The presented study deals with the influence of the contacts materials on the evolution of the arc in low voltage circuit breakers. The commutation from the mobile contact onto the electrode is especially investigated in order to improve the breaking device performances. Hence, to preserve the qualities of the contact, the arc must leave this area as soon as possible. To undertake this study, several diagnostics are implemented. A measuring device is composed of magnetic induction sensors located outside the chamber. It allows the determination of the position and the volume of the arc during the breaking. Optical (ultra-speed camera) and electrical measurements are also performed with the technical support of Schneider Electric. Different current values (assumed peak current of 3 kA, 8 kA and 12 kA) and different natures of materials composing the electrical contacts have been tested. Copper contacts, different contacts on silver base obtained with different processes have been used. Experimental results show the influence of these various parameters on the arc volume and on the transfer of the arc towards the quenching chamber. Indeed, different dynamic behaviors are observed during the current transfer phase.

The formation of intermetallic compounds (IMC) and its effects at the interface between different metals has always been of interest for the electronics industry, contacts manufacturers and users. The purpose of this work is primarily to develop an in situ technique of thermally aging metallic samples within the vacuum chamber of a scanning electron microscope (SEM). This setup enables ongoing observation of the formation and growth of intermetallic compounds within the chamber. Due to the amount of data available in literature, copper-tin specimens were chosen as a basis to validate the technique. Once the samples were thermally aged, energy dispersive X-ray (EDX) analyses as well as electron backscattered diffraction (EBSD) were done on the surfaces. Ex situ nano-indentation measurements were also performed on the IMC. Results have shown that the IMC formation can be observed while aging within a SEM chamber.


High copper alloys were required by the industry to improve mechanical and electrical contact resistance for connecting device. This work addresses the electrical contact resistance law versus force in the range (1–100 N) for sphere/plan shapes. The designed samples are submitted to indentation (static contact) and insertion (sliding contact). Experimental power law of contact resistance versus forces was obtained where the law parameters are well related to electrical resistivity, Young modulus, yield stress... Previous analytical relationship Rc=f(Fc) in the literature and finite element simulation code are used to discuss the origin and the validity of such practical power law. Nevertheless the analytic expression are found unsatisfactory, the numerical model gives some agreement with this previous experimental law. However better convergence between numerical and experimental data was obtained in indentation when the surface topography is considered. The obtained results are a useful tool to evolve compromise between the electrical and mechanical aspects for a high loading contact. The main statement is that numerical model including the real topography and roughness is robust so it can be used in different contact shape and complex design for contact resistance evaluation. Finally, depending on the hardness and the resistivity, these uncoated materials were found to act on fretting apparitions and its level.


In this article polarizability properties of spheres and ellipsoids are analyzed. For limiting shapes (disks and needles), the polarizability values can theoretically become extremely large. In the limiting process, however, the sequence is crucial in which the geometric parameters and the permittivity magnitude approach infinity. This article determines the levels of the achievable polarizability, which levels dictate the limits of the effective parameters of the composite to be made of such components. Furthermore, the plasmonic details in the negative permittivity domain are connected with the positive-permittivity behavior. Particular geometries carry over the plasmonic response to ENZ (epsilon-near-zero) materials, which brings forth interesting perspectives for material design with extreme parameters. These singularities are carefully analyzed in the present paper for non-magnetic and non-chiral particles.


This paper presents the modeling of an argon micro-plasma produced by microwaves (2.45 GHz) at atmospheric pressure. The study uses a one-dimensional stationary fluid-type code that solves the transport equations for electrons, positive ions Ar+ and Ar+ 2, and the electron mean energy, together with Poisson's equation for the space-charge electrostatic field, Maxwell's equations for the electromagnetic excitation field and the gas thermal energy equation. The model uses a simple kinetic scheme for Ar that includes the ground state, an excited state representing the lumped 4s levels, and two ionization states associated to the atomic and the molecular ions. The ions are assumed to be in thermal equilibrium with the neutral gas, having the same temperature profile.

