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Analytic RF design of a linear accelerator with a SLED-Ⅰ type RF pulse compressor

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Nuclear Science and Techniques 2020年第11期31卷 12-22页

作者： Jia-Yang Liu Jia-Ru Shi Hao Zha Alexej Grudiev Ping Wang ying-chao du Huai-Bi Chen Department of Engineering Physics Tsinghua UniversityBeijing 100084China Key Laboratory of Particle and Radiation Imaging(Tsinghua University) Ministry of EducationBeijing 100084China European Organization for Nuclear Research(CERN) 1211 GenevaSwitzerland

This study presents the RF design of a linear accelerator(linac)operated in single-bunch *** accelerator is powered by a compressed RF pulse produced from a SLED-I type RF pulse *** compressed RF pulse has an unflattened shape with a gradient distribution which varies over the structure *** analytical study to optimize the accelerating structure together with the RF pulse compressor is *** optimization aims to maximize the efficiency by minimizing the required RF power from the generator for a given average accelerating *** study shows that,owing to the compressed RF pulse shape,the constant-impedance structure has a similar efficiency to the optimal structure using varying iris *** constant-impedance structure is easily fabricated and is favorable for the design of a linac with a pulse *** utilize these findings to optimize the RF design of a X-band linac using the constant-impedance accelerating structure for the Tsinghua Thomson X-ray source facility.

关键词： X-band linac High gradient structure RF pulse compressor Thomson X-ray source Single-bunch mode

Exploration of Combining Strategy on Teaching Chinese as a Second Language Among American High School Students

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Sino-US English Teaching 2014年第7期11卷 531-534页

作者： ZHAO ying du chao Yanshan University Qinhuangdao China

Among different teaching methods in second language teaching, there are five different core relations： the relations between language and speech, between oral and written language, between foreign and native language, between integrity and individuality, between the use of foreign language and the development of intelligence. With a view on the entire structure of Chinese teaching and learning as a second language among American high school students and through scientifically conducting the five relations and subdividing the teaching purpose, contents, and objects, this paper will elaborate the strategy on selecting and combining different teaching methods in the whole Chinese teaching and learning process. The purpose of this paper is to greatly develop the effectiveness in teaching and learning Chinese as a second language through selecting appropriate strategies and integrating various advantages according to the teaching purpose, content, and the object.

关键词： American high school students teaching methods combing strategy

Simultaneous fluorescence and Compton scattering computed tomography based on linear polarization X-ray

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Nuclear Science and Techniques 2024年第10期35卷 41-50页

作者： Zhi-Jun Chi Hong-Ze Zhang Jin Lin Xuan-Qi Zhang Hao Ding Qi-Li Tian Zhi Zhang ying-chao du Wen-Hui Huang Chuan-Xiang Tang Key Laboratory of Beam Technology of the Ministry of Education School of Physics and AstronomyBeijing Normal UniversityBeijing 100875China Key Laboratory of Particle and Radiation Imaging of the Ministry of Education Department of Engineering PhysicsTsinghua UniversityBeijing 100084China

Purpose To propose a method for simultaneous fluorescence and Compton scattering computed tomography by using linearly polarized *** Monte Carlo simulations were adopted to demonstrate the feasibility of the proposed *** the simulations,the phantom is a polytetrafluoroethylene cylinder inside which are cylindrical columns containing aluminum,water,and gold(Au)-loaded water solutions with Au concentrations ranging between 0.5 and 4.0 wt%,and a parallel-hole collimator imaging geometry was *** light source was modeled based on a Thomson scattering X-ray *** phantom images for both imaging modalities were reconstructed using a maximumlikelihood expectation maximization *** Both the X-ray fluorescence computed tomography(XFCT)and Compton scattering computed tomography(CSCT)images of the phantom were accurately reconstructed.A similar attenuation contrast problem for the different cylindrical columns in the phantom can be resolved in the XFCT and CSCT *** interplay between XFCT and CSCT was analyzed,and the contrast-to-noise ratio(CNR)of the reconstruction was improved by correcting for the mutual influence between the two imaging *** with K-edge subtraction imaging,XFCT exhibits a CNR advantage for the *** Simultaneous XFCT and CSCT can be realized by using linearly polarized *** synergy between the two imaging modalities would have an important application in cancer radiation therapy.

关键词： X-ray fluorescence computed tomography Compton scattering computed tomography Linear polarization Thomson scattering X-ray source Monte Carlo simulation

Beam and image experiment of beam deflection electron gun for distributed X-ray sources

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Nuclear Science and Techniques 2019年第3期30卷 127-138页

作者： Cheng-Jun Tan Chuan-Xiang Tang Wen-Hui Huang Qing-Xiu Jin ying-chao du Qun Luo Pei-Dong Wu Dong-Hai Liu Lu-Ming Zhang Cong Xu Accelerator Laboratory Department of Engineering PhysicsTsinghua University Key Laboratory of Particle and Radiation Imaging Ministry of Education Tsinghua University Nuctech Company Limited

