Electromagnetic Pulse Simulator Research Articles

The leakage field characteristics of a large hybrid electromagnetic pulse simulator.

The leakage field of a hybrid electromagnetic pulse simulator with horizontal polarization is simulated and experimentally investigated based on the finite integration technique in this paper. The field distribution characteristics and far-field radiation pattern of the simulator are given. The attenuation characteristics of the electric field at specific directions in the z = 2m plane are also predicted by numerical data fitting. Finally, according to the ICNIRP guidelines, the safe distances that satisfy the occupational and public exposure limits are obtained, and the safety regions lower than the reference levels are given. Results show that the electric field in the α = 0° direction is mainly contributed by the main polarization component (Ey), while the total electric field in the α = 90° direction also requires consideration of the vertical component (Ez). The dominant radiation direction in the z = 2m plane lies between α = 0° and 30°, which poses the highest demand for the safe distance around the simulator. In addition, impedance mismatch and ground reflection are the main factors affecting the waveforms of the radiated electric field.

Analysis of the Interference Effects in CMOS Image Sensors Caused by Strong Electromagnetic Pulses

With the electromagnetic environment becoming increasingly complex, it is crucial to address the risk posed by electromagnetic pulse, which critically impairs the performance and reliability of electronic systems based on complementary metal oxide semiconductor (CMOS) image sensors. In this context, research on the failure types of CMOS image sensors in a high-power electromagnetic environment, caused by strong electromagnetic pulses and the rapid evaluation method of interference immunity, has garnered significant interest. This paper conducts electromagnetic pulse simulation experiments on CMOS image sensors to first study their failure types, such as image abnormalities and functional interruption, and then identify the corresponding failure criteria. Furthermore, this study builds on the small sample test evaluation method to investigate the interference threshold of functional interruptions in CMOS image sensors by calculating the failure probability at different field strengths. The obtained data were combined with the Weibull distribution function for fitting, the results of which found the interference threshold to be at 40.4 kV/m. The findings of this study provide a basis for evaluating the survivability of CMOS image sensors and their associated reinforcement technology in high-power electromagnetic environments.

Analysis on the low-frequency electromagnetic pulse coupling to horizontal electrically short lines

In this study, we investigated the coupling features of the nuclear electromagnetic pulse (NEMP) on overhead cables in the middle-and-far regions, different from the transmission line model commonly used for field-line coupling in high-frequency cases, using a simpler lumped approximation to solve the electrically small size model in low-frequency cases. To verify its effectiveness, a simulation model with the same conditions was set up using the software of Computer Simulation Technology (CST), and cable coupling experiments were performed in a laboratory environment using a bounded-wave electromagnetic pulse simulator. The calculated results of the lumped approximation circuit were compared with the CST simulation and measured results, and the agreement was good. The results also shows that the load exhibits a differential response in the case of the low impedance and it is consistent with the excitation signal in the case of the high impedance. Finally, some more experiments were constructed to analyzed the effect of different cable parameters on the cable load response through experiments, and the experimental results are also in general agreement with the theoretical analysis, in which the induced signal of the low-impedance load is mainly determined by the magnetic field in the direction normal to the cable and the ground loop and the induced signal of the high-impedance load is mainly determined by the electric field in the direction of the height of the cable erection.

Development of a 3 MV coaxial peaking capacitor for large-scale electromagnetic pulse simulator.

Coaxial peaking capacitor is a key component in high-altitude electromagnetic pulse (EMP) simulators with fast front pulse output. It poses significant technical and engineering challenges in limiting radiation field amplitude and test space. This paper presents the design and testing of a 180 pF, 3 MV coaxial peaking capacitor with improved insulation performance. In the insulation design, the length of the dielectric film is extended to reduce the background electric field on the flashover path. The electric field threshold obtained from image diagnosis is used as a reference. During capacitor testing, the insulation characteristics are diagnosed using both direct and indirect methods. The voltage measured by a D-dot probe, the output waveform of the Marx generator in the primary source, and the radiation field waveform are analyzed to understand the flashover characteristics of the capacitor and to improve the reliability of the test results. The experimental results demonstrate that the peaking capacitor can operate stably at 3.0 MV. If flashover occurring on the dropping edge of the pulse is permitted, the operating voltage can be greater than 3.7 MV without significantly affecting the radiation field waveform. The analysis on the surface flashover morphology of the peaking capacitor reveals that the flashover mainly occurs at the dropping edge of the capacitor's waveform, indicating that the damage to the film is not serious. This research significantly increases the working voltage of coaxial peaking capacitors and contributes to the development of high-altitude EMP simulation technology.

Design of Self-Integrating Transient Surface Current Density Sensor Integrated Fiber Transmission Link.

