The neutron-induced total cross sections of natural lead have been measured in a wide energy range(0.3 eV-20 MeV)on the back-streaming white neutron beamline(Back-n)at the China Spallation Neutron Source.Neutron energ...The neutron-induced total cross sections of natural lead have been measured in a wide energy range(0.3 eV-20 MeV)on the back-streaming white neutron beamline(Back-n)at the China Spallation Neutron Source.Neutron energy was determined by the neutron total cross-section spectrometer using the time-of-flight technique.A fast multi-cell fission chamber was used as the neutron detector,and a 10-mm-thick high-purity natural lead sample was employed for the neutron transmission measurements.The on-beam background was determined using Co,In,Ag,and Cd filters.The excitation function of ^(nat)Pb(n,tot)reaction below 20 MeV was calculated using the TALYS-1.96 nuclear-reaction modeling program.The present results were compared with previous results,the evaluated data available in the five major evaluated nuclear data libraries(i.e.,ENDF/B-VIII.0,JEFF-3.3,JENDL-5,CENDL-3.2,and BROND-3.1),and the theoretical calculation curve.Good agreement was found between the new results and those of previous experiments and with the theoretical curves in the corresponding region.This measurement obtained the neutron total cross section of natural lead with good accuracy over a wide energy range and added experimental data in the resonance energy range.This provides more reliable experimental data for nuclear engineering design and nuclear data evaluation of lead.展开更多
This study investigates the effects of displacement damage on the dark signal of a pinned photodiode CMOS image sensor(CIS)following irradiation with back-streaming white neutrons from white neutron sources at the Chi...This study investigates the effects of displacement damage on the dark signal of a pinned photodiode CMOS image sensor(CIS)following irradiation with back-streaming white neutrons from white neutron sources at the China spallation neutron source(CSNS)and Xi'an pulsed reactor(XAPR).The mean dark signal,dark signal non-uniformity(DSNU),dark signal distribution,and hot pixels of the CIS were compared between the CSNS back-n and XAPR neutron irradiations.The nonionizing energy loss and energy distribution of primary knock-on atoms in silicon,induced by neutrons,were calculated using the open-source package Geant4.An analysis combining experimental and simulation results showed a noticeable proportionality between the increase in the mean dark signal and the displacement damage dose(DDD).Additionally,neutron energies influence DSNU,dark signal distribution,and hot pixels.High neutron energies at the same DDD level may lead to pronounced dark signal non-uniformity and elevated hot pixel values.展开更多
The back-streaming white-neutron beamline(Back-n)of the China Spallation Neutron Source is an essential neutronresearch platform built for the study of nuclear data,neutron physics,and neutron applications.Many types ...The back-streaming white-neutron beamline(Back-n)of the China Spallation Neutron Source is an essential neutronresearch platform built for the study of nuclear data,neutron physics,and neutron applications.Many types of cross-sectional neutron-reaction measurements have been performed at Back-n since early 2018.These measurements have shown that a significant number of gamma rays can be transmitted to the experimental stations of Back-n along with the neutron beam.These gamma rays,commonly referred to as in-beam gamma rays,can induce a non-negligible experimental background in neutron-reaction measurements.Studying the characteristics of in-beam gamma rays is important for understanding the experimental background.However,measuring in-beam gamma rays is challenging because most gamma-ray detectors are sensitive to neutrons;thus,discriminating between neutron-induced signals and those from in-beam gamma rays is difficult.In this study,we propose the use of the black resonance filter method and a CeBr_(3) scintillation detector to measure the characteristics of the in-beam gamma rays of Back-n.Four types of black resonance filters,^(181)Ta,^(59)Co,^(nat)Ag,and^(nat)Cd,were used in this measurement.The time-of-flight(TOF)technique was used to select the detector signals remaining in the absorption region of the TOF spectra,which were mainly induced by in-beam gamma rays.The energy distribution and flux of the in-beam gamma rays of Back-n were determined by analyzing the deposited energy spectra of the CeBr_(3) scintillation detector and using Monte Carlo simulations.Based on the results of this study,the background contributions from in-beam gamma rays in neutron-reaction measurements at Back-n can be reasonably evaluated,which is beneficial for enhancing both the experimental methodology and data analysis.展开更多
To verify the performance of the neutron total cross-sectional spectrometer, the neutron total cross section of carbon is initially measured in the energy range of 1 eV to 20 MeV using the time-of-flight method. The m...To verify the performance of the neutron total cross-sectional spectrometer, the neutron total cross section of carbon is initially measured in the energy range of 1 eV to 20 MeV using the time-of-flight method. The measurement is performed at the Back-n white neutron source with a 76-m time-of-flight path using the China Spallation Neutron Source. A multilayer fast fission chamber with 235U and 238U is employed as the neutron detector. The diameter and thickness of the natural graphite sample are 70 mm and 40 mm, respectively. Signal waveforms are collected using a data acquisition system. Off-line data processing was used to obtain the neutron time-of-flight spectra and transmissions. The uncertainty of the counting statistics is generally approximately 3% for each bin in the energy range of 1–20 MeV. It is determined that the results for the neutron total cross section of carbon obtained using ^235U cells are in good agreement with the results obtained using 238U cells within limits of statistical uncertainty. Moreover, the measured total cross sections show good agreement with the broadening evaluated data.展开更多
