A 2＂×2＂BC501A liquid scintillation detector with a gain stabilization system is developed and applied to neutron andγ-ray measurement on the EAST tokamak.Energy calibration of a liquid scintillator using a fas...A 2＂×2＂BC501A liquid scintillation detector with a gain stabilization system is developed and applied to neutron andγ-ray measurement on the EAST tokamak.Energy calibration of a liquid scintillator using a fast coincidence method is presented and compared with the Monte Carlo simulation.Determination of the proton light output function of the BC501A is presented.Results from dedicated experiments with an Am-Be neutron source,γsource and quasi-monoenergetic neutron beams,and from measurements on EAST tokamak are presented and discussed.展开更多
An experimental system aimed at n-γ discrimination using the zero-crossing method with a φ3’’×2’’ BC501A liquid scintillation detector was established and tested with an Am-Be neutron source. Two-dimensiona...An experimental system aimed at n-γ discrimination using the zero-crossing method with a φ3’’×2’’ BC501A liquid scintillation detector was established and tested with an Am-Be neutron source. Two-dimensional plots of energy versus zero-crossing time were obtained. The quality of n-γ discrimination was checked by the figure-of-merit （FOM）, the neutron peak-to-valley ratio, and the proportion of leaked neutrons over all neutron events. The performance of n-γ discrimination in terms of FOM was compared with previous work done by other groups. The n-γ discrimination in four different energy regions with an interval of 0.1 MeV between 0.3 MeV and 0.7 MeV was studied, and the results indicate that the n-γ discrimination threshold can go down to 0.4 MeV.展开更多
A VME-based experiment system for n-y discrimination using the charge comparison method was established.A data acquisition program for controlling the programmable modules and processing data online via VME64X bus was...A VME-based experiment system for n-y discrimination using the charge comparison method was established.A data acquisition program for controlling the programmable modules and processing data online via VME64X bus was developed through the use of Lab VIEW.The two-dimensional（2D） scatter plots of the charge in the slow component vs.the total charge from ^（241）Am-Be and 252Cf neutron sources are presented.The 2D scatter plots of the energy vs.the ratio of the charge in the slow component to the total charge of the pulses are also presented.The quality of n-γ discrimination was checked by the figure-of-merit,and the results showed good performance of n-γ discrimination at the low energy range.Neutrons and γ-rays were separated above 50 keVee（electron-equivalent energy）.The quality of n-γ discrimination has been improved compared with others＇ results at five energies（150,250,350,450,550 keVee）.展开更多
Accurate knowledge of the neutron energy spectra is useful in basic research and applications. The overall procedure of measuring and unfolding the fast neutron energy spectra with BC501 A liquid scintillation detecto...Accurate knowledge of the neutron energy spectra is useful in basic research and applications. The overall procedure of measuring and unfolding the fast neutron energy spectra with BC501 A liquid scintillation detector is described. The recoil proton spectrum of 241Am-Be neutrons was obtained experimentally. With the NRESP7 code, the response matrix of detector was simulated.Combining the recoil proton spectrum and response matrix, the unfolding of neutron spectra was performed by GRAVEL iterative algorithm. A MatLab program based on the GRAVEL method was developed. The continuous neutron spectrum of 241Am-Be source and monoenergetic neutron spectrum of D-T source have been unfolded successfully and are in good agreement with their standard reference spectra. The unfolded 241Am-Be spectrum are more accurate than the spectra unfolded by artificial neural networks in recent years.展开更多
The n-γ discrimination performance of two experimental arrangements based on the rise-time method and the zero-crossing method was compared for a 50.8 mm-diametered and 50.8 mm-high BC501A liquid scintillator coupled...The n-γ discrimination performance of two experimental arrangements based on the rise-time method and the zero-crossing method was compared for a 50.8 mm-diametered and 50.8 mm-high BC501A liquid scintillator coupled to a 50.8 mm-diametered 9807B photomultiplier in this work. The low energy limitation of the detected neutron with different detector high voltages and the figure of merit of the n-γ discrimination in four neutron energy regions (1–2 MeV, 0.75–1 MeV, 0.5–0.75 MeV and below 0.5 MeV) were studied by using the Am-Be neutron source. Under a time statistical model of the photoelectron emission process in scintillation counters, the intrinsic capability of the n-γ discrimination performance under the optimal condition was evaluated. The experimental results of the zero-crossing method demonstrate a better n-γ. discrimination performance than those of the rise-time method, which is consistent with the calculated results.展开更多
Based on the multi-coincidence measurement, the time resolution of three liquid scintillation detectors （BC501A） were determined strictly by solving the coincidence equations, where the influence from electronics es...Based on the multi-coincidence measurement, the time resolution of three liquid scintillation detectors （BC501A） were determined strictly by solving the coincidence equations, where the influence from electronics estimated by self coincidence measurement as well as the background had been considered. The result of this work agreed well with the result that was deduced from the traditional method, and it will be helpful to analyze the energy resolution of neutron time of flight spectra measured by using such detectors at CIAE （China Institute of Atomic Energy）.展开更多
基金supported by the National Magnetic Confinement Fusion Science Program of China(Nos.2013GB106004 and 2012GB101003)National Natural Science Foundation of China(No.91226102)
文摘A 2＂×2＂BC501A liquid scintillation detector with a gain stabilization system is developed and applied to neutron andγ-ray measurement on the EAST tokamak.Energy calibration of a liquid scintillator using a fast coincidence method is presented and compared with the Monte Carlo simulation.Determination of the proton light output function of the BC501A is presented.Results from dedicated experiments with an Am-Be neutron source,γsource and quasi-monoenergetic neutron beams,and from measurements on EAST tokamak are presented and discussed.
