In April 2017, a mini neutron monitor (NM) was installed at King Abdulaziz City for Science and Technology (KACST) central Saudi Arabia (Riyadh;cut-off rigidity, Rc = 14.4 Gv) for continuous observation of the cosmic ...In April 2017, a mini neutron monitor (NM) was installed at King Abdulaziz City for Science and Technology (KACST) central Saudi Arabia (Riyadh;cut-off rigidity, Rc = 14.4 Gv) for continuous observation of the cosmic ray (CR) neutrons. The detector was built as a major aspect of the international scientific joint effort between the Centre of Space Research (North-West University, Potchefstroom, South Africa) and KACST. The recorded data correspond to low energy neutrons that primarily have energies lower than 20 GeV. In this paper, a brief description about the mini NM detector will be given. The influence of atmospheric pressure on the recorded CR neutrons was studied and the barometric coefficient was calculated and used to eliminate the pressure effects from the measured data. The obtained coefficient was consistent with those previously obtained by several investigators. The daily variation of the CR neutron was studied and characterized. Short-term CR periodicities, such as the 27-day period, and its two harmonics, were identified. The obtained periodicities are in agreement with those reported by different researchers. The obtained results from this detector have been compared to the existing 1 m<sup>2</sup> scintillator detector showing comparable results. Long-term data from this detector will be of incredible significance to the research community to investigate several types of CR variations resulting from solar activity at such high cut off rigidity site.展开更多
A spherical tissue equivalent proportional counter(TEPC) for neutron monitoring has been developed. It was properly designed to produce a uniform electric field intensity around the anode wire. An internal ^(241)Am al...A spherical tissue equivalent proportional counter(TEPC) for neutron monitoring has been developed. It was properly designed to produce a uniform electric field intensity around the anode wire. An internal ^(241)Am alpha source was adopted for lineal energy calibration. The TEPC was characterized in terms of dose equivalent response in a standard ^(252)Cf neutron field, and was tested with 2.45 MeV neutrons. Microdosimetric spectra, frequency mean lineal energy and dose-average mean lineal energy of 2.45 MeV neutrons were obtained and compared with FLUKA Monte Carlo simulation results. The measurement and simulation results agreed well. The mean quality factor and dose equivalent values evaluated from the 2.45 MeV neutron measurement were in good agreement with the recommended effective quality factor and ambient dose equivalent H*(10),respectively. Preliminary results have proved the availability of the developed TEPC for neutron monitoring.展开更多
The neutron flux monitor(NFM)system is an important diagnostic subsystem introduced by large nuclear fusion devices such as international thermonuclear experimental reactor(ITER),Japan torus-60,tokamak fusion test rea...The neutron flux monitor(NFM)system is an important diagnostic subsystem introduced by large nuclear fusion devices such as international thermonuclear experimental reactor(ITER),Japan torus-60,tokamak fusion test reactor,and HL-2 A.Neutron fluxes can provide real-time parameters for nuclear fusion,including neutron source intensity and fusion power.Corresponding to different nuclear reaction periods,neutron fluxes span over seven decades,thereby requiring electronic devices to operate in counting and Campbelling modes simultaneously.Therefore,it is crucial to design a real-time NFM system to encompass such a wide dynamic range.In this study,a high-precision NFM system with a wide measurement range of neutron flux is implemented using realtime multipoint linear calibration.It can automatically switch between counting and Campbelling modes with variations in the neutron flux.We established a testing platform to verify the feasibility of the NFM system,which can output the simulated neutron signal using an arbitrary waveform generator.Meanwhile,the accurate calibration interval of the Campbelling mode is defined well.Based on the above-mentioned design,the system satisfies the requirements,offering a dynamic range of 10~8 cps,temporal resolution of 1 ms,and maximal relative error of 4%measured at the signal-to-noise ratio of 15.8 dB.Additionally,the NFM system is verified in a field experiment involving HL-2 A,and the measured neutron flux is consistent with the results.展开更多
