Journal articles on the topic 'Electrodynamic focusing'

Self-focusing of laser beams in plasma is studied analytically using the thermal (collision produced) and ponderomotive (nonlinear force produced) effects based on the model of Zakharov with solutions of the nonlinear Schrödinger equation. A basic difference appears if the electric field amplitude E is less than the threshold Eth (at which the electrodynamic energy density is equal to the gasdynamic pressure) from the contrary case, E > Eth.The length of the filamentation process is evaluated and results in large values for E below Eth.

Two types of electrodynamic forming process have been developed: electromagnetic and electrohydraulic forming. In the case of electromagnetic forming, the energy stored in a capacitor bank is discharged through a coil, which means that the electrical interaction between the coil and the plate or a tubular part to be formed results in deformation of the workpiece. However, in the case of electrohydraulic forming, the capacitor bank is discharged through a spark gap or filament wire; the deformation of the workpiece is due to the shockwaves, generated by the discharge process in a transmitting medium. In both processes, a large amount of energy is released in extremely short time, therefore these processes are considered to be high energy rate forming processes. These high energy rates, result in increasing the formability of the materials in many cases, and obtain significant deformations also for some materials that normally do not behave plastically. The utilization of the energy stored in the capacitor bank is significantly better in the case of electrohydraulic forming, because the released energy is converted directly to pressure waves, results in forming of higher strength materials. Both metallic and non-metallic materials can be formed by the technologies of electromagnetic and electrohydraulic technologies. In the present paper some aspects and applications of these high energy rate methods are briefly outlined mainly focusing on the automotive industry, involving expansion or compression forming of tubular parts, joining and assembly operations.

The energy harvesting became more popular as the need for small energy sources was growing. Among different types of energy harvesting (electromagnetic, piezoelectric, magnetostrictive, light, heat) the first one is the oldest and still popular. The common studies focused on optimizing the electro-mechanical design. This paper is focusing on the study of the electric circuit, with the main goal of finding some optimum rules. The results could be used for designing the coil of the sensor and the external electrical circuit.

One of the main trends in microwave electronics is the ultra-large power production. The electron stream energy is converted inside vacuum systems, where the key moment is increasing output power of microwave devices, which is possible only when using more and more powerful electron streams. Increasing electron stream power is possible due to either enhancing the carried currents or as a result of increasing the electron energy. Given the law that connects currents and voltages in electronic systems operating when the current is limited by a spatial charge, the production of ultra-high-power electron flows is associated with the usage of relativistic velocity electrons, i. e. approaching the light speed. Likewise, at present, relativistic electrovacuum devices (traveling-wave lamps and backward-wave lamps) use magnetic focusing for linear relativistic streams, which prevents the implementation of simple superconducting electrodynamic systems, because highfrequency metal superconductivity disappears in constant magnetic fields. Meanwhile, simplified ultra-highpower superconducting device structures can significantly increase the device energy due to the strong ohmic loss reduction, which just limits the device energy, destroying the working electrodynamic system surface by increasing power or pulse duration of the generator. The article outlines the modernized design of a new-type microwave generator – the relativistic helitron. The paper considers a simpler coaxial resonator design, obtained by using the supercritical narrowing of the inner conductor radius by the Hn1l mode of the electromagnetic field, rather than a coaxial resonator with notch filters.

Resonance energy transfer is the primary mechanism for the migration of electronic excitation in the condensed phase. Well-known in the particular context of molecular photochemistry, it is a phenomenon whose much wider prevalence in both natural and synthetic materials has only slowly been appreciated, and for which the fundamental theory and understanding have witnessed major advances in recent years. With the growing to maturity of a robust theoretical foundation, the latest developments have led to a more complete and thorough identification of key principles. The present review first describes the context and general features of energy transfer, then focusing on its electrodynamic, optical, and photophysical characteristics. The particular role the mechanism plays in photosynthetic materials and synthetic analogue polymers is then discussed, followed by a summary of its primarily biological structure determination applications. Lastly, several possible methods are described, by the means of which all-optical switching might be effected through the control and application of resonance energy transfer in suitably fabricated nanostructures.Key words: FRET, Förster energy transfer, photophysics, fluorescence, laser.

