A method of measuring the tritium in seawater based on electrolytic enrichment and ultra-low background liquid scintillation counting techniques was established.The different factors influencing the detection limit we...A method of measuring the tritium in seawater based on electrolytic enrichment and ultra-low background liquid scintillation counting techniques was established.The different factors influencing the detection limit were studied,including the counting time,the electrolytic volume of the seawater samples,the selection of background water,scintillation solution and their ratio.After optimizing the parameters and electrolyzing 350 mL volume of samples,the detection limit of the method was as low as 0.10 Bq/L.In order to test the optimization of system for this method,of the 84 seawater samples collected from the Arctic Ocean we measured,92%were above the detection limit(the activity of this samples ranged from 0.10 Bq/L to 1.44 Bq/L with an average of(0.30±0.24)Bq/L).In future research,if we need to accurately measure the tritium activity in samples,the volume of the electrolytic samples will be increased to further reduce the minimum detectable activity.展开更多
Purpose Among the several methods to measure ^(222)Rn in water,the liquid scintillation counting(LSC)technique is one of the most sensitive and widely used when analysing non-saline waters by liquid extraction,providi...Purpose Among the several methods to measure ^(222)Rn in water,the liquid scintillation counting(LSC)technique is one of the most sensitive and widely used when analysing non-saline waters by liquid extraction,providing excellent accuracy,precision and low-level detection limits.When using the liquid scintillation counter Tri-Carb 3170 TR/SL(Perkin-Elmer)it is not possible to make an automatic determination of the alpha/beta discrimination parameter,being necessary to evaluate the pulse decay discriminator(PDD)value manually to the ^(222)Rn determination.In this work,we describe the steps to perform the calibration of that type of equipment.Methods The method consists in the preparation of standard samples from a ^(226)Ra certified standard solution and the adjustment of the PDD value by hand until the percentage of alpha events reaches a plateau of a near-constant fraction of total events.The process consists in taking several measures between PDD 80 and 200 with 15 min counting time each.Within the plateau,the alpha/beta ratio was used to determine the plateau final range as well as the optimum PDD value.After that,the calibration standards and blanks were measured and the region of interest(ROI)was established by finding the maximum value for the figure of merit(FOM)in the upper and lower limits.Results The optimal PDD value of 148 was established by the alpha/beta ratio,and after that,it was possible to measure ^(226)Ra standards to perform the calibration.An efficiency of(9.758±0.035)×1^(0-1) was obtained.In routine measurements,a detection limit of about 0.50 Bq L^(-1) is achieved for a 120 min counting time.To evaluate the uncertainty budget,the uncertainties of the net count rate,the efficiency,the sample amount and the decay correction factor were considered.Conclusions A method was developed for the calibration of LSC Tri-Carb 3170 TR/SL with the optimization of the PDD using a ^(226)Ra standard solution.The acquisition to obtain the plot of the variation of the events fraction in each window(alpha and beta)in function of PDD allowed to evaluate a plateau where the fraction of events was at a minimum.Afterwards,it was possible to measure the set of ^(226)Ra standards after the equilibrium with ^(222)Rn and determine the efficiency for ^(222)Rn with a detection limit of about 0.50 Bq L^(-1) in routine analyses.展开更多
Background Tritium(3H)emits low-energy beta particles with a maximum energy of 18.6 keV.Liquid scintillation counting technique(LSC)is mostly used for the detection and quantification of low-energy emitters like H-3.T...Background Tritium(3H)emits low-energy beta particles with a maximum energy of 18.6 keV.Liquid scintillation counting technique(LSC)is mostly used for the detection and quantification of low-energy emitters like H-3.The most widely used method to determine the level of tritium in humans is testing urine.Method In this study,tritium activity concentrations in urine samples taken from 20 adults were measured.Their ages range from 23 to 50.Eight of them are female,and others are male.The tritium activity concentrations in urine samples were determined with two different methods.Also,two standard samples were used to compare urine samples.Result The efficiency values were found with two different methods(26.07%for the first method and 26.14%for the second method).According to the comparison results,the tritium concentration differences between these methods were found in a negligible level for urine samples and in an acceptable level for standard samples.Conclusion The tritium activity concentrations in urine and standard samples were calculated using two different methods.According to the comparison results,these two methods can be used for determination of tritium concentrations in urine samples.展开更多
High-precision vertex and energy reconstruction are crucial for large liquid scintillator detectors such as that at the Jiangmen Underground Neutrino Observatory(JUNO),especially for the determination of neutrino mass...High-precision vertex and energy reconstruction are crucial for large liquid scintillator detectors such as that at the Jiangmen Underground Neutrino Observatory(JUNO),especially for the determination of neutrino mass ordering by analyzing the energy spectrum of reactor neutrinos.This paper presents a data-driven method to obtain a more realistic and accurate expected PMT response of positron events in JUNO and develops a simultaneous vertex and energy reconstruction method that combines the charge and time information of PMTs.For the JUNO detector,the impact of the vertex inaccuracy on the energy resolution is approximately 0.6%.展开更多
Large-volume liquid scintillator detectors with ultra-low background levels have been widely used to study neutrino physics and search for dark matter.Event vertex and event time are not only useful for event selectio...Large-volume liquid scintillator detectors with ultra-low background levels have been widely used to study neutrino physics and search for dark matter.Event vertex and event time are not only useful for event selection but also essential for the reconstruction of event energy.In this study,four event vertex and event time reconstruction algorithms using charge and time information collected by photomultiplier tubes were analyzed comprehensively.The effects of photomultiplier tube properties were also investigated.The results indicate that the transit time spread is the main effect degrading the vertex reconstruction,while the effect of dark noise is limited.In addition,when the event is close to the detector boundary,the charge information provides better performance for vertex reconstruction than the time information.展开更多
