最新刊期
      卷 41 ， 期 8 ， 2018

        LOW ENERGY ACCELERATOR, RAY AND APPLICATIONS

      • Zhiyao LI,Han CHEN,Yingchao DU
        Vol. 41, Issue 8, Article number: 080202(2018) DOI: 10.11889/j.0253-3219.2018.hjs.41.080202
        摘要：Background An important limitation for using of velocity bunching is nonlinear effect which leads to non-uniform compression and beam quality deterioration. Purpose This study aims to realize nonlinear compensation caused by nonlinear effect in velocity bunching. Method Based on the self-induced wakefield while the beam passing through a wakefield structure, nonlinear compensation is achieved by modulation of beam longitudinal phase space. Start-to-end simulation by ASTRA is performed in this paper. Results The results show that slice energy spread of beam increased from about 3keV to about 20keV which is benefit to suppress the micro-bunching instability in subsequent process. Conclusion Uniform velocity bunching can be realized by the method of nonlinear compensation to general high quality uniformly compressed beam.  
        关键词：Velocity bunching;Wakefield structure;Nonlinear compensation   
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        发布时间：2021-05-19
      • Ruixue NIAN,Shiwei JING
        Vol. 41, Issue 8, Article number: 080201(2018) DOI: 10.11889/j.0253-3219.2018.hjs.41.080201
        摘要：Background The neutron yield and lifetime of the neutron tube are affected by the performance of the target. The study of the characteristics of the target materials has far-reaching significance for improving the performance of the neutron tube. Purpose This study aims to get the effect of alloy target material on neutron yield and lifetime of neutron tube. Methods The neutron yield of titanium targets under different beams and accelerating high voltage conditions is simulated by SRIM 2008 and compared with the results of 3He neutron monitor. The experimental and simulation results are in good agreement. The neutron output and sputtering yield at different deuterium energies and different alloy targets are calculated. The alloy targets include titanium alloys containing scandium, molybdenum and niobium with different atom ratios. Results The results show that the neutron yield of titanium alloys containing scandium as target materials in the incident ion energy 120 keV and the alloy ratio of 0.2 is the highest, and the simulated value can reach 1.24×109 s-1. The sputtering yield of metal atom and tritium atom is lower which the alloy ratio of titanium alloys containing scandium is 0.6. Compared with the titanium alloys containing molybdenum and niobium, the one containing scandium has higher neutron yield, and lower sputtering yield. Conclusion This work is the basis for the research of alloy target materials. Titanium alloy containing scandium is a potential material for the preparation of a high-yield and long-lived neutron tube in the future.  
        关键词：Neutron tube;SRIM;Alloy target;Neutron output;Sputtering yield   
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        发布时间：2021-05-19

