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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:
A review of basic types and technological realizations of charged particle accelerators
Chen Sifu, Huang Ziping, Shi Jinshui
Accepted Manuscript  doi: 10.11884/HPLPB202032.190424
[Abstract](2) [PDF 1910KB](0)
The modern particle accelerators have developed greatly over the last 100 years. This article provides an overview of all main types of particle accelerators. Simple charts are given to exhibit conceptual and technological evolutions of each type particle accelerator. The basic types, fundamental principles, technological realizations, and typical technical features of various types of particle accelerators are also briefly introduced.
Measurement signal processing technology for magnetic axis of solenoid based on pulsed tuat-wire method
Jiang Xiaoguo, Yang Xinglin, Jiang Wei, Liao Shuqing, Zang Zongyang, Liu Yunlong, Long Quanhong, Li Jiayuan
Accepted Manuscript  doi: 10.11884/HPLPB202032.190431
[Abstract](0) [PDF 866KB](0)
In measurement of magnetic axis of solenoid, there are some key difficulties should be solved,such as precision measurement for tuat-wire vibration and position, reducing measurement signal distortion, separative data processing for offset and tilt signal in magnetic axis of solenoid and so on. One kind of signal detect and measurement principle of extracting the useful faintness signal via subtracting the high offset level signal from the total measurement signal is adopted to meet the above need. The method of constant current driving the detector is also adopted in order to obtain more stability and anti-jamming signal. The measurement system has been developed for directly obtaining the pure vibration signal of the tuat-wire. The problems of obtaining completeness exact measurement signal by simply using an AC coupling amplifier or band-pass filter are resolved and the faintness signal can be obtained without aberration. The influence produced by tilt and up-down in low frequency component of base line signal is eliminated ulteriorly. The separative data processing for offset and tilt signal is also achieved to some extent. The measurement sensitivity has been improved maximumly by about an order of magnitude.
Design of S-band bi-phase modulator with high speed and accuracy
Bai Weida, Jiang Tao, Xiong Zhengfeng, Jiang Zili
Accepted Manuscript  doi: 10.11884/HPLPB202032.19394
[Abstract](25) [PDF 889KB](1)
Bi-phase modulator is one important component in SLAC energy doubler (SLED) pulse compression systems. Performance such as precision and speed of phase shift has a significant impact on SLED. In this paper, an S-band bi-phase modulator with fast speed and adjustable accuracy is presented. Precision of the phase shifter is related to two parallel varactors, controlled by bias voltage. The simulated results show that the proposed bi-phase modulator has a fast switching speed of 4 ns and a high phase shift accuracy.
Generation of sub-mm focal spot for intense-current accelerator utilizing spatial collimating restriction
Wang Yi, Li Jin, Li Qin, Dai Zhiyong
Accepted Manuscript  doi: 10.11884/HPLPB202032.190166
[Abstract](92) [PDF 1316KB](2)
Focal spot size is a key parameter for evaluating the resolving power of the accelerator. A reduction in the focal spot size can effectively improve the spatial resolution of the object. This work studies and designs collimator structures for spatial restriction, which help to reduce the geometry blur of imaging and thus obtain a smaller effective spot-size. The Monte Carlo method is applied to simulate the generation of the light source and the imaging process of the spatial resctriction structures. The parameters of the light source with different collimator structures are analyzed, including the distribution and size of the effective focal spot, the angular distribution and the spectrum of the photons. Theoretical calculations show that an effective focal spot size with a sub-mm scale can be obtained by means of spatial restriction at the expense of a partial loss of the field-of view and the exposure.
Research of phased array antenna system suitable for tunnel
Zhong Xuanming, Zhang Dongmin, Liao Cheng, Du Zheng, Xiong Jie
Accepted Manuscript  doi: 10.11884/HPLPB202032.190423
[Abstract](39) [PDF 854KB](1)
In order to meet the urgent need of high-speed and high-quality wireless communication in tunnel environment. The high gain antenna suitable for tunnel environment is studied. A novel approach to improve the transmission quality of signals in tunnel by using two-element phased array antenna system is presented. The phased array antenna system consists of two high gain antennas and a phase shifter. By adjusting the phase of one antenna, the minimum amplitude of the superimposed electric field strength in the tunnel can be maximized, and the average electric field strength of the signals can be increased. The simulation results show that, compared with the signals transmitted by the single antenna, the minimum amplitude of the superimposed electric field strength of the resultant signals transmitted by phased array antenna system increases by 19.6 dB at least in the axial propagation range of 3000 m tunnel, and at least a 12.4 dB augmentation of the minimum electric field strength compared with the signals transmitted by the two antennas simultaneously, which achieves better diversity optimization effect, eliminates the deep fading caused by multipath effect, and solves the communication problem in tunnel environment.
Numerical simulation and experimental verification on distribution characteristics of hydrogen flow in single compartment
Qi Xiongfei, Hou Liqiang, Du Zhengyu, Cao Xuewu
Accepted Manuscript  doi: 10.11884/HPLPB202032.190420
[Abstract](52) [PDF 865KB](0)
The distribution characteristics of hydrogen flow in local single space is a special concern of nuclear power plant and hydrogen storage device. In this paper, a single compartment of the experimental device which used as a geometric structure to establish a computational fluid dynamics analysis model for the numerical study of hydroFgen distribution in small-scale space. By comparing the experimental data with the simulated data, the choice of the optimal turbulence model is given, and the flow distribution of hydrogen in small-scale space under low mass flow rate condition is simulated. The numerical simulation show that the results obtained by Realizable k-ε, RNG k-ε and Standard k-ε turbulence models agree well with the experimental data in the six two-equation turbulence models, which can accurately reflect the release process and distribution of hydrogen in small-scale space. In low mass flow rate case, the radial range of the mainstream region of hydrogen is small, and hydrogen is stably and evenly distributed in the middle and upper part of the compartment.
Ceramic packaged multi-gap gas switch for fast linear transformer driver
Jiang Xiaofeng, Cong Peitian, Zhou Wenyuan, Wang Zhiguo, Jiang Hongyu, Sun Tieping
Accepted Manuscript  doi: 10.11884/HPLPB202032.190383
[Abstract](43) [PDF 895KB](4)
To improve the housing lifetime, insulation reliability and assembly consistency, the process and breakdown characteristics of a ceramic packaged multi-gap gas switch used for fast linear transformer driver (FLTD) were studied based on the multi-gap gas switch with stackable insulators and electrodes. The effects of different sealing processes on the electric field distribution of the interface between ceramic and metal were compared and analyzed, and then the reasonable sealing structure was optimized. A ceramic packaged multi-gap gas switch was designed and its self-breakdown and triggering characteristics were experimentally tested. The results show that when the switch operates at the charging voltage of ±100 kV, the gas pressure of 3atm and the peak current of 30 kA, the average delay time of 5000 shots is 36.4 ns and the jitter is 2.8 ns. The ceramic package gas switch has the advantages on productization and maintenance-free, and will have broad application prospects in FLTD module.