The precise vertex reconstruction for large liquid scintillator detectors is essential.A novel machine learning-based method was successfully developed to reconstruct an event vertex in JUNO.In this study,the performa...The precise vertex reconstruction for large liquid scintillator detectors is essential.A novel machine learning-based method was successfully developed to reconstruct an event vertex in JUNO.In this study,the performance of machine learning-based vertex reconstruction was further improved by optimizing the input images of neural networks.By separating the information of different types of PMTs and adding the information of the second hit of PMTs,the vertex resolution was improved by approximately 9.4% at 1 MeV and 9.8% at 11 MeV.展开更多
In recent years, cooling technology for liquid xenon(LXe) detectors has advanced driven by the development of dark matter(DM) detectors with target mass in the 100–1000 kg range. The next generation of DM detectors b...In recent years, cooling technology for liquid xenon(LXe) detectors has advanced driven by the development of dark matter(DM) detectors with target mass in the 100–1000 kg range. The next generation of DM detectors based on LXe will be in the 50,000 kg(50 t)range requiring more than 1 k W of cooling power. Most of the prior cooling methods become impractical at this level.For cooling a 50 t scale LXe detector, a method is proposed in which liquid nitrogen(LN2) in a small local reservoir cools the xenon gas via a cold finger. The cold finger incorporates a heating unit to provide temperature regulation. The proposed cooling method is simple, reliable, and suitable for the required long-term operation for a rare event search. The device can be easily integrated into present cooling systems, for example the ‘‘Cooling Bus’ ’employed for the Panda X I and II experiments. It is still possible to cool indirectly with no part of the cooling or temperature control system getting in direct contact with the clean xenon in the detector. Also, the cooling device can be mounted at a large distance, i.e., the detector is cooled remotely from a distance of 5–10 m. The method was tested in a laboratory setup at Columbia University to carry out different measurements with a small LXe detector and behaved exactly as predicted.展开更多
Non-vanishing electromagnetic properties of neutrinos have been predicted by many theories beyond the Standard Model, and an enhanced neutrino magnetic moment can have profound implications for fundamental physics. Th...Non-vanishing electromagnetic properties of neutrinos have been predicted by many theories beyond the Standard Model, and an enhanced neutrino magnetic moment can have profound implications for fundamental physics. The XENON1T experiment recently detected an excess of electron recoil events in the 1–7 keV energy range, which can be compatible with solar neutrino magnetic moment interaction at a most probable value of μ_(v) = 2.1 × 10^(-11)μ_(B).However, tritium backgrounds or solar axion interaction in this energy window are equally plausible causes.Upcoming multi-tonne noble liquid detectors will test these scenarios more in depth, but will continue to face similar ambiguity. We report a unique capability of future large liquid scintillator detectors to help resolve the potential neutrino magnetic moment scenario. With O(100) kton·year exposure of liquid scintillator to solar neutrinos, a sensitivity of μ_(v) < 10^(-11)μ_(B) can be reached at an energy threshold greater than 40 keV, where no tritium or solar axion events but only neutrino magnetic moment signal is still present.展开更多
Nucleco is the Sogin Group’s Italian leading company in the sector of radiological services,radioactive waste management,decontamination and reclamation of industrial sites and nuclear power plants.Nucleco is 60%owne...Nucleco is the Sogin Group’s Italian leading company in the sector of radiological services,radioactive waste management,decontamination and reclamation of industrial sites and nuclear power plants.Nucleco is 60%owned by Sogin and 40%by ENEA-National Agency for New Technologies.The waste characterization carried out by Nucleco SpA includes a large variety of radionuclides belonging to the gamma,beta and alpha emitter families.The determination of Uranium and Plutonium isotopes plays a key role in the waste characterization.Nucleco SpA has distinguished itself in characterizations of radioactive waste in complex and nuclear plant matrices.These matrices have large amounts of alpha emitters,in particular isotopes of Uranium,Thorium and Plutonium.A significant presence of U238 results in such a large amount of Th234(and daughters)that interferes with the determination of Pu241.Hence,there is the need of finding a pre-treatment,extraction and subsequent purification technique that would allow Th234 to be detached and thus Pu241 to be determined in complex high-activity matrices.The above elements are extracted using chromatography columns.An isotope of the element to be analyzed,with known activity,is added at the beginning of the process to determine the extraction yield.Before being eluted into the column,the sample undergoes a series of treatments in order to be purified of any interferents.The method developed by Nucleco involves the oxidation of Pu at valence+6 and the subsequent precipitation,in fluorides form,of the elements with valence+4 and+3(i.e.Th234).Pu241 is then measured by LSC(Liquid Scintillation Counting),while the other isotopes are measured by alpha spectrometry after electrodeposition on a metal plate.展开更多
As a unique probe,the precision measurement of pp solar neutrinos is important for studying the sun’s energy mechanism as it enables monitoring the thermodynamic equilibrium and studying neutrino oscillations in the ...As a unique probe,the precision measurement of pp solar neutrinos is important for studying the sun’s energy mechanism as it enables monitoring the thermodynamic equilibrium and studying neutrino oscillations in the vacuum-dominated region.For a large-scale liquid scintillator detector,a bottleneck for pp solar neutrino detection is the pile-up events of intrinsic14C decay.This paper presents a few approaches to discriminating between pp solar neutrinos and ^(14)C pile-up events by considering the differences in their time and spatial distributions.In this study,a Geant4-based Monte Carlo simulation is conducted.Multivariate analysis and deep learning technology are adopted to investigate the capability of ^(14)C pile-up reduction.The BDTG (boosted decision trees with gradient boosting) model and VGG network demonstrate good performance in discriminating pp solar neutrinos and ^(14)C double pile-up events.Under the ^(14)C concentration assumption of 5×10-18g/g,the signal significance can achieve 10.3 and 15.6 using the statistics of only one day.In this case,the signal efficiency for discrimination using the BDTG model while rejecting 99.18% ^(14)C double pile-up events is 51.1%,and that for the case where the VGG network is used while rejecting 99.81%of the ^(14)C double pile-up events is 42.7%.展开更多
