Propagation Of Electromagnetic Pulses Research Articles

Generation of unipolar electromagnetic pulses in semiconductor nanocrystals

Generation of unipolar electromagnetic pulses in semiconductor nanocrystals

Self-similarity of rogue wave generation in gyrotrons: Beyond the Peregrine breather

Within the framework of numerical simulations, we study the gyrotron dynamics under conditions of a significant excess of the operating current over the starting value, when the generation of electromagnetic pulses with anomalously large amplitudes (“rogue waves”) can be realized. The averaged shape of high-power pulses is shown to be very close to the celebrated Peregrine breather. At the same time, we demonstrate that the relation between peak power and duration of rogue waves is self-similar, but does not reproduce the one characteristic for Peregrine breathers. Remarkably, the discovered self-similar relation corresponds to the exponential nonlinearity of an equivalent Schrödinger-like evolution equation. This interpretation can be used as a theoretical basis for explaining the giant amplitudes of gyrotron rogue waves.

Utilization of Capacitor Bank for Electromagnetic Pulse Crimping

Capacitors play an important role in an electrical system. They have numerous applications in the field of lasers, fast X-ray, neutron sources, electromagnetic pulse generators, electron beam accelerators, plasma generation and electromagnetic welding of materials. One of the applications of high voltage capacitors as energy storage and discharge devices is in the crimping of cables using the electromagnetic pulse forming technique. This research paper investigates the use of a high-voltage energy storage capacitor with a capacitance of 208 microfarads and rated voltage of 44 kV to perform Electromagnetic Pulse Crimping (EMPC) of lugs for 70 mm2 and 120 mm2 cables. The capacitor operates at 12 kV and is discharged to produce a high current that generates a strong magnetic field of up to 20 Tesla, which is utilized for joining the cable conductor and the lug. The study examines the performance of the capacitor under different operating values such as voltage, capacitance, and discharge time and investigates the effect of these parameters on the termination quality. The paper presents the experimental results of the crimping, which include the contact resistance, weld strength, microstructure, and defects of the welded joints. The results indicate that the capacitor-based electromagnetic pulse crimping produces welds with high strength and minimal defects. Additionally, the paper discusses the future scope of research in this area and the potential applications of such capacitors in other welding techniques. The findings of this research paper provide valuable insights for engineers and researchers working in the field of energy storage, high-voltage applications and welding.

Transformation of the Shape and Spectrum of an Ultrawideband Electromagnetic Pulse in a “Gigantic” Coaxial Line Filled with Magnetized Plasma

A propagation of ultrawideband electromagnetic pulses (UWB EMPs) through magnetized plasma has been experimentally studied using a “gigantic” coaxial line, which has been developed at IAP RAS for laboratory modeling of ionospheric effects. This coaxial line is 1.4 m in diameter and 10 m in length and is installed inside the chamber of the large-scale Krot plasma device. The line can be filled with rf inductively coupled plasma, magnetized or not. It allows one to explore the propagation of UWB EMPs in plasma along a long path without refraction and divergence and obtain a physical picture of EMP transformation. Under conditions where the duration of the UWB EMP is comparable to the period of electron plasma oscillations (fp−1), the period of cyclotron rotation of electrons (fc−1), or even significantly shorter, a complex of effects of transformation of the waveform and frequency spectrum of the pulse occurs. Without ambient magnetic field, a UWB EMP is distorted due to the effects of the cutoff and frequency dispersion. In dense magnetized plasma, i.e., when fp >> fc, the UWB EMP breaks into two wave packets, the high-frequency one (f > fp) and low-frequency one (f < fc). In rare magnetized plasma (fp << fc), the cyclotron absorption produces a long train of damped oscillations at a frequency close to the cyclotron frequency fc following the UWB EMP.

Mitigation of electromagnetic pulses interfering with Thomson parabola ion spectrometers at XG-III laser facility.

