Just Accepted manuscripts are peer-reviewed and accepted for publication. They are posted online prior to technical editing formatting for publication and author proofing.
Display Method:
Edge quality improvement of ghost imaging based on convolutional neural network
Zhang Hangyu, Wu Yi, Zhao Shuai, Feng Guoying
 doi: 10.11884/HPLPB202436.240030
[Abstract](12) [PDF 4103KB](1)
Abstract:
Scatter-shift ghost imaging edge extraction methods require multiple sampling of the object to obtain a high quality edge map. In order to solve the problem of many samples and long time when extracting the edge of the object by scatter-shift ghost imaging, convolutional neural network is adopted to the edge extraction experiment of ghost imaging. Firstly, the unknown image is irradiated by Walsh scattering, the sampled signal collected by the barrel detector is input to the ghost imaging edge extraction network as the image feature information, finally the edge information map of the detected object is directly outputted by the trained network, and the output of the convolutional neural network is optimized by using the non-maximum value suppression algorithm. The experimental results show that for the reconstructed object of 128×128 pixels, the signal-to-noise ratio and structural similarity index of the ghost imaging edge extraction network output edge pattern are 5 times and 2 times higher than that of the scatter-shift ghost imaging respectively when the sampling number is 1600, which successfully improves the quality of the ghost imaging edge extraction under the low sampling rate and reduces the sampling time. The ghost imaging edge extraction scheme using convolutional neural network is conducive to fast and high-quality edge detection of ghost imaging in practical applications of object recognition and security inspection.
Simulation research on energy distribution of light radiation from nuclear explosion
Han Xiaoxiang, Li Jun, Zhang Xin, Yuan Lin, Liu Yang, Wang Boyu
 doi: 10.11884/HPLPB202436.230406
[Abstract](15) [PDF 11383KB](2)
Abstract:
Light radiation is a crucial component of the energy produced in nuclear explosion, making the study of its space distribution highly significant. Here, we present the derivation of a formula for computing thermal energy induced by the light radiation of a nuclear explosion. The derivation integrates the fireball development laws with the transient energy dynamics of light radiation. The resultant formula exhibits a dependency on several factors, including the height of the explosion, the yield of the explosion, atmospheric attenuation coefficients, as well as the radius and temperature of the fireball. Via the creation of diverse maps and the adjustment of pertinent parameters, we conduct simulation calculations to elucidate the distribution patterns of the transient thermal energy from nuclear explosion light radiation. Furthermore, we incorporate the burn injury grading standards into the simulation by introducing a search function that autonomously categorizes the injury grading zones on the virtual map. What’s more, neural networks are employed to train the numerical models, aiming to discern the correlation between the parameters associated with nuclear explosions and the injury grading radius on the map. This innovative approach enables the direct prediction of the injury grading radius based on nuclear explosion parameters, significantly shorten the calculation process.
Predictive modeling of the surface pattern of double-sided polishing process of optical components
Mi Zhikai, Nie Fengming, Huang Siling, Xue Feng
 doi: 10.11884/HPLPB202436.240068
[Abstract](8) [PDF 7795KB](0)
Abstract:
Addressing the challenge of establishing a stable removal function for double-sided polishing to predict the finished surface profile, this paper builds on the principles of double-sided polishing. We use the coordinate transformation method to derive the relative velocity distribution equations for the upper and lower surfaces of the component. Subsequently, static pressure distributions on both surfaces are simulated using ANSYS software. The simulation data is then imported into Matlab and fitted with a polynomial method to determine the time-varying pressure distribution formulas for the component's surfaces. Based on the Preston equation, an expression for the correction coefficient K is derived. The value of the correction coefficient K is calculated to be 2.588×10−15 from four sets of polishing experimental data, enabling the construction of a predictive model for the surface pattern in double-sided polishing processes. The predictive model is ultimately validated through machining experiments. The experimental results indicate that the error in predicting the PV (Peak-to-Valley) value accounts for approximately 1.07% to 7.4% of the actual PV value after processing, demonstrating good agreement between the predicted model and the actual post-processing surface pattern.
A 10 kV hundred-nanosecond risetime hundred-microsecond pulse width rectangular pulse source
Tang Mengyuan, Jiang Zeyun, Ding Weidong
 doi: 10.11884/HPLPB202436.240092
[Abstract](20) [PDF 17415KB](1)
Abstract:
For requirement of quantity transmission in broadband measurement system, a unipolar rectangular pulse source is designed to realize 10 kV rectangular wave pulse output with MOSFET as the core component based on Marx circuit. The modular and miniaturization of the pulse generator is realized by using the stack structure to build the 12-stage prototype. The experimental results show that when the input voltage is 850 V, the proposed pulse source can generate a fast output pulse with 10 kV maximum voltage, rise time less than 100 ns, 200 μs pulse width under the capacitive load below 300 pF. The power supply can be used in rectangular wave response performance test of broadband measuring equipment or pulse power related applications.
Similarity analysis applied to nuclear criticality accident alarm systems
Xu Yuan, Jiang Shihang, Yang Haifeng, Yi Xuan, Shao Zeng
 doi: 10.11884/HPLPB202436.230368
[Abstract](15) [PDF 6290KB](0)
Abstract:
To determine the alarm threshold for criticality accident alarm systems (CAASs) used in facility monitoring, it is necessary to select appropriate benchmark experiments for validation. This paper constructs a simplified model and a representative virtual equipment room model, taking into consideration the characteristics of CAASs in the equipment room. The functionality of calculating sensitivity coefficients using the differential operator sampling approach in the Monte Carlo code RMC was implemented to solve the fixed source problem. Following that, a sensitivity and uncertainty analysis was conducted to examine the similarities between systems and explore the factors influencing them. The results indicate that the neutron source term spectrum and the concrete material significantly affect the similarity between systems. Additionally, the thickness of the concrete between the detector and the inner wall has a moderate influence on similarity, whereas the geometric position of the source term has a negligible impact. The impact of the spent fuel composition on similarity can be neglected. Based on the similarity analysis procedure proposed in this study, it is concluded that the simplified model exhibits a relatively high similarity to the virtual equipment room model. Hence, the research conclusions based on the simplified model are applicable to the virtual equipment room model, offering valuable insights for similarity studies of CAASs in engineering.
Parameter estimation method of Frequency hopping signal based on time-frequency transform and Waveform shaping
Wang Chuanchuan, Zhang Kuanqiao, Wang Manxi
 doi: 10.11884/HPLPB202436.240079
[Abstract](11) [PDF 1219KB](1)
Abstract:
In view of the adverse effect of noise on frequency hopping signal parameter estimation, a frequency hopping signal parameter estimation method based on time-frequency transform and waveform shaping is proposed. The time-frequency ridge is calculated by the short-time Fourier transform of the frequency hopping signal, the waveform shaping of the time-frequency ridge is processed to eliminate the false time-hopping interference caused by noise, and the hopping period sequence is obtained through the time-hopping sequence. The histogram of the hopping period sequence is calculated, and the value with the most occurrence times is selected to calculate the hopping speed of the frequency hopping signal. According to the hopping period sequence, signal of each hop is extracted respectively, and then the frequency is estimated. The effectiveness of the proposed method is verified by experiments, and the ideal estimation results of hopping time, hopping speed and frequency of frequency hopping signal under low signal-to-noise ratio are guaranteed by comprehensive use of time-frequency transformation and waveform shaping technology.