Based on some important domestic and international references,the third γ multiplicity measurement equation is derived,but it is different from the results given in current researches.The neutron multiplicity equatio...Based on some important domestic and international references,the third γ multiplicity measurement equation is derived,but it is different from the results given in current researches.The neutron multiplicity equation is deduced in this paper,especially the fourth fast-neutron multiplicity equation based on the liquid scintillation detectors,which is more complex than the other multiplicity equations up to the fourth order.The equations given in this paper can be used to verify the validity and availability of principles for the multiplicity measurement up to the fourth order,and extend the application scopes of the neutron multiplicity measurement,such as correcting the additional measurement value to eliminate influences for dead times.It will be the foundation of nuclear researches,if the higher order multiplicity measurement is important for nuclear materials’control and accountability.展开更多
In accordance with the recommendations of the most recent Directive of Council EURATOM No. 2013/51, which concerns requirements for the protection of the health of the general public with regard to radioactive substan...In accordance with the recommendations of the most recent Directive of Council EURATOM No. 2013/51, which concerns requirements for the protection of the health of the general public with regard to radioactive substances in water intended for human consumption, we are obligated to monitor the level of approximate dose of radioactive substances. The directive indicates two basic isotopes: tritium and radon, which ought to be monitored continuously. Essential are also para-metric values as well as frequency, methods of monitoring of radioactive substances and equipment requirements. Directive states that measurements of content of tritium and radon ought to be taken as well as calculations of approximate dose natural and artificial radionuclides content should be done, apart from tritium, potassium-40, radon and short-living products of radon disintegration. In case if one of radioactive concentrations is over 20% of computational value or concentration of tritium is over parametric value analysis of additional radionuclides is required. A detailed list of radionuclides is presented in appendix No. 3 in the Directive. Laboratory of Nuclear Control Systems and Methods in the Institute of Nuclear Chemistry and Technology (INCT) worked out a Miniature Liquid Scintillation Counter (LCS) [1] [2], within a project titled “New generation of intelligent radiometric devices with cordless transmission of information” (UDA-POIG.01.03.01-14-065/08) co-financed by European Union from the European Regional Development Fund (ERDF). This Miniature Liquid Scintillation Counter may be used as a basic equipment resulting in the above mentioned directive. This article presents results of conducted research based on LCS and comparison of this results with the measurements carried out by Accredited Laboratory for Cali-bration of Dosimetric and Radon Instruments in Central Laboratory for Radiological Protection in Warsaw (CLOR).展开更多
To satisfy the accurate positioning requirement of the calibration source in the Jiangmen Underground Neutrino Observatory, a Tonpilz-type hydrophone with low radioactivity and high electroacoustics is developed.The r...To satisfy the accurate positioning requirement of the calibration source in the Jiangmen Underground Neutrino Observatory, a Tonpilz-type hydrophone with low radioactivity and high electroacoustics is developed.The radioactivity of the proposed hydrophone is strictly controlled by selecting pure raw materials, especially active piezoelectric ceramics. The electroacoustic performance of the hydrophone is improved by making structural optimization. High sensitivity and aimed directivity are achieved using 33-mode piezoelectric ceramic rings arranged in series and improvement in the radiating head of the Tonpilz hydrophone, respectively. All electroacoustic performances are studied through finite element analyses.The simulations indicate that the electroacoustic performances of the hydrophones in linear alkylbenzene-based liquid scintillator can be approximately predicted according to the results in water because their differences caused by two types of acoustic media, water and liquid scintillator, are known. The tests show that the hydrophone prototype can achieve a maximum sensitivity of-209.3dB and a beamwidth of 132.2° at a frequency of 143 kHz.In addition, eight hydrophones only contributed to a background radioactivity level of 26 ± 4 mHz in the neutrino analysis.展开更多
The research on geoneutrinos is a new interdisciplinary subject involving particle experiments and geo-science.Potassium-40(40K)decays contribute roughly to 1/3 of the radiogenic heat of the Earth,which is not yet acc...The research on geoneutrinos is a new interdisciplinary subject involving particle experiments and geo-science.Potassium-40(40K)decays contribute roughly to 1/3 of the radiogenic heat of the Earth,which is not yet accounted for by experimental observation.Solar neutrino experiments with liquid scintillators have observed uranium and thorium geoneutrinos and are the most promising experiments with regard to low-background neutrino detection.In this study,we present the new concept of using liquid-scintillator Cherenkov detectors to detect the neutrino-electron elastic scattering process of 40K geoneutrinos.Liquid-scintillator Cherenkov detectors using a slow liquid scintillator achieve this goal with both energy and direction measurements for charged particles.Given the directionality,we can significantly suppress the dominant intrinsic background originating from solar neutrinos in conventional liquid-scintillator detectors.We simulated the solar-and geo-neutrino scatterings in the slow liquid scintillator detector,and implemented energy and directional reconstructions for the recoiling electrons.We found that 40K geoneutrinos can be detected with three-standard-deviation accuracy in a kiloton-scale detector.展开更多
Introduction The Jiangmen Underground Neutrino Observatory has critical requirements on quality of the liquid scintillator,one of which is long attenuation length.Purpose A system with a height of 3 m is used to preci...Introduction The Jiangmen Underground Neutrino Observatory has critical requirements on quality of the liquid scintillator,one of which is long attenuation length.Purpose A system with a height of 3 m is used to precisely measure the attenuation length of the liquid scintillators.Methods The light generated by a LED is transmitted through an optical fiber.After being focused,filtered and collimated,the light enters the test tube with the liquid scintillator and is detected by the PMT.The stepping motor is controlled by the Labview program to adjust the level of the liquid scintillator,and the emitted light intensity of different liquid levels can be obtained to fit the attenuation length.In addition,the systematic errors have been studied,which includes the measurement error of the emitted light intensity and the error caused by the movement of light spot,and the latter is responded to the non-uniformity of the PMT photocathode.Meanwhile,analytical methods were improved.Results The system can measure the attenuation length stably and a small error was obtained,including statistical error and systematic error(0.69-23.70 m).展开更多
