Pulsed Electromagnetic Radiation Research Articles

Modeling of a Current Injection System for Susceptibility Study

This article deals with the model of a high current injection system associated with its electrical generation–transformation–distribution chain able to reproduce differential or common-mode parasitic currents and voltages induced by the coupling between a nuclear electromagnetic pulse radiation on a global electrical network. Due to the quite complexity of the current injection system, the chosen modeling approach was to use the well-known equivalent Thevenin generator. Because of several hundreds of amperes and volts of current and/or voltage generated and their relatively large spectral occupancy of some tens of megahertz, the measurement of currents and voltages needed to build the model, were carried out with adequate sensors and equipment. Once the model built, the generators have been integrated into Spice circuit simulation tool in order to predict the differential and the common- mode currents and voltages induced at the input of switch-mode power supplies and, for later studies, at some different nodes.

Varying characteristics of electromagnetic radiation from coal failure during hydraulic flushing in coal seam

A large amount of gas, which will do great damage to the environment as a kind of greenhouse gas, is discharged directly into the air in the process of coal mining in China. Majority of coal mines in China are characterized by low permeability, great gas pressure, and low strength feature. These features make it difficult for the extraction of gas, which increases the risk of coal and gas outbursts. In order to improve the permeability of coal seam, hydraulic flushing (HF) technology is adopted. So, the effect of hydraulic flushing will be necessary to be analyzed before gas extraction. In this paper, an electromagnetic radiation (EMR) experiment system of coal seam during hydraulic flushing was established, electromagnetic radiation (EMR) signals produced by the deformation and fracture of coal were studied during hydraulic flushing in coal seam in the Songhe coal mine, Guizhou province, China. The results showed that abundant EMR signals could be produced because of coal deformation and fracture. EMR signals were positively associated with the degree of coal failure. In different coal seams, EMR signals had different features during hydraulic flushing. The greater the gas pressure in the coal seam, the more dilatation energy was released. Higher rupture velocity could generate stronger magnetic signals. During hydraulic flushing, the more serious the rupture of coal, the higher the count of EMR pulses, and the higher the frequency of EMR. The principal frequencies and the amplitudes of waves increased gradually with gradually increasing ruptures. The change of EMR signals after hydraulic flushing was more dramatic than before hydraulic flushing. So, it is feasible and dependable to evaluate the effect of coal seam hydraulic flushing by EMR.

Shielding efficiency of wide-band pulses of electromagnetic radiation by shields based on the needle-punching material

To protect electronic systems from the wide-band pulses of electromagnetic radiation, it is proposed to use the shields designed based on needle-punched and felt materials, including those with impregnating liquids. The shielding characteristics of the obtained shields were measured using a test complex of pulsed electromagnetic fields operating on the principle of reproducing ultrashort electromagnetic pulses of vertical (horizontal) polarization with the amplitude at the beginning of the working area of at least 5 and 50 kV/m. The test complex included voltage pulse generators, high-voltage coaxial cables, an antenna feeder, a digital field indicator, a cable and a remote control button. The effective frequency band of the pulse was from 130 MHz to 2.31 GHz. The pulse power at the beginning of the work was 5.34 MW. In each test, 5 packs of pulses were emitted and pulse amplitudes were measured. Each burst of pulses had a duration of 1 s. The pulse frequency in the packet was 1 kHz. The shielding efficiency averaged over the effective frequency band was calculated and the error was determined. The values of electromagnetic pulse shielding efficiency were obtained, which equaled 9.4.15.5 dB for a needle-punched material with a carbon additive, and 9.7...12.4 dB for felt fabric with a layer of polymer metallized film, which allows using them to design the shields to protect electronic systems from the destructive effects of electromagnetic weapons.

Dispersion and attenuation characteristics of steady-state microwave plasma waveguide

Near the electrostatic plasma frequency, plasma exhibits a relative permittivity near zero, and this property has been used to make transient plasma waveguides at microwave and optical wavelengths by ionizing gases with pulsed electromagnetic fields and laser radiation. However, to our knowledge, no one has constructed a steady-state RF-excited plasma waveguide for the purpose of studying its microwave attenuation and dispersion characteristics. We report here the results of investigations at 2.8–3.7 GHz of a variable-length plasma waveguide up to 30 cm long in which the plasma’s relative permittivity was as low as 0.2. De-embedded S-parameter power loss is as low as 4.6 dB and the dispersion is largely consistent with theory, although further work remains to be done.

