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We present a study of dust acoustic shock waves in a non-Maxwellian plasma with dust charge fluctuations, which are seen to cause a dissipation term in fluid model, and consequently shocks are generated. In particular, we focus on dust acoustic waves as affected by various dust size distributions. Two distinct dust size distributions—the polynomial and the power law distributions—have been used. For analytical investigation of nonlinear wave propagation in complex plasmas, a reductive perturbation approach is used to obtain the Burgers equation. A dusty plasma system with non-Maxwellian Kappa distribution is considered and it is shown that the amplitude of a shock wave, for the dust size distribution is larger than that for the mono-sized counterpart, while the shock width manifests an opposite trend. Furthermore, the shock wave speed is also affected by the dust size distributions as well as by the nature of velocity distribution function. To benchmark our findings, we apply the proper limit on the spectral index, i.e., κ → ∞ , and retrieve the Maxwellian results. The current findings are crucial for comprehending respective shock distributions for a plasma system exhibiting non-thermal characteristics and having dust size distributions. [ABSTRACT FROM AUTHOR]

We describe measurements of the DC electrical conductivity of warm dense matter using ultrafast terahertz (THz) pulses. THz fields are sufficiently slowly varying that they behave like DC fields on the timescale of electron–electron and electron–ion interactions and hence probe DC-like responses. Using a novel single-shot electro-optic sampling technique, the electrical conductivity of the laser-generated warm dense matter was determined with <1 ps temporal resolution. We present the details of the single-shot THz detection methodology as well as considerations for warm dense matter experiments. We, then, provide proof-of-concept studies on aluminum driven to the warm dense matter regime through isochoric heating and shock compression. Our results indicate a decrease in the conductivity when driven to warm dense matter conditions and provide a platform for future warm dense matter studies. [ABSTRACT FROM AUTHOR]

Nonlinear structures formed by the coupled drift wave (DW) and ion acoustic waves (IAWs) are studied in a magnetized inhomogeneous collisionless bi-ion plasma with ions shear flow along the ambient magnetic field B = B 0 z ̂ . The electrons are assumed to follow double spectral index (r, q) distribution in which r shows the flat top nature, while q is responsible for the shape of the distribution at the tail. A nonlinear differential equation is derived, and its solutions in the form of double layers (DLs) and solitons are obtained in different limits. It is pointed out that the presence of (0.4%) protons in the oxygen plasma of ionosphere should not be ignored because acoustic speeds corresponding to oxygen and hydrogen ions have small ratio of about four and drift wave frequency may lie in the same range. It is found that only the rarefactive solitons can be formed by the nonlinear DW and IAWs in the inhomogeneous oxygen hydrogen (O–H) plasma. However, the theoretical model predicts that both compressive and rarefactive DLs may be formed. The linear instabilities of low-frequency electrostatic waves due to field-aligned shear flow of ions have also been investigated. [ABSTRACT FROM AUTHOR]

The four-wave mixing (FWM) mechanism for the generation of Terahertz (THz) radiation in magnetized-collisional clustered-plasma is studied. Clusters can trap the incident laser fields, leading to efficient energy transfer to plasma electrons and the creation of a strong nonlinear current. The size and density of clusters can be tuned to control the emission of THz radiation. The smaller clusters can bring about higher intensity THz radiation, while larger clusters can contribute to the broader THz frequency range. The THz radiation angular distribution patterns in the forward direction have been assessed, and the impact of plasma interaction length, cluster radius, and plasma electrons collision frequency on the generated THz wave patterns has been investigated. The FWM analysis highlights the importance of plasma clusters as well as magnetic fields in the efficient generation of THz emission. The model also takes into consideration how an induced electron current density initiated by DC external magnetic field can boost radiation power without changing the directivity diagram. [ABSTRACT FROM AUTHOR]

An analysis of reductive perturbation method (RPM) is presented to show why the solitary structures of non-linear ion acoustic waves (IAWs) cannot be obtained in magnetized electron ion plasma by employing this technique. In RPM, the non-linear Korteweg–de Vries equation is derived using stretched co-ordinates in the reference frame of the wave phase speed, considering the dispersion to be a higher-order effect that balances the non-linearity to produce a solitary structure. The maximum amplitude | Φ m | of the non-linear solitary wave turns out to be larger than one that contradicts the small amplitude approximation. In the presence of negative ions, the maximum amplitude satisfies the condition | Φ m | < 1. To elaborate these points, the results have been applied to an experimental plasma consisting of positive ions of xenon (Xe +) and negative ions of fluorene (F −) along with electrons. The amplitude and width of the solitary structures depend upon the ratio of the electron to positive ion density ( n e 0 n i 0 ). Since the non-linear coefficient turns out to be negative, rarefied (dip) solitons are formed in the magnetized Xe + − F − − e plasma. [ABSTRACT FROM AUTHOR]

The charged particle beams, such as electrons, ions, and plasma compression flow, have received considerable attention due to their applications in science and technology; therefore, studying the stability of these beams is of particular importance. Here, we examine theoretically the stability properties of a cold relativistic electron beam with a transverse velocity shear and non-uniform density profile. We consider a plane-parallel beam propagating along an external magnetic field and evaluate its macroscopic equilibrium state. We derive the dispersion relation of the slipping instability based on the linear electrodynamics of an inhomogeneous plasma and kinetic theory. In this model, the oscillation spectrum and the growth rate are derived by using the eikonal equation and the quasi-classical quantization rule. A linear velocity shear and a non-linear density gradient are assumed. Furthermore, we analyze numerically the dispersion relation of the slipping instability. The impacts of the inhomogeneity parameter and the relativistic factor on the properties of the slipping instability are discussed. [ABSTRACT FROM AUTHOR]

We have developed an experimental platform at the National Ignition Facility that employs colliding planar shocks to produce warm dense matter with uniform conditions and enable high-precision equation of state measurements. The platform uses simultaneous x-ray Thomson scattering and x-ray radiography to measure the density, electron temperature, and ionization state in warm dense matter. The experimental platform is designed to create a large volume of uniform plasma (approximately 700 × 700 × 150 μm3) at pressures approaching 100 Mbar and minimize the distribution of plasma conditions in the x-ray scattering volume, significantly improving the precision of the measurements. Here, we present the experimental design of the platform and compare hydrodynamic simulations to x-ray radiography data from initial experiments studying hydrocarbons, producing uniform densities within ±25% of the average probed condition. We show that the platform creates a homogeneous plasma that can be characterized using x-ray Thomson scattering. Thus, the new platform enables accurate measurements of plasma conditions necessary to test models for the equation of state and ionization potential depression in the warm dense matter regime. [ABSTRACT FROM AUTHOR]