Research progress in radio technology based on Rydberg atoms
He Qing, Li Dong, Gu Li, Luo Siyuan, He Yudong, Li Biao, Wang Qiang
 doi: 10.11884/HPLPB202436.240061
[Abstract](55) [PDF 33429KB](11)
Abstract:
In recent years, the field of quantum information technology has experienced rapid growth, with a particular focus on electromagnetic sensors that utilize Rydberg atoms. Rydberg atoms, characterized by their high energy states, have garnered significant attention due to their highly sensitive response to external fields. These atoms offer several advantages, including self-calibration capabilities and direct traceability to the International System of Units (SI), which make them exceptionally suitable for applications in radio sensing and detection. Since Shaffer and others made a breakthrough in measuring microwave electric field intensity using the electromagnetic induced transparency effect of Rydberg atoms in 2012, the sensitivity and uncertainty of measuring microwave electric field intensity have significantly surpassed those of traditional microwave measurement results. Over the past decade, research centered around new theories and technologies, such as Rydberg atom superheterodyne technology, has enabled the measurement of electromagnetic wave frequency, polarization, phase, amplitude, and other parameters. Related engineering technologies are also experiencing significant growth, expected to have a disruptive impact on traditional radio technology. This comprehensive review aims to summarize the research progress in the field of Rydberg atom-based radio technology over the past ten years. It will start by examining the underlying principles of detection and then proceed to outline the developmental trajectory of this domain. Finally, the review will provide insights into the future trends and potential directions for the evolution of this technology.
Design and implementation of linear injector timing system for 300 MeV proton and heavy ion accelerator
Han Xiaodong, Liu Donge, Xu Zhe, Zhang Ruifeng, Li Shilong, Zhou Ruihuai, Cong Yan
 doi: 10.11884/HPLPB202436.240041
[Abstract](23) [PDF 10736KB](0)
Abstract:
A linear timing system was designed for the linear injector of the Harbin Institution of Technology’s Space Environment Simulation and Research Infrastructure (SESRI) -300 MeV proton and heavy ion accelerator. The linear timing system provides precise timing trigger signals for linear accelerator chopper system with pulse operation mode, low-level RF control system, beam current diagnostic and feedback system to meet the demands of physical beam tuning. The system hardware based on the design of Field Programmable Gate Array (FPGA), which realizes the precise timing control of related equipment of linear timing system in internal trigger mode and external trigger mode, as well as the control and safety interlock of chopper. The hardware can realize the optical signal communication, W5300 Ethernet communication, multiple relay outputs and multiple synchronized trigger signals with precise timing outputs. At the same time, the use of optical signal communication module will facilitate the cascade of systems and system scalability, which can meet the large-scale needs of linear gas pedal timing system. The user high level software is developed based on the distributed architecture of EPICS (Experimental Physics and Industrial Control System). The linear timing system has been successfully used in 300 MeV proton and heavy ion accelerator and SSC-LINAC of Institute of Modern Physics (IMP), and has operated stably and reliably for a long period of time without any failure.
Simulation analysis of indirect effects of lightning on airborne missiles
Fan Guangcheng, Yuan Feima, Zhang Lei, Lei Yuhu, Yang Gang, Li Kelian
 doi: 10.11884/HPLPB202436.240065
[Abstract](18) [PDF 7403KB](7)
Abstract:
As a suspension for military aircraft, missile has potential for being struck by lightning in special thunderstorm environments. To improve the lightning protection of airborne missiles, a simulation environment of military aircraft with missiles is built in CST software according to the testing methods in SAE ARP5416 standard. The lightning 1A zones are classified through electrostatic field simulation, and the indirect effects of lightning striking on this model are simulated under injection current method. Simulation results show that the head rear edge of missile (metal parts) and tail wing tip of missile are susceptible to initial attachment from lightning. When the head rear edge of the missile is attached by lightning, the extremely harsh electromagnetic environment occurs at the radome, and the equipment in cabin of carbon fiber reinforced plastic (CFRP) can be damaged owing to the strong electric field and the high voltage induced on cables. However, the electric field strength and induced voltage amplitudes on cables can be dropped in two orders of magnitude separately in the condition of aluminum plating inside the CFRP cabin.
Research on ATL law based on hydrostatic leveling system
Cheng Zhubing, Li Xiao, Wang Wei, Wu Enchen, Ding Ting, Zhang Qiuyu, He Xiaoye
 doi: 10.11884/HPLPB202436.230323
[Abstract](42) [PDF 7021KB](2)
Abstract:
For particle accelerators, ground deformation can cause beam distortion or even loss, so it is necessary to study ground deformation in particle accelerator field. By constructing two parallel distributed hydrostatic leveling systems consisting of 7 static leveling sensors spaced 10 m apart in the Hefei Light Source’s linear accelerator tunnel, this paper analyzed a total of three monitoring data collected by the two systems for a period of half a month, find the linear relationship present in the ATL law and obtain the constant values of the ATL law separately, and discover the correlation between the model constant A and seasons’ temperature. Finally, through data comparison, it was found that the periodic components in the relative motion of ground points are mainly affected by the earth tide.
A cascaded broadband choke device for the transmission shaft in the waveguide
Dong Tao, Wang Xiufang, Ni Tailai, Wang Hao, Wang Bangji, Liu Qingxiang
 doi: 10.11884/HPLPB202436.230401
[Abstract](27) [PDF 1955KB](2)
Abstract:
In this paper, a cascaded broadband choke device is presented, which can prevent microwave leakage by a transmission shaft in the waveguide. Utilizing the principle of impedance transformation, the bandwidth attributes of the cascaded broadband choke device are examined. It is discerned that augmenting the quantity of dielectric slices can enhance the bandwidth of the choke device. Furthermore, based on the principle of equivalent wavelength, escalating the dielectric constant of the dielectric slice can effectively reduce the choke device’s volume. An electromagnetic simulation software is employed to establish a model of a double-layer choke structure. This model is then used to simulate and analyze the impact of variables such as the number of dielectric slices, dielectric constant, and size on the choke structure’s performance. The simulation outcomes indicate that at a working frequency of 10 GHz, the leakage loss of the double-layer choke structure is less than −40 dB within a bandwidth range of 9.70 GHz-10.82 GHz, achieving a relative bandwidth of 8.2%. A simplified simulation model is subsequently utilized for physical fabrication and testing. The experimental findings not only corroborate the accuracy of the simulation results but also affirm the low-loss and wide-bandwidth characteristics of the proposed choke structure.
Commission method of the primary helium circulator of HTGR under variable resistance condition
Ye Lin, Yan Yijie, Xu Weiqiang, Zhao Feng, Chen Guangjian, Li Chao, Zhu Yingjie
 doi: 10.11884/HPLPB202436.230444
[Abstract](37) [PDF 1671KB](3)
Abstract:
During the commissioning of the primary helium circulator of the high-temperature gas-cooled reactor (HTGR), it could not complete the performance test of the full speed range, because the resistance of the primary loop was lower than the design condition. Based on the theoretical characteristics of the primary helium circulator and similar principles, a method for calculating the commission parameters of the primary helium circulator under different resistance conditions is developed. Combined with the monomeric test operating points of the primary helium circulator, accurately calculated the operating point parameters of the cold and hot performance tests of the primary helium circulator, and guided the completion of the full speed and full power performance tests of the primary helium circulator in HTGR. By comparing and analyzing the commission and factory test results of the primary helium circulator, the feasibility of this calculation method is verified, and provide correction factors for the conversion of working conditions between air medium and helium medium. Through comparing and analyzing the commission and operation data of the primary helium circulator, it can be seen that the commission conditions provided in this article have sufficient enveloping ability, which can cover all operating conditions of the primary helium circulator during the operation of HTGR. This proves that the variable resistance condition commission method of the primary helium circulator meets the performance verification requirements of HTGR, and it can be used to guide the primary helium circulator commission of subsequent HTGR.