The neutron count rate fluctuation reaches six orders of magnitude between the ohmic plasma scenario and high power of auxiliary heating on an experimental advanced superconducting tokamak(EAST).The measurement result...The neutron count rate fluctuation reaches six orders of magnitude between the ohmic plasma scenario and high power of auxiliary heating on an experimental advanced superconducting tokamak(EAST).The measurement result of neutron flux monitoring(NFM)is a significant feedback parameter related to the acquisition of radiation protection-related information and rapid fluctuations in neutron emission induced by plasma magnetohydrodynamic activity.Therefore,a wide range and high time resolution are required for the NFM system on EAST.To satisfy these requirements,a digital pulse signal acquisition and processing system with a wide dynamic range and fast response time was developed.The present study was conducted using a field-programmable gate array(FPGA)and peripheral component interconnect extension for instrument express(PXIe)platform.The digital dual measurement modes,which are composed of the pulse-counting mode and AC coupled square integral's Campbelling mode,were designed to expand the measurement range of the signal acquisition and processing system.The time resolution of the signal acquisition and processing system was improved from 10 to 1 ms owing to utilizing highspeed analog-to-digital converters(ADCs),a high-speed PXIe communication with a direct memory access(DMA)mode,and online data preprocessing technology of FPGA.The signal acquisition and processing system was tested experimentally in the EAST radiation field.The test results showed that the time resolution of NFM was improved to 1 ms,and the dynamic range of the neutron counts rate was expanded to more than 10^(6) counts per second.The Campbelling mode was calibrated using a multipoint average linear fitting method;subsequently,the fitting coefficient reached 0.9911.Therefore,the newly developed pulse signal acquisition and processing system ensures that the NFM system meets the requirements of high-parameter experiments conducted on EAST more effectively.展开更多
Neutron flux monitor （NFM） as an important diagnostic sub-system in ITER （international thermonuclear experimental reactor） provides a global neutron source intensity, fusion power and neutron flux in real time. T...Neutron flux monitor （NFM） as an important diagnostic sub-system in ITER （international thermonuclear experimental reactor） provides a global neutron source intensity, fusion power and neutron flux in real time. Three types of neutron flux monitor assemblies with different sensitivities and shielding materials have been designed. Through MCNP （Mante-Carlo neutral particle transport code） calculations, this extended system of NFM can detect the neutron flux in a range of 10^4 n/（cm^2.s） to 10^14 n/（cm^2.s）. It is capable of providing accurate neutron yield measurements for all operational modes encountered in the ITER experiments including the in-situ calibration. Combining both the counting mode and Campbelling （MSV; Mean Square Voltage） mode in the signal processing units, the requirement of the dynamic range （107） for these NFMs and time resolution （1 ms） can be met. Based on a uncertainty analysis, the estimated absolute measurement accuracies of the total fusion neutron yield can reach the required 10% level in both the early stage of the DD-phase and the DD-phase, the absolute measurement accuracy full power DT operation mode. In the advanced would be better than 20%.展开更多
The prototype neutron flux monitor consists of a high purity ^(235)U fission chamber detector and a'blank'detector,which is a fissile material free detector with the same dimension as the fission chamber detec...The prototype neutron flux monitor consists of a high purity ^(235)U fission chamber detector and a'blank'detector,which is a fissile material free detector with the same dimension as the fission chamber detector to identify noise issues such as noise coming from gamma rays.The main parameters of the fission chamber assembly that have been measured in the laboratory are confirmed to approach the technological level of the International Thermonuclear Experimental Reactor(ITER)in the near future.This prototype neutron flux monitor will be further developed to become a neutron flux monitor suitable for the operation phase of D-D fusion on the ITER.展开更多
