最新刊期
卷 42 ， 期 8 ， 2019
- “在同步辐射光源领域，研究人员采用拉普拉斯算子和阈值分割法，提高了荧光靶探测器的光斑定位精度。”摘要：BackgroundFluorescence screen detector is an important spot position measuring device. The position of the spot is mainly measured by the fluorescent screen image. However, due to the dispersion of the spot, the edge of the spot in the image becomes blurred, which will affect the position measurement.PurposeThis study aims to improve the accuracy of spot position measurement.MethodsThe Laplacian operator was used to enhance the fluorescent screen image, and then the threshold segmentation method was applied to finding the edge position of the spot. Accuracy comparison of this approach with canny edge detection algorithm was performed on a real fluorescent spot image.ResultsTest results show that this method can be used to accurately locate the spot position from fluorescent image with better accuracy compared with canny algorithm.ConclusionsLaplace enhancement can be applied to improving position measurement resolution of fluorescence screen detector.关键词：Synchrotron radiation;Fluorescence screen;Image processing;Laplace enhancement
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发布时间：2024-10-25 - “在串行飞秒晶体学领域，机器学习方法可有效筛选分类数据，提高XFEL实验数据筛选效率。”摘要：BackgroundA number of machine learning-based methods have been developed for classification screening of serial femtosecond crystallography (SFX) data.PurposeThis study aims to improve the data analysis technique to obtain more effectively screen SFX data from X-ray free electron lasers (XFELS).MethodsFirst of all, experimental data of different samples were taken for screening and categorizing, Automatic image processing and convolutional neural network were employed for detection of Bragg points in diffraction patterns of crystals, hence, invalid experimental data were filtered out. Then, simulation was performed as the benchmark for many experiments. Finally, the reasons for the different accuracy of experimental prediction results were analyzed.ResultsAmong many methods, convolutional neural network can obtain higher prediction accuracy whilst linear method only has better accuracy for some samples, but both of them are superior to traditional point-finding algorithm.ConclusionsThis approach provides an effective and convenient data screening tool for X-ray FEL experiments.关键词：Free electron laser;Serial crystallography;Machine learning
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发布时间：2024-10-25
SYNCHROTRON RADIATION TECHNOLOGY AND APPLICATIONS
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Radio frequency design and multipacting study of superconducting elliptical cavity for CSNS-II linac AI导读
“中国散裂中子源二期升级，直线加速器能量增益提升至300 MeV，采用全超导结构，优化了椭球腔高频参数和几何尺寸，加速梯度8 MV∙m-1以上抑制二次电子倍增。”摘要：BackgroundUpgrade of China spallation neutron source (CSNS-II) from 100 kW to 500 kW is being developed. Superconducting spoke cavity and elliptical cavity are used to upgrade the linac from 80 MeV to 300 MeV, hence the 648 MHz β=0.6 elliptical cavity needs to be studied.PurposeThe study aims to develop this β=0.6 elliptical cavity for CSNS-II linac upgrade, which provides energy gain from 150 MeV to 300 MeV.MethodsWith software computer simulation technology (CST), the cavity geometry and high frequency parameters of ellipsoidal cavity were optimized. Multipacting and Lorentz force were analyzed with these optimized data.ResultsThe field flat of this elliptical cavity was optimized to 98.2% while the Epk/Eacc and Bpk/Eacc reached 2.70 and 4.89, respectively. With modified the shape of the equator the growth rate of multipacting decresed under the same radio frequency (RF) parameters, and multipacting was suppressed totally when the accelerated gradient was over 8 MV∙m-1.ConclusionThe RF parameters of this 648 MHz β=0.6 elliptical cavity after optimization design could meet the requirements of CSNS-II linac upgrade very well.关键词：Superconducting;Elliptical cavity;Multipacting;Lorentz force- 366
