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The electric double layer in argon helicon plasma by using floating electrostatic probe and local optical emission spectroscopy under different external magnetic field was investigated. Results show that electrons generated in the plasma source can be magnetized by the magnetic field and transported by the gradient of diverging magnetic field in the diffusion chamber, giving rise to the hollowed distribution of electron temperature. The electron temperature on axis has a sudden decrease, leading to the sudden decrease of plasma density as well as the plasma potential, forming a double layer structure. The position of double layer moves along with the position of diverging magnetic field, and the potential drop increases along with the strength of magnetic field. The structure of the external magnetic field plays the decisive factor for the double layer in helicon plasma.

The electric polarization for the vortex distribution of magnetization in a double-layer exchange-coupled ferromagnetic film of finite dimensions is studied numerically. The electric polarization of such a film is determined by its component of perpendicular magnetization. The contribution to the electrical polarization of individual layers of a sample is different and depends on the size of the film. As the transverse dimensions of the film shrink, the value of the average polarization grows. When magnetized in the perpendicular direction, the average polarization passes through a maximum.

The double-layer approach (DLA) possesses superior features for the analysis of static electromagnetic problems. In this article, dealing with the magnetostatic analysis, we introduce two kinds of double layers: the first one on the surface of the magnetic body and the second one on the cut-surface within the exciting current loop. From the double layers on the cut-surface, we were able to derive a novel, unified exciting potential, which facilitates the treatment of any magnetostatic problem, including multiply connected problems. Furthermore, in this article, we use for the first time DLA for the analysis of magnetic forces acting on the magnetic bodies. The law of action and reaction provides a self-check function within DLA, enabling thus the simple and reliable tool for the confirmation if the computed results are adequate and accurate. This improved, DLA-based approach for the force analysis together with the introduced “action-reaction” principle for the self-checking of the force calculation are, to the authors' best knowledge, not known in the scientific community so far. Finally, we would like to emphasize that the presented DLA enables accurate, self-checked, generic analysis of the real-world devices, providing advanced treatment of both geometrical singularities (edges, corners) and materials used (high permeability, nonlinearities).

Microwave absorption characteristics of double layer of barium hexaferrite attached on the silica to from a composite on the basis of wave propagation theory have been investigated. Barium hexaferrite, BaFe12O19, was synthesized through ceramic method from stoichiometric mixtures of BaCO3 and Fe2O3 as precursors. The mixture was pelletized under the pressure of 10 MPa and sintered at 1100 °C for 5 hours. Silica in the forms of powder was purified by using HCl. The crystal structure of the samples was characterized using X-ray diffraction (XRD), microstructure was examined using scanning electron microscope (SEM), hysteresis curves recorded by PERMAGRAPH techniques, whereas the microwave absorbing properties for X-band was recorded using a vector network analyzer (VNA). Relative complex permeability and permittivity, and reflection loss values were calculated at given thickness according to transmittance line theory within the range 8.2–12.4 GHz. Based on this study, the layer dimension and frequency that results in low reflection loss can be estimated from the material properties of the barium hexaferrite/silica composite material.

The dynamic behavior of large amplitude ion-acoustic double layers in a plasma is investigated in the presence of two-temperature nonextensive electrons. The effects of physical parameters, such as the temperature and concentration of positive ions on the formation and structure of double layer are discussed. It is shown that the depth of the Sagdeev potential and the amplitude of both positive and negative ion-acoustic double layers sensitively depend on the temperature and the concentration of positive ions. The obtained results are also compared with the results of a similar Maxwellian plasma with warm ions and two (cold and hot) electron species.

The plasma on a magnetic field line in the downward current region of the aurora is simulated using a Vlasov model. It is found that an electric field parallel to the magnetic fields is supported by a double layer moving toward higher altitude. The double layer accelerates electrons upward, and these electrons give rise to plasma waves and electron phase-space holes through beam–plasma interaction. The double layer is disrupted when reaching altitudes of 1–2 Earth radii where the Langmuir condition no longer can be satisfied due to the diminishing density of electrons coming up from the ionosphere. During the disruption the potential drop is in part carried by the electron holes. The disruption creates favourable conditions for double layer formation near the ionosphere and double layers form anew in that region. The process repeats itself with a period of approximately 1 min. This period is determined by how far the double layer can reach before being disrupted: a higher disruption altitude corresponds to a longer repetition period. The disruption altitude is, in turn, found to increase with ionospheric density and to decrease with total voltage. The current displays oscillations around a mean value. The period of the oscillations is the same as the recurrence period of the double layer formations. The oscillation amplitude increases with increasing voltage, whereas the mean value of the current is independent of voltage in the 100 to 800 V range covered by our simulations. Instead, the mean value of the current is determined by the electron density at the ionospheric boundary.