Design of a high-precision and widely tunable bounded-wave electromagnetic pulse simulator
Zhou Kaiming, Li Zhengdi, Deng Jianhong
Accepted Manuscript  doi: 10.11884/HPLPB202032.190373
[Abstract](38) [PDF 723KB](0)
A high-precision and continuously tunable medium bounded-wave electromagnetic pulse simulator is introduced in this paper. A widely tunable, automated novel high voltage pulse source of compact size with fast rise time is adopted. Based on fiber transmission automation control is realized, anti-jamming problem solved and HEMP simulation ability promoted. Parameters of the simulator are below: the rise time about 2.5 ns, half-peak width about 23 ns, working volume 4 m×4 m×5.8 m, output continuously tunable electric field from 0.2 kV/m to 60 kV/m.
PCIe electromagnetic interference analysis and optimization design based on co-simulation of field and circuit
Yang Hui, Song Hang, Xiao Xia
Accepted Manuscript  doi: 10.11884/HPLPB202032.190360
[Abstract](38) [PDF 873KB](0)
In this paper, the rationality of Electromagnetic Compatibility(EMC)design of Printed Circuit Board (PCB) is evaluated in advance through electromagnetic simulation. The purpose of this method is to reduce the situation that the Electromagnetic Interference (EMI) of PCB does not meet GMW 3097 standard when the EMC test is conducted. Firstly, the 3D electromagnetic field simulation of the Peripheral Component Interconnect express (PCIe) module on the PCB is performed. Then the field simulation is dynamically linked with the circuit simulation of the Simulation Program with Integrated Circuit Emphasis (SPICE) model of chip on the PCIe module, so that the co-simulation of field and circuit is performed. According to experimental test, the accuracy of this simulation method is within 6 dBμV, which satisfies the deviation of PCB processing technology and the uncertainty of the experimental test. Thus, this simulation method meets the accuracy requirements. Therefore, the EMI of PCB can be evaluated and the PCB design can be optimized by this simulation method. After the 33 Ω resistors on the PCIe module replaced by magnetic beads, the EMI of the PCB at 1.6 GHz is reduced by 13.4 dB. According to the 1-m method specified in the CISPR 25 standard for testing, the EMI of PCB becomes -3.4 dBμV, which is lower than the GMW 3097 standard requirement. Therefore, the effectiveness of this measure is verified.
Design and implementation of semiconductor multi-physical parallel computing program JEMS-CDS-Device
Li Guangrong, Zhao Zhenguo, Wang Weijie, You Chunguang, Zhou Haijing
Accepted Manuscript  doi: 10.11884/HPLPB202032.190246
[Abstract](30) [PDF 1305KB](0)
Aiming at the research requirements of multi-physical effects mechanism of devices in complex electromagnetic environment, a parallel computing program for semiconductor multi-physics effects, JEMS-CDS-Device, is developed. This paper introduces the architecture design and implementation technology of JEMS-CDS-Device. The program is based on the unstructured grid parallel framework—JAUMIN. It uses the finite volume method (FVM) to discretize and uses the Newton method to get fully coupled solution of the "electric-drift diffusion transport" problem. The program which adopts the "kernel + algorithm library" form architecture, supports 2D/3D unstructured mesh, and can solve problems of tens of millions of degrees of freedom parallelly. It supports extended development of physical effect equations, discrete algorithms, material physics models, etc.
Summary of application of stretched wire technology in accelerator alignment and survey
Yuan Jiandong
Accepted Manuscript  doi: 10.11884/HPLPB202032.190259
[Abstract](99) [PDF 1038KB](1)
To study the application and development of stretched wire technology in accelerator alignment and survey, the principle of stretched wire technology is summarized firstly, then the development history of stretched wire alignment method in accelerator is reviewed, and then the latest development trend of stretched wire alignment method is introduced. Finally, the advantages and disadvantages of various alignment methods and their suitable environments are discussed, and the development differences between domestic and foreign alignment methods are compared. The development direction of the stretched wire alignment method is pointed out, and the direction of the accelerator alignment and survey is given.
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:
Regularity analysis of leakage-field from vertically polarized bounded wave electromagnetic pulse simulator with distributed load
Xie Linshen, Wu Wei, Zhu Xiangqin
Corrected proofs  doi: 10.11884/HPLPB202032.190434
[Abstract](41) [PDF 1179KB](0)
A parallel finite difference time domain (FDTD) method combined with perfectly magnetic conductor (PMC) image method and CST software is firstly presented for computing the leakage field ( including sideward and backward leakage field) from vertically polarized bounded wave electromagnetic pulse (EMP) simulator with distributed load. The results got from simulation agree well with those from experiment. Numerical results show that the leakage field’s peak-value near the ground reaches maximum in the direction of height, but there’s little difference of leakage fields’ peak-values at the testing points under 1.5 m height and far away from the simulator; The peak-values of sideward leakage field from simulator’s transitional section are larger than those from distributed load section, both of them are larger than the backward leakage field from the end of distributed load section, as the testing point is near the simulator, and the backward leakage field may be larger than those sideward leakage fields, as the vertically distance between the testing point and the simulator increases; The regularity conclusion suits for the simulator with different double exponential source. The more excited source component in high frequency domain, the larger backward leakage field in some distance domain. The leakage field from the simulator increases, as ground’s conductivity increases.
Development of ion source discharge chamber for the 5 MW neutral beam heating line on HL-2M device
Wei Huiling, Cao Jianyong, Yu Peixuan, Zou Guiqing, Zhou Hongxia, Yang Xianfu, Zhou Bowen, Luo Huaiyu, Geng Shaofei
Corrected proofs  doi: 10.11884/HPLPB202032.190275
[Abstract](38) [PDF 1136KB](0)
To construct a 5 MW neutral beam heating beamline for HL-2M device, the development of the discharge chamber of the hot cathode arc discharge ion source for neutral beam heating was carried out. The neutral beamline contains four sets of 80 kV/45 A/5 s ion sources, and the discharge chamber design index is 850 A/5 s. Firstly, the electromagnetic studio in CST software was used to simulate the cusp magnetic field of the discharge chamber with specific geometric structure, and the cusp magnetic field distribution was obtained, which verified the rationality of cusp magnetic field layout. To solve the problems in the process of the discharge chamber and the localized arcing in the experiment, the structure of the discharge chamber was improved. The side wall of the discharge chamber changed from 40 rows of cusp magnets to 7 rings of cusp magnets, the cathode structure changed from the filament plate structure to the ceramic kovar structure, and a ceramic shield was added between the discharge chamber and the accelerator. Normal arc discharge was obtained in both the cathode plate discharge chamber and the cathode ceramic kovar discharge chamber. The final shaped discharge chamber adopted 7-ring cusp magnets and ceramic kovar cathode structure. The arc discharge index of the 5 MW neutral beamline ion source was achieved in the final shaped discharge chamber. The arc discharge time was close to 5 s, and the maximum arc discharge current reached 1 000 A.
