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Design of an electron gun for terahertz radiation source

Chinese Physics C 2014年第4期38卷 93-97页

作者：李骥裴元吉胡桐宁陈曲珊冯光耀尚雷李成龙 National Synchrotron Radiation Laboratory University of Science and Technology of China State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology Deutsches Elektronen-Synchrotron

An EC-ITC （External-Cathode Independently Tunable Cells） RF gun was employed with the aim of obtaining short-pulse bunches with high peak current for a terahertz radiation source. A gridded DC gun plays a key role as the external injecting electron source of the ITC RF gun, the performance of which determines the beam quality in the injector and transport line. In order to make the beam well compressed in the ITC RF gun, the energy of the electrons acquired from the gridded DC gun should be 15 keV at most. A proper structure of the gridded gun with double-anode is shown to overcome the strong space- charge force on the cathode, which is able to generate 6 μs beam with 4.5 A current successfully.

关键词： gridded DC gun RF gun EC-ITC

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Research on hybrid multi-terminal high-voltage DC technology for offshore wind farm integration

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Journal of Modern Power Systems and Clean Energy 2013年第1期1卷 34-41页

作者： Peng ZHAN Chenghao LI Jinyu WEN Yu HUA Meiqi YAO Naihu LI State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and TechnologyWuhan 430074Chin Grid Technology Center(China)Co.Ltd. Shanghai 201114China

Multi-terminal high-voltage DC(MTDC)technology is a promising way to transmit large amounts of offshore wind power to the main *** paper proposes a hybrid MTDC scheme to integrate several offshore wind farms into the onshore power grids at different locations.A hybrid four-terminal HVDC system comprising two onshore line commutated converters(LCCs)and two voltage source converters(VSCs)connecting an offshore wind farm is constructed in PSCAD/EMTDC.A coordination control scheme based on the VSCs’AC voltage control and the LCCs’DC voltage droop control is designed to ensure smooth system operation and proper power sharing between onshore AC *** operational characteristics of the system are *** addition,a black start-up method without any auxiliary power supply for the VSCs is *** transmission scheme is tested through simulations under various conditions,including start-up,wind speed variation,and the disconnection of one VSC or of one LCC.

关键词： Hybrid multi-terminal HVDC Offshore wind farm Droop control Voltage source converter Line commutated converter

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Staged reaction kinetics and characteristics of iron oxide direct reduction by carbon

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International Journal of Minerals,Metallurgy and Materials 2015年第10期22卷 1025-1032页

作者： Ru-fei Wei Da-qiang Cang Ling-ling Zhang Yuan-yuan Bai School of Metallurgical and Ecological Engineering University of Science and Technology Beijing State Key Laboratory of Advanced Metallurgy University of Science and Technology Beijing School of Civil and Environmental Engineering University of Science and Technology Beijing Key Laboratory of Electromagnetic Processing of Materials of the Ministry of Education Northeastern University

Staged reduction kinetics and characteristics of iron oxide direct reduction by carbon were studied in this work. The characteristics were investigated by simultaneous thermogravimetric analysis, X-ray diffraction（XRD）, and quadrupole mass spectrometry. The kinetics parameters of the reduction stages were obtained by isoconversional（model-free） methods. Three stages in the reduction are Fe2O3→Fe3O4, Fe3O4→Fe O, and Fe O→Fe, which start at 912 K, 1255 K, and 1397 K, respectively. The CO content in the evolved gas is lower than the CO2content in the Fe2O3→Fe3O4stage but is substantially greater than the CO2 contents in the Fe3O4→Fe O and Fe O→Fe stages, where gasification starts at approximately 1205 K. The activation energy（E） of the three stages are 126–309 k J/mol, 628 k J/mol, and 648 k J/mol, respectively. The restrictive step of the total reduction is Fe O→Fe. If the rate of the total reduction is to be improved, the rate of the Fe O→Fe reduction should be improved first. The activation energy of the first stage is much lower than those of the latter two stages because of carbon gasification. Carbon gasification and FexOy reduction by CO, which are the restrictive step in the last two stages, require further study.

关键词： iron oxides direct reduction reduction kinetics re

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Switching Reaction Pathway of Medium-Concentration Ether Electrolytes to Achieve 4.5 V Lithium Metal Batteries (vol 23, pg 8481, 2023)

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NANO LETTERS 2023年第21期23卷 10097-10097页

作者： Jiang, Zhipeng Deng, Yu Mo, Jisheng Zhang, Qingan Zeng, Ziqi Li, Yongtao Xie, Jia School of Materials Science and Engineering Key Laboratory of Green Fabrication and Surface Technology of Advanced Metal Materials of Ministry of Education Anhui University of Technology Maanshan 243002 China State Key Laboratory of Advanced Electromagnetic Engineering and Technology School of Electrical and Electronic Engineering Huazhong University of Science and Technology Wuhan 430074 China