To satisfy high-precision,widc-rangc,and real-time neutron flux measurement requirements by the International Thermonuclear Experimental Reactor(ITF.R),a data acquisition and control system based on fission chamber de...To satisfy high-precision,widc-rangc,and real-time neutron flux measurement requirements by the International Thermonuclear Experimental Reactor(ITF.R),a data acquisition and control system based on fission chamber detectors and fast controller technology,has been developed for neutron flux monitor in ITER Equatorial Port#7.The signal processing units which arc based on a field programmable gate array and the PXI Express platform arc designed to realize the neutron flux measurement with I ms time resolution and a fast response less than 0.2 ms,together with real-time timestamps provided by a timing hoard.The application of the wide-range algorithm allows the system to measure up to 10^10cps with a relative error of less than 5%.Furthermore,the system is managed and controlled by a software based on the Experimental Physics and Industrial Control System,compliant with COntrol.Data Access and Communication architecture.展开更多
A small-angle scattering neutron spectrometer for material research is under construction at the China Spallation Neutron Source. An intervening neutron beam monitor behind the sample is needed to measure the beam int...A small-angle scattering neutron spectrometer for material research is under construction at the China Spallation Neutron Source. An intervening neutron beam monitor behind the sample is needed to measure the beam intensity in order to reduce the measurement uncertainty caused by beam fluctuation. Considering the mobility requirement and limited space, we proposed a compact monitor using a type of lithium-glass scintillator provided by China Building Materials Academy. Its performance was studied experimentally using ^(252)Cf and ^(60)Co sources.The neutron light yield of the selected scintillator was measured to be 5:3 × 10~3 photons/neutron. The feasibility of n-gamma discrimination using the charge comparison method was verified. By using the Geant4 toolkit, themonitor was modeled with precise physical processes including neutron tracking, scintillation, and optical photon transmission. The gamma sensitivity and detection efficiency were investigated in the simulation. It was concluded that a 0.5-mm-thick lithium-glass scintillator with natural lithium is an appropriate choice to satisfy both the neutron detection efficiency and gamma elimination requirements.展开更多
A novel full-digital real-time neutron flux monitor(NFM) has been developed for thorium-based molten salt reactor(TMSR).The system is based on the highspeed,parallel,and pipeline processing of the field programmable g...A novel full-digital real-time neutron flux monitor(NFM) has been developed for thorium-based molten salt reactor(TMSR).The system is based on the highspeed,parallel,and pipeline processing of the field programmable gate array as well as the high-stability controller area network platform.A measurement range of 10~8 counts per second is achieved with a single fission chamber by utilizing the normalization of the count and Campbell algorithms.With the advantages of using the measurement range,system integrity,and real-time performance,digital NFM has been tested in the Xi'an pulsed reactor fission experiments and was found to exhibit superior experimental performance.展开更多
As a key part of the diagnosis system in the International Thermonuclear Experimental Reactor(ITER),the neutron flux monitor(NFM),which measures the neutron intensity of the fusion reaction,is a Counting-Campbelling s...As a key part of the diagnosis system in the International Thermonuclear Experimental Reactor(ITER),the neutron flux monitor(NFM),which measures the neutron intensity of the fusion reaction,is a Counting-Campbelling system with a large dynamic counting range.A dynamic linear calibration method is proposed in this paper to solve the problem of cross-over between the different counting and Campbelling channels,and improve the accuracy of the cross-calibration for long-term operation.The experimental results show that the NFM system with the dynamic linear calibration system can obtain the neutron flux of the fusion reactor in real time and realize the seamless measurement area connection between the two channels.展开更多