Control of the proton beam charge and energy in a laser-driven double-layer target was numerically investigated. Generally the proton beam charge is determined by the areal density σ = nl of the second layer, while the accelerating field is governed by the substrate thickness L . From a series of one-dimensional particle-in-cell simulations over a broad range of σ and L , it was confirmed that those two control parameters do not interfere significantly, indicating the beam charge and energy can be separately controlled. We suggest self-assembly monolayers technique be used for the fabrication of the areal density of the second layer.

This investigation is composed of an observational part, plus a new theoretical model interpreting the related exhibited satellite datasets through an entirely new approach concerning the substorm's ultimate excitation mechanism. First, we present a few representative case studies showing the Bz component of the magnetic field to develop quasi-periodic negative deflections with periodicities ranging from T=15 to 60s in the central plasma sheet (CPS) with persistent tailward plasma flows. The wave activity of Bz is much lower outside the CPS, while occasionally almost a monochromatic response is identified. In certain cases, a profound change of frequency is evident and happens most probably due to the Doppler-effect; there is a relation between the plasma velocity enhancement and the increase of frequency. When comparing the amplitude of Bz deflections to the lobe magnetic field, one plausibly may infer that the deflections reflect the very dynamics of the source itself. Therefore, we put forward the concept about "a pulsating source", and more specifically, we adopt the pulsating "twin Double Layer (DL) structure" as the ultimate mechanism converting magnetic energy to kinetic. The DL acts either as a resistor or a capacitor and the twin-DL structure approximately behaves in a way similar to the cardiac cycle with repeated, rhythmic contractions and expansions. The contraction phase represents the abrupt local thinning of the plasma sheet (PS) that terminates explosively, heating the plasma and accelerating energetic particles. The expansion phase corresponds to a local distention of the source, which also terminates explosively. The DLs are oppositely polarized depending on the range of Rc whether it fulfills the condition rgi ≤ Rc < 9 rgi or rge < Rc < rgi, where rgi (rge) and Rc are the ion (electron) gyro-radius and the curvature radius of the local magnetic field, respectively. In more detail, the "akis structure", as it was earlier introduced by Sarafopoulos [1, 2] and further elaborated in this work, repetitively forms DLs that undergo a transition from depolarization to repolarization in each of the consecutive cycles. The collapse of the dissipation region (leading to local dipolarization) seems to occur when rge < Rc < 9rge. Large scale Boström's type II field aligned currents (FACs) flow and neutralize the net charges produced by "charge separation processes" within the twin-DL structure; thus the whole structure principally operates (under favorable conditions) like a huge resonant RLC-type circuit. Actually the pulsating source is an integral part of that huge (resonating) circuit, wherein even the ionosphere obviously plays its vital role imposing a positive feedback. The author of this study believes that Faraday's law can be experimentally validated with his suggested model more reliably than with the alternative X-type magnetic reconnection model incorporating the concept of "magnetic diffusion". The presently proposed "akis structure" embedded in the whole magnetotail's current system is presumably a precious structure with novel features. The source will probably be triggered at that place in which the condition for resonance is satisfied, while the resonance dramatically increases the rate of energy conversion, that is the efficiency of the source.

We report the experimental generation of highly energetic carbon ions up to 48 MeV per nucleon by shooting double-layer targets composed of well-controlled slightly underdense plasma and ultrathin foils with ultraintense femtosecond laser pulses. Particle-in-cell simulations reveal that carbon ions are ejected from the ultrathin foils due to radiation pressure and then accelerated in an enhanced sheath field established by the superponderomotive electron flow. Such a cascaded acceleration is especially suited for heavy ion acceleration with femtosecond laser pulses. The breakthrough of heavy ion energy up to many tens of $\mathrm{MeV}/\mathrm{u}$ at a high repetition rate would be able to trigger significant advances in nuclear physics, high energy density physics, and medical physics.