The neutron capture cross section of 197 Au was measured using the time-of-flight(TOF)technique at the Back-n facility of the China Spallation Neutron Source(CSNS)in the 1 eV to 100 keV range.Prompt c-rays originating...The neutron capture cross section of 197 Au was measured using the time-of-flight(TOF)technique at the Back-n facility of the China Spallation Neutron Source(CSNS)in the 1 eV to 100 keV range.Prompt c-rays originating from neutron-induced capture events were detected by four C_(6)D_(6) liquid scintillator detectors.Pulse height weighting technology(PHWT)was used to analyze the data.The results are in good agreement with ENDF/B-VIII.0,CENDL-3.1,and other evaluated libraries in the resonance region,and in agreement with both n TOF and GELINA experimental data in the 5–100 keV range.Finally,the resonance peaks in the energy range from 1eV to 1 keV were fitted by the SAMMY R-matrix code.展开更多
The ^(232)Th(n,f)cross section is very important in basic nuclear physics and applications based on the Th/U fuel cycle.Using the time-of-flight method and a multi-cell fast-fission ionization chamber,a novel measurem...The ^(232)Th(n,f)cross section is very important in basic nuclear physics and applications based on the Th/U fuel cycle.Using the time-of-flight method and a multi-cell fast-fission ionization chamber,a novel measurement of the^(232)Th(n,f)cross sec-tion relative to^(235)U in the 1–200 MeV range was performed at the China Spallation Neutron Source Back-n white neutron source(Back-n).The fission event-neutron energy spectra of^(232)Th and^(235)U fission cells were measured in the single-bunch mode.Corrected 232Th/235U fission cross-sectional ratios were obtained,and the measurement uncertainties were 2.5–3.7%for energies in the 2–20 MeV range and 3.6–6.2%for energies in the 20–200 MeV range.The^(232)Th(n,f)cross section was obtained by introducing the standard cross section of^(235)U(n,f).The results were compared with those of previous theoreti-cal calculations,measurements,and evaluations.The measured 232Th fission cross section agreed with the main evaluation results in terms of the experimental uncertainty,and 232Th fission resonances were observed in the 1–3 MeV range.The present results provide^(232)Th(n,f)cross-sectional data for the evaluation and design of Th/U cycle nuclear systems.展开更多
The neutron capture cross section of ^(232)Th was measured at the neutron time-of-flight facility Back-n of China Spallation Neutron Source(CSNS)for the first time.The measurement was performed with 4 hydrogen-free de...The neutron capture cross section of ^(232)Th was measured at the neutron time-of-flight facility Back-n of China Spallation Neutron Source(CSNS)for the first time.The measurement was performed with 4 hydrogen-free deuterated benzene C6D6 liquid scintillation detectors,in the ES#2 experiment station on the beam line,at a distance of about 76 m from the neutron-production assembly.The total energy detection principle in combination with the pulse height weighting technique(PHWT)was applied to analyze the measured data.Results of the ^(232)Th(n,γ)reaction cross section in the unresolved resonance region from 4 keV to 100 keV were obtained,which shows a good agreement with the existing experimental data from EXFOR,as well as with the evaluated data from the ENDF/B-VIII.0 and CENDL-3.1.In addition,the excitation function of ^(232)Th(n,γ)^(233)Th reaction in the unresolved resonance region was theoretically calculated by using the code TALYS-1.95.By fitting the experimental cross section and theoretical data,the average parameters in the unresolved resonance region were extracted.展开更多
The^(74)Se is one of 35 p-nuclei,and^(82)Se is a r-process only nucleus,and their(n,γ)cross sections are vital input parameters for nuclear astrophysics reaction network calculations.The neutron capture cross section...The^(74)Se is one of 35 p-nuclei,and^(82)Se is a r-process only nucleus,and their(n,γ)cross sections are vital input parameters for nuclear astrophysics reaction network calculations.The neutron capture cross section in the resonance range of isotopes and even natural selenium samples has not been measured.Promptγ-rays originating from neutron-induced capture events were detected by four C_(6)D_(6) liquid scintillator detectors at the Back-n facility of China Spallation Neutron Source(CSNS).The pulse height weighting technique(PHWT)was used to analyze the data in the 1 e V to 100 ke V region.The deduced neutron capture cross section was compared with ENDF/B-VIII.0,JEFF-3.2,and JENDL-4.0,and some differences were found.Resonance parameters were extracted by the R-matrix code SAMMY in the 1 e V-1 ke V region.All the cross sections ofnatSe and resonance parameters are given in the datasets.The datasets are openly available at http://www.doi.org/10.11922/sciencedb.j00113.00019.展开更多
Silver indium cadmium(Ag–In–Cd) control rod is widely used in pressurized water reactor nuclear power plants,and it is continuously consumed in a high neutron flux environment. The mass ratio of ^(107)Ag in the Ag...Silver indium cadmium(Ag–In–Cd) control rod is widely used in pressurized water reactor nuclear power plants,and it is continuously consumed in a high neutron flux environment. The mass ratio of ^(107)Ag in the Ag–In–Cd control rod is 41.44%. To accurately calculate the consumption value of the control rod, a reliable neutron reaction cross section of the ^(107)Ag is required. Meanwhile,^(107)Ag is also an important weak r nucleus. Thus, the cross sections for neutron induced interactions with ^(107)Ag are very important both in nuclear energy and nuclear astrophysics. The(n, γ) cross section of ^(107)Ag has been measured in the energy range of 1–60 eV using a back streaming white neutron beam line at China spallation neutron source. The resonance parameters are extracted by an R-matrix code. All the cross section of ^(107)Ag and resonance parameters are given in this paper as datasets. The datasets are openly available at http://www.doi.org/10.11922/sciencedb.j00113.00010.展开更多