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发布时间：2024-10-25 - “在强流重离子加速器领域，专家提出了加速器电源在线标定方法，有效保证数字电源精度，为HIAF建设提供技术保障。”摘要：BackgroundAccuracy and consistency of the excitation current are very important for high intensity heavy-ion accelerators. Usually, the long-term operation of magnetic field power supply, aging and zero drift of devices, ambient temperature, electromagnetic interference and other factors will lead to the decline of the current accuracy of some power supplies, thence affecting the consistency of current, which has a greater impact on the debugging efficiency and beam quality of high intensity heavy-ion accelerators.PurposeThis study aims to improve and ensure the debugging efficiency and beam quality of high intensity heavy-ion accelerators.MethodsAn on-line calibration method for accelerator power supply was proposed by using system of chip (SOC). The factors affecting current accuracy are discussed and analyzed. The calibration principle was introduced and the method was implemented on Cyclone V SOC platform. Finally, experimental test was carried out to verify this calibration method.Results & ConclusionsThe experimental results verify the effectiveness of the method that can effectively ensure the accuracy of the digital power supply of the accelerator, and provide technical support for the construction of the "12th Five-Year Plan" high intensity heavy-ion accelerator facility (HIAF).关键词：Current calibration;Current accuracy;Consistency;ARM;HPS;Linux
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发布时间：2024-10-25
ACCELERATOR, RAY TECHNOLOGY AND APPLICATIONS
- “在放射性药物领域，研究人员建立了快速可靠的18F-氟化钠放射化学纯度分析方法，为质量控制提供解决方案。”摘要：BackgroundSodium 18F-fluoride Injection is a radioactive diagnostic agent for positron emission tomography (PET) for bone imaging to identify areas of altered bone formation activity. Radiochemical purity testing is one of the quality control items.PurposeThis study aims to establish a convenient, rapid and reliable method for the determination of radiochemical purity of sodium 18F-fluoride injection.MethodsThis study focused on the establishment of radiochemical purity test paper chromatography method, and verified by method precision, system precision, linearity and durability.ResultsThe results showed that the analytical method of radiochemical purity was the Whatman No.1 paper treated with 2% sodium acetate solution as chromatography paper and 50% methanol as the eluent, after separation, the radiochemical purity was tested by radioactive thin layer scanner. The verified results showed that these methods met the quality control requirements, the chemical purity is 0.65~0.85 of Rf and the precision is 0.15%.ConclusionsThis study established a convenient, rapid and reliable sodium 18F-fluoride physicochemical property test methods for radiochemical purity test.关键词：Sodium 18F-fluoride;Radiochemical purity;Paper chromatography method
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发布时间：2024-10-25 - “高岭土对铀(VI)吸附性能良好，6小时达平衡，最佳初始浓度60μg/mL，pH值5时吸附效果最大。”摘要：BackgroundKaolin is one of clay rocks that can be used to adsorb uranium (VI), but performance has hardly studied.PurposeThis study aims at the effects of adsorption time, initial U(VI) concentration, adsorption quality, pH value, ion species and humic acid quality on kaolin adsorption U(VI).MethodsKaolin 200 mesh, drying reserve, and formation of U(VI) solution with 1 g∙L-1 mass concentration by U3O8 were prepared. Analytically pure reagents of known content were used to config deionized water and ionic solution with different pH values. Then, experimental method of static adsorption was used for the study.ResultsKaolin has good adsorption performance for U(VI), and it reaches equilibrium at 6 h. The optimum concentration of U(VI) is 60 μg∙mL-1. The best adsorbent mass is 0.01 g. When the pH value increases, the adsorption effect of kaolin on U(VI) increases first and then decreases, when pH=5, the adsorption effect is the greatest. In the solution, K+, NO3-, Na+ and SO42- have little effect on the adsorption of U(VI). Mg2+, CO32- and HCO3- have an inhibitory effect on the adsorption of U(VI), which is not conducive to adsorption. Increasing the quality of the humic acid in the solution inhibits the U(VI) adsorption of the kaolin.ConclusionsThe quasi-secondary kinetic model can better describe the adsorption of U(VI) on kaolin than the quasi-first-order kinetic model. This experiment provides a theoretical basis for kaolin as a backfill material for radioactive nuclear waste.关键词：Kaolin;U(VI);Adsorption ability;Kinetic model