The transient surface current density reflects the external coupling of the electromagnetic pulse (EMP) to the tested device. In this paper, the generation mechanism and measurement principle of conductor surface current density are introduced, and the surface current density distribution irradiated by EMP on a typical aircraft structure is simulated and analyzed. The traditional surface current density is usually measured by B-dot antenna, but its output signal is the differential of the measured signal, so additional integrators or numerical integration of the measured data are required. In this paper, a self-integrating surface current sensor based on optical fiber transmission is designed based on the shielded loop antenna with gap structure. The output signal is the real signal waveform to be measured. Compared with coaxial cables, integrated optical fiber transmission improves the anti-interference ability of long-distance transmission signals. At the same time, the design process of the sensor is introduced in detail. The bandwidth of the sensor is 300 kHz~500 MHz, the sensitivity is calibrated at 1.23 (A·m-1)/mV, and the dynamic range is ±25~1400 A·m-1 (35 dB). The surface current of a metal plate is measured in a bounded wave electromagnetic pulse simulator using a detector developed in this paper. The test results show that the developed sensor has good engineering applicability.

Progress in developing high-altitude electromagnetic pulse simulators

Progress in developing high-altitude electromagnetic pulse simulators

Simulation and Experimental Study on Coupling Effect of Fuze under Ultra-wide Spectrum Strong Electromagnetic Pulse

The lack of anti-strong electromagnetic interference ability of fuze has become an important aspect restricting the effectiveness of weapon system. Taking a certain type of fuze as an example, this paper analyzes the coupling mechanism of ultra-wide spectrum transient strong electromagnetic pulse to the fuze, analyzes the action mode of aperture coupling and field line coupling, establishes the mathematical model of space electromagnetic field, and then simulates the effect of aperture coupling and field line coupling of the fuze by using CST Microwave Studio software. It is concluded that the strongest coupling state is when the polarization direction of the electromagnetic field is parallel to the axis of the fuze. Combined with the theory and simulation, the ultra-wide spectrum transient strong electromagnetic pulse simulation system is used to conduct the strong electromagnetic pulse irradiation test, and the electromagnetic pulse effect threshold is obtained. It is concluded that the effect threshold leading to communication failure is about 27~40kV/m, which provides a certain theoretical and experimental basis for fuse strong electromagnetic protection.

Sensitivity Analysis of Conductivity Models in Simulation of High-Altitude Electromagnetic Pulse

The reasonable conductivity model and parameters are important for the accurate simulation of high-altitude electromagnetic pulse. While in most public literature, the fitting formulas of the conductivity parameters are given directly without discussion of their physical meaning. In addition, few investigations were carried out in systematic analysis on the parameter sensitivity of the air conductivity model. In this article, the sensitivity of the parameters in the equilibrium ohmic model is analyzed, indicating that electron mobility is the most sensitive conductivity parameter. The law of the peak electric field with the electron mobility under different conditions of observation direction, burst height, yield, gamma energy, and gamma pulse waveform is systematically explored. It is concluded that a reasonable mobility fitting formula should consider the effects of air density, electric field intensity, and nonequilibrium effect, and the fitting result should be as close as possible to the credible measurement value.

On the Self-Consistent Simulation of High-Altitude Electromagnetic Pulse

Self-consistency between Compton electrons and electromagnetic (EM) fields is an important physical mechanism in the generation and propagation of early-time high-altitude EM pulse (HEMP). This article develops an iterative self-consistent HEMP simulation scheme based on high-frequency approximation (HFA) algorithms. The self-consistent effect between electrons and fields is decoupled and neglected in the first iteration and then is taken into account by considering the results of the field as the independent fields, which affect electrons in the next iteration. The computation can be improved up to tens of times faster than the existing non-iterative method. This article provides a detailed study about self-consistent HEMP with regard to the influence of prompt gamma yield and various prompt gamma ray spectra. The saturation phenomenon caused by secondary electrons is considered as well. The self-consistent effect is significant in the source region. At ground level, it shortens the duration and reduces the amplitude of HEMP. Numerical results showed that the differences caused by self-consistency are significant in the simulation with different prompt gamma yields and prompt gamma ray of monoenergetic and spectrum.

