adopted as a remedy to deal with the signals,the algorithm...A large-volume HPGe detector normally has a severe ballistic deficit due to its long rise time of the output signals.Despite the trapezoidal shaping algorithm adopted as a remedy to deal with the signals,the algorithm cannot fully eliminate the ballistic deficit in the case of a high counting rate.To resolve the problem,we propose a ballistic deficit compensation method that is based on the measurement of rise time of the signals before shaping.We find that the ballistic deficit after trapezoidal shaping has little relation to the time constant,but shows a quadratic relationship with the rise time and has a negative correlation with the shaping time.In the case of high count rates,the high resolution is handled by fitting the curve to the rise time and the amplitude deficit of the signal after shaping and by compensating for the signal amplitude after trapezoidal shaping.Tests indicate that when the count rate is about 100 kcps,the resolution of Co-60 improves from traditional 2.32 up to 1.91 keV,thus reaching a higher level.展开更多
With the development of large-scale spectral surveys, fiber positioning technology has been developing rapidly. Because of the performance advantages of a four-quadrant（4Q） detector, a fiber positioning and real-tim...With the development of large-scale spectral surveys, fiber positioning technology has been developing rapidly. Because of the performance advantages of a four-quadrant（4Q） detector, a fiber positioning and real-time monitoring system based on the 4Q detector is proposed. The detection accuracy of this system is directly determined by the precision of the center of the spot. A Gaussian fitting algorithm based on the 4Q detector is studied and applied in the fiber positioning process to improve the calculated accuracy of the spot center. The relationship between the center position of the incident spot and the detector output signal is deduced. An experimental platform is built to complete the simulated experiment. Then we use the Gaussian fitting method to process experimental data, compare the fitting value with the theoretical one and calculate the corresponding error.展开更多
A systematic study of the distribution of the Naturally Occurring Radioactive Materials as well as the anthropogenic radionuclide in the working environment of the Shipbreaking yards of Sitakunda, Chittagong, Banglade...A systematic study of the distribution of the Naturally Occurring Radioactive Materials as well as the anthropogenic radionuclide in the working environment of the Shipbreaking yards of Sitakunda, Chittagong, Bangladesh, has been carried out with an objective of establishing reliable base line data on the radiation level and hence to measure the radiation dose expose to the workers and to the inhabitants of the studied area. Fifteen Soil samples have been col-lected from five different Shipbreaking yards. Three sampling spots in each yard have been selected for having repre-sentative samples for the assessment of radioactivity releasing from 226Ra (238U), 232Th and their daughters and 40K us-ing the Digital Gamma-ray Spectrometry system coupled with a High Purity Germanium (HPGe;Canberra, 40% rela-tive efficiency, 1.8 keV resolution at 1332 keV of 60Co) detector and PC based Multichannel Analyzer (MCA, upto 16k channel). The software Genie 2000 (Canberra) and Hypermet PC have been used for data acquisition and gamma peak analysis, respectively. Each of fifteen soils (~200g) and two standards (IAEA-Soil-6 and 800Bq liquid 226Ra sprayed in Al2O3) were counted in cylindrical plastic pot using gamma spectrometry system for 20000 sec for the determination of activity concentrations of the radionuclides. The samples and standards were kept in air tied condition at least for 4 weeks before gamma counting to attain the radioactive equilibrium between daughters and parents of 226Ra (238U) and 232Th decay series. The Al2O3 based 226Ra standard was used for the construction of efficiency curve covering the wide gamma energy range. The IAEA-Soil-6 was used for quality control (QC) of the analysis. The homogeneity test and density corrections of Al2O3 based 226Ra standard were performed and implemented for the analysis. The results of ac-tivity concentrations have been used to assess the radium equivalent activities (Raeq) and the representative level index (Iγr) values in the experimental soil samples. The results have been compared with other global radioactivity measure-ments and evaluations.展开更多
The uncertainty of nuclide libraries in the analysis of the gamma spectra of low-and intermediate-level radioactive waste(LILW)using existing methods produces unstable results.To address this problem,a novel spectral ...The uncertainty of nuclide libraries in the analysis of the gamma spectra of low-and intermediate-level radioactive waste(LILW)using existing methods produces unstable results.To address this problem,a novel spectral analysis method is proposed in this study.In this method,overlapping peaks are located using a continuous wavelet transform.An improved quadratic convolution method is proposed to calculate the widths of the peaks and establish a fourth-order filter model to estimate the Compton edge baseline with the overlapping peaks.Combined with the adaptive sensitive nonlinear iterative peak,this method can effectively subtracts the background.Finally,a function describing the peak shape as a filter is used to deconvolve the energy spectrum to achieve accurate qualitative and