Irradiation experiments on p-Ga N gate high-electron-mobility transistors(HEMTs) were conducted using neutrons at Back-streaming White Neutron(Back-n) facility at the China Spallation Neutron Source(CSNS).Two groups o...Irradiation experiments on p-Ga N gate high-electron-mobility transistors(HEMTs) were conducted using neutrons at Back-streaming White Neutron(Back-n) facility at the China Spallation Neutron Source(CSNS).Two groups of devices were float-biased,while one group was ON-biased.Post-irradiation analysis revealed that the electrical performance of the devices exhibited progressive degradation with increasing Back-n fluence,with the ON-biased group demonstrating the most pronounced deterioration.This degradation was primarily characterized by a negative shift in the threshold voltage,a significant increase in reverse gate leakage current,and a slight reduction in forward gate leakage.Further analysis of the gate leakage current and capacitance-voltage characteristics indicated an elevated concentration of two-dimensional electron gas(2DEG),attributed to donor-type defects introduced within the barrier layer by Back-n irradiation.These defects act as hole traps,converting into fixed positive charges that deepen the quantum-well conduction band,thereby enhancing the 2DEG density.Additionally,through the trap-assisted tunneling mechanism,these defects serve as tunneling centers,increasing the probability of electron tunneling and consequently elevating the reverse gate leakage current.展开更多
The neutron total cross-section of ^(nat)Cr plays a crucial role in new nuclear engineering design and fundamental science.A new measurement of the neutron-induced total cross-sections of ^(nat)Cr was performed using ...The neutron total cross-section of ^(nat)Cr plays a crucial role in new nuclear engineering design and fundamental science.A new measurement of the neutron-induced total cross-sections of ^(nat)Cr was performed using the transmission method on the back-streaming white neutron beamline(Back-n)at the China Spallation Neutron Source(CSNS).The neutron energy was determined using the time-of-flight technique.The neutron total cross-sections of ^(nat)Cr were obtained across a broad energy range(0.3 eV−20 MeV)in one experiment for the first time.The resulting effective total cross-sections were compared with the existing experimental data in different energy ranges,which revealed good agreement with the evaluated libraries.Theoretical calculation of the total cross-section in the energy range of 1.5 to 20 MeV was then conducted using TALYS-1.96 and compared with the present results.The measurement provides a high-quality total cross-section of ^(nat)Cr,including detailed uncertainty data across a wide energy range,offering a valuable reference for nuclear data re-evaluation and nuclear engineering design.展开更多
The neutron total cross section data of^(9)Be are essential in the nuclear structure model research of light nuclei and nuclear power installations.The neutron total cross section of^(9)Be in the 0.3 eV−120 MeV energy...The neutron total cross section data of^(9)Be are essential in the nuclear structure model research of light nuclei and nuclear power installations.The neutron total cross section of^(9)Be in the 0.3 eV−120 MeV energy region has been measured using time-of-flight and transmission methods with the Neutron Total Cross Sectional Spectrometer(NTOX)based on the multi-cell fast fission chamber at the China Spallation Neutron Source(CSNS)-Back-n white neutron source(Back-n).The fission count-neutron energy distributions of ^(235)U and ^(238)U without samples and with Be samples with three thicknesses were measured in the double-bunch operation mode for a beam power of 100 kW.The Bayesian method was used to eliminate the influence of the double-bunch problem on neutron measurement in the energy region above 10 keV.The neutron total cross section of^(9)Be results was consistent with ENDF/B-VIII.0 evaluation library data in the 0.3 eV−20 MeV energy region.In the energy ranges of 0.3 eV to 10 keV and 0.01 to 20 MeV,the deviations between our results and the evaluation results of ENDF/B-VIII.0 were within 2.5%and 15%,respectively.In the resonance energy region,the measured resonance energies in our experiment were 0.63,0.82,and 2.8 MeV,respectively.The results showed that the total cross section uncertainties of three Be samples were within 2.2%in the energy region below 1 MeV.The total cross section uncertainty of 30 mm Be from ^(235)U was the smallest and less than 5%in the energy region of 0.3 eV−120 MeV.The results of this experiment can provide technical support for further data analysis and related nuclear data evaluation.展开更多
目的探讨首发男性精神分裂症患者康复期工作记忆功能的特点。方法选取2020年11月至2024年12月入住某院精神科的男性首发精神分裂症康复期患者59例(患者组)和男性健康志愿者60名(对照组),采用蒙特利尔认知评估(MoCA)量表对两组被试认知...目的探讨首发男性精神分裂症患者康复期工作记忆功能的特点。方法选取2020年11月至2024年12月入住某院精神科的男性首发精神分裂症康复期患者59例(患者组)和男性健康志愿者60名(对照组),采用蒙特利尔认知评估(MoCA)量表对两组被试认知功能进行评估,通过数字n-back任务(0-back、1-back、2-back)评估工作记忆,比较两组行为学表现。结果两组在年龄、受教育年限、MoCA评分等一般情况差异无统计学意义(P>0.05);患者组在0-back、1-back和2-back任务中的正确率(97.33%、94.00%、82.67%)均显著低于对照组(98.33%、96.16%、89.67%,P<0.05),0-back和1-back任务反应时(440.65 ms、467.00 ms)显著长于对照组(393.85 ms、440.09 ms,P<0.05),2-back反应时两组差异无统计学意义(541.75 ms VS 534.55 ms,P>0.05)。结论首发男性精神分裂症患者康复期存在工作记忆功能损伤,表现为正确率下降和反应延迟,提示其可能是该疾病的原发性认知缺陷。展开更多
