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Design, Test and Shimming of a 1.5 T Head-Only MRI Superconducting Magnet

IEEE Transactions on Applied Superconductivity 2025年

作者： Song, Yunxing Cheng, Zhiwen Jiang, Xunhuang Li, Jianglan Li, Liang Wang, Qiuliang Huazhong University of Science and Technology Wuhan National High Magnetic Field Center Wuhan430074 China Huazhong University of Science and Technology State Key Laboratory of Advanced Electromagnetic Technology Wuhan430074 China Chinese Academy of Sciences Institute of Electrical Engineering Beijing100190 China University of Chinese Academy of Sciences Beijing100049 China

As the core component of magnetic resonance imaging (MRI) system, superconducting magnet provides a high-intensity, stable and homogeneous magnetic field background for the system. The strength, stability, and homogeneity of the magnetic field directly affect the imaging quality of MRI. This paper presents the design, test and shimming of a 1.5 T Head-Only MRI superconducting magnet developed by the Wuhan National High Magnetic Field Center (WHMFC). The magnet consists of 7 primary coils and 2 shielding coils and is operated at an operating current of 510 A using liquid helium (LHe) bath cooling. The test has shown that the magnet reached the target field of 1.5 T directly after the first ramp-up without any quench. Under the magnetic field of 1.5 T, the magnetic field decay rate of the magnet is less than 0.02 ppm/hr. After 3 rounds of passive shimming, the magnet achieves a magnetic field inhomogeneity of 2.89 ppm over an imaging sphere within a diameter of 26 cm. The successful development of this magnet provides practical engineering validation for the lightweight technology of head-only MRI superconducting magnets. © 2002-2011 IEEE.

关键词： Superconducting magnets

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Tailoring the carbon nanofibers with Ti3C2Tx MXene as precursor to enhance the electromagnetic attenuation properties

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Materials Today Nano 2025年 30卷

作者： Chen, Pingan Hong, Sizeng Li, Xiangcheng Zhu, Yingli Chen, Fu Qiao, Mengke State Key Laboratory of Advanced Refractories Wuhan University of Science and Technology Wuhan430081 China Key Laboratory of High Temperature Electromagnetic Materials and Structure of MOE Wuhan University of Science and Technology Wuhan430081 China School of Information Science and Engineering Wuhan University of Science and Technology Wuhan430081 China

Carbon nanofibers can be widely used in the field of electromagnetic wave absorption due to corrosion resistance, low density and good chemical stability. Here, we report a strategy to achieve strong microwave absorption capability by adjusting the crystallinity of carbon nanofibers containing Al2O3 and TiO2. TiO2 with Ti3C2Tx MXene as a precursor decreases the crystallization temperature of Al2O3 from 1400 °C to 800 °C in the carbon nanofibers. The diameter distribution of carbon nanofibers is uniform, though the surface of carbon nanofibers is getting rough with Ti3C2Tx content increasing. The minimum reflection loss of carbon nanofibers is −55.78 dB at a thickness of 4.32 mm;the effective absorption bandwidth reaches 5.41 GHz (12.59–18 GHz) at a thickness of 1.67 mm, almost covering the Ku band. The excellent microwave absorption performance can be attributed to the synergistic effect of the non-crystalline carbon matrix and crystalline Al2O3/TiO2, in which the former improves impedance matching with free space, while the latter enhances the attenuation capability to the electromagnetic wave. © 2025

关键词： Impedance matching (electric)

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Impact of dielectric barrier discharge cold plasma on Dendrobium officinale polysaccharides: Physicochemical and functional properties

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International Journal of Biological Macromolecules 2025年 311卷 143740页

作者： Yu, Wujin Chen, Peng Xu, Xinhui Nie, Lanlan Huang, Zhenyu Muhammad, Ahsan Hafiz Wang, Yan Bu, Tingting Sun, Peilong Cai, Ming Department of Food Science and Technology Zhejiang University of Technology Hangzhou Zhejiang310014 China China National Light Industry China State Key Laboratory of Advanced Electromagnetic Engineering and Technology School of Electrical and Electronic Engineering Huazhong University of Science and Technology Wuhan430074 China State Key Laboratory in Quality Research of Chinese Medicine Institute of Chinese Medical Sciences University of Macau 999078 China