The links of many medical-biological events with high levels of geomagnetic activity (GMA) are widely discussed. In recent years, several medical phenomena were described in inverse distribution by time with GMA. Also...The links of many medical-biological events with high levels of geomagnetic activity (GMA) are widely discussed. In recent years, several medical phenomena were described in inverse distribution by time with GMA. Also a concurrent to GMA and solar activity force-cosmic ray activity (CRA) and closely related high energy neutron and proton fluxes are studied as a forces dominating at low GMA and solar activity in relation to considered medical events. The aim of this study was to explore the distribution of some important medical events on days with “Zero” GMA levels, accompanied by high CRA (neutron activity). Medical event data of the Grand Baku region (more than 3 mln inhabitants), Azerbaijan, with daily distribution on the time 1 Dec. 2002-31 Dec. 2007 was compared to daily GMA Kp indices in general (Kp > 0, 1837 days) and 34 days daily GMA indices Kp = 0. Daily CRA data was also compared using neutron monitoring data from two stations. Daily averaged data and their standard deviations on the mentioned GMA levels were compared and statistical significance was established. Results revealed a significant rise in the number of emergencies (n = 1,567,576) and total deaths number (n = 46,360) at the days of “Zero” GMA level. These days were accompanied by significant rise of CRA (neutron activity). For Sudden Cardiac Deaths (SCD, n = 1615) and cerebral stroke (CVA, n =10,054) the increase achieved strong trend to significance level. Acute Myocardial Infarction occurrence (morbidity) and trauma were also absolutely more registered at days with “Zero” GMA level, despite the small number of such days. The average Infection numbers show an inverse relationship with absolutely high registry at the “Zero” GMA level days. Study linking environmental physical activity levels and the human medical data shows that geomagnetic field variations accompanied by the increased level of cosmic ray activity, can have either direct or indirect adverse effects on human health and physiology, even when the magnitude of the geomagnetic field disturbance is extremely small or even is equal to zero. On days of “Zero” daily Kp indices describing Geomagnetic Activity, accompanied by high Cosmic Ray Activity (neutron activity), more medical emergencies and total death number (daily) occurred. Sudden Cardiac Deaths and Cerebral Stroke numbers show a strong trend to significant rise. Absolute increase of number of Acute Myocardial Infarction and less Infections, not achieving statistical significance, was also observed. These results are additional data for considering Cosmic Ray Activity (neutron activity) as an additional factor involved in time distribution of human medical events.展开更多
In fast reactors, the inherent neutron source strength is often insufficient for monitoring the reactor start-up operation with ex-core detectors. To increase the subcritical neutron flux, an auxiliary neutron source ...In fast reactors, the inherent neutron source strength is often insufficient for monitoring the reactor start-up operation with ex-core detectors. To increase the subcritical neutron flux, an auxiliary neutron source subassembly(SSA) is generally used to overcome this problem. In this study, the estimated neutron source strength and detector count rate of an antimony-beryllium-based SSA are obtained using the deterministic transport code DORT and Monte Carlo calculations. Because the antimony activation rate is a critical parameter, its sensitivity to the capture cross section and neutron flux spectrum is studied. The reaction cross section sensitivity is studied by considering data from different evaluated nuclear data files.It is observed that, because of the variation in the cross sections from different evaluated nuclear data files, the values of the saturation gamma(> 1.67 MeV) activity and neutron strength predicted by ORIGEN2 lie within ±2%.The obtained antimony activation rate and sensitivity to the neutron flux are partially validated by irradiating samples of antimony in the KAMINI reactor. The average onegroup capture cross sections of bare and cadmium-covered 123Sb samples obtained by the ratio method are 4.0 and 1.78 b, respectively. The results of the calculation predicting the activated neutron source strength as a function of operating time and sensitivity to the neutron spectrum in the irradiation region are also presented.展开更多