^(147,149)Sm are slow neutron capture(s-process)nuclides in nuclear astrophysics,whose(n,γ)cross sections are important input parameters in nucleosynthesis network calculations in the samarium(Sm)region.In addition,^...^(147,149)Sm are slow neutron capture(s-process)nuclides in nuclear astrophysics,whose(n,γ)cross sections are important input parameters in nucleosynthesis network calculations in the samarium(Sm)region.In addition,^(149)Sm is a fission product of ^(235)U with a 1%yield,and its neutron resonance parameters play a critical role in reactor neutronics.According to the available nuclear evaluation databases,a significant disagreement has been observed in the resonance peaks of the ^(147,149)Sm(n,γ)crosssectional data within the energy range of 20-300 eV.In this study,tutron capture cross section of a natural samarium target was measured at the back-streaming white neutron beamline of the China Spallation Neutron Source.The neutron capture yield was obtained,and the neutron resonance parameters for ^(147)Sm at 107.0,139.4,241.7,and 257.3 eV and ^(149)Sm at 23.2,24.6,26.1,28.0,51.5,75.2,90.9,125.3,and 248.4 eV were extracted using the SAMMY code based on R-matrix theory.For the parameters Γ_(n) and Γ_(γ) in these energies of ^(147,149)Sm,the percentages consistent with the results of the CENDL-3.2,ENDF/B-Ⅷ.0,JEFF-3.3,JENDL-4.0,and BROND-3.1 database are 27%,65%,65%,42%,and 58%,respectively.However,27% of the results were inconsistent with those of the major libraries.This work enriches experimental data of the ^(147,149)Sm neutron capture resonance and helps clarify the differences between different evaluation databases at the above energies.展开更多
The neutron total cross-section spectrometer(NTOX)applied on the Back-n beamline at the China Spallation Neutron Source(CSNS)is based on a multicell fission chamber and utilizes ^(235,238)U for neutron detection.To re...The neutron total cross-section spectrometer(NTOX)applied on the Back-n beamline at the China Spallation Neutron Source(CSNS)is based on a multicell fission chamber and utilizes ^(235,238)U for neutron detection.To reduce the experimental uncertainty in the resonance energy region of ^(235,238)U and improve the neutron detection efficiency,a fast scintillator-based neutron total cross-section(FAST)spectrometer was designed.A prototype based on a large-area square ^(6)Li-enriched Cs_(2)LiLaBr_(6)(CLLB)scintillator was constructed and beam-tested.The size of the CLLB scintillator was 50.8 mm×50.8 mm×6 mm,and its side was coupled to an array of 1×8 S14160 MPPC to avoid the irradiation from the high-intensity neutrons and rays.The beam test was performed using a broad-energy pulsed neutron and the time-of-flight(TOF)technique on the Back-n beamline.The results demonstrate that the prototype exhibits good neutron/ γ discrimination capability under strong flash irradiation.The prototype was applied to measure the neutron total cross-section of ^(nat)Pb and the result was compared with that obtained using the NTOX.The two results were consistent in the energy region of 0.3 eV to 1 keV,and the prototype showed a higher detection efficiency and did not exhibit fission resonance effect.This type of spectrometer can be used as a complement to the NTOX in the low-energy range and provides a technical reference and framework for developing the FAST spectrometer on the Back-n beamline.展开更多
The neutron-induced total cross-section of ^(209)Bi is crucial for the physical design and safety assessment of lead-based fast reactors, and the quality of experimental data should be improved for evaluation and appl...The neutron-induced total cross-section of ^(209)Bi is crucial for the physical design and safety assessment of lead-based fast reactors, and the quality of experimental data should be improved for evaluation and application.A recent experiment was conducted on the back-streaming white neutron beamline(Back-n) at the China Spallation Neutron Source(CSNS) using the neutron total cross-section spectrometer(NTOX). The neutron energy was determined using a fast multi-cell fission chamber and the time-of-flight technique. Two high-purity bismuth samples,6 mm and 20 mm in thickness, were chosen for neutron transmission measurements and comparisons. The neutron total cross-sections of ^(209)Bi, ranging from 0.3 e V to 20 Me V, were derived considering neutron flight time determination, flight path calibration, and background subtraction. A comparison of the experimental results with the data in the ENDF/B-VⅢ.0 library showed fair agreement, and the point-wise cross-sections were found to be consistent with existing experimental data. Special attention was given to the determination of resonance parameters, which were analyzed using the R-matrix code SAMMY and Bayesian method in the 0.5 ke V to 20 ke V energy range. The extracted resonance parameters were compared to previously reported results and evaluated data. This study is recognized as the first one where the neutron total cross-section of bismuth across such a broad energy spectrum is measured in a single measurement or experiment, and it provides valuable data for the assessment of related reaction information for evaluated libraries and the advancement of lead-bismuth-based nuclear systems.展开更多
The capture cross sections of the ^(169)Tm(n,γ)reaction were measured at the back streaming white neutron beam line(Back-n)of the China Spallation Neutron Source(CSNS)using four C_(6)D_(6) liquid scintillation detect...The capture cross sections of the ^(169)Tm(n,γ)reaction were measured at the back streaming white neutron beam line(Back-n)of the China Spallation Neutron Source(CSNS)using four C_(6)D_(6) liquid scintillation detectors.The background subtraction,normalization,and correction were carefully considered in the data analysis to obtain accurate cross sections.For the resonance at 3.9 eV,the R-matrix code SAMMY was used to determine the resonance parameters with the internal normalization method.The average capture cross sections of ^(169)Tm for energy between 30 and 300 keV were extracted relative to the ^(197)Au(n,γ)reaction.The measured cross sections of the ^(169)Tm(n,γ)reaction were reported in logarithmically equidistant energy bins with 20 bins per energy decade with a total uncertainty of 5.4%-7.0% in this study and described in terms of average resonance parameters using a Hauser-Feshbach calculation with fluctuations.The point-wise cross sections and the average resonance parameters showed fair agreement with the evaluated values of the ENDF/B-Ⅷ.0 library in the energy region studied.展开更多
基金This work is supported by the National Natural Science Foundation of China(No.12375296)the Key Laboratory of Nuclear Data Foundation(No.JCKY2022201C153)+2 种基金the Natural Science Foundation of Hunan Province of China(Nos.2021JJ40444,2020RC3054)the Youth Innovation Promotion Association CAS(No.2023014)the National Key Research and Development Plan(No.2022YFA1603303).