quantitative analyses of the nuclide without the aid of a nuclide library.Gamma spectrum acquisition experiments for standard point sources of Cs-137 and Eu-152,a segmented gamma scanning experiment for a 200 L standard drum,and a Monte Carlo simulation experiment for triple overlapping peaks using the closest energy of three typical LILW nuclides(Sb-125,Sb-124,and Cs-134)are conducted.The results of the experiments indicate that(1)the novel method and gamma vision(GV)with an accurate nuclide library have the same spectral analysis capability,and the peak area calculation error is less than 4%;(2)compared with the GV,the analysis results of the novel method are more stable;(3)the novel method can be applied to the activity measurement of LILW,and the error of the activity reconstruction at the equivalent radius is 2.4%;and(4)The proposed novel method can quantitatively analyze all nuclides in LILW without a nuclide library.This novel method can improve the accuracy and precision of LILW measurements,provide key technical support for the reasonable disposal of LILW,and ensure the safety of humans and the environment.展开更多
Two measurement systems, one being comprised of three HPGe detectors and the other being a 4π measurement system of the assembly of 10 sets of scintillation detectors, were compared for their measurement performance ...Two measurement systems, one being comprised of three HPGe detectors and the other being a 4π measurement system of the assembly of 10 sets of scintillation detectors, were compared for their measurement performance in operations of radioactive waste drum radioactivity measurement and clearance and release operation of decommissioning. The system features of the former were high costs, capable of identifying radionuclides, a measurement time of about 1000 sec. The system features of the latter were high sensibility, capable of identifying hotspots, a measurement time of about 100 sec. Various comparisons were made for the differences of the two systems on reference drums, whole-drum homogeneous and non-homogeneous metal drums and non-metal drums, whole-drums of different filling rates. The aim was to compare the differences of the two measurement systems in measuring radioactivity of critical radionuclides of <sup>137</sup>Cs, <sup>54</sup>Mn and <sup>60</sup>Co.展开更多
High purity germanium detectors have important applications in many fields. Detector’s performance deteriorated significantly due to radiation of neutron. The annealing of damaged HPGe detector is expounded in this m...High purity germanium detectors have important applications in many fields. Detector’s performance deteriorated significantly due to radiation of neutron. The annealing of damaged HPGe detector is expounded in this monograph. The experiment results indicate that raising the temperature to 70°C for five days, the restoration efficiency can reach 90%.展开更多
X光机绝对光子数的测量在X射线计量中有着十分重要的意义,对其进行测量时需先将探测器的能量—道址函数进行刻度。本文使用放射源对HPGe探测器进行能量刻度,得到其能量—道址函数且其线性相关系数R2=0.999 84。论文结合了CT成像技术,对...X光机绝对光子数的测量在X射线计量中有着十分重要的意义,对其进行测量时需先将探测器的能量—道址函数进行刻度。本文使用放射源对HPGe探测器进行能量刻度,得到其能量—道址函数且其线性相关系数R2=0.999 84。论文结合了CT成像技术,对探测器进行平行光束探测效率的MC模拟,使建模更精确。模拟结果显示,探测效率曲线在11.0 ke V处会出现吸收边,是因为Ge元素被激发产生Kα、Kβ特征X射线发生逃逸,未被记录下来形成逃逸峰所致,这与实际实验情况相符。展开更多
基金supported by Natural Science Foundation of China(No.41274109)Youth Innovation Team of Sichuan Province(2015TD0020)
文摘A large-volume HPGe detector normally has a severe ballistic deficit due to its long rise time of the output signals.Despite the trapezoidal shaping algorithm adopted as a remedy to deal with the signals,the algorithm cannot fully eliminate the ballistic deficit in the case of a high counting rate.To resolve the problem,we propose a ballistic deficit compensation method that is based on the measurement of rise time of the signals before shaping.We find that the ballistic deficit after trapezoidal shaping has little relation to the time constant,but shows a quadratic relationship with the rise time and has a negative correlation with the shaping time.In the case of high count rates,the high resolution is handled by fitting the curve to the rise time and the amplitude deficit of the signal after shaping and by compensating for the signal amplitude after trapezoidal shaping.Tests indicate that when the count rate is about 100 kcps,the resolution of Co-60 improves from traditional 2.32 up to 1.91 keV,thus reaching a higher level.
基金support by the Fundamental Research Funds for the Central Universities of China (2013/B15020271)the National Natural Science Foundation of China (1014/515029111)the National Undergraduate Training Program for Innovation and Entrepreneurship (201610294069)
文摘With the development of large-scale spectral surveys, fiber positioning technology has been developing rapidly. Because of the performance advantages of a four-quadrant（4Q） detector, a fiber positioning and real-time monitoring system based on the 4Q detector is proposed. The detection accuracy of this system is directly determined by the precision of the center of the spot. A Gaussian fitting algorithm based on the 4Q detector is studied and applied in the fiber positioning process to improve the calculated accuracy of the spot center. The relationship between the center position of the incident spot and the detector output signal is deduced. An experimental platform is built to complete the simulated experiment. Then we use the Gaussian fitting method to process experimental data, compare the fitting value with the theoretical one and calculate the corresponding error.
