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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:
Propagation characteristics of terahertz wave in plasma sheath around vehicle
Geng Xingning, Xu Degang, Li Jining, Chen Kai, Zhong Kai, Yao Jianquan
Accepted Manuscript  doi: 10.11884/HPLPB202032.190291
[Abstract](3) [PDF 0KB](0)
In this paper, the plasma electron density and collision frequency are calculated based on the flow field simulation of RAM C-III vehicle, and an inhomogeneous plasma model is established according to the calculation results. The effects of plasma density, plasma thickness, plasma collision frequency and external magnetic field on the propagation characteristics of terahertz wave in plasma are analyzed by using scattering matrix method. The results show that the propagation loss increases with plasma electron density and plasma thickness, while the transmittance decreases first and then increases with the increasing of collision frequency. When an external magnetic field is applied, the propagation characteristics of the left-hand polarized terahertz wave will be improved, while for the right-hand polarized terahertz wave, the application of magnetic field induces an absorption peak, which shifts to high frequency range with the increasing of magnetic induction intensity. This work may make a contribution to the study of solving the problem of communication blackout.
Random vibration response analysis of Sshenguang laser facility component based on PANDA platform
Wang Keying, Fan Xuanhua, Chen Xueqian, Niu Hongpan
Accepted Manuscript  doi: 10.11884/HPLPB201931.190269
[Abstract](1) [PDF 0KB](0)
Reliability design requirements for large and complex equipment pose new challenges to numerical simulation of structural dynamics. In this paper, based on self-developed PANDA parallel computing platform, the modal superposition method is used to calculate the random vibration response under multi-point foundation excitation. The algorithm design and parallel implementation are carried out, and the corresponding solving module is constructed. Taking the six-degree-of-freedom platform structure in the target positioning prototype of Shenguang facility as a numerical example, the modal and random vibration responses of the structure under ground fluctuating load are analyzed with our self-developed progress modules in PANDA platform. The analysis results are compared with the test results and commercial software analysis results. In terms of mode frequency, mode shape and displacement response, the results are consistent. This verified the correctness of the relevant software and prove the feasibility of PANDA platform in actual engineering structural analysis. The correlative studies have important significance on solving dynamic analysis problems of complex equipments with autonomic software and breaking limitations of commercial finite element software.
Nitrogen doping experiment of 1.3 GHz superconducting cavity
Dong Chao, Sha Peng, Liu Baiqi, Li Zhongquan, Yang jisen, Wang Honglei
Accepted Manuscript  doi: 10.11884/HPLPB201931.190141
[Abstract](2) [PDF 0KB](0)
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 research 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.
Inversion algorithm of vertical visibility based on lidar and its error evaluation
Song Hairun, Wang Xiaolei, Li Hao
Accepted Manuscript  doi: 10.11884/HPLPB201931.190250
[Abstract](3) [PDF 0KB](0)
In order to solve the problem that the non-uniform distribution of extinction coefficients in the vertical direction of the atmosphere makes it difficult to directly measure the vertical visibility by traditional methods, this paper presents a method for calculating the vertical visibility based on lidar detection. Firstly, according to the basic principle of atmospheric radiation transmission and radiation transfer equation, we deduce the calculation formula of vertical visibility, which solves the problem that there is no specific formula for calculating vertical visibility. Secondly, we invert the extinction coefficient distribution in the vertical direction of the atmosphere by using the lidar equation and Klett algorithm. On this basis, we propose an iterative algorithm for vertical visibility. Finally, we use the gray model GM(1,1) and batch statistics algorithm to evaluate the backscattering coefficient obtained by laser radar inversion, and give the error confidence interval (0.760±0.339)×10−4(srad·km)−1. This paper applies the vertical visibility iterative algorithm and evaluates the laser radar inversion data. The results show that the method is a particularly effective method for calculating vertical visibility, which meets the basic requirements of detection, and the error is small and high precision.