文摘The neutron-induced total cross sections of natural lead have been measured in a wide energy range(0.3 eV-20 MeV)on the back-streaming white neutron beamline(Back-n)at the China Spallation Neutron Source.Neutron energy was determined by the neutron total cross-section spectrometer using the time-of-flight technique.A fast multi-cell fission chamber was used as the neutron detector,and a 10-mm-thick high-purity natural lead sample was employed for the neutron transmission measurements.The on-beam background was determined using Co,In,Ag,and Cd filters.The excitation function of ^(nat)Pb(n,tot)reaction below 20 MeV was calculated using the TALYS-1.96 nuclear-reaction modeling program.The present results were compared with previous results,the evaluated data available in the five major evaluated nuclear data libraries(i.e.,ENDF/B-VIII.0,JEFF-3.3,JENDL-5,CENDL-3.2,and BROND-3.1),and the theoretical calculation curve.Good agreement was found between the new results and those of previous experiments and with the theoretical curves in the corresponding region.This measurement obtained the neutron total cross section of natural lead with good accuracy over a wide energy range and added experimental data in the resonance energy range.This provides more reliable experimental data for nuclear engineering design and nuclear data evaluation of lead.
基金supported by the Young Elite Scientists Sponsorship Program by CAST(No.YESS20210441)the National Natural Science Foundation of China(Nos.U2167208,11875223)。
文摘This study investigates the effects of displacement damage on the dark signal of a pinned photodiode CMOS image sensor(CIS)following irradiation with back-streaming white neutrons from white neutron sources at the China spallation neutron source(CSNS)and Xi'an pulsed reactor(XAPR).The mean dark signal,dark signal non-uniformity(DSNU),dark signal distribution,and hot pixels of the CIS were compared between the CSNS back-n and XAPR neutron irradiations.The nonionizing energy loss and energy distribution of primary knock-on atoms in silicon,induced by neutrons,were calculated using the open-source package Geant4.An analysis combining experimental and simulation results showed a noticeable proportionality between the increase in the mean dark signal and the displacement damage dose(DDD).Additionally,neutron energies influence DSNU,dark signal distribution,and hot pixels.High neutron energies at the same DDD level may lead to pronounced dark signal non-uniformity and elevated hot pixel values.
基金supported by the Youth Talent Program of China National Nuclear Corporationthe Continuous-Support Basic Scientific Research Project(BJ010261223282)+1 种基金the National Natural Science Foundation of China(No.11790321)the Research and development project of China National Nuclear Corporation。
文摘The back-streaming white-neutron beamline(Back-n)of the China Spallation Neutron Source is an essential neutronresearch platform built for the study of nuclear data,neutron physics,and neutron applications.Many types of cross-sectional neutron-reaction measurements have been performed at Back-n since early 2018.These measurements have shown that a significant number of gamma rays can be transmitted to the experimental stations of Back-n along with the neutron beam.These gamma rays,commonly referred to as in-beam gamma rays,can induce a non-negligible experimental background in neutron-reaction measurements.Studying the characteristics of in-beam gamma rays is important for understanding the experimental background.However,measuring in-beam gamma rays is challenging because most gamma-ray detectors are sensitive to neutrons;thus,discriminating between neutron-induced signals and those from in-beam gamma rays is difficult.In this study,we propose the use of the black resonance filter method and a CeBr_(3) scintillation detector to measure the characteristics of the in-beam gamma rays of Back-n.Four types of black resonance filters,^(181)Ta,^(59)Co,^(nat)Ag,and^(nat)Cd,were used in this measurement.The time-of-flight(TOF)technique was used to select the detector signals remaining in the absorption region of the TOF spectra,which were mainly induced by in-beam gamma rays.The energy distribution and flux of the in-beam gamma rays of Back-n were determined by analyzing the deposited energy spectra of the CeBr_(3) scintillation detector and using Monte Carlo simulations.Based on the results of this study,the background contributions from in-beam gamma rays in neutron-reaction measurements at Back-n can be reasonably evaluated,which is beneficial for enhancing both the experimental methodology and data analysis.
基金supported by the National Key Research and Development Plan(No.2016YFA0401603)the National Natural Science Foundation of China(No.11675155)
文摘To verify the performance of the neutron total cross-sectional spectrometer, the neutron total cross section of carbon is initially measured in the energy range of 1 eV to 20 MeV using the time-of-flight method. The measurement is performed at the Back-n white neutron source with a 76-m time-of-flight path using the China Spallation Neutron Source. A multilayer fast fission chamber with 235U and 238U is employed as the neutron detector. The diameter and thickness of the natural graphite sample are 70 mm and 40 mm, respectively. Signal waveforms are collected using a data acquisition system. Off-line data processing was used to obtain the neutron time-of-flight spectra and transmissions. The uncertainty of the counting statistics is generally approximately 3% for each bin in the energy range of 1–20 MeV. It is determined that the results for the neutron total cross section of carbon obtained using ^235U cells are in good agreement with the results obtained using 238U cells within limits of statistical uncertainty. Moreover, the measured total cross sections show good agreement with the broadening evaluated data.