针对钍基熔盐堆白光中子源(Thorium Molten Salt Reactor with a Particle and Neutron Source,TMSRPNS)在运行过程中出现中子束流掉束或打火导致的束流不稳定的问题,有必要设计研发一种具有高计数率、低中子束流影响、高中子/伽马甄别...针对钍基熔盐堆白光中子源(Thorium Molten Salt Reactor with a Particle and Neutron Source,TMSRPNS)在运行过程中出现中子束流掉束或打火导致的束流不稳定的问题,有必要设计研发一种具有高计数率、低中子束流影响、高中子/伽马甄别性能的中子束流监测器。基于蒙特卡罗模拟软件Geant4,系统研究了薄膜塑料闪烁中子束流监测器的中子转换层厚度、闪烁体厚度,以及入射窗材料等关键参数对薄膜闪烁体的影响规律,分析结果表明:闪烁体中子转换层厚度约为2μm时具有相对合适的本征探测效率;闪烁体厚度为0.5 mm、甄别阈值为0.8 MeV时监测器具备γ射线不灵敏性能。同时,通过对比不同入射窗材料对于γ射线产生电子以及对中子散射的影响,选取电子产生较少且中子散射较小的铝作为入射窗材料。研究结果可为后续的中子束流监测器实物制备提供理论依据。展开更多
文摘In April 2017, a mini neutron monitor (NM) was installed at King Abdulaziz City for Science and Technology (KACST) central Saudi Arabia (Riyadh;cut-off rigidity, Rc = 14.4 Gv) for continuous observation of the cosmic ray (CR) neutrons. The detector was built as a major aspect of the international scientific joint effort between the Centre of Space Research (North-West University, Potchefstroom, South Africa) and KACST. The recorded data correspond to low energy neutrons that primarily have energies lower than 20 GeV. In this paper, a brief description about the mini NM detector will be given. The influence of atmospheric pressure on the recorded CR neutrons was studied and the barometric coefficient was calculated and used to eliminate the pressure effects from the measured data. The obtained coefficient was consistent with those previously obtained by several investigators. The daily variation of the CR neutron was studied and characterized. Short-term CR periodicities, such as the 27-day period, and its two harmonics, were identified. The obtained periodicities are in agreement with those reported by different researchers. The obtained results from this detector have been compared to the existing 1 m<sup>2</sup> scintillator detector showing comparable results. Long-term data from this detector will be of incredible significance to the research community to investigate several types of CR variations resulting from solar activity at such high cut off rigidity site.
基金Supported by the Key Technology of Fusion Reactor Radiation Protection Foundation(No.2014GB112005)
文摘A spherical tissue equivalent proportional counter(TEPC) for neutron monitoring has been developed. It was properly designed to produce a uniform electric field intensity around the anode wire. An internal ^(241)Am alpha source was adopted for lineal energy calibration. The TEPC was characterized in terms of dose equivalent response in a standard ^(252)Cf neutron field, and was tested with 2.45 MeV neutrons. Microdosimetric spectra, frequency mean lineal energy and dose-average mean lineal energy of 2.45 MeV neutrons were obtained and compared with FLUKA Monte Carlo simulation results. The measurement and simulation results agreed well. The mean quality factor and dose equivalent values evaluated from the 2.45 MeV neutron measurement were in good agreement with the recommended effective quality factor and ambient dose equivalent H*(10),respectively. Preliminary results have proved the availability of the developed TEPC for neutron monitoring.
基金supported by the National Natural Science Foundation of China(Nos.11475131,11975307,and 11575184)the National Magnetic Confinement Fusion Energy Development Research(No.2013GB104003)。
文摘The neutron flux monitor(NFM)system is an important diagnostic subsystem introduced by large nuclear fusion devices such as international thermonuclear experimental reactor(ITER),Japan torus-60,tokamak fusion test reactor,and HL-2 A.Neutron fluxes can provide real-time parameters for nuclear fusion,including neutron source intensity and fusion power.Corresponding to different nuclear reaction periods,neutron fluxes span over seven decades,thereby requiring electronic devices to operate in counting and Campbelling modes simultaneously.Therefore,it is crucial to design a real-time NFM system to encompass such a wide dynamic range.In this study,a high-precision NFM system with a wide measurement range of neutron flux is implemented using realtime multipoint linear calibration.It can automatically switch between counting and Campbelling modes with variations in the neutron flux.We established a testing platform to verify the feasibility of the NFM system,which can output the simulated neutron signal using an arbitrary waveform generator.Meanwhile,the accurate calibration interval of the Campbelling mode is defined well.Based on the above-mentioned design,the system satisfies the requirements,offering a dynamic range of 10~8 cps,temporal resolution of 1 ms,and maximal relative error of 4%measured at the signal-to-noise ratio of 15.8 dB.Additionally,the NFM system is verified in a field experiment involving HL-2 A,and the measured neutron flux is consistent with the results.