Anisotropic stacked epoxy composites with excellent thermal properties
Li Jiapeng, Xia Lansong, Zhang Ping, Liu Dong
Accepted Manuscript  doi: 10.11884/hplpb201931.190342
[Abstract](2) [PDF 0KB](0)
With the rapid development of high-power lasers and electronic technology, higher requirements have been proposed for the structure and material of the heat sink device. Based on the principle of conduction-insulation heat, alternating stack epoxy resin composites with excellent thermal protection were prepared, the hexagonal boron nitride (h-BN: 5%, 15%, 25%) and expanded vermiculite (E-ver: 1%) are used as fillers for heat dissipation layer and thermal insulation layer, respectively. The thermal protection performance experiment was completed. The result shows that the temperature of the top center temperature is 13-16 °C lower than that of the traditional materials, and the thermal delay time is greatly improved. An increase in the h-BN content causes an increase in the thermal protection properties of the composites. The thermal mechanism of the anisotropic stacked composites was explained.
Analysis on nonlinear response of RF filter under ultra wide band pulse environment
Lu Xicheng, Qiu Yang, Wu Jing, Tian Jin, Yang Zhiqiang
Accepted Manuscript  doi: 10.11884/HPLPB202032.190355
[Abstract](2) [PDF 0KB](0)
The experiments reveal, for the out-off-band of the filter, the transfer property of a RF filter under ultra wide band (UWB) pulse is essentially in agreement with that of CW. But, for some frequencies in the in-band of the filter, the transfer function of UWB is larger than 1. Moreover, the oscillating property is found in the time domain response of the filter. Therefore, based on the nonlinear passive intermodulation (PIM) and the Q-value, the response mechanisms of the filter are studied. The PIM of the filter is showed nonlinear effects by the two different field strength, which results in the university of measurement results is limited. Furthermore, the signal through the filter is predicted by making use of the two measured transfer functions. The predicting results show the predicting waveform by the CW measured result is smaller than actual result on the energy and the peak power. As a result, the response mechanisms of the filter on UWB pulse does differ from the that of CW. The measured results of CW also can’t be applied for the UWB effect analysis and evaluation.
Degradation of organic dyes by nanosecond pulsed discharge plasma
Qiu Congying, Guan Xiantao, Liu Zhen, Yan Keping
Accepted Manuscript  doi: 10.11884/HPLPB202032.190390
[Abstract](26) [PDF 0KB](0)
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.
Lifetime characteristic of three-electrode field-distortion gas switch of fast linear transformer driver
Li Ying, Jin Jianwei, Chen Li, Sun Fengju, Li Xingwen, Wang Zhiguo, Jiang Xiaofeng, Wu Jian, Li Penghui
Accepted Manuscript  doi: 10.11884/HPLPB202032.190339
[Abstract](18) [PDF 0KB](0)
Three-electrode field-distortion gas switch is a crucial element of modular fast linear transformer driver (FLTD). Electrode erosion affects the trigger jitter during the lifetime of the switch, which in turn can affect the output characteristics of FLTD. Therefore, studying the impact of electrode erosion on the trigger jitter of the switch is of great significance to optimize the switch structure and predict the switch life. This paper studies the erosion characteristic of intermediate electrode of three-electrode switch, and the electrode materials are stainless steel and brass. The key factors affecting the lifetime of switch are obtained by considering the changing rules of trigger and erosion characteristics, which provides theoretical support for the optimization of the performance of the three-electrode switch. The results show that the erosion area and surface roughness of stainless steel and brass electrodes increase with discharge times. The brass electrode is ablated more seriously and the stainless steel electrode has higher surface roughness. With the increase of discharge times, the breakdown point moves to the electrode edge area, which affects the insulation performance of the switch.
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
Accepted Manuscript  doi: 10.11884/HPLPB202032.190370
[Abstract](2) [PDF 0KB](0)
The armature-rail contact interface effects the characteristics of armature startup in the pulsed high current linear driver. Furthermore, the armature startup has an influence on the system efficiency and life. 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 in ANSYS, the pre-tightening force and contact status can be simulated. Besides, the electromagnetic force and current density can also be obtained by simulation. The results showed that groove increased the flexibility of armature and the homogenous of current distribution by the current skin effect. Owing to the increasing pressure, the groove armature startup was delayed and its contact resistance reduced. It had important significance to improve contact condition and reduce erosion.
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:
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
Corrected proofs  doi: 10.11884/HPLPB202032.190378
[Abstract](23) [PDF 0KB](0)
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%.