Stable mono-filamentary dielectric barrier discharges (MF-DBDs) are achieved between two insulated electrodes in pure krypton, between 100 and 600Torr. Electrical characterization, spectroscopic and kinetic analyses of the MF-DBD are performed. The fast supply current pulse provides reliable triggering for spectroscopic measurements thus allowing an in situ kinetic study. Only the second continuum of krypton is observed and it is attributed to krypton excimers Kr2[ 1u(3P2)] lowv which are correlated to the Kr(3P2) metastable atomic state. Its intensity increases with pressure, due to an enhancement of 3-body collisions with ground state atoms. The kinetic analysis of the luminescence decay of this emission in the post excitation phase, leads to only two exponential components. The pressure dependence of each decay frequency allowed determination of the radiative lifetime of Kr2[ 1u(3P2)] low v excimers and the 3-body collisional rate constant of formation of Kr2[ 1u(3P2)] high v ones are determined.

In this paper we study helical inclusions of a certain shape (called the “optimal shape”), such that the electric, magnetic, and magneto-electric polarizabilities are equal, and discuss unusual reflection properties of artificial materials based on such inclusions. We study helical particles with optimized design parameters, which can make the realization of media with equal dielectric and magnetic susceptibilities possible. Not canonical helix, which consists of a split loop with two straight-wire sections, but the true helix, which is obtained by bending a wire with a constant pitch angle is investigated. The geometry of the helices makes it possible to create a composite material with equal permittivity and permeability.In such material optimal helices are located in pairs and each pair consists of the right-handed and left-handed helix.Thus compensation of chiral properties of a material as a whole is achieved.

The precise characterization of the local microstructure situation is a precondition to investigate and to understand the degradation phenomena occurring in electrical contact materials, because the microstructure is the unique and authentic monitor of the whole materials experience. However, it could not be fully exploited so far due to the lack of adequate characterization techniques. The recently developed FIB-nanotomography may solve this problem. It is based on the automatic serial sectioning by a focused ion beam (FIB) of the volume of interest at the nanoscale and offers an optimum resolution in x-y-z directions. For imaging all well established contrast information of the scanning electron microscopy (chemistry, phase composition, grain structure, texture, stress and strain) is available. After imaging, a detailed 3D image analysis enables the comprehensive quantitative evaluation of local microstructure degradation effects. This work gives an overview of these new possibilities using the example of a Ag/SnO2 contact material in its initial state and after switch operations.

Since electromagnetic (EM) noise resulting from an arc discharge disturbs other electric devices, parameters on electromagnetic compatibility, as well as lifetime and reliability, are important properties for electrical contacts.To clarify the characteristics and the mechanism of the generation of the EM noise, the current noise up to GHz band frequency generated by slowly breaking contacts with external direct current (dc) magnetic field, up to 40 mT, was investigated experimentally using Ag and AgSnO2 material.To reveal the characteristics as pure clean surface contact operation, the arc only at the operation of the first contact break was measured.Firstly, the effect of the external dc magnetic field on the duration and voltage fluctuation of the breaking arc of AgSnO2 material, which has relatively longer arc duration, was quantified.The experimental results on AgSnO2 material newly revealed that although applying external dc magnetic field is effective in reduction of duration of gaseous phase in arc discharge, higher variation of contact voltage in the gaseous phase which results in high frequency noise is caused.Secondly, the effect of the external dc magnetic field on the breaking arc of Ag was measured.It was found that larger current noise arises, when the contact voltage is rapidly varied at the arc discharge.There are two kinds of rapid changes, which cause high-frequency EMC problem, in the voltage waveform.One is at extinction of arc discharge.Other kind is short-duration arc (short-arc) before the ignition of the continuous metallic arc.Especially, we focused on the characteristics of the short-arc at the initial of the opening of the contact for clarifying the high frequency EMC problem.It was demonstrated that the spectrum of current noise in the case of “B = 30 mT” is smaller than that in the case of “B = 0 mT”.In addition, duration and fluctuation of short-arc is suppressed by the dc magnetic field.These results are basic and useful finding to know not only the noise generation in the contact-breaking phenomena but also the material dependency for EMC problems.

Relativistic optics in moving media is an old topic in electromagnetic theory. The study of bianisotropic media – a very important class of metamaterials – stems from the research in that topic. However, a coordinate-free approach to moving media leads to rather cumbersome algebraic manipulations with tensors (or dyadics). In this article we present an alternative framework to deal with moving media: using spacetime algebra, the Clifford (geometric) algebra of Minkowski spacetime, we show that the inherent complexity of this subject can be substantially reduced through a transformation – the vacuum form reduction – that maps our problem into an equivalent spacetime with the same formal spacetime constitutive relation as real vacuum. This is made clear by showing that the two Maxwell equations (in spacetime) are reduced to a single Maxwell equation as in vacuum. We apply this technique to plane wave propagation in moving isotropic media which, from the laboratory perspective (that sees the movement), are actually nonreciprocal bianisotropic media. Our results are in full agreement with the conventional tensor and dyadic analyses.

