最新刊期
卷 44 ， 期 9 ， 2021
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Ambient pressure X-ray absorption spectroscopy at ME2-BL02B of SSRF and its application in catalysis AI导读
“在催化、环境和能源领域，上海光源ME2-BL02B实验站发展的近常压X射线吸收谱方法，可有效探测真实反应状态下样品表面的化学信息变化。”摘要：BackgroundThe traditional soft X-ray absorption spectroscopy (XAS) method can only work under ultra-high vacuum conditions and cannot be used to detect changes in the electronic structure of samples under real conditions. However, the in-situ soft X-ray absorption spectroscopy method developed in the past decade is mainly based on the fluorescence yield mode. The lack of surface sensitive electron yield mode XAS, especially the Auger electron yield mode, hinders effective detection of chemical information and electronic structure changes on the surface.PurposeThis study aims to investigate the near-ambient pressure X-ray absorption spectroscopy method and the chemical information of the sample surface in the real state.MethodsBy constructing the communication between electron energy spectrometer and the monochromator, the near-atmospheric soft X-ray absorption spectroscopy setup and method were developed at the ME2-BL02B terminal station of Shanghai Synchrotron Radiation Facility (SSRF) different modes of X-ray absorption spectrum under in-situ conditions could be measured in this terminal station, including total electron yield, partial electron yield, and Auger electron yield mode. With the help of in-situ method, the dynamic surface changes of materials at different depths could be described, and platinum-titanium dioxide catalyst for CO oxidation was selected as an example.ResultsThe in-situ ambient pressure X-ray absorption spectroscopy of the electron yield mode recently developed at the ME2-BL02B terminal of SSRF is successfully applied to investigating the catalyst surface under real conditions, and experimental results show the superiority of the surface-sensitive XAS method.ConclusionsThe ambient pressure X-ray absorption spectroscopy method of this study can be used to approximate the chemical information changes of samples in real environments, thereby providing powerful tools for users in the fields of catalysis, environment and energy.关键词：Ambient pressure;In situ;X-ray absorption spectroscopy;Electron yield mode;Surface catalysis- 426
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发布时间：2024-10-25 -
Screening of safe dietary restriction therapy based on synchronous X-ray fluorescence microscopy AI导读
“最新研究评估了饮食限制疗法对小鼠体重、生存期和肝肾功能的影响，为肿瘤治疗提供新思路。”摘要：BackgroundDietary restriction therapy is one of the new methods of tumor treatment following surgery, radiotherapy and chemotherapy, and it plays an important role in the treatment of various tumors. However, there are no studies on the safety of this therapy.PurposeThis study aims to evaluate the effect of dietary restriction therapy on the body and to screen a safe dietary restriction therapy.MethodFirst of all, twenty mice were used for 45 days of food intake testing after 1 week of adaptive feeding. Secondly, sixty mice were randomly divided into 4 groups, one was taken Ad-libitum fed (AL) and 3 groups were treated by three dietary restrictions, i.e., 50% daily dietary restriction (DR), alternate-day fasting (ADF), alternate-day 50% dietary restriction (ADR). Daily food intake of normal mice was checked and the effects of three dietary restrictions on weight and survival time were evaluated. The liver and kidney function was tested on the collected serums of these mice to screen out the optimal dietary restriction scheme. Then, synchrotron-based hard X-ray fluorescence microscopy was used to test the biodistribution of several trace elements in liver and kidney for the safety evaluation of the optimal dietary restriction scheme. Haematoxylin and eosin (H&E) staining was employed to test whether the organs and tissues had lesions.ResultsExperimental results show that the average daily food intake of the mice is 0.2 g per gram of body weight. The body weight of the mice treated with 50% daily dietary restriction decreases linearly, and the survival time is significantly shortened; alternate-day fasting results in significant weight loss, shortened survival time and abnormal liver and kidney function whilst alternate-day 50% dietary restriction has no significant changes in body weight, survival time, liver and kidney function, and the biodistribution of trace elements in liver and kidney, and the pathology of major organs.ConclusionA safe dietary restriction scheme developed in this study will provide theoretical and experimental basis for the adjuvant treatment of malignant tumors with dietary restriction therapy.关键词：Dietary Restriction;Safety;Synchrotron-based hard X-ray fluorescence microscopy;Elements distribution;Histopathology- 412