The Thomson parabola ion spectrometer is vulnerable to intense electromagnetic pulses (EMPs) generated by a high-power laser interacting with solid targets. A metal shielding cage with a circular aperture of 1mm diameter is designed to mitigate EMPs induced by a picosecond laser irradiating a copper target in an experiment where additionally an 8-ns delayed nanosecond laser is incident into an aluminum target at the XG-III laser facility. The implementation of the shielding cage reduces the maximum EMP amplitude inside the cage to 5.2 kV/m, and the simulation results indicate that the cage effectively shields electromagnetic waves. However, the laser-accelerated relativistic electrons which escaped the target potential accumulate charge on the surface of the cage, which is responsible for the detected EMPs within the cage. To further alleviate EMPs, a lead wall and an absorbing material (ECCOSORB AN-94) were added before the cage, significantly blocking the propagation of electrons. These findings provide valuable insights into EMP generation in large-scale laser infrastructures and serve as a foundation for electromagnetic shielding design.

Generation and regulation of electromagnetic pulses generated by femtosecond lasers interacting with multitargets

Generation and regulation of electromagnetic pulses generated by femtosecond lasers interacting with multitargets

Propagation of electromagnetic pulses with nonzero area in dissipative media

The propagation of ultrashort electromagnetic pulses with a nonzero electric area in dielectric and conducting media is studied in the frame of a unidirectional propagation model. General solutions for the electric pulse area are obtained for different types of media with a linear response to the external field. It is shown that the evolution of the electric area of the pulse is dramatically different for conducting and non-conducting media. In the case of dielectrics, where the current induced by an external field arises from the polarization of bound electrons, the electric pulse area is an invariant of pulse propagation in spite of the dissipation process. For media with free charge carriers (plasma or semiconductors), the electric pulse area decreases with time due to Joule heating of the media by the static component of the field.

О направленном излучении сверхкоротких электромагнитных импульсов и фрактальной геометрии пространства-времени

Theoretical and experimental investigations of propagation of ultrashort electromagnetic pulses (US EMP) are needed to develop new technologies of creation of modern special engineering. The analytical method of field calculation of travelling antenna waves taking into account reflection of fracture and redistribution of currents in wires because of losses of radiation energy from fractures is considered. The calculations of V-antenna, the field of radiation of a horn system and the pulse radiation of the antenna with a reflector are presented. Experimental investigations of UWB EMP propagation carried out on the basis of the theory developed by S.A. Podosenov are the base of creation of modern radiotechnical complexes. Simultaneously the main conceptions of space-time fractal geometry of deterministic structures are introduced.

Dispersive propagation of nuclear electromagnetic pulse in the ionosphere

Introduction: On the propagation path to the satellite, the ionosphere will distort the nuclear electromagnetic pulse (NEMP) and change its physical properties.Methods: This paper proposes a method for calculating the propagation of NEMP to the satellite. The method decomposes NEMP into the superposition of simple harmonic waves, and each simple harmonic wave is calculated separately in the ionosphere. With the consideration of different time of arrival and critical frequency of the ionosphere, the NEMP after propagating in the ionosphere is obtained by superposition of simple harmonic waves in time domain rather than the inverse Fourier transform which will erase the time domain information.Results: The results show that NEMP is dispersive in ionosphere with the pulse broadened, the speeds changed and the bandwidth narrowed. The time-frequency spectrum can provide the frequency band where the signal energy is located.Discussion: Our proposed method provides a simple and effective way to calculate the NEMP propagation in the ionosphere, which should afford help to the design of NEMP receivers and the selection of satellite orbit altitude.

GENERATION OF RECTANGULAR NANOSECOND ELECTROMAGNETIC PULSES WITH A PICOSECONDS RISE FRONT

A method for generation of ultra-wideband electromagnetic pulses with a nanosecond duration and a picosecond rise time has been studied. The emitter is a horn antenna with a photoconductive switch irradiated by laser pulses. It has been shown that the duration of ultra-wideband electromagnetic pulses is determined by the length of the antenna and the semiconductor material, and the rising front is determined by the front of the laser pulses used to initiate the photoconductive switch. The work shows typical pulse durations of ~1 ns with a rising edge of up to ~34 ps.