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发布时间：2024-10-25 - “在医学成像领域，研究人员采用固相合成法合成新型GnRH衍生物，并利用［18F］AlF标记法自动化标记，成功在PC-3前列腺肿瘤模型中实现小动物PET/CT显像。这一成果为前列腺癌的诊断和治疗提供了新思路。”摘要：[Backgroud] Gonadotropin releasing hormone (GnRH) receptor is overexpressed in many human tumors and is currently used as a target for molecular imaging.PurposeThis study aims to design and synthesize a new 18F-labeled GnRH peptide by automatic radiosynthesis for preliminary Micro-PET/CT imaging.Methods[18F]AlF-NOTA-P-L-Lys6-GnRH was automated radiolabeled with 18F by using Al18F complex on the modified PET-MF-2V-IT-I synthesis module. The stability of [18F]AlF-NOTA-P-L-Lys6-GnRH was incubated in phosphate buffer saline (PBS) at 37 ºC and the octanol/water partition coefficient was studied. The dynamic Micro-positron emission tomography (PET) study of [18F]AlF-NOTA-P-L-Lys6-GnRH in nude mice bearing PC-3 cancer was carried out.ResultsThe total radiochemical synthesis and purification of [18F]AlF-NOTA-P-L-Lys6-GnRH was completed in 35 min with a decay-corrected yield of (25±6)% and a specific activity of 8~30 GBq∙µmol-1 (n=6). The logP value of [18F]AlF-NOTA-P-L-Lys6-GnRH was -2.70±0.06 and the tracer was stable in phosphate-buffered saline for 2 h. Dynamic PET imaging analysis revealed that [18F]AlF-NOTA-P-L-Lys6-GnRH was clearly delineated in PC-3 xenografted tumor with high tumor-to-muscle ratios and excreted mainly through the kidneys.Conclusion[18F]AlF-NOTA-P-L-Lys6-GnRH was an efficient automated production of commercially available synthetic modules that could be used as a potential PET tracer for the imaging PC-3 prostate tumors.关键词：[18F]AlF-NOTA-P-L-Lys6-GnRH;GnRH;Automated radiosynthesis;Micro-PET/CT
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发布时间：2024-10-25 - “在高放射性废物处置领域，研究了239Pu在青海大柴旦粘土岩中的吸附行为，发现粘土对239Pu吸附影响大，吸附分配系数随时间、pH和液固比变化。”摘要：BackgroundThe research on clay rocks is still in exploration stage in selection of surrounding rock types for high-level radiation waste disposal.PurposeThis study aims to get the adsorption characteristics of 239Pu in Dachaidan clay rocks in Qinghai.MethodsClay rock samples were kept contact with known concentration of radionuclides in aqueous solution for a long time under oscillation until the concentration of radionuclides in aqueous solution did not change. Then, the adsorption behavior of 239Pu in clay rocks was investigated by the static adsorption experiment using appropriate measuring instruments.ResultsThe experimental results show that the sorption distribution coefficient of 239Pu in clay gradually increased with the adsorption time extends until it become a constant, and the measured adsorption equilibrium time of 239Pu in clay rocks is 2 days.ConclusionThe adsorption distribution coefficient of 239Pu in clay increases with the increase of pH value and decrease of liquid-solid ratio. It also increases firstly the increase of the initial concentration of 239Pu, and then decreases thereafter.关键词：239Pu;Clay rocks;Adsorption;Radionuclide migration
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发布时间：2024-10-25
NUCLEAR CHEMISTRY, RADIOCHEMISTRY, RADIOPHARMACEUTICALS AND NUCLEAR MEDICINE
- “在核辐射探测领域，研究者设计了三NaI（Tl）晶体探测器系统，并通过实验验证了其在远距离探测137Cs源时的有效性，为提高源定位精度提供了新方法。”摘要：BackgroundWith the wide application of radioactive sources and radioactive materials, the probability of losing radioactive source accidents is increasing.PurposeThis study aims to locate lost radioactive sources by using three gamma ray directional detectors.MethodsA gamma ray detection system consisting of three NaI(Tl) crystals was designed. The relationship between the full-energy peak ratio of the three NaI (Tl) detectors in the 137Cs radiation field as a function of distance and incident particle direction was studied by simulation and experiment.ResultsThe results show that in the case of long-range detection, the full-energy peak ratio method can effectively eliminate the influence of the source-detector spacing on the angular resolution. For the 1.36×106 Bq 137Cs source at the distance of about 2.58 m, maximum angular deviation of measurement is 1.72° or less, and the relative positional deviation is 3.71%.ConclusionsThe designed three NaI(Tl) crystal detector has stable angular resolution in a certain range and can distinguish the incident direction of rays.关键词：Source location;Three NaI(Tl) crystal detector;Full-energy peak ratio method
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发布时间：2024-10-25
NUCLEAR ELECTRONICS AND INSTRUMENTATION
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Band engineering of graphene: manganese intercalation by alloying with germanium substrate 封面论文 AI导读