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发布时间：2024-10-25 - “上海同步辐射光源研发三维位置诊断系统，实现同步工作点高精度测量，为束流纵向动力学研究提供新方法。”摘要：BackgroundThe precise measurement of the synchrotron tune is of great significance for the study of beam longitudinal dynamics and the improvement of beam stability. In 2020, a bunch-by-bunch 3D position diagnosis system to measure the transverse position and longitudinal phase was built at Shanghai Synchrotron Radiation Facility (SSRF), it can also be used to monitor synchrotron tunes in real time. Compared with the traditional measurement method, the advantage of this method is that it does not need to modulate the RF cavity pressure.PurposeThis study aims to achieve high-precision measurement of synchrotron tune in the normal operating mode without disturbing the user's experiments.MethodsThe phase oscillation of the refilled charge during the injection transient was extracted to effectively remove the interference of the RF system and the crosstalk between bunches. Correlation coefficient was used to obtain the bunch phase refilled with charge. Then, multiple longitudinal parameters, including the synchrotron tune, were fitted by mathematical model.ResultsThe measurement results show that the synchrotron tune of SSRF is 0.007 3, and the fitting accuracy is 95%. The momentum compaction factor of storage ring directly calculated by the formula is 4×10-4.ConclusionsThe bunch-by-bunch 3D position diagnosis system and refilled charge extraction algorithm provide a favorable tool for realizing high-precision measurement of synchrotron tune.关键词：SSRF;Synchrotron tune;Bunch-by-bunch 3D position diagnosis system;Refilled charge;Phase oscillation
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发布时间：2024-10-25
SYNCHROTRON RADIATION TECHNOLOGY AND APPLICATIONS
- “在加速器准直控制网观测数据处理领域，三维平差理论基础更严密，但存在误差累积问题。专家分析了误差来源和传播方式，验证了抑制方法，有效控制误差累积。”摘要：BackgroundCompared with 2D+1D adjustment, three dimensional adjustment has a more rigorous theoretical basis. However, when the unconstrained three dimensional adjustment is applied to the observation values processing of the accelerator alignment control network, serious error accumulation will occur and resulting in obvious distortion of the results.PurposeThis study aims to expound the ways and characteristics of three dimensional adjustment error accumulation for accelerator alignment control network.MethodsFirstly, based on the layout of accelerator alignment control network and the moving station measurement method of laser tracker, the three dimensional adjustment mathematical model was analyzed, and the least-squares collocation theory was used to clearly explain the error propagation. Secondly, the characters of laser tracker measurement accuracy, station positioning and orientation accuracy and single station measurement error propagation were studied by analyzing the laser tracker 3D coordinate measurement model, measurement point error model and simulation measurement experiments. Finally, adjustment calculation of the linac control network was verified by simulation measurement, and two error accumulation suppression methods were tested.ResultsThe source and propagation mode of error accumulation are explained theoretically, and verified by simulation calculation, so are the serious error accumulation of elevation and lateral errors in three dimensional adjustment of control network in accelerator.ConclusionsProviding high-precision point coordinate constraint for three dimensional adjustment can effectively suppress error accumulation, and providing high-precision orientation constraint for station coordinate system can also achieve the effect of suppressing error accumulation.关键词：Three dimensional adjustment;Accelerator alignment control network;Laser tracker;Error accumulation;Move station measurement