We use numerical simulations to demonstrate that a source of bright collimated vortex γ-ray with large orbital angular momentum and small divergence can be achieved by irradiating an intense circularly polarized laser on a cone-fan target. In the all-optical setup, electron beam of energy with hundreds of MeV and also vortex laser pulse are formed. A considerable fraction of angular momentum of laser is converted to electron beam and furthermore to final vortex γ-ray, which are roughly 27.8% and 3%, respectively. The conversion efficiency of energy from laser to them is around 41% and 3.8%. Moreover, comparative simulations for different inner sizes of the cone reveal that there exists an optimal size making the highest angular momentum of γ-ray photons. For simulations with different laser modes, the circularly polarized laser is more appropriate rather than the Laguerre–Gaussian one to generate vortex γ-ray. [ABSTRACT FROM AUTHOR]

Formation of Korteweg-de Vries (KdV) solitons by nonlinear lower hybrid waves (LHWs) is not possible in usual electron ion plasma because a dispersive term does not have a suitable form. It is pointed out that the dispersion characteristics of electrostatic LHWs are modified in the presence of field-aligned shear flow to produce KdV solitons with negative electrostatic potential as it has been observed by satellites in the upper ionosphere. Plasma density decreases within the solitary structures. The parallel electron velocity shear v e 0 = v e 0 (x) z ̂ also gives rise to unstable waves in the intermediate frequency range in linear limit whereas the ambient magnetic field B 0 = B 0 z ̂ is assumed to be constant. The instability and structure size depend upon the electron parallel velocity shear parameter S e = 1 Ω e d v e 0 (x) d x (where Ω e is the electron gyrofrequency) and the propagation direction with respect to the ambient magnetic field B0. The theoretical model is applied to the upper ionosphere, and the estimated width of the structures turns out to be of the order of 70 m, which is closer to the observations. [ABSTRACT FROM AUTHOR]

Expansion of solar wind into the interplanetary space generates temperature anisotropy that cannot be justified by adiabatic fluid theory. Kinetic instabilities driven by the interplay between electrons and protons temperature anisotropy may be operative in order to explain the actual state of solar wind reported by satellite observations. Based on the temperature anisotropy, T ⊥ / T ∥ , and alternative different plasma beta, β, regimes of solar wind species, we investigate the unified wave spectrum where left-hand polarized electromagnetic proton cyclotron and electron firehose instabilities may co-exist or transit with each other. Linear stability analysis catches the co-existence/transition of these instabilities in the different propagation domain. A moment-based quasilinear approach is adopted to highlight the feedback effects of these instabilities on the initial distributions and also to validate the transition during the non-linear (or quasilinear) time-evolution of the instabilities. Looking at the solar wind observations, we assume a bi-Maxwellian dual core-halo electron and proton model that allows solar wind species temperatures to vary in time t in addition. By incorporating the radial expansion effects and inhomogeneities, our present findings may be applicable to the First Solar Parker Probe observations. [ABSTRACT FROM AUTHOR]

Electromagnetic ion cyclotron (EMIC) waves have been studied in this manuscript which are triggered by hot proton thermal anisotropy having energy ranging from 7 to 26 keV with a minimum resonant energy of 6.9 keV. However, an opposite effect can be observed for the hot protons for energy less than the minimum resonant energy. When the intensity of EMIC waves is large, the cold protons (ions) having low-energies can be energized by the EMIC waves. The possible reasons for this energization are the phase bunching of low energy ions with EMIC waves and the generation of electric fields at the relaxation time of substorm. As a consequence, these undetectable protons now become detectable, and the number density and temperature anisotropy of the protons also increase within the energy range from 1 to 100 eV. Accordingly, the helium ions are also energized by the EMIC waves. [ABSTRACT FROM AUTHOR]

The properties of materials under extreme conditions of pressure and density are of key interest to a number of fields, including planetary geophysics, materials science, and inertial confinement fusion. In geophysics, the equations of state of planetary materials, such as hydrogen and iron, under ultrahigh pressure and density provide a better understanding of their formation and interior structure [Celliers et al., "Insulator-metal transition in dense fluid deuterium," Science 361, 677–682 (2018) and Smith et al., "Equation of state of iron under core conditions of large rocky exoplanets," Nat. Astron. 2, 591–682 (2018)]. The processes of interest in these fields occur under conditions of high pressure (100 GPa–100 TPa), high temperature (>3000 K), and sometimes at high strain rates (>103 s−1) depending on the process. With the advent of high energy density (HED) facilities, such as the National Ignition Facility (NIF), Linear Coherent Light Source, Omega Laser Facility, and Z, these conditions are reachable and numerous experimental platforms have been developed. To measure compression under ultrahigh pressure, stepped targets are ramp-compressed and the sound velocity, measured by the velocity interferometer system for any reflector diagnostic technique, from which the stress-density of relevant materials is deduced at pulsed power [M. D. Knudson and M. P. Desjarlais, "High-precision shock wave measurements of deuterium: Evaluation of exchange-correlation functionals at the molecular-to-atomic transition," Phys. Rev. Lett. 118, 035501 (2017)] and laser [Smith et al., "Equation of state of iron under core conditions of large rocky exoplanets," Nat. Astron. 2, 591–682 (2018)] facilities. To measure strength under high pressure and strain rates, experimenters measure the growth of Rayleigh–Taylor instabilities using face-on radiography [Park et al., "Grain-size-independent plastic flow at ultrahigh pressures and strain rates," Phys. Rev. Lett. 114, 065502 (2015)]. The crystal structure of materials under high compression is measured by dynamic x-ray diffraction [Rygg et al., "X-ray diffraction at the national ignition facility," Rev. Sci. Instrum. 91, 043902 (2020) and McBride et al., "Phase transition lowering in dynamically compressed silicon," Nat. Phys. 15, 89–94 (2019)]. Medium range material temperatures (a few thousand degrees) can be measured by extended x-ray absorption fine structure techniques, Yaakobi et al., "Extended x-ray absorption fine structure measurements of laser-shocked V and Ti and crystal phase transformation in Ti," Phys. Rev. Lett. 92, 095504 (2004) and Ping et al., "Solid iron compressed up to 560 GPa," Phys. Rev. Lett. 111, 065501 (2013), whereas more extreme temperatures are measured using x-ray Thomson scattering or pyrometry. This manuscript will review the scientific motivations, experimental techniques, and the regimes that can be probed for the study of materials under extreme HED conditions. [ABSTRACT FROM AUTHOR]