Effects of different sequential neutron/gamma irradiation on current gain of bipolar devices
Wang Kai, Lü Xueyang, Wu Kunlin, Feng Jiaming, Fan Xiaoqiang, Li Junjie, Yang Guixia, Lu Yi, Qiu Dong, Zou Dehui
Corrected proofs  doi: 10.11884/HPLPB202032.190333
[Abstract](34) [PDF 866KB](0)
In this paper, CFBR-II fast neutron reactor (China's second fast neutron pulse reactor) and Co-60 device are used to carry out experiments on different sequential neutrons/gamma irradiated bipolar transistors. Under the condition that the collector-emitter voltage is constant, the variation curve of the bipolar transistor current gain with the collector current is measured, and the influence of different irradiation order of neutron/ gamma on the current gain of the bipolar transistor is studied. The experimental results show that when the collector-emitter voltage is constant and the collector current is extremely low, the current gain degradation of the bipolar transistor is relatively large, and the current gain increases with the collector current. The degradation of the current gain of the bipolar transistor caused by the gamma irradiation after the neutron pre-irradiation would be greater than that of the neutron irradiation after the gamma pre-irradiation, and the difference is more obvious in PNP transistor than in NPN transistor. This paper presents a preliminary discussion on the related mechanism.
Electron beam introduction of Ka-band coaxial multi-beam relativistic klystron amplifier
Dang Zhiwei, Li Shifeng, Wang Zhanliang, Huang Hua, Wang Tengfang, Liu Zhenbang, Gong Yubin
Corrected proofs  doi: 10.11884/HPLPB202032.190192
[Abstract](195) [PDF 1005KB](2)
The Ka-band high power microwave coaxial multi-beam relativistic klystron amplifier (RKA) is a potential device. This paper firstly determines the main factors affecting its the efficiency of multi-injection electron beam introduction and preliminary structural parameters through theoretical analysis. Secondly, the Ka-band relativistic multi-beam diode model is established by three-dimensional particle simulation software to optimize the structural parameters. The final efficiency of electron beam introduction can reach 89%. An experimental study on the generation and transmission of electron beams was carried out to verify the results of particle simulation. Under the condition of electron beam voltage 502 kV, beam current 4.34 kA, axial magnetic induction strength 0.76 T, the electron beam introduction efficiency reached 72%. The electron beam pattern obtained by electron beam bombardment of the nylon target indicates that the shape of the electron beam is not distorted during generation and transmission. The generated electron beam diameter is about 2 mm. The simulation and experimental results show that the designed high-current multi-beam diode can generate high-quality electron beams and achieve efficient electron beam introduction, providing technical support for Ka-band coaxial multi-reported relativistic klystron amplifiers.
Linewidth of femtosecond laser two-photon polymerization multiple-rapid-scanning
Tong Weiyang, Wang Zhengling
Corrected proofs  doi: 10.11884/HPLPB202032.190089
[Abstract](36) [PDF 897KB](5)
Using the theory of free radical concentration fluctuation combined with the effect of optical tweezers, this paper studies the linewidth of femtosecond laser two-photon polymerization multiple-fast-scanning processing theoretically. According to the relationship between the change of free radical concentration and time in the two-photon photopolymerization processing, considering the influence of the optical tweezers on the free radical distribution range, it obtains the formula of the linewidth of multiple-rapid-scanning processing. It also presents the relationship between linewidth and scanning speed, laser power, and interval time. The results can be regressed to the general formula of single-scanning and are in good agreement with the experimental results in the literature. The study provides a new idea for studying the femtosecond laser two-photon processing to obtain a smaller processing linewidth, and provides a theoretical basis for the femtosecond laser multiple-rapid-scanning processing.
High-frequency characteristics of half rectangular ring helix slow wave structure
Xia Wei, Wei Wanghe, Wei Yanyu, Lu Min
Corrected proofs  doi: 10.11884/HPLPB202032.190359
[Abstract](27) [PDF 1117KB](1)
A novel half rectangular-ring helix slow-wave structure (SWS) is proposed for the design of wide bandwidth and high power traveling-wave tubes. The numerical calculation by 3D electromagnetic simulation software HFSS shows that proper dispersion and coupling impedance can be obtained by reasonably setting the geometrical parameters of the SWS. Meanwhile, compared with the half circular ring helix slow wave structure, slight variation in dispersion and remarkable improvement in coupling impedance have been observed in the numerical calculation of the half rectangular ring helix SWS. The half rectangular-ring helix slow-wave structure has the combined advantages of flatten dispersion, high interaction impedance, easy fabrication and convenience for interaction with sheet beam.
Operation stability improvement for synchrotron light sources by tune feedback system
Wu Xu, Tian Shunqiang, Zhang Qinglei, Zhang Wenzhi
Corrected proofs  doi: 10.11884/HPLPB202032.190270
[Abstract](307) [FullText HTML](134) [PDF 851KB](2)
Ten Insert Devices (IDs) had been installed in the Shanghai Synchrotron Radiation Facility (SSRF) storage ring. The ID gaps were repeatedly adjusted for the scientific experiments during the user time. The residual quadrupole errors beyond the ID feedforward disturbed the beam optics, including the betatron tune deviations that spoiled machine performance and brightness stability. A tune feedback system was developed and implemented in the SSRF storage ring to resolve the deterioration. The tune stability of ±0.001 in 2 weeks was reached. Another important function of this feedback system is finding out slow drift in the power supplies of dipole or quadrupole by observing the correction current changes in the feedback. To prove this feedback’s feasibility, we compared variations of the beam parameters, including the injection efficiency, the beam life-time, the horizontal beam size and the beta-beatings.
A passive efficiency calibration method with Monte Carlo simulation in segmented gamma scanning
Zheng Honglong, Tuo Xianguo, Gou Jiayuan, Wu Yao, Zuo Wei, Guo Yufei, He Lin, Liu Yanfang, Huang Cong, Yang Linfeng, Liu Wei
Corrected proofs  doi: 10.11884/HPLPB202032.190416
[Abstract](38) [PDF 885KB](0)
In this work, an efficiency calibration function model is presented to calculate the efficiency of segment in segmented gamma scanning (SGS) for 200 L nuclear waste drum. Discrete SGS efficiencies are simulated with MCNP for different densities and gamma ray energies. Parameters of function are determined by using multivariate nonlinear regression method with the efficiencies. The SGS efficiency calibration function is constructed to calculate the efficiency matrix. Aluminum silicate with density of 0.310 g·cm−3, wood fiber of 0.595 g·cm−3, point sources 137Cs with activity of 3.110×105 Bq and 60Co of 1.371×105 Bq are used to construct samples of drum for SGS analysis. Result shows: for the extremely heterogeneous radioisotope distribution of only a point source placed at 8 different positions in the drum, errors of reconstructed activities are −37.68%~31.52%. Overall, the reconstructed activity is in agreement with the true activity. This method effectively and accurately achieves SGS efficiency calculation and reconstruction of activity.