Design and experiment of open waveguide array antenna with high power and high efficiency
Wei Yihong, Li Xiangqiang, Su Yiyu, Zhang Jianqiong, Wang Qingfeng
 doi: 10.11884/HPLPB202436.230421
[Abstract](41) [PDF 6863KB](14)
Abstract:
Aiming at the application requirements of array antenna with high-power capacity, high efficiency and low profile characteristics, a high-power capacity and high efficiency open waveguide array antenna is proposed and designed. The antenna consists of a compact 16-way waveguide power distribution network, 4×4 rectangular open waveguide unit cells and ceramic sealing radome. By designing the size of the open waveguide and loading E-plane metal bar on the surface of the open waveguide, the electric field distribution on the radiation aperture surface is more uniform, and the radiation gain of the unit cell is improved. The step matching structure is used to realize the size transformation from the output port of the waveguide power distribution network to the interface of the open waveguide unit cell, and the impedance bandwidth of the system is improved. The ceramic radome loaded on the array keeps the interior of the antenna in a vacuum state and improves the power capacity of the antenna. According to the application requirements of X-band high-power array antenna, a 16-element open waveguide array with a center frequency of 9.5 GHz is optimized and designed, the simulation results show that the aperture efficiency is greater than 90% and the reflection coefficient is less than -13.9 dB in the range of 9.25~9.65 GHz. The antenna is processed and tested, the measured antenna reflection curve and radiation pattern at the center frequency are in good agreement with the simulation results, the antenna gain at the center frequency is 21.7 dBi. The overall profile height of the antenna is twice the wavelengths at the central frequency, and the power capacity in vacuum obtained by simulation is 40 MW, which has the characteristics of high power capacity, high efficiency and low profile.
Simulation of coolant boiling phenomenon in sodium cooled fast reactor based on porous medium approach
Hui Tianyu, Tong Lili, Cao Xuewu
 doi: 10.11884/HPLPB202436.230408
[Abstract](35) [PDF 1914KB](3)
Abstract:
As the first stage of severe accidents in sodium cooled fast reactors, accurate prediction of the occurrence time and location of coolant boiling is of great significance for the safety assessment of Sodium Cooled Fast Reactors (SFR). Based on a two fluid six equation model, conservation equations are constructed for the gas-liquid two-phase flow of sodium. The evaporation-condensation model is used to characterize the interphase mass exchange, and explicit and implicit methods are used to calculate evaporation-condensation model. Constitutive relationships such as Sobolev resistance model, two phase flow heat transfer model, and phase momentum exchange are considered. A porous medium analysis approach which is suitable for simulating SFR coolant boiling was developed, and comparative verification was conducted using KNS-37 L22 loss of flow experiment data. L29 flow data is used to verify the applicability of the model. The results indicate that the established sodium boiling porous medium analysis approach can effectively simulate the boiling phenomenon. It predicts that the boiling time will be around 6.3 seconds, which is 0.2 seconds different from the experiment. The overall trend of temperature and flow rate changes are in good agreement with experimental data.
Research progress in deep learning for wavefront reconstruction and wavefront prediction
Qiu Congpan, Liu Guodong, Zhang Dayong, Hu Liusen
 doi: 10.11884/HPLPB202436.230430
[Abstract](66) [PDF 19076KB](19)
Abstract:
The combination of deep learning technology and adaptive optics technology is expected to effectively improve the wavefront correction effect and better cope with more complex environmental conditions. The research progress of applying deep learning in the direction of wavefront reconstruction and wavefront prediction is detailed, including the specific research methods and corresponding neural network structure design adopted by the researchers in these two research directions, and the performance of these neural networks in different practical application scenarios is analyzed, and the differences between the different neural network structures are compared and discussed, and the specific impacts of the structural differences are explored. The differences between the different neural network structures are compared and discussed, and the specific impacts brought by the structural differences are explored. Finally, the existing methods of deep learning in these two directions are summarized, and the future development trend of the deep integration of deep learning and adaptive optics technology is also prospected.
Articles in press have been peer-reviewed and accepted, which are not yet assigned to volumes /issues, but are citable by Digital Object Identifier (DOI).
Display Method:
Magnetohydrodynamic electromagnetic pulse produced by high altitude nuclear explosion
Wang Jianguo
 doi: 10.11884/HPLPB202436.240105
[Abstract](36) [PDF 5003KB](4)
Abstract:
The magnetohydrodynamic (late-time) electromagnetic pulse (E3) generated by high-altitude nuclear explosions has a serious impact on national key infrastructures such as the power system. Due to the complex mechanism of late-time electromagnetic pulse generation and many dependent factors, including explosion yield, explosion height, explosion orientation, explosion time, observation point position and soil conductivity, there is no available mature code that can simulate the whole generation process of late-time electromagnetic pulse. This paper introduces the generation mechanism of late-time electromagnetic pulse, discusses the relationship between the electric field of late-time electromagnetic pulse and the change of explosive yield of nuclear devices, explosive height, and atmospheric conditions. The electric field peak of E3A increases linearly with the explosion equivalent, while the electric field peak of E3B shows obvious saturation effect with the explosion equivalent increase. The current status of the simulation code of late-time electromagnetic pulse is analyzed, and it can provide a reference for further research on the numerical simulation method and code development of late-time electromagnetic pulse.
B-spline discontinuous Galerkin method for Maxwell’s equations
Hua Qinyi, Li Lin, Qi Hongxin
 doi: 10.11884/HPLPB202436.240076
[Abstract](26) [PDF 16279KB](2)
Abstract:
In the field of computational electromagnetics, the discontinuous Galerkin time domain (DGTD) method typically relies on irregular grid partitioning in model space and high-order polynomial interpolation calculations on elements. When comparing two-dimensional spatial quadrilateral mesh partitioning to triangular mesh partitioning at the same interpolation order, quadrilateral meshing offers fewer degrees of freedom and higher computational efficiency. However, traditional basis function spaces, relying on isoparametric transformations and polynomial tensor product interpolation, only possess low-order completeness on quadrilateral elements. Consequently, their stability and accuracy are significantly influenced by grid distortion. To address this challenge, this thesis proposes a high-order B-spline interpolation DGTD method based on irregular quadrilateral meshes for solving Maxwell's equations. The advantage of B-spline interpolation lies in its high-order completeness on irregular elements, effectively eliminating internal degrees of freedom within the elements. Furthermore, the coefficient matrices of the discrete system for Maxwell's equations also possess exact analytical forms. Analyzing the eigenmodes of cavities and the electromagnetic scattering of wedge structures, thus the maximum allowable time step increasing by 2.5 times and reducing the required unknowns by 25% compared to COMSOL software, the proposed algorithm exhibits notable advantages in terms of higher stability and precision.