基金supported by the Users with Excellence Program of the Hefei Science Center CAS (No. 2020HSC-UE012)
文摘The neutron count rate fluctuation reaches six orders of magnitude between the ohmic plasma scenario and high power of auxiliary heating on an experimental advanced superconducting tokamak(EAST).The measurement result of neutron flux monitoring(NFM)is a significant feedback parameter related to the acquisition of radiation protection-related information and rapid fluctuations in neutron emission induced by plasma magnetohydrodynamic activity.Therefore,a wide range and high time resolution are required for the NFM system on EAST.To satisfy these requirements,a digital pulse signal acquisition and processing system with a wide dynamic range and fast response time was developed.The present study was conducted using a field-programmable gate array(FPGA)and peripheral component interconnect extension for instrument express(PXIe)platform.The digital dual measurement modes,which are composed of the pulse-counting mode and AC coupled square integral's Campbelling mode,were designed to expand the measurement range of the signal acquisition and processing system.The time resolution of the signal acquisition and processing system was improved from 10 to 1 ms owing to utilizing highspeed analog-to-digital converters(ADCs),a high-speed PXIe communication with a direct memory access(DMA)mode,and online data preprocessing technology of FPGA.The signal acquisition and processing system was tested experimentally in the EAST radiation field.The test results showed that the time resolution of NFM was improved to 1 ms,and the dynamic range of the neutron counts rate was expanded to more than 10^(6) counts per second.The Campbelling mode was calibrated using a multipoint average linear fitting method;subsequently,the fitting coefficient reached 0.9911.Therefore,the newly developed pulse signal acquisition and processing system ensures that the NFM system meets the requirements of high-parameter experiments conducted on EAST more effectively.
基金National Natural Science Foundation of China(Nos.10175021,10675124)
文摘Neutron flux monitor （NFM） as an important diagnostic sub-system in ITER （international thermonuclear experimental reactor） provides a global neutron source intensity, fusion power and neutron flux in real time. Three types of neutron flux monitor assemblies with different sensitivities and shielding materials have been designed. Through MCNP （Mante-Carlo neutral particle transport code） calculations, this extended system of NFM can detect the neutron flux in a range of 10^4 n/（cm^2.s） to 10^14 n/（cm^2.s）. It is capable of providing accurate neutron yield measurements for all operational modes encountered in the ITER experiments including the in-situ calibration. Combining both the counting mode and Campbelling （MSV; Mean Square Voltage） mode in the signal processing units, the requirement of the dynamic range （107） for these NFMs and time resolution （1 ms） can be met. Based on a uncertainty analysis, the estimated absolute measurement accuracies of the total fusion neutron yield can reach the required 10% level in both the early stage of the DD-phase and the DD-phase, the absolute measurement accuracy full power DT operation mode. In the advanced would be better than 20%.
基金The project supported by the National Natural Science Foundation of China(No.10175021)the Retraining Foundation of the Southwestern Institute of Physics for Talented Personnel
文摘The prototype neutron flux monitor consists of a high purity ^(235)U fission chamber detector and a'blank'detector,which is a fissile material free detector with the same dimension as the fission chamber detector to identify noise issues such as noise coming from gamma rays.The main parameters of the fission chamber assembly that have been measured in the laboratory are confirmed to approach the technological level of the International Thermonuclear Experimental Reactor(ITER)in the near future.This prototype neutron flux monitor will be further developed to become a neutron flux monitor suitable for the operation phase of D-D fusion on the ITER.
