Electromagnetic Pulse Simulator Research Articles

纳秒级激光惯性约束装置靶室内电磁脉冲数值模拟

纳秒级激光惯性约束装置靶室内电磁脉冲数值模拟

NUMERICAL ANALYSIS OF SAFETY ZONE OF A LARGE FLAT-PLATE BOUNDED-WAVE EMP SIMULATOR.

The safety zone of a large flat-plate bounded-wave electromagnetic pulse simulator was analyzed using the 3D electromagnetic simulation software Computer Simulation Technology. First, the double-limit requirement cited from the GB 8702 for an instantaneous pulse was clarified compared with the International Commission on Non-Ionizing Radiation Protection guidelines. This means that both the amplitude of the time-domain waveforms and all frequency components should be satisfied with the respective exposure limits. Then, the leakage field of a large flat-plate bounded-wave simulator was simulated. After analyzing the peak amplitude of an instantaneous electric field in a certain area, the observation points along six directions were specified, and the corresponding amplitudes were given. Furthermore, it was verified that the time-domain electric field of the critical points was satisfied with the frequency-domain exposure limits. Finally, the safety distances lower than the reference levels were given, and the safety zones corresponding to the three common exposure limits were obtained.

A coaxial film capacitor with a novel structure to enhance its flashover performance.

As one of the key components of an electromagnetic pulse simulator, the peaking capacitor is coaxially constructed with a laminate structure utilizing alternative thin metal rings and polymer film dielectrics, which is designed as a part of the antenna. This paper presents a coaxial film capacitor with a novel structure to improve its flashover performance. First, the relationship between the capacitance and the capacitor's structural parameters are deduced, and a theoretical basis of lengthening the polymer film dielectrics to enhance the flashover performance is discussed. Based on the theoretical analysis, two 150 pF, 3-layer coaxial film capacitors with different extended lengths for the polymer film dielectrics (10 and 60 mm) are designed and developed. For the capacitor with a 60 mm extended film dielectric, the polymethylmethacrylate rings are adhered to the thin metal rings to support the polymer film dielectrics using a soft adhesive. Electric field analyses show that a longer extended length could decrease the surface field at the edge of the polymer film dielectric by as much as 93%. Comparative insulation experiments show that the flashover voltage for the improved capacitor is 89.9% higher than the original one. The influence of the capacitor's polymer extensions (including the polymer supporting rings and the film dielectrics) on the radiating field of a cone antenna is analyzed numerically, and the results show that only slight changes are introduced into the radiating field. Finally, a designed 350 pF, 20-layer coaxial film capacitor with lengthened film dielectrics is presented.

Variation and Saturated Phenomena of Polypropylene Film Flashover Voltage Under Different SF6 Pressures

In the practical operation of an electromagnetic pulse (EMP) simulator, the flashover phenomenon on the edge of polypropylene dielectrics dominates the insulation failure mode of a peaking capacitor. To analyze the characteristics of polypropylene film flashover voltage under high-pressure SF6, an experimental platform was established, and the pulse generator could output a pulse with a rise time of approximately 27 ns. The experiments were performed on finger electrodes, and the SF6 pressure was set from 0.1 to 1.0 MPa. The experimental results show that the relationship of flashover voltage and gas pressure could be divided into two regions: in low-pressure regions, the flashover voltage increases with the gas pressure linearly and in high-pressure regions, the growth of flashover voltage gradually slows down and approaches a saturation value. As the gap distance increases, the saturation point of gas pressure decreases, and even when close to 0.4 MPa, with a 9-mm gap distance, this unconventional phenomenon cannot be ignored, particularly in practical EMP simulators. When the high surface resistivity and the charge trap distribution on the polypropylene film are considered, the accumulation and emission of surface charges on the film might be the primary reason for the saturated phenomena.

Design of Wideband GHz Electric Field Sensor Integrated with Optical Fiber Transmission Link for Electromagnetic Pulse Signal Measurement.

The detection of high frequency overvoltage and partial discharge is of great significance in evaluating the insulation condition of high-voltage power equipment. A wideband GHz electric field (E-field) sensor for electromagnetic pulse (EMP) signal measurement was proposed in this paper. An optical fiber transmission link was adopted in the design in order to implement high-voltage isolation and reduce electromagnetic interference during transmission. The designed sensor was mainly made up of a differential electric field (D-dot) antenna, transmitter, and receiver. The D-dot antenna was designed to detect high frequency E-field strength and generate a corresponding voltage signal, which was converted into an optical signal by the transmitter. The optical signal could be transmitted a large distance through an optical fiber without electromagnetic interference and changed back to a voltage signal again by a receiver. The design process of the sensor was introduced in detail, and experiments were performed using a gigahertz transverse electromagnetic (GTEM) cell and an EMP simulator to verify it. The results indicated that the designed sensor had a good performance besides an expectable delay due to the optional amplifier.