We summarize the nuclear physics interests in the Oklo natural nuclear reactors, focusing particularly on developments over the past two decades. Modeling of the reactors has become increasingly sophisticated, employing Monte Carlo simulations with realistic geometries and materials that can generate both the thermal and epithermal fractions. The water content and the temperatures of the reactors have been uncertain parameters. We discuss recent work pointing to lower temperatures than earlier assumed. Nuclear cross-sections are input to all Oklo modeling and we discuss a parameter, the 175 Lu ground state cross-section for thermal neutron capture leading to the isomer 176 m Lu , that warrants further investigation. Studies of the time dependence of dimensionless fundamental constants have been a driver for much of the recent work on Oklo. We critically review neutron resonance energy shifts and their dependence on the fine structure constant α and the ratio Xq = mq/Λ (where mq is the average of the u and d current quark masses and Λ is the mass scale of quantum chromodynamics (QCD)). We suggest a formula for the combined sensitivity to α and Xq that exhibits the dependence on proton number Z and mass number A, potentially allowing quantum electrodynamic (QED) and QCD effects to be disentangled if a broader range of isotopic abundance data becomes available.

The Dirac delta function is a concept that is useful throughout physics as a standard mathematical tool that appears repeatedly in the undergraduate physics curriculum including electrodynamics, optics, and quantum mechanics. Our analysis was guided by an analytical framework focusing on how students activate, construct, execute, and reflect on the Dirac delta function in the context of classical electrodynamics problems solving. It’s applications in solving the charge density associated with a point charge as well as electrostatic point dipole field, for more advanced situations to describe the charge density of hydrogen atom were presented.

AbstractFollowing the initial success of cavity quantum electrodynamics in atomic systems, strong coupling between light and matter excitations is now achieved in several solid-state set-ups. In those systems, the possibility to engineer quantum emitters and resonators with very different characteristics has allowed access to novel nonlinear and non-perturbative phenomena of both fundamental and applied interest. In this article, we will review some advances in the field of solid-state cavity quantum electrodynamics, focussing on the scaling of the relevant figures of merit in the transition from microcavities to sub-wavelength confinement.

An influence of the rotation and gravity of the Earth on the particle motion and the spin evolution is not negligible and it should be taken into account in spin physics experiments. The Earth rotation brings the Coriolis and centrifugal forces in the lab frame and also manifests in the additional rotation of the spin and in the change of the Maxwell electrodynamics. The change of the Maxwell electrodynamics due to the Earth gravity is much smaller and can be neglected. One of manifestations of the Earth rotation is the Sagnac effect. The electric and magnetic fields acting on the spin in the Earth’s rotating frame coincide with the corresponding fields determined in the inertial frame instantly accompanying a lab. The effective electric field governing the particle motion differs from the electric field in the instantly accompanying frame. Nevertheless, the difference between the conventional Lorentz force and the actual force in the Earth’s rotating frame vanishes on average in accelerators and storage rings due to the beam rotation. The Earth gravity manifests in additional forces acting on particles/nuclei and in additional torques acting on the spin. The additional forces are the Newton-like force and the reaction force provided by a focusing system. The additional torques are caused by the corresponding focusing field and by the geodetic effect. As a result, the Earth gravity leads to the additional spin rotation about the radial axis which may not be negligible in EDM experiments.