文摘To satisfy high-precision,widc-rangc,and real-time neutron flux measurement requirements by the International Thermonuclear Experimental Reactor(ITF.R),a data acquisition and control system based on fission chamber detectors and fast controller technology,has been developed for neutron flux monitor in ITER Equatorial Port#7.The signal processing units which arc based on a field programmable gate array and the PXI Express platform arc designed to realize the neutron flux measurement with I ms time resolution and a fast response less than 0.2 ms,together with real-time timestamps provided by a timing hoard.The application of the wide-range algorithm allows the system to measure up to 10^10cps with a relative error of less than 5%.Furthermore,the system is managed and controlled by a software based on the Experimental Physics and Industrial Control System,compliant with COntrol.Data Access and Communication architecture.
基金supported by the National Key R&D Program of China(No.2017YFA0403702)the Instrument Developing Project of the Chinese Academy of Sciences(No.YZ201512)the National Natural Science Foundation of China(Nos.11635012,11405191,and11205036)
文摘A small-angle scattering neutron spectrometer for material research is under construction at the China Spallation Neutron Source. An intervening neutron beam monitor behind the sample is needed to measure the beam intensity in order to reduce the measurement uncertainty caused by beam fluctuation. Considering the mobility requirement and limited space, we proposed a compact monitor using a type of lithium-glass scintillator provided by China Building Materials Academy. Its performance was studied experimentally using ^(252)Cf and ^(60)Co sources.The neutron light yield of the selected scintillator was measured to be 5:3 × 10~3 photons/neutron. The feasibility of n-gamma discrimination using the charge comparison method was verified. By using the Geant4 toolkit, themonitor was modeled with precise physical processes including neutron tracking, scintillation, and optical photon transmission. The gamma sensitivity and detection efficiency were investigated in the simulation. It was concluded that a 0.5-mm-thick lithium-glass scintillator with natural lithium is an appropriate choice to satisfy both the neutron detection efficiency and gamma elimination requirements.
基金supported by the National Natural Science Foundation of China(Nos.11375195 and 11575184)the National Magnetic Confinement Fusion Energy Development Research(No.2013GB104003)
文摘A novel full-digital real-time neutron flux monitor(NFM) has been developed for thorium-based molten salt reactor(TMSR).The system is based on the highspeed,parallel,and pipeline processing of the field programmable gate array as well as the high-stability controller area network platform.A measurement range of 10~8 counts per second is achieved with a single fission chamber by utilizing the normalization of the count and Campbell algorithms.With the advantages of using the measurement range,system integrity,and real-time performance,digital NFM has been tested in the Xi'an pulsed reactor fission experiments and was found to exhibit superior experimental performance.
基金Supported by ITER Plan National Major Project(No.2008GB109000)
文摘As a key part of the diagnosis system in the International Thermonuclear Experimental Reactor(ITER),the neutron flux monitor(NFM),which measures the neutron intensity of the fusion reaction,is a Counting-Campbelling system with a large dynamic counting range.A dynamic linear calibration method is proposed in this paper to solve the problem of cross-over between the different counting and Campbelling channels,and improve the accuracy of the cross-calibration for long-term operation.The experimental results show that the NFM system with the dynamic linear calibration system can obtain the neutron flux of the fusion reactor in real time and realize the seamless measurement area connection between the two channels.