After the theory of dynamic double layers in laser-produced plasmas arrived at several significant results in agreement with measurement, including particle acceleration, a clarification was given to the paper by Bryant et al. (1992) negating such acceleration. The discrepancy seems to be in the definition of static double layers in contradiction with dynamic double layers that are created in laser-induced plasma. We present here new results on the acceleration of electrons in a laser-irradiated plasma by double layer mechanisms. A simple analytical example is given.

In the present investigation, ion-acoustic double layers in an inhomogeneous plasma consisting of Maxwellian and non-thermal distributions of electrons are studied. We have derived a modified Korteweg–de Vries (mKdV) equation for ion-acoustic double layers propagating in a collisionless inhomogeneous plasma. It is observed that the non-thermal parameters affect the amplitude and width of the double layer which further depend on the density.

Small amplitude ion-acoustic double layers in an unmagnetized and collisionless plasma consisting of cold positive ions, q-nonextensive electrons, and a cold electron beam are investigated. Small amplitude double layer solution is obtained by expanding the Sagdeev potential truncated method. The effects of entropic index q, speed and density of cold electron beam on double layer structures are discussed.

An analytical solution for time stationary weak double layers in an unmagnetized dusty plasma by using Sagdeev’s pseudopotential method is studied considering dusts with constant charge and mass. Here, the plasma consists of electrons, ions and negatively-charged micron-sized dust particles. From the study, expressions for the potential and the dust acoustic velocity of the double layer is determined.

[1] The formation and dynamic evolution of double layers which form inside the auroral cavity are studied using one- and two-dimensional electrostatic particle-in-cell simulations. Both the one- and two-dimensional simulations are confined to processes that occur in the auroral cavity and include four plasma populations: hot electrons, H+ and O+ anti-earthward ion beams and a hot H+background population. We show that double layers inside the auroral cavity can evolve nonlinearly from ion phase space holes and are supported by the cold, anti-earthward traveling O+beam. We then present two-dimensional particle-in-cell results which show that double layers in the interior of the auroral cavity can form in higher dimensions. The electric field structure in 2-D is verified as a double layer through simultaneous analysis of the parallel electric field and H+ and O+ phase space.

The laser-driven acceleration of proton beams from a double-layer cone target, comprised of a cone shaped high-Z material target with a low density proton layer, is investigated via two-dimensional fully relativistic electro-magnetic particle-in-cell simulations. The dependence of the inside diameter (ID) of the tip size of a double-layer cone target on proton beam characteristics is demonstrated. Our results show that the peak energy of proton beams significantly increases and the divergence angle decreases with decreasing ID size. This can be explained by the combined effects of a stronger laser field that is focused inside the cone target and a larger laser interaction area by reducing the ID size.

The pseudopotential technique is applied to a multicomponent plasma consisting of nonthermal electrons and warm positive and negative ions with drift motion with a view to studying ion-acoustic double layers. Conditions for the existence of such layers are obtained, two critical concentrations of negative ions being identified which control the formation and nature of the ion-acoustic double layers. The effects of nonthermal electrons, negative-ion concentration, and negative-ion temperature on the double layer formation and structure are also investigated. The nonthermal electrons and the negative ions are shown to contribute significantly to the excitation and structure of the double layers. The importance of the results in the context of magnetospheric and auroral plasmas is discussed.

Application of the method of collocations to solve the boundary integral equation for the density of the double layer at a piecewise constant approximation is incorrect, since in this case the boundary condition for the vector of the magnetic field is not executed. Proposed in this paper, a discrete-field model does not contain the collocation points, and the boundary conditions are an integral manner. The proposed modification of the method of the double-layer magnetic charges is not necessary in the conduct of conditional partition, which greatly simplifies the process of algorithmization method.