Acceleration of a rest electron bunch in vacuum by a Laguerre–Gauss (LG) laser pulse is studied using three-dimensional test-particle simulations. It is found that the ponderomotive force and the phase synchronization process, with the help of each other, cause rest electrons to reach high energies in the laser interaction. The ponderomotive force due to the spatial distribution of a high-intensity LG laser pulse pushes electrons from the rest and accelerates them at first. Then, the accelerated electrons are trapped in the pulse and continue to gain more energy through the phase synchronization process. Unlike the interaction with a Gaussian laser pulse in which to maintain the beam quality was not possible without the intervention of an external factor, using the LG laser pulse reveals the feasibility of generating a GeV high-quality electron bunch with low spread in energy and radial deflection, without applying any external agent. [ABSTRACT FROM AUTHOR]

The linear dispersion relation and partial differential equations are derived for the electronegative plasma with heavier negative ions embedded in an ambient magnetic field. The appropriate transformation is used to study the nonlinear structures without introducing multi-scale expansion of various quantities. The nonlinear partial differential equation obtained sustains nonlinear structures like solitons and double layers. All the linear waves and the nonlinear structures like solitons and double layers are found to be modified predominantly under the influence of superthermal particles, density inhomogeneity, electron populations, and positive to negative heavy ion ratios. [ABSTRACT FROM AUTHOR]

It is pointed out that the criterion ω p e ≪ ω p + , ω p − (where ωpj is the plasma oscillation frequency of jth species and j = e, +, −) presented to define pure pair-ion plasma must also be fulfilled to ignore electron dynamics in positive-negative ion plasma. It is also suggested that the potassium (K+) plasma having negative ions of perfluoromethylcyclohexane (C 7 F 14 −) produced in Q-machine seems to have a significant number density of electrons; therefore, ion acoustic waves (IAW) may also exist. If T ± < T e and ions have field-aligned shear flow, the fluid theory predicts that the IAWs will be excited. The dimensions of experimentally produced plasma are small; therefore, the local theory is applicable only approximately. Since observations show that T e ≃ T ± in the laboratory performed experiments with positive-negative ions, the kinetic theory is also used to look for electron current-driven IAWs. Kinetic theory predicts that IAWs will be highly damped if electrons flow antiparallel to B0 in opposite direction with respect to positive ions. On the other hand, if electrons flow along B0 as is the case of ionospheric plasma, then IAWs become unstable. Thus, field-aligned shear flow of ions and parallel electron current can produce IAWs both in laboratory and astrophysical electron positive negative ion plasmas. [ABSTRACT FROM AUTHOR]

The relativistic effects on the dust grain charging are investigated by calculating the relativistic cross section by the orbit-limited motion (OLM) theory and relativistic Tsallis distribution function for currents carried by ions and electrons in nonequilibrium plasma. The dust grain electrical potential equation is derived in the dust grain charging process, and this nonlinear equation is solved by the numerical method. We indicate that the behavior of nonextensivity is in contrast to ions and electrons, and it is found that the density of species in plasma has the most influence on the degree of nonextensivity. We show that the degree of nonextensivity of the electron and the ion has significant effects on the relationship between dust grain electrical potential and dust density. As another result, it is indicated that by increasing the dust density, the dust particles will be seen as a component from ordinary multi-ionic plasma that shows collective behavior. By comparing the results in relativistic and nonrelativistic regimes, it is indicated that in the relativistic regime, the density of dust is limited, and the electrical potential of dust grains also varies, whereas in the nonrelativistic regime, the dust density is not limited, and the dust grain electrical potential tends to be constant in small amounts of dust density. [ABSTRACT FROM AUTHOR]

The characteristics of Bernstein waves like overlapping, propagation region, and harmonic structure are examined in the symmetric and asymmetric pair ion plasma. We observe that asymmetry (in temperature and mass) in pair ion plasma alters the dispersion curves and overlapping between the harmonics seems to vanish for such a plasma system. [ABSTRACT FROM AUTHOR]

The generation of high-intensity attosecond pulses by the interaction of two counterpropagating short laser pulses with underdense plasma is investigated. By using parallel fully kinetic particles in cell simulation, which shows the formation of relativistic flying mirrors in the wake wave of the intense driver laser pulse and the focusing reflection of the weak source pulse, it is demonstrated that intense attosecond pulses can be produced under the optimized conditions of plasma density and driver laser amplitude according to the relativistic similarity theory. In addition, it is shown that the frequency of the source pulse is upshifted by a factor from 10 to 80 corresponding to a reflected radiation wavelength from 20 to 164 nm which lies in the extreme ultraviolet region, while most of the energy lies around a frequency upshift of 20, in agreement with the measured Lorentz factor. The intensity of the main attosecond pulse is two orders higher than the source pulse intensity. [ABSTRACT FROM AUTHOR]

Nonlinear dissipative structures are studied in one and two dimensions in nonuniform magnetized plasmas with non-Maxwellian electrons. The dissipation is incorporated in the system through ion-neutral collisions. Employing the drift approximation, nonlinear drift waves are derived in 1D, whereas coupled drift-ion acoustic waves are derived in 2D in the weak nonlinearity limit. It is found that the ratio of the diamagnetic drift velocity to the velocity of nonlinear structure determines the nature (compressive or rarefactive) of the shock structure. The upper and lower bounds for velocity of the nonlinear shock structures are also found. It is noticed that the existence regimes for the drift shock waves in one and two dimensions for Cairns distributed electrons are very distinct from those with kappa distributed electrons. Interestingly, it is found that both compressive and rarefactive shock structures could be obtained for the one dimensional drift waves with kappa distributed electrons. [ABSTRACT FROM AUTHOR]