        NUCLEAR ELECTRONICS AND INSTRUMENTATION

      • Linfeng HE,Fangdong TANG,Chao ZHAO
        Vol. 41, Issue 8, Article number: 080401(2018) DOI: 10.11889/j.0253-3219.2018.hjs.41.080401
        摘要：BackgroundIn the last decade, a large number of environmental gamma spectrometers have been installed to monitor ambient radionuclide in the environmental radiation monitoring stations in China. However, the response coefficients to airborne radionuclide concentration of most facilities were unknown. PurposeThis study aims to establish an accurate and practical method for determining the response coefficient to airborne radionuclide concentration of the environmental gamma spectrometers. MethodsBased on two assumptions on the spatial distribution of the facility's detection efficiency, a theoretical model was proposed and simplified. Subsequently. Monte Carlo simulation method was utilized to analyze the deviation contributed by the two assumptions for several common radionuclides quantitatively. Simultaneously, the detection efficiency spatial distribution of a self-developed gamma spectrometer which consists of a typical NaI(Tl) crystal (76.2 mm×76.2 mm) was measured in an 137Cs expose experiment to verify the accuracy of Monte Carlo simulation method. Lastly, the method for determining the response coefficient was established by using the simplified theoretical model, and applied to two environmental gamma spectrometers in field. ResultsThe relative difference between the experimental and simulated detection efficiency of the self-developed gamma spectrometer was less than 6% at every measurement position. According to the Monte Carlo simulation results of the typical gamma spectrometer, relative deviations of response coefficients to several common airborne radionuclides contributed by the two assumptions were less than 0.1% and 10% respectively. In the field test, the changing trend of the detection efficiency was similar to the simulated results, and the response coefficients to airborne 137Cs of the two facilities were 6.49 min-1·Bq-1·m3 and 2.62 min-1·Bq-1·m3 respectively. ConclusionThe results of Monte Carlo simulation indicated that the simplified model was acceptable for environmental radiation monitoring field, and the applicability of this method had been validated through field test.  
        关键词：Environmental gamma spectrometer;Response coefficient to activity concentration;Monte Carlo simulation   
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        发布时间：2021-05-19
      • Hu WANG,Wensheng WU,Hongwei WANG,Liwei REN,Yunlong GE,Duo DONG,Ruigang WANG,Liuqiong HE
        Vol. 41, Issue 8, Article number: 080406(2018) DOI: 10.11889/j.0253-3219.2018.hjs.41.080406
        摘要：BackgroundThe inelastic scattering reaction between neutron and formation element in pulsed neutron porosity logging can not be neglected. Compared to chemical source, the influences of lithology and density on the measurement of hydrogen index increase, so the measured apparent porosity may be affected. PurposeThis study aims to investigate the formation density influence and corresponding correction method. MethodsFirst of all, the relationship of slowing-down length of neutrons in the infinite homogeneous formation between bulk density and hydrogen index was deduced, and numerical simulation was performed. Then the correlation between the quotient of counting rate after correction of formation density and the hydrogen index of the formation was obtained. Finally, the quotients of far detector counting rate and near detector counting rate were used to correct the formation density, and the result of the experiment was analyzed. ResultsThe relation between the bulk density corrected count ratio and hydrogen index was obtained, and the sensitiveness of pulsed neutron porosity logging got improved. ConclusionsCorrecting count ratio of near detector and far detector with bulk density by means of numerical simulation can reduce the influence of bulk density, enhance the detection sensitivity of porosity and reduce the influence of lithology and shale effect.  
        关键词：Neutron porosity log;Bulk density;Hydrogen index;Sensitivity   
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        发布时间：2021-05-19
      • Yuefeng HE,Yanfeng WANG,Yingtan ZHAO,Ruirui FAN,Changli MA,Xueyu GONG,Zhijia SUN,Ping CAO,Li YU,Manyu ZHENG,Ying ZHANG
        Vol. 41, Issue 8, Article number: 080403(2018) DOI: 10.11889/j.0253-3219.2018.hjs.41.080403
        摘要：BackgroundA neutron sensitive multi-wire proportional chamber (MWPC) is one of important components for the CSNS's (China spallation neutron source) construction.In terms of large-area neutron detectors, the delay-line readout method is a new type of signal readout method. PurposeThis study aims to design and implement a 200mm×200mm sensitive area MWPC prototype with a delay-line readout system to verify the feasibility of the delay-line readout method. MethodsAn unified anode readout and two channel for each cathode signal are implemented with the MWPC. At first we put α radiation sources in three different positions of the neutron detector, the position information of the incident particle what these sources scattering into the detector contained by the induced signal in cathode. After avalanche, spreads through a series of 5ns modules to the opposite ends, a high precision time to digital converter (TDC) is employed for determining arrival time, from which the incident position can be derived. Finally, the root software is used for data analysis so as to verify the position performance of this MWPC. ResultsThe preliminary results with the α radiation source testing showed the position resolution is better than 2 mm which achieved by this proposed MWPC. ConclusionThe developed MWPC detector can successfully perform position measurement. Meanwhile, it is good to verify the feasibility of the delay-line readout method in the measurement of large-area neutron detectors.  