The thermal performance of a sunspace attached to a living room located in Amman-Jordan has been investigated. Six configurations that differ by the ratio of glazed surface area to opaque surfaces area are studied. A novel configuration that utilizes an inclined front surface is thermally investigated. The effect of orientation of the sunspace, opaque wall and floor absorption coefficients and number of glass layers on the thermal performance is evaluated. Results show that the sunspace reduces the heating load during the winter, while it creates a serious overheating problem during summer. The contribution of reducing heating requirements increases with increasing the ratio of glazed surface to opaque surface area. Also, the optimal contribution was obtained when the sunspace was oriented to the south. Two passive cooling techniques are proposed and evaluated to overcome the summer overheating problem. Additionally, a passive heating technique is proposed to minimize the thermal losses during winter nights. Internal shading and night ventilation successfully minimize the overheating problem. Employing the three passive techniques with sunspace, results show that as high as 42% reductions in annual heating and cooling load can be achieved. Utilizing an inclined front surface with double layer of glass can further reduce heating and cooling load requirements.

The plane-parallel flow of the collisionless ion flux integrally neutralized by Boltzmann electrons is considered. It is shown that there is a rigid unique relation between the velocity and current density in the quasi-neutral region on the collector, which defines equilibrium conditions of the near-cathode double layer.

The arrangement of permanent magnets in double-layer interior permanent-magnet motors is optimized for variable-speed applications. First, the arrangement of magnets is decided by automatic optimization. Next, the superiority of the optimized motor is discussed by considering d- and q-axis equivalent circuits that take into account the magnetic saturation of the rotor core. Finally, experimental verification is carried out with a prototype motor. It is confirmed that the maximum torque of the optimized motor under both low-speed and high-speed conditions is higher than that of conventional motors because of the relatively large q-axis inductance and small d-axis inductance. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 183(4): 54–63, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22348

On the basis of two magneto-fluid model for two time-scales, the evolution of double layer in the downward current region of the aurora is numerically simulated under the non-static limit case. The results show that localized drop in density owing to collapsed high-frequency field can lead to the formation of double layer. The amplitude of the double layer is the order of the electron temperature, and the ramp potential is up to 36 V localized to tens of Debye lengths, which is around 100–200 m. These are consistent with the measurements in both the ramp potential and thickness by the Fast Auroral SnapshoT satellite in the downward current region of the aurora.

Formation of large-amplitude double layers in a dusty plasma whose constituents are electrons, ions, warm dust grains and positive ion beam are studied using Sagdeev’s pseudopotential technique. Existence of double layers is investigated. It is found that both the temperature of dust particles and ion beam temperature play significant roles in determining the region of the existence of double layers.

Intensely luminous double layers develop and then expand in size in a visibly glowing RF discharge produced using a plasma source consisting of a semi-transparent cylindrical mesh with a central electrode, in a linear plasma chamber. Although RF discharge is known to be independent of device geometry in the absence of magnetic field, the initiation of RF discharge using such a plasma source results in electron drift and further expansion of the plasma in the vessel. The dynamics of complex plasma structures are studied through electric probe diagnostics in the expanding RF plasma. The measurements made to study the parametric dependence of evolution of double layer structures are analyzed and presented here. The plasma parameter measurements suggest that the complex potential structures initially form with low potential difference between the layers and then gradually expand producing burst oscillations. The present study provides interesting information about the stability of plasma sheath and charge par...

Recent developments in laboratory double layers from the late 1980s to the spring of 2007 are reviewed. The paper begins by a lead up to electric double layers in the laboratory. Then an overview of the main double layer devices and properties is presented with an emphasis on current-free double layers. Some of the double layer models and simulations are analysed before giving a more complete description of current-free double layers in radiofrequency plasmas expanding in a diverging magnetic field. Astrophysics double layers are briefly reported. Finally, applications of double layers to the field of plasma processing and electric propulsion are discussed.

It is shown that the features of formation and structure of a stationary charged layer at the interface between a symmetric plasma and a wall depend to a considerable extent on the ratios τ± (for both plasma components) of the thermal velocity to the velocity of the plasma flow at the beginning of the layer, as well as on the polarity and magnitude of electric potential φW of the wall. The conditions under which a double layer-type structure can be formed in the near-wall layer of the symmetric plasma are formulated. The charge double layer contains two sublayers with opposite polarities of charge for a fixed polarity of the wall. The charge polarity of sublayer adjoining the plasma is opposite to the polarity of the wall, while the sublayer adjoining the wall has a charge of the same polarity as that of the wall. The ranges of symmetric plasma parameters for which the double layer exists are determined. It is found that a structure of this type can be formed nor for all parameters of the plasma, for which a charged layer exists; the possibility of formation of this structure depends on τ± as well as on the sign of the potential of the wall.