Research on lidar scanning mode
Yuan Guangfu, Ma Xiaoyu, Liu Shuang, Yang Qilong
Corrected proofs  doi: 10.11884/HPLPB202032.190382
[Abstract](246) [PDF 817KB](6)
Scanning lidar is widely used in atmospheric remote sensing detection and target capture. To realize the effective detection of lidar, this paper studies four common scanning modes of l​​​​​​​idar: raster scanning, Lissajo scanning, spiral scanning and hexagonal scanning. The corresponding scanning equation is deduced, and the physical meaning and adjustment method of parameters are discussed. Aiming at the requirement of fine scanning in atmospheric remote sensing detection, the distribution of spot under raster scanning and hexagonal scanning is studied. The leakage rate and overlap rate of these two scanning modes are simulated and analyzed. The results show that under the same scanning condition, the leakage area of hexagonal scanning mode is the smallest. The physical image and scan pattern of scanning control system based on the above research are presented. Finally, the characteristics of these four scanning modes are summarized, and their application and suggestions are given.
Characteristics analysis of electrohydraulic shockwave
Wu Min’gan, Liu Yi, Lin Fuchang, Liu Siwei, Sun Jianjun
Corrected proofs  doi: 10.11884/HPLPB202032.190356
[Abstract](211) [PDF 1264KB](3)
Characteristics of electrohydraulic shockwave are the keys to the application of electrohydraulic disintegration of rocks (EHDR). Mathematical models are used to characterize the generation and propagation of the shockwave, an integrated experimental platform is established, the measured and simulated results of typical shockwave characteristics are analyzed. The simulated results of characteristics of shockwaves under different charge voltage are given, and the influence of charge voltage on the shockwave characteristics are analyzed. The results show that the peak pressure and energy of shockwave is 2.67 MPa and 27.30 J respectively, the wave front time is 2.16 μs, the loading rate is 1.24 MPa/μs, when the charge voltage is 11 kV. The peak value and energy of shockwaves increase, the wave front time decreases, the loading rate of shockwaves increases, while the efficiency of electrical energy transfer into shockwave energy decreases, when the charge voltage of capacitor rises. Characteristics of shockwaves can be predicted from the parameters of discharge circuit via simulation, thus to provide theoretical basis for further study on the morphology and effect of EHDR.
Comparison of insulation properties of several liquid dielectrics under nanosecond pulses
Jia Wei, Chen Zhiqiang, Guo Fan, Li Yaoyao, Qi Yuhang, Chen Yongping, Yang Tian
Corrected proofs  doi: 10.11884/HPLPB202032.190338
[Abstract](1040) [PDF 761KB](3)
Based on the self-developed nanosecond pulsed test platform with output voltage of 30 ns risetime and 100 ns half width, and the standard dielectric strength DC tester, the breakdown characteristics of four liquid dielectrics (transformer oil, glycerol, deionized water and Galden HT200) under DC and nanosecond pulses were experimentally studied and compared. The following conclusions were obtained: (1)Under both DC and nanosecond pulse, Galden HT200 has the highest breakdown field strength which is more than 40% higher than that of the transformer oil. (2) Under the nanosecond pulse, the breakdown field strength of Galden HT200 and transformer oil both increased by 6.5-7 times than those under DC. And it took the shortest time(nanosecond scale) for Galden HT200 to breakdown, followed by the transformer oil(20 ns), then glycerol(45 ns) and deionized water(70 ns). (3) After multiple breakdowns, a lot of carbonized discharge products were accumulated at the electrode gap in the glycerol which has the largest viscosity coefficient. However, there are no obvious breakdown traces in the Galden HT200 and deionized water, which both have the smaller viscosity coefficient. But obvious shock waves were observed in the Galden HT200 and deionized water, which make the gap electrodes loose.
Digital self-excited vertical test system of superconducting cavity
Yang Jisen, Pan Weimin, Wang Honglei, Liu Jiaji, Wang Muyuan, Zhou Quan, He Feisi, Sha Peng, Lin Haiying, Wang Qunyao, Wang Guangwei, Mi Zhenghui
Corrected proofs  doi: 10.11884/HPLPB202032.190320
[Abstract](52) [PDF 847KB](3)
Vertical test is an important method for characterizing the performance of superconducting cavities. We designed an superconducting cavity vertical test system based on digital self-excited algorithm and the technology of low-level radio frequency, which could improve the vertical test efficiency of superconducting cavities. The RF front-end and clock distribution system of the vertical test system adopts the second up-and-down conversion scheme. To some extent, the working frequency of the digital self-excited loop of the vertical test system can be set flexibly, and the working bandwidth of the test system is increased. The test results of the pass-band frequency of the 1.3 GHz 9-cell superconducting cavity show that the vertical test system has strong frequency resolution (<800 kHz) to ensure the smooth progress of the multi-cell superconducting cavity pass-band test.
Nitrogen doping experiment of 1.3 GHz superconducting cavity
Dong Chao, Sha Peng, Liu Baiqi, Li Zhongquan, Yang Jisen, Wang Honglei
Corrected proofs  doi: 10.11884/HPLPB202032.190141
[Abstract](303) [PDF 712KB](13)
In order to greatly improve the quality factor (Q) of a Nb superconducting cavity and reduce its power loss, we performed high-temperature nitrogen doping (N-doping) on the superconducting cavity, which is the most widely used method in the world. Based on the needs of large-scale accelerators at home and abroad, the Institute of High Energy Physics, Chinese Academy of Sciences, carried out researches on 1.3 GHz 1-cell superconducting cavities, including standard post-processing and N-doping. After data analysis and comparison, it can be found that the Q values of two 1.3 GHz 1-cell fine-grain superconducting cavities have been significantly improved. At the same time, the abnormal behavior of Q value depending on acceleration gradient (Eacc) was observed in low-temperature vertical test, which is called the "anti-Q-slope" phenomenon.
Influence of armature-rail contact surface morphology on starting characteristics of armature
Che Yingdong, Zhao Weikang, Wang Zhizeng, Tian Wen, Kong Youjun, Yuan Weiqun, Yan Ping
Corrected proofs  doi: 10.11884/HPLPB202032.190370
[Abstract](152) [PDF 1007KB](7)
The armature-rail contact interface affects the characteristics of armature startup in the pulsed high current linear driver. Furthermore, the armature startup has an influence on the system efficiency and lifetime. This paper discusses the effect of armature surface morphology on armature startup. In the experiments, a high-speed camera was set up to observe the armature startup. Combined with the finite element software ANSYS, the pre-tightening force and contact status were simulated. Besides, the electromagnetic pressure and current density were also obtained by simulation. The results show that groove increased the flexibility of armature and the homogeneity of current distribution was improved by the current skin effect. Owing to the increasing pressure, the groove armature startup was delayed and its contact resistance reduced. The results have important significance to improve contact condition and reduce erosion.
Magnetized liner inertial fusion research progress
Zhao Hailong, Xiao Bo, Wang Ganghua, Wang Qiang
Corrected proofs  doi: 10.11884/HPLPB202032.190357
[Abstract](24) [PDF 1331KB](0)
Magnetized liner inertial fusion(MagLIF) is a new concept of controlled fusion, which combines both advantages of traditional magnetic confinement fusion (MCF) and inertial confinement fusion (ICF). It has promising application potentials because theoretically it can dramatically lower the difficulties to realize controlled fusion. For purpose of better understandings of MagLIF, we investigate and summarize the main progresses which have been achieved in this field. This context would help researchers to be acquainted with MagLIF research in following domains: theoretical and analytic research, numerical simulations, experimental configurations, measurements and diagnostics, load designs and fabrications, laser driving MagLIF and auto-magnetization target, finally this context would also provide heuristic perspectives for the future MagLIF research.
