Low background gamma spectrometry was used to measure the radionuclides activity of <sup>238</sup>U, <sup>232</sup>Th, and <sup>235</sup>U series as well as <sup>40</sup>...Low background gamma spectrometry was used to measure the radionuclides activity of <sup>238</sup>U, <sup>232</sup>Th, and <sup>235</sup>U series as well as <sup>40</sup>K and <sup>137</sup>Cs in a sediment sample. The goal of the study was to measure the <sup>238</sup>U (63.3 keV peak of <sup>234</sup>Th;1001 keV peak of <sup>234m</sup>Pa) and <sup>235</sup>U (143.76 keV, 163.33 keV, and 205.31 keV peaks) activity by low background gamma spectrometry in sediment sample. <sup>235</sup>U activity in environmental samples is difficult to accurately measure by gamma spectrometry due to its low abundance in nature and low gamma line intensities at 143.76 keV, 163.33 keV, and 205.31 keV. We have shown that by using low background gamma spectrometry, it is possible to accurately measure the <sup>235</sup>U activity in sediment samples. The <sup>235</sup>U activity was measured without using the major peak of 185.7 keV (I<sub>γ</sub> = 57.2%) which requires interference correction from 186.21 keV of <sup>226</sup>Ra. <sup>226</sup>Ra activity was determined by measuring <sup>222</sup>Rn daughters (<sup>214</sup>Pb and <sup>214</sup>Bi). The precision and accuracy of the gamma activity measurement in the sediment sample were verified by using the HPGe detectors with Certified Reference Material (CRM) Irish Sea Sediment (IAEA-385). The results obtained for the 63.33 keV energy line of <sup>234</sup>Th are compared with the 1001 keV energy line of <sup>234m</sup>Pa. The values of <sup>238</sup>U and <sup>235</sup>U activities, as well as <sup>40</sup>K, <sup>137</sup>Cs, and <sup>226</sup>Ra, agreed with the certificate values of CRM. The results show that the <sup>238</sup>U is in equilibrium with its daughters (<sup>234</sup>Th, <sup>234m</sup>Pa, and <sup>210</sup>Pb). <sup>232</sup>Th is also in equilibrium with its daughters (<sup>228</sup>Ra, <sup>212</sup>Pb, <sup>212</sup>Bi and <sup>208</sup>Tl). <sup>235</sup>U/<sup>238</sup>U activity ratio of 0.046 ± 0.007 in the sediment is constant in nature but fluctuates due to geological processes. A value of 0.055 ± 0.008 was found in our sediment sample.展开更多
A low-background neutron detector array was developed to measure the cross section of the ^(13)C(a,n)^(16)O reaction,which is the neutron source for the s-process in AGB stars,in the Gamow window(E_(c.m.)=190±40 ...A low-background neutron detector array was developed to measure the cross section of the ^(13)C(a,n)^(16)O reaction,which is the neutron source for the s-process in AGB stars,in the Gamow window(E_(c.m.)=190±40 keV)at the China Jinping Underground Laboratory(CJPL).The detector array consists of 24^(3)He proportional counters embedded in a polyethylene cube.Owing to the deep underground location and a borated polyethylene shield around the detector array,a low background of 4.5(2)/h was achieved.The ^(51)V(p,n)^(51)Cr reaction was used to determine the neutron detection efficiency of the array for neutrons with energies E_(n)<1 MeV.Geant4 simulations are shown to effectively reproduce the experimental results.They were used to extrapolate the detection efficiency to higher energies for neutrons emitted in the ^(13)C(α,n)^(16)O reaction.The theoretical angular distributions of the ^(13)C(α,n)^(16)O reaction were shown to be important in the estimation of the uncertainties of the detection efficiency.展开更多