Purpose Liquid scintillator is the target material of neutrino in Jiangmen Underground Neutrino Observatory(JUNO)detector.it is necessary to control the radon at a very low level.Methods In this work,a device was set ...Purpose Liquid scintillator is the target material of neutrino in Jiangmen Underground Neutrino Observatory(JUNO)detector.it is necessary to control the radon at a very low level.Methods In this work,a device was set up to strip the radon from liquid scintillator with high-purity nitrogen bubbling,and the radon carrier nitrogen was collected into radon measurement chamber to measure radon concentration,then the stripping efficiency of radon in liquid scintillator can be measured.Results Under normal temperature and 2L/min gas flow rate,the stripping efficiency of radon in liquid scintillator is 3.85%.Conclusions The preliminary radon stripping results showthat the high-purity nitrogen stripping radon in the liquid scintillator has efficiency,and the device has the ability to measure radon concentration in the liquid scintillator,as well as the stripping device provides a basis for further low concentration radon measurement in the liquid scintillator.展开更多
Purpose Radon is a noble gas,which endangers our health.The liquid scintillator is one of the detector materials used to measure radon in the environment.But there are challenges in measuring radon using a liquid scin...Purpose Radon is a noble gas,which endangers our health.The liquid scintillator is one of the detector materials used to measure radon in the environment.But there are challenges in measuring radon using a liquid scintillator,such as independent manual operation and long measurement periods.Methods and Results We propose a liquid scintillator detector for the rapid measurement of radon,which is composed of a breathable liquid scintillator probe and photomultiplier tube.Cascade decay recognition and pulse shape discrimination(PSD)were used to select radon events.241 Am4(α)and 90Sr(β)source calibration was used to optimize the PSDfigure of merit of the liquid scintillator,and a 232Th(220Rn)diffusion source was used to verify the function of this novel detector for measuring radon.Conclusion The detector had an integrated design for sampling and measurement,which simplified the measurement steps.Thus,this novel liquid scintillator detector demonstrated promise for use in radon-detection systems.展开更多
The Jiangmen Underground Neutrino Observatory(JUNO)is a large liquid scintillator detector designed to explore many topics in fundamental physics.In this study,the potential of searching for proton decay in the p→νK...The Jiangmen Underground Neutrino Observatory(JUNO)is a large liquid scintillator detector designed to explore many topics in fundamental physics.In this study,the potential of searching for proton decay in the p→νK^(+)mode with JUNO is investigated.The kaon and its decay particles feature a clear three-fold coincidence signature that results in a high efficiency for identification.Moreover,the excellent energy resolution of JUNO permits suppression of the sizable background caused by other delayed signals.Based on these advantages,the detection efficiency for the proton decay via p→νK^(+)is 36.9%±4.9%with a background level of 0.2±0.05(syst)±0.2(stat)events after 10 years of data collection.The estimated sensitivity based on 200 kton-years of exposure is 9.6×1033 years,which is competitive with the current best limits on the proton lifetime in this channel and complements the use of different detection technologies.展开更多
Objective:To figure out the source of uncertainty in the determination of ^(14)C activity concentration in urine samples,and to establish a complete expression of analysis results,in order to improve the accuracy of ^...Objective:To figure out the source of uncertainty in the determination of ^(14)C activity concentration in urine samples,and to establish a complete expression of analysis results,in order to improve the accuracy of ^(14)C monitoring method.Methods:Four urine samples of normal people were collected,and wet oxidation method was used in the pretreatment of the samples,then the activity concentration of ^(14)C was determined by liquid scintillation counting(LSC).After the mathematical model was established,the uncertainty components were determined,the standard uncertainty was combined,and the extended uncertainty was calculated.Results:The relative uncertainty of 4 samples was 22.5%,17.0%,17.3%and 18.2%.The activity concentration of urine was(0.32±0.14),(0.60±0.20),(0.86±0.30)and(0.74±0.27)Bq/L,respectively.In the relative uncertainty of 22.5%,17.7%was from sample counting,13.6%from detection efficiency,2.1%from recovery rate,0.58%from sample volume,and 0.01%from sample weight.Conclusions:The main factors affecting the uncertainty include the error or deviation of sample counting,detection efficiency and recovery rate.The error of volume and weight also contributes to the measurement uncertainty.展开更多
China Jinping Underground Laboratory(CJPL)is ideal for studying solar,geo-,and supernova neutrinos.A precise measurement of the cosmic-ray background is essential in proceeding with R&D research for these MeV-scal...China Jinping Underground Laboratory(CJPL)is ideal for studying solar,geo-,and supernova neutrinos.A precise measurement of the cosmic-ray background is essential in proceeding with R&D research for these MeV-scale neutrino experiments.Using a 1-ton prototype detector for the Jinping Neutrino Experiment(JNE),we detected 264 high-energy muon events from a 645.2-day dataset from the first phase of CJPL(CJPL-I),reconstructed their directions,and measured the cosmic-ray muon flux to be (3.53±0.22_stat.±0.07_sys.)×-10^(-10)cm^(-2).The observed angular distributions indicate the leakage of cosmic-ray muon background and agree with simulation data accounting for Jinping mountain's terrain.A survey of muon fluxes at different laboratory locations,considering both those situated under mountains and those down mine shafts,indicates that the flux at the former is generally a factor of (4±2) larger than at the latter,with the same vertical overburden.This study provides a convenient back-of-the-envelope estimation for the muon flux of an underground experiment.展开更多
基金The project sponsored by the Scientific Research Foundation of Third Institute of Oceanography,Ministry of Natural Resources,under contract No.2020012the Join Project of Xiamen Marine Research and Development Institute under contract No.K191301.