Flowing microwave N2 afterglows at reduced pressure are studied as a source of N-atoms. It is presently reported results obtained by pulsing the nitrogen gas flow with an electromagnetic (EM) valve before the plasma, starting with discharge conditions of continuous flow around 1 Torr. By keeping the microwave power tuned on as in continuous flow, it is obtained two successive plasmas: the first one at a pressure of 2–3 Torr when the flow gas is on and the second one at lower pressure (0.4-0.5 Torr) when the flow gas is off. The gas pressures were measured in a 5 L post-discharge chamber. The two plasmas are here analysed by emission spectroscopy and the transmitted powers are deduced from the N2 +/N2 intensity ratio for both cases. It is obtained about the same power as for continuous flow when the flow gas is on with a negligible reflected power. The transmitted power is lower and thus the reflected power is important when the flow gas is off. The emission of the N2 1st positive system at 580 nm, signature of the N-atom recombination in the afterglow, is observed in the reactor after the gas pressure rise, with a maximum intensity obtained for a duty cycle of 0.5 at a period of 2 s, corresponding to a maximum N-atom density of about 1015 cm-3 and a pressure variation Δp in the range 2.3-0.5 Torr.

The formation of negative ions produced in a negative point-to-plane corona discharge fed by a Ar/N2/CH4 gas mixture has been studied using mass spectrometry. The measurements were carried out in flowing regime at ambient temperature and a reduced pressure of 460 mbar. The CN- anion has been found to be the most dominant negative ion in the discharge and is believed to be the precursor of heavier negative ions such as C3N- and C5N-. The most likely pathway for the formation of such molecular anions is H-loss dissociative electron attachment to HCN, H3CN and H5CN formed in the discharge. These same anions have been detected in Titan's atmosphere and the present experiments may provide some novel insights into the chemical and physical mechanisms prevalent in Titan's atmosphere and hence assist in the interpretation of results from the Cassini Huygens space mission.

New microwave nonreciprocal properties are investigated in “ferrite plate – grating of resonant elements” metasandwiches arranged along the axis of a rectangular waveguide in a transverse constant magnetic field. Giant nonreciprocity in the transmission is observed at the ferromagnetic resonance frequencies at certain values of the magnetic field under conditions of a mutual influence between the ferromagnetic and the grating resonances. In addition, nonreciprocal splitting of the resonance in grating elements is observed under small magnetic field, which is much less than the field necessary to the ferromagnetic resonance excitation. The nonreciprocal transmission does not take place in the case of free ferrite in the absence of a grating. Sign reversal of the nonreciprocity is observed, when ferrite transfers to the opposite side of a grating as well as under certain values of the constant magnetic field, when the sign reversal of difference between frequencies of the ferromagnetic resonance and the grating resonance takes place. Nonreciprocal effects are explained by the interaction between precessing spins in ferrite and a magnetic field of the surface wave, formed by a grating, and by coupling between the resonances of grating elements. It has been shown theoretically that microwaves in waveguide with bianisotropic layer, simulating a grating of resonant elements, are elliptically or circularly polarized with frequency and spatially – dependent rotating sense of the microwave magnetic field. The nonreciprocal effects have been observed for different grating elements: for both electric dipoles and chiral elements.