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发布时间：2024-10-25 - “在饮用水放射性测定领域，专家通过研究α-β串道现象，提出了修正方法，有效提高了测定准确性。”摘要：BackgroundThere is α-β crosstalk in determination of gross α and β radioactivities in drinking water using a low background scintillation counter, which may lead to erroneous measurement results.PurposeThis study aims to reduce the α-β crosstalk in the determination of gross α and β radioactivities on a low background scintillation counter.MethodsFirst of all, α-β crosstalk correction factors for α (241Am) and β (90Sr-90Y) planar sources were determined on a typical scintillator with low background α/β measuring instrument--BH1227, to ascertain the particles or rays causing the α-β crosstalk. Then, α-β crosstalk correction factors for α and β standard sources with different areas and thicknesses were measured by the BH1227 to explore the relationship between the crosstalk correction factors and the areas and thicknesses of α and β standard sources. The gross α and β radioactivities of drinking water samples with different α or β radioactivity levels were measured and corrected by the BH1227, and the crosstalk correction factors obtained from the α and β standard sources, respectively. Finally, comparisons of the gross α and β radioactivities without and with the crosstalk corrections in drinking water samples were performed to verify the crosstalk correction.ResultsIt is shown that, while pulses arising from alpha particles can get into β channel, the opposite is not typically done. With the increasing of thicknesses of the α standard sources, the α-to-β crosstalk correction factors increase first and then tend to be stable, but have no relation with their areas. The β-to-α crosstalk correction factor for the β standard sources is zero. The correction with the α-to-β crosstalk correction factors obtained from α standard sources, which have the same thickness and area as sample sources, minimizes the α-to-β crosstalk in gross β radioactivity measurement for drinking water samples. The determination of gross α radioactivity in the drinking water samples is not affected by the β-to-α crosstalk.ConclusionsThe pulses caused by β particles or X-γ rays, which can get into α channel lead to erroneous counting, can be effectively rejected by a reasonable increase of α threshold. The α-to-β crosstalk can be effectively reduce with properly adjusting the upper and lower thresholds of β channel to make the α-to-β crosstalk factor as small as possible and performing the α-to-β crosstalk correction on the β count.关键词：Low background α and β measuring scintillation counter;Determination of gross α and β radioactivities in drinking water;Crosstalk correction
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发布时间：2024-10-25
ACCELERATOR, RAY TECHNOLOGY AND APPLICATIONS
- “在光学元件抛光领域，专家设计了高能量大束流氩离子枪，实现了大口径碳化硅非球面反射镜的高精度快速抛光。”摘要：BackgroundLarge size aspherical mirrors have been widely used in space communication systems because of their high angular resolution and energy harvesting ability.PurposeThis study aims to develop a high energy and high flux argon (Ar) ion gun for the rapid polishing of modified silicon layer on the surface of large size SiC aspherical mirror.MethodsFirst of all, Ar ionization was realized by filament and anode grid. Ar+ energy was determined by anode voltage whilst the extractor and electrostatic lenses were employed to achieve Ar+ emission and focusing. The high transmittance of argon ions was realized by adjusting the voltage between the filament and the anode grid to maximize the ionization rate, and adjusting the size and relative position of the electrostatic focusing lens. The materials in the Ar ion gun were selected not only suitable for ultra-high vacuum, but also preventing from vacuum discharge. Then, the parameters of the main components of argon ion gun were determined by theoretical calculation and simulation of the trajectory of argon ion beam. Finally, preliminary experimental tests were carried out to verify its performance.ResultsThe test results show that the Ar+ energy and beam flux can reach 20 keV and 50 μA, respectively, at 30 mm working distance and Ar partial pressure of 1.2×10-2 Pa. The beam size can be continuously adjusted from 19 mm to 24 mm.ConclusionsThis developed argon ion gun with small size, high energy and high flux, can be installed on a vacuum multi-dimensional displacement table for a wide range of movement to achieve high vacuum surface polishing of large aperture optical elements.关键词：Argon ion gun;Optical mirror polishing;Surface science;Electrostatic focusing lens