Display Method:
2020, 32: 025001.   doi: 10.11884/HPLPB202032.200016
[Abstract](34) [PDF 198KB](5)
Pulsed Power Technology
Development of high performance, high-current pulsed electron beam sources
Xun Tao, Yang Hanwu, Zhang Jun, Liu Lie, Zhang Jiande
2020, 32: 025003.   doi: 10.11884/HPLPB202032.190375
[Abstract](211) [PDF 1694KB](24)
As a core part, the performance of a high-current electron beam source is inevitably essential for high-power sources and accelerators. The attractive features are high-electric field vacuum interface, high quality high current density electron emission, and high peak thermal load collector, which are compatible with high repetition rate operations. This paper presents an optimized ceramic insulation structure with hold-off voltage pulse of 600 kV, 100 ns, and 5 Hz. Mechanisms and surface improvements are developed. Large-scale, well-aligned SiC nano-wires as high-current, pulsed electron beam emitters are explored. They show an superior advantage on cathode lifetime and emission quality. In addition the thermal control and cooling methods for a repetitively operated high current collector are gathered, and the specially designed device can work stably with a heat flux of 1012 W/m2. These efforts make solid contributions to the HPM sources for practical use.
Simulation method of quadruple-level circuit model for stack and vacuum section of Julong-I facility
Mao Chongyang, Xue Chuang, Xiao Delong, Ding Ning
2020, 32: 025004.   doi: 10.11884/HPLPB202032.190330
[Abstract](300) [PDF 593KB](5)
The quadruple-level circuit model for stack and vacuum section of Julong-I facility was established. To avoid complicated two-dimensional circuit simulation, the prediction-correction method was used to deal with the distribution of currents at the entrance of the quadruple-level insulation stack. The accuracy and efficiency were both ensured by this method. By applying this model to the FCM-PTS code coupled with the snow-plow model for the Z-pinch load, the current for each level of the outer magnetic insulation transmission line was obtained, while the coincidence of load currents between simulation and experiment was also improved.
Experimental study on multi-channel synchronous conduction conditions of GaAs-PCSS
Liu Yi, Shen Yi, Xia Liansheng, Wang Wei, Ye Mao, Zhang Huang
2020, 32: 025005.   doi: 10.11884/HPLPB202032.190328
[Abstract](204) [PDF 960KB](5)
Gallium Arsenide Photoconductive Semiconductor Switch (GaAs-PCSS) has outstanding features, such as, fast response, high repetition, low jitter and high-power capacity. Multi-channel design can effectively reduce the damage from high current in nonlinear mode and improve switch’s lifetime. In this paper, on the solid-state pulse forming line experimental platform, multiple GaAs-PCSSs are connected in parallel as one switch through a special fixture, and different trigger signals are applied to each of them, in order to study the necessary conditions for GaAs-PCSS multi-channel synchronous conduction. The results show that, firstly, by the same trigger signals, the on-current is successfully divided into 4 GaAs-PCSS channels; secondly, by different trigger signals, the delay time difference and trigger energy difference must be lower than 1 ns and 20 μJ respectively, if an effective current diversion is expected; thirdly, split and integrated multi-channel GaAs-PCSS structures are designed, and the integrated 20-channel GaAs-PCSS was slightly damaged after 7000 shots.
Current and electromagnetic radiation characteristics of three-electrode gas spark switch
Qiu Yongfeng, Bian Li’an, Liu Zhu, Xiao Pei, Jiang Jianhui, Li Gaosheng, Yang Jianhua, Liu Jinliang
2020, 32: 025006.   doi: 10.11884/HPLPB202032.190326
[Abstract](283) [PDF 700KB](10)
Strong electromagnetic radiation is produced when the three-electrode gas spark switch works. In this paper, firstly, theoretical analysis of the on-current and electromagnetic radiation of the switch is carried out, then the switch is simulated by CST software and the breakdown field strength of which is calculated. Secondly, the on-current and far-field radiation field strength of the three-electrode gas spark switch are measured experimentally, and the results are summarized and analyzed. Finally, the strong electromagnetic radiation of the switch is suppressed with electromagnetic shielding method effectively. The research results can provide reference for electromagnetic radiation and protection of pulse power devices.
Efficiency of distributed energy storage electromagnetic railgun
Wen Yanling, Dai Ling, Zhu Qi, Wang Shaojie, Lin Fuchang
2020, 32: 025007.   doi: 10.11884/HPLPB202032.190332
[Abstract](286) [PDF 1113KB](6)
A distributed energy storage (DES) electromagnetic railgun has the advantage of higher efficiency, compared with a breech-fed railgun. A railgun with a caliber of 60 mm×80 mm is designed. In order to stabilize the current waveform, current feed-in points are set along the length of the gun, and the armature position is diagnosed and the pulse power system is triggered by real-time feedback signal to test the performance of the DES railgun. The resistance gradient is calculated by finite element analysis: the coupling field of current field and magnetic field is applied to the rectangular rail-armature model established in the 3D magnetic field of COMSOL. Based on the platform of MATLAB SIMULINK, the power circuit of capacitive energy storage pulse power supply module is established. The impedance models of rail and armature are established according to the non-linear time-varying dynamic characteristics of DES electromagnetic railgun, and the forward electromagnetic force and sliding friction force are calculated to construct the motion equation of armature. The armature-railgun module is built by signal circuit, and the two isolated networks connected through SIMULINK measurement module. The variable step-size ode23tb solver calculate the railgun current and exit velocity. A 4.16 MJ DES electromagnetic railgun is designed. The results show that with 10.8 kV pre-charging voltage of the capacitance, a 3 m long DES electromagnetic railgun can accelerate the 1 kg projectile to 1.4 km/s. Compared with the breech-fed electromagnetic railgun, the launching efficiency of the system can be increased by about 3%.
Thermal analysis calculation of dry-type transformer in PSM high voltage power supply
Xia Yuyang, Li Qing, Mao Xiaohui
2020, 32: 025008.   doi: 10.11884/HPLPB202032.190294
[Abstract](320) [PDF 834KB](4)
Multi-winding dry rectifier transformer is an important equipment for high voltage power supply in Tokamak heating system. Its excellent performance is directly related to the output quality of high voltage power supply. Carrying out research on power loss and heat dissipation of transformers, reducing the performance impact of transformers due to temperature rise, is very important to ensure the good working condition of the transformer. In this paper, the relationship between thermophysical properties and temperature is fitted by MATLAB. The convective heat transfer and thermal radiation of the transformer are analyzed and calculated by the equations. In the case of natural convection and heat radiation of the air, the temperature of the transformer cannot be controlled within a temperature range that satisfies the performance, and the temperature rise is about 200 ℃. In the case of forced air convection, the good heat dissipation of the transformer is realized, and finally the forced air cooling at a wind speed of 2 m/s is achieved, and the temperature rise of the transformer is less than 75 ℃, ensuring the good working condition of the transformer. The article further uses ANSYS to analyze the temperature field distribution of the transformer. Forced air cooling reduces the overall temperature and allows heat to be released to the surrounding atmosphere more quickly, reducing the damage of the transformer under high temperature.