Generation of Rectangular Nanosecond Electromagnetic Pulses with a Picosecond Rise Front

Generation of Rectangular Nanosecond Electromagnetic Pulses with a Picosecond Rise Front

Emulating Radiative Field of Electromagnetic Pulse Generator Deployed With Co-Design Capacitor Under Dynamic Switching Process

Emulating Radiative Field of Electromagnetic Pulse Generator Deployed With Co-Design Capacitor Under Dynamic Switching Process

Maxwell–Bloch equations without spectral broadening: the long-time asymptotics of an input pulse in a long two-level laser amplifier

We study the problem of propagation of an input electromagnetic pulse through a long two-level laser amplifier under trivial initial conditions. In this paper, we consider an unstable model described by the Maxwell–Bloch equations without spectral broadening. Previously, this model was studied by Manakov in (1982 Zh. Eksp. Teor. Fiz. 83 68–75) and together with Novokshenov in (1986 Teor. Mat. Fiz. 69 40–54). We consider this model in a more natural formulation as an initial-boundary (mixed) problem using a modern version of the inverse scattering transform method in the form of a suitable Riemann–Hilbert (RH) problem. The RH problem arises as a result of applying the Fokas–Its method of simultaneous analysis of the corresponding spectral problems for the Ablowitz–Kaup–Newell–Segur equations. This approach makes it possible to obtain rigorous asymptotic results at large times, which differ significantly from the previous ones. Differences take place both near the light cone and in the tail region, where a new type of solitons is found against an oscillating background. These solitons are physically relevant, their velocities are smaller than the speed of light. The number of such solitons can be either finite or infinite (in the latter case, the set of zeros has a condensation point at infinity). Such solitons cannot be reflectionless, they are generated by zeros of the reflection coefficient of the input pulse (and not by poles of the transmission coefficient). Thus our approach shows the presence of a new phenomenon in soliton theory, namely, the boundary condition (input pulse) of a mixed problem under trivial initial conditions can generate solitons due to the zeros of the reflection coefficient, while the poles of the transmission coefficient do not contribute to the asymptotics of the solution.

Propagation of intense electromagnetic pulse with a small conical phase shift induced by Axicon optics.

The conical phase shift induced by the axicon generates a non-diffracting Bessel beam. In this paper, we examine the propagation property of an electromagnetic wave focused by a thin lens and axicon waveplate combination, which induces a small amount of conical phase shift less than one wavelength. A general expression describing the focused field distribution has been derived under the paraxial approximation. The conical phase shift breaks the axial symmetry of intensity and shows a focal spot-shaping capability by controlling the central intensity profile within a certain range near focus. The focal spot-shaping capability can be applied to form a concave or flattened intensity profile, which can be used to control the concavity of a double-sided relativistic flying mirror or to generate the spatially uniform and energetic laser-driven proton/ion beams for hadron therapy.

Collisional particle-in-cell investigations of electromagnetic pulses in hypervelocity impact plasmas

A collisional, 2D discontinuous Galerkin particle-in-cell (DG-PIC) code is developed to analyze electromagnetic pulses (EMPs) generated from hypervelocity impact plasmas. The discontinuous Galerkin scheme is used to solve the 2D transverse electric Maxwell’s equations while the particle-in-cell scheme is used to model charged species dynamics. Two models for Coulomb collisions are tested: a small-angle “particle-moment” model and a general Langevin equation model. Both collisionless and collisional simulations are able to reliably reproduce EMP generation due to charge separation within the bulk and the resulting electrostatic oscillations that occur. Both collision models cause a decrease in the frequency of the EMPs that are formed; however, this decrease is not significant enough to explain the discrepancy between experiments and simulations in previous literature. Despite this, Coulomb collisions can be significant in the physics of the plasma behind EMP generation for hypervelocity impacts, particularly in increased heating within the plasma. Overall, although Coulomb collisions are highly influential in the temperature of the plasma, they are not important in the EMP generated and its threat to spacecraft.

