scholarly journals Modification of relativistic beam fields under the influence of external conducting and ferromagnetic flat boundaries

2020 ◽  
Vol 2020 (1) ◽  
Author(s):  
B B Levchenko
Keyword(s):  
Electric Fields ◽  
Particle Density ◽  
Lorentz Factor ◽  
Historical Background ◽  
External Fields ◽  
Relativistic Limit ◽  
Elliptical Cross ◽  
Flat Surfaces ◽  
Exact Summation ◽  
Analytical Expressions

Abstract We derive analytical expressions for external fields of a relativistic bunch of charged particles with a circular and an elliptical cross section under different boundary conditions and interaction of the fields with an accelerator structural elements. The particle density in the bunch is assumed to be uniform as well as non-uniform. At distances far apart from the bunch, in free space the field reduces to the relativistic modified Coulomb form for a pointlike charge and at small distances the expressions reproduce the external fields of a continuous beam. In an ultra-relativistic limit the longitudinal components of the internal and external electric fields of the bunch are strongly suppressed by the Lorentz factor. If the bunch is surrounded by conducting surfaces, the bunch self-fields are modified. Image fields generated by a bunch between two parallel conducting plates are studied in detail. Exact summation of the electric, $E_y$, and magnetic, $B_x$, image field components allows the infinite series to be represented in terms of elementary trigonometric functions. The new expressions for modified fields are applied to study image forces acting on the bunch constituents and the bunch as a whole. The coherent and incoherent tune shifts for an arbitrary bunch displacement from the midplane are calculated in the framework of an improved linear theory, for both infinite and finite parallel flat surfaces. Moreover, the developed method allows us to generalize the Laslett image coefficients $\epsilon_1$, $\epsilon_2$, $\xi_1$, $\xi_2$ to the case of an arbitrary bunch offset and reveal relationships between these coefficients. Appendix C provides a brief historical background of the development of the method of electrical images.

Revisiting Local Electric Fields on Close-Packed Metal Surfaces: Theory Versus Experiments

2007 ◽  
Vol 128 ◽  
pp. 219-224 ◽  
Author(s):  
P.P. Kostrobiy ◽  
Bogdan M. Markovych ◽  
Yuri Suchorski
Keyword(s):  
Electron Density ◽  
Electric Fields ◽  
Metal Surfaces ◽  
Integration Method ◽  
Functional Integration ◽  
Correlation Effects ◽  
Flat Surfaces ◽  
Exchange Correlation ◽  
Density Distributions ◽  
Theory Versus

An external electrostatic field of the order of a few tens of a volt per nanometer causes significant changes in the electron density distribution near a metal surface. Because of differing electronic distributions and varying responses of electrons to the applied field for various metals, the resulting local field distribution in the close vicinity of the surface should depend on the electronic properties of the particular metal, even for flat surfaces. Field-free and field-modified electron density distributions for different metal surfaces were calculated using the functional integration method. This approach enables the exchange-correlation effects to be correctly considered and makes it possible to account for the proper field-effect for broad field ranges without using the perturbation theory. The results of calculations are compared with the field-ion microscopic observations.

scholarly journals Climbing droplets driven by mechanowetting on transverse waves

2019 ◽  
Vol 5 (6) ◽  
pp. eaaw0914 ◽  
Author(s):  
Edwin De Jong ◽  
Ye Wang ◽  
Jaap M. J. Den Toonder ◽  
Patrick R. Onck
Keyword(s):  
Electric Fields ◽  
Digital Microfluidics ◽  
Modern Technology ◽  
Dynamic Surface ◽  
Transverse Waves ◽  
Flat Surfaces ◽  
Inclined Surfaces ◽  
Fluid Properties ◽  
High Electric Fields ◽  
New Applications

Many applications in modern technology, such as self-cleaning surfaces and digital microfluidics, require control over individual fluid droplets on flat surfaces. Existing techniques may suffer from side effects resulting from high electric fields and high temperatures. Here, we introduce a markedly different method, termed “mechanowetting,” that is based on the surface tension–controlled droplet motion on deforming surfaces. The method is demonstrated by transporting droplets using transverse surface waves on horizontal and (vertically) inclined surfaces at transport velocities equal to the wave speed. We fully capture the fundamental mechanism of the mechanowetting force numerically and theoretically and establish its dependence on the fluid properties, surface energy, and wave parameters. Mechanowetting has the potential to lead to a range of new applications that feature droplet control through dynamic surface deformations.

scholarly journals Interaction of a Screw Dislocation with Interface and Wedge-Shaped Cracks in One-Dimensional Hexagonal Piezoelectric Quasicrystals Bimaterial