Preliminary study on all-solid state long pulse generator based on fractional-turn ratio saturable pulse transformer
Chen Rong, Yang Jianhua, Cheng Xinbing, Qian Baoliang
2020, 32: 025009.   doi: 10.11884/HPLPB202032.190327
[Abstract](361) [PDF 1304KB](12)
This paper presents the design of an all-solid state pulse generator based on a fractional-turn ratio saturable pulse transformer which, as the key component, takes the roles of magnetic switch, pulse forming device, voltage boosting device, etc. Preliminary experimental results show that a quasi-square pulse with the amplitude of 14.4 kV and the pulse width of 194 ns are obtained while the DC voltage source supply is 100 V. Hence, it is feasible to apply this technology to construct a generator outputting pulses with the pulse width of several hundred nanoseconds. This study can provide a guidance to construct a MW level solid state pulse generator module.
Degradation of organic dyes by nanosecond pulsed discharge plasma
Qiu Congying, Guan Xiantao, Liu Zhen, Zhu Anna, Yan Keping
2020, 32: 025010.   doi: 10.11884/HPLPB202032.190390
[Abstract](415) [PDF 1006KB](12)
Organic compounds (especially dyes compounds) are major pollutants in the industrial wastewater and have gained a great concern due to their hazardous influence on the environment and mankind’s health. A multiple pin-plane type pulsed corona discharge reactor was used to degrade Brilliant Crocein(Acid Red 73, AR73) continuously. The reactor was energized by a repetitive TLT based nanosecond pulsed power source. The source can produce pulses with a peak voltage of 50 kV, a pulse width of 40 ns, and a risetime of 20 ns at a repetition rate of up to 500 Hz. To evaluate the discharge performance, residual dye concentration and hydrogen peroxide (H2O2) were analyzed by UV spectrophotometry. The high voltage of 44.26 kV amplitude and frequency of 200 Hz were applied to the needles while wastewater film was used as the ground electrode. When the initial concentration of AR73 was 30 mg/L and the flow rate was 3.4 L/min, the degradation percentage of AR73 could reach up to 83.20% after 30 minutes of treatment with the needle-water distance of 30 mm. Under this condition, the input energy per pulse was 11.73 mJ, the concentration of H2O2 was up to 47.36 μmol/L, and the energy yield for 50% dye removal was 31.07 g·kW−1·h−1. Increasing the discharge voltage could further increase the degradation rate of AR73, and the active species generation in the solution was enhanced, but the energy efficiency decreased.
Two-phase streamer characteristics in transformer oil under nanosecond impulses voltages
Wang Qi, Wang Meng, Wang Jue, Yan Ping
2020, 32: 025011.   doi: 10.11884/HPLPB202032.190380
[Abstract](384) [PDF 2129KB](3)
To reveal the influence of the formation and development of gas-phase streamer channel on liquid discharge between pin-plane electrodes, a numerical model of the transformer-oil discharge in the pin-plane electrode system is built based on the continuity equations of free charge carriers, which are coupled with the Poisson’s equation. The gas-phase processes during the streamer development process is also taken into consideration, including impact ionization and the increase in the mobility of free charge carriers in the gas-phase relative to the liquid-phase in the streamer channel. The Heaviside function is used to switch the simulation model between gas-phase and liquid-phase. The initial and propagation progress of streamer discharge under nano-second pulse voltage is simulated using the model. Simulating results show that the electric field at the streamer body is significantly reduced and the electric field at the head of the streamer is further enhanced with the addition of such low density gas-phase region. The propagation speed of the streamer in two-phase model is also faster than that of the ordinary liquid-phase model.
Effect of gas medium on corona discharge for voltage balance and self-breakdown characteristics in multi-gaps gas switch
Liu Xianfei, Tang Zhao, Liu Xuandong
2020, 32: 025012.   doi: 10.11884/HPLPB202032.0358
[Abstract](99) [PDF 889KB](10)
The fast linear transformer drive (FLTD) is a new type of pulse power source developing rapidly in recent years. It usually adopts multi-gap gas switch (MGS) as its primary switch. The corona discharge for voltage balance was proposed to improve the switch breakdown performance. However, great difference of corona discharge in different gases may exist and affect the performance of MGSs. In this paper, the effects of needle electrode in air on single-gap corona discharge characteristics are studied. The size of corona needle electrode is determined. Then, the corona discharge characteristics in N2, CO2, SF6/N2 and C4F7N/N2 are studied. The breakdown voltage of the 6-gap gas switch and its stability with the gas type and pressure are studied. The experimental results show that the corona current is high in N2. The corona current in air is lower and the corona discharge is stable in air. The addition of electric negative gas will greatly reduce the corona current. When air and N2 are used as the switch gas, the breakdown voltage of the switch increases linearly with the increase of gas pressure, but there is a low breakdown voltage sometimes. When electric negative gas is mixed with N2, the breakdown voltage is significantly higher. When the pressure of 1%SF6/99%N2 mixed gas is 0.18 MPa, the breakdown voltage is about 197.33 kV and the ratio of the standard deviation to the breakdown voltage is 1.50%.When 1% C4F7N/99%N2 mixed gas is 0.15 MPa. The breakdown voltage is about 190.42 kV, and the standard deviation is 0.55%. This indicates that the mixed gas of C4F7N and N2 has a significant effect on improving the breakdown voltage stability of multi-gap gas switch.
Status of radiographic X-ray source driven by 4 MV, 80 kA induction voltage adder
Wei Hao, Yin Jiahui, Zhang Pengfei, Sun Fengju, Qiu Aici, Liang Tianxue, Zeng Jiangtao, Jiang Xiaofeng, Wang Zhiguo, Sun Jiang, Liu Wenyuan, Hu Yixiang
2020, 32: 025013.   doi: 10.11884/HPLPB202032.190331
[Abstract](340) [PDF 1266KB](16)
This paper presents the design details and experiment results of a 4 MV facility developed for flash X-ray radiography in Northwest Institute of Nuclear Technology (NINT). The facility is based on the technology of an induction voltage adder (IVA) driving a rod pinch diode (RPD). The facility mainly consists of the prime power source, induction voltage adder, and RPD. The prime power source consists of two 3.2 MV low-inductance Marx generators and four deionized-water coaxial lines. Each Marx generator charges two 6 Ω, 30 ns pulse forming lines (PFLs) in less than 370 ns. There exist two-stage pulse compressions for each pulseline, providing four forward waves with peak voltages of 1 MV at current of 160 kA with a duration time of 60 ns. Four electrically-triggered SF6 gas switches serve as energy transfer switches from PFLs to outlines, and then four self-breakdown water switch are used to sharpen the risetime and reduce the prepulse. The IVA consists of four-stage induction cavities stacked in series, each of which almost operates at 1.5 MV voltage. A vacuum insulated transmission line (without magnetic insulation) is used for power addition. The RPD is chosen to create X rays through bremsstrahlung. At present, the IVA could produce a 4.3 MV voltage with a risetime (10%-90%) of 21 ns and a FWHM time of 70 ns. The diode current is about 85 kA, and the FWHM time of X rays is about 55 ns. The delay time from Marx trigger to the X-ray output is about 749 ns, with a standard deviation of about 7 ns. With a 2-mm diameter tungsten rod used, the X-ray dose is about 15.5 rad (LiF) at 1 m straight ahead, and the spot size is about 1.4 mm.