Вода является основной компонентой в организме человека, определяющей гемодинамику. В процессе движения воды наблюдается генерация заряда, обусловленная её электрокинетическими свойствами. В работе исследована временная зависимость генерации и аккумуляции заряда в воде, движущейся по проточной системе. Показано, что при определенных условиях, временная зависимость аккумуляции заряда имеет нелинейный характер - наблюдается скачкообразное изменение регистрируемой величины (эффект электрогидродинамического барьера стекания заряда, ЭБСЗ). Появление этих скачков зависит от расстояния (l) между срезом наконечника подающей трубки проточной системы и электродом заземления, вставленным в эту трубку. Эффект наблюдается при расстоянии l~10 см и более. Этот эффект должен учитываться в фундаментальных исследованиях свойств воды, а также при разработке моделей, описывающих гемодинамику в организме в норме и патологии. Кроме того, полученные результаты следует использовать при разработке высокочувствительных аналитических систем, таких, как нанопроводные, на основе атомно-силового микроскопа (АСМ) и других диагностических систем, предназначенных для повышения эффективности раннего выявления патологического процесса. Цель исследования: мониторинг генерации и аккумуляции электрического заряда при движении воды как компоненты организма и основы растворов, используемых в аналитических системах. Методика. Исследован процесс генерации и аккумуляции заряда в воде при ее движении в проточной системе. В качестве такой системы использовалась проточная часть АСМ-фишинг системы, с помощью которой показана возможность высокой концентрационной чувствительности анализа при обнаружении белковых маркеров заболеваний. Измерения величины электрического заряда проводились с помощью электрометра, включенного в проточную систему подачи образца системы АСМ-фишинга [1, 2]. Основные элементы системы подачи - перистальтический насос, трубка для подачи воды, полипропиленовый наконечник к трубке и измерительная ячейка. К измерительной ячейке подключен электрометр, разработанный в ИБМХ. В процессе измерений деионизованная вода непрерывно подавалась в ячейку с помощью насоса. Скорость потока (~15 мкл/с) подобрана таким образом, чтобы на наконечнике (внутренний диаметр 0,4 мм) подающей трубки формировались капли. Для поддержания постоянного потенциала в резервуаре с исходной водой, в подающую трубку вставлен электрод заземления. Расстояние от электрода до среза наконечника трубки (l) варьировалось и составляло 5, 10 или 15 см. Эксперименты проводились при t = 35°C и влажности 49%. Результаты: показано, что в фишинг-системе, после прохождения деионизованной воды по подающей трубке этой системы, генерируется электрический заряд, который регистрируется при поступлении воды в измерительную ячейку. По результатам измерений наблюдается аккумуляция заряда. При постоянной скорости подачи воды наблюдается как линейное увеличение величины заряда в измерительной ячейке, так и скачкообразное. Появление этого эффекта зависит от расстояния между наконечником и электродом заземления в подающей трубке - эффект обнаруживается при величине этого расстояния, l~10 см и более. Обнаруженная скачкообразная зависимость названа эффектом электрогидродинамического барьера стекания заряда (ЭБСЗ). Заключение. Обнаружено, что при движении воды в проточной системе, в процессе её непрерывной подачи, в измерительной ячейке накапливается заряд, поступающий с водой из наконечника подающей трубки. Установлена линейно-скачкообразная зависимость накопления заряда в ячейке (эффект ЭБСЗ). Величина скачка накопленного заряда (порядка нескольких нКл) зависит от расстояния между наконечником и электродом заземления, вставленного в подающую трубку. Этот эффект должен учитываться при проведении фундаментальных исследований, посвященных изучению физико-химических свойств воды, а также при создании уточненных моделей, описывающих гемодинамику в организме в норме и патологии. Кроме того, полученные результаты следует использовать при разработке высокочувствительных диагностических систем на основе молекулярных детекторов, включающих проточный способ подачи образца, и предназначенных для повышения эффективности раннего выявления патологического процесса. Water is the main component of the human body, which determines hemodynamics. Electrokinetic properties of moving water provide generation of a charge. This work focuses on time dependence of charge generation and accumulation in water passing through a flow-based system. It was shown that under certain conditions, the time dependence of charge accumulation was nonlinear; the recorded value changed in a stepwise manner (effect of electrodynamic barrier for the charge run-off, EBCRO). Emergence of these stepwise changes depends on the distance between the tip of the input pipe and the ground electrode inserted in this pipe. This effect was observed at a distance of l~10 cm and more. The discovered effect should be taken into account in developing flow-based, highly sensitive analytic systems, such as nanowire, atomic-force microscope (AFM) based, and other systems designed to improve early detection of pathological processes. Aim: To monitor electric charge generation and accumulation in moving water as a main component of the body and a vehicle of solutions used in analytical systems. Methods: The process of charge generation and accumulation was studied in water during its motion in a flow system. In the experiments, the flow-based part of an AFM-based fishing system was used since this system provides a high concentration sensitivity in detecting protein markers of diseases. Electric charge values were measured using an electrometer incorporated in the flow system that feeds samples into the AFM-fishing system. The major elements of the sample feeding system included a peristaltic pump, a pipe for sample delivery from a tapered tip, and a measuring cell connected to an electrometer developed at the Institute of Biomedical Chemistry. During the measurements, deionized water was continuously pumped into the cell. The flow rate (~15 mL/s) was selected so that drops form on the tip nozzle (inner diameter, 0.4 mm) of the inlet pipe. To maintain a constant potential in the stock solution, a ground electrode was inserted into the inlet pipe. The distance between the electrode inside the pipe and the tip varied and was 5, 10, or 15 cm. Experiments were conducted at t = 35°C and 49% humidity. Results. In the fishing system, after the deionized water has passed through the feeding pipe of this system through the tip, an electric charge is generated and recorded when the water enters the measuring cell. According to results of measurements charge accumulation is observed. At a constant rate of water supply, accumulation of the charge in the measuring cell can be either linear or stepwise. Emergence of this effect depends on the distance between the tip and the ground electrode in the input pipe: the effect was detected at a distance of l~10 cm and more. The discovered stepwise dependence was named the effect of electrodynamic barrier for the charge run-off (EBCRO). Conclusion. In the process of water motion during its continuous pumping through the flow-based system, a charge accumulates in the measuring cell; this charge is delivered with the water from the tip of the feeding pipe. A linear-stepwise dependence of charge accumulation in the cell (EBCRO effect) is determined. Magnitude of the stepwise change in this charge (approximately several nC) depends on the distance between the tip and the ground electrode inserted into the inlet pipe. This effect should be taken into account in both basic research focusing on physicochemical properties of water and applied research focusing on development of the models describing hemodynamics in the body. In addition, the obtained results might be used in developing highly sensitive diagnostic systems, such as nanowire, AFM-based, and other fishing systems to enhance early detection of pathological process.