Survey and design study of mesoband high power electromagnetic pulse radiator

The mesoband high power electromagnetic pulse is a main development direction of high power microwave technology in recent years, the simulator can be used in the research of radiation environment simulation and effect study of high power electromagnetic pulse.This paper reports the survey of the mesoband high power electromagnetic pulse simulator and the common characteristics of the simulator in the working frequency and technical mode. A mesoband high power electromagnetic pulse is described, in the design, the mesoband antenna can be driven by a Marx generator directly. According to the experimental results of the simulator, the wide spectrum radiation factor is 224 kV, the repetition frequency is 40 Hz, the center radiation frequency is 215 MHz, and the spectrum width is 32%. It is concluded that the design requirement is well satisfied，the simulator can provide reference and test foundation for further development and scientific research.

Simulation computation and analytic modification of characteristic impedance of parallel-plate transmission line

Based on time domain reflection theory, a novel way to calculate the characteristic impedance of a parallel-plate transmission line is proposed. With CST microwave studio, a simulation model is established to calculate the accurate value of the characteristic impedance of the parallel-plate transmission line. Based on the results, the analytic formula for the characteristic impedance of the parallel-plate transmission line is modified. Furthermore, the effect of broadening of the bottom plate of parallel-plate transmission line on its characteristic impedance is researched. Considering the effect of broadening of bottom plate, a new formula for the characteristic impedance of the parallel-plate transmission line is proposed. The final formula could be applied to the calculation of the characteristic impedance of bounded-wave simulators and other electromagnetic pulse simulators with similar structure.

Gauss–Seidel Iterative Solution of Electromagnetic Pulse Coupling to Three-Conductor Transmission Lines

This paper proposes a distributed analytical representation and Gauss-Seidel iterative technique (Seidel-DARIT-field), which has a faster convergence rate than the Jacobi-DARIT-field method in the simulation of electromagnetic pulse (EMP) radiated field coupling to multiconductor transmission lines (MTLs) and is more valid and accurate. The process of the first iteration in this method is similar to that in the Jacobi-DARIT-field method. At the second iteration and after, every line will be updated based on the present iteration state of other lines.

10m高分布式负载有界波电磁脉冲模拟器的模式分析

10m高分布式负载有界波电磁脉冲模拟器的模式分析

A 800 kV compact peaking capacitor for nanosecond generator

An extremely compact high voltage peaking capacitor is developed. The capacitor has a pancake structure with a diameter of 315 mm, a thickness of 59 mm, and a mass of 6.1 kg. The novel structural design endows the capacitor with a better mechanical stability and reliability under hundreds of kilovolts pulse voltage and an inner gas pressure of more than 1.5 MPa. The theoretical value of the capacitor self-inductance is near to 17 nH. Proved by series of electrical experiments, the capacitor can endure a high-voltage pulse with a rise time of about 20 ns, a half-width duration of around 25 ns, and an amplitude of up to 800 kV in a single shot model. When the capacitor was used in an electromagnetic pulse simulator as a peaking capacitor, the rise time of the voltage pulse can be reduced from 20 ns to less than 3 ns. The practical value of the capacitor's inductance deduced from the experimental date is no more than 25 nH.

Simulation of EMP Inject Effects Based on Improved Elman Network

In order to quickly determine the performance of a transient voltage suppressor (TVS), improve time domain identification capability of Elman network, the simulation of electromagnetic pulse (EMP) inject effects based on improved Elman network is proposed. Derivation proved that improved Elman network trained by standard BP algorithm has a similar form with the basic Elman network trained dynamic BP algorithm. We establish and improve its Elman network predictive modeling based on the measured parameters of TVS and then demonstrate that improved Elman network has the characteristics of quick speed, high precision, good performance and strong generalization ability, and broad use of prospects.

辐射式核电磁脉冲模拟器TEM喇叭天线

For the problem that TEM horn antenna used in the radiating-wave nuclear electromagnetic pulse (NEMP) simulator has limited ability of low frequency radiating, two basic types of TEM horn antennas (composed of plates and wires respectively) are analyzed. Based on TEM horn antenna composed of wires that can make simulator lighter, a new type of TEM horn antenna is designed by using the structure of helixes end and attaching the shielded plates circuit to antenna. Results show that compared with the common type of the TEM horn antenna composed of wires, this new type of antenna has improved the ability of low frequency radiating greatly. The pulse width of near field waveform is longer by almost seven nanoseconds, and the peak value of pulse is larger by almost one kilovolt per meter. Increasing the radius of helixes and decreasing the pitch of helixes can further enhance both pulse width and peak value of the field strength. Meanwhile, attaching the shielded plates circuit to antenna can further lower down the wave crest generated by reflected signals, which makes the near field waveforms much better.

