Large amplitude ion-acoustic double layers in a plasma havingvariable-charge dust grain particles

The dust grain charging effect on large amplitude ion-acoustic double layers in a dusty plasma are investigated by the numerical calculation. The nonlinear structures of ion-acoustic double layers are examined, showing that the characteristics of the double layer sensitively depend on the dust charging effect, the influence of the ion temperature, the electrostatic potential, and the Mach number. The flow of the plasma current to the surface of dust particles increases the dust charge numbers. The effect of the ion temperature decreases the propagation speed of the ion-acoustic double layers and decreases the dust charge numbers. It is found that rarefactive double layers can propagate in this system. New findings of large amplitude ion-acoustic double layers with the dust charging effect and finite ion temperature in a dusty plasma are predicted     

A Study of Small Amplitude Ion Acoustic Double Layers in a Multi-Species Unmagnetized Plasma

We report here analytic solutions for weak ion acoustic double layers in an unmagnetized multi-species plasma having two electron components, each described by a Boltzmann distribution, and two ions of different masses, each described by usual fluid equations. The velocity and the width of the double layers for different amplitude has been studied.     

Low frequency electrostatic nonlinear structures in an inhomogeneous magnetized non-Maxwellian electron–positron–ion plasma

The properties of low frequency (coupled acoustic and drift wave) nonlinear structures including solitary waves and double layers in an inhomogeneous magnetized electron–positron–ion (EPI) nonthermal plasma with density and temperature inhomogeneities are studied in a simplified way. The nonlinear differential equation derived here for the study of double layers in the inhomogeneous EPI plasma resembles with the modified KdV equation in the stationary frame. But the method used for the derivation of nonlinear differential equation is simple and consistent to give both the stationary solitary waves and double layers. Further, the illustrations show that superthermality κ, drift velocity and temperature inhomogeneity have significant effects on the amplitude, width, and existence range of the structures.     

Small amplitude ion-acoustic double layers with cold electron beam and q-nonextensive electrons

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.     

Adiabatic dust-acoustic double layers in two temperature electron dusty plasma

Large amplitude adiabatic double layers are investigated in the case of positively charged dusty plasma. The dust grains provide the inertia and the background plasma is formed of two electron populations, hot and cold, in thermal equilibrium. Using fluid equations and the pressure balance equation, the Sagdeev pseudo-potential is driven in the stationary frame. The dependence of the double layers amplitude and Mach number on various parameters such as the hot to cold electron densities, the temperature ratio and the dust drift velocity have been numerically examined. The critical parameters, for which a nature change occurs, are found.     

Large Amplitude Dust Ion Acoustic Solitons and Double Layers in Dusty Plasmas with Ion Streaming and High-Energy Tail Electron Distribution

Large amplitude dust ion acoustic （DIA） solitons as well as double layers （DLs） are studied in a dusty plasma having a high-energy-tail electron distribution. The influence of electron deviation from the Maxwellian distribution and ion streaming on the existence domain of solitons is discussed in the （M, f） space using the pseudo-potential approach. It is found that in the presence of streaming ions and for a fixed f, solitons may appear for larger values of M. This means that in the presence of ion streaming, high values of the Mach number are needed to have soliton. The DIA solitary waves profile is highly sensitive to the ion streaming speed. Their amplitude is found to decrease with an increase of the ion streaming speed. In addition, we find that the ion streaming effect may lead to the appearance of double layers. The results of this axticle should be useful in understanding the basic nonlinear features of DIA waves propagating in space dusty plasmas, especially those including a relative motion between species, such as comet tails and solar wind streams, etc.     

Theory of weak ion acoustic double layers

We present a theory of small amplitude ion acoustic double layers in a homogeneous unmagnetized plasma. Using fluid equations for ions and a general equation of state for electrons, we show that such double layers exist when the free and reflected electron distributions are different from maxwellians.     