Our aim in this review paper is to present the applications of Connes' noncommutative geometry to elementary particle physics. Whereas the existing literature is mostly focused on a mathematical audience, in this paper we introduce the ideas and concepts from noncommutative geometry using physicists' terminology, gearing towards the predictions that can be derived from the noncommutative description. Focusing on a light package of noncommutative geometry (so-called "almost-commutative manifolds"), we shall introduce in steps: electrodynamics, the electroweak model, culminating in the full Standard Model. We hope that our approach helps in understanding the role noncommutative geometry could play in describing particle physics models, eventually unifying them with Einstein's (geometrical) theory of gravity.

A synthesis of the present knowledge on gamma-ray emission from the magnetosphere of a rapidly rotating neutron star is presented, focusing on the electrodynamics of particle accelerators. The combined curvature, synchrotron, and inverse-Compton emission from ultra-relativistic positrons and electrons, which are created by two-photon and/or one-photon pair creation processes, or emitted from the neutron-star surface, provide us with essential information on the properties of the accelerator — electric potential drop along the magnetic field lines. A new accelerator model, which is a mixture of traditional inner gap and outer gap models, is also proposed, by solving the Poisson equation for the electrostatic potential together with the Boltzmann equations for particles and gamma-rays in the two-dimensional configuration and two-dimensional momentum spaces.

Symmetry principles of several distinct kinds are revealingly engaged in an analysis focussing on third harmonic scattering, a current focus of research on nonlinear optics in chiral media. Analysis in terms of irreducible Cartesian tensors elucidates the detailed electrodynamical origin and character of the corresponding material properties. Considerations of fundamental charge, parity and time reversal (CPT) symmetry reveal the conditions for an interplay of transition multipoles to elicit a chiral response using circularly polarised pump radiation, and the symmetry of quantised angular momentum underpins the associated selection rules and angular distribution. The intrinsic structural symmetry of chiral scatterers determines their capacity to exhibit differential response. Exploiting permutational index symmetry in the response tensors enables quantitative assessment of the boundary values for experimentally measurable properties, including circular intensity differentials.

Consideration of the many observed types of jets on scales ranging from parsecs to megaparsecs seen in radio, optical, infrared and X-ray wavebands with a variety of morphologies both in galactic and extragalactic systems leads to some constraints on their fundamental nature. Jet formation is introduced with the concept of the Laval nozzle and related points include the problem of maintaining the nozzle, Mach disk effects due to under and over-expansion and the potential importance of magnetic confinement and focussing. Current ideas on jet formation at the black hole and accretion disk are given with emphasis on the plasma physics associated with black-hole electrodynamics, thermal and magnetically driven winds and thick disks. Stability of jet propagation is reviewed with emphasis on magnetised and unmagnetised Kelvin-Helmholtz instabilities and the various dominant modes. The particle acceleration physics of shocks, wave-particle interactions and turbulence is summarised while noting some outstanding plasma physics problems. Jet equilibrium associated with the non-linear saturation of instabilities, the formation of cocoons, shock stabilisation and magnetic fields is discussed. Detailed plasma physics studies that could significantly clarify jet physics are indicated.

The ionosphere and thermosphere (IT) constitutes a coupled, complex and dynamical electromagnetic and photochemical system, which is sensitive to a combination of external factors: particle precipitation and electrical currents from the Earth's magnetosphere and incoming solar radiation produce dramatic effects in the IT and significantly alter its energetics, dynamics and chemistry in a way that is not well understood. This sensitivity of the IT to external factors results in large, yet often unpredictable changes in many of the variables in the IT, such as in its density, temperature, neutral and ion winds, total electron content, neutral and ion composition, electric fields, currents and conductivities. External forcing of the IT system varies over different time-scales, such as solar cycle (11-year), inter-annual (e.g. quasi-biennial), seasonal and diurnal; on top of these, geomagnetic disturbances caused by solar storms and substorms can lead to abrupt reconfigurations of the magnetospheric field-aligned and horizontal currents, setting a number of electrodynamics processes in motion. The overlapping physical and chemical phenomena occur at a range of temporal and spatial scales that are highly difficult to understand as a whole. The importance of the behaviour of this region to multiple issues related to aerospace technology, such as orbital calculations, vehicle re-entry, space debris lifetime, etc., and its potential threats to modern, technology-dependent society via geomagnetically induced currents and ionospheric scintillation of Global Navigation Satellite System signals, dictate that a more detailed understanding and accurate modelling are urgently needed. In this paper, we review the status of characterization and some of the key open issues and challenges of the IT, focusing on measurement gaps in this region as well as areas of largest discrepancies between models and data.This article is part of the theme issue ‘Solar eruptions and their space weather impact’.