“在石墨烯能带工程领域，科学家成功在石墨烯和锗衬底间插入二维Mn-Ge合金岛，为改变石墨烯能带结构提供新方法。”摘要：BackgroundIt is essential to introduce a bandgap in graphene or its heterojunctions in the field of band engineering.PurposeThis study aims to intercalate two-dimensional Mn-Ge alloy island between graphene and the Ge(110) substrate and modify the electronic state of graphene.MethodsThe atomic structure and low-energy electronic excitation were studied by scanning tunneling microscopy (STM).ResultsWe found one-dimensional nanowires and two-dimensional planar islands in samples with different graphene coverage. Without graphene protection, two-dimensional alloy islands can grow into three-dimensional wedges. The intercalation of one-dimensional nanowires and two-dimensional planar islands opens an energy gaps of 400 meV and 200 meV respectively.ConclusionsMn is intercalated to the graphene/Ge(110) through the edge of the graphene island by alloying with germanium. The open energy gap provides a feasible method for engineering the band structure of graphene.关键词：Graphene;Scanning tunneling microscopy/spectroscopy;Intercalation;Band engineering- 323
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发布时间：2024-10-25
NUCLEAR PHYSICS, INTERDISCIPLINARY RESEARCH
- “在核能领域，碳化硅复合材料燃料棒在失水事故中表现出优异性能，能有效延缓事故进程。”摘要：BackgroundWith low thermal conductivity, low neutron absorption cross section, good corrosion resistance and maintenance of strength in high temperature, silicon carbide (SiC) continuous fiber-reinforced SiC-matrix composites (SiCf/SiC) is one of the candidate materials of accident tolerant fuel (ATF).PurposeThis study aims at the comprehensive performance of fuel rod with SiCf/SiC cladding under loss of coolant accident (LOCA) condition.MethodsThe material properties of SiCf/SiC were fitted based on open access experimental data. By using FRATRAN, the performance differences between SiCf/SiC cladding and Zr4 cladding under the same condition was achieved.ResultsThese material formulas and methods could be preliminary used in the work of SiCf/SiC fuel rod performance analysis.ConclusionThe analysis shows that the rupture time of SiCf/SiC cladding fuel rod is longer and the average temperature is lower, which could effectively delay the occurrence of accidents.关键词：Fuel rod;SiCf/SiC;Cladding;LOCA
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发布时间：2024-10-25 - “在加速器驱动次临界系统领域，我国专家建立了基于外中子源强度的CIADS堆芯控制响应模型，为保证反应堆瞬态安全性提供解决方案。”摘要：BackgroundAccelerator driven subcritical system (ADS) can be used for power generation, proliferation and transmutation. China initiative accelerator driven system (CIADS) is a self-designed ADS research facility in China. It only relies on the intensity of neutron source outside the accelerator to regulate the core power.PurposeThis study aims to accurately regulate power in transient conditions to ensure the transient safety of the reactor based on the strength of external neutron source.MethodsThe lumped parameter method was used to establish the core nonlinear model of CIADS, and the micro-disturbance linearization method was used to linearize the core nonlinear model. Dual-input and dual-output core state space model was established, and core power fuzzy proportional integral derivative (PID) controller was designed to carry out disturbance control simulation to obtain the core control response characteristics of CIADS.Results & ConclusionThe simulation results show that the use of fuzzy PID controller can achieve good control of core relative power under the different external neutron source relative intensity disturbance or core inlet temperature disturbance.关键词：External neutron source relative intensity;Accelerator driven subcritical system;Core power;Fuzzy PID controller
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发布时间：2024-10-25 - “在核反应堆棒束燃料组件研究领域，专家设计了远心光路粒子图像测速系统，有效降低了图像畸变，为定位格架下游横流可视化测量提供了解决方案。”摘要：BackgroundMixing vanes are set on the spacer grids of bundle fuel assembly to promote the lateral mixing of pressurized water reactors (PWRs). Hence, the lateral flow downstream of the spacer grids is an important element to measure its thermal-hydraulic performance.PurposeThe study aims to tackle the challenge of measuring lateral flow using visualization method.MethodsA telecentric optical system was employed in the particle image velocimetry (PIV) measurement to efficiently reduce the distortion of the image. In addition, the fluorinated ethylene propylene (FEP) tube was utilized as the matched-refractive-index material of the work fluid in the measurement area to minimize the focusing effect after the transparent rods and realize the uniform illumination of the whole section of the rod bundle. Calibration and lateral flow measurement were conducted to evaluate its performance.ResultsExperimential results show that the lateral flow and vortices can be well obtained on the whole cross section of the 5×5 rod bundle by PIV telecentric measurement.ConclusionsThe measured flow fields indicates that the dominant effect of the mixing vanes on the lateral flow 5Dh downstream and its effect decays further downstream.关键词：Particle image velocimetry;Telecentric optical system;Matched index of refraction;Spacer grid;Lateral flow