Two-phase streamer characteristics in transformer oil under nanosecond impulses voltages
Wang Qi, Wang Meng, Wang Jue, Yan Ping
Corrected proofs  doi: 10.11884/HPLPB202032.190380
[Abstract](33) [PDF 0KB](0)
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.
Experimental study on multi-channel synchronous conduction conditions of GaAs-PCSS
Liu Yi, Shen Yi, Xia Liansheng, Wang Wei, Ye Mao, Zhang Huang
Corrected proofs  doi: 10.11884/HPLPB202032.190328
[Abstract](17) [PDF 0KB](0)
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.
The preliminary study of laser-triggered pseudospark switch
Zhou Liang, Zhang Ming, Sun Chengge
Corrected proofs  doi: 10.11884/HPLPB202032.190094
[Abstract](59) [PDF 1038KB](2)
Laser-triggered pseudospark switches, also called back-lighted thyratrons (BLTs), are low pressure, high voltage, high current glow-mode switches The feasibility of BLTs is verified. The laser beams with wavelengths of 266 nm and 532 nm were used in the test. In the non-focused mode, the minimum trigger energy for 266 nm laser is 15 mJ, the anode ignition delay time is about 340 ns, and the time jitter is about 40 ns. The minimum trigger energy for 532 nm laser is 83 mJ, the anode ignition delay time is about 420 ns, and the time jitter is about 60 ns. In the focused mode, the minimum trigger energy for 266 nm laser is 4 mJ, when the laser trigger energy is 8 mJ, the anode delay time is 190 ns, the jitter is less than 1 ns. The minimum trigger energy for 532 nm laser is 6 mJ, when the laser trigger energy is 8 mJ, the anode delay time is than 240 ns, the jitter is less than 1 ns. The methods to further reduce the energy of the laser trigger will be studied in the future.
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
Corrected proofs  doi: 10.11884/HPLPB202032.190331
[Abstract](48) [PDF 0KB](0)
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.
Influence of metal matrix materials on self-breakdown stability of graphene film cathode
Wang Gang, Liu Sheng, Pan Yafeng, Fan Hongyan
Corrected proofs  doi: 10.11884/HPLPB202032.190297
[Abstract](35) [PDF 961KB](2)
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.
Simulation method of quadruple-level circuit model for stack and vacuum section of Julong-I facility
Mao Chongyang, Xue Chuang, Xiao Delong, Ding Ning
Corrected proofs  doi: 10.11884/HPLPB202032.190330
[Abstract](42) [PDF 588KB](0)
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.
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
Corrected proofs  doi: 10.11884/HPLPB202032.190280
[Abstract](82) [PDF 1017KB](2)
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.
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
Corrected proofs  doi: 10.11884/HPLPB202032.190326
[Abstract](26) [PDF 0KB](0)
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.
Study on temperature rise of electromagnetic coil launcher
Xiong Min, Zhang Yadong, Gong Yujia, Zhang Hu
Corrected proofs  doi: 10.11884/HPLPB202032.190300
[Abstract](29) [PDF 0KB](0)
Synchronous induction coil launcher mainly uses pulse current to supply power directly to the coil. The temperature rise of armature and coil will occur in the actual working process, and it is a major factor restricting the development of coil launcher to miniaturization and high speed. In this paper, the temperature rise model of electromagnetic coil is established. For single trigger, Comsol and self-programmed Coilgun are used to calculate, and the corresponding test platform is built to verify the temperature rise. The Comsol method with direct coupling is the most accurate method, and the change of material parameters with temperature can also be considered. The simulation results show that the temperature rise of armature is about 4.2 ℃ and the maximum temperature rise of coil is 7.7 ℃. Because of the limitation of measurement delay and sampling frequency of thermocouple temperature sensor, the armature temperature test curve can not measure the maximum temperature point in the simulation curve, it can record the temperature change curve in the whole test process. The change of temperature and the final stable temperature are basically consistent with that of the simulation. The maximum error is 6.1%, which shows the accuracy of the simulation. This study lays a foundation for subsequent multi-stage coil continuous launching.