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发布时间：2024-10-25 - “在辐射环境质量测量领域，专家采用4种自吸收修正方法对土壤样品进行分析，蒙特卡罗抽样法最精确。”摘要：BackgroundIn radiation environmental quality measurement or emergency measurement, most samples have different media composition, and the laboratory standard sources are limited.PurposeThis study aims to improve the analysis accuracy of different samples by self-absorption correction of the samples.MethodsFour different self-absorption correction methods, were used to test and analyze soil samples containing different nuclides to calculate the self-absorption correction of volume samples. The geometric dimension of samples was the same as the standard solid point source ø75 mm×70 mm. The point detector correction method, the mean effective length correction method and the vertical incident correction method were employed to simplify the detector, the sample box and the incident angle, respectively, whilst the Monte Carlo correction method was closest to the actual situation of the γ-ray near-incidence detector in the sample.ResultsThe Monte Carlo correction method has the least deviation for low energy nuclides which is within ±8% between the correction results and true values, better than that of mean effective length method. The point detector correction method, the vertical incidence correction method, and the mean effective length correction method have small deviation for middle and high energy nuclides, but the deviations of these three methods for low-energy nuclides are large.ConclusionsThe Monte Carlo self-absorption correction method can be used as an accurate correction for the self-absorption of low-energy nuclides. If the composition of the medium in the sample is unknown, the mean effective length method can be used to calibrate the self-absorption of the measured nuclides in the middle and high energy parts. The vertical incidence method and point detector method are also suitable for self-absorption correction of the middle and high energy parts. The relative deviation between the correction results and true values is within ±8% in the low-energy part, which is better than the mean effective length method.关键词：γ spectrum;Mass attenuation coefficient;Self-absorption correction
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发布时间：2024-10-25 - “在X射线能谱测量领域，专家提出了基于最小二乘法的快速拟合双指数脉冲算法，用于测量时间常数，拟合优度R2均超过0.95，运行速度比传统算法快两个数量级。”摘要：BackgroundIn the X-ray energy spectrum measurement system, the time constant is an important factor affecting trapezoidal pulse shaping. Accurate measurement of the time constant of double exponential pulse signals is beneficial to obtaining a better trapezoidal pulse shaping.PurposeThis study aims to propose a fast fitting double exponential pulse algorithm for measuring the time constant in trapezoidal pulse shaping.MethodsFirst of all, the linear regression method based on the least square method was adopted to convert nonlinear fitting linear fitting. Then, functional expression of double exponential pulse signal was fitted by fast trapezoidal pulse shaping, and the feasibility of time constant measurement in trapezoidal forming by fast fitting double exponential algorithm was verified by MATLAB programming simulation. Finally, the practicability of the algorithm was evaluated by experimental pulse data of 55Fe radiation source received by X-ray silicon draft detector (SDD). Goodness-of-fit R2 of this algorithm was compared with that of cftool toolbox of MATLAB on both the simulation data and experimental data.ResultsThe goodness of fit R2 of proposed algorithm exceeds 0.95 for both the simulated signal with 5% standard deviation noise and the shaped pulse signal of experiments. When the goodness of fit exceeds 0.95, the running speed of this algorithm is 2 orders of magnitude faster than that in cftool toolbox of MATLAB.ConclusionsThe algorithm of this paper possesses high fitting degree, fast calculation time, hence suitable for real-time measurement of time constant of double exponential pulse signal in embedded system.关键词：Micro-zone energy spectrum;Trapezoidal pulse shaping;Double exponential fitting;Least square method
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发布时间：2024-10-25
NUCLEAR ELECTRONICS AND INSTRUMENTATION
- “中国散裂中子源实验缪子源辐射安全研究取得进展，利用蒙特卡罗模拟软件FLUKA计算分析了瞬发辐射和剩余辐射，优化了屏蔽设计，为建设质子和中子辐照实验平台提供条件。”