基金supported by the National Natural Science Foundation of China(Nos.11875311,11905274,11705156,and 11605097)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB34030000)。
文摘The neutron capture cross section of 197 Au was measured using the time-of-flight(TOF)technique at the Back-n facility of the China Spallation Neutron Source(CSNS)in the 1 eV to 100 keV range.Prompt c-rays originating from neutron-induced capture events were detected by four C_(6)D_(6) liquid scintillator detectors.Pulse height weighting technology(PHWT)was used to analyze the data.The results are in good agreement with ENDF/B-VIII.0,CENDL-3.1,and other evaluated libraries in the resonance region,and in agreement with both n TOF and GELINA experimental data in the 5–100 keV range.Finally,the resonance peaks in the energy range from 1eV to 1 keV were fitted by the SAMMY R-matrix code.
基金supported by the National Natural Science Foundation of China(Nos.11675155,11790321,and 12075216)the National Key Research and Development Plan(No.2016YFA0401603).
文摘The ^(232)Th(n,f)cross section is very important in basic nuclear physics and applications based on the Th/U fuel cycle.Using the time-of-flight method and a multi-cell fast-fission ionization chamber,a novel measurement of the^(232)Th(n,f)cross sec-tion relative to^(235)U in the 1–200 MeV range was performed at the China Spallation Neutron Source Back-n white neutron source(Back-n).The fission event-neutron energy spectra of^(232)Th and^(235)U fission cells were measured in the single-bunch mode.Corrected 232Th/235U fission cross-sectional ratios were obtained,and the measurement uncertainties were 2.5–3.7%for energies in the 2–20 MeV range and 3.6–6.2%for energies in the 20–200 MeV range.The^(232)Th(n,f)cross section was obtained by introducing the standard cross section of^(235)U(n,f).The results were compared with those of previous theoreti-cal calculations,measurements,and evaluations.The measured 232Th fission cross section agreed with the main evaluation results in terms of the experimental uncertainty,and 232Th fission resonances were observed in the 1–3 MeV range.The present results provide^(232)Th(n,f)cross-sectional data for the evaluation and design of Th/U cycle nuclear systems.
基金supported by the Chinese TMSR Strategic Pioneer Science and Technology Project(Grant No.XDA02010000)the National Natural Science Foundation of China(Grant No.11790321).
文摘The neutron capture cross section of ^(232)Th was measured at the neutron time-of-flight facility Back-n of China Spallation Neutron Source(CSNS)for the first time.The measurement was performed with 4 hydrogen-free deuterated benzene C6D6 liquid scintillation detectors,in the ES#2 experiment station on the beam line,at a distance of about 76 m from the neutron-production assembly.The total energy detection principle in combination with the pulse height weighting technique(PHWT)was applied to analyze the measured data.Results of the ^(232)Th(n,γ)reaction cross section in the unresolved resonance region from 4 keV to 100 keV were obtained,which shows a good agreement with the existing experimental data from EXFOR,as well as with the evaluated data from the ENDF/B-VIII.0 and CENDL-3.1.In addition,the excitation function of ^(232)Th(n,γ)^(233)Th reaction in the unresolved resonance region was theoretically calculated by using the code TALYS-1.95.By fitting the experimental cross section and theoretical data,the average parameters in the unresolved resonance region were extracted.
基金supported by the National Natural Science Foundation of China(Grant Nos.11875311,11905274,11705156,11605097,and U2032146)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB34030000)。
文摘The^(74)Se is one of 35 p-nuclei,and^(82)Se is a r-process only nucleus,and their(n,γ)cross sections are vital input parameters for nuclear astrophysics reaction network calculations.The neutron capture cross section in the resonance range of isotopes and even natural selenium samples has not been measured.Promptγ-rays originating from neutron-induced capture events were detected by four C_(6)D_(6) liquid scintillator detectors at the Back-n facility of China Spallation Neutron Source(CSNS).The pulse height weighting technique(PHWT)was used to analyze the data in the 1 e V to 100 ke V region.The deduced neutron capture cross section was compared with ENDF/B-VIII.0,JEFF-3.2,and JENDL-4.0,and some differences were found.Resonance parameters were extracted by the R-matrix code SAMMY in the 1 e V-1 ke V region.All the cross sections ofnatSe and resonance parameters are given in the datasets.The datasets are openly available at http://www.doi.org/10.11922/sciencedb.j00113.00019.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11875311, 11905274, 1705156, U2032146, 11865010, 11765015, and 1160509)the Natural Science Foundation of Inner Mongolia, China (Grant Nos. 2019JQ01 and 2018MS01009)the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDB34030000)。
文摘Silver indium cadmium(Ag–In–Cd) control rod is widely used in pressurized water reactor nuclear power plants,and it is continuously consumed in a high neutron flux environment. The mass ratio of ^(107)Ag in the Ag–In–Cd control rod is 41.44%. To accurately calculate the consumption value of the control rod, a reliable neutron reaction cross section of the ^(107)Ag is required. Meanwhile,^(107)Ag is also an important weak r nucleus. Thus, the cross sections for neutron induced interactions with ^(107)Ag are very important both in nuclear energy and nuclear astrophysics. The(n, γ) cross section of ^(107)Ag has been measured in the energy range of 1–60 eV using a back streaming white neutron beam line at China spallation neutron source. The resonance parameters are extracted by an R-matrix code. All the cross section of ^(107)Ag and resonance parameters are given in this paper as datasets. The datasets are openly available at http://www.doi.org/10.11922/sciencedb.j00113.00010.