文摘A method of measuring the tritium in seawater based on electrolytic enrichment and ultra-low background liquid scintillation counting techniques was established.The different factors influencing the detection limit were studied,including the counting time,the electrolytic volume of the seawater samples,the selection of background water,scintillation solution and their ratio.After optimizing the parameters and electrolyzing 350 mL volume of samples,the detection limit of the method was as low as 0.10 Bq/L.In order to test the optimization of system for this method,of the 84 seawater samples collected from the Arctic Ocean we measured,92%were above the detection limit(the activity of this samples ranged from 0.10 Bq/L to 1.44 Bq/L with an average of(0.30±0.24)Bq/L).In future research,if we need to accurately measure the tritium activity in samples,the volume of the electrolytic samples will be increased to further reduce the minimum detectable activity.
基金the Fundacao para a Ciencia e Tecnologia(FCT)support through the UID/Multi/04349/2013 projectfunding provided by FCTIFCCN(b-on).
文摘Purpose Among the several methods to measure ^(222)Rn in water,the liquid scintillation counting(LSC)technique is one of the most sensitive and widely used when analysing non-saline waters by liquid extraction,providing excellent accuracy,precision and low-level detection limits.When using the liquid scintillation counter Tri-Carb 3170 TR/SL(Perkin-Elmer)it is not possible to make an automatic determination of the alpha/beta discrimination parameter,being necessary to evaluate the pulse decay discriminator(PDD)value manually to the ^(222)Rn determination.In this work,we describe the steps to perform the calibration of that type of equipment.Methods The method consists in the preparation of standard samples from a ^(226)Ra certified standard solution and the adjustment of the PDD value by hand until the percentage of alpha events reaches a plateau of a near-constant fraction of total events.The process consists in taking several measures between PDD 80 and 200 with 15 min counting time each.Within the plateau,the alpha/beta ratio was used to determine the plateau final range as well as the optimum PDD value.After that,the calibration standards and blanks were measured and the region of interest(ROI)was established by finding the maximum value for the figure of merit(FOM)in the upper and lower limits.Results The optimal PDD value of 148 was established by the alpha/beta ratio,and after that,it was possible to measure ^(226)Ra standards to perform the calibration.An efficiency of(9.758±0.035)×1^(0-1) was obtained.In routine measurements,a detection limit of about 0.50 Bq L^(-1) is achieved for a 120 min counting time.To evaluate the uncertainty budget,the uncertainties of the net count rate,the efficiency,the sample amount and the decay correction factor were considered.Conclusions A method was developed for the calibration of LSC Tri-Carb 3170 TR/SL with the optimization of the PDD using a ^(226)Ra standard solution.The acquisition to obtain the plot of the variation of the events fraction in each window(alpha and beta)in function of PDD allowed to evaluate a plateau where the fraction of events was at a minimum.Afterwards,it was possible to measure the set of ^(226)Ra standards after the equilibrium with ^(222)Rn and determine the efficiency for ^(222)Rn with a detection limit of about 0.50 Bq L^(-1) in routine analyses.
基金This study was supported by the Scientific and Technological Research Council of Turkey(TÜB˙ITAK)under the Project No.214S221.
文摘Background Tritium(3H)emits low-energy beta particles with a maximum energy of 18.6 keV.Liquid scintillation counting technique(LSC)is mostly used for the detection and quantification of low-energy emitters like H-3.The most widely used method to determine the level of tritium in humans is testing urine.Method In this study,tritium activity concentrations in urine samples taken from 20 adults were measured.Their ages range from 23 to 50.Eight of them are female,and others are male.The tritium activity concentrations in urine samples were determined with two different methods.Also,two standard samples were used to compare urine samples.Result The efficiency values were found with two different methods(26.07%for the first method and 26.14%for the second method).According to the comparison results,the tritium concentration differences between these methods were found in a negligible level for urine samples and in an acceptable level for standard samples.Conclusion The tritium activity concentrations in urine and standard samples were calculated using two different methods.According to the comparison results,these two methods can be used for determination of tritium concentrations in urine samples.
基金supported by the National Key R&D Program of China(No.2018YFA0404100)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.12175257)+1 种基金the National Natural Science Foundation of China(No.12175257)the Science Foundation of High-Level Talents of Wuyi University(No.2021AL027).
文摘High-precision vertex and energy reconstruction are crucial for large liquid scintillator detectors such as that at the Jiangmen Underground Neutrino Observatory(JUNO),especially for the determination of neutrino mass ordering by analyzing the energy spectrum of reactor neutrinos.This paper presents a data-driven method to obtain a more realistic and accurate expected PMT response of positron events in JUNO and develops a simultaneous vertex and energy reconstruction method that combines the charge and time information of PMTs.For the JUNO detector,the impact of the vertex inaccuracy on the energy resolution is approximately 0.6%.
基金supported by the National Natural Science Foundation of China(Nos.11805294 and 11975021)the China Postdoctoral Science Foundation(2018M631013),the Strategic Priority Research Program of Chinese Academy of Sciences(XDA10010900)+1 种基金the Fundamental Research Funds for the Central Universities,Sun Yatsen University(19lgpy268)in part by the CAS Center for Excellence in Particle Physics(CCEPP).
文摘Large-volume liquid scintillator detectors with ultra-low background levels have been widely used to study neutrino physics and search for dark matter.Event vertex and event time are not only useful for event selection but also essential for the reconstruction of event energy.In this study,four event vertex and event time reconstruction algorithms using charge and time information collected by photomultiplier tubes were analyzed comprehensively.The effects of photomultiplier tube properties were also investigated.The results indicate that the transit time spread is the main effect degrading the vertex reconstruction,while the effect of dark noise is limited.In addition,when the event is close to the detector boundary,the charge information provides better performance for vertex reconstruction than the time information.
基金supported by the National Natural Science Foundation of China(Nos.11975021,12175257,12175321,11675275,and U1932101)the Guangdong Basic and Applied Basic Research Foundation(No.2021A1515012039)+3 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA10010900)the National College Students Science and Technology Innovation Projectthe Undergraduate Base Scientific Research Project of Sun Yat-sen Universitythe CAS Center for Excellence in Particle Physics(CCEPP).