Scattering correction method for cone-beam X-ray CT based on slanted-hole scattering correction plate
Guo Chenglong, Ni Peijun, Qi Zicheng, Fu Kang
 doi: 10.11884/HPLPB202436.230362
[Abstract](31) [PDF 21677KB](4)
Abstract:
Compared with two-dimensional fan-beam and parallel-beam CT systems, cone-beam X-ray CT has advantages such as fast scanning speed, high X-ray utilization efficiency, consistent axial and horizontal resolution of reconstructed images, and is the focus of current industrial CT technology development. However, the imaging quality is affected by the presence of scattered radiation. To reduce the impact of scattered radiation on image quality, this paper proposes a new scatter correction method based on a slanted-hole scatter correction plate. The principle and implementation of this method are thoroughly investigated. By acquiring the raw scan data and the scan data after using the slanted-hole scatter correction plate, scatter field data is obtained using interpolation and smoothing techniques. Then, by subtracting the scatter field data from the original data and performing reconstruction, scatter-free CT images can be obtained. Compared with the grating-based scatter correction plate method, the results show that in cone-beam CT scans of turbine blades, the contrast-to-noise ratio of typical regions (the cooling channels within the blades and the inner walls of the blades) is improved by 14.2% and 56.8% respectively with the slanted-hole scatter correction plate method, whereas with the grating-based scatter correction plate method, the same positions only show an improvement of 5.6% and 27.6% respectively. This validates the superiority of the slanted-hole scatter correction plate scatter correction method.
Design and implementation of a historical image data storage system for fluorescent target
Wu Han’nan, Yue Min, Ma Tao, Zhang Wei, Zhang Jie
 doi: 10.11884/HPLPB202436.230413
[Abstract](42) [PDF 2944KB](2)
Abstract:
A fluorescence target historical image data storage system based on MongoDB database was constructed to address the issues of historical image data storage: continuously increasing data generated by the system, and slow historical data retrieval speed of the Heavy Ion Research Facility in Lanzhou (HIRFL) fluorescence target. To save, observe and analyze fluorescence target beam images, this article establishes an EPICS based historical data archiving system to obtain PV (Process Variable) data of fluorescence target images. The obtained data is stored using MongoDB database sharding technology, and the image conversion and web page implementation are achieved through the Django framework. Image classification algorithms are applied in the system to improve data read and write speed. This system can stably obtain, store, and observe fluorescence target beam history images on HIRFL, providing convenience for beam analysis and tuning work.
Electromagnetic and thermal analysis research of high-order-mode coupler for 1.3 GHz 9-cell high performance superconducting cavity
Wang Zihan, Pan Weimin, Mi Zhenghui, Zhai Jiyuan, He Feisi, Sha Peng, Wang Guangwei, Liu Ming
 doi: 10.11884/HPLPB202436.230425
[Abstract](48) [PDF 8945KB](6)
Abstract:
The Institute of High Energy Physics of the Chinese Academy of Sciences completed the research and development of the high quality factor 1.3 GHz superconducting cryomodule in June 2023, taking the lead in the world to realize the technical route of the medium temperature baking. Eight 1.3 GHz 9-cell superconducting cavities with the medium temperature baking process are integrated. During the integration test of the cryomodule, the temperature of the high-order mode (HOM) coupler of the superconducting cavity was abnormal, which made the superconducting cavity unable to work stably under high gradient. In this paper, the electromagnetic analysis of the high-order-mode coupler is carried out by the HFSS software and eigenmode Solver in CST software and the thermal analysis of the high-order-mode coupler is carried out by theory and Ansys Workbench software. Combining with the high-power experiment of cavity, the cause of the abnormal performance of the superconducting cavity was found. Also, the cooling structure of the HOM coupler in the superconducting cavity was further optimized to solve the instability of the superconducting cavity under high gradient in the module.
Two-dimensional simulation of dense plasma focus
Ou Haibin, Duan Shuchao, Wang Ganghua, Xiao Jinshui, He Jialong, Xie Long, Xiao Bo, Kan Mingxian
 doi: 10.11884/HPLPB202436.240001
[Abstract](52) [PDF 2576KB](5)
Abstract:
To investigate the motion law of the plasma sheath in a dense plasma focus (DPF) device and the influence of related design parameters, this paper uses a self-developed FOI program to conduct two-dimensional magnetohydrodynamic simulation of the plasma sheath motion process and focus formation process in the Mather type discharge chamber structure, and obtains results similar to the visible light experimental images of the Lawrence Livermore National Laboratory in the United States. At the same time, the influence of different pressure, current, anode radius and cathode-anode gap on the motion law of the plasma sheath is explored. The calculation results show that the plasma sheath will compress the gas radially with a certain degree of curvature, which is one of the reasons for the instability phenomenon; the axial velocity of plasma sheath is inversely proportional to the square root of pressure, and is proportional to the current. The larger the anode size of the device, the smaller the axial velocity of sheath. To increase the current, it is necessary to extend the anode length to match the focusing time with the current peak. The gap between cathode and anode has little effect on the axial motion process of plasma sheath near the anode.
Simulation and optimization of novel movable TEM horn radiating-wave simulator
Zhu Xiangqin, Wu Wei, Cai Libing
 doi: 10.11884/HPLPB202436.240093
[Abstract](34) [PDF 2177KB](4)
Abstract:
To improve the low frequency radiation characteristics of the radiating-wave simulator based on transverse electromagnetic (TEM) horn, a novel movable simulator made up of exponential-type TEM horn, two vertical perfect electric conductor (PEC) plates at its aperture, two sloping PEC plates and parallel resistance is designed firstly. The effect of different exponential tapered rates, the height of the two vertical PEC plates, the width of the source port and the parallel resistance at the end of the two sloping PEC plates to the near-field radiation performance of the novel simulator is simulated and optimized by finite-difference time-domain (FDTD) method. The radiation characteristics of the optimized novel simulator and its arrays is also given. The calculation results show that, the full width at half maximum (FWHM) of the electric field at the testing point which is 3 m away from the optimized novel simulator’s aperture center reaches 18.95 ns, and the optimized novel simulator’s sizes are 6 m×6 m×6.24 m while those of the normal simulator must be 9 m×12 m×6.8 m to get the same low-frequency radiation performance as that of the optimized novel simulator. And higher peak-value of the electric field at the testing point of the optimized novel simulator can be got compared with the normal simulator. In addition, the ratio of the delayed oscillation’s amplitude of the electric field in time-domain at the testing point of the optimized novel simulator to its peak-value is significantly reduced compared with that of the previous studies, while the peak-value of the testing point of the optimized novel simulator keeps high. The electric field’s peak value at the center point in the testing plane of the optimized novel simulator’s 2 × 2 array model is the largest, and the effective region meeting the requirement of field 6dB uniformity on the testing plane of 2 × 2 array model has the largest domain; The effective region on the 2 × 2 array model’s testing plane has the largest horizontal range, followed by 2 × 1 array model; The effective regions on the testing planes of 2 × 2 array model and 1×2 array model have the largest vertical range.
Calibration of the tracker’s angle measurement error for linac control network
Zhang Yifei, Dong Xiaohao, Chen Jiahua, Sun Xiaopei, Liu Fangfang
 doi: 10.11884/HPLPB202436.230374
[Abstract](15) [PDF 1031KB](1)
Abstract:
Linac control network is the reference for optical axis transmission. According to the layout of key equipment in linac tunnel, the control network is laid out on the ground and wall of the tunnel. Tracker is the main instrument for measuring linac control network, and the angle measurement error is a key factor affecting the accuracy of the tracker. Based on the layout of wall and ground network points and the measurement plan, laser tracker’s angles were decomposed as horizontal and vertical angles in all measurement states. Then, through the linkage testing of high-precision CMM and laser trackers, all the decomposed angles were calculated, and the calculated values are used to correct the tracker’s measurement angles. Based on the test results, regardless of the measurement state, measured angle of the tracker is larger than the calculated value. The ground network points’ vertical angle deviation and horizontal angle deviation almost equal to the nominal accuracy of the tracker. When the horizontal angle of wall points exceeds 15°, deviation increase significantly, and the deviation should be corrected while measuring the wall network points.