摘要：BackgroundChina Spallation Neutron Source (CSNS) based on the spallation reaction is a large multidisciplinary research facility, which has been constructed and commissioned since August 2018. Experimental Muon Source (EMuS) is one of the important research platforms for the future construction of CSNS. The proton beam energy is 1.6 GeV and the power on the carbon target is 20 kW.PurposeThis study aim to design radiation and shielding system for EMuS that satisfies the requirements of radiation safety.MethodsThe Monte Carlo simulator of FLUKA was used to calculate and analyze the prompt radiation and residual radiation. According to the dose limit, the shielding optimization design was carried out, and abandoned proton beam flux was estimated. Finally, computational results of FLUKA were analyzed, and compared with that of the Moyer mode semi-empirical formula.ResultsThe simulation results show that the exterior residual radiations of shielding for the high radiation area such as target area, collimation area, dump and muon transport line are very low whilst the inside components such as carbon target, magnets, and vacuum pipes of high-energy proton transport line are critically activated and have high residual radiation. The abandoned proton beam after carbon target is of 1012 cm-2∙s-1.ConclusionsThe optimal shielding design meets the requirements of prompt radiation protection for EMuS of CSNS, but the strategy of remote operations and strict control of maintenance time need to consider for the future maintenance and upgrade. Abandoned proton beam can be efficiently utilized to build a proton irradiation platform and a neutron irradiation platform with carefully studying of the background of those irradiation points.关键词：High-energy proton beam;Prompt radiation;Residual radiation;Shielding;Moyer model;Irradiation platform
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发布时间：2024-10-25 - “在低温去污领域，研究人员开发出一种新型低温去污剂，能在-15~10℃环境下高效去除放射性污染，具有广泛应用潜力。”摘要：BackgroundThe research of low temperature detergent is of great significance for the operating and decommissioning of nuclear facilities at low temperature environment.PurposeThis study aims to explore the fluid characteristics and decontamination characteristics of polyvinyl butyral detergent at low temperature.MethodsThe low temperature detergent was prepared by using polyvinyl butyral as solute, ethanol and ethyl acetate as solvent and citric acid as decontamination additives. The viscosity, fluidity, sprayability and wettability of the detergent on the surface of different materials were measured in experiment. Four simulated U(VI) contaminated plate samples were prepared by the dyeing of the uranyl nitrate solution on the base of glass, stainless steel, ceramic tile and alkyd paint, respectively. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) were used to characterize the decontamination films on the surface of these four samples, and study the decontamination mechanism. Finally, the decontamination characteristics of the detergent for the simulated U(VI) pollution on surface of different materials were studied at low temperature, and the effects of temperature, detergent dosage and surface roughness on decontamination rate were discussed.ResultsExperimental results show that the decontamination rates of the detergent for the simulated U(VI) pollution on the surface of glass, stainless steel, ceramic tile and alkyd paint board are above 97.3%, 93.6%, 95.5% and 88.9%, respectively, in the temperature range of -15~10 ℃, that the temperature and the detergent dosage have little effect on the decontamination rate and that the decontamination film formed by the detergent have good strippability.ConclusionsThe detergent has a good application potential at the decontamination of radioactive pollution in low temperature environment.关键词：Polyvinyl butyral;Low temperature;Decontamination;Peelable film
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发布时间：2024-10-25 - “在航空γ能谱测量领域，专家提出了基于离散积分的三维地形校正方法，提高了测量结果的准确性。”摘要：BackgroundAirborne gamma spectrometer is a method to measure ground gamma nuclide activity (specific activity) by installing gamma spectrometer on aircraft. The accuracy of results is affected by flight altitude and terrain fluctuation. At present, altitude correction has been applied to the quantitative analysis of airborne gamma spectrometer, but the correction effect of altitude correction on areas with large terrain fluctuation is not desirable.PurposeThis study aims to propose a 3D terrain correction method based on discrete integral.MethodsFirst of all, the basic characteristics of digital elevation model (DEM) and radiation field distribution were analyzed. Then, the effective detection area of airborne gamma spectrometer was divided into micro grid surface elements, and the contribution of micro elements to the counting rate of full energy peak of the airborne gamma spectrum was calculated. The terrain correction coefficient by discrete integral was realized by the terrain correction of airborne gamma spectrum measurement results, and the accuracy of airborne gamma spectrum measurement results was simultaneously improved. Finally, verification of this method was performed on the measured airborne gamma-ray spectrum data processing.ResultsVerification results show that the influence of terrain on gamma spectrum data is corrected effectively by the proposed method.ConclusionsThe 3D terrain correction method based on discrete integral can improve the consistency between airborne gamma spectrum measurement results and ground measurement results, and has the advantages of fast mesh division, altitude and terrain correction simultaneous.关键词：Airborne gamma-ray spectrometry survey;Terrain correction;Height correction;Inversion