The diameter of a stem, a common origin point for streamers where the transition from the streamer to the leader takes place, has a significant effect on the simulation of streamer-to-leader transition. To measure the diameter of the stem, a schlieren system was established with the temporal and spatial resolutions of 5 μs and 70 μm, respectively. Experiments were conducted under positive lightning and switching impulses; the applied voltage, discharge current, and schlieren images were recorded synchronously. A method was proposed to measure the diameter of the stem based on the schlieren images, with which the stem diameter as a function of time was obtained. Moreover, the initial diameters of the stem under different conditions were obtained through the linear fitting. At last, a relation between the initial cross-sectional area of the stem and the discharge current was given within a certain range. [ABSTRACT FROM AUTHOR]

For realistic values of the Lundquist number in tokamak plasmas, 1/1 magnetic islands lead to the formation of a secondary thin current sheet, which breaks up into a chain of small magnetic islands, called plasmoids. The role of plasmoid dynamics during the sawtooth reconnection process in fusion plasmas remains an unresolved issue. In this study, systematic simulations are performed to investigate the resistive internal kink mode using the full resistive magnetohydrodynamics equations implemented in the NIMROD code in a simplified tokamak geometry. For Lundquist number S ≥ 1.6 × 10 7 , the secondary current sheet is found to be unstable to plasmoids during the nonlinear resistive kink mode evolution with a critical aspect ratio of the current sheet of ∼ 70. The merging of small plasmoids leads to the formation of a monster plasmoid that can significantly affect the primary island evolution. This may provide an explanation for the partial reconnection observed in sawtooth experiments. [ABSTRACT FROM AUTHOR]

The interaction potentials caused by a pair of moving test charges are studied in collisionless unmagnetized multi-ion plasmas, containing the electrons, singly ionized positive ions, and two negative ions. Starting from the Vlasov-Poisson coupled equations, a generalized electrostatic potential is obtained for a pair of test charges moving with constant velocities along the z-axis. Based on the speeds and correlations of test charges, the cases of slow, fast, and resonating test charge response are specifically studied and analyzed. If the test charges move with velocities much slower than the thermal speeds of all plasma species in multi-ion plasmas, then a short-range Debye-Hückel (DH) shielding potential appears to decay exponentially with the distance, whereas the long-range far-field (FF) potential varies as the inverse cube of the distance from test charges. The shielding phenomenon does not occur if the test charges move much faster than the plasma thermal speeds. However, the oscillatory wakefield (WF) potentials only exist behind the test charges when their speeds resonate with the speed of ion-acoustic waves. Numerically, it is revealed that the profiles of DH, FF, and WF potentials are significantly affected by the multi-ion plasma parameters and correlation effects. The results might be helpful for understanding the shielding phenomena, particle-particle and wave-particle interactions in multi-ion laboratory plasmas. [ABSTRACT FROM AUTHOR]

The linear and nonlinear properties of ion-acoustic rogons and associated modulational instability (MI) are studied in an unmagnetized dense electron-ion plasma, containing degenerate trapped/untrapped electrons and classical adiabatic ions. Solving the quantum hydrodynamic equations by using the standard multiscale reductive perturbation technique, a nonlinear Schrödinger equation is derived, which admits potential envelopes to be stable (unstable) against the perturbations for PQ < 0 (PQ > 0) . Here, P and Q are the dispersion and nonlinearity coefficients, respectively. It is numerically shown that for the vanishing ionic temperature ratio (σ = 0) , the parametric regime at perturbation wavelengths λ ≥ 2.5 λ eff (λ ≤ 2.5 λ eff ) is always modulationally stable (unstable); here, λeff is the effective screening length. Moreover, the finite ionic temperature (T i ≤ 10 eV) restores the modulational stability at relatively short wavelengths by confining MI within the perturbation range 4.5 λ eff ≤ λ ≤ 1.3 λ eff. The parameter Θ (= T e / 2 2 μ) shows the impact of the untrapped electrons which not only enhances (reduces) the angular frequency (group speed) of the envelope but also piles up the wave crests (energy) to produce the MI. Furthermore, due to degenerate trapped electrons, the instability domain gets widened in the limit PQ > 0 and leads to the onset of MI and unstable excitations. The study has important results for understanding the mechanism of MI and unstable modes in the context of astrophysical environments (white dwarfs, neutron stars, etc.,) and high density experiments. [ABSTRACT FROM AUTHOR]

It is pointed out that the presence of non-thermal electrons and protons in oxygen plasma of the ionosphere plays a destructive role in the formation of electrostatic structures by nonlinear ion acoustic waves (IAWs). On the other hand, linear electrostatic perturbations at different IAW frequencies are excited by the field-aligned shear flow in oxygen-hydrogen plasma of the upper ionosphere, and non-thermal electrons cause an increase in the growth rate. The excitation of IAW and formation of solitary structures in the ionosphere are investigated at altitudes of 600 km and 1000 km in the auroral region. [ABSTRACT FROM AUTHOR]

Coupled linear and nonlinear drift ion acoustic waves are studied in a dense degenerate, inhomogeneous electron positron ion plasma with a quantized magnetic field. The influence of the magnetic field quantization parameter, temperature degeneracy, density inhomogeneity, and positron concentration is elaborated with appropriate plasma parameters on linear and nonlinear drift ion acoustic wave propagation. The illustrations show that both linear and nonlinear wave characteristics are modified significantly by these effects. This investigation can be supportive to understand the planetary interiors, plasmonics, short pulsed petawatt laser technology, and the white dwarf stars. [ABSTRACT FROM AUTHOR]

By using the generalized expression for the plasma conductivity tensor, the general dispersion relation for the Bernstein waves is derived. To investigate the Bernstein waves for a weakly relativistic plasma, the Maxwell-Boltzmann-Juttner distribution function is employed. The propagation characteristics of the electron Bernstein waves (overlapping, propagation regions, and harmonic structures) are examined by using different values of η (ratio of rest mass energy to thermal energy) and ω p e ω c e (ratio of the plasma frequency to the cyclotron frequency). It is observed that the relativistic effects are the main cause of the harmonic overlapping which reduces the region of propagation. [ABSTRACT FROM AUTHOR]