Research of electromagnetic launched fire-extinguishing bomb fire-fighting system
Zhang Yadong, Xiong Min, Dong Mingyang, Lin xiong
Corrected proofs  doi: 10.11884/HPLPB202032.190304
[Abstract](43) [PDF 0KB](0)
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.
Efficiency of distributed energy storage electromagnetic railgun
Wen Yanling, Dai Ling, Zhu Qi, Wang Shaojie, Lin Fuchang
Corrected proofs  doi: 10.11884/HPLPB202032.190332
[Abstract](26) [PDF 0KB](0)
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%.
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
Corrected proofs  doi: 10.11884/HPLPB202032.190327
[Abstract](139) [PDF 1297KB](6)
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.
Study of ultrafast semiconductor opening switch
Wang Ganping, Li Fei, Jin Xiao, Song Falun, Zhang Qi
Corrected proofs  doi: 10.11884/HPLPB202032.190298
[Abstract](45) [PDF 0KB](0)
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.
Thermal analysis calculation of dry-type transformer in PSM high voltage power supply
Xia Yuyang, Li Qing, Mao Xiaohui
Corrected proofs  doi: 10.11884/HPLPB202032.190294
[Abstract](40) [PDF 829KB](1)
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.
 Cover and Content
2019, 31(12): 120000.  
[Abstract](1) [PDF 317KB](1)
High Power Laser and Optics
Theoretical analysis of optical path accurate adjustment in femtosecond pulse measurement process
Shen Miao, Xia Yanwen, Dong Jun, Zhang Bo, Sun Zhihong, Lu Zonggui, Yuan Haoyu
2019, 31(12): 121001-1.   doi: 10.11884/HPLPB201931.190165
[Abstract](45) [PDF 0KB](1)
For the measurement of single shot femtosecond laser pulse, to describe the influence of incident angle and crystal rotation on the output signal accurately, the third harmonic process is analyzed and deduced. In this article, the range of the angle of incident light is derived and calculated mathematically. At the same time, the relationship between the output autocorrelation signal and the crystal’s attitude is analyzed quantitatively. The results show that, to satisfy the phase matching condition, the minimum value of the incident angle is 30.114°. The output direction of the autocorrelation signal is insensitive to the rotation of the crystal. However, the output intensity is sensitive to the intersection angle of two incident beams. The capacity of the crystal rotation is large, and the thinner the crystal is, the less sensitive it is. Moreover, the time resolution of the correlation signal is determined by the angle between the two incident beams in the crystal, the change of the angle outside the crystal does not change the time resolution. The study has reference value for the precise adjustment of femtosecond laser pulse measurements.
Simulation and experimental verification of thermal expansion of metal and glass cementing bodies
Li Guohui, Xu Honglai, Xiang Rujian, Du Yinglei, Wu Jing, Xiang Zhenjiao, Zhang Yue
2019, 31(12): 121002-1.   doi: 10.11884/HPLPB201931.190272
[Abstract](21) [PDF 0KB](0)
The stress of different adhesive bodies were simulated and analyzed at different temperature, and the thermal expansion coefficient of different metals were tested by the Thermal Expansion Instrument. Then, the metals with different thermal expansion coefficient were bonded to the glass separately, then the adhesive bodies were heated in a semi-enclosed space and their deformation were measured by Hartmann. The results show that the simulation data of the adhesive bodies agree well with the experiment data. It can be used to guide the design of thermal expansion matching for different attributes materials.
High Power Microwave
New negative coupling structure and its application on substrate integrated waveguide bandpass filters
Liu Qing, Lü Dalong, Bian Chenge, Zhou Dongfang
2019, 31(12): 123001-1.   doi: 10.11884/HPLPB201931.190189
[Abstract](21) [PDF 0KB](0)
To design cross-coupled substrate integrated waveguide (SIW) bandpass filters (BPFs) with high performance, a new negative coupling structure is proposed, which is constructed by two coupled lines with shorted ends. The negative coupling structure is analyzed in detail. The stracture which can realize both relatively weak and strong negative coupling strength. The optimization method based on characteristic polynomials and reference zeros and poles of scattering parameters is realized for the filter design. To verify the proposed negative coupling structure, two fourth-order cross-coupled SIW BPFs with the center frequency of 10 GHz based on the optimized coupling matrixes are designed. The first one has a normalized bandwidth of 3% with a negative coupling in one cross-coupling path to illustrate the realization of weak negative coupling strength, and the second one has a normalized bandwidth of 8% with a negative coupling in one main coupling path to illustrate the realization of strong negative coupling strength. Finally, the two BPFs are fabricated and measured. Simulation and measurement results are in good agreement, which demonstrates the feasibility of the proposed negative coupling structure and its application on cross-coupled SIW filters with high performance. The influence of weak disperse cross coupling on locations of transmission zeros is also discussed.
