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Some typical electrons trajectories around a bubble regime in intense laser plasma interaction are investigated theoretically. By considering a modification of the fields and