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发布时间：2024-10-25 - “钍基氟盐冷却高温堆燃料元件研究取得新进展，分析了TRISO包覆燃料颗粒结构对堆芯性能的影响，为物理设计提供参考。”摘要：BackgroundThorium-based pebble bed fluoride salt-cooled high-temperature reactor (PB-TFHR) is one of the reactor types in the fourth generation reactors. It uses pebble fuel design filled with TRISO (TRi-structural ISOtropic) coated fuel particles dispersed in a graphite matrix and has good neutronic and safety performances.PurposeThis study aims at the radius of kernel, thickness and density of coating layers of TRISO in PB-TFHR for neutron properties, the production of fission gas with krypton, xenon and iodine, and failure rate of coated fuel particles. It can provide a design reference for the reactor physics of FHR.MethodsThe Standardized Computer Analyses for Licensing Evaluation (SCALE) 6.1 program and the corresponding submodules such as burnup and cross section processing were used to calculate the critical and burnup for the PB-TFHR and the PANAMA model was used to calculate the failure rate of TRISO coated fuel particles.ResultsThe results show that when the thickness and density of coating layers are maintained unchanged, a larger radius of kernel (≥0.01 cm) is required to meet the requirement that the reactor is under-moderated while the temperature feedback of core is always negative. When the thickness and density of the coating layers keep constant, at the same burnup, the smaller the radius of kernel is, the less fission gas is produced and the smaller the failure rate is. When the density of coating layers is not changed, variations of the thickness of the porous carbon buffer and the inner pyrolytic carbon layer have a great influence on the keff whilst keeping the thickness of the coating layers unchanged, only changing the density of the coating layers does not affect the keff obviously.ConclusionThe analysis of this study give the optimal structure of TRISO coated fuel particle and provide some reference for the physical design.关键词：PB-TFHR;Pebble;TRISO;Burnup;Failure rate
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发布时间：2024-10-25 - “在高通量堆内辐照ThO2样品，分析裂片核素产额，分离铀/钍并测算U含量。”摘要：BackgroundThorium is a potential source of nuclear energy, and thorium fuel element has many unique advantages over the uranium-based fuel element. A lot of research on its utilization has been carried out in the world. In recent years, China has strengthened the research and application of thorium nuclear fuel, but compared with the uranium plutonium cycle, the basic data is very short and the technical foundation is very weak.PurposeThis study aims to optimize the process of the thorium, and provide basic data for the Th-U database.MethodsFirst of all, ThO2 was irradiated in high flux engineering test reactor (HFETR), and irradiated ThO2 was dissolved by trifluomethanesulfonic acid (TFMS). Then, the fission nuclides such as 233Pa and 95Zr, 103Ru and 137Cs were analyzed to obtain their yields. Finally, the U/Th of the sample was separated by tributyl phosphate (TBP) extraction resin, and the content of U was analyzed and calculated by inductively coupled plasma mass spectrometry (ICP-MS) and γ spectrometer.ResultsUnder the condition of thermal neutron fluence of 1.32×1020 n·cm-2 (fast/thermal ratio about 2.8:1), the 233U and 232U content of 7.1 mg irradiated ThO2 were 8.01 μg (yield was 0.128%) and 1.21×10-4 μg respectively, the ratio of 232U/233U was 1.51×10-5.ConclusionsThe related data of the fission nuclide yield of 233U in the process of Th/U transformation is improved, especially in the lower case of thermal neutron injection. The relationship of correlation between the generation of 232U and the fast neutron is confirmed, and further the key problems of the relationship between nuclear and neutron injection of 233U and 232U is confirmed, too.关键词：Thorium dioxide;ThO2;Thorium uranium cycle;233U;232U
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发布时间：2024-10-25
NUCLEAR ENERGY SCIENCE AND ENGINEERING
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