2019 ◽  
Vol 2019 ◽  
pp. 1-7
Author(s):  
Lian he Li ◽  
Yue Zhao
Keyword(s):  
Screw Dislocation ◽  
Electric Fields ◽  
Electric Displacement ◽  
Image Force ◽  
Coupling Constants ◽  
Geometrical Parameters ◽  
Intensity Factors ◽  
One Dimensional ◽  
Special Cases ◽  
Analytical Expressions

Interaction of a screw dislocation with wedge-shaped cracks in one-dimensional hexagonal piezoelectric quasicrystals bimaterial is considered. The general solutions of the elastic and electric fields are derived by complex variable method. Then the analytical expressions for the phonon stresses, phason stresses, and electric displacements are given. The stresses and electric displacement intensity factors of the cracks are also calculated, as well as the force on dislocation. The effects of the coupling constants, the geometrical parameters of cracks, and the dislocation location on stresses intensity factors and image force are shown graphically. The distribution characteristics with regard to the phonon stresses, phason stresses, and electric displacements are discussed in detail. The solutions of several special cases are obtained as the results of the present conclusion.

The study of the plasmon modes of square atomic clusters based on the eigen-oscillation equation of charge under the free-electron gas model

2018 ◽  
Vol 32 (11) ◽  
pp. 1850139 ◽  
Author(s):  
Hong-Jie Xue ◽  
Reng-Lai Wu ◽  
Cheng-Xi Hu ◽  
Ming Zhang
Keyword(s):  
Electric Fields ◽  
Free Electron ◽  
Electron Gas ◽  
Plasmon Mode ◽  
Atomic Clusters ◽  
Equation Method ◽  
Electron Systems ◽  
External Fields ◽  
Oscillation Equation ◽  
Plasmon Modes

In atomic clusters, plasmon modes are generally gained by the resonant responses for external fields. However, these resonant methods still carry some defects: some plasmon modes may not have been found as that may not have been excited by the external fields. Recently, by employing the extended Hubbard model to describe electron systems of atomic clusters, we have presented the eigen-oscillation equation of charge to study plasmon modes. In this work, based on the free-electron gas model, we further explore the eigen-equation method. Under different external electric fields, some of the plasmon mode spectrums with obvious differences are found, which display the defects of the resonant methods. All the plasmon modes obtained by the resonant methods are predicted by the eigen-equation method. This effectively shows that the eigen-equation method is feasible and reliable in the process of finding plasmon. In addition, various kinds of plasmons are displayed by charge distributions, and the evolution features of plasmon with system parameters are gained by the energy absorption spectrum.

scholarly journals Accelerated self-constricted electron streams in plasma

1959 ◽  
Vol 249 (1258) ◽  
pp. 318-334 ◽  
Keyword(s):  
Electric Fields ◽  
Numerical Solutions ◽  
Fluid Model ◽  
Electron Flow ◽  
Electron Stream ◽  
Ion Collisions ◽  
Two Fluid Model ◽  
Analytical Expressions ◽  
Positive Ion ◽  
Two Fluid

The mechanism is described of radial oscillations in a neutralized cylindrical electron stream in an accelerating electric field. The analysis is based on the two-fluid model of plasma. Analytical expressions for small amplitude oscillations and numerical solutions for large amplitudes are derived. It is found, when electron-positive ion collisions are taken into account, that for dense streams in low electric fields the radial oscillations (pinch oscillations) can destroy the streaming character of the electron flow and thus prevent its acceleration.

scholarly journals Dipolophoresis and Travelling-Wave Dipolophoresis of Metal Microparticles

Micromachines ◽  
2020 ◽  
Vol 11 (3) ◽  
pp. 259
Author(s):  
Jose Eladio Flores-Mena ◽  
Pablo García-Sánchez ◽  
Antonio Ramos
Keyword(s):  
Electric Fields ◽  
Particle Motion ◽  
Numerical Solutions ◽  
Particle Surface ◽  
Travelling Wave ◽  
Aqueous Electrolytes ◽  
Small Particles ◽  
Ac Electric Fields ◽  
Induced Charge ◽  
Analytical Expressions

We study theoretically and numerically the electrokinetic behavior of metal microparticles immersed in aqueous electrolytes. We consider small particles subjected to non-homogeneous ac electric fields and we describe their motion as arising from the combination of electrical forces (dielectrophoresis) and the electroosmotic flows on the particle surface (induced-charge electrophoresis). The net particle motion is known as dipolophoresis. We also study the particle motion induced by travelling electric fields. We find analytical expressions for the dielectrophoresis and induced-charge electrophoresis of metal spheres and we compare them with numerical solutions. This validates our numerical method, which we also use to study the dipolophoresis of metal cylinders.