Design of broad-band input coupler of W-band TE02 mode gyro-TWT
Wang Zheyuan, Wang Efeng
2019, 31(12): 123002-1.   doi: 10.11884/HPLPB201931.190367
[Abstract](45) [PDF 0KB](2)
In this paper, the input coupler for W-band gyro-TWT is designed to meet the needs of the signal transmission and mode conversion. The input coupler is potential device to be the essential section determining the bandwidth of the whole gyro-TWT. The theoretical analysis of the input coupler of the W-band TE02 mode gyro-TWT is carried out. It is pointed out that one factor affecting the transmission loss of the main mode is that the rise of the miscellaneous modes reduces the transmission coefficient of the main mode, and simulation is done to suppress the miscellaneous modes by optimizing the sizes of the coupling hole, reducing the loss from 3.9 dB to 0.8 dB. According to the simulation sizes processing and cold testing, the final input coupler with 3 dB bandwidth of 7.9 GHz meets the design requirements.
Wideband matching technology used for predistortion linearization
Wang Yongfei, Han Peisheng, Hu Qing, Chen Xinpeng, Zhou Dongfang
2019, 31(12): 123003-1.   doi: 10.11884/HPLPB201931.190128
[Abstract](16) [PDF 0KB](0)
Due to the gain fluctuation and nonlinear characteristic variation of the TWT amplifier chain, predistorter cannot compensate the nonlinearities at different frequencies within the working band, thus nonlinear mismatch might occur and nonlinearity of TWTA could get worse at some frequencies. The wideband linear match theory of predistorter with TWTA is put forward, and the influence of nonlinear mismatch is discussed. Predistorter cascaded with gain compensation unit can flatten the gain fluctuation and match the nonlinearity of TWTA, truly broaden the linear working band of LTWTA.
Design of Ku-band 6 bit digital attenuator of microwave monolithic integrated circuit
Zhou Shouli, Zhang Jingle, Wu Jianmin, Zhou Shancheng, Cheng Yuanfei
2019, 31(12): 123004-1.   doi: 10.11884/HPLPB201931.190049
[Abstract](33) [PDF 0KB](0)
A Ku-band 6 bit digital attenuator of microwave monolithic integrated circuit (MMIC) was developed based on GaAs E/D pseudomorphic high electron mobility transistor (pHEMT) process. The 6 bit digital attenuator was made up of six base states. It could obtain maximum attenuation of 31.5 dB with the attenuation step of 0.5 dB. 0.5 dB and 1 dB attenuation bits were realized by adopting simplified T-type structure. In the 16 dB attenuation bit, a switched-path-type topology was employed to improve the attenuation flatness and reduce the additional phase shift effectively. The measurement results show that in the range of 12−18 GHz, the 64-state root mean square (RMS) error is less than 0.25 dB, the phase variation is from −0.5° to +9.5°, the insertion loss is less than 4.9 dB and the input and output voltage standing wave ratios are both less than 1.5∶1. The chip size is 3.00 mm×0.75 mm. The MMIC chip has the characteristics of wide bandwidth, high attenuation accuracy and small size. It can be mainly used in fields such as microwave phased array radar transceiver components and communication.