Dendrobium officinale has garnered significant attention due to its notable bioactivity and health benefits. The polysaccharide extracted from Dendrobium officinale (DOP) is the primary source of its functionality. However, its poor solubility and high viscosity necessitate the modification of its physicochemical properties. This study aimed to investigate the impact of cold plasma treatment on the physicochemical and functional properties of DOP. The results indicated that cold plasma treatment substantially increased the solubility of DOP from 87.5 % to 96.30 % and enhanced its hydrophilicity with a lower water contact angle, primarily attributed to the etching effect of plasma. Furthermore, the study confirmed the co-occurrence of cross-linking and depolymerization during the plasma discharge process. The plasma treatment reduced the viscosity of the polysaccharide solution by 10 folds and increased its thermal stability. The microstructure of the polysaccharide, examined by SEM and AFM, revealed that plasma treatment disrupted the cross-linking structure, leading to smooth agglomeration at high intensity. Moreover, the antioxidant capacity and immunoreactivity of plasma-treated DOP have been improved, and the free radical scavenging rate of the plasma-treated could reach 34.40 % at a concentration of 1 mg/mL, stimulating the secretion of cytokines TNF-α (increased 20.70 %), IL-1β (increased 26.94 %), IL-6 (increased 25.32 %), and IL-10 (increased 13.03 %) in in vitro cell tests. Accordingly, cold plasma treatment could be a novel approach to modifying polysaccharides and improving their potential applications in food and pharmaceutical sectors. © 2025

关键词： Plasma deposition

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Traceability Method of Measuring System for Arbitrary High-Voltage and High-Current Impulses

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IEEE Sensors Journal 2025年

作者： Yang, Ning Liu, Yi Lin, Mingxing Li, Liuxia Lin, Fuchang Long, Zhaozhi Diao, Yinglong Li, Wenting Fan, Jiawei Huazhong University of Science and Technology State Key Laboratory of Advanced Electromagnetic Engineering and Technology School of Electrical and Electronic Engineering Wuhan430074 China Huazhong University of Science and Technology Key Laboratory of Pulse Power Technology Ministry of Education School of Electrical and Electronic Engineering Wuhan430074 China State Grid Sichuan Electric Power Company Chengdu610041 China China Electric Power Research Institute 430072 China

High-voltage and high-current impulse waveforms, characterized by a diverse frequency spectrum, pose challenges for accurate traceability to national standards. Traditional methods for tracing impulse quantities to a single-frequency measurement standard are not universally applicable. This paper introduces a novel approach that establishes a general traceability method by mapping the impulse scale factor to a multi-frequency AC scale factor based on the energy spectrum, enabling indirect traceability to the power frequency standard under high-voltage or high-current conditions. A full-waveform inversion method is employed that integrates the frequency spectrum of measured impulse waveforms using fast Fourier transform (FFT) with the frequency response characteristics of the measuring system, which are determined through convolution based on square wave responses. This approach facilitates traceability of time parameters for arbitrary impulse waveforms. Experimental results demonstrate that the resistive impulse voltage divider's scale factor uncertainties at low and high voltages are 3.100×10-4 and 1.344×10-3, respectively. Additionally, the uncertainties for the T1 and T2 parameters of the inverted waveform of the attenuator are within 0.45% and 0.03%, respectively. These findings validate the effectiveness of our traceability theory. © 2001-2012 IEEE.

关键词： Electric frequency measurement

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Design of the high voltage isolation transmission module with low delay for ECRH system on J-TEXT

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Plasma Science and technology 2018年第2期20卷 19-25页

作者：马海燕夏冬辉王之江崔芳泰余振雄金易坤刘昌海 State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology

As a flexible auxiliary heating method,the electron cyclotron resonance heating（ECRH） has been widely used in many tokamaks and also will be applied for the J-TEXT *** meet requirements of protection and fault analysis for the ECRH system on J-TEXT,signals of gyrotrons such as the cathode voltage and current,the anode voltage and current,etc should be transmitted to the control and data acquisition *** the high voltage environment of gyrotrons,isolation transmission module based on FPGA and optical fiber communication has been designed and *** test results indicate that the designed module has strong anti-noise ability,low error rate and high transmission *** delay of the module is no more than 5 μs which can fulfill the requirements.

关键词： J-TEXT tokamak electron cyclotron resonance heating high-voltage isolation

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Equilibrium Reconstruction and Integration of EFIT with Diagnoses in J-TEXT Tokamak

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Plasma Science and technology 2016年第12期18卷 1225-1230页

作者：高海龙徐涛张帆简翔张晓卿杨州军高丽江中和庄革 State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology

The EFIT program is integrated with the high resolution laser polarimeter interferometer system（POLARIS）, the soft X-ray imaging diagnostic system（SXR） and the electron cyclotron emission radiometer（ECE） in the J-TEXT tokamak. Then some internal information about Faraday angle and the position of safety factor q=1 can be obtained as a constraint to EFIT. The modified EFIT code is used to calculate the internal parameters such as flux function, safety factor q, pressure and current density.