scholarly journals Impact of an off-centred dipole on neutron star binaries

2019 ◽  
Vol 488 (3) ◽  
pp. 4161-4168
Author(s):  
J Pétri
Keyword(s):  
Neutron Star ◽  
Electric Fields ◽  
Distribution Functions ◽  
Compact Objects ◽  
Binary Neutron Star ◽  
Analytical Approximations ◽  
Binary Formation ◽  
Sizeable Fraction ◽  
Pseudo Spectral ◽  
Analytical Expressions

ABSTRACT Neutron stars are strongly magnetized rotating compact objects. Therefore, they also produce huge electric fields accelerating particles to ultrarelativistic energies. The simplest magnetic topology is a dipole traditionally located at the stellar centre. In this paper, we re-investigate the consequences of an off-centred rotating magnetic dipole, showing accurate magnetic field line geometries, the associated spin-down luminosity as well as the corresponding electromagnetic kick and torque imprinted to the neutron star. Results are obtained by time-dependent numerical simulations of Maxwell equations in vacuum using pseudo-spectral methods. We compare our results to known analytical expressions available to lowest order in the parameter ϵ = d/R, where d is the displacement of the dipole from the stellar centre and R the neutron star radius. We found good agreement between our numerical computations and our analytical approximations even for well off-centred dipoles having large displacements with a sizeable fraction of the radius, i.e. ϵ ≲ 1. An explanation for binary neutron star eccentricity distribution functions is given with an emphasize on highly eccentric systems as an alternative scenario to traditional binary formation.

scholarly journals Electric and Magnetic Fields Generated by a Charged Bunch between Parallel Conducting Plates

2010 ◽  
Vol 2010 ◽  
pp. 1-5 ◽  
Author(s):  
B. Levchenko
Keyword(s):  
Magnetic Fields ◽  
Cross Section ◽  
Infinite Series ◽  
Direct Method ◽  
Charged Particles ◽  
Circular Cross Section ◽  
External Fields ◽  
Trigonometric Functions ◽  
Electric And Magnetic Fields ◽  
Analytical Expressions

Image fields generated by a bunch of charged particles between two parallel perfectly conducting plates are studied in detail. We derive exact analytical expressions for external fields of a charged relativistic bunch with a circular cross-section. Summation of image fields by the direct method invented by Laslett allows the infinite series to be represented in terms of elementary trigonometric functions.

Competitive Guidance Cues Affect Fibroblast Cell Alignment: Electric Fields vs. Contact Guidance

2004 ◽  
Vol 845 ◽  
Author(s):  
Iain R. Gibson ◽  
Colin D. McCaig
Keyword(s):  
Electric Fields ◽  
Fibroblast Cell ◽  
Groove Depth ◽  
Fibroblast Cells ◽  
Cell Alignment ◽  
Flat Surfaces ◽  
Guidance Cues ◽  
Guidance Cue ◽  
Mixed Response ◽  
Field Strengths

ABSTRACTWhen bovine ligament fibroblast cells were cultured on parallel micro-grooved surfaces, they aligned their long axes parallel to the groove direction. This alignment was dependent on the groove depth, with increasing groove depth increasing guided cell alignment. When cells were cultured in a physiological dc electric field (EF) on non-grooved, flat surfaces, the cells aligned in response to the EF, with their long axes perpendicular to the EF vector. This response was EF strength dependent, increasing EF strength (from 20 to 200mV/mm) increased cell alignment, perpendicular to the EF vector. These two guidance cues were applied simultaneously, so that the EF vector was parallel to the groove direction. At high but still physiological EF strengths (200mV/mm) cells ignored the topography and were guided by the EF alone, aligning perpendicular to the EF vector, as on non-grooved surfaces. At low field strengths (20mV/mm) cells responded only to the topographic guidance cue, with cells aligning parallel to the grooves and therefore also to the EF vector. Intermediate field strengths (50 to 100mV/mm) produced a mixed response, with cells responding to both guidance cues. The effect of removing serum from the culture medium on the EF and topographical guidance of fibroblast cells was studied and the results were compared to cells on non-grooved surfaces. Removal of serum produced a small but significant decrease in the angle of cell alignment for cells on non-grooved surfaces, from 78 to 63 degrees, relative to the EF vector, but did not completely suppress the EF guidance cue. In contrast, the EF guidance of cells on grooved substrates was suppressed almost completely by the absence of serum, with cells responding only to the grooved topography, aligning their long axis parallel to the grooves and the EF vector. These results imply that alignment of fibroblasts by topography is serum-independent, but alignment by EFs is serum-dependent. In addition they demonstrate that the alignment of fibroblast cells can be tailored by the dual guidance cues of topography and electric fields.

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