Design of a high-power miniaturized waveguide E-plane heterodyne power combiner
Su Yiyu, Li Xiangqiang, Wei Yihong, Zhang Jianqiong, Wang Qingfeng
 doi: 10.11884/HPLPB202436.230433
[Abstract](57) [PDF 12565KB](12)
Abstract:
The existing heterodyne power combiners are not suitable for applications where input and output signals need to be in the same direction with limited space. To solve the problem, this paper designs a high-power and miniaturized heterodyne power combiner operating at frequencies of 9.3 GHz and 9.7 GHz. Based on the traditional filter-based heterodyne power combiner, the proposed design utilizes an over-mode rectangular waveguide E-plane power combiner. The waveguide filters are parallel and the input ports are also located on the same plane, so that the combiner is suitable for the specific applications. The sizes of the rectangular waveguide are reduced to suppress higher-order modes. Besides, the distance between mode strips is decreased in integer multiples of half-wavelength of the waveguide to compresses the overall length with high power capacity. The combiner has a length of 9.2λ, a width of 1.5λ and a height of 2.8λ, while λ is the wavelength corresponding to the frequency of 9.5 GHz in free space. At 9.3 GHz and 9.7 GHz, the return loss of the combiner is more than 20 dB, its combining efficiency is more than 98% , and the isolation between input ports is more than 20 dB. At microwave pulse breakdown threshold of 80 MV/m, the combiner provides a power capacity of 310 MW.
Cover and Contents
Cover and Contents, High Power Laser and Particle Beams, No 5 Vol 36, 2024
Editorial Office
[PDF 8122KB](34)
Pulsed Power System
Compact pulsed-power circuit methods and practice
Jiang Weihua, Tokuchi Akira, Sugai Taichi, Yu Liang, Feng Yu, Zhuang Longyu, Ren Xiaojing, Yang Junxiang
2024, 36: 055001.   doi: 10.11884/HPLPB202436.240053
[Abstract](278) [PDF 7166KB](113)
Abstract:
This review article aims at summarizing the basic principles of circuit methods used in compact pulsed-power generators. The concept of energy storage and voltage adding are explained followed by the descriptions on switching unit design and control signal generation. Some examples of applications of these circuit methods are given, including Marx circuit using capacitor energy storage, Marx circuit using inductive energy storage, Marx circuit using hybrid energy storage, linear transformer driver (LTD) circuit using capacitive energy storage and LTD circuit using inductive energy storage.
A design of B-dot calibration simulator for azimuthal transmission line
Zhang Xinjun, Luo Weixi, Hu Yixiang, Yin Jiahui, Zhou Wenyuan
2024, 36: 055002.   doi: 10.11884/HPLPB202436.230341
[Abstract](108) [PDF 3310KB](27)
Abstract:
An off-line calibration platform is designed based on the requirement of off-line calibration of induction cavity azimuthal transmission line current probe. The analog device is a flat-plate transmission line structure, which has lower distortion than on-line calibration. The source of cross-platform calibration error is analyzed, and the measures to reduce the error are put forward. The analysis shows that the installation eccentricity and probe longitudinal installation depth are the biggest sources of cross-platform calibration error, which need to be paid attention to in engineering design. An off-line calibration platform is established and the error analysis is carried out. As a result, 3.3% cross-platform calibration error is obtained.
High voltage damped oscillator based on interstage self-triggering Marx circuit
Chen Yufeng, Wang Qingfeng, Li Xiangqiang, Zhang Jianqiong
2024, 36: 055003.   doi: 10.11884/HPLPB202436.230360
[Abstract](145) [PDF 2743KB](62)
Abstract:
To increase the output voltage and reduce the volume and cost of the high voltage damped oscillator, a 4×4 stage self-triggering Marx structure damped oscillator model is established in this paper. In this model, the main switch of each stage adopts series IGBTs module based on capacitor trigger mode. Only one isolated signal is provided to control the turn-on and turn-off of the primary discharge switch tube. The grid of the adjacent discharge tube is automatically charged and discharged through the interstage capacitance to make it turn-on and turn-off. The model improves the working voltage of Marx single stage and simplifies the driving circuit of each stage, and solves the problem of dynamic and static voltage equalization of switching tube by adding buffer circuit. Based on this topology, a prototype of a high-voltage damped oscillator is built, which outputs 16 kV damped oscillation waveform with a frequency of 1 MHz on an inductive load. The rise time of the waveform is about 75 ns, and the repetition frequency is 500 Hz. The prototype is small in size and stable in operation, which verifies the feasibility of the scheme.
Research advancements of small-scale flash X-ray machine
Hu Hanpeng, Huang Yaqi, Zhang Zhenming, Zhang Xiulu, Yuan Changying
2024, 36: 055004.   doi: 10.11884/HPLPB202436.240020
[Abstract](187) [PDF 16195KB](63)
Abstract:
Flash X-ray radiography is often used to photograph the internal structure and hydrodynamic behavior of high-speed moving objects, and has gradually expanded to the fields of industrial flaw detection, precision system state detection and so on. This paper summarizes the research process and progress of small flash X-ray machine (SFXM), relating to four main technical routes of Marx generator, pulse forming line, fast pulse linear transformer, high-voltage transformer, and two key components of X-ray diode and switches. The research status of small flash X-ray radiography system is discussed, and the shortcomings of mature commercial small X-ray machines abroad and domestic commercial products are explored, The development trend of SFXM in the future is analyzed, which provides reference and basis for the research and development of SFXM and the exploration of commercial popularization.
Pulse Power Source Components
Design of discrete magnetic coupling drivers for high-frequency nanosecond pulse modulator
Chen Lei, Li Guochao, Zhang Ge, Zhu Caihui, Qiu Jian, Zhao Hui, Liu Kefu
2024, 36: 055005.   doi: 10.11884/HPLPB202436.230306
[Abstract](120) [PDF 6334KB](36)
Abstract:
With the increasing and extensive applications of high-voltage nanosecond solid-state pulse generators in various fields such as biology, industry, and environment, the pulse waveform, voltage amplitude, pulse duration, and pulse repetition frequency have become essential controllable variables for specific pulse power applications. To further reduce the size and cost of the pulsed power supply, a high-voltage nanosecond pulse modulator with high repetition frequency is proposed with positive Marx circuit, drivers with multiple pulse transformers as the core, and ns rising time. This driver enables the design of a high-voltage nanosecond pulse modulator with ns-level rise time and high repetition frequency. The proposed driver features a compact structure and eliminates the need for multiple isolated power supplies for driving. It allows the gate voltage of two MOSFETs to rise and fall rapidly and synchronously at a high repetition frequency, enabling the generation of gate voltage with controllable amplitude within one hundred nanoseconds. In the case, not only the maximum pulse width is not limited by the magnetic core saturation, but also the negative bias voltage can reliably turn off the switch, improving the reliability of the circuit. In addition, the influence of different turns and magnetic core materials on the driving waveform is studied. A 14-stage pulse modulator prototype is developed. Test results show that the output voltage and pulse width of the modulator based on the drivers are continuously adjustable, with the ability to change the pulse profile. The maximum output voltage reaches 5.5 kV with 100 ns to 50 ms width, minimum rise time of approximately 18 ns, and a continuous repetition frequency of 100 kHz.