Small amplitude double layers in an electronegative dusty plasma with q-distributed electrons

The small amplitude dust ion-acoustic double layers in a collisionless four-component unmagnetized dusty plasma system containing nonextensive electrons, inertial negative ions, Maxwellian positive ions, and negatively charged static dust grains are investigated theoretically. Using the pseudo-potential approach and reductive perturbation method, an energy integral equation for the system has been derived and its solution in the form of double layers is obtained. The results appear that the existence regime of the double layer is very sensitive to the plasma parameters, e.g., electron nonextensivity,negative-to-positive ion number density ratio etc. It has been observed that for the selected set of parameters, the system supports rarefactive,(compressive) double layers depending upon the degree of nonextensivity of electrons.     

Large-amplitude double layers in a dusty plasma with an arbitrary streaming ion beam

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.     

On the Acceleration of Energetic Cosmic Particles by Electrostatic Double Layers

The capability of electrostatic double layers of accelerating charged particles to high energies is investigated. Starting from a one-dimensional relativistic double-layer model a two-dimensional relativistic double layer in a current filament is studied. It is found that the filamentary double layer has a maximum potential drop that depends both on the magnitude of the filamentary current and on the composition of the layer. The results are applied to two cosmic double layers?one in a solar electric circuit and another in a galactic circuit. If the layers are composed of protons and electrons, these particles may be accelerated to 1011 eV in the solar layer and to 1014 eV in the galactic layer. It is suggested that the solar double layer may account for the acceleration of solar cosmic rays while the galactic layer may contribute to the generation of cosmic radiation.     

Double-layer-relevant laboratory results

Many double-layer-relevant laboratory experiments have been carried out at the University of Wisconsin. Laboratory stair-step double layers, which resemble three or more weak double layers joined in series, have been produced without ionization. Double-layer floating potential fluctuations have been investigated and progress has been made in developing a novel technique for measuring electron energy distribution functions in low-density double layers (i.e. λ_D ≫probe dimensions). A new inductive plasma source has been developed. With this source, magnetized double layers can be routinely produced. These magnetized double layers are often weak stair-step double layers that are oblique to the magnetic field. Laboratory data of emitting probe characteristics taken in tenuous plasmas have helped to quantify space-charge-enhanced plasma gradient induced error in double-layer electric field measurements made by satellite double probes. Also, magnetic sheaths have been experimentally studied and compared with theory     

Double layers in a field-aligned current driven plasma

The solutions of small amplitude ion acoustic double layers in current-carrying plasma in the presence of the magnetic field have been presented. The electron beam along the magnetic field has only been considered and the drift velocity assumed to be less than the electron thermal velocity. The velocity, the width and the potential of such DLs are calculated.     

Ion Beam Driven Ion Cyclotron Double Layers

We present here a self consistent theory of small amplitude double layers associated with electrostatic ion cyclotron waves in a plasma containing hot electrons, cold ions and traversed by an ion beam. It has been shown that compressive type of double layers solution exists when θ_b (beam temperature) < α_b (beam concentration) < 1.     

Intrinsic resonances in double layers with finite thickness

Short wavelength electrostatic perturbations in one-dimensional magnetized double layers are studied in the local WKB approximation. The corresponding dielectric function shows resonant interaction between fluctuations and electrons whose time of flight across the double layer is an integer multiple of the half period of waves.     

Small amplitude variable charge dust Bernstein-Greene-Kruskal double layers

A first theoretical attempt is made to investigate small amplitude, variable charge dust Bernstein-Greene-Kruskal (BGK) double layers (DLs). The nature of the dust BGK-DLs (compressive or rarefactive), their strength and thickness depend sensitively on the net negative charge residing on the grain surface, the dust grain dynamics and, more interestingly, on the ion-to-electron temperatures ratio.     