The rapid identification of γ-emitting radionuclides with low activity levels in public areas is crucial for nuclear safety.However,classical methods rely on full-energy peaks in the integral spectrum,requiring suffi...The rapid identification of γ-emitting radionuclides with low activity levels in public areas is crucial for nuclear safety.However,classical methods rely on full-energy peaks in the integral spectrum,requiring sufficient count accumulation for evaluation,thereby limiting response time.The sequential Bayesian approach,which utilizes prior information and considers both photon energies and interarrival times,can significantly enhance the performance of radionuclides identification.This study proposes a theoretical optimization method for the traditional sequential Bayesian approach.Each photon is processed sequentially,and the corresponding posterior probability is updated in real time using a noninformative prior from the Bayesian theory.By comparing the posterior probabilities of the background and radionuclides based on the energy variance and time interval,the type of γ-rays can be identified(background characteristic γ-rays,Compton plateaus γ-rays,or radionuclide-specific characteristic γ-rays).By integrating the information from these multiple characteristic γ-rays,the presence and type of radionuclides were determined based on the final decision function and a set threshold.Based on theoretical research,verification experiments were conducted using a LaBr_(3)(Ce)detector in both low-and natural background radiation environments with typical radionuclides(^(137)Cs,^(60)Co,and ^(133)Ba).The results show that this approach can identify ^(137)Cs in 7.9 s and 8.5 s(source dose rate contribution:approximately 6.5×10^(−3)μGy/h),^(60)Co in 8.1 s and 9.8 s(approximately 4.8×10^(−2)μGy/h),and ^(133)Ba in 4.05 s and 5.99 s(approximately 3.4×10^(−2)μGy/h)under low and natural background radiation,respectively,with a miss rate below 0.01%.This demonstrates the effectiveness of the proposed approach for fast radionuclides identification,even at low activity levels and highlights its potential for enhancing public safety in diverse radiation environments.展开更多
Highly oriented pyrolytic graphite (HOPG) is frequently adopted as the reaction target in12C+12C fusion reaction experiments owing to its superior purity.In this study,we investigate the reaction yield dependence on t...Highly oriented pyrolytic graphite (HOPG) is frequently adopted as the reaction target in12C+12C fusion reaction experiments owing to its superior purity.In this study,we investigate the reaction yield dependence on the accumulated beam dose on HOPG target using a novel detection system consisting of a time-projection chamber and silicon array.The reaction yields are significantly reduced under intense beam bombardment owing to radiation damage to the HOPG surface.The α_(0) and p_(0,1) yields decrease by 51.5% and 25%,respectively,when the ^(12)C^(2+) beam dose accumulates at 5 C.Using the novel detection system and HOPG target,the α0yield is determined to be 2.68_(-1.69)^(+4.69)×10^(-17/12) C after correcting for the yield loss due to radiation damage.Our result represents the highest sensitivity achieved to date in direct measurements of ^(12)C(12C,α_(0))^(20)Ne.展开更多
In order to add earthquake monitoring methods and develop new method research,the ELF Network for Earthquake Monitoring selected 30 stations in the Capital Circle and the Sichuan-Yunnan region. Finding electromagnetic...In order to add earthquake monitoring methods and develop new method research,the ELF Network for Earthquake Monitoring selected 30 stations in the Capital Circle and the Sichuan-Yunnan region. Finding electromagnetic field background variation is the basis of distinguishing the seismic electromagnetic anomalies. This paper introduces the data acquisition and selection of the Shexian,Anqiu,Lijiang and Dali stations which have recorded for longer time with better data and are located on the similar latitude. Then we use the natural source electromagnetic field's auto-power spectrum to express the intensity of the electromagnetic field. By using power spectral data of many frequencies in the observation frequency band,after the data pre-processing and sliding average noising,the background variation of extremely low frequency stations and the range ability were acquired.Taking the Baoshan M5. 1 earthquake on October 30,2015 and Dali M5. 0 earthquake on May 18,2016 as examples,the authors analyzed the earthquake electromagnetic anomaly characteristic of ELF stations around the earthquakes.展开更多