文摘A systematic study of the distribution of the Naturally Occurring Radioactive Materials as well as the anthropogenic radionuclide in the working environment of the Shipbreaking yards of Sitakunda, Chittagong, Bangladesh, has been carried out with an objective of establishing reliable base line data on the radiation level and hence to measure the radiation dose expose to the workers and to the inhabitants of the studied area. Fifteen Soil samples have been col-lected from five different Shipbreaking yards. Three sampling spots in each yard have been selected for having repre-sentative samples for the assessment of radioactivity releasing from 226Ra (238U), 232Th and their daughters and 40K us-ing the Digital Gamma-ray Spectrometry system coupled with a High Purity Germanium (HPGe;Canberra, 40% rela-tive efficiency, 1.8 keV resolution at 1332 keV of 60Co) detector and PC based Multichannel Analyzer (MCA, upto 16k channel). The software Genie 2000 (Canberra) and Hypermet PC have been used for data acquisition and gamma peak analysis, respectively. Each of fifteen soils (~200g) and two standards (IAEA-Soil-6 and 800Bq liquid 226Ra sprayed in Al2O3) were counted in cylindrical plastic pot using gamma spectrometry system for 20000 sec for the determination of activity concentrations of the radionuclides. The samples and standards were kept in air tied condition at least for 4 weeks before gamma counting to attain the radioactive equilibrium between daughters and parents of 226Ra (238U) and 232Th decay series. The Al2O3 based 226Ra standard was used for the construction of efficiency curve covering the wide gamma energy range. The IAEA-Soil-6 was used for quality control (QC) of the analysis. The homogeneity test and density corrections of Al2O3 based 226Ra standard were performed and implemented for the analysis. The results of ac-tivity concentrations have been used to assess the radium equivalent activities (Raeq) and the representative level index (Iγr) values in the experimental soil samples. The results have been compared with other global radioactivity measure-ments and evaluations.
基金supported by the National Natural Science Foundation of China(Nos.12205190,11805121)the Science and Technology Commission of Shanghai Municipality(No.21ZR1435400).
文摘The uncertainty of nuclide libraries in the analysis of the gamma spectra of low-and intermediate-level radioactive waste(LILW)using existing methods produces unstable results.To address this problem,a novel spectral analysis method is proposed in this study.In this method,overlapping peaks are located using a continuous wavelet transform.An improved quadratic convolution method is proposed to calculate the widths of the peaks and establish a fourth-order filter model to estimate the Compton edge baseline with the overlapping peaks.Combined with the adaptive sensitive nonlinear iterative peak,this method can effectively subtracts the background.Finally,a function describing the peak shape as a filter is used to deconvolve the energy spectrum to achieve accurate qualitative and quantitative analyses of the nuclide without the aid of a nuclide library.Gamma spectrum acquisition experiments for standard point sources of Cs-137 and Eu-152,a segmented gamma scanning experiment for a 200 L standard drum,and a Monte Carlo simulation experiment for triple overlapping peaks using the closest energy of three typical LILW nuclides(Sb-125,Sb-124,and Cs-134)are conducted.The results of the experiments indicate that(1)the novel method and gamma vision(GV)with an accurate nuclide library have the same spectral analysis capability,and the peak area calculation error is less than 4%;(2)compared with the GV,the analysis results of the novel method are more stable;(3)the novel method can be applied to the activity measurement of LILW,and the error of the activity reconstruction at the equivalent radius is 2.4%;and(4)The proposed novel method can quantitatively analyze all nuclides in LILW without a nuclide library.This novel method can improve the accuracy and precision of LILW measurements,provide key technical support for the reasonable disposal of LILW,and ensure the safety of humans and the environment.
文摘Two measurement systems, one being comprised of three HPGe detectors and the other being a 4π measurement system of the assembly of 10 sets of scintillation detectors, were compared for their measurement performance in operations of radioactive waste drum radioactivity measurement and clearance and release operation of decommissioning. The system features of the former were high costs, capable of identifying radionuclides, a measurement time of about 1000 sec. The system features of the latter were high sensibility, capable of identifying hotspots, a measurement time of about 100 sec. Various comparisons were made for the differences of the two systems on reference drums, whole-drum homogeneous and non-homogeneous metal drums and non-metal drums, whole-drums of different filling rates. The aim was to compare the differences of the two measurement systems in measuring radioactivity of critical radionuclides of <sup>137</sup>Cs, <sup>54</sup>Mn and <sup>60</sup>Co.
文摘High purity germanium detectors have important applications in many fields. Detector’s performance deteriorated significantly due to radiation of neutron. The annealing of damaged HPGe detector is expounded in this monograph. The experiment results indicate that raising the temperature to 70°C for five days, the restoration efficiency can reach 90%.
文摘X光机绝对光子数的测量在X射线计量中有着十分重要的意义,对其进行测量时需先将探测器的能量—道址函数进行刻度。本文使用放射源对HPGe探测器进行能量刻度,得到其能量—道址函数且其线性相关系数R2=0.999 84。论文结合了CT成像技术,对探测器进行平行光束探测效率的MC模拟,使建模更精确。模拟结果显示,探测效率曲线在11.0 ke V处会出现吸收边,是因为Ge元素被激发产生Kα、Kβ特征X射线发生逃逸,未被记录下来形成逃逸峰所致,这与实际实验情况相符。