        关键词：Multi-wire proportional chamber;Delay module readout;Position measurement   
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        发布时间：2021-05-19
      • Gang WANG,Yuekun HENG,Xiaohua LI,Nan LI,Zhimin WANG,Miao HE,Fengjiao LUO,Liangsheng HUANG,Mengzhao LI,Yuzhen YANG,Yan ZHANG,Kaile WEN
        Vol. 41, Issue 8, Article number: 080402(2018) DOI: 10.11889/j.0253-3219.2018.hjs.41.080402
        摘要：BackgroundThe 7.62cm (3-inch) photomultiplier tube (PMT) is an important component of the Jiangmen Underground Neutrino Observatory (JUNO) giant detector, which will work as an independent detection system for the physics measurements, and will calibrate as well as crosscheck the 50.8cm (20-inch) PMT detection system. It is required that the single-channel current supply of each 7.62cm PMT high voltage does not exceed 10 μA. PurposeThis study aims to reduce the performance requirements of the high-voltage power supply system and improve the reliability of the system. MethodsThe effects of different high-voltage currents on the detection performance of the 7.62cm PMT are studied by experiments. Three kinds of high voltage current dividers were used to test the performance of an HZC XP72B20 7.62cm PMT sample (serial number 70069), including gain, energy resolution, peak to valley ratio and non-linearity of the anode output signal. ResultsThe change of the divider current has negligible impact on these probing performances. ConclusionsThis result provides an important experimental reference for the use of small divider current in the JUNO detector for the 7.62cm PMT.  
        关键词：Photomultiplier tube;Divider current;Single photoelectron spectrum;Nonlinearity   
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        发布时间：2021-05-19
      • Hao QIAO,Siguang WANG
        Vol. 41, Issue 8, Article number: 080404(2018) DOI: 10.11889/j.0253-3219.2018.hjs.41.080404
        摘要：BackgroundThe relationship of detector resolution changed with energy should be considered when the intrinsic spectra have wide range in experiments like neutrino energy measurement. The normal numerical integration method using center processing unit (CPU) does not meet the performance requirement. PurposeThis study aims to find a method which can accelerate the convolution operation without losing convenience. MethodsThe graphics processing unit (GPU) and compute unified device architecture (CUDA) toolkit are employed to implement RooFit's probability density function (PDF) class and calculate the numerical integration parallelly. ResultsIn the test server using E5-2603 v3 as CPU and K80 as GPU, this method improves the speed as high as 218 times when the integration nodes set to be 1 million. ConclusionCombining GPU with RooFit library can get a significant improvement in the speed without lose RooFit's convenience. The method could be an example for those experiments which need complicated convolution calculations.  
        关键词：GPU;Convolution;Numerical integration;RooFit;CUDA   
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        发布时间：2021-05-19
      • Jiangfeng LI,Ming SU,Zhonghua XIONG,Fan GAO
        Vol. 41, Issue 8, Article number: 080405(2018) DOI: 10.11889/j.0253-3219.2018.hjs.41.080405
        摘要：BackgroundCompared with the traditional X ray detection method, use of fast neutron to detect explosives can get more accurate result which has attracted worldwide attention. PurposeThis study aims to detect explosive by using the continuous fast neutron resonance spectrum of radioactive neutron source. MethodsThe Monte Carlo program Monte Carlo N-particle code (MCNP) was used to simulate the neutron spectrum of four kinds of explosives combining neutron time of flight method. The associated γ particle method can be used to measure the neutron time of flight (TOF) spectrum of 252Cf in practice, and levenberg-marquardt (L-M) fitting method was applicable to accurately calculate relative proportions of each nuclide. Based on the TOF methods of neutron energy spectrum measuring, the influence on the calculation results of time resolution, neutron flight distance, the thickness of the explosives and the statistical fluctuation has been taken into account for the measurement accuracy. ResultsThe results show that L-M method can accurately calculate explosive nuclide ratio with high energy resolution, the maximum error was less than 10%. The energy resolution and thickness of the explosives increase the calculation error whilst the influence of statistical fluctuation can be eliminated by more than 10 6 neutron counting, ConclusionsThe exact nuclide ratio of the material can be obtained by fitting the fast neutron resonance continuous spectrum to realize the detection of the explosives. However, further research is needed to apply this method to the on-site measurement.  
        关键词：Fast neutron resonance;Explosive;Mont Carlo simulation;L-M algorithm   
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        发布时间：2021-05-19