文摘研究了对BC501A液体闪烁体对γ射线的光输出响应特性。实验上利用γ放射源(60Co,137Cs)测量了不同光电倍增管高压下,尺寸为Φ5.08 cm×5.08 cm的BC501A液体闪烁体探测器的脉冲幅度谱。利用Geant4软件进行模拟,计算结果与实验数据很好地符合,得到了能量分辨函数及能量刻度曲线。利用Geant4研究了BC501A的脉冲幅度谱的康普顿边缘Ec、康普顿峰Emax及康普顿半高点E1/2与能量分辨率的关系。同时模拟结果显示,随γ射线能量(0.2～3 Me V)的增加,康普顿边缘位置Nc/Nmax从0.8至0.7线性减少。
文摘An experimental system aimed at n-γ discrimination using the zero-crossing method with a φ3’’×2’’ BC501A liquid scintillation detector was established and tested with an Am-Be neutron source. Two-dimensional plots of energy versus zero-crossing time were obtained. The quality of n-γ discrimination was checked by the figure-of-merit （FOM）, the neutron peak-to-valley ratio, and the proportion of leaked neutrons over all neutron events. The performance of n-γ discrimination in terms of FOM was compared with previous work done by other groups. The n-γ discrimination in four different energy regions with an interval of 0.1 MeV between 0.3 MeV and 0.7 MeV was studied, and the results indicate that the n-γ discrimination threshold can go down to 0.4 MeV.
文摘A VME-based experiment system for n-y discrimination using the charge comparison method was established.A data acquisition program for controlling the programmable modules and processing data online via VME64X bus was developed through the use of Lab VIEW.The two-dimensional（2D） scatter plots of the charge in the slow component vs.the total charge from ^（241）Am-Be and 252Cf neutron sources are presented.The 2D scatter plots of the energy vs.the ratio of the charge in the slow component to the total charge of the pulses are also presented.The quality of n-γ discrimination was checked by the figure-of-merit,and the results showed good performance of n-γ discrimination at the low energy range.Neutrons and γ-rays were separated above 50 keVee（electron-equivalent energy）.The quality of n-γ discrimination has been improved compared with others＇ results at five energies（150,250,350,450,550 keVee）.
文摘Accurate knowledge of the neutron energy spectra is useful in basic research and applications. The overall procedure of measuring and unfolding the fast neutron energy spectra with BC501 A liquid scintillation detector is described. The recoil proton spectrum of 241Am-Be neutrons was obtained experimentally. With the NRESP7 code, the response matrix of detector was simulated.Combining the recoil proton spectrum and response matrix, the unfolding of neutron spectra was performed by GRAVEL iterative algorithm. A MatLab program based on the GRAVEL method was developed. The continuous neutron spectrum of 241Am-Be source and monoenergetic neutron spectrum of D-T source have been unfolded successfully and are in good agreement with their standard reference spectra. The unfolded 241Am-Be spectrum are more accurate than the spectra unfolded by artificial neural networks in recent years.
文摘The n-γ discrimination performance of two experimental arrangements based on the rise-time method and the zero-crossing method was compared for a 50.8 mm-diametered and 50.8 mm-high BC501A liquid scintillator coupled to a 50.8 mm-diametered 9807B photomultiplier in this work. The low energy limitation of the detected neutron with different detector high voltages and the figure of merit of the n-γ discrimination in four neutron energy regions (1–2 MeV, 0.75–1 MeV, 0.5–0.75 MeV and below 0.5 MeV) were studied by using the Am-Be neutron source. Under a time statistical model of the photoelectron emission process in scintillation counters, the intrinsic capability of the n-γ discrimination performance under the optimal condition was evaluated. The experimental results of the zero-crossing method demonstrate a better n-γ. discrimination performance than those of the rise-time method, which is consistent with the calculated results.
基金Supported by State Key Development Program for Basic Research of China (2009GB107001, 2008CB717803, 2007CB209903)Research Fund for Doctoral Program of Higher Education of China (200610011023)
文摘Based on the multi-coincidence measurement, the time resolution of three liquid scintillation detectors （BC501A） were determined strictly by solving the coincidence equations, where the influence from electronics estimated by self coincidence measurement as well as the background had been considered. The result of this work agreed well with the result that was deduced from the traditional method, and it will be helpful to analyze the energy resolution of neutron time of flight spectra measured by using such detectors at CIAE （China Institute of Atomic Energy）.
