最新刊期
      卷 42 ， 期 5 ， 2019

        SYNCHROTRON RADIATION TECHNOLOGY AND APPLICATIONS

      • “扫描相干衍射成像技术在生物和材料领域取得成功，多切片三维成像方法为高效低剂量成像开辟新路。”
        NIE Wei,XU Zijian,TAO Xulei,TAI Renzhong,ZHU Zhiyuan
        Vol. 42, Issue 5, (2019) DOI: 10.11889/j.0253-3219.2019.hjs.42.050101
        摘要：BackgroundPtychography technology has been applied widely nowadays, and has made great achievements in the fields of materials, energy and life sciences. Traditional Ptychography 3D imaging is based on the computational tomography technology with multi-angular projection which has the disadvantages of low-efficiency and high-dose. The emerging multi-slice 3D imaging approach opens up a new way for high-efficiency low-dose 3D imaging.PurposeThis study aims to improve the reconstruction convergence and imaging quality of the multi-slice ptychographic tomography with emphasis on the effect of the illumination divergence degree on the reconstructed image of this approach.MethodsFirst of all, a numerical simulation method was employed to optimize the relaxation parameters. Then the effect of divergence of incident X-ray on reconstruction quality of multi-slice method was investigated by simulation experiments. Finally, the reconstructed images were compared directly with the ground-truth original images, and an error metric was calculated for monitoring the convergence of the reconstruction and measuring the quality of the reconstructed image.ResultsIt was found that the higher the divergence degree of the incident beam, the faster the iterative reconstruction converges, and the better the reconstructed image quality.ConclusionThe choice and setting of the focusing optical devices are significant in multi-slice ptychographic tomography experiments, a zone-plate with a smaller outermost zone width or an X-ray beam with lower energy in such experiments are helpful to obtain a better imaging quality by using multi-slice 3D ptychography approach.  
        关键词：X-ray ptychography;Multi-slice 3D imaging;Incident X-ray divergence degree;Zone-plate focusing   
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        发布时间：2024-10-25
      • “在X射线层叠衍射成像技术领域，专家引入“动量”概念，开发了动量加速层叠衍射迭代引擎算法，有效解决了传统算法收敛停滞问题，显著提升了图像重建质量。”
        TAO Xulei,XU Zijian,WANG Chunpeng,TAI Renzhong
        Vol. 42, Issue 5, (2019) DOI: 10.11889/j.0253-3219.2019.hjs.42.050102
        摘要：BackgroundThe image retrieval algorithm of ptychography is a kind of conventional gradient descent algorithm. This algorithm begins with a set of guessing functions, and the signals collected in the experiment are continuously input into the iteration process to achieve final convergence. However the reconstructed process often falls into stagnation because of the low gradient around the local minima and the extent of the gradient descent is too small.PurposeThis study aims to solve the convergence stagnation problem of conventional gradient descent algorithm by using momentum ptychographical iterative engine (mPIE).MethodsThe concept of "momentum" was introduced into the ptychography algorithm to update conventional algorithm, called the momentum ptychographical iterative engine (mPIE). Adding momentum to an algorithm means that the iterative process has the characteristic of inertance. The extent of gradient descent relies on the previous steps and the gradient of current step. With the momentum, convergence can escape stagnation, and the reconstructed process can continue even around the local minima with a gradient is very small. The same set of coherent diffraction imaging experimental data was used to test the reconstructed image quality of mPIE algorithm and compare with that of extending ptychographical iterative engine (ePIE) algorithm.ResultsThe experimental results showed that mPIE algorithm outperformed ePIE algorithm with smaller convergence value of objective function, and better final reconstructed image quality.ConclusionThe result indicates that a better reconstructed result can be achieved with mPIE algorithm compared with the traditional ePIE algorithm.  
        关键词：X-ray ptychography;Mixed state;X-ray microscopy;Iterative phase retrieval algorithm   
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        发布时间：2024-10-25
      • “上海同步辐射光源采用机械夹持密封水冷晶体，有效避免晶体剥离脱落，保障光束线稳定运行。”
        SONG Li,FAN Yichen,JIN Limin,XU Zhongmin
        Vol. 42, Issue 5, (2019) DOI: 10.11889/j.0253-3219.2019.hjs.42.050103
        摘要：BackgroundThe water-cooled crystals at Shanghai synchrotron radiation facility (SSRF) are currently vacuum sealed by colloid bonding. In high-energy synchrotron radiation environments, the colloid is prone to failure that will cause the crystal to flake off.PurposeThis study aims to introduce the recommended sealing method to avoid the above risks.MethodsWater-cooled crystal sealing structure was applied to mechanical clamping mechanism. Experimental tests were conducted to obtain surface error in meridian direction of crystal caused by mechanical load and rocking curve. In addition, the water pressure resistance test and leak detection test of the mechanically sealed water-cooled crystal were carried out.ResultsThe slope error of the crystal caused by mechanical load is approximately 3.55 μrad (root mean square) which satisfies the performance requirements. Rocking curve test shows that the value of full width at half maximum (FWHM) of the water-cooled crystal of the mechanical sealing structure is 11.86″ which is nearly the same as the FWHM value of 12.24″ of the water-cooled crystal under the original bonding mode, and the difference is about 3%. The results of water pressure resistance and leak detection tests show that the sealing performance of the crystal assembly structure is pretty good.ConclusionsThe water-cooled crystal sealed by mechanical clamping can meet the performance requirements, and it can effectively avoid the occurrence of peeling off event of crystal during work, and provided the necessary guarantee for the stable operation of beam lines at SSRF.  
        关键词：Synchrotron radiation;Water-cooled crystal;Mechanical sealing;Slope error;Rocking curve   
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        发布时间：2024-10-25