Distributed X-ray sources comprise a single vacuum chamber containing multiple X-ray sources that are triggered and emit X-rays at a specific time and location. This process facilitates an application for innovative system concepts in X-ray and computer tomography. This paper proposes a novel electron beam focusing, shaping,and deflection electron gun for distributed X-ray *** electron gun uses a dispenser cathode as an electron emitter, a mesh grid to control emission current, and two electrostatic lenses for beam shaping, focusing, and deflection. Novel focusing and deflecting electrodes were designed to increase the number of focal spots in the distributed source. Two identical half-rectangle opening electrodes are controlled by adjusting the potential of the two electrodes to control the electron beam trajectory, and then, multifocal spots are obtained on the anode target. The electron gun can increase the spatial density of the distributed X-ray sources, thereby improving the image quality. The beam experimental results show that the focal spot sizes of the deflected(deflected amplitude 10.5 mm)and non-deflected electron beams at full width at half maximum are 0.80 mm 90.50 mm and 0.55 mm 90.40 mm, respectively(anode voltage 160 kV; beam current 30 mA). The imaging experimental results demonstrate the excellent spatial resolution and time resolution of an imaging system built with the sources, which has an excellent imaging effect on a field-programmable gate array chip and a rotating metal disk.

关键词： Beam deflection electron gun X-ray imaging Distributed X-ray sources Stationary CT

Beam dynamics optimization of very-high-frequency gun photoinjector

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Nuclear Science and Techniques 2022年第9期33卷 80-92页

作者： Han Chen Lian-Min Zheng Bin Gao Zi-Zheng Li ying-chao du Ren-Kai Li Wen-Hui Huang Chuan-Xiang Tang duan Gu Zheng Qi Meng Zhang Hai-Xiao Deng Qiang Gu Dong Wang Department of Engineering Physics Tsinghua UniversityBeijing 100084China Chinese Academy of Sciences Shanghai Institute of Applied PhysicsShanghai 201800China Chinese Academy of Sciences Shanghai Advanced Research InstituteShanghai 201210China

Very-high-frequency(VHF)gun photoinjectors,capable of producing high-brightness and high-repetitionrate electron bunches,are some of the best electron sources for driving MHz-class repetition-rate free-electron *** this study,the beam dynamics optimization of a VHF gun photoinjector for Shanghai HIgh Repetition Rate X-ray Free Electron Laser and Extreme Light Facility(SHINE)is systematically demonstrated using a genetic *** the inclusion of the solenoid geometry as an optimization variable into the genetic algorithm,the optimum projected normalized emittance for 100 pC bunches with bunch length of 1 mm rms is reduced to 0.1 mm mrad for 100%of the particles and 0.075 mm mrad for 95%of the particles,proving that sub-100 nm emittance can be achieved in the SHINE injector using a single-cell Tsinghua University(THU)VHF *** emittance fulfills the requirements not only of SHINE and Linac Coherent Light Source(LCLS)-II but also of LCLS-II-High Energy(LCLS-II-HE).We demonstrate that the optimal emittance in the VHF gun injector is reduced via the optimization of the solenoid geometry,thereby reducing solenoid spherical *** the inclusion of high-order(H.O.)energy spread among the optimization objectives,the *** spread can be reduced by a factor of nearly six using a high-harmonic cavity despite a 38%emittance ***,the beam dynamics in the SHINE main accelerator show that reducing the *** spread in the injector is of great significance to improving compression efficiency and reducing bunch current spike.

关键词： VHF gun photoinjector Multi-objective optimization Emittance High-order energy spread

Observation and mitigation of image distortion in high-energy electron radiography

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Nuclear Science and Techniques 2023年第6期34卷 69-77页

作者： Hao-Qing Li Liang Sheng Chang-Qing Zhang ying-chao du Zheng Zhou Xiu-Feng Weng Jia-Hao Xiao Hong-Qiao Yin Bin Sun Kun Wei Yang Li Bao-Jun duan Yong-Tang Liu Yan-Hong Zhang Mei Zhang Yan Song Xiao-Dong Zhang Jun Liu Zhu-Ming Fu Qing Xu Xue du Jian-Peng Gao Xin-Yi Wang Xin-Jian Tan Dong-Wei Hei Department of Engineering Physics Tsinghua UniversityBeijing100084China State Key Laboratory of Intense Pulsed Radiation Simulation and Effect Northwest Institute of Nuclear TechnologyXi’an710024China Institute of Applied Electronics China Academy of Engineering PhysicsMianyang621900China Institute of Intelligent Machines Hefei Institutes of Physical ScienceChinese Academy of SciencesHefei230031China Zhongke Hefei Institutes of Collaborative Research and Innovation for Intelligent Agriculture Hefei231131China

Image distortion caused by the angular misalignment of quadrupole magnets in high-energy electron radiography has been studied *** propose that the distortion originates from the coupling of the electron motions in the transverse directions,based on a theoretical analysis and the transfer-matrix *** relative angular rotation between the second and third magnetic quadrupoles was identified as the main contributor to image *** was verified by both a beam-dynamics simulation and *** strategies to mitigate this image distortion are also explored,including magnets online tuning,higher beam energy and larger magnification *** study provides criteria for designing experiments and paves the way for achieving higher image precision.