        SYNCHROTRON RADIATION TECHNOLOGY AND APPLICATIONS

      • Bo GAO,Yongbin LENG,Hanjiao CHEN,Jie CHEN
        Vol. 41, Issue 8, Article number: 080101(2018) DOI: 10.11889/j.0253-3219.2018.hjs.41.080101
        摘要：Background Spatial interferometer technology is widely used to measure the transverse beam size of synchrotron radiation around the world. The interferometer usually uses double-slit with fixed slit separation. However, this method is only suitable for measurements with relatively small changes in beam size. With the development of the diffraction limited storage ring, the demand for high-precision measurement is becoming more and more urgent. Multi-frequency coherence measurement can overcome these limitations, but it is limited by the changing speed of double-slit. Purpose This study aims to improve the speed of multi-frequency coherence measurement by establishment of a slit separation rapid scanning system at Shanghai synchrotron radiation facility (SSRF). Methods Superimposed double single-slit is employed as the new double-slit mask in this system, and multi-thread technology is used to do fast data processing. Results The experimental results show that the time for one complete 10 points measurement is less than 3s with better accuracy compared with the traditional interferometer.[Conclusion] The new system greatly improves the speed of the multi-frequency coherence measurement and outperform the existing interferometer in terms of accuracy. Conclusion The new system greatly improves the speed of the multi-frequency coherence measurement and outperform the existing interferometer in terms of accuracy.  
        关键词：Spatial interferometer;Synchrotron radiation facility;Transverse beam size;Emittance;Silt spacing rapid scanning system   
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        发布时间：2021-05-19
      • Xin JIN,Jianjun WANG,Yiwen LI,Da HUANG,Chunming YANG,Fenggang BIAN,Jie WANG
        Vol. 41, Issue 8, Article number: 080102(2018) DOI: 10.11889/j.0253-3219.2018.hjs.41.080102
        摘要：Background Block copolymers can spontaneously self-assemble into various micro-scale morphologies under the various external fields, which have an extensive potential on the application of the electronics, information, chemistry and biology, etc. However, the self-assembly process is still a "black box", the understanding is still limited to the evolution of morphology during the varying external conditions. Purpose This study aims to investigate the self-assembly behavior of Poly(styrene)-block-poly (acrylic acid) (PS-b-PAA) in the temperature field by using in-situ synchrotron radiation small-angle X-ray scattering (SAXS). Methods SAXS experiments were performed on the BL16B1 beamline of Shanghai Synchrotron Radiation Facility (SSRF). Energy was selected as 10 keV and the wave length is 0.124 nm. 2D SAXS patterns were recorded by Mar165 CCD with pixel size of 79 μm×79 μm. A sample-to-detector distance of 1946 mm was chosen. The temperatures of the specimens were monitored by using a Linkam thermal stage THMS600 (Linkam scientific instruments). One-dimensional integrated intensity curves were obtained from 2D SAXS patterns by self-developed software. PS-b-PAAs (PS:PAA=3000:5000) were used directly as purchased from Sigma-Aldrich Inc. Results The in-situ SAXS experiment shows that the center of scattering peak was shifted with increasing temperature from q≈0.73 nm-1 to q≈0.39 nm-1, which was also accompanied by the varying of full width of half maximum, integral area, and maximum value of SAXS peak. A phase transition temperature was estimated as Tc=128℃ and the temperature width of transition is 5℃. Pair distance distribution function was used for the analysis of SAXS data. Conclusion With increasing temperature, the length of particle decreased gradually and body perforated, A rod-like shape with an undulating surface exists before the phase transition. At the temperature higher than Tc, the particle was degraded from the rod-like shape changes to a near-spherical shape still contains hole residue. The particles grow and gradually condense into a larger sphere with a diameter of~30 nm at the later stage.  
        关键词：Block copolymer;Self-assembly;SAXS;Synchrotron radiation   
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        发布时间：2021-05-19

        NUCLEAR PHYSICS, INTERDISCIPLINARY RESEARCH

      • Zhifeng LI,Qingtian LI,Beibei WANG,Yong HAN,Hui ZHANG,Zheng PENG,Jian LIU,Yimin LI,Zhi LIU
        Vol. 41, Issue 8, Article number: 080501(2018) DOI: 10.11889/j.0253-3219.2018.hjs.41.080501
        摘要：BackgroundThe oxygen vacancies concentration and thermal stability of CeO2 based catalysts play an important role in their catalytic performance. However, the effect of metal loading on oxygen vacancy and thermal stability remains ambiguous. Therefore, a comprehensive and systematic method for elucidating the oxygen vacancies and the strong synergistic metal-support interactions in CeO2 nanocrystals is desirable. PurposeThis work aims to determine the relationship between the lattice constant and the concentration of oxygen vacancies, and to highlight the strong synergistic metal-support interactions in CeO2 nanocrystals using bulk and surface characterization tools. MethodsThe samples were characterized by X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and inductively coupled plasma spectrometer (ICP). ResultsThe XRD results indicate that the lattice constant of annealed CeO2 was smaller than that of as-synthesized CeO2 due to the decrease in oxygen vacancy concentration. Therefore, a linear relationship between lattice constant and oxygen vacancy concentration is established. Compared with as-synthesized and annealed CeO2, Pt/CeO2 nanorods present higher oxygen vacancy concentrations. The XPS, XRD and ICP results show that Pt diffuse into the CeO2 during the annealing process. Hence, the strong synergistic metal-support interactions between Pt and CeO2 protect the Pt clusters from further oxidation to PtO2. ConclusionThe relationship between lattice constant and the concentration of oxygen vacancies in CeO2 shows that a decrease in lattice constant is related to the decrease in concentration of oxygen vacancies when CeO2 is annealed in dry air. Moreover, the Pt loading distorts the lattice structure of CeO2, thereby increasing its lattice strain and the lattice constant. Accordingly, Pt diffusion into CeO2 at high temperature is responsible for the improved thermal stability of oxygen vacancy and Pt/CeO2.  
        关键词：Cerium oxide;Pt loading;Oxygen vacancies;Lattice constant;Thermal stability   
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        发布时间：2021-05-19
      • Kai XIA,Ling HAN,Huating KONG,Qinglong YAN,Yu ZHANG,Ying ZHU
        Vol. 41, Issue 8, Article number: 080502(2018) DOI: 10.11889/j.0253-3219.2018.hjs.41.080502
        摘要：BackgroundDirect cellular delivery of CRISPR/Cas9 complexes is of great significance for genome editing, gene expression regulation, and DNA/RNA imaging. Electroporation is an important approach for the delivery of Cas9 ribonucleoproteins (RNP). PurposeThis study aims to screen the optimal electroporation condition for CRISPR/Cas9-mediated genome editing. MethodsSDS PAGE, Western bolt, Agarose gel electrophoresis and T7E1 cleavage assay were used to investigate the CRISPR/Cas9-mediated gene editing efficiency under various electroporation conditions. 3-(4, 5-dimethyl-2-thiazolyl)-2, 5-diphenyl-2-H-tetrazolium bromide (MTT) and Caspase-3 activity determination methods were used to investigate the biocompatibility of various electroporation conditions. ResultsWhen the voltage is 1 300 V, pulse number is 1, and pulse width is 30 ms, we get the optimal genome editing efficiency with low cellular toxicity. ConclusionOur work provides useful information of using CRISPR/Cas9 complexes for further biomedical applications.  
        关键词：Cas9 ribonucleoproteins;Electroporation condition;Direct delivery;Gene editing efficiency;Biocompatibility   
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        发布时间：2021-05-19