By applying the Maxwell and quantum hydrodynamic equations, we have studied the parametric instabilities of stimulated Raman scattering (SRS) and stimulated Brillouin scattering (SBS) in an unmagnetized electron-ion quantum plasma. In this context, we have derived the nonlinear dispersion relations of the large-amplitude electromagnetic (EM) waves, the electrostatic electron plasma waves, and the ion-acoustic waves. The nonlinear evolution equations are then solved by utilizing the Fourier transform to obtain expressions for the three-wave decay and modulational instabilities with quantum corrections. It is found that the growth rate of the instabilities is a strong function of large-amplitude EM waves, and quantum effects due to Fermi pressure and quantum correlations stabilize both SRS and SBS instabilities. Expressions for the maximum growth rates attributed to SRS and SBS instabilities are also derived by ignoring the nonlinear correction shift on the frequency of EM waves. The relevance of nonlinear interaction of EM waves with a quantum dense astrophysical plasma is highlighted in the perspective of electron Fermi pressure and exchange-correlation effects, where the plasma density is high enough. [ABSTRACT FROM AUTHOR]

A formalism for nonlinear interaction of degenerate upper-hybrid waves (DUHWs) with degenerate ion-cyclotron waves (DICWs) and degenerate Alfven waves (DAWs) is revisited to account for quantum corrections owing to quantum Bohm potential, quantum exchange-correlations, and quantum statistical pressure. For this purpose, different nonlinear dispersion relations are derived with quantum settings. By using the phasor matching techniques, the growth rates of three wave decay and modulational instabilities are analyzed by identifying the nonlinear coupling of high-frequency DUHWs with low-frequency DICWs and DAWs. Numerically, it is revealed that parametric three wave decay and modulational instabilities are significantly influenced by the impact of Fermi pressure and exchange-correlation in a degenerate magnetoplasma. The present results are important to understand the dispersive properties of nonlinear waves and their mutual couplings at quantum scales in degenerate environments like white dwarfs, neutron stars, and magnetars. [ABSTRACT FROM AUTHOR]

We present the qualitative and quantitative use of laser-induced breakdown spectroscopy (LIBS) for the compositional characterization of the doped material of zinc (Zn) and tin (Sn) nanoparticles. The transition metal zinc doped tin nanoparticles are synthesized via co-precipitation and hydrothermal routes. A single laser operating at a wavelength at 532 nm is used to produce ablated plasma. The detailed analysis of the emission spectrum of ablated plasma reveals qualitative information which can be correlated with identification of the target material. The Boltzmann plot, standard two-line, and Saha-Boltzmann plot methods are used to determine the plasma temperature of nanoparticles, while the Stark broadening method and Saha-Boltzmann equation are used to estimate the electron number density of ablated plasma. Calibration free (CF-LIBS), one line calibration free (OLCF-LIBS), and calibration curve (CC-LIBS) approaches are used for the quantitative analysis of doped nano-structured materials with low and high concentrations. Using CF-LIBS, the quantitative analysis of the sample is carried out using Boltzmann plots, while using calibration based LIBS, quantitative results based on calibration curves are obtained, and limits of detection of nanoparticles are also determined using these calibration curves. Quantitative results estimated from calibration free and calibration based approaches are compared and validated with the results from standard techniques such as laser ablation time of flight (LA-TOF) spectroscopy and EDX. The present work establishes LIBS as an effective analytical tool for qualitative and quantitative estimation of the doped nanomaterials from atomic emission spectra. [ABSTRACT FROM AUTHOR]

Despite the extensive work done to characterize and improve the smoothness of ablator materials used in inertial confinement fusion (ICF), features indicative of seeded instability growth in these materials are still observed. A two-dimensional imaging velocimetry technique has been used on Omega to measure the velocity non-uniformities of shock fronts launched by indirect drive in the three ablator materials of current interest, glow-discharge polymer, beryllium, and high-density carbon ablators. Observed features are deviations from shock front planarity with amplitudes of a few tens of nanometers, local velocity variations of a few tens of m/s, and transverse spatial scales ranging from 5 to 200 μm. These data will help develop a full understanding of the effects of surface topography, dynamic material response, and internal heterogeneities on the stability of ICF capsules. For all three ablators, we have quantified perturbations at amplitudes that can dominate conventional surface roughness seeds to hydrodynamic instability. [ABSTRACT FROM AUTHOR]

The propagation characteristics of magnetoacoustic shock waves are investigated in an electron-ion dense magnetoplasma that accounts for spin − 1 2 electrons and geometrical effects within the framework of a two-fluid quantum magnetohydrodynamic model. For this purpose, we have employed the reductive perturbation technique and derived small-amplitude planar Korteweg de Vries Burgers (KdVB) and cylindrical KdVB equations. Numerically, cylindrical KdVB equations are analyzed by choosing the plasma parameters consistent with compact astrophysical systems. It is observed that the density, magnetic field, and viscosity are the parameters that ascertain significant modifications in the structure and propagation of magnetoacoustic shock waves. The amplitude of the shock wave becomes larger in the case of cylindrical geometry and propagates faster than that of planar shock waves. Furthermore, the results are compared with analytical solutions in the limit of earlier times to show an excellent agreement of the results. However, the magnetization energy is found to mitigate the amplitude of shock structures in a dense magnetoplasma where quantum spin effects cannot be ignored. [ABSTRACT FROM AUTHOR]

Stable electrostatic plasmon excitations due to propagation of Gaussian electron pulses are studied in a cylindrical nanowire of radius “a” and length “L”. For this purpose, we consider conduction electrons that follow the quantum hydrodynamical model to account for quantum statistics, quantum diffraction, and exchange-correlation effects in the presence of classical static ions. The use of the well-known Fourier transform technique and the Trivelpiece-Gould configuration leads to the generalized dispersion for plasmons with finite mode quantization effects via the radial and azimuthal mode indices, as well with quantum settings. The excitations of plasmon wakefield appear when the electron beam propagates with a constant velocity along the axial direction of nanowires. The stability conditions are also analyzed for the existence of wakefield excitations by solving three important inequalities using typical parameters of gold nanowires. The results may prove useful for understanding the plasmon excitations in quantum nanowires, where electrons can be trapped and accelerated in the wakefield to emit radiation in the extreme-ultraviolet range. [ABSTRACT FROM AUTHOR]