        ACCELERATOR, RAY TECHNOLOGY AND APPLICATIONS

      • “中国散裂中子源加速器高能段采用先进Quadrupole-D磁铁，加工精度高，运行稳定，为加速器研究提供新方向。”
        LI Bo,LIU Huachang,GONG Keyun,CHEN Qiang,WANG Yun,WU Xiaolei,LI Ahong
        Vol. 42, Issue 5, (2019) DOI: 10.11889/j.0253-3219.2019.hjs.42.050201
        摘要：BackgroundHigh energy section of drift tube linac (DTL) for China spallation neutron source (CSNS) is composed of 9 m cavity and 27 Quadrupole-D drift tubes, it is used to provide energy gain from 60 MeV to 80 MeV. The quadrupole-D magnet coil adopted SAKAE structure with compact and small aperture feature, maximum exciting current is 396 A. The drift tube shell is made of oxygen free copper and welded by the electron beam welding (EBW). High accuracy processing and magnetic measurements are required for this compact and small aperture drift tube.PurposeThe study aims to develop such a compact, small aperture and long effective length quadrupole-D magnet with high accuracy processing and magnetic measurement of a strong beam proton accelerator, and cone structure is first used for domestic drift tubes.MethodsQuadrupole-D magnet is designed and optimized by code. Hall measurement and rotating coil measurement are carried out after the magnet is completed to keep the magnet qualified. Then, rotating coil measuremengts were carried out during the machining process to provide processing dimensions, and a precision rotating coil measurement system designed for drift tuning magnetic measurement is used to keep the drift tube qualified.ResultsQuadrupole-D magnet and drift tube were developed for CSNS DTL, the effective length deviation is 2.6%, the integral field deviation is 2.2%, the field gradient deviation is 0.4% and the center deviation is better than 0.003, the higher-order harmonics are less than 3.5×10-3, 24 drift tubes magnetic center deviation is less than 0.03 mm, the magnet is in good condition after 9 h of running test.ConclusionDTL of CSNS run well with Quadrupole-D drift tubes, which are important for low energy intense beam proton accelerator.  
        关键词：Drift tube;Quadrupole magnet;Hall measurement;Rotating coil measurement;Integral field;Higher-order harmonics   
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        发布时间：2024-10-25