A Study on the Characteristics of Electromagnetic Radiation during Deformation and Failure of Different Materials Under Uniaxial Compression

The detection of electromagnetic radiation (EMR) during the fracture of solid materials such as rocks and coal has been widely used in seismic exploration and mine dynamic disaster prediction. As described in this paper, we conduct uniaxial compression tests on coal, cement, and glass materials to determine the characteristic EMR differences among materials. A band-stop filter based on the Fourier transform and the wavelet packet transform method are used to conduct signal denoising and analysis. Basic analyses of the pulse-time characteristics, energy distribution, cumulative energy, and waveform characteristics of EMR are conducted. The research results show that there is a strong corresponding relation between the loading time, loading stress and EMR energy. A large number of EMR events are released in rapid succession during the main rupture of coal and cement, while the EMR events are evenly distributed throughout the whole loading process of glass. For the same material, the maximum EMR amplitude increases with an increasing peak value of the stress. The EMR pulse waveform of coal and cement agrees well with predictions based on the theoretical formula of the electromagnetic dipole oscillation EMR generation mechanism. The paper provides further theoretical basis for understanding the mechanism of EMR, with great significance for improving coal mining safety.

The Barkhausen Method to Investigate Powerful Processes during Action of Piezoelectric Igniters

The Barkhausen method is proposed to clarify the cause of radiation of electromagnetic (EM) pulses during high voltage pulse generation by piezoelectric igniters (PIs). Wide bandwidth of the experimental setup was narrowed for a simultaneous registration of electric and detected EM pulses by a two-channel oscilloscope. The PI was loaded on a high ohmic resistance and high voltage pulses of 8 – 17 kV amplitude and up to 150 ms in total duration were registered. These pulses contained a series of short pulses called Barkhausen type pulses. Duration of these pulses having the relatively high amplitude was 30 – 40 ns. The registration revealed that the radiating EM pulse series corresponded to Barkhausen type pulse series. Short non-radiating negative pulses appearing during the saturated voltage growth were also observed and they had relaxation tails. The analysis showed that the EM pulses are caused as a result of domain switching with high voltage spikes at the PZT cylinders bases, where high electric fields are created. The activity of these switchings weakens when the “age” of PIs increases. The non-radiated pulses resulted from fast internal screening processes in the volume of the cylinders, accompanied by the impact ionization. The increase of the saturation and PI’s “age” causes lengthening of the relaxation tails. The results of practical importance for PIs in monitoring systems are placed. It is concluded that the Barkhausen method in wideband configuration is a convenient experimental arrangement for investigation of powerful processes in ferro-piezoelectric ceramics.

The Electric Field Area in a Vacuum with Moving Charges

An exact analytical expression has been derived for the area of an electric field generated by charged particles moving at constant acceleration in vacuum. An approximate form of the spatial distribution of the electric field area in the vicinity of a point of instantaneous charge stopping is presented. It is shown that quasi-unipolar pulses of electromagnetic radiation with a significant electric area can be generated.

Predicted response of an atom to a short burst of electro-magnetic radiation

In this work, we present a hypothesis that spectral response of atoms or molecules to a pulse of electro-magnetic radiation with fast rising or falling fronts would contain a unique emission line that is located approximately near the frequency of the natural oscillations of optical electrons. The emission of this “pinging” spectral line would exist during the time that is determined by the time of radiative energy loss by the optical electron. The amplitude of the “pinging” spectral line would be higher for the pulses with faster rising or falling fronts. The simulations using our previously developed model confirmed existence of the “pinging” spectral response. If experimentally confirmed, this work could lead to a new high sensitivity, high signal to noise ratio stand-off detection techniques, and to other yet unknown applications.

Semiclassical approach for solving the time-dependent Schrödinger equation in spatially inhomogeneous electromagnetic pulses

To solve the time-dependent Schr\"odinger equation in spatially inhomogeneous pulses of electromagnetic radiation, we propose an iterative semi-classical complex trajectory approach. In numerical applications, we validate this method against ab initio numerical solutions by scrutinizing (a) electronic states in combined Coulomb and spatially homogeneous laser fields and (b) streaked photoemission from hydrogen atoms and plasmonic gold nanospheres. In comparison with streaked photoemission calculations performed in strong-field approximation, we demonstrate the improved reconstruction of the spatially inhomogeneous induced plasmonic infrared field near a nanoparticle surface from streaked photoemission spectra.

Электрическая площадь поля в вакууме с движущимися зарядами

An exact analytical expression is presented for the electric field area generated by the motion of charged particles with constant acceleration. An approximate form of the spatial distribution of the electric area in the vicinity of the point of instantaneous stopping of charges is given. The possibility of generating quasi-unipolar pulses of electromagnetic radiation with a significant electric area is shown.