Study on the Influential Mechanism of Fluorination on the Flashover Voltage of Polypropylene Film Under Nanosecond Pulse Voltage

A polypropylene (PP) film is usually employed as the main insulation of the peaking capacitor, which is important in an electromagnetic pulse simulator to generate high-amplitude nanosecond pulse. The flashover voltage of PP films under nanosecond pulse limits the highest working voltage of a peaking capacitor. Surface fluorination was employed to increase the flashover voltage of PP. The flashover voltages of PP samples with different fluorination times (0, 4, and 6 h) were tested in an oven with nanosecond pulse voltage. The results showed that the flashover voltage of the PP film with 6-h surface fluorination was increased about 15% than the untreated film in the air. To clarify the influential mechanism, the physicochemical properties of PP film samples were tested and characterized. The results of thermally stimulated depolarization current (TSDC) showed that the trap density of the PP film increased obviously after fluorination treatment. With the increase in treatment time, the trap depth and density were increased obviously. The surface conductivity of PP films slightly decreased with the increase in fluorination time. The mechanism of surface fluorination on the influence of the flashover performance of the PP film under nanosecond pulse is discussed. It is concluded that surface fluorination significantly increases the carbon–fluorine (C–F) bond of the PP film, resulting in the increase in the depth and density of the surface trap, and then, a large amount of homocharges trapped in the surface trap reduces the electric field near the electrode.

Flashover Voltage of Epoxy FRP Insulators with Different Surface Roughness and Groove under Nanosecond Pulses in SF6

In order to further improve the insulation performance of fiber reinforce plastic (FRP) materials used in electromagnetic pulse (EMP) simulators, the flashover characteristics of FRP materials with different surface roughness and groove, i.e., those who are easily achieved and have a prominent effect, are investigated in 0.1 MPa SF6 under nanosecond pulse voltage with a rise time of 20–30 ns. The experimental results show that surfaces with different roughness have no significant influence on the flashover voltages of the FRP insulators, and both the convex grooves made of FRP and the convex grooves with nylon rings inlaid to form projections can improve the surface flashover voltage of epoxy FRP insulators under nanosecond pulse, in which the effect of the former surface is more obvious. For the insulators with convex grooves made of FRP, it is found that the root of the FRP protrusions breaks down after a number of shots with the occurrence of carbonization channels and spots, which is nonexistent for the nylon projections. Combined with the test results of surface characteristics, the surface roughness and the secondary electron emission yield (SEEY) are not key factors of flashover characteristics in SF6 under nanosecond pulse, arguably due to the fact that the energy needed for an incident electron to ionize an SF6 molecule is lower than that to excite two secondary electrons. Hence, the flashover performance cannot be improved by adjusting the surface roughness, and the flashover channel is principally governed by the macroscopic distribution of electrical field which can be changed by the convex groove. Breakdown phenomena of FRP protrusions indicate that the bulk insulation performance of resin FRP is weaker compared to pure resin because of its composite structure, as well as the impurities and voids introduced in the manufacturing process. The results are instructive for the design of FRP insulation structures in the compact EMP simulator.

Analysis and Experimental Verification of the Peaking Capacitor’s Flashover Process in an EMP Simulator

The flashover process of the peaking capacitor in the electromagnetic pulse (EMP) simulator is studied based on theoretical analyses and experimental verification in this paper. There are deeper and denser ablation spots on the film surface near the inner core of the destroyed peaking capacitor, while the damage of the outer film is relatively slight, which indicates that the flashover current along the inner film is larger. Besides, the circuit simulation analyses show that the earlier the flashover occurs on the film of the peaking capacitor, the smaller the flashover current. The electric field on the non-conical surface of the capacitor is mainly occupied with normal component. Differently, for the conical surface, the electric field on the outer layer is dominated by the normal component and the parallel component is the main part on the inner layer. It is considered that the flashover on the conical surface originates from outer layers and develops gradually to the inner until the flashover penetrates through all layers. Furthermore, the images of flashover show that the flashover firstly occurs on the outermost layers and develops to the inner layers with the increase of the voltage. For such special structure of the peaking capacitor, the parallel component of electric field is more likely to facilitate the flashover under nanosecond pulse. These results may exhibit specific reference implication in the design of insulation for the peaking capacitor used in EMP simulator.

A low-jitter self-triggered spark-discharge pre-ionization switch: primary research on its breakdown characteristics and working mechanisms

MV pulsed switch plays a key role as the transfer switch in large electromagnetic pulse simulators. To broaden the range of self-triggering time, a novel spark-discharge pre-ionization switch, in which the main gap electric field is superposed at the trigger gap to let the electrons in its spark channel also become initial electrons, is proposed and tested. The design idea is: as electrons in the spark channel of the trigger gap always exist after its breakdown, the injection time of pre-ionization should have a more negligible effect on reducing the switch jitter. The experiment results under pulses with a rise time of ∼100 ns support the above assumptions. When the operating voltage is from ∼300 to ∼800 kV and the self-triggering time is ∼45% to ∼75% of the peak time, the breakdown time delay jitter is less than 2 ns, and the breakdown voltage jitter is smaller than 1.25%. Under specific self-triggering time, the breakdown time delay jitter is less than 1.5 ns, and the breakdown voltage jitter is smaller than 0.8%.