基金supported by the National Natural Science Foundation of China (Grant Nos.12120101005,U2030104,12175174,11975174,and 12105229)State Key Laboratory Foundation of Laser Interaction with Matter (Grant Nos.SKLLIM1807 and SKLLIM2106)+1 种基金the Postdoctoral Fellowship Program of CPSF (Grant No.GZC20241372)National Key Laboratory of Intense Pulsed Radiation Simulation and Effect (Grant No.NKLIPR2419)。
文摘Irradiation experiments on p-Ga N gate high-electron-mobility transistors(HEMTs) were conducted using neutrons at Back-streaming White Neutron(Back-n) facility at the China Spallation Neutron Source(CSNS).Two groups of devices were float-biased,while one group was ON-biased.Post-irradiation analysis revealed that the electrical performance of the devices exhibited progressive degradation with increasing Back-n fluence,with the ON-biased group demonstrating the most pronounced deterioration.This degradation was primarily characterized by a negative shift in the threshold voltage,a significant increase in reverse gate leakage current,and a slight reduction in forward gate leakage.Further analysis of the gate leakage current and capacitance-voltage characteristics indicated an elevated concentration of two-dimensional electron gas(2DEG),attributed to donor-type defects introduced within the barrier layer by Back-n irradiation.These defects act as hole traps,converting into fixed positive charges that deepen the quantum-well conduction band,thereby enhancing the 2DEG density.Additionally,through the trap-assisted tunneling mechanism,these defects serve as tunneling centers,increasing the probability of electron tunneling and consequently elevating the reverse gate leakage current.
基金Supported by the National Natural Science Foundation of China(12375296)the Educational Commission of Hunan Province,China(21A0281)+2 种基金the Youth Innovation Promotion Association CAS(2023014)the Key Laboratory of Nuclear Data Foundation(JCKY2022201C153)the Natural Science Foundation of Hunan Province,China(2024RC3205,2024JJ2044)。
文摘The neutron total cross-section of ^(nat)Cr plays a crucial role in new nuclear engineering design and fundamental science.A new measurement of the neutron-induced total cross-sections of ^(nat)Cr was performed using the transmission method on the back-streaming white neutron beamline(Back-n)at the China Spallation Neutron Source(CSNS).The neutron energy was determined using the time-of-flight technique.The neutron total cross-sections of ^(nat)Cr were obtained across a broad energy range(0.3 eV−20 MeV)in one experiment for the first time.The resulting effective total cross-sections were compared with the existing experimental data in different energy ranges,which revealed good agreement with the evaluated libraries.Theoretical calculation of the total cross-section in the energy range of 1.5 to 20 MeV was then conducted using TALYS-1.96 and compared with the present results.The measurement provides a high-quality total cross-section of ^(nat)Cr,including detailed uncertainty data across a wide energy range,offering a valuable reference for nuclear data re-evaluation and nuclear engineering design.
基金Supported by the National Key Research and Development Plan(2016YFA0401603)the National Natural Science Foundation of China(11675155,11790321)Foundation of President of China Academy of Engineering Physics(YZJLX2016003)。
文摘The neutron total cross section data of^(9)Be are essential in the nuclear structure model research of light nuclei and nuclear power installations.The neutron total cross section of^(9)Be in the 0.3 eV−120 MeV energy region has been measured using time-of-flight and transmission methods with the Neutron Total Cross Sectional Spectrometer(NTOX)based on the multi-cell fast fission chamber at the China Spallation Neutron Source(CSNS)-Back-n white neutron source(Back-n).The fission count-neutron energy distributions of ^(235)U and ^(238)U without samples and with Be samples with three thicknesses were measured in the double-bunch operation mode for a beam power of 100 kW.The Bayesian method was used to eliminate the influence of the double-bunch problem on neutron measurement in the energy region above 10 keV.The neutron total cross section of^(9)Be results was consistent with ENDF/B-VIII.0 evaluation library data in the 0.3 eV−20 MeV energy region.In the energy ranges of 0.3 eV to 10 keV and 0.01 to 20 MeV,the deviations between our results and the evaluation results of ENDF/B-VIII.0 were within 2.5%and 15%,respectively.In the resonance energy region,the measured resonance energies in our experiment were 0.63,0.82,and 2.8 MeV,respectively.The results showed that the total cross section uncertainties of three Be samples were within 2.2%in the energy region below 1 MeV.The total cross section uncertainty of 30 mm Be from ^(235)U was the smallest and less than 5%in the energy region of 0.3 eV−120 MeV.The results of this experiment can provide technical support for further data analysis and related nuclear data evaluation.
文摘目的探讨首发男性精神分裂症患者康复期工作记忆功能的特点。方法选取2020年11月至2024年12月入住某院精神科的男性首发精神分裂症康复期患者59例(患者组)和男性健康志愿者60名(对照组),采用蒙特利尔认知评估(MoCA)量表对两组被试认知功能进行评估,通过数字n-back任务(0-back、1-back、2-back)评估工作记忆,比较两组行为学表现。结果两组在年龄、受教育年限、MoCA评分等一般情况差异无统计学意义(P>0.05);患者组在0-back、1-back和2-back任务中的正确率(97.33%、94.00%、82.67%)均显著低于对照组(98.33%、96.16%、89.67%,P<0.05),0-back和1-back任务反应时(440.65 ms、467.00 ms)显著长于对照组(393.85 ms、440.09 ms,P<0.05),2-back反应时两组差异无统计学意义(541.75 ms VS 534.55 ms,P>0.05)。结论首发男性精神分裂症患者康复期存在工作记忆功能损伤,表现为正确率下降和反应延迟,提示其可能是该疾病的原发性认知缺陷。
基金supported by the Natural Science Foundation of Hunan Province,China(No.2025JJ60020)the National Key Research and Development Program(No.2022YFA1603300)+1 种基金National Natural Science Foundation of China(Nos.12275338 and 12388102)China Institute of Atomic Energy(No.CIAE-FWGKJT-23-0820).