Mathematical model for temperature estimation forecasting of electrically conductive plate elements under action of pulsed electromagnetic radiation of radio-frequency range

A mathematical model for determining the temperature of an electrically conductive plate element under the action of pulsed electromagnetic radiation of the radio-frequency range is proposed. This model allows us to take into account the influence of the process of thermoelastic energy dissipation on the forecasting of the value of temperature in addition to the joule heat. This process is determined by thermal expansion and the action of poendromotive forces arising in the element. This approach allows us to predict a decrease in the error of temperature determination. On this basis, the distributions of temperature in an electrically conductive plate element under the action of an amplitude-modulated radio pulse have been investigated numerically. Thermoelastic energy dissipation is taken into account when using the frequencies of the carrying electromagnetic oscillations beyond the resonant frequencies and of the first resonant frequency of the electromagnetic field for this element. An estimate of the influence of the process of taking into account mechanisms of energy dissipation on the total value of temperature in the element at the specified action and used frequencies is obtained. This has allowed us to increase the accuracy of temperature measurements in this element.

Analysis of electromagnetic pulses generation from laser coupling with polymer targets: Effect of metal content in target

Powerful lasers interacting with solid targets can generate intense electromagnetic pulses (EMPs). In this study, EMPs produced by a pulsed laser (1 ps, 100 J) shooting at CH targets doped with different titanium (Ti) contents at the XG-III laser facility are measured and analyzed. The results demonstrate that the intensity of EMPs first increases with Ti doping content from 1% to 7% and then decreases. The electron spectra show that EMP emission is closely related to the hot electrons ejected from the target surface, which is confirmed by an analysis based on the target–holder–ground equivalent antenna model. The conclusions of this study provide a new approach to achieve tunable EMP radiation by adjusting the metal content of solid targets, and will also help in understanding the mechanism of EMP generation and ejection of hot electrons during laser coupling with targets.

A Compact High Efficient Wideband Electromagnetic Pulse Radiator

A wideband electromagnetic pulse oscillation and radiation method is studied. A compact high efficient wideband electromagnetic pulse radiator is developed based on this method. Simulation analysis and experimental results show that the radiation device can obtain more than 40% equivalent voltage radiation efficiency.

Investigation of influence of model hydrometeors on characteristics of electromagnetic radiation impulses registered near to artificial thunderstorm cells

Results of the experimental investigations of the influence of the model hydrometeor arrays on the characteristics of the electromagnetic radiation of the channel discharges between the system of the artificial thunderstorm cells of a negative or positive polarity and the ground have been presented in the paper. Parameters of the impulses of the electromagnetic radiation registered by the wideband plate antennas for the first and subsequent return strokes are under a consideration. Significant influence of the array of the large model hydrometeors on the probability of a subsequent stroke initiation and on the parameters of the corresponding electromagnetic radiation pulses has been established and discussed. Found dependencies between the characteristics of the current impulse of the first and subsequent return strokes from the system of the negative and positive artificial thunderstorm cells and the parameters of the impulses of the corresponding electromagnetic radiation have been analyzed. Comparison of the received results with processes of the electromagnetic radiation of a natural lightning has fulfilled.

Ultra high-speed all-optical coherent memory cell

We study the interaction of two counterpropagating unipolar video pulses of electromagnetic radiation in a dense resonant two-level medium. The pulse durations are less than one oscillation period of an atomic transition. We show that a polariton cluster (i.e. the compact long-living strongly coupled state of electromagnetic field and matter polarization) is created, when two unipolar pulses collide in a resonant medium of the frequency ω0 (the pulses correspond to self-induced transparency solitons of the same amplitudes and opposite polarities).We have studied for the first time the conditions of maximal excitation of a resonant polarization in the polariton cluster volume. We show that there exist optimal durations and amplitudes of the recording pulses. We studied the processes of double and multiple recording and erasing of an optical memory cell in a thin layer of a resonant medium (quantum dots). We demonstrated that the pulse rate of the recording-erasing pulses can reach 60 000 GHz and higher, which happens under the coherent regime of the interaction between the electromagnetic field and polarization of the medium.