Design of high voltage constant current charging power supply based on LC series resonance
Jiang Jinbo, Xu Lin, Luo Zheng, Yang Wen, Tang Ming, Yao Yandong, Chen Rui
2024, 36: 055006.   doi: 10.11884/HPLPB202436.230295
[Abstract](152) [PDF 4448KB](78)
Abstract:
LC series resonant high voltage constant current charging power supply can realize high efficiency and fast charging of the capacitor and has an excellent capacity of anti-load short-circuit, hence it has extensive application prospects in high repetition frequency pulsed power systems. The efficiency of the charging power supply is a crucial factor to determine the ability of the system to operate at repetition rate. Improving efficiency is the primary goal of designing high-voltage capacitor charging power supply. According to the working principle of LC series resonant circuit, it is analyzed that the operating mode of power supply, the switching frequency of the inverter bridge and the distribution parameters of the high-frequency transformer are the main ingredients affecting the efficiency. For a DC power supply with a power of 10 kW and an output voltage of 40 kV, the main circuit parameters were calculated and the circuit model was established using Pspice to verify its accuracy. The soft switching technology was used to reduce the switching loss, and the high frequency transformer with smaller distribution parameters was designed to further improve the efficiency. On this basis, the overall structure design of the power supply was completed. Finally, the charging characteristics of the power supply were tested. Experimental tests indicate that the power supply can charge a 0.1 µF capacitor to 39.5 kV within 37 ms, and the charging efficiency of the power supply is 87.1%.
Design and experiment of a sub-nanosecond repetition rate pulse signal generator
Feng Chuanjun, Dai Wenfeng, Xu Le, Wang Chuanwei, Fu Jiabin
2024, 36: 055007.   doi: 10.11884/HPLPB202436.240022
[Abstract](107) [PDF 1179KB](47)
Abstract:
The repetitive narrow pulse signal generator with a sub-nanosecond front, high-voltage amplitude, and approximately Gaussian single-cycle waveform is extensively applied in areas such as ultra-wideband detection and electromagnetic compatibility testing. This paper introduces the design of an all-solid-state repetitive pulse generator utilizing a Marx circuit architecture, which incorporates components like mica capacitors, avalanche transistors, surface-mount technology resistors, and inductors. To meet the signal output specifications, the printed circuit board layout and microstrip lines have been optimized. Through fine-tuning the matching circuit element parameters, the generator successfully delivers a unipolar negative pulse signal with a peak value of approximately 1 kV, a pulse width of around 650 ps, a leading edge of approximately 450 ps, and a trailing edge of about 700 ps across a 50 Ω resistive load. The resulting pulse waveform exhibits similar, smooth, and steep leading and trailing edges, achieving a repetition rate of 10 kHz. Both the peak value and full width at half maximum jitters are maintained at less than 10%.
Design of high-power repetitive pulse laser power supply
Li Helong, Xu Jian, Yang Zhiqing, Song Jiahao, Wu Zhouyu, Tang Yihui, Zhao Shuang, Ding Lijian
2024, 36: 055008.   doi: 10.11884/HPLPB202436.240045
[Abstract](131) [PDF 3469KB](42)
Abstract:
This paper proposes a design method for a high-power pulsed power supply for YAG laser systems, which is capable of realizing high-energy repetitive pulse with flexible voltage regulations. The power supply consists of an LC resonant converter as the charging network and a thyristor-based pulse forming network. Based on the proposed design approach, a 7 kW prototype is developed, which is able to output maximum voltage of 2.2 kV with a repetitive frequency ranged from 1 to 10 Hz. Moreover, the developed power supply is able to release up to 700 J of the energy on the xenon lamp.
kHz repetition rate pulse power source based on tri-coaxial cable Blumlein lines driven by hydrogen thyratron
Shen Yi, Huang Ziping, Zhang Huang, Liu Yi, Ding Mingjun, Xia Liansheng
2024, 36: 055009.   doi: 10.11884/HPLPB202436.230420
[Abstract](113) [PDF 8547KB](47)
Abstract:
Flash X-ray photography technology has important scenarios in military and civil fields. According to the requirement of high repetition rate of the linear induction a ccelerator, we put foruarc a pulse power source scheme based on tri-coaxial cable Blumlein lines driven by hydrogen thyratron. A tri-coaxial cable was designed and developed. The conduction characteristics of hydrogen thyratron were studied. The verification setup for the pulse power source was built. The experimental research on kHz repetition rate pulse power source and kHz repetition rate pulse power source driving induction cavity was carried out. The results show that the tri-coaxial cable Blumlein lines pulse power source driven by hydrogen thyratron can realize the kHz repetition rate square wave output with excellent waveform quality.
High Power Switch
Development and validation of V/N gas switches for photo conductive semiconductor switch triggers
Song Yuhui, Wang Lingyun, Zhou Liangji, Liu Hongwei, Zhang Dongdong, Chen Lin, Yuan Jianqiang, Deng Minghai, Xie Weiping, Gao Bin, Wang Ruijie
2024, 36: 055010.   doi: 10.11884/HPLPB202436.230347
[Abstract](116) [PDF 6607KB](63)
Abstract:
To meet the requirements of multi-channel precise synchronous trigger switch, photo conductive semiconductor switch (PCSS) is combined with V/N gas switch, which takes advantage of the photoelectric isolation, low trigger threshold, low delay time jitter and photoelectric isolation of PCSS, as well as the advantages of high operating voltage and strong load capacity of V/N gas switch. The core of the combination of the two switches is that the structural parameters of the V/N gas switch match the parameters of the PCSS trigger loop. The structural capacitance, trigger loop oscillation parameters and switching electric field distribution of the V/N gas switch are analyzed and calculated. The relationship between the structural capacitance of the V/N gas switch and the oscillation loop composed of PCSS and series inductors is studied. The self-breakdown voltage curve, on-delay time and delay time jitter of the switch under different under voltage ratios are obtained. The performance of the V/N gas switch for PCSS triggering is preliminarily verified.
Research on working characteristics of hydrogen thyratron
Zhao Yanhao, Rao Bo, Yang Yong, Yu Haojun, Zhang Ming
2024, 36: 055011.   doi: 10.11884/HPLPB202436.240040
[Abstract](96) [PDF 1578KB](36)
Abstract:
The working characteristics of the hydrogen thyratron and the optimization effect of the potential equalization treatment are investigated experimentally. The experiments show that the heating voltage has great influence on the working characteristics of hydrogen thyratron, on the premise of no self-discharge phenomenon, using higher heating voltage can obtain better conduction performance. The differences of trigger pulses and anode voltages have little effect on the conduction performance of hydrogen thyratron. Using resistors to equalize the voltage of hydrogen thyratron can make the voltage distribution more uniform and alleviate the phenomenon of self-discharge. The research provides reference and guidance for the use of hydrogen thyratron.
Study on glow discharge triggered repetitive frequency pseudospark switch
Ding Wenjing, Feng Jinjun, Zhang Ming, Yang Hongfei
2024, 36: 055012.   doi: 10.11884/HPLPB202436.240036
[Abstract](103) [PDF 2984KB](40)
Abstract:
The pseudospark switch works in the left branch of Paschen curve with low gas pressure, and it has the advantages of ns-level breakdown time, 100 kA-level pulse current and long lifetime. High pulse repetition frequency (PRF) pseudospark switch are widely used in both civil and military fields. This paper focuses on the double-pulse trigger structure and presents the design of a switch with this structure, which is tested with 10 kV anode voltage for different gas pressure, pre-trigger voltage and main trigger voltage. The corresponding relationship between the gas pressure, the two trigger voltages and trigger current are calculated respectively. In addition, the influence of pre-trigger and main trigger pulses on the trigger process is analysed. The results show that the minimum trigger voltage is only 100 V, and the switch can work stably with high repetition frequency.