Due to ongoing miniaturization in electronics, connector contact designs have to follow the same trends. The prediction of the mechanical and electrical performance of low force connector contacts becomes increasingly important. This paper shows a new approach for modeling elastic plastic contact between two multi-layered non-conforming rough bodies subjected to pressure and shear traction. Three main considerations will be presented: realistic surface simulations, numerical simulation of contact interfaces, and constriction resistance calculations. (i) Since measured three dimensional (3D) digitized surface data is not always available, having the ability to numerically simulate “realistic” rough surface topographies is of great importance. It will be shown how realistic engineered surfaces can be modeled using five scale independent parameters: RMS roughness, x/y correlation length, kurtosis and skew. (ii) A numerical algorithm has been developed which calculates the stresses and deformations generated in a contact system with up to three different layers per contact partner. The mechanical properties of each individual contact layer are incorporated into the calculation. This numerical algorithm is based on Papkovich-Neuber Potentials, both multi grid and conjugate gradient methods are used, and the plastic deformation of the individual contact points (a-spots) can be interpolated using different material hardening behaviors. (iii) Once the contact interface a-spot distribution is simulated, the constriction resistance of the true contact area can then be calculated. The voltage drop within the contacting bodies is interpolated by iteratively solving the Laplace equation. The electrical properties of all the individual contact layers as well as the interaction between the individual a-spots are taken into account. A validation of these simulation algorithms will be shown using a hard Au/Ni/CuSn6 contact system. The results show excellent agreement between measured and simulated contact resistance results over a normal force range from 1 cN up to 250 cN. The algorithms have been implemented with an “easy to use” Windows software interface called “First Contact”. The software also incorporates a material database that when used together with a surface modeler, allows for the fast calculation and 3D visualization of all mechanical and electrical contact characteristics. 


The arc behavior in an arrangement of parallel arc rails with a splitter plate in between has been investigated experimentally and in numerical computations. Thereby, the arc is simulated by coupling finite-volume modeling for the gasdynamics and finite-elements modeling for the electromagnetics. The formation of arc roots on the splitter plate can be described by a thin layer of elements with a current-density dependent specific resistance. The simulations were extended to model the experimental arrangement exactly. Additionally, net emission coefficients and radiation heat conductivity of air plasma instead of a simplified T4 net emission of a black body were used to model the radiative cooling of the arc. The results of the arc voltage, the arc movement and the splitting process have been compared to measurements and high speed movies of the arc and yield good correlation. Moreover, the simulations allow good insight into the temperature distribution of the arc and the movement of the pressure waves caused at the arc ignition.


Plasmas are energetic media that can give birth to dust particles due to the presence of reactive gases or plasma-surface interactions. Industrial plasmas are often concerned by these dust particles that can be either unwanted or useful for the process. For fusion plasmas, production of dust particles from wall erosion is a serious issue for performance and safety reasons. In this article, some aspects of dusty plasmas with potential implications for plasma experimenters will be discussed. Convenient ways for detecting the presence or the growth of dust particles will be presented. The spatial distribution of the dust cloud during the plasma phase determines the subsequent dust particle deposition. It will be shown that some reactor regions can attract or repeal these dust particles. Finally, the dust particle dynamics after the plasma extinction will be investigated. A special attention will be paid on the residual electric charge that can stay attached on the dust particle surface and on its implications for dust particle control or deposition.

Full wave numerical study of electromagnetic wavereflection from and transmission through an array of thin, perfectconducting, planar strip complex-shaped elements placed on amagnetized ferrite substrate is carried out. Our results show,that the absorption level and the frequency band of the structure,when the ferromagnetic resonance and a metal element resonance areclose in frequency, are larger than the correspondingcharacteristics of the ferrite layer without metal elements. Asignificant enhancement of the Faraday rotation has frequencyshift with respect to the main resonance. Both right-handed andleft-handed circular polarized incident waves interact effectivelywith a metal array placed on ferrite substrate unlike the knownresonant interaction when only one kind (right- or left-handed) ofcircular polarized waves interacts with the ferrite slab withoutmetal elements.

Cylindrical hollow cathode magnetron sputtering (HCMS) system was used to deposit crystalline titanium dioxide thin films on p-Si (100) substrates. For a fixed pressure of 0.6 Pa total gas flow rate of 20 sccm and power of 55 W, the influence of the oxygen percentage in the Ar+O2 gas mixture on the structural and surface properties of the films was studied by profilometry, XRD and AFM. The substrates were placed inside the hollow cathode at different positions along its symmetrical axis. Numerical simulations of cathode ion collection probability (CICP) were done in order to compare calculated data with the deposition process characteristics. The results indicate that the deposition rate and the surface roughness gradually decrease with the distance from the bottom of the cathode, due to the decrease of the CICP. The increase of the oxygen percentage in the gas discharge influences directly the deposition rate and decrease the surface roughness. The XRD analyses show that all the films are crystalline with predominant anatase (101) and rutile (110) orientations.