Terahertz Technology
Study of 0.8 THz regenerative feedback oscillators
Li Tianyi, Meng Weisi, Pan Pan, Cai Jun, Wu Xianping, Feng Jinjun, Yan Tiechang
2019, 31(12): 123101-1.   doi: 10.11884/HPLPB201931.190372
[Abstract](62) [PDF 0KB](0)
With the development of terahertz technology, high-frequency and high-power terahertz radiation sources have been the focus of researching all over the world. Based on the requirement of 0.8 THz terahertz wave imaging system, the regenerative feedback oscillator is designed and studied by using folded waveguide slow wave structure(SWS). In this paper, the SWS of 0.8 THz folded waveguide is designed and optimized by using the eigenmode solver in CST Microwave Studio. Then the oscillator is simulated and verified by PIC solver in CST Particle Studio. In the initial exploration stage of THz, regenerative feedback oscillator has the advantage of high feasibility and high output power. The simulation results show that a stable output signal of 60 mW can be generated.
Complex Electromagnetic Environment
Design and simulation of beam-wave interaction system of 397 GHz clinotron
Su Siming, Feng Jinjun
2019, 31(12): 123102-1.   doi: 10.11884/HPLPB201931.190368
[Abstract](22) [PDF 0KB](0)
Clinotron is a modification of the backward-wave oscillator. In clinotron the electron beam is inclined to slow wave structure (SWS). Due to the inclined electron beam, electrons are closer to SWS and can interact with stronger electric field, which leads to a higher output power and interaction efficiency. In this paper, the interaction system of clinotron is designed, and the double corrugated waveguide SWS is applied in clinotron for the first time. The dispersion curves, field distribution and beam-wave interaction are simulated with electromagnetic codes and 3D PIC codes. The result shows that more than 100 mW output power and a 50 GHz tuning bandwidth can be obtained. The simulation results show that the maximum output power is 2.3 W at frequency of 370.5 GHz with beam voltage 7.0 kV, beam current 120 mA and guiding magnetic field of 1.0 T.
Analysis on the interference effect of electrostatic discharge of GNSS receiver on aircraft
Fan Yuqing, Cheng Erwei, Wei Ming, Zhang Qinglong, Chen Yazhou
2019, 31(12): 123201-1.   doi: 10.11884/HPLPB201931.190268
[Abstract](39) [PDF 0KB](0)
Aiming at the problem that the Global Navigation Satellite System (GNSS) receiver is susceptible to ESD, the interference effect of the corona discharge on the surface of the aircraft and ESD generated by maintenance on the receiver are studied. The time-frequency domain characteristics of the ESD is analyzed. The front door coupling experiment of corona discharge to the receiver was carried out using a simulator composed of a needle ball electrode and a high voltage source. It is proved that the radiation field generated by the corona pulse has no obvious interference effect on the receiver. Based on the human body metal ESD model, the experiment of the interference effect of spark discharge on the receiver was carried out. It was found that the surge current easily caused potential fluctuation of the serial port conversion chip of the receiver, and the main loop of the read/write program was stuck. ESD protection should be performed for the serial port.
Design of X-band ultra-wide angle scanning phased array antenna
Lu Jiaojun, Wu Hongchao
2019, 31(12): 123202-1.   doi: 10.11884/HPLPB201931.190226
[Abstract](32) [PDF 0KB](2)
–To realize X-band ultra-wide-angle scanning, the paper proposes a novel tightly coupled array antenna unit design, and combines the equivalent circuit to analyze and optimize antenna parameters. With the integrated Marchand balun, dipole and balun can be fabricated on the same PCB, thus reducing antenna’s weight and cost. Introducing the vertical parasitic superstrate and horizontal dielectric layer above the antenna aperture, the two work together to improve the impedance transformation during wide-angle scanning. The results show that the scanning angle ranges up to 80° in E-plane while 70° in H-plane, with an active VSWR<3, in X-band (8–12 GHz). The antenna is simple, compact and easy to fabricate.
Particle Beams Technology
Simulation analysis and test of periodic focusing system with opening magnetic ring
Guo Zugen, Yang Zhixin, Ji Rujing, Han Ping, Zhang Ruifeng, Wang Qi, Wang Zhanliang, Gong Yubin, Gong Huarong
2019, 31(12): 124001-1.   doi: 10.11884/HPLPB201931.190208
[Abstract](33) [PDF 0KB](0)
The magnetic ring at the wave port position of the TWT periodic permanent magnet focusing system usually adopts single open magnetic ring. Two different double-open magnetic rings were proposed because of adding waveguide impedance tuning branch at the wave port position. The magnetic field near the central axis of the double-open magnetic ring was analyzed by using the 3D electromagnetic simulation software Opera-3D, and the design method of the periodic magnetic focusing system of double-open magnetic ring was put forward. In order to verify the feasibility of periodic permanent magnet focusing system with double-open magnetic rings, an electronic optical system of E-band folded waveguide TWT was designed and tested. In the traveling wave tube test, the emission current of the electron gun was 83 mA, and the electron beam flow rate of the periodic magnetic focusing system with double-open magnetic rings was 99%.