关键词： EFIT equilibrium reconstruction diagnoses

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Mode-Coupling Analysis of Parametric Decay Instability in Magnetized Plasmas

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Plasma Science and technology 2014年第9期16卷 809-814页

作者：袁媛江中和郭伟欣孙新锋胡希伟 State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology

In this paper, derived from Maxwell and fluid equations of plasmas, unified nonlinear wave equations are used to describe the parametric decay instability （PDI） in magnetized plasmas, and in view of mode-coupling, we can obtain all the possible PDI channels. By solving the nonlinear equations with a mode-coupling method, we obtain the growth rate of the PDI, of which all of the three waves are ordinary mode （O-mode） or extraordinary mode （X-mode） wave. Under the dipole approximation, an explicit formula of the growth rate of the X-mode and the condition of the equilibrium density scale are obtained. According to the existence conditions of three X-mode waves, this kind of instability might exist in ECRH with the second harmonic X-mode wave.

关键词： magnetized plasma parametric decay instability mode-coupling theory,growth rate

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Power dependence of density limit due to plasma-wall interaction in a burning plasma

arXiv

引用

arXiv 2025年

作者： Liu, Jiaxing Zhu, Ping Escande, Dominique Franck State Key Laboratory of Advanced Electromagnetic Technology International Joint Research Laboratory of Magnetic Confinement Fusion and Plasma Physics School of Electrical and Electronic Engineering Huazhong University of Science and Technology Wuhan430074 China Department of Nuclear Engineering and Engineering Physics University of Wisconsin-Madison MadisonWI53706 United States Aix-Marseille Université CNRS PIIM UMR 7345 Marseille France

The density limit is one of the major obstacles to achieving the desired fusion performance in tokamaks. However, the underlying physics mechanism for its recently observed power dependence in experiments has not been well understood or predicted in theory. In this work, the power dependent scalings of density limit are obtained based on the plasma-wall self-organization theory [D.F. Escande 2022 NF], which are able to match the power dependence of density limits in multiple tokamak devices. The key factors influencing the power dependence are found to be the plasma-wall sputtering and the particle confinement time. The effects of non-sputtered impurities and fusion products are further evaluated. This PWSO-density limit model is then extended to the burning plasma regime and used to predict the conditions for entering burning plasma. Copyright © 2025, The Authors. All rights reserved.

关键词： Tokamak devices

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Effects of Boundary Current on electromagnetic Dispersion Characteristics for a Relativistic Electron Beam

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Plasma Science and technology 2016年第1期18卷 51-57页

作者：肖集雄曾中夏冬辉王之江刘昌海 State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology

With betatron oscillation characteristics of the electron beam and ion channel effect taken into account,dispersion characteristics of electrostatic modes and TM modes for a relativistic electron beam guided by ion channel are *** relations are derived and solved numerically to investigate the dependence of the dispersion characteristics for electrostatic modes and TM modes on the betatron oscillation frequency and the ratio of the relativistic electron beam radius to the waveguide *** effects of the boundary current on the dispersion characteristic of the TM modes and the interaction between the betatron modes and TM modes are *** considering the boundary current,for a strong ion channel,a new low-frequency branch of the TM modes arises and the interaction frequency between the betatron modes and the TM01modes is increased with the same parameters.

关键词： dispersion characteristics electromagnetic eigenmodes betatron oscillation ion channel

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Grid Forming Converters in Renewable Energy Sources Dominated Power Grid:Control Strategy,Stability,Application,and Challenges

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Journal of Modern Power Systems and Clean Energy 2021年第6期9卷 1239-1256页

作者： Haobo Zhang Wang Xiang Weixing Lin Jinyu Wen State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology TBEA Sunoasis Company Ltd. the State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology

The renewable energy sources(RESs)dominated power grid is an envisaged infrastructure of the future power system,where the commonly used grid following(GFL)control for grid-tied converters suffers from lacking grid support capability,low stability,***,emerging grid forming(GFM)control methods have been proposed to improve the dynamic performance and stability of grid-tied *** paper reviews existing GFM control methods for the grid-tied converters and compares them in terms of control structure,grid support capability,fault current limiting,and *** the impact of fault current limiting strategies,a comprehensive transient stability analysis is *** addition,this paper explores the typical applications of GFM converters,such as AC microgrid and offshore wind farm high-voltage direct current(OWF-HVDC)integration ***,the challenges to the GFM converters in future applications are discussed.

关键词： Grid following(GFL)control grid forming(GFM)control high-voltage direct current(HVDC) microgrid renewable energy small-signal stability transient stability

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