Self-absorption (SA) can drastically affect the emission signal which makes quantitative and, in extreme cases, qualitative investigations very challenging in laser induced plasma spectroscopy. In this study, plasma parameters are spectroscopically studied and SA in aluminum emission lines is investigated at various laser energies and gate delays. Q-switched Nd:YAG laser installed on LIBS2500plus system (1064 nm, 6 ns, 10 Hz) was used for ablation. The sample was ablated in air with different laser energies between 5 and 650 mJ, and spectra were recorded at various gate delays between 0 and 23.75 μs. Intensities of spectral lines Al I 308.2 and 309.3 nm were monitored for the range of laser energies and gate delays. The intensity of spectral lines was increased in response to the increasing laser energy. Rapid increase in intensities was observed for the first microsecond after plasma ignition. The maximum intensity of Al is observed at a gate delay of 1.25 μs. Plasma conditions are investigated on the basis of electron density and temperature in response to the change in laser energy and gate-delay. The electron temperature increased from 15 413 K to 20 200 K and the electron density from 5.0 × 1016 cm−3 to 3.5 × 1018 cm−3 with increase in laser energy from 5 to 650 mJ. The electron temperature is exponentially decreased from 26 733 K to 16 649 K and the electron density is reduced from 2.0 × 1017 cm−3 to 1.0 × 1016 cm−3 for increase in the gate delay from 0 to 23.75 μs. The self-absorption effect in resonant spectral lines of Al is estimated on the basis of SA coefficient calculated using FWHM of spectral lines. The highest values of SA coefficient are found for the lowest laser energies and longest gate delays. It states that the SA is significant when the plasma temperature is low and also, when plasma is least dense. It is fairly obvious to conclude that SA effects are least prevalent when the plasma plume is induced by high laser energies and measurements are made at short gate delays. [ABSTRACT FROM AUTHOR]

Head-on collision between ion acoustic shock waves (IASWs) and the consequences after collision are investigated considering the plasma system to be consisting of relativistic warm ions and nonextensive electrons and positrons, taking into account the effects of nonlinearity and dispersion. Two-sided KdV-Burger equations are derived employing the extended Poincar e ´ -Lighthill-Kuo method. The results reveal that the plasma parameters are responsible for the modification of the structures along with phase shifts of the shock waves. The nonlinearity effects on IASWs in a highly relativistic regime (HRR) become pronounced rather than the weakly relativistic regime (WRR). The phase shifts of IASWs are enhanced by the relativistic streaming factor and superthermality. The electrostatic IASWs become rarefactive depending on temperatures, kinematic viscosity, and superthermality in both WRR and HRR. The amplitudes of IASWs are increasing for WRR but decreasing for HRR due to increasing ion thermal velocities. Besides, the amplitudes of the solitons are detaining due to the increase in the positron concentration for the depopulation of ions. [ABSTRACT FROM AUTHOR]

We investigate electron self-injection in a donut bubble wakefield driven by a Laguerre-Gauss laser pulse. The present work discusses the electron capture by modeling the analytical donut bubble field. We discuss the self-injection of the electrons from plasma for various initial conditions and then compare the results. We show that the donut bubble can trap plasma electrons forming a hollow beam. We present the phase spaces and longitudinal momentum evolution for the trapped electrons in the bubble and discuss their characteristic behaviors and stability. It will be shown that the electrons self-injected in the front are ideal for applications in which a good stability and low energy spread are essential. [ABSTRACT FROM AUTHOR]

The vertical sizes of one-dimensional (1-D) and two dimensional (2-D) electrostatic solitons are estimated in the oxygen-hydrogen (O – H) and pure oxygen plasmas of the upper ionosphere taking into account the effects of non-extensive and trapped electrons. The field-aligned flow of oxygen ions is also considered. It is found that both electron trapping and non-extensivity play a constructive role in the formation of 1-D and 2-D solitary structures. The vertical size of the solitons is not known through observations, but here it is pointed out that the vertical size of these structures should be of the order of a few meters at the altitude of 800 km in the 1-D case. On the other hand, in the 2-D case, the vertical size is much larger than the horizontal size and it turns out to be of the order of a few kilometers, while the width is about a few hundred meters in agreement with the observations. [ABSTRACT FROM AUTHOR]

The shear flow in dust dynamics driven waves in combination with the dust-neutral drag is studied in a plasma comprising of ions, electrons, and dust. Non-thermal population of ions is considered, which has been observed by many satellite missions. It is found that the dissipative instability produced by dust sheared flow and dust-neutral drag gets modified by the presence of nonthermal ions. It is found that the dissipative instability enhances for the Cairns distribution, whereas the kappa distribution arrests the growth of this instability. In the nonlinear regime, the formation of vortices in the system is studied. It is found that the nonthermal population of ions significantly alters these structures in comparison with their Maxwellian counterpart. The results obtained in this paper may have relevance in the planetary magnetospheres where the dust particles are present and non-Maxwellian distribution of particles have been observed by Freja and Viking satellites. [ABSTRACT FROM AUTHOR]

It is pointed out that the ion acoustic waves (IAWs) are excited either by field-aligned shear flows or electron parallel current in oxygen-hydrogen (O-H) plasma of upper ionosphere. The purely growing D'Angelo instability becomes ion acoustic wave instability in the presence of second kind of ions within the framework of multi-fluid plasma model. On the other hand, kinetic theory is used to show that the growth rate of current driven ion acoustic wave overcomes the ion Landau damping. Out of four real roots corresponding to negative shear flow, the two roots can become unstable. Thus, ion acoustic waves at different but very low real frequencies appear in O-H plasma of ionosphere due to parallel shear flow and current, which is in agreement with satellite observations. [ABSTRACT FROM AUTHOR]