Pursuing high-energy-density lithium metal batteries (LMBs) necessitates the advancement of electrolytes. Despite demonstrating high compatibility with lithium metal anodes (LMAs), ether-based electrolytes face challenges in achieving stable cycling at high voltages. Herein, we propose a strategy to enhance the high-voltage stability of medium-concentration (∼1 M) ether electrolytes by altering the reaction pathway of ether solvents. By employing a 1 M lithium difluoro(oxalato)borate in dimethoxyethane (LiDFOB/DME) electrolyte, we observed that LiDFOB displays a pronounced tendency for decomposition over DME, leading to a modification in the decomposition pathway of DME. This modification facilitates the formation of a stable organic–inorganic hybrid interface. Utilizing such an electrolyte, the Li-LCO cell demonstrates a discharge specific capacity of 146 mAh g–1 (5 C) and maintains retention of 86% over 1000 cycles at 2 C under a 4.5 V cutoff voltage. Additionally, the optimized ether electrolyte demonstrated outstanding cycling performance in Li-LCO full cells under practical conditions.

关键词： lithium metal battery electrolyte high-voltage ether interface

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The design and fault ride through control of un-interrupted DC-DC Autotransformer

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Science China(Technological Sciences) 2018年第12期61卷 1935-1949页

作者： LI MengBo XIANG Wang ZUO WenPing YAO LiangZhong LIN WeiXing WEN JinYu State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology Renewable Energy Department China Electric Power Research Institute TBEA China Xinjiang Sunoasis Co. Ltd

This paper proposed a novel type of DC-DC converter, termed as un-interrupted DC Autotransformer(un-interrupted DC AUTO), which has the capability to ride through DC fault on either side of the converter without blocking any devices. Besides that, the adequately designed converter retains the advantages of DC AUTO technology, namely reduced investment cost and transmission loss. To begin with, the topology and basic attributes of the un-interrupted DC AUTO are illustrated. Then the design goals and the corresponding design procedures are analyzed. Furthermore, an effective control system is proposed to enable the converter steady operation during both normal and faulted conditions. Finally, a 1000 MW ±320 kV/±640 kV test system is built on PSCAD/EMTDC platform to verify the technical feasibility of the proposed converter and the effectiveness of the control strategy.

关键词： DC-DC power conversion DC Autotransformer HVDC converters DC fault control strategy

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Multiband adjustment engineering strategy for broadband range in photonic crystals

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Results in Physics 2025年 68卷

作者： Yu, Wenjia Liu, Shiyu Sun, Hang Wang, Jicheng Yang, Yuting Shen, Xiaopeng School of Science Jiangsu Provincial Research Center of Light Industrial Optoelectronic Engineering and Technology Jiangnan University Wuxi 214122 China School of Materials Science and Physics China University of Mining and Technology Xuzhou 221116 China Key Lab of Advanced Optical Manufacturing Technologies of Jiangsu Province Soochow University Suzhou 215006 China State Key Laboratory of Millimeter Waves Southeast University Nanjing 210096 China

Topological edge states are crucial for optical modulation, and the overlapping Brillouin zones in nested structures can effectively control multiband edge states. A nested photonic crystal framework can enhance the rotational freedom, providing additional functionalities. In this study, a multifunctional, tunable, innovative double-rotation C₄ nested photonic crystal structure was developed;it reached a higher degree of freedom via double independent rotations. These nested C₄ photonic crystal structures could expand the functional range of C₄ structure implementation. The multifunctional implementation of multienergy band transmissions, unidirectional transmissions, and wavelength division multiplexers containing nested C₄ structures were experimentally demonstrated. The experimental results agreed well with the simulated predictions. Thus, this study offers new insights and strategies to foster the advancement of topological photonics and radar communication devices. © 2024 The Author(s)

关键词： Multiband adjustment Multienergy band transmissions Photonic crystals Wavelength division multiplexing

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Error field penetration in J-TEXT tokamak based on two-fluid drift-MHD model

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Chinese Physics B 2024年第4期33卷 545-551页

作者：王文徐涛张仪 the J-TEXT team State Key Laboratory of Advanced Electromagnetic Technology International Joint Research Laboratory of Magnetic Confinement Fusion and Plasma PhysicsSchool of Electrical and Electronic EngineeringHuazhong University of Science and TechnologyWuhan 430074China

An externally generated resonant magnetic perturbation can induce complex non-ideal MHD responses in their resonant *** have studied the plasma responses using Fitzpatrick's improved two-fluid model and program *** calculated the error field penetration threshold for *** addition,we find that the island width increases slightly as the error field amplitude increases when the error field amplitude is below the critical penetration ***,the island width suddenly jumps to a large value because the shielding effect of the plasma against the error field disappears after the *** scanning the natural mode frequency,we find that the shielding effect of the plasma decreases as the natural mode frequency ***,we obtain the m/n=2/1 penetration threshold scaling on density and temperature.