Research on the Coupling Characteristics of Electromagnetic Pulse of Electronic Equipment

The problem of electromagnetic interference is becoming more and more prominent in complex environment, and the study of coupling effect between electronic devices is very important to guide the design of electromagnetic protection. In this paper, CST electromagnetic simulation software is used to study the strong electromagnetic pulse coupling effect of the device chassis and harmonious vibration cavity, to simulate the coupling characteristics of the cavity by square hole seam area and the length of the outer cable in the cavity, and then to study the coupling characteristics of the two coupling methods at the same time through simulation and analysis of the coupling electric field and electromagnetic pulse simulation test. The results show that the larger the hole area, the stronger the field strength of coupling into the cavity, and no effect on the resonant point position in the cavity; The longer the cable, the stronger the field force coupled in the center of the cavity, the resonant frequency in the cavity is basically unchanged; When the two coupling methods exist at the same time, the size of the hole seam is small compared to the wavelength, which makes it difficult for electromagnetic waves to enter the inside of the cavity, mainly as cable coupling, and the other is mainly in the form of hole coupling.

A Code Verification for the Cavity SGEMP Simulation Code LASER-SGEMP

The stochastic Richardson extrapolation-based numerical error quantification (StREEQ) technique has been applied to accomplish a code verification for the cavity systemgenerated electromagnetic pulse (SGEMP) simulation code LASER-SGEMP. Here, the grid convergence index method estimates the discretization error caused by the finite difference, while the bootstrap sampling demonstrates the sampling error arising from the inherent stochastic noise. The electric field waveforms obtained by the LASER-SGEMP code agree well with the high precision solution from a reference. According to the StREEQ method, the convergence value of the electric field at 1.8 ns is calculated to be 0.955 V/m and the numerical error characterized by the 95% confidence interval is [0.948, 0.964] V/m, while the high precision solution is 0.961 V/m. Therefore, the code verification has supported the accuracy of the LASER-SGEMP code, and the StREEQ technique is proved to be capable of estimating the numerical error of the cavity SGEMP simulation.

Simulation of High-Altitude Nuclear Electromagnetic Pulse Using a Modified Model of Scattered Gamma

High-altitude electromagnetic pulse (HEMP) generated by the photons from nuclear explosions is a threat to electronic and power systems. During the generation of HEMP, besides the gamma rays released directly by the nuclear devices, the scattered gamma rays can also produce recoil electrons that contribute to the Compton current and further conduction current. Therefore, the gamma-ray model containing both direct and scattered gamma is more accurate to be used in the simulation of HEMP environments. In this article, the modified gamma-ray model based on single-scattering approximation which considers the effects of scattered gamma is presented and the results of the modified model and the traditional prompt-gamma-only model are compared. It is concluded that the scattered gamma rays have little effect on the peak value and rising edge of HEMP. However, the scattered gamma rays influence the electric field at the end of early-time HEMP greatly. This method is also an approach to the scattered gamma component of intermediate-time HEMP.

Design of a high-precision and widely tunable bounded-wave electromagnetic pulse simulator

This paper introduces a high-precision and continuously tunable medium bounded-wave electromagnetic pulse simulator, which adopts a widely tunable, automated novel high voltage pulse source of compact size with fast rise time. Based on fiber transmission automation control is realized, anti-jamming problem is solved and HEMP simulation ability is promoted. Parameters of the simulator are: the rise time about 2.5 ns, FWHM 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.

Regularity analysis of leakage-field from vertically polarized bounded wave electromagnetic pulse simulator with distributed load

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.

All solid-state electromagnetic pulse simulator based on the 4H-SiC photoconductive semiconductor switch.

To study the damage and protection mechanism of an electromagnetic pulse to an electronic system, an all solid-state high-voltage pulse power with photoconductive semiconductor switch is developed, which is a component of the bounded wave electromagnetic pulse simulator. The output peak voltage of the prepared all solid-state pulsed power source was 74.5 kV, the risetime was 2.05 ns, and the pulse width was 22 ns. In addition, the peak voltage of the output pulse of the all solid-state pulsed power source could be regulated. The all solid-state electromagnetic pulse simulator developed in this work can generate an electromagnetic environment with a risetime of 2.2 ns and a pulse width of 23.5 ns.

Design of a Small NEMP Simulator for the Immunity Test of Core Electronic Components in HEMP Environments

We design a small nuclear electromagnetic pulse (NEMP) simulator to study the immunity of core electronic components in high-altitude electro-magnetic pulse (HEMP) environments. The NEMP simulator comprises of a power device, a high-voltage charging part, a pulse-shaping part, and the input taper. The performance of the proposed simulator is verified by the actual experimental results. The positive and negative polarities for the mono pulse output of a transient pulse generator are checked against the standard. The field uniformity of the proposed NEMP simulator is 1.6 dB and fully meets the standard.