Pulsed Power Technology
Study on over-current protection of solid-state Marx generators
Rao Junfeng, Zeng Tong, Li Zi, Jiang Song
2019, 31(12): 125001-1.   doi: 10.11884/HPLPB201931.190138
[Abstract](76) [PDF 952KB](1)
SiC MOSFETs with fast rising time and low switching loss have been gradually used in solid-state pulse generators. In this paper, aiming at protecting solid-state Marx generators from common over-current fault, the damage mechanism of SiC MOSFET is analyzed, and a new driving system with over-current protection is proposed. The drive system not only outputs drive signals with long pulse width, but also provides over-current clamping effect during the whole conducting process of the SiC MOSFET. Based on the relation between gate voltage of SiC MOSFET and drain current, the proposed drive circuit clamps the conducting current amplitude by pulling down the gate voltage of SiC MOSFET with a single sampling resistor and a pair of anti-series zener diodes. Experimental results show that the on-state impedance of the SiC MOSFET remains very low when the conducting current is low and consequently the gate voltage is slightly reduced. When an over-current fault occurs, the conducting current can be quickly clamped through the rapidly rising conducting impedance of the switch since the gate-source voltage is pulled down quickly.
Compressed strong magnetic field confinement effect on alpha particle energy in field-reversed configuration plasma target
Zhao Xiaoming, Sun Chengwei, Sun Qizhi, Jia Yuesong, Qin Weidong
2019, 31(12): 125002-1.   doi: 10.11884/HPLPB201931.190047
[Abstract](151) [PDF 0KB](0)
Based on an one dimensional elastic-plastic reactive hydro-dynamic code SSS-MHD, confinement effect, by strong magnetic field during compression of field-reversed configuration (FRC) plasma target by solid liner, on the alpha particle energy transport is studied numerically. Also, investigations on the alpha particles self-heating (including local and non-local) and end loss effects are carried out. In the physical model, plasma energy is divided into three parts as that of DT ions, electrons, and alpha particles. In addition, fusion reaction in thermal equilibrium is taken into account. Numerical results imply that FRC target behaves like rigid rotor during solid liner compression. The compressed strong magnetic field can well define alpha particle energy in O-point area in target center rather than in the axis area, which is helpful for an FRC plasma burning. The non-local self-heating power peak value locates at O-point, but the local self-heating power maximum is beyond O-point. The plasma temperature peak value of local self-heating is about 0.5 times greater than that of non-local self-heating. In the script-off layer (SOL), end loss effect of alpha particle energy increases with the solid liner convergence. Especially in the SOL boundary, peak alpha particle energy loss rate appears.
Discharge characteristics of a gas switch triggered by ejected plasma
Zhang Mingkang, Liu Xuandong, Shen Xi, Liang Chengjun
2019, 31(12): 125003-1.   doi: 10.11884/HPLPB201931.190243
[Abstract](45) [PDF 1029KB](0)
High speed ejected plasma, generated by the discharge in an actuator, can be applied as a trigger to gas gap switch which is working at low coefficient or with wide gap. This paper studies the influence of working conditions of gas switch on the discharge characteristics of ejected plasma triggered gas switch .The effects of gap distance, gas type, gas pressure, switching coefficient and cooperation mode of trigger pulse polarity and main voltage polarity on the discharge characteristics of ejected plasma triggered gas switch were studied by experiments. The results indicate that the ejected plasma triggered gas switch can be reliably and rapidly triggered with switching coefficient of about 10% . When the gas pressure of N2 in the switch is 0.5 MPa and the gap distance is 5 mm, the delay time and jitter are 11.7 μs and 1.42 μs, respectively. When the distance increases to 18 mm, the probability is reduced, the delay time increases to 19.7 μs. When the switching coefficient increases from 10% to 60%, the delay time decreases from 11.7 μs to 1.1 μs. With the same self-breakdown voltage, high pressure, short gap distance, negative trigger pulse and positive main voltage are better best choices to reduce the delay time.