High Voltage Insulation and Discharge
Influence of auxiliary discharge needle on direct current self-breakdown characteristics of the gas gap
Shi Ling, Xie Linshen, Guo Fan, Jia Wei, Wang Haiyang, Chen Zhiqiang, Cheng Le, Wang Yi, Wu Gang, Xiao Jing, Mei Kaisheng, Wang Gefei, Hua Jiantao
2024, 36: 055013.   doi: 10.11884/HPLPB202436.230371
[Abstract](79) [PDF 1108KB](27)
Abstract:
To reduce the jitter of the direct current self-breakdown voltage, and not affect the self-breakdown voltage as much as possible, an auxiliary discharge electrode structure with an auxiliary discharge needle implanted in the cathode center is designed based on the discharge gap of the annular electrode. The influence of the diameter, length and top chamfer of the auxiliary discharge needle on the field distortion is studied by electric field simulation. The direct current self-breakdown characteristics of the gas gap without and with auxiliary discharge needle in dry air and SF6 gas are studied by experiments. The results show that the smaller the diameter and the longer the length of the auxiliary discharge needle, the weaker the shielding effect of the electrode ring on the electric field, the stronger the field distortion intensity; the influence of the implatation of auxiliary discharge needle on the direct current self-breakdown of SF6 gas discharge gap is small, and with the increase of the field distortion coefficient, the percentage drop of self-breakdown voltage of dry air at the same air pressure is 2-3 times that of SF6 gas; the auxiliary discharge needle has a beneficial effect on the breakdown stability of dry air and SF6 gas discharge gap under the condition of direct current , the dispersion reduction percentage is about 25% higher than that without auxiliary discharge needle.
Breakdown characteristics of pre-ionization trigger gap in different gases under bipolarity pulse
Wang Yi, Guo Fan, Chen Zhiqiang, Jia Wei, Wang Gefei, Shi Ling, Xie Linshen, Wu Gang, Wu Wei
2024, 36: 055014.   doi: 10.11884/HPLPB202436.230392
[Abstract](107) [PDF 2226KB](47)
Abstract:
The breakdown characteristics of trigger gap for the pre-ionization switch in N2, the mixture of N2 and SF6 and SF6 atmosphere under positive and negative pulse were investigated for the higher voltage grade and bipolarity application. The relationships between the breakdown voltage and delay time of the pre-ionization gap and the pressure of different kinds of gases were obtained, and the breakdown characteristics were compared for the pre-ionization gap under positive and negative polarities. The results of the experiment demonstrated that the breakdown process of the gap in N2 was more stable, and the linearity of breakdown voltage varying with pressure in N2 was the best among the three kinds of gases. The breakdown voltage was saturated only in SF6 with the increase of gas pressure. The breakdown voltage of the gap under negative polarity was higher than that under the positive at some certain values of the pressure, and this phenomenon might suggest that there was a polarity effect upon the breakdown process of pre-ionization gap. Compared with the mixture and N2, the absolute differences between negative and positive polarity for both breakdown voltage and delay time in SF6 were relatively higher. N2 should be preferred as the insulating medium for the pre-ionization gap to reduce the synchronization delay difference of the bipolar self-triggered switches. The polarity effect of the pre-ionization gap and the distinctions among the different kinds of insulated gas medium should be paid more attention in engineering applications for the pre-ionization gap.
Vacuum surface flashover characteristics of cross-linked polystyrene under high repetition rate burst multi-pulse loading
Huang Ziping, Li Yuan, Deng Xu, Li Feng, Li Xin
2024, 36: 055015.   doi: 10.11884/HPLPB202436.230337
[Abstract](104) [PDF 2986KB](48)
Abstract:
Based on the requirement of high current multi-pulse accelerator, the surface flashover characteristics of cross-linked polystyrene (XLPS) material under burst multi-pulse in vacuum were studied experimentally. Vacuum surface flashover experiments were carried out with XLPS samples placed in flat electrodes under single pulse and three pulses with interval of 500 ns. Special phenomena such as continuous decrease of equivalent impedance of vacuum surface before flashover and continuous maintenance of flashover channel after pulse end were observed, and statistical data of vacuum surface flashover of XLPS materials under corresponding conditions were obtained. On the basis of experiments, the flashover characteristics of XLPS in vacuum under high repetition rate multi-pulse loading are analyzed, which provides experimental basis for insulation design of high repetition rate multi-pulse accelerator.
Development and application of experimental platform for vacuum insulator stack
Zhou Yawei, Hu Yixiang, Yang Shi, He Deyu, Yin Jiahui, Luo Weixi, Zhang Xinjun
2024, 36: 055016.   doi: 10.11884/HPLPB202436.230410
[Abstract](105) [PDF 1566KB](40)
Abstract:
The study of vacuum surface flashover along the insulator ring was carried out. An experimental platform for vacuum insulator stack was built. The influence of flashover among insulator ring on the voltage of the vacuum insulator stack was evaluated by equivalent circuit model. Vacuum surface flashover along the three kinds of material insulator stacks were carried out, which verify the availability and reliability of the experimental platform. This work provides a reference for the engineering research of the vacuum insulator stack of pulse power device, and also provides an experimental platform for research of new insulation materials.
Two-stage microstructure on surface of vacuum polymer insulators
Huo Yankun, Liu Wenyuan, He Yajiao, Ke Changfeng, Cai Libing, Bai Xianchen, Cheng Jun
2024, 36: 055017.   doi: 10.11884/HPLPB202436.230423
[Abstract](86) [PDF 6407KB](28)
Abstract:
In a previous work, a two-stage microstructure was proposed and demonstrated to be able to sharply improve surface flashover voltage of polymer insulators in vacuum. In this paper, the two-stage microstructure was separated into two sub-structures, i.e., surface micro-groove structure and surface micro-hole structure, to study the voltage improvement mechanism in the two-stage microstructure. Through the synthesis of a composite material, laser treatment and acid corrosion, the two-stage microstructure was prepared as well as the two sub-structures. Flashover test of the insulators with the three kinds of surface structures showed that construction of micro grooves and micro holes on the surface of insulators could both enhance the surface flashover strength and their combination could further enhance the flashover strength. The results indicate that through proper combination of different kinds of surface structures multiple suppression of the flashover could be achieved and the surface flashover voltage could be further improved.
High Power Microwave and High Power Electromagnetic Pulse
Power synthesis method of Ricker pulse and its radiation efficiency
Xie Jiyang, Jiang Zheng, Wei Zhaohuan, Yang Hongchun
2024, 36: 055018.   doi: 10.11884/HPLPB202436.230285
[Abstract](74) [PDF 1813KB](25)
Abstract:
This article investigates the Ricker pulse to address the issue of low radiation efficiency in time-domain antennas. Firstly, it highlights the high center frequency of the Ricker pulse, which is advantageous for improving antenna radiation efficiency. Then it proceeds to explain the power synthesis method for generating Ricker pulses, derives a theoretical formula for the optimal delay of synthesizing high-order Gaussian pulses, starting with precise time delay control. It describes the design of a unipolar pulse and the optimization of its falling edge using the sharpening capacitor method. With this unipolar pulse as a foundation, a Ricker pulse is designed, featuring a peak-to-peak value of 5.1 kV, a main peak half-width of 350 ps, and a center frequency of 0.5 GHz. To verify the correctness of the analysis, the article proposes a simple method to calculate the radiation efficiency of all-metal time-domain antennas. Both the designed Ricker pulse and a unipolar pulse with the same pulse width are used to excite the same antenna. The results demonstrate that the amplitude radiation efficiency of the single-pole pulse is only about 60%. In contrast, the Ricker pulse achieves over 80% efficiency. Similarly, the power radiation efficiency of the single-pole pulse is less than 40%, while that of the Ricker pulse can exceed 60%. The utilization of Ricker pulses as excitation has proven to be highly effective in enhancing the radiation efficiency of antennas, thereby minimizing the potential damage to transmission systems caused by reflected power. Additionally, this technique holds immense value in antenna miniaturization and exhibits promising applications in time-domain technologies like ground penetrating radar and high-power microwave sources.