Comparison of lightning return stroke channel-base current models with measured lightning current

Electromagnetic pulse radiation produced around the lightning stroke channel has caused the disturbance to the microelectronic industry, especially to disturbance of high frequency to electronic systems. Lightning channel-base current function (CBC) characteristics and parameters determine lightning electromagnetic field (LEMF) results obtained on the basis of the used models. This paper evaluated and compared the measured lightning current and six lightning current-based channels models namely Bruce and Golde, Heidler, Diendorfer and Uman, Nucci, Pierce and Cianos and new current-based current (NCBC) models. In terms of the waveshape, among all the six lightning channel-based current models discussed, the models developed by Javor, Nucci and Diendorfer and Uman have showed a good agreement compared to the measured lightning current. In terms of 10-90% risetime and full width half maximum time (FWHM) comparison, NCBC and Nucci models have showed compatible comparison. However, Nucci model is not easily adjustable to different desired pulse-current waveshapes. On the other hand, NCBC model can be simplified, the values of lightning peak current and risetime can be chosen arbitrarily and independently from other parameters, and there is no need for the peak-correction factor, so that reduces the number of parameters. Therefore, the NCBC model was suggested to be used in the future in order to simulate much accurate return stroke model. This knowledge will contribute to the development of a new accurate and efficient return stroke model.

Effective electromagnetic shielding with multi-layer structure material on Shenguang laser facility

Electromagnetic pulses (EMPs) with high intensity and frequency bandwidth can be generated during the intensive laser irradiating solid targets in inertial confinement fusion (ICF). To shield the EMPs radiation and hence protect various diagnostics in and outside the target chamber, we designed a multi-layer structure material to shield the EMPs and demonstrate experimentally and numerically shielding performance of the material structure. The thickness of the multi-layer structure material has a great influence on the EMPs shielding. It is shown that, with the increase of the material thickness, the better shielding performance is obtained, and the material structure with polytetrafluoroethylene of 0.5 mm, copper of 0.4 mm and lead of 2.4 mm reduces 448 times compared the maximum value of EMPs voltage to that without shielded. The design of multi-layer structure material for EMPs shielding provides a promising way to reduce EMPs radiation, which is extremely useful for the diagnostics protection and signal processing in ICF.

Features of electromagnetic radiation in the interaction of a high-speed flow of silicon carbide microparticles with a metal barrier

This work is a continuation of the work, where the results of the theoretical study of the formation of the electromagnetic field in the explosion of the cumulative charge were presented and the hypothesis of the formation of an electromagnetic pulse in the collision of a high-speed flow of particles with a metal barrier was put forward. In the present work, the cumulative charge was used to disperse powder microparticles to speeds of 2500 m/s and to study the processes of collision of high-speed particle flows with an obstacle. The purpose of the work is to study the features of electromagnetic radiation in the collision of a high-speed flow of particles with a solid. The study of the resulting pulse of electromagnetic radiation was carried out according to the developed method by measuring the magnetic field induction using Hall sensors. The average value of the magnetic field induction is 45.9 MT. Registration of the ionizing component and evaluation of the radiation energy were determined by the intensity of photodetector illumination (x-ray film). Evaluation of the particle energy along the path length in the emulsion gives a value of 80-100 MeV. It is shown that the process of high-speed collision and interaction of the microparticle flow. with a metal barrier is accompanied by a number of effects that have not yet been studied. As a result of the research, practical results are obtained that confirm the previously proposed hypothesis and allow to supplement the understanding of the nature of the origin of electromagnetic radiation in the collision of a high-speed flow of particles with a metal barrier in the conditions of their penetration.

Wide-Aperture Liquid Calorimeters for Measuring the Energy of Powerful Microwave Radiation Pulses

An overview was done of the efficient devices designed to measure the energy of powerful electromagnetic radiation pulses of the relativistic microwave sources – liquid calorimeters with wide-aperture absorbing loads. Designs and characteristics of calorimeters are described along with their operational features.

Pantograph–Catenary Arcing Detection Based on Electromagnetic Radiation

Currently, the detection equipment for offline arcing on high-speed trains is of great interest because it can evacuate the contact state between the contact wire and the strip. In order to ensure the safety of the train under the effect of the arcing, the self-designed fourth-order Hilbert curve fractal antenna is chosen to detect the arcing, in this paper, based on its electromagnetic radiation signal. Aspects of time-, frequency-, and joint time–frequency-domain analyses of the signals were considered. Meanwhile, the experiments were conducted several times with different circuit currents and different electrode gaps, and the electromagnetic pulses under different moments were studied. Results indicated that the electromagnetic radiation pulses were corresponding to the abrupt variations of voltage during arcing, and all the characteristic frequencies were located at similar values (18 MHz). Mechanisms of using the short-time Fourier transform method to obtain an accurate arcing moment, extinguished time, and arcing duration have been explained in detail. Thus, the characteristics of arcing electromagnetic radiation could become the significant and efficient parameters to detect the pantograph–catenary operation state of high-speed trains.