光伏新能源发电系统的电能产出受到多种外部条件的影响,包括光照强度、环境温度变化以及局部阴影的遮挡效应,容易导致其MPP(Maximum Power Point,最大功率点)发生漂移,从而难以快速准确地跟踪功率点变化。在低碳背景下,计算发电系统Boos...光伏新能源发电系统的电能产出受到多种外部条件的影响,包括光照强度、环境温度变化以及局部阴影的遮挡效应,容易导致其MPP(Maximum Power Point,最大功率点)发生漂移,从而难以快速准确地跟踪功率点变化。在低碳背景下,计算发电系统Boost电路中的占空比、输出负载、电感和电容参数,引入蚁群算法对Boost电路参数进行优化,增强搜索过程的多样性和探索性。采用随机化步长,通过模糊控制器,实现对最大功率点跟踪控制。仿真结果表明,当直流母线电压存在扰动时,所提方法可以迅速作出反应,并将电压恢复到正常水平;当光照强度骤减后,仅需要0.9 s左右的时间就可以稳定在最大功率点附近。展开更多
文摘Low background gamma spectrometry was used to measure the radionuclides activity of <sup>238</sup>U, <sup>232</sup>Th, and <sup>235</sup>U series as well as <sup>40</sup>K and <sup>137</sup>Cs in a sediment sample. The goal of the study was to measure the <sup>238</sup>U (63.3 keV peak of <sup>234</sup>Th;1001 keV peak of <sup>234m</sup>Pa) and <sup>235</sup>U (143.76 keV, 163.33 keV, and 205.31 keV peaks) activity by low background gamma spectrometry in sediment sample. <sup>235</sup>U activity in environmental samples is difficult to accurately measure by gamma spectrometry due to its low abundance in nature and low gamma line intensities at 143.76 keV, 163.33 keV, and 205.31 keV. We have shown that by using low background gamma spectrometry, it is possible to accurately measure the <sup>235</sup>U activity in sediment samples. The <sup>235</sup>U activity was measured without using the major peak of 185.7 keV (I<sub>γ</sub> = 57.2%) which requires interference correction from 186.21 keV of <sup>226</sup>Ra. <sup>226</sup>Ra activity was determined by measuring <sup>222</sup>Rn daughters (<sup>214</sup>Pb and <sup>214</sup>Bi). The precision and accuracy of the gamma activity measurement in the sediment sample were verified by using the HPGe detectors with Certified Reference Material (CRM) Irish Sea Sediment (IAEA-385). The results obtained for the 63.33 keV energy line of <sup>234</sup>Th are compared with the 1001 keV energy line of <sup>234m</sup>Pa. The values of <sup>238</sup>U and <sup>235</sup>U activities, as well as <sup>40</sup>K, <sup>137</sup>Cs, and <sup>226</sup>Ra, agreed with the certificate values of CRM. The results show that the <sup>238</sup>U is in equilibrium with its daughters (<sup>234</sup>Th, <sup>234m</sup>Pa, and <sup>210</sup>Pb). <sup>232</sup>Th is also in equilibrium with its daughters (<sup>228</sup>Ra, <sup>212</sup>Pb, <sup>212</sup>Bi and <sup>208</sup>Tl). <sup>235</sup>U/<sup>238</sup>U activity ratio of 0.046 ± 0.007 in the sediment is constant in nature but fluctuates due to geological processes. A value of 0.055 ± 0.008 was found in our sediment sample.
基金supported by the National Natural Science Foundation of China(Nos.11490564 and 11805138).
文摘A low-background neutron detector array was developed to measure the cross section of the ^(13)C(a,n)^(16)O reaction,which is the neutron source for the s-process in AGB stars,in the Gamow window(E_(c.m.)=190±40 keV)at the China Jinping Underground Laboratory(CJPL).The detector array consists of 24^(3)He proportional counters embedded in a polyethylene cube.Owing to the deep underground location and a borated polyethylene shield around the detector array,a low background of 4.5(2)/h was achieved.The ^(51)V(p,n)^(51)Cr reaction was used to determine the neutron detection efficiency of the array for neutrons with energies E_(n)<1 MeV.Geant4 simulations are shown to effectively reproduce the experimental results.They were used to extrapolate the detection efficiency to higher energies for neutrons emitted in the ^(13)C(α,n)^(16)O reaction.The theoretical angular distributions of the ^(13)C(α,n)^(16)O reaction were shown to be important in the estimation of the uncertainties of the detection efficiency.
基金supported by the Program for NIM-Basic Research Business Expenses Key Field Program,China(No.AKYCX2315).