        NUCLEAR ELECTRONICS AND INSTRUMENTATION

      • “在核物理实验中，为解决传感器网络能量不均衡问题，提出了一种电源系统改造方案，可降低节点能耗78%，延长系统寿命5倍。”
        LIU Xuesong,WU Jie
        Vol. 42, Issue 5, (2019) DOI: 10.11889/j.0253-3219.2019.hjs.42.050401
        摘要：BackgroundIn the data acquisition system for a nuclear physics experiment, the energy consumption of each acquisition node of wireless sensor networks is not balanced, and the energy utilization of the system is insufficient, which cannot satisfy the task of reliable data acquisition for a long time.PurposeThis study aims to solve the common problem of energy imbalance of wireless sensor networks, and put forward a transformation scheme of power supply system for wireless sensor networks.MethodsOn the basis of reserving wireless sensor communication, the scheme achieves two improvements by adding power lines between sensor nodes. Firstly, the energy transfer channels between nodes are increased to solve the problem of unbalanced energy consumption between nodes. Secondly, on the basis of energy balance, sensor nodes communicate with the optimal energy scheme to avoid energy waste caused by frequent clusters in traditional wireless sensor networks.ResultsThe results show that this method can prolong the life of the system about five times at the cost of connecting a few power lines.ConclusionThe simulation results show that compared with clustering protocol, this scheme can reduce the average power consumption of nodes by 78% and prolong the system life by about 5 times.  
        关键词：Wireless sensor network;Energy balance;Power line connected;Energy optimal routing   
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        发布时间：2024-10-25
      • “在高压充电电源领域，专家研制了基于平面绝缘芯变压器结构的电源，并验证了二极管功率损耗，为选择二极管提供原则。”
        HUANG Maomao,LI Rui,LI Deming,WEI Jukui,WU Wanfeng,ZHU Yanyan
        Vol. 42, Issue 5, (2019) DOI: 10.11889/j.0253-3219.2019.hjs.42.050402
        摘要：BackgroundHigh voltage charging power supply is developed from the requirement of pulse modulation high voltage power supply. The power supply structure consists of a planar insulated core transformer in series with multiple output coils. Therefore, many rectifier diodes are used accordingly. Critical power loss of rectifier diodes has direct influence on the temperature rise of sealed output structure of power supply.PurposeThis study aims to reduce the influence of diode power loss according to the operating characteristics of the diode and determine the selection principle of the diode.MethodsBased on the relationship between the current turn-off slope and reverse recovery peak current of various diodes, circuit simulation and parametric analysis of common diodes, fast recovery diodes and silicon carbide Schottky diodes were carried out, silicon carbide diodes C4D05120E (1 200 V 9 A) was selected as high-voltage rectifier diode to design high voltage rectifier circuit.ResultsThe high voltage power supply operates at 70% load, and the temperature rise caused by the loss of power of silicon carbide diode is within 2°.ConclusionThe application of silicon carbide diode improves the power loss of high voltage power rectifier diodes. With the increase of switching frequency of high voltage power supply, the advantages of silicon carbide diode will be more obvious.high voltage power supply, the advantages of silicon carbide diode will be more obvious.  
        关键词：Planar transformer;LLC resonance;Silicon carbide diode;High voltage power supply   
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        发布时间：2024-10-25
      • “在核探测器前端电子学领域，新型低压差电压稳压器结构提升电源效率，负载瞬态恢复时间小于400纳秒，为北京谱议CGEM探测器和LHC第三代像素探测器提供电源供电。”
        CHAI Junying,JIANG Xiaoshan,ZHANG Yongjie,DONG Yongwei,SHI Feng,LI Lu,CHENG Weishuai,LENG Chongyang,WANG Zheng,WU Bobing
        Vol. 42, Issue 5, (2019) DOI: 10.11889/j.0253-3219.2019.hjs.42.050403
        摘要：BackgroundAs nuclear detectors become more and more channels with smaller and smaller volume, front-end electronics tends to adopt CMOS (complementary metal oxide semiconductor) ASIC designs. The ASIC has low power consumption, small parasitic capacitance and small size, hence the power supply has a tendency to integrate at the front end.PurposeThis study aims to design a new kind of low-dropout (LDO) structure that is suitable for the front-end power supply of nuclear detectors and robust to the process and has no capacitance.MethodsBased on the classical low-dropout (LDO) structure, complementary metal oxide semiconductor (CMOS) process using IBM 130 nm process was employed to realize the new LDO structure. A novel LDO robust to external capacitance value and equivalent series resistance (ESR) was obtained. This comprehensive performance of the design has the advantage of strong robustnes to load capacitance, hence is siutable for the front end of the nuclear detector.ResultsIts recovery time of the transient response is less than 400 ns and the drop out voltage is below 200 mV. All these futures are especially suitable for the front end, which is often a hybrid circuit.ConclusionThis design is used for the cylindrical gas electron multipliers (CGEM) of BESIII update project, it is also the technical reserve for the power supply of third generation pixel detector in large hadron collider (LHC).  
        关键词：LDO;Front-end;ASIC   
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        发布时间：2024-10-25