文摘The precise vertex reconstruction for large liquid scintillator detectors is essential.A novel machine learning-based method was successfully developed to reconstruct an event vertex in JUNO.In this study,the performance of machine learning-based vertex reconstruction was further improved by optimizing the input images of neural networks.By separating the information of different types of PMTs and adding the information of the second hit of PMTs,the vertex resolution was improved by approximately 9.4% at 1 MeV and 9.8% at 11 MeV.
基金the Ministry of Science and Technology of China(No.2016YFA0400301)the grants for the XENON Dark Matter Project。
文摘In recent years, cooling technology for liquid xenon(LXe) detectors has advanced driven by the development of dark matter(DM) detectors with target mass in the 100–1000 kg range. The next generation of DM detectors based on LXe will be in the 50,000 kg(50 t)range requiring more than 1 k W of cooling power. Most of the prior cooling methods become impractical at this level.For cooling a 50 t scale LXe detector, a method is proposed in which liquid nitrogen(LN2) in a small local reservoir cools the xenon gas via a cold finger. The cold finger incorporates a heating unit to provide temperature regulation. The proposed cooling method is simple, reliable, and suitable for the required long-term operation for a rare event search. The device can be easily integrated into present cooling systems, for example the ‘‘Cooling Bus’ ’employed for the Panda X I and II experiments. It is still possible to cool indirectly with no part of the cooling or temperature control system getting in direct contact with the clean xenon in the detector. Also, the cooling device can be mounted at a large distance, i.e., the detector is cooled remotely from a distance of 5–10 m. The method was tested in a laboratory setup at Columbia University to carry out different measurements with a small LXe detector and behaved exactly as predicted.
基金Supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDA10010800)the Double First Class Start-up Fund (WF220442603) provided by Shanghai Jiao Tong Universitysupport from the CAS Center for Excellence in Particle Physics (CCEPP)。
文摘Non-vanishing electromagnetic properties of neutrinos have been predicted by many theories beyond the Standard Model, and an enhanced neutrino magnetic moment can have profound implications for fundamental physics. The XENON1T experiment recently detected an excess of electron recoil events in the 1–7 keV energy range, which can be compatible with solar neutrino magnetic moment interaction at a most probable value of μ_(v) = 2.1 × 10^(-11)μ_(B).However, tritium backgrounds or solar axion interaction in this energy window are equally plausible causes.Upcoming multi-tonne noble liquid detectors will test these scenarios more in depth, but will continue to face similar ambiguity. We report a unique capability of future large liquid scintillator detectors to help resolve the potential neutrino magnetic moment scenario. With O(100) kton·year exposure of liquid scintillator to solar neutrinos, a sensitivity of μ_(v) < 10^(-11)μ_(B) can be reached at an energy threshold greater than 40 keV, where no tritium or solar axion events but only neutrino magnetic moment signal is still present.
文摘Nucleco is the Sogin Group’s Italian leading company in the sector of radiological services,radioactive waste management,decontamination and reclamation of industrial sites and nuclear power plants.Nucleco is 60%owned by Sogin and 40%by ENEA-National Agency for New Technologies.The waste characterization carried out by Nucleco SpA includes a large variety of radionuclides belonging to the gamma,beta and alpha emitter families.The determination of Uranium and Plutonium isotopes plays a key role in the waste characterization.Nucleco SpA has distinguished itself in characterizations of radioactive waste in complex and nuclear plant matrices.These matrices have large amounts of alpha emitters,in particular isotopes of Uranium,Thorium and Plutonium.A significant presence of U238 results in such a large amount of Th234(and daughters)that interferes with the determination of Pu241.Hence,there is the need of finding a pre-treatment,extraction and subsequent purification technique that would allow Th234 to be detached and thus Pu241 to be determined in complex high-activity matrices.The above elements are extracted using chromatography columns.An isotope of the element to be analyzed,with known activity,is added at the beginning of the process to determine the extraction yield.Before being eluted into the column,the sample undergoes a series of treatments in order to be purified of any interferents.The method developed by Nucleco involves the oxidation of Pu at valence+6 and the subsequent precipitation,in fluorides form,of the elements with valence+4 and+3(i.e.Th234).Pu241 is then measured by LSC(Liquid Scintillation Counting),while the other isotopes are measured by alpha spectrometry after electrodeposition on a metal plate.
基金supported by National Natural Science Foundation of China(No.12005044)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA10011200)Guangxi Science and Technology Program(No.GuiKeAD21220037).
文摘As a unique probe,the precision measurement of pp solar neutrinos is important for studying the sun’s energy mechanism as it enables monitoring the thermodynamic equilibrium and studying neutrino oscillations in the vacuum-dominated region.For a large-scale liquid scintillator detector,a bottleneck for pp solar neutrino detection is the pile-up events of intrinsic14C decay.This paper presents a few approaches to discriminating between pp solar neutrinos and ^(14)C pile-up events by considering the differences in their time and spatial distributions.In this study,a Geant4-based Monte Carlo simulation is conducted.Multivariate analysis and deep learning technology are adopted to investigate the capability of ^(14)C pile-up reduction.The BDTG (boosted decision trees with gradient boosting) model and VGG network demonstrate good performance in discriminating pp solar neutrinos and ^(14)C double pile-up events.Under the ^(14)C concentration assumption of 5×10-18g/g,the signal significance can achieve 10.3 and 15.6 using the statistics of only one day.In this case,the signal efficiency for discrimination using the BDTG model while rejecting 99.18% ^(14)C double pile-up events is 51.1%,and that for the case where the VGG network is used while rejecting 99.81%of the ^(14)C double pile-up events is 42.7%.
文摘Based on some important domestic and international references,the third γ multiplicity measurement equation is derived,but it is different from the results given in current researches.The neutron multiplicity equation is deduced in this paper,especially the fourth fast-neutron multiplicity equation based on the liquid scintillation detectors,which is more complex than the other multiplicity equations up to the fourth order.The equations given in this paper can be used to verify the validity and availability of principles for the multiplicity measurement up to the fourth order,and extend the application scopes of the neutron multiplicity measurement,such as correcting the additional measurement value to eliminate influences for dead times.It will be the foundation of nuclear researches,if the higher order multiplicity measurement is important for nuclear materials’control and accountability.