文摘The rapid identification of γ-emitting radionuclides with low activity levels in public areas is crucial for nuclear safety.However,classical methods rely on full-energy peaks in the integral spectrum,requiring sufficient count accumulation for evaluation,thereby limiting response time.The sequential Bayesian approach,which utilizes prior information and considers both photon energies and interarrival times,can significantly enhance the performance of radionuclides identification.This study proposes a theoretical optimization method for the traditional sequential Bayesian approach.Each photon is processed sequentially,and the corresponding posterior probability is updated in real time using a noninformative prior from the Bayesian theory.By comparing the posterior probabilities of the background and radionuclides based on the energy variance and time interval,the type of γ-rays can be identified(background characteristic γ-rays,Compton plateaus γ-rays,or radionuclide-specific characteristic γ-rays).By integrating the information from these multiple characteristic γ-rays,the presence and type of radionuclides were determined based on the final decision function and a set threshold.Based on theoretical research,verification experiments were conducted using a LaBr_(3)(Ce)detector in both low-and natural background radiation environments with typical radionuclides(^(137)Cs,^(60)Co,and ^(133)Ba).The results show that this approach can identify ^(137)Cs in 7.9 s and 8.5 s(source dose rate contribution:approximately 6.5×10^(−3)μGy/h),^(60)Co in 8.1 s and 9.8 s(approximately 4.8×10^(−2)μGy/h),and ^(133)Ba in 4.05 s and 5.99 s(approximately 3.4×10^(−2)μGy/h)under low and natural background radiation,respectively,with a miss rate below 0.01%.This demonstrates the effectiveness of the proposed approach for fast radionuclides identification,even at low activity levels and highlights its potential for enhancing public safety in diverse radiation environments.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB34020200)National Key Research and Development Program(MOST 2022YFA1602304)+1 种基金Scientific Research Instrument and Equipment Development Program of the Chinese Academy of Sciences(No.GJJSTD20210007)National Natural Science Foundation of China(Nos.12175156,U1632142).
文摘Highly oriented pyrolytic graphite (HOPG) is frequently adopted as the reaction target in12C+12C fusion reaction experiments owing to its superior purity.In this study,we investigate the reaction yield dependence on the accumulated beam dose on HOPG target using a novel detection system consisting of a time-projection chamber and silicon array.The reaction yields are significantly reduced under intense beam bombardment owing to radiation damage to the HOPG surface.The α_(0) and p_(0,1) yields decrease by 51.5% and 25%,respectively,when the ^(12)C^(2+) beam dose accumulates at 5 C.Using the novel detection system and HOPG target,the α0yield is determined to be 2.68_(-1.69)^(+4.69)×10^(-17/12) C after correcting for the yield loss due to radiation damage.Our result represents the highest sensitivity achieved to date in direct measurements of ^(12)C(12C,α_(0))^(20)Ne.
基金sponsored by the Youth Fund Project of CEA in 2017(QNJJ201702)
文摘In order to add earthquake monitoring methods and develop new method research,the ELF Network for Earthquake Monitoring selected 30 stations in the Capital Circle and the Sichuan-Yunnan region. Finding electromagnetic field background variation is the basis of distinguishing the seismic electromagnetic anomalies. This paper introduces the data acquisition and selection of the Shexian,Anqiu,Lijiang and Dali stations which have recorded for longer time with better data and are located on the similar latitude. Then we use the natural source electromagnetic field's auto-power spectrum to express the intensity of the electromagnetic field. By using power spectral data of many frequencies in the observation frequency band,after the data pre-processing and sliding average noising,the background variation of extremely low frequency stations and the range ability were acquired.Taking the Baoshan M5. 1 earthquake on October 30,2015 and Dali M5. 0 earthquake on May 18,2016 as examples,the authors analyzed the earthquake electromagnetic anomaly characteristic of ELF stations around the earthquakes.
文摘光伏新能源发电系统的电能产出受到多种外部条件的影响,包括光照强度、环境温度变化以及局部阴影的遮挡效应,容易导致其MPP(Maximum Power Point,最大功率点)发生漂移,从而难以快速准确地跟踪功率点变化。在低碳背景下,计算发电系统Boost电路中的占空比、输出负载、电感和电容参数,引入蚁群算法对Boost电路参数进行优化,增强搜索过程的多样性和探索性。采用随机化步长,通过模糊控制器,实现对最大功率点跟踪控制。仿真结果表明,当直流母线电压存在扰动时,所提方法可以迅速作出反应,并将电压恢复到正常水平;当光照强度骤减后,仅需要0.9 s左右的时间就可以稳定在最大功率点附近。