Sound transmission through finite lightweight multilayered structures with thin air layers

The sound transmission loss (STL) of finite lightweight multilayered structures with thin air layers is studied in this paper. Two types of models are used to describe the vibro-acoustic behavior of these structures. Standard transfer matrix method assumes infinite layers and represents the plane wave propagation in the layers. A wave based model describes the direct sound transmission through a rectangular structure placed between two reverberant rooms. Full vibro-acoustic coupling between rooms, plates, and air cavities is taken into account. Comparison with double glazing measurements shows that this effect of vibro-acoustic coupling is important in lightweight double walls. For infinite structures, structural damping has no significant influence on STL below the coincidence frequency. In this frequency region, the non-resonant transmission or so-called mass-law behavior dominates sound transmission. Modal simulations suggest a large influence of structural damping on STL. This is confirmed by experiments with double fiberboard partitions and sandwich structures. The results show that for thin air layers, the damping induced by friction and viscous effects at the air gap surfaces can largely influence and improve the sound transmission characteristics.     

Diffraction enhancement and suppression of rotation of plane of polarization in chiral photonic crystals

The oblique propagation of light through a gyrotropic crystal layer placed in an ultrasonic field is considered. The problem is solved using the Ambartsumyan method of addition of layers. The wavelength dependences of the amplitude and polarization characteristics are studied for different values of the problem parameters. Application of such systems is discussed.     

Vibration amplitude and induced temperature limitation of high power air-borne ultrasonic transducers

The acoustic impedances of matching layers, their internal loss and vibration amplitude are the most important and influential parameters in the performance of high power airborne ultrasonic transducers. In this paper, the optimum acoustic impedances of the transducer matching layers were determined by using a genetic algorithm, the powerful tool for optimizating domain. The analytical results showed that the vibration amplitude increases significantly for low acoustic impedance matching layers. This enhancement is maximum and approximately 200 times higher for the last matching layer where it has the same interface with the air than the vibration amplitude of the source, lead zirconate titanate-pizo electric while transferring the 1 kW is desirable. This large amplitude increases both mechanical failure and temperature of the matching layers due to the internal loss of the matching layers. It has analytically shown that the temperature in last matching layer with having the maximum vibration amplitude is high enough to melt or burn the matching layers. To verify suggested approach, the effect of the amplitude of vibration on the induced temperature has been investigated experimentally. The experimental results displayed good agreement with the theoretical predictions.     

Nonlinear Dynamics in a Nonextensive Complex Plasma with Viscous Electron Fluids

Cylindrical and spherical dust-electron-acoustic(DEA) shock waves and double layers in an unmagnetized,collisionless,complex or dusty plasma system are carried out.The plasma system is assumed to be composed of inertial and viscous cold electron fluids,nonextensive distributed hot electrons,Maxwellian ions,and negatively charged stationary dust grains.The standard reductive perturbation technique is used to derive the nonlinear dynamical equations,that is,the nonplanar Burgers equation and the nonplanar further Burgers equation.They are also numerically analyzed to investigate the basic features of shock waves and double layers(DLs).It is observed that the roles of the viscous cold electron fluids,nonextensivity of hot electrons,and other plasma parameters in this investigation have significantly modified the basic features(such as,polarity,amplitude and width) of the nonplanar DEA shock waves and DLs.It is also observed that the strength of the shock is maximal for the spherical geometry,intermediate for cylindrical geometry,while it is minimal for the planar geometry.The findings of our results obtained from this theoretical investigation may be useful in understanding the nonlinear phenomena associated with the nonplanar DEA waves in both space and laboratory plasmas.     

Evidence of coupling between InAs self-assembled quantum dots in thin GaAs buffer layer

We have studied the optical properties of two layers of InAs self-assembled quantum dots (QDs). The QDs were separated by a GaAs barrier with thickness varied from 2.5 to 10 nm. All samples exhibited double peaks from low-temperature photoluminescence spectra. The energy difference between two peaks shows that the origin of the double peaks is different for each sample. In case of the thin barrier thickness, the double peaks are due to the coupling of the ground states of lower and upper dots. In the thick barrier case, the double peaks originate from the ground and excited states because the barrier is thick enough to separate the double QDs.