        NUCLEAR ENERGY SCIENCE AND ENGINEERING

      • Xuechao ZHAO,Xiangzhou CAI,Jingen CHEN
        Vol. 41, Issue 8, Article number: 080601(2018) DOI: 10.11889/j.0253-3219.2018.hjs.41.080601
        摘要：BackgroundAccelerator-driven subcritical molten salt reactor (ADS-MSR) has many unique advantages and features for advanced nuclear fuel utilization. PurposeThis study aims to analyze the influence of neutronics performance of the molten salt fuel in ADS. MethodsIn this work, the Monte Carlo N particle transport code (MCNP) program was employed to calculate the proton source efficiency, the neutron spectrum and the Th-U breeding in an accelerator driven subcritical molten salt reactor. ResultsMolten salt fuels will enhance the moderation to spallation neutrons and fission neutrons while improving the proton source efficiency. The moderating effect of molten salt reduces the Th-U breeding capability at the beginning of burnup, and the CR of FLi, FLiBe and oxide fuel were 1.023, 1.062 and 1.068 respectively. On the other side, with on-line refueling and fuel processing, the CR of FLi and FLiBe salt become higher than oxide fuel in the first year and 3rd year of the burnup, and can stabilize around 1.06 and 1.00 for a long period of time, respectively. ConclusionCompared to the oxide fuel, the FLi molten salt fuel has the better performance on Th-U breeding in an accelerator driven subcritical reactor.  
        关键词：Molten salt fuel;Proton efficiency;Th-U breeding;On-line processing   
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        发布时间：2021-05-19
      • Zhikang WAN,Xuehui AN,Peng ZHANG,Liuming YAN,Wenfeng WANG,Jinhui CHENG
        Vol. 41, Issue 8, Article number: 080602(2018) DOI: 10.11889/j.0253-3219.2018.hjs.41.080602
        摘要：BackgroundThe molten salt is used as the coolant of the molten salt reactor because of its stable chemical properties and excellent heat transfer performance. At the same time, the thermal stability of the molten salt also determines the stability of the molten salt reactor (MSR). In this paper, the effect of additives on the thermal stability of molten salt at high temperature was studied by selecting Solar salt (NaNO3-KNO3, 60%(wt)~40%(wt)) molten salt as a base salt and Na2CO3 as an additive. PurposeThis study aims to improve the working temperature range and high temperature thermal stability of Solar salt molten salt. MethodsThe effect of Na2CO3 on the working temperature range and thermal stability of Solar salt was studied by the simultaneous thermal analysis and the mass loss rate-time curve. The decomposition products of Solar salt were verified by chemical analysis and pH analysis. ResultsBy adding 1%(wt) Na2CO3, the working temperature range and thermal stability of the Solar salt molten salt were improved by 20 degree celsius and 3.2%, respectively. ConclusionThis study can provide a reference to the improvement of high temperature thermal stability of molten salt in MSR.  
        关键词：Solar salt;Thermal stability;Molten salt reactor   
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