Nonlinear Phenomena During the Propagation of Powerful Nanosecond Electromagnetic Pulses in Large-Scale Strip Lines in Gas at Low Pressure

Nonlinear Phenomena During the Propagation of Powerful Nanosecond Electromagnetic Pulses in Large-Scale Strip Lines in Gas at Low Pressure

NONLINEAR PHENOMENA DURING THE PROPAGATION OF POWERFUL NANOSECOND ELECTROMAGNETIC PULSES IN A LARGE-SCALE STRIPE LINES WITH A GAS AT REDUCED PRESSURE

Experiments of propagation of the high-power high-voltage nanosecond and subnanosecond pulses in large-scale transmitting lines in various gases make it possible to solve a wide range of fundamental and applied problems, from simulating the propagation of electromagnetic pulses (EMP) through the atmosphere to estimating the electrical strength of elements of pulsed high-voltage gas-filled systems. At the IAP RAS, experiments with stripe lines up to 5 m in length are performed in Krot and Sprite devices. During the propagation of EMP with an electric field strength up to 100 kV/m in a low pressure gas, the effects are observed such as the formation of non-uniform and essentially non-stationary glow, nonlinear absorption and dispersion transformation of the shape of high-power pulses, due to gas ionization in the EMP field.

“Superlight” Propagation of Electromagnetic Pulses in a Resonant-Absorbing Gas Medium

“Superlight” Propagation of Electromagnetic Pulses in a Resonant-Absorbing Gas Medium

Slowing down light in a qubit metamaterial

The rapid progress in quantum information processing leads to a rising demand for devices to control the propagation of electromagnetic wave pulses and to ultimately realize universal and efficient quantum memory. While in recent years, significant progress has been made to realize slow light and quantum memories with atoms at optical frequencies, superconducting circuits in the microwave domain still lack such devices. Here, we demonstrate slowing down electromagnetic waves in a superconducting metamaterial composed of eight qubits coupled to a common waveguide, forming a waveguide quantum electrodynamics system. We analyze two complementary approaches, one relying on dressed states of the Autler–Townes splitting and the other based on a tailored dispersion profile using the qubits tunability. Our time-resolved experiments show reduced group velocities of down to a factor of about 1500 smaller than in vacuum. Depending on the method used, the speed of light can be controlled with an additional microwave tone or an effective qubit detuning. Our findings demonstrate high flexibility of superconducting circuits to realize custom band structures and open the door to microwave dispersion engineering in the quantum regime.

High-current space-charge-limited pulses using ultrashort laser pulses.

The maximum current that can be delivered by a 1-D vacuum diode is limited due to the space-charge reduction of the accelerating field. For a steady-state operation, this is given by the Child-Langmuir space-charge limit. However, for pulsed diode sources, the instantaneous current can be much higher than this limit, as long as the pulse length is much less than the transit time across the diode gap. This enables the generation of high current pulses with pulse durations of the order of tens of picoseconds using photocathodes driven by ultrashort laser pulses. The generation of such short and powerful electromagnetic pulses is important for numerous applications such as ultrawideband radar or as photocathode sources for accelerators. In this work, the limiting current pulse is investigated in the case of a very short, square-top initial pulse and it is found that these pulses propagate in a self-similar manner, remaining as a square-top charge cloud in space throughout their acceleration and propagation. The resultant current and pulse duration turn out to be dependent on only three parameters, which are the applied voltage, the vacuum transit time, and the fraction of the saturation charge density in the initial charge cloud. The resultant scaling of the resultant peak current and pulse duration are calculated numerically as a function of starting sheet-charge density, allowing the calculation of the resultant pulses for any ultrashort, pulse-driven vacuum photodiode design.