Analytical electron acoustic solitary wave (EASW) solution is investigated in the presence of periodic force for an unmagnetized plasma consisting of cold electron fluid, superthermal hot electrons, and stationary ions. Employing the reductive perturbation technique, the forced Kortegde Vries (KdV) equation is derived for electron acoustic waves. For the first time, an analytical solution for EASWs is derived in the presence of periodic force. The effects of the ratio between hot electron and cold electron number densities at equilibrium (α), spectral index (κ), speed of the traveling wave (M), strength (f0), and frequency (ω) of the periodic force are studied on the analytical solution of EASWs. It is observed that the parameters α, κ, M, f0, and ω affect significantly the structures of the electron acoustic solitary waves. The results may have relevance in laboratory plasmas as well as in space plasma environments. [ABSTRACT FROM AUTHOR]

Using kinetic approach, the effect of electron-ion collisions on Weibel instability has been investigated for three different types of anisotropic distribution functions (i.e., bi-kappa, bi-Maxellian, and product bi-kappa). It is found that the presence of electron-ion collisions has a negative effect on the growth rate of Weibel instability. By using analytical analysis, it has been found that the growth rate of the collisional plasma becomes negative if the electron-ion collision frequency becomes higher than the growth rate of the Weibel instability for a collisionless plasma while keeping all the other parameters same. The impact of electron-ion collisions has also been studied on the temperature anisotropy parameter τ(=T⊥/T‖)τ(=T⊥/T‖) threshold required for making the growth rate of the Weibel instability positive for all the three distribution functions. The illustrations show that for higher spectral index κ‖=κ>4κ‖=κ>4, the temperature anisotropy threshold is same for all the three distribution functions; however, for lower κ‖=κ<4κ‖=κ<4, the threshold conditions are different for the bi-kappa as compared to those found for the other two distribution functions. The boundaries between the stable and unstable regions of bi-kappa and product bi-kappa distributions have been found in the presence of collisions. In the presence of collisions, the boundary curve for product bi-kappa is similar to that we get in the absence of collisions. However, the temperature anisotropy threshold parameters are higher for collisional plasma as compared to those obtained for the collisionless plasma. The boundary curve for bi-kappa distribution function in the presence of collisions is significantly different from the boundary curve formed in the absence of collisions. In the presence of collisions, the temperature anisotropy threshold increases very rapidly when the spectral index is <2. [ABSTRACT FROM AUTHOR]

In this study, we developed an analytical model for the flow field in the Huels-type arc-heated wind tunnel (L2K) of the German Aerospace Center. This flow-field model can be used to accurately reproduce the discharge behavior in the heating section and expansion in the nozzle section of L2K. It includes the radiation transport and turbulent flow as well as thermochemical nonequilibrium models, which are tightly coupled with electric field calculations. In addition, we considered the turbulent diffusion model for the mass conservation of the species and performed numerical simulations for several cases with and without the turbulent diffusion model. Computations were conducted to obtain the general characteristics of an arc-heated flow containing an arc discharge and supersonic expansion. We verified that radiation and turbulence play important roles in the transfer of heat from the high-temperature core flow to the outer cold gas in the heating section of L2K. In addition, we performed parametric studies that involved varying the degree of turbulent diffusion. The results showed that turbulent diffusion has a large influence on the formation of the arc discharge in the heating section and on the enthalpy distribution at the nozzle exit. [ABSTRACT FROM AUTHOR]

A transverse gauss shape magnetic field with wide width is proposed for collimating the fast relativistic electron beam in laser irradiating plasmas, which is highlighted by the twodimensional particle-in-cell simulations, in particular, the effects of this magnetic field on the production and transport of fast electron beam. When the axial magnetic field is also present, it is found that the energy density of fast electrons can be enhanced greatly. For example, in the presence of 30MG axial magnetic field, it is enhanced by 3-4 times when the amplitude of the applied transverse magnetic field lies within the optimal regime 200-300MG comparable to that without the transverse magnetic field. Meanwhile, the divergence angle of the electron beam can be controlled and even decreased a little due to the better sandwich structure of the overall weakening magnetic field. The study implies that the proposed transverse magnetic field is helpful to obtain the high quality electron beam which is beneficial to the fast ignition in inertial confinement fusion. [ABSTRACT FROM AUTHOR]

The set of nonlinear partial differential equations for the coupled ion acoustic and drift waves is reduced to the KdV equation, which is finally transformed into the form of energy integral equation of a pseudo particle in small amplitude limit. It is pointed out that this approach is convenient for choosing appropriate plasma parameters and numerically obtaining drift solitary wave profiles as compared to the solution of the KdV equation, particularly, in non-uniform plasmas. Electrons are assumed to follow the Kappa distribution function. It is found that the solitons amplitude decreases corresponding to steeper density and temperature gradients because of the restriction on the validity of local approximation. Deviation of electrons from thermal equilibrium distribution is supportive for the formation of electrostatic solitary structures by the coupled nonlinear ion acoustic and drift waves. The estimates of the width of the solitons formed by these coupled nonlinear electrostatic waves in the F-region ionosphere are found to be a few meters in agreement with the satellite observations. [ABSTRACT FROM AUTHOR]

A Thomson backscattering experiment has been performed in a Penning-Malmberg device ELTRAP. To estimate the minimum sensitivity of diagnostics, we have computed the signal to noise ratio and found that the present bunch has a number density of 4.3x108 cm-3, which is three orders of magnitude less than the desired density of 1011 cm-3. To increase the signal level from the RF studies to the GHz range, the transmission efficiency from the rectangular waveguide orthogonally coupled to a prototype circular waveguide was experimentally analyzed on a testbench. It is observed that the lengths of waveguides play an important role in the transmission efficiency and return loss. When the length of the optimum rectangular waveguide (>2 λg=31 cm) is reduced to 7 cm, due to geometrical constraints of the ELTRAP device, consequently, the transmission efficiency is also reduced and shifts away from the maximum 3 GHz operating frequency. The useful frequency band is then reduced with the increasing length of the prototype circular waveguide (102 cm). Using the electromagnetic Particle-In-Cell simulations involving the electron cyclotron resonance heating (ECRH), we have utilized a magnetic field of 0.1 T resonating with 2.8 GHz RF drive during each time step (1 ps) having the power level of 0.04 V to the middle and to the end of the trap. A more efficient increase in the radial and azimuthal temperature profiles is observed as compared to the axial temperature profile. The reason is the use of ECRH to heat electrons in cyclotron motion, which is completely kinetic and magnetron motion which is almost entirely potential based. The axial motion interchanges in between the kinetic and potential with a slight enhancement in axial motion to maintain the total canonical angular momentum conserved. The temperature profile of the confined electron plasma increases with the variation of densities from 5x107m-3 to 1012m-3. The major heating effect occurs when the RF power is injected from the position close to one end with respect to the middle position of the trap. [ABSTRACT FROM AUTHOR]