        NUCLEAR PHYSICS, INTERDISCIPLINARY RESEARCH

      • “在半导体材料领域，专家利用60Co源γ射线辐照4H-SiC肖特基二极管探测器，观察辐照对其电学特性及α粒子响应能量分辨率的影响。”
        HAN Chong,CUI Xingzhu,LIANG Xiaohua,LIANG Hongwei,XIA Xiaochuan,YANG Cun,YE Xin,TANG Jilong,WANG Dengkui,WEI Zhipeng
        Vol. 42, Issue 5, (2019) DOI: 10.11889/j.0253-3219.2019.hjs.42.050501
        摘要：BackgroundSilicon carbide is considered as a representative wide band gap semiconductor material for high temperature and radiation resistance devices due to its physical properties of wide band gap and high threshold displacement energy.PurposeThis study aims to investigate the effects of irradiation on the electrical properties of the 4H-SiC Schottky diode detector and the energy resolution of the α-particle response.MethodsThe 4H-SiC Schottky diode detector was irradiated with 60Co source gamma-rays. The forward current and reverse bias voltage of the detector were observed. [Results & Conlusion] After γ-rays irradiation with total absorbed dose of 1 000 kGy, the forward current of the detector decreases by three orders of magnitude compared with that before irradiation. The reverse current value does not change at 0~120 V bias voltage. When the reverse bias voltage is higher than 120 V, the reverse current value changes obviously. At the same time, there is no significant change in the energy resolution of α-particle before and after irradiation.  
        关键词：4H-SiC;Schottky diode;γ-rays;Detector;Electrical properties;Energy resolution   
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        发布时间：2024-10-25
      • “在中枢神经系统诊疗领域，核酸分子递送技术取得新进展，为开发高效安全载体提供新思路。”
        ZHOU Haibin,LI Jiang,HU Ji,WANG Lihua
        Vol. 42, Issue 5, (2019) DOI: 10.11889/j.0253-3219.2019.hjs.42.050502
        摘要：BackgroundThe use of nucleic acid in the diagnosis and treatment of diseases and injuries of the central nervous system (CNS) has shown great promise in recent years. However, transporting nucleic acids to CNS with highly complex structure and barriers remains challenging.PurposeThis study aims to give a comprehensive review of efficient and low-toxic delivery strategies of nucleic acids towards central nervous system for theranostic applications.MethodsBy means of literature review, the progress in developing nucleic acid delivery strategies for applications in CNS in recent years are analyzed. These strategies can be categorized into viral vector-based, non-viral carrier-based, and carrier-free. We also discussed their advantages and limitations, and provided suggestions for the future development of novel strategies.Results & ConclusionThese strategies have been shown to enhance the structural stability and cell uptake of the nucleic acids, thus improving the theranostic performance.  
        关键词：Viral vectors;Non-viral vectors;Central nervous system;Gene therapy   
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        发布时间：2024-10-25