The conditions for formation of ion acoustic weak double layer in a dusty plasma are investigated. In case of much lower value of ion-electron temperature ratio, the weak double layer is observed when the fraction of the negative charge in the plasma on the dust grain is , whereas for equal ion-electron temperature it is observed only when the fraction is . The parameter regimes of transition from compressive to rarefactive double layer are also specified.

An enhanced long-distance transport of periodic electron beams in an advanced double layer cone-channel target is investigated using two-dimensional particle-in-cell simulations. The target consists of a cone attached to a double-layer hollow channel with a near-critical-density inner layer. The periodic electron beams are generated by the combination of ponderomotive force and longitudinal laser electric field. Then a stable electron propagation is achieved in the double-layer channel over a much longer distance without evident divergency, compared with a normal cone-channel target. Detailed simulations show that the much better long-distance collimation and guidance of energetic electrons is attributed to the much stronger electromagnetic fields at the inner wall surfaces. Furthermore, a continuous electron acceleration is obtained by the more intense laser electric fields and extended electron acceleration length in the channel. Our investigation shows that by employing this advanced target, both the forward-going electron energy flux in the channel and the energy coupling efficiency from laser to electrons are about threefold increased in comparison with the normal case.

In this article we present electric field, magnetic field, and charged particle observations from the upward current region of the aurora focusing on the structure of electric fields at the boundary between the auroral cavity and the ionosphere. Over 100 high-resolution measurements of the auroral cavity that were taken by the Fast Auroral Snapshot (FAST) satellite are included in this study. The observations support earlier models of the auroral zone that held that quasi-static parallel electric fields are the primary acceleration mechanism. In addition to the statistical study, several examples of direct observations of the parallel electric fields at the low-altitude boundary of the auroral cavity are put forth. These observations suggest that the parallel electric fields at the boundary between the auroral cavity and the ionosphere are self-consistently supported as oblique double layers.

The distribution of plasma and electric fields close to the far side of the Moon are discussed. The existence of a strong double layer behind the Moon is predicted and its parameters are investigated. Electric currents associated with this double layer and finite conductivity inside the Moon are estimated. The fluxes of suprathermal electrons behind the Moon in different energy ranges are calculated and compared with the experimental data. It is shown that the theoretical results are in qualitative agreement with the data obtained by Lunar Prospector and the Apollo 15 subsatellite.

Double layers were discovered by Irving Langmuir; (who called them “double sheathes”) in his experiments with low-pressure discharges in the 1920s. Subsequently, they were observed by nearly all the pioneers in experimental plasma physics (Tonks 1931; Schonhuber 1958; Crawford and Freeston 1963; Babic et al. 1971).

Using a Vlasov code for simulating fully nonlinear behavior of a plasma driven by an applied potential drop, it is shown that fast solitary potential pulses in the form of electron holes are a common feature of the high potential side of a strong double layer. Temporal and spatial features of the electron holes seen in the simulations are compared against the measurements from FAST. The evolution of the electron beam accelerated by a double layer and that of the plasma on its high potential side generate the suitable conditions for nearly continuously creating fast moving electron holes.

A theoretical model is presented to investigate the double layers, associated with the kinetic Alfven waves, in a magnetized electron–positron–ion plasma with a small but finite value of β, and small-amplitude double layer solutions are obtained. The existence of small-amplitude double layers requires that the density of ions is appreciably larger than that of positrons at equilibrium. The properties of the double layers are determined by the ratio between the number densities of positrons and ions at equilibrium, the direction cosines defining the moving frame, as well as the electron to positron temperature ratio.

It is found that, by means of numerical simulations, an ion acoustic instability (v/sub d/ < v/sub te/) results in the formation of double layers in a sufficiently long system. Anomalous resistivity generated by the ion acoustic instability causes the buildup of a dc potential which in turn accelerates electrons further to enhance the original instability leading to the formation of double layers. A necessary condition required for generating a double layer is given.

The maximum electric field in bursts of plasma frequency oscillations produced in an anode double layer was measured by observing deflections of a probe electron beam. It is found that the electric field is larger than the threshold field required for strong turbulence associated with caviton formation and Langmuir soliton collapse.