文摘The links of many medical-biological events with high levels of geomagnetic activity (GMA) are widely discussed. In recent years, several medical phenomena were described in inverse distribution by time with GMA. Also a concurrent to GMA and solar activity force-cosmic ray activity (CRA) and closely related high energy neutron and proton fluxes are studied as a forces dominating at low GMA and solar activity in relation to considered medical events. The aim of this study was to explore the distribution of some important medical events on days with “Zero” GMA levels, accompanied by high CRA (neutron activity). Medical event data of the Grand Baku region (more than 3 mln inhabitants), Azerbaijan, with daily distribution on the time 1 Dec. 2002-31 Dec. 2007 was compared to daily GMA Kp indices in general (Kp > 0, 1837 days) and 34 days daily GMA indices Kp = 0. Daily CRA data was also compared using neutron monitoring data from two stations. Daily averaged data and their standard deviations on the mentioned GMA levels were compared and statistical significance was established. Results revealed a significant rise in the number of emergencies (n = 1,567,576) and total deaths number (n = 46,360) at the days of “Zero” GMA level. These days were accompanied by significant rise of CRA (neutron activity). For Sudden Cardiac Deaths (SCD, n = 1615) and cerebral stroke (CVA, n =10,054) the increase achieved strong trend to significance level. Acute Myocardial Infarction occurrence (morbidity) and trauma were also absolutely more registered at days with “Zero” GMA level, despite the small number of such days. The average Infection numbers show an inverse relationship with absolutely high registry at the “Zero” GMA level days. Study linking environmental physical activity levels and the human medical data shows that geomagnetic field variations accompanied by the increased level of cosmic ray activity, can have either direct or indirect adverse effects on human health and physiology, even when the magnitude of the geomagnetic field disturbance is extremely small or even is equal to zero. On days of “Zero” daily Kp indices describing Geomagnetic Activity, accompanied by high Cosmic Ray Activity (neutron activity), more medical emergencies and total death number (daily) occurred. Sudden Cardiac Deaths and Cerebral Stroke numbers show a strong trend to significant rise. Absolute increase of number of Acute Myocardial Infarction and less Infections, not achieving statistical significance, was also observed. These results are additional data for considering Cosmic Ray Activity (neutron activity) as an additional factor involved in time distribution of human medical events.
文摘In fast reactors, the inherent neutron source strength is often insufficient for monitoring the reactor start-up operation with ex-core detectors. To increase the subcritical neutron flux, an auxiliary neutron source subassembly(SSA) is generally used to overcome this problem. In this study, the estimated neutron source strength and detector count rate of an antimony-beryllium-based SSA are obtained using the deterministic transport code DORT and Monte Carlo calculations. Because the antimony activation rate is a critical parameter, its sensitivity to the capture cross section and neutron flux spectrum is studied. The reaction cross section sensitivity is studied by considering data from different evaluated nuclear data files.It is observed that, because of the variation in the cross sections from different evaluated nuclear data files, the values of the saturation gamma(> 1.67 MeV) activity and neutron strength predicted by ORIGEN2 lie within ±2%.The obtained antimony activation rate and sensitivity to the neutron flux are partially validated by irradiating samples of antimony in the KAMINI reactor. The average onegroup capture cross sections of bare and cadmium-covered 123Sb samples obtained by the ratio method are 4.0 and 1.78 b, respectively. The results of the calculation predicting the activated neutron source strength as a function of operating time and sensitivity to the neutron spectrum in the irradiation region are also presented.
文摘针对钍基熔盐堆白光中子源(Thorium Molten Salt Reactor with a Particle and Neutron Source,TMSRPNS)在运行过程中出现中子束流掉束或打火导致的束流不稳定的问题,有必要设计研发一种具有高计数率、低中子束流影响、高中子/伽马甄别性能的中子束流监测器。基于蒙特卡罗模拟软件Geant4,系统研究了薄膜塑料闪烁中子束流监测器的中子转换层厚度、闪烁体厚度,以及入射窗材料等关键参数对薄膜闪烁体的影响规律,分析结果表明:闪烁体中子转换层厚度约为2μm时具有相对合适的本征探测效率;闪烁体厚度为0.5 mm、甄别阈值为0.8 MeV时监测器具备γ射线不灵敏性能。同时,通过对比不同入射窗材料对于γ射线产生电子以及对中子散射的影响,选取电子产生较少且中子散射较小的铝作为入射窗材料。研究结果可为后续的中子束流监测器实物制备提供理论依据。