Study of ultrafast semiconductor opening switch
Wang Ganping, Li Fei, Jin Xiao, Song Falun, Zhang Qi
2020, 32: 025014.   doi: 10.11884/HPLPB202032.190298
[Abstract](391) [PDF 669KB](11)
In this paper, the working principle of drift step recovery diode (DSRD) is introduced. The relation between the device parameters and switching characteristic is revealed by studying the physics processes inside DSRD. The analyses show that the rising rate of output pulse is proportional to the electric field breakdown threshold and saturated drift velocity of carrier. Large breakdown threshold and low doping level are benefitial to improve the maximum operation voltage, but the switching time will be increased also. In general, high breakdown threshold is necessary for DSRD with excellent performance. In addition, for the expanding of the diffusion zone over time, the pre-pulse can be reduced with short pumping time, which is obvious when forward current time is larger than 200 ns. To obtain an ideal pulse front, the injected charge should be exhausted as soon as the backward current just achieves maximum. By a simple pumping circuit, a fast pulse generator based on DSRD with the rise time of about 4 ns and the amplitude of 8 kV was designed, which can be used to trigger the fast ionization diode.
A parameter optimization method of snubber circuit of thyristor under pulse current working condition
Tong Wei, Li Hua, Fu Peng, Wang Kun, Mahmood Ul Hassan, Song Zhiquan
2020, 32: 025015.   doi: 10.11884/HPLPB202032.190280
[Abstract](211) [PDF 1045KB](5)
As thyristor valve is the core equipment of quench protection system of large fusion device, the design and optimization of its snubber circuit parameters are related to the safety and reliability of the valve and even the whole quench protection system. So far, most of the design and optimization of snubber circuit parameters are based on DC steady-state conditions. However, there are few literatures on parameter optimization under impulse conditions. In this paper, the buffer circuit parameters of thyristor valve are designed and optimized under the pulse condition of superconducting magnet quench protection system. Based on the exponential model of thyristor reverse recovery current, the current mathematical model at the turn-off time is established. The relationship between the key parameters is obtained through experiments, and the reverse recovery model of thyristor current is established in Matlab according to thyristor performance and system requirements. Considering the performance requirements such as current drop rate at turn-off time, peak reverse recovery voltage and the cost, a parameter design and optimization method of thyristor snubber circuit under pulse condition is proposed. The model of quench protection system is built in Matlab, the simulation results show that compared with the original parameters, the optimal parameters reduce 11% of the peak reverse recovery voltage and 43% of the peak reverse recovery voltage change rate. At the same time, the manufacturing cost of the circuit is reduced to 1/7 of the original one.
Thermal characteristics of high voltage and high current thyristor assembly
Zhang Xingru, Feng Bingyang, Liu Jun, Li Yuansheng, Xiao Haolong, Zhang Mengyu, He Mengbing
2020, 32: 025016.   doi: 10.11884/HPLPB202032.190346
[Abstract](80) [PDF 973KB](6)
Thyristors have the advantages of good control characteristics, long life and low noise. At present, in the application of pulse power technology, the use of high-power thyristors instead of traditional gas switches is a research trend. Thyristors are used under high voltage, high current, and repetitive operating conditions, requiring careful selection and combination of switch components. Based on the failure mechanism of thyristors, the theoretical analysis, simulation calculation and experimental research on the heating of thyristor components under high voltage, high current, high di/dt, high du/dt and repetitive frequency are carried out. The use conditions of the thyristor components in repetitive frequency pulse power system thus have a theoretical basis. As the operating voltage, current, and frequency of the thyristor increase, the thermal loss of the thyristor increases and the heating of the thyristor becomes more serious. To ensure the safe and stable operation of the thyristor, the junction temperature needs to be kept within a safe range, and it cannot work at repetitive frequencies for a long time.
Flashover characteristics of laminate structure composed of round parallel-plate electrodes and polymer film dielectrics
Chen Zhiqiang, Jia Wei, Xie Linshen, Guo Fan, Wang Chengcheng, He Xiaoping, Wu Wei, Ji Shengchang
2020, 32: 025017.   doi: 10.11884/HPLPB202032.190311
[Abstract](129) [PDF 1029KB](9)
The peaking capacitor used for pulse compression in electromagnetic pulse (EMP) simulator often uses the laminate structure of electrodes and thin film dielectrics to achieve insulation at high voltage, and the surface flashover is the main insulation failure mode of the peaking capacitor. In this paper, the effect of key structural parameters of the peaking capacitor and the gas pressure on its surface flashover performance were experimentally studied under the condition that the insulation gas was SF6 and the risetime of the applied voltage was approximately 30 ns. The experimental results show that: (1) the electrode thickness, the interspace around the electrodes and the surface coating ceuld not significantly change the surface flashover voltage of the laminated structure; (2) increasing the gas pressure could improve the flashover performance at low gas pressure; (3) the flashover voltage is nearly proportional to the number of polymer film layers; (4) the flashover voltage could be increased remarkably by increasing the extension length of the polymer film dielectrics. Based on the streamer theory, the above results are analyzed and discussed. It is considered that in inhomogeneous field the flashover initiates in the strengthened field region but the formation and development of the flashover channel is mainly determined by the background field on the flashover path. Therefore, reducing the electrical field at the triple point has little effect on the flashover performance but reducing the field on the flashover path can improve the flashover voltage of the laminated structure significantly.
Experimental research on reliability of 1 MV X-ray system for radiography
Ma Chenggang, Li Hongtao, Deng Minghai, Cao Ningxiang, Mo Tengfu, Wang Xiao, Zhang Zhiqiang
2020, 32: 025018.   doi: 10.11884/HPLPB202032.190378
[Abstract](183) [PDF 615KB](7)
Referring to the Scorpio-1 prototype, the 1 MV X-ray system for radiography was redesigned. According to the reliability requirements, it has a reliability design of the system elements, including Marx generator, field distortion switch, pulse forming line, pulse transmission line and rod-pinch diode. Moreover, the experimental tests on the reliability of the system, including time jitter and stability of X-ray, were performed. According to the experimental results, the system operates stable and continuous outputs more than 81 shots. The following technical parameters of the system were achieved: time jitter less than 146 ns, X-ray dose 0.75−1.40 R at 1 m right in front of the system and reliability up to 98%.