Accelerator Technology
Nonlinear optimization for longitudinal beam injection in diffraction-limited synchrotron light sources
Shen Siqi, Tian Shunqiang, Zhang Qinglei, Wu Xu, Zhao Zhentang
2019, 31(12): 125101-1.   doi: 10.11884/HPLPB201931.190196
[Abstract](59) [FullText HTML](62) [PDF 726KB](5)
Storage rings of the next generation synchrotron light sources have quite small dynamic apertures with which transverse beam injection can hardly be efficient. The longitudinal beam injection may be a solution to this problem. To apply a longer kicker pulse, it is necessary to increase time offset of the injected beam to the stored one by reducing RF frequency. The beam with a longer time offset will have a higher momentum deviation due to synchrotron motion, thus full injection of this method requires the storage ring to provide large enough energy acceptance and off-momentum dynamic aperture. A candidate lattice of the upgraded Shanghai Synchrotron Radiation Facility (SSRF-U) was used to nonlinearly optimize the longitudinal beam injection. With the optimal results of a series of RF frequencies, it is found that there is a critical RF frequency below which lowering frequency could not help to lengthen the kicker pulse in a given lattice. The beam injection into the SSRF-U storage ring was simulated and reached high efficiency with its critical RF frequency and optimal sextupole gradients.
Design of bremsstrahlung target of 4 MeV flash X-ray machine
He Hui, Yu Haijun, Wang Yi, Dai Wenhua
2019, 31(12): 125102-1.   doi: 10.11884/HPLPB201931.190273
[Abstract](46) [PDF 0KB](1)
Bremsstrahlung converter target is one of the key factors for flash X-ray machine. The bremsstrahlung radiation process in which the electron beam impinges on the target is simulated utilizing the Monte Carlo method, by which the influence of the effective target thickness on the exposure is analyzed, the optimal target thickness and the exposure are also obtained for the 4 MeV flash X-ray machine. The damages of target impacted by the electron beam are compared and discussed for various electron energy deposit density from different sources, such as 12 MeV LIA, Dragon accelerators and 4 MeV flash X-ray machine. The results show that the tantalum distributed target may be the satisfactory solution for the bremsstrahlung target of 4 MeV flash X-ray machine.
Upgrade of CSRe beam diagnostic control system based on EPICS
Li Min, Nie Yonggan, Li Shengpeng, Li Weilong, Dong Jinmei, Chen Yucong, Zhao Tiecheng, Mao Ruishi, Xu Zhiguo, Kang Xincai, Feng Yongchun, Zhao Zulong, Wang Yanmou, Ma Weinian, Yin Yan
2019, 31(12): 125103-1.   doi: 10.11884/HPLPB201931.190144
[Abstract](57) [PDF 3747KB](0)
The experimental Cooling Storage Ring (CSRe) of the Heavy Ion Research Facility in Lanzhou (HIRFL) provides high-quality beam for high-precision mass measurement, atomic physics and other experimental studies. Consequently, accurate measurement of beam parameters is the prerequisite for physical experiments. At present, the control system of CSRe has been upgraded to the EPICS architecture. This paper introduces the current status of the beam diagnostics control system based on EPICS which is affiliated with the accelerator control system. Moreover, some of the beam parameters are measured and analyzed by the upgraded beam diagnostics control system. According to the test results with beam at CSRe, the beam position control system can measure the turn-by-turn position of the injected beam. Furthermore, the calculated turn-by-turn position results show that there is a certain degree of oscillation during the injection process, which affects the injection efficiency directly. The beam current measurement system can achieve precise measurement with DCCT by upgrading a high-resolution data acquisition card, in addition, the D event trigger has been integrated into the beam current control system for receiving the trigger and synchronized information from the virtual accelerator. The upgraded control system is running stably and can measure the beam parameters since the upgrade in 2018 and has been integrated into the graphical user interface (GUI) of the accelerator control system.

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