文摘^(147,149)Sm are slow neutron capture(s-process)nuclides in nuclear astrophysics,whose(n,γ)cross sections are important input parameters in nucleosynthesis network calculations in the samarium(Sm)region.In addition,^(149)Sm is a fission product of ^(235)U with a 1%yield,and its neutron resonance parameters play a critical role in reactor neutronics.According to the available nuclear evaluation databases,a significant disagreement has been observed in the resonance peaks of the ^(147,149)Sm(n,γ)crosssectional data within the energy range of 20-300 eV.In this study,tutron capture cross section of a natural samarium target was measured at the back-streaming white neutron beamline of the China Spallation Neutron Source.The neutron capture yield was obtained,and the neutron resonance parameters for ^(147)Sm at 107.0,139.4,241.7,and 257.3 eV and ^(149)Sm at 23.2,24.6,26.1,28.0,51.5,75.2,90.9,125.3,and 248.4 eV were extracted using the SAMMY code based on R-matrix theory.For the parameters Γ_(n) and Γ_(γ) in these energies of ^(147,149)Sm,the percentages consistent with the results of the CENDL-3.2,ENDF/B-Ⅷ.0,JEFF-3.3,JENDL-4.0,and BROND-3.1 database are 27%,65%,65%,42%,and 58%,respectively.However,27% of the results were inconsistent with those of the major libraries.This work enriches experimental data of the ^(147,149)Sm neutron capture resonance and helps clarify the differences between different evaluation databases at the above energies.
基金supported by the National Natural Science Foundation of China(No.12375296)the Key Laboratory of Nuclear Data Foundation(No.JCKY2022201C153)+1 种基金the Science and Technology Innovation Program of Hunan Province(No.2024RC3205)the Natural Science Foundation of Hunan Province,China(No.2024JJ2044).
文摘The neutron total cross-section spectrometer(NTOX)applied on the Back-n beamline at the China Spallation Neutron Source(CSNS)is based on a multicell fission chamber and utilizes ^(235,238)U for neutron detection.To reduce the experimental uncertainty in the resonance energy region of ^(235,238)U and improve the neutron detection efficiency,a fast scintillator-based neutron total cross-section(FAST)spectrometer was designed.A prototype based on a large-area square ^(6)Li-enriched Cs_(2)LiLaBr_(6)(CLLB)scintillator was constructed and beam-tested.The size of the CLLB scintillator was 50.8 mm×50.8 mm×6 mm,and its side was coupled to an array of 1×8 S14160 MPPC to avoid the irradiation from the high-intensity neutrons and rays.The beam test was performed using a broad-energy pulsed neutron and the time-of-flight(TOF)technique on the Back-n beamline.The results demonstrate that the prototype exhibits good neutron/ γ discrimination capability under strong flash irradiation.The prototype was applied to measure the neutron total cross-section of ^(nat)Pb and the result was compared with that obtained using the NTOX.The two results were consistent in the energy region of 0.3 eV to 1 keV,and the prototype showed a higher detection efficiency and did not exhibit fission resonance effect.This type of spectrometer can be used as a complement to the NTOX in the low-energy range and provides a technical reference and framework for developing the FAST spectrometer on the Back-n beamline.
基金the National Natural Science Foundation of China(12375296)the Key Laboratory of Nuclear Data Foundation(JCKY2022201C153)+1 种基金the National Key Research and Development Plan(2022YFA1603303)the Natural Science Foundation of Hunan Province of China(2021JJ40444,2020RC3054)。
文摘The neutron-induced total cross-section of ^(209)Bi is crucial for the physical design and safety assessment of lead-based fast reactors, and the quality of experimental data should be improved for evaluation and application.A recent experiment was conducted on the back-streaming white neutron beamline(Back-n) at the China Spallation Neutron Source(CSNS) using the neutron total cross-section spectrometer(NTOX). The neutron energy was determined using a fast multi-cell fission chamber and the time-of-flight technique. Two high-purity bismuth samples,6 mm and 20 mm in thickness, were chosen for neutron transmission measurements and comparisons. The neutron total cross-sections of ^(209)Bi, ranging from 0.3 e V to 20 Me V, were derived considering neutron flight time determination, flight path calibration, and background subtraction. A comparison of the experimental results with the data in the ENDF/B-VⅢ.0 library showed fair agreement, and the point-wise cross-sections were found to be consistent with existing experimental data. Special attention was given to the determination of resonance parameters, which were analyzed using the R-matrix code SAMMY and Bayesian method in the 0.5 ke V to 20 ke V energy range. The extracted resonance parameters were compared to previously reported results and evaluated data. This study is recognized as the first one where the neutron total cross-section of bismuth across such a broad energy spectrum is measured in a single measurement or experiment, and it provides valuable data for the assessment of related reaction information for evaluated libraries and the advancement of lead-bismuth-based nuclear systems.
基金Supported by the National Natural Science Foundation of China(11790321,11805282)the National Key Research and Development Program of China(2016YFA0401601)。
文摘The capture cross sections of the ^(169)Tm(n,γ)reaction were measured at the back streaming white neutron beam line(Back-n)of the China Spallation Neutron Source(CSNS)using four C_(6)D_(6) liquid scintillation detectors.The background subtraction,normalization,and correction were carefully considered in the data analysis to obtain accurate cross sections.For the resonance at 3.9 eV,the R-matrix code SAMMY was used to determine the resonance parameters with the internal normalization method.The average capture cross sections of ^(169)Tm for energy between 30 and 300 keV were extracted relative to the ^(197)Au(n,γ)reaction.The measured cross sections of the ^(169)Tm(n,γ)reaction were reported in logarithmically equidistant energy bins with 20 bins per energy decade with a total uncertainty of 5.4%-7.0% in this study and described in terms of average resonance parameters using a Hauser-Feshbach calculation with fluctuations.The point-wise cross sections and the average resonance parameters showed fair agreement with the evaluated values of the ENDF/B-Ⅷ.0 library in the energy region studied.