Development of transmission target X-ray tube
Zhou Liang, Wang Wenchuan, Zhou Lin, Li Mingjia, Liang Chuan, Zhang Faqiang
2020, 32: 025019.   doi: 10.11884/HPLPB202032.190336
[Abstract](87) [PDF 554KB](8)
The X-ray tube is a key component of an X-ray source. An X-ray tube used for a compact nanosecond pulsed X-ray source is described in this paper. The X-ray tube is a sealed transmission target X-ray diode. Its cathode is acomb structure formed from thin tungsten sheets with thickness of 50 μm, while its target is made of a 100 μm-thick titanium film. The X-ray dose at a distance of 20 cm from the diode is 20 mR per pulse while the diode voltage is 512 kV. In this case, the full width at half maximum of the X-ray pulse is about 5 ns.
Design of drift step recovery diode pulse power generator based on magnetic saturation transformer
Shi Xiaolei, Chen Jinhui, Wang Guanwen, Wang Lei, Zeng Tao, Yang Wei, Wang Xu, Su Wentong, Wu Guanjian
2020, 32: 025020.   doi: 10.11884/HPLPB202032.190387
[Abstract](100) [PDF 697KB](4)
Drift step recovery diode(DSRD) has a great application prospect in pulse power technology for its notably short switching-off time, high repetition rate and large working current. In this paper, a DSRD pump circuit topology based on magnetic saturation transformer is studied. The topology is small, light and reliable. According to the operating requirements of DSRD, a pump circuit was designed. It consists of a power MOSFET primary switch and a magnetic saturation transformer with boost and saturation characteristics. The circuit was simulated by Pspice software, which confirmed the principles of the circuit. Based on the simulation analysis, a prototype was designed and its circuit experiment was implemented. The experiment indicates that when the charging voltage is 800 V, the pulse amplitude on resistor load of 50 Ω is larger than 7 kV, the rise time is less than 4.2 ns (10%-90%) and the FWHM is about 10 ns.
Hardware compensation of B-dot low frequency characteristics in cavity
Wei Bing, Kang Junjun, Wang Jie, Fu Jiabin, Fu Zhen, Feng Shuping
2020, 32: 025021.   doi: 10.11884/HPLPB202032.190309
[Abstract](318) [PDF 717KB](7)
The output signal of B-dot probe in the cavity increases at low frequency. The first-order correction method of “a characteristic flux-penetration time” is analyzed. According to the analysis, the method of compensation with integrator is proposed. Frequency response experiments were carried out for B-dot installed in the electrodes of coaxial and radial lines. The results show that when the RC time constant of the integrator is equal to the characteristic flux-penetration time, the measurements of B-dot coincide with the standard current signal. Therefore, for the B-dot probe in the cavity, this is the principle of selecting the RC constant of the integrator. The compensated test results are obtained directly by hardware, thus it is more convenient to operate than the software correction method.
Influence of metal matrix materials on self-breakdown stability of graphene film cathode
Wang Gang, Liu Sheng, Pan Yafeng, Fan Hongyan
2020, 32: 025022.   doi: 10.11884/HPLPB202032.190297
[Abstract](266) [PDF 964KB](11)
Graphene has attracted great interest for its distinctive band structure and physical properties. Results from previous studies show that a graphene cathode can provide stable field emission and intense emission in vacuum. This paper presents two metal matrix graphene film cathodes prepared by different methods. One is a copper/graphene matrix cathode grown by chemical vapor deposition, the other is a stainless steel/graphene matrix cathode transferred by substrate corrosion. The surface morphology of the graphene films on these two cathodes was examined using a scanning electron microscope (SEM) and Raman spectroscopy. The thickness and uniformity of the graphene film was evaluated. Gas spark switches based on these two cathodes were developed. The impulse-breakdown characteristics of these switches in a quasi-uniform electric field were studied. When the gap length is 5 mm and the gas pressure is 0.6 MPa, the average breakdown voltage (UBD) for copper/graphene matrix cathode is nearly 85.9 kV, and the voltage jitter is 3.2%; the average UBD for stainless steel/graphene matrix cathode is nearly 59.8 kV, and the voltage jitter is 2.4%. According to preliminary analysis, the surface state of the cathode and the quality of the graphene film directly affect the breakdown stability of the gas switch.
Research of electromagnetic launched fire-extinguishing bomb fire-fighting system
Zhang Yadong, Xiong Min, Dong Mingyang, Lin xiong
2020, 32: 025023.   doi: 10.11884/HPLPB202032.190304
[Abstract](273) [PDF 2200KB](7)
This article introduces the severe fire situation in China, and clarifies the limitations of the existing fire-fighting solutions. In view of the limited range and the limitation of the use of pyrotechnics, it is proposed to use the electromagnetic coil launcher to launch the fire-extinguishing bomb to extinguish fire. Based on the current filament circuit model, a 10-stage electromagnetic coil launcher is designed. Pulse capacitor is used as the initial energy source and the coil is discharged sequentially by a crowbar circuit. The 7.2 kg projectile could be accelerated to the maximum speed of 171 m/s and the muzzle speed of 154 m/s. The efficiency will be over 15%. It shows that the electromagnetic coil launcher can meet the launching needs of fire-fighting project's needs. An intelligent unmanned electromagnetic launch fire-fighting system is proposed. The intelligent command and control system dispatches drones to collect fire information, then formulates fire-fighting strategies. The unmanned electromagnetic fire-extinguishing vehicle will be controlled to launch fire-extinguishing bombs to achieve accurate and efficient fire extinguishing. The system will adjust the fire extinguishing plan according to the evaluation results of fire extinguishing efficiency until the task is completed.
Analysis of physical effects of borosilicate glass coverslips irradiated by protons
Li Xin, Zhao Qiang, Hao Jianhong, Dong Zhiwei, Xue Bixi
2020, 32: 025024.   doi: 10.11884/HPLPB202032.190325
[Abstract](118) [PDF 760KB](4)
As an important part of the spacecraft power system, solar cells require high conversion efficiency and reliability and a longer service life. By using an anti-irradiation glass coverslip, the protection of the solar cell against particle radiation can be enhanced, the service life of the solar cell can be prolonged, and the spacecraft can obtain a reliable energy supply. Borosilicate glass is an ideal glass cover material for solar cells. In this paper, Monte Carlo method is combined with SRIM software to study the physical mechanism of damage of proton irradiated borosilicate glass. Combining the theory of particles-matters interaction with the basic formula, based on analyzing the stopping power, ionization energy loss and displacement energy loss of protons in different borosilicate glass, and the generation of vacancies, the physical mechanism of the damage was analyzed. The results show that the proton irradiation damage with energy of 30−120 keV mainly occurs on the surface of borosilicate glass; proton deposition and vacancies distribution follow the Bragg curve; ionization energy loss is the main part of energy loss, which increases with the increase of incident energy, leading to ionization and excitation of electrons; displacement energy loss increases with the decrease of energy in the glass, which leads to the vacancy defects of boron, oxygen and silicon. Ionization effect and defects are important reasons for the formation of color center in borosilicate glass.