关键词： plasma responses drift-MHD model error field penetration

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Effect of dilution gas composition on the evolution of graphite electrode characteristics in the spark gap switch

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Plasma Science and technology 2021年第6期23卷 74-82页

作者： Hongyu DAI Lee LI Shuai REN Jingrun GUO Xin GONG Anthony Bruce MURPHY State Key Laboratory of Advanced Electromagnetic Engineering and Technology Key Laboratory of Pulsed Power Technology(Ministry of Education)School of Electrical and Electronic EngineeringHuazhong University of Science&TechnologyWuhan 430074People's Republic of China CSIRO Manufacturing Lindfield NSW 2070Australia

As the widely implemented electrode material,graphite has the characteristic of sublimation by the thermal shock of the switching arc,and the produced carbon vapor is easy to condense into carbon powders and deposit in the *** impact of the type of dilution gas in a mixture of20%oxygen and 80%dilution gas on the sublimation and oxidation characteristics of the graphite electrode is *** is found that when nitrogen dilution gas was replaced by argon,the heat flux to the electrodes decreased,which led to a 63%reduction of graphite *** the same time,the cooling rate of the arc was slower in argon,which promotes oxidation of the carbon *** residual solid carbon can be reduced by 70%–85%by using argon as the dilution ***,it is demonstrated that the stability and working life of the switch could be increased by appropriate selection of the dilution gas.

关键词： pulsed discharge graphite electrode thermal arc dilution gas electrode erosion

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Power supply for generating frequency-variable resonant magnetic perturbations on the J-TEXT tokamak

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Plasma Science and technology 2018年第8期20卷 96-103页

作者： Guo XU Bo RAO Yonghua DING Mao LI Da LI Ruo JIA Minxiong YAN Xinke JI Nengchao WANG Zhuo HUANG Daojing GUO Lai PENG State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and TechnologyWuhan 430074People＇s Republic of China School of Electrical and Electronic Engineering Huazhong University of Science and TechnologyWuhan 430074People＇s Republic of China

To further research the response of the tearing mode（TM） to dynamic resonant magnetic perturbation（DRMP） on the J-TEXT tokamak, a modified series resonant inverter power supply（MSRIPS） with a function of discrete variable frequency is designed for DRMP coils in this study. The MSRIPS is an AC–DC–AC converter, including a phase-controlled rectifier, an LC filter, an insulated gate bipolar transistor（IGBT） full bridge, a matching transformer, three resonant capacitors with different capacitance values, and three corresponding silicon controlled rectifier（SCR） switches. The function of discrete variable frequency is realized by switching over different resonant capacitors with corresponding SCR switches while matching the corresponding driving frequency of the IGBT full bridge. A detailed switching strategy of the SCR switch is put forward to obtain sinusoidal current waveform and realize current waveform smooth transition during frequency conversion. In addition, a resistor and thyristor bleeder is designed to protect the SCR switch from overvoltage. Manufacturing of the MSRIPS is completed, and the MSRIPS equipment can output current with an amplitude of 1.5 kA when its working frequency jumps among different frequencies. Moreover, the current waveform is sinusoidal and can smoothly transition during frequency conversion. Furthermore, the transition time when the current amplitude rises from zero to a steady state is less than 2 ms during frequency conversion. By using the MSRIPS, the expected discrete variable frequency DRMP is generated, and the phenomenon of the TM being locked to the discrete variable frequency DRMP is observed on the J-TEXT tokamak.

关键词： tearing mode J-TEXT series resonant inverter discrete variable frequency silicon controlled rectifier

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Design and control of the accelerator grid power supply-conversion system applied to CFETR N-NBI prototype

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Plasma Science and technology 2020年第8期22卷 175-183页

作者： Dongyu WANG Ming ZHANG Shaoxiang MA Shu YANG Kexun YU Yuan PAN State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and TechnologyWuhan 430074People's Republic of China School of Electrical and Electronic Engineering Huazhong University of Science and TechnologyWuhan 430074People's Republic of China

The acceleration grid power supply(AGPS)rated 200 kV/25 A is a key component devoted to supply the acceleration grids of the China fusion engineering test reactor negative-ion-based neutral beam injector(N-NBI)prototype *** paper focused on the design and control of the AGPS conversion system(AGPS-CS),with emphasis on the requirement of the wide range output voltage and rise time.A voltage regulation switch at the front of step-down transformer is applied to optimize the grid current and DC-link ***,a new feedforward control strategy with piecewise PI compensator is proposed to improve the characteristics of *** simulation results of the proposed AGPS-CS are presented,proving the performance of the power supply to achieve the desired requirements.

关键词： CFETR NBI accelerator grid power supply feedforward control high voltage power supply

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