Modern liquid-fuel rocket propulsion harbors a number of great limitations. Among those is the weight of fuel, which makes up more than 90% of the mass of the SpaceX Falcon 9 (NASA, 2018). Electric propulsion has been used for decades as an alternative to liquid-fuel rockets due to low propellant requirements and high specific impulse. Although electric thrusters have strictly been used in non-atmospheric conditions, recent innovations attempt to expand its use to airspace. This quasi-experimental study focuses on the creation of an air-breathing magnetoplasmadynamic (MPD) thruster, with attempts being made to maximize the efficiency of the engine. Immense safety concerns prevented testing from occurring after the engine was built. However, the estimated performance of the built MPD is compared to a multitude of existing forms of electric propulsion, from Hall-effect thrusters to electrodynamic tethers. The concluding evidence suggests that air-breathing MPDs are not currently viable, high-power photon thrusters being of greater use in atmospheric conditions. Further research focusing on decreasing atmospheric breakdown voltage and increasing mirror reflectance of photon thrusters is suggested.

Numerical simulations of stationary fluorescence spectra of molecular systems usually rely on the relation between the photon emission rate and the system’s dipole–dipole correlation function. However, research papers usually take this relation for granted, and standard textbook expositions of the theory of fluorescence spectra also tend to leave out this important relation. In order to help researchers with less theoretical training gain a deeper understanding of the emission process, we perform a step-by-step derivation of the expression for the fluorescence spectrum, focusing on rigorous mathematical treatment and the underlying physical content. Right from the start, we employ quantum description of the electromagnetic field, which provides a clear picture of emission that goes beyond the phenomenological treatment in terms of the Einstein A coefficient. Having obtained the final expression, we discuss the relation of the latter to the present level of theory by studying a simple two-level system. From the technical perspective, the present work also aims at familiarizing the reader with the density matrix formalism and with the application of the double-sided Feynman diagrams.

The predictions of mean-field electrodynamics can now be probed using direct numerical simulations of random flows and magnetic fields. When modelling astrophysical magnetohydrodynamics, it is important to verify that such simulations are in agreement with observations. One of the main challenges in this area is to identify robust quantitative measures to compare structures found in simulations with those inferred from astrophysical observations. A similar challenge is to compare quantitatively results from different simulations. Topological data analysis offers a range of techniques, including the Betti numbers and persistence diagrams, that can be used to facilitate such a comparison. After describing these tools, we first apply them to synthetic random fields and demonstrate that, when the data are standardized in a straightforward manner, some topological measures are insensitive to either large-scale trends or the resolution of the data. Focusing upon one particular astrophysical example, we apply topological data analysis to H iobservations of the turbulent interstellar medium (ISM) in the Milky Way and to recent magnetohydrodynamic simulations of the random, strongly compressible ISM. We stress that these topological techniques are generic and could be applied to any complex, multi-dimensional random field.

AbstractThe Poynting vector plays a key role in electrodynamics as it is directly related to the power and the momentum carried by an electromagnetic wave. Based on the Lorenz-Mie theory, we report on the focusing effect of a spherical particle-lens by properly analysing the Poynting vector maps. Conventional two-dimensional (2D) maps showing Poynting vector magnitude and direction in a given plane cannot deliver information on three-dimensional (3D) directivity and vectorisation in key regions of singularities, such as vortexes and saddle points, due to poor expressiveness. In this article, an analytical 3D mapping technology is utilised to track the field-features passing through the singularities of the distribution of the Poynting vector in a spherically dielectric mesoscale particle-lens. We discovered that the spheres with the certain size parameters can stimulate extremely large field-intensity at singularities and then form two circular hotspots around the sphere poles. An astonishing large ‘heart-shape’ 3D Poynting vector circulation, which cannot be predicted by conventional 2D mapping analysis, is found to provide a great angular variation within an enormous range in these spheres. We anticipate that this effect will contribute to the field-enhancement phenomena, such as surface enhances Raman scattering, surface enhances absorption, super-resolution imaging and others.