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发布时间：2024-10-25
NUCLEAR PHYSICS, INTERDISCIPLINARY RESEARCH
- “在核反应堆领域，专家开发了模拟CRUD内部硼沉积的分析模型，揭示了电厂CIPS事件的深刻原因，为评估CIPS风险提供理论依据和数据支撑。”摘要：BackgroundDuring pressurized water reactor (PWR) power operation period, corrosion products tend to deposit in the fuel boiling zone and form chalk rivers unidentified deposit (CRUD). At a certain level of CRUD, boron acid will precipitate and depress local nuclear power, causing CRUD induced power shift (CIPS) incident, however, the operation data of reactors that have undergone CIPS indicate that CRUD thickness is not the only factor affecting CIPS.PurposeThis study aims to evaluate the CIPS risk of PWR more scientifically by establishing an evaluation methodology that comprehensively considers CRUD characteristics and thermal-hydraulic condition.MethodsBased on the internal mass transfer mechanism of the porous media, a model which could simulate boron deposition process inside CRUD was established by combining the consideration of CRUD morphology. According to the simulated results, the deep causes of CIPS in Callaway and Ulchin power plants were revealed.ResultsEvaluation results show that the most important factor of CIPS in Callaway power plant is CRUD thickness which is different from the contribution of CRUD porosity to Ulchin's CIPS.ConclusionsThe CIPS risk evaluation method of this study provides theoretical evidence and supporting data for more scientific CIPS analysis.关键词：PWR;CIPS;CRUD characteristics;Thermal-hydraulic;Boron deposition
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发布时间：2024-10-25 - “在小型移动核电源领域，专家开发了一种堆芯功率展平算法，有效处理复杂堆芯优化问题，降低计算成本。”摘要：BackgroundThe small transportable nuclear power system designed with the solid block heat pipe stack as the core has the advantages of good environmental adaptability, system safety and reliability, deployment flexibility, and resistance to external events. In order to control the sharp rise in reactivity under the water flooding accidents, a spectral shift absorber Gd2O3 is added to its core fuel. During the process of power flatten by adjusting fuel enrichment and Gd2O3 mass fraction at different locations in the core, it is necessary to ensure that the core solution meets a series of objectives such as refueling cycle and critical safety in both the conditions of normal operation and the accident. It makes the power flattening problem of small transportable nuclear reactor with high dimensional decision variables, multiple objectives and constraints, and multiple operating conditions.PurposeThis study aims to develop a core power flattening algorithm for small transportable nuclear power supply to reduce the computational cost.MethodsBased on a co-evolutionary algorithm framework and the laws of physics, a power flattening algorithm was developed to reduce the dimensionality through clustering algorithms. Convergence acceleration was achieved through the collaboration between sub-populations. The agent model based on Gaussian process regression (GPR) was used to predict and screen a large number of core schemes, so as to effectively reduce computational costs.ResultsComputation results show that the power peak factor of the initial scheme is decreased from original 1.30 to 1.14 after the core optimization.ConclusionsCompared with the traditional differential evolutionary algorithms and differential evolution algorithms embedded with clustering, the co-evolutionary based power flattening algorithm has significant advantages in terms of optimization quality and efficiency. The use of the clustering method and the surrogate model in the framework of co-evolutionary algorithms can effectively deal with the optimization of the complex reactor core.关键词：Small transportable nuclear power;Power flatten;Co-evolutionary algorithm;Gaussian process regression
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发布时间：2024-10-25
NUCLEAR ENERGY SCIENCE AND ENGINEERING
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