A compact PFN-Marx repetitive pulsed power source
Wu Youcheng, Feng Chuanjun, Fu Jiabin, Dai Wenfeng, Cao Longbo
2024, 36: 055019.   doi: 10.11884/HPLPB202436.230354
[Abstract](127) [PDF 2409KB](48)
Abstract:
A compact repetitive pulse power source is developed as an experimental platform for high power relativistic magnetron with low magnetic field. To obtain better output pulse waveform with a compact structure, the pulsed power source designed based on PFN-Marx technology has a coaxial structure. A circular pulse forming net (PFN) is devised out with the impedance of 4 Ω, working voltage of 50 kV, and electrical length of 53 ns, consisting of 13 ceramic capacitors with the capacitance of 1nF. Two PFN devices in series by a gas switch and an insulation plate form a circular high-voltage pulse generation module. Multiple pulse generation modules are coaxial and stacked in a metal cylinder. Inductive isolation is used between the modules. After all switches are turned on, all modules are discharged in series to generate a fast rising-time high-power square wave pulse. Moreover, repetitive operation is achieved through synchronous control of the trigger switch and charging power supply. In experiments the 22-stage PFN-Marx pulsed power source developed was charged to 51 kV, and a high-voltage square wave pulse of 516 kV was obtained on a load of 84 Ω, with pulse width (FWHM) of 104 ns, flat top of 63 ns and rising-time of 11 ns. This power source can operate stably at a repetition rate of 20 Hz for 15 s.
Research progress on power system effects in late-time high-altitude electromagnetic pulses environment
Liu Tongyu, Li Li, Wang Ya’nan, Tian Yihan, Zhao Yuyang, Wang Yihuan, He Yuheng, Meng Wei, Cai Linglong, Ma Zhiqin, Li Xingwen, Ding Weidong
2024, 36: 055020.   doi: 10.11884/HPLPB202436.240042
[Abstract](132) [PDF 28838KB](46)
Abstract:
High-altitude electromagnetic pulse (HEMP), as a wide-area electromagnetic attack method, can have severe impacts on the power equipment and even collapse the power infrastructure, posing significant challenges to the electromagnetic safety of novel power systems. This article focuses on the latest research progress on the power system effects in late-time HEMP environment. Firstly, the mechanism of geomagnetic disturbance generation and the calculation method of induced geomagnetic field are analyzed. The calculation method of geomagnetically induced current (GIC) is provided. Then, the effects and mechanisms of typical primary power equipment, such as power transformers, current transformers, circuit breakers, etc. under extreme GIC conditions are summarized. Next, the extreme GIC injection devices and simulated experiment methods are discussed. And the experimental and simulation results acquired by Defense Threat Reduction Agency (DTRA) and Electric Power Research Institute (EPRI) are also discussed, as well as the power system effects simulation and assessment. Finally, the article summarises the present work, and analyzes the future research from the perspective of effects mechanism, primary power equipment characteristics, simulated experimental methods, and system-level effects assessment.
Pulse Power Application and Frontier Interdisciplinary Science
Method for predicting plasma channel length for rock breaking by pulsed discharge
Liu Yi, Liao Hongbin, Cheng Jin, Li Liuxia, Lin Fuchang, Zhao Yong
2024, 36: 055021.   doi: 10.11884/HPLPB202436.230432
[Abstract](129) [PDF 3018KB](50)
Abstract:
Aiming at the difficulty of predicting the length of rock-breaking arc plasma channel by high voltage pulse discharge, a comprehensive test platform for rock-breaking arc plasma channel by high voltage pulse discharge was constructed. The development characteristics and typical current and voltage parameters of arc plasma channel under granite-tap water combined medium were measured, and the broken region formed on the rock surface under different electrode spacing and pulse discharge times was extracted. Based on the energy balance equation, the impedance model of the arc plasma channel in rock is established. The approximate optimal solution of the impedance model parameters is obtained by iterative optimization algorithm. The relative error between the calculated results and the experimental results is less than 7%. Based on the optimized parameters, the length of plasma channel is predicted by the measured current and voltage data. The absolute error between the plasma channel length predicted by the model and the measured value is in the order of mm, and the relative error is less than 10%, which provides theoretical support for the matching design of power-electrode load in the high-voltage pulse discharge rock breaking system.
Optimization and evaluation of simulation model for diesel generator set with pulse load
Shi Meng, Yang Yibin, Yang Dingfu, Huang Kefeng, He Kai, Wu Zhen
2024, 36: 055022.   doi: 10.11884/HPLPB202436.230342
[Abstract](63) [PDF 1640KB](22)
Abstract:
Aiming at the output characteristics of diesel generator set with pulse load, an index is proposed to evaluate the consistency of output voltage (current) waveform to judge the simulation degree of the model. Also, a dynamic limiting method for synchronous generator excitation voltage output based on BP neural network algorithm is proposed, and it is applied to the model optimization of diesel generator set. Experimental results show that among the 27 sets of examples, 18 groups’ real-time waveform proximity (RWP) values are less than 90% in the original simulation but in the optimized simulation, the RWP values of all the test groups are higher than 90%, indicating that the optimized simulation model is more effective, and can be applied to further research on diesel generator set with pulse load.
Spatial distribution of active particles in pulsed driven plasma jet
Bao Hanchun, Guan Yinxia, Wang Shiqiang, Tang Shiya, Li Chao, Guo Yafeng
2024, 36: 055023.   doi: 10.11884/HPLPB202436.230422
[Abstract](91) [PDF 4800KB](25)
Abstract:
To investigate the spatial distribution characteristics of active particles in atmospheric pressure pulse driven plasma jet, a coaxial double ring plasma jet reactor was used. Under external pulsed power excitation, the relative intensity changes of characteristic peaks of each active particle in different ionization regions along the axial space were studied. The results show that active particle characteristic peaks such as NO, OH, N2, \begin{document}${\rm{N}}_2^{+}$\end{document}, He, can be detected at all measurement points of the pulse excited plasma jet, with the emission spectral bands and characteristic peaks corresponding to OH, N2, \begin{document}${\rm{N}}_2^{+}$\end{document} particles being more significant; In the upstream ionization section between the high-voltage electrode and the grounding electrode, the relative intensities of characteristic peaks of active particles NO, OH and N2 are higher near the high-voltage electrode and grounding electrode, while lower in the middle of the upstream ionization section. The relative intensities of characteristic peaks of different levels of He and \begin{document}${\rm{N}}_2^{+}$\end{document} gradually decrease along the airflow direction; In the midstream ionization section from the grounding electrode to the reactor nozzle, the axial distribution of relative intensities of active particles NO, OH and characteristic peaks of different energy levels N2, \begin{document}${\rm{N}}_2^{+}$\end{document} and He shows a gradually decreasing trend with the direction of the airflow; In the downstream ionization section from the reactor nozzle to the end of the plasma jet, the axial distribution of the relative intensity of the characteristic peaks of active particles OH and NO gradually weakens with the direction of gas flow; The relative intensity of the characteristic peaks of different energy levels N2, \begin{document}${\rm{N}}_2^{+}$\end{document} and He shows a pattern of first increasing and then decreasing, providing strong support for the in-depth study of the energy transfer process and reaction mechanism of pulse driven plasma jet.