基金The work was realized in the frame of an international project co-funded-Ministry of Science and Higher Education Republic of Poland-“Development of dosimetry methods and safety of radiation and nuclear facilities”,within the framework of the project“Global Threat Reduction Initiative”based on contract No.212971-Task Order 38.
文摘In accordance with the recommendations of the most recent Directive of Council EURATOM No. 2013/51, which concerns requirements for the protection of the health of the general public with regard to radioactive substances in water intended for human consumption, we are obligated to monitor the level of approximate dose of radioactive substances. The directive indicates two basic isotopes: tritium and radon, which ought to be monitored continuously. Essential are also para-metric values as well as frequency, methods of monitoring of radioactive substances and equipment requirements. Directive states that measurements of content of tritium and radon ought to be taken as well as calculations of approximate dose natural and artificial radionuclides content should be done, apart from tritium, potassium-40, radon and short-living products of radon disintegration. In case if one of radioactive concentrations is over 20% of computational value or concentration of tritium is over parametric value analysis of additional radionuclides is required. A detailed list of radionuclides is presented in appendix No. 3 in the Directive. Laboratory of Nuclear Control Systems and Methods in the Institute of Nuclear Chemistry and Technology (INCT) worked out a Miniature Liquid Scintillation Counter (LCS) [1] [2], within a project titled “New generation of intelligent radiometric devices with cordless transmission of information” (UDA-POIG.01.03.01-14-065/08) co-financed by European Union from the European Regional Development Fund (ERDF). This Miniature Liquid Scintillation Counter may be used as a basic equipment resulting in the above mentioned directive. This article presents results of conducted research based on LCS and comparison of this results with the measurements carried out by Accredited Laboratory for Cali-bration of Dosimetric and Radon Instruments in Central Laboratory for Radiological Protection in Warsaw (CLOR).
基金supported by the“trategic Priority Research Program”of the Chinese Academy of Sciences(No.XDA10010800)the National Natural Science Foundation of China(No.12074318)。
文摘To satisfy the accurate positioning requirement of the calibration source in the Jiangmen Underground Neutrino Observatory, a Tonpilz-type hydrophone with low radioactivity and high electroacoustics is developed.The radioactivity of the proposed hydrophone is strictly controlled by selecting pure raw materials, especially active piezoelectric ceramics. The electroacoustic performance of the hydrophone is improved by making structural optimization. High sensitivity and aimed directivity are achieved using 33-mode piezoelectric ceramic rings arranged in series and improvement in the radiating head of the Tonpilz hydrophone, respectively. All electroacoustic performances are studied through finite element analyses.The simulations indicate that the electroacoustic performances of the hydrophones in linear alkylbenzene-based liquid scintillator can be approximately predicted according to the results in water because their differences caused by two types of acoustic media, water and liquid scintillator, are known. The tests show that the hydrophone prototype can achieve a maximum sensitivity of-209.3dB and a beamwidth of 132.2° at a frequency of 143 kHz.In addition, eight hydrophones only contributed to a background radioactivity level of 26 ± 4 mHz in the neutrino analysis.
基金Supported in part by the National Natural Science Foundation of China(11620101004,11235006,11475093)the Ministry of Science and Technology of China(2018YFA0404102)+1 种基金the Key Laboratory of Particle&Radiation Imaging(Tsinghua University)the CAS Center for Excellence in Particle Physics(CCEPP)
文摘The research on geoneutrinos is a new interdisciplinary subject involving particle experiments and geo-science.Potassium-40(40K)decays contribute roughly to 1/3 of the radiogenic heat of the Earth,which is not yet accounted for by experimental observation.Solar neutrino experiments with liquid scintillators have observed uranium and thorium geoneutrinos and are the most promising experiments with regard to low-background neutrino detection.In this study,we present the new concept of using liquid-scintillator Cherenkov detectors to detect the neutrino-electron elastic scattering process of 40K geoneutrinos.Liquid-scintillator Cherenkov detectors using a slow liquid scintillator achieve this goal with both energy and direction measurements for charged particles.Given the directionality,we can significantly suppress the dominant intrinsic background originating from solar neutrinos in conventional liquid-scintillator detectors.We simulated the solar-and geo-neutrino scatterings in the slow liquid scintillator detector,and implemented energy and directional reconstructions for the recoiling electrons.We found that 40K geoneutrinos can be detected with three-standard-deviation accuracy in a kiloton-scale detector.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(XDA10010500)National Natural Science Foundation of China(11390384).
文摘Introduction The Jiangmen Underground Neutrino Observatory has critical requirements on quality of the liquid scintillator,one of which is long attenuation length.Purpose A system with a height of 3 m is used to precisely measure the attenuation length of the liquid scintillators.Methods The light generated by a LED is transmitted through an optical fiber.After being focused,filtered and collimated,the light enters the test tube with the liquid scintillator and is detected by the PMT.The stepping motor is controlled by the Labview program to adjust the level of the liquid scintillator,and the emitted light intensity of different liquid levels can be obtained to fit the attenuation length.In addition,the systematic errors have been studied,which includes the measurement error of the emitted light intensity and the error caused by the movement of light spot,and the latter is responded to the non-uniformity of the PMT photocathode.Meanwhile,analytical methods were improved.Results The system can measure the attenuation length stably and a small error was obtained,including statistical error and systematic error(0.69-23.70 m).
文摘Purpose Liquid scintillator is the target material of neutrino in Jiangmen Underground Neutrino Observatory(JUNO)detector.it is necessary to control the radon at a very low level.Methods In this work,a device was set up to strip the radon from liquid scintillator with high-purity nitrogen bubbling,and the radon carrier nitrogen was collected into radon measurement chamber to measure radon concentration,then the stripping efficiency of radon in liquid scintillator can be measured.Results Under normal temperature and 2L/min gas flow rate,the stripping efficiency of radon in liquid scintillator is 3.85%.Conclusions The preliminary radon stripping results showthat the high-purity nitrogen stripping radon in the liquid scintillator has efficiency,and the device has the ability to measure radon concentration in the liquid scintillator,as well as the stripping device provides a basis for further low concentration radon measurement in the liquid scintillator.