垂直极化平行板有界波电磁脉冲模拟器辐射近场的快速估算方法

For fast estimating the time-domain near-fields of flat-plate bounded wave electromagnetic pulse(EMP) simulator with vertical polarization, scattering transfer function method is used in time-domain simulation of this kind of simulator. A Gaussian pulse, whose effective frequency domain is wider than that of a given pulse source, is found firstly. And the time-domain response of electric fields at some testing points in the simulator excited by the Gaussian pulse source can be got by finite-difference time-domain (FDTD) method. Then the transient response of electric field at each testing point as the simulator excited by the given pulse source can be computed by Fourier transform, system transfer function and inverse Fourier transform. The results are well consistent with those got by FDTD method as the simulator is excited by the given pulse source directly. The method in this paper is useful for fast estimating radiation near-fields of a fixed simulator with different exciting sources. It has the advantages of reducing FDTD simulation time, saving much computing time and CPU storage especially for medium or large simulators.

分布式负载平行板有界波电磁脉冲模拟器的模拟分析

分布式负载平行板有界波电磁脉冲模拟器的模拟分析

Time-Domain Simulation and Measurement of a Guided-Wave EMP Simulator's Field Uniformity

Field uniformity is crucial to ensuring the validity of test results for electromagnetic field facilities. In this paper, the field uniformity of a guided-wave electromagnetic pulse simulator is directly assessed by a numerical computational method based on the finite integration technique. The results of the numerical simulation are compared with those of the corresponding experiment, and the satisfactory agreement is obtained.

Application of TEM horn antenna in radiating NEMP simulator

In order to design a small radiating nuclear electromagnetic pulse simulator with fast rise time, we have investigated the application of TEM horn antenna in this kind of simulator. The TEM horn antenna is excitated by the integral double exponential pulse. Farfield response in time domain is analyzed based on the step response formula which is derived from the equivalent transmission line model of TEM horn antenna. Principle of antenna parameters selection is determined. The results of numerical calculation give a show of the radiation waveform and some problems. Then experiments are implemented and results are compared with the radiation waveforms generated by double exponential pulse excitation. It suggests that the TEM horn antenna can be used as radiating antenna in the NEMP simulator, which can radiate double-exponent-like pulse with the integral double exponential pulse as excitation. Meanwhile, impedance loading can improve farfield waveforms and enhance the low-frequency radiating ability of antenna.

A New Type of TEM Horn Antenna for High-Altitude Electromagnetic Pulse Simulator

A new type of transverse electromagnetic (TEM) horn antenna for high-altitude electromagnetic pulse (HEMP) simulator is designed in terms of the structure of circular helix end and shielded plates circuit. The finite-difference time-domain (FDTD) method is applied to build the antenna model and to calculate waveforms of antenna radiation filed. Results suggest that the new type of antenna can broaden the pulse width and raise the peak field strength value of radiated pulses. Furthermore, the improvement of radiation in lower frequencies reaches a degree of several decibels in amplitude frequency spectrum. Meanwhile, a new index called “waveform similarity” for confirming the similarity of field waveforms with that of standard specification is proposed and calculated for near-field waveforms of different TEM horn antennas. It is shown by the new index that the field waveform radiated by the new type of TEM horn antenna is much closer to standard waveform.

Performance and Structure of an EMP Simulator

The electromagnetic pulse simulator designed in this paper consists of an adjustable direct current high voltage source, a capacitor for energy-storage, an air spark gap switch, a resistive divider for measurement and a GHz transversal electromagnetic wave (GTEM) cell. The analysis model is constructed based on the theory of transmission line. Influencing factors, such as self-load and impedance mismatch of the transmission line (as well as the cell), were analyzed using Pspice. The self-load has the effect of parallel connection with the load of GTEM cell. It may increase the rise-time, decrease the fall time and reduce the voltage peak. The sudden change of the transmission line impedance will make the waveform of pulse contain reflected oscillation. Four types of resistance divider link were also simulated using Pspice. Improper connection of the resistance divider will cause the waveform of pulse oscillation and lengthen the rise-time, which can be reduced by shorting the high voltage lead, using system structure with gradually changing resistance or connecting a damping resistance at the end.

腔体系统电磁脉冲模拟中的电子发射面

The setting method of electron emission boundary in cavity system generate electromagnetic pulse(SGEMP) simulation is researched. The electron emission boundary in bottom incidence cavity SGEMP simulation is introduced, and the peculiarity of the boundary in side incidence cavity SGEMP simulation is analyzed. By the employment of virtual-emission-surface, the electron emission boundary in side incidence cavity SGEMP simulation is realized. It is indicated that by using the method mentioned here one can achieve the electron emission boundary efficiently, both in flat and curved surface boundary condition, and the parameters and emission sequence of electron on the boundary obey the corresponding physical laws.

基于感应叠加技术的重复频率电磁脉冲模拟器

基于感应叠加技术的重复频率电磁脉冲模拟器