关键词： Misalignment Angular rotation Russian quadruplet Transfer matrix

Simulations of electron zebra stripes in the inner radiation belt using a composite empirical electric field model

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Science China Earth Sciences 2025年第1期68卷 27-38页

作者： Ziyang WANG ying LIU Qiugang ZONG Hong ZOU Yuguang YE Xuzhi ZHOU chao YUE Shan WANG Institute of Space Physics and Applied Technology Peking University State Key Laboratory of Lunar and Planetary Science Macau University of Science and Technology

The phenomenon termed “zebra stripes” manifests as regular patterns in the energy-space(L shell) spectrum of energetic electrons(ranging from tens to hundreds ke V) within the inner radiation belt. These structures exhibit drift-periodic behavior and commonly arise from large-scale electric field perturbations near the substorm onsets. In this study, we introduce a composite electric field model and replicate the formation, structure, and evolution of zebra stripes using a bounce-averaged test particle code under this electric field model. High-resolution measurements of energetic electrons obtained from the Van Allen Probes and the recently launched Macao Science Satellites-1 are used as initial conditions and served to validate our test particle simulations. Comparative analyses between observed data and simulations demonstrate our test particle method's efficacy in capturing zebra stripes' general behavior. Moreover, the composite model proves capable of reproducing realistic variations in the electric field within the inner radiation belt to a certain extent. Nevertheless, subtle differences emerge in the flux strength and the positions of stripes. These disparities primarily stem from limitations inherent in the electric field model and the initial conditions of the simulation. Acknowledging that the model represents an average case, it is conceivable that real-world scenarios may deviate from the average, thereby introducing variations in the observed phenomena.

关键词： Zebra stripes Inner radiation belt Large-scale electric fields Van Allen Probes Macao Science Satellite

Observation of topological charge transformations in acoustic vortex using passive periodic systems

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Science China(Physics,Mechanics & Astronomy) 2025年第1期Mechanics & Astronomy) .卷 140-147页

作者： Di-chao Chen Xie Liu Changqing Xu Da-Jian Wu ying Cheng Xiao-Jun Liu School of Physics and Technology Nanjing Normal University Key Laboratory of Modern Acoustics School of Physics Nanjing University

Vortex transmutation utilizes a periodic system, which not only enables the alteration of the topological charge(TC) of unstable input vortices but also facilitates their transformation into stable structures. This approach is crucial for investigating the characteristics of vortices in various wave systems. Here, we achieve acoustic vortex TC transmutation by employing a welldesigned dual-structured plate external system(DPES). The interactions between the acoustic vortex and the finite-order discrete rotational symmetry lead to the transformation of its topological charge when complete rotational symmetry is broken to Nthorder discrete symmetry. Our results experimentally demonstrate the acoustic vortex TC transmutation based on passive artificial structures, enabling numerous applications in particle manipulation and information multiplexing as well as advancing our understanding and control over free-space acoustic vortices.

关键词： acoustic vortex topological charge transformation artificial structure

Oxygen vacancies enriched Ir/WOx catalysts for the directly chem-catalytic conversion of cellulose to ethanol

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Tungsten 2025年第1期7卷 88-99页

作者： Yu-Jing Weng Zhao-ying Ding ying-chao Li Yuan-Feng Wu Yuan-Yang Xu Rui Chen Xiao-Lei Zhao Hai-Yong Wang Da-Lei Zhang Yu-Long Zhang Henan Key Laboratory of Coal Green Conversion and International Joint Laboratory of Coal Clean Utilization College of Chemistry and Chemical Engineering Henan Polytechnic University Key Laboratory of Renewable Energy Guangzhou Institute of Energy Conversion Chinese Academy of Sciences Liaoning Institute of Energy Technology

Tungsten and its oxides are highly versatile catalysts with unique properties that hold great promise for a wide array of applications,including biological pathways and chemical *** chemo-catalysis of cellulose to ethanol presents a promising avenue for ethanol synthesis with the potential for enhanced efficiency compared to conventional methods,offering a sustainable and carbon-neutral alternative to existing petrochemical and biological ***,Ir/WOxcatalysts enriched with oxygen vacancies were meticulously prepared and demonstrated remarkable catalytic performance in converting cellulose to ethanol directly in the presence of tungstic *** catalyst achieved a high ethanol yield of 66.5%under optimal reaction conditions,approaching the theoretical yield limit of traditional ethanol *** results revealed the presence of oxygen defects,Bronsted/Lewis acidity,and Ir nanoclusters on the catalyst surface,working synergistically to facilitate the cascade catalysis of cellulose hydrolysis,sugar retro-aldol condensation reaction,and C2 intermediate hydrodeoxygenation to *** situ Fourier transform infrared spectrometer analysis confirmed the catalyst's ability to enhance the adsorption and activation of ethylene glycol for ethanol *** manipulating subtle structural features,this study offers a fresh perspective on tungsten group catalyst design and underscores the importance of synergistic effects among catalytic sites for the efficient production of ethanol from cellulose.

关键词： Cellulosic ethanol Chem-catalysis Hydrogenolysis Retro-aldol condensation Tungsten