基金supported by the National Natural Science Foundation of China(11775252).
文摘Purpose Radon is a noble gas,which endangers our health.The liquid scintillator is one of the detector materials used to measure radon in the environment.But there are challenges in measuring radon using a liquid scintillator,such as independent manual operation and long measurement periods.Methods and Results We propose a liquid scintillator detector for the rapid measurement of radon,which is composed of a breathable liquid scintillator probe and photomultiplier tube.Cascade decay recognition and pulse shape discrimination(PSD)were used to select radon events.241 Am4(α)and 90Sr(β)source calibration was used to optimize the PSDfigure of merit of the liquid scintillator,and a 232Th(220Rn)diffusion source was used to verify the function of this novel detector for measuring radon.Conclusion The detector had an integrated design for sampling and measurement,which simplified the measurement steps.Thus,this novel liquid scintillator detector demonstrated promise for use in radon-detection systems.
基金supported by the Chinese Academy of Sciencesthe National Key R&D Program of China+22 种基金the CAS Center for Excellence in Particle PhysicsWuyi Universitythe Tsung-Dao Lee Institute of Shanghai Jiao Tong University in Chinathe Institut National de Physique Nucléaire et de Physique de Particules (IN2P3) in Francethe Istituto Nazionale di Fisica Nucleare (INFN) in Italythe Italian-Chinese collaborative research program MAECI-NSFCthe Fond de la Recherche Scientifique (F.R.S-FNRS)FWO under the "Excellence of Science-EOS" in Belgiumthe Conselho Nacional de Desenvolvimento Científico e Tecnològico in Brazilthe Agencia Nacional de Investigacion y Desarrollo in Chilethe Charles University Research Centrethe Ministry of Education,Youth,and Sports in Czech Republicthe Deutsche Forschungsgemeinschaft (DFG)the Helmholtz Associationthe Cluster of Excellence PRISMA+ in Germanythe Joint Institute of Nuclear Research (JINR)Lomonosov Moscow State University in Russiathe joint Russian Science Foundation (RSF)National Natural Science Foundation of China (NSFC) research programthe MOST and MOE in Taiwan,Chinathe Chulalongkorn UniversitySuranaree University of Technology in Thailandthe University of California at Irvine in USA
文摘The Jiangmen Underground Neutrino Observatory(JUNO)is a large liquid scintillator detector designed to explore many topics in fundamental physics.In this study,the potential of searching for proton decay in the p→νK^(+)mode with JUNO is investigated.The kaon and its decay particles feature a clear three-fold coincidence signature that results in a high efficiency for identification.Moreover,the excellent energy resolution of JUNO permits suppression of the sizable background caused by other delayed signals.Based on these advantages,the detection efficiency for the proton decay via p→νK^(+)is 36.9%±4.9%with a background level of 0.2±0.05(syst)±0.2(stat)events after 10 years of data collection.The estimated sensitivity based on 200 kton-years of exposure is 9.6×1033 years,which is competitive with the current best limits on the proton lifetime in this channel and complements the use of different detection technologies.
基金supported by ERAN I-21-18,Key Program of Tianjin Municipal Natural Science Foundation(19JCZDJC40500)Key Program of National Center for Occupational Safety and Health(2021-ZD-06).
文摘Objective:To figure out the source of uncertainty in the determination of ^(14)C activity concentration in urine samples,and to establish a complete expression of analysis results,in order to improve the accuracy of ^(14)C monitoring method.Methods:Four urine samples of normal people were collected,and wet oxidation method was used in the pretreatment of the samples,then the activity concentration of ^(14)C was determined by liquid scintillation counting(LSC).After the mathematical model was established,the uncertainty components were determined,the standard uncertainty was combined,and the extended uncertainty was calculated.Results:The relative uncertainty of 4 samples was 22.5%,17.0%,17.3%and 18.2%.The activity concentration of urine was(0.32±0.14),(0.60±0.20),(0.86±0.30)and(0.74±0.27)Bq/L,respectively.In the relative uncertainty of 22.5%,17.7%was from sample counting,13.6%from detection efficiency,2.1%from recovery rate,0.58%from sample volume,and 0.01%from sample weight.Conclusions:The main factors affecting the uncertainty include the error or deviation of sample counting,detection efficiency and recovery rate.The error of volume and weight also contributes to the measurement uncertainty.
基金Supported in part by the National Natural Science Foundation of China(11620101004,11475093)the Key Laboratory of Particle&Radiation Imaging(Tsinghua University,the CAS Center for Excellence in Particle Physics(CCEPP),and Guangdong Basic and Applied Basic Research Foundation(2019A1515012216)Portion of this work performed at Brookhaven National Laboratory is supponted in part by the United States Department of Energy(DE-SC0012704)。
文摘China Jinping Underground Laboratory(CJPL)is ideal for studying solar,geo-,and supernova neutrinos.A precise measurement of the cosmic-ray background is essential in proceeding with R&D research for these MeV-scale neutrino experiments.Using a 1-ton prototype detector for the Jinping Neutrino Experiment(JNE),we detected 264 high-energy muon events from a 645.2-day dataset from the first phase of CJPL(CJPL-I),reconstructed their directions,and measured the cosmic-ray muon flux to be (3.53±0.22_stat.±0.07_sys.)×-10^(-10)cm^(-2).The observed angular distributions indicate the leakage of cosmic-ray muon background and agree with simulation data accounting for Jinping mountain's terrain.A survey of muon fluxes at different laboratory locations,considering both those situated under mountains and those down mine shafts,indicates that the flux at the former is generally a factor of (4±2) larger than at the latter,with the same vertical overburden.This study provides a convenient back-of-the-envelope estimation for the muon flux of an underground experiment.