The dynamics of dust ion acoustic waves (DIAWs) is investigated in a magnetized dusty plasma whose constituents are cold ions, superthermal electrons, and dust particles in the framework of a damped Zakharov-Kuznetsov (dZK) equation in the presence of externally applied periodic force. The dZK equation is derived employing the standard reductive perturbation technique. The effect of dust ion collision on the quasiperiodic and chaotic motion of dust ion acoustic waves is discussed. It is observed that the collision frequency νid0 plays the role of a switching parameter from the quasiperiodic route to chaos for the DIAWs. [ABSTRACT FROM AUTHOR]

The formation and propagation of fully nonlinear dust-acoustic (DA) waves and shocks are studied in a non-Maxwellian thermal dusty plasma which is composed of Maxwellian electrons and nonthermal energetic ions with a neutralizing background of negatively charged dust grains. For this purpose, we have solved dust dynamical equations along with quasineutrality equation by using a diagonalization matrix technique. A set of two characteristic wave equations is obtained, which admits both analytical and numerical solutions. Taylor expansion in the small-amplitude limit (Φ ≪ 1) leads to nonlinear effective phase and shock speeds accounting for nonthermal energetic ions. It is numerically shown that DA pulses can be developed into DA shocklets involving the negative electrostatic potential, dust fluid velocity, and dust number density. These structures are significantly influenced by the ion-nonthermality, dust thermal correction, and temporal variations. However, the amplitudes of solitary and shock waves are found smaller in case of Cairns-distributed ions as compared to Kappa-distributed ions due to smaller linear and nonlinear effective phase speeds that cause smaller nonlinearity effects. The present results should be useful for understanding the nonlinear characteristics of large-amplitude DA excitations and nonstationary shocklets in a laboratory non-Maxwellian dusty plasma, where nonthermal energetic ions are present in addition to Maxwellian electrons. [ABSTRACT FROM AUTHOR]

Relying on the density functional theory, we have examined the impact of electron exchange-correlations on the nonlinear dispersion relations and associated parametric instabilities induced by nonlinear couplings of high-frequency quantum upper-hybrid waves (QUHWs) with different low-frequency waves, like quantum lower-hybrid waves (QLHWs), quantum ion-cyclotron waves (QICWs), and quantum Alfvén waves (QAWs) in a dense quantum magnetoplasma. For theoretical description of waves, we make use of quantum hydrodynamic equations to account for the electron exchange-correlation and Bohm potentials, strongly dependent on the density fluctuations. At quantum scales, nonlinear dispersion equations are derived for QUHWs, QICWs, QLHWs, and QAWs and then Fourier transformed for obtaining the nonlinear dispersion relations and growth rates involving the three wave decay and modulational instabilities in dense quantum magnetoplasmas. The relevance to nonlinear interactions due to high- and low-frequency waves in perspective of electron exchange-correlations is highlighted. [ABSTRACT FROM AUTHOR]

The effect of electron trapping in an electron-positron-ion plasma is modeled with κ-distributed electrons. The trapped electron number density is truncated to some finite order of the electrostatic potential Φ. Small amplitude solitary structures with Sagdeev potential approach and reductive perturbation method (through Schamel equation) are found to be modified under the impact of superthermality index κ and trapping efficiency β. A modified Schamel equation which gives rise to the small amplitude double layers (SIADLs) is obtained. The role of various plasma parameters in particular, the superthermality index, the positron concentration, and the electron trapping efficiency on the small amplitude ion acoustic double layers (SIADLs) has been investigated. It can be inferred from this investigation that these parameters play modifying character in the formation of nonlinear structures like solitary waves and SIADLs in e-p-i plasma. [ABSTRACT FROM AUTHOR]

Propagation characteristics and interaction phenomena among the dust acoustic (DA) solitons in unmagnetized dusty plasmas are studied. The plasma is composed of negatively charged mobile dust, Boltzmann distributed electrons, and nonthermally distributed cold and hot ions. The extended Poincaré-Lighthill-Kuo method is employed to derive the two-sided Korteweg-de Vries (KdV) equations. The solutions of the KdV equations are constructed using the Hirota bilinear method both for single- and multi-solitons. The phase shifts are determined for the interactions among the two-, four-, and six-DA solitons. The effects of plasma parameters on the head-on collisions of the DA single- and multi-solitons and their corresponding phase shifts are investigated. [ABSTRACT FROM AUTHOR]

A comparative study of the interactions between nonlinear ion acoustic solitary waves (IASWs) propagating toward each other, and the electrostatic nonlinear propagation of IASWs, both for the weakly and relativistic regimes consisting of relativistic warm ions, nonthermal electrons and positrons, is carried out. Two-sided Korteweg--de Vries (KdV) equations are derived using the extended Poincar-e-Lighthill-Kuo (PLK) method to reveal the physical issues concerned. The effects of positron concentration, ion-electron temperature ratio, electron-positron temperature ratio, relativistic streaming factor, the population of electron, and positron nonthermality on the electrostatic resonances and their phase shifts are investigated for both regimes. It is found that the plasma parameters significantly modify the phase shifts, electrostatic resonances, hump-shaped electrostatic potential profiles, and the electric fields on the nonlinear propagation characteristics of IASWs. The results obtained may be useful for clarifications of interaction between IASWs in astrophysical and laboratory plasmas, especially in pulsar magnetosphere, laser produced, inertial confinement plasmas, and pulsar relativistic winds with supernova ejecta that produce nonthermal electrons, positrons and relativistic ions. Published by AIP Publishing. [ABSTRACT FROM AUTHOR]