        NUCLEAR ENERGY SCIENCE AND ENGINEERING

      • “在核电安全领域，专家利用MELCOR2.2程序对安全壳内氢气点燃浓度限值进行敏感性分析，为消除可燃气体潜在威胁提供解决方案。”
        SHI Xingwei,SHI Qiang,MA Guoqiang,SONG Wei,JIA Bin,ZUO Jiaxu,LIU Fudong
        Vol. 42, Issue 5, (2019) DOI: 10.11889/j.0253-3219.2019.hjs.42.050601
        摘要：BackgroundIn severe accidents, the oxidation behavior of fuel cladding and other metallic materials in core region with steam, and the molten corium-concrete interaction (MCCI) are important source items for releasing hydrogen.PurposeThis study aims to investigate the sensitivity of the hydrogen mole fraction limit for ignition in the containment to prevent the hydrogen deflagration and explosion.MethodsThe integrated contamination model has been built systemically in large power passive pressurized-water reactor (PWR) using the latest version of MELCOR2.2 code, and the sensitivity analysis of hydrogen molar fraction limit for ignition has been carried out.ResultsThe analysis results show that: 1) the higher hydrogen mole fraction limit setting the more obvious pressure peak generated by a single combustion; it will cause the hydrogen deflagration and detonation if the value exceeds the mole fraction limit; 2) the hydrogen ignition is affected by other noncondensible gases to a certain extent. The increase of carbon monoxide molar fraction escalates the hydrogen ignition and, conversely, the carbon dioxide and steam dilute the flammable gases.ConclusionHydrogen ignition is greatly affected by the ignition limit of hydrogen molar fraction, and as an important factor, the other noncondensible gases components in containment are non-negligible. Therefore, it is crucial to combining and diluting the combustible gases for eliminating the potential risk in containment.  
        关键词：MELCOR2.2;Hydrogen;Mole fraction limit for ignition;Severe accident;Sensitivity analysis   
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      • “在高温熔盐泵轴承研究领域，专家采用有限体积法分析了不同织构对轴承承载能力的影响，优化出最佳十字形织构，为设计提供理论指导。”
        CHEN Jun,JIANG Xinyue,LIN Liangcheng,FU Yuan
        Vol. 42, Issue 5, (2019) DOI: 10.11889/j.0253-3219.2019.hjs.42.050602
        摘要：BackgroundThe high temperature molten salt pump is the heart of the molten salt coolant thermal circuit. At present, the molten salt pump used in molten salt reactor adopts cantilever structure, and its long shaft needs to be supported by sliding bearings in molten salt. It is an effective method to improve the supporting capability and improve the tribological property by making texture of the inner surface of the sleeve a smooth one.PurposeThis study aims at analysis of the surface texture finned high temperature molten salt pump.MethodsThe finite volume method was employed to study the bearing of high temperature molten salt pump. Smooth bearing was taken as contrast term, the bearing capacity of different textures such as non-texture, long texture, circular texture, square texture and cross-shaped texture was analyzed.ResultsBy optimizing the shape, density and depth of texture, the bearing capacity can be improved. Cross-shaped texture with a length of 8 mm, a width of 3 mm and a depth of 20 μm shows the best bearing capacity.ConclusionAmong the four textures studied in this paper, the cross-shaped texture has the best bearing capacity.  
        关键词：High temperature molten salt pump;Sliding bearing;Surface texture;Molten salt reactor   
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      • “在工程领域，研究了竖直矩形窄流道在过冷沸腾条件下的换热特性，为提高换热效率提供参考。”
        CHENG Ning,GUO Yun,PENG Changhong,ZHANG Yong
        Vol. 42, Issue 5, (2019) DOI: 10.11889/j.0253-3219.2019.hjs.42.050603
        摘要：BackgroundVertical rectangular narrow flow channel has been widely used in engineering field due to its good heat transfer effect and compact structure. While the study on onset of nucleate boiling (ONB) site in vertical rectangular flow channels is very limited.PurposeThis study aims to figure out the effects of inlet fluid temperature, mass flux and channel height by experiment in the vertical rectangular flow channels with 1.8 mm and 2.8 mm gaps respectively.MethodsVisualization method was employed to observe the bubble growth and wall superheat at the ONB point under subcooled boiling condition. Deionized water was used as the working medium, a high-speed camera was used to photograph the growth process of bubbles and the temperature of the backing plate was recorded by thermocouples.ResultsIt was found that the inlet temperature, mass flux and channel height had the same effects on the bubble growth and the wall superheat at the ONB point in the two flow channels. The bubble size of ONB point in two flow channels increases with the increase of the inlet temperature, and decreases with the increase of mass flow rate.ConclusionsUnder the condition of constant mass flow rate, the flow channel height has no significant effect on the bubble size at ONB point. The superheat degree of the ONB point in two flow channels decreases with the increase of inlet temperature and increases with the increase of the mass flow rate. The relationship between the wall superheat of ONB point and the heat flux is not affected by the flow path height and it can be predicted by the empirical formula in literature.  
        关键词：Vertical rectangular flow channel;Visual experiment;Onset of nucleate boiling point;Bubble growth;Wall superheat   
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      • “在聚变实验装置领域，专家利用EAST装置对金属材料进行活化实验，分析了放射性核素，为确保人员剂量安全提供解决方案。”
        HAN Liangwen,LI Kai,ZHONG Guoqiang,XIAO Min,XU Yu,HU Liqun
        Vol. 42, Issue 5, (2019) DOI: 10.11889/j.0253-3219.2019.hjs.42.050604
        摘要：BackgroundThe radiation dose mainly comes from the activation of different metal materials after fusion experimental facility shut down.PurposeThis study aims to analyze the radionuclides generated by activated materials, so as to help ensure the safety of personal doses during equipment maintenance.MethodsActivation experiments of the common metal materials were carried out. Associating with total peak area method, Wasson method and curve fitting method, the energy spectra measured by high purity germanium γ spectrometer were analyzed.ResultsThe results show that the irradiated metal samples contain artificial radionuclides, and the detector count rate is closely related to the irradiation position. Wasson peak area method has higher computational accuracy for weak peak area compared with other two methods.ConclusionsIf the activation of the bio-shielded wall is not taken into account, the radiation dose in the hall of the EAST facility is contributed mainly by 56Mn, 99Mo, 76As, 64Cu, 51Cr, 58Co, 59Fe, 54Mn, 60Co and et al radionuclides after device shut down.  
        关键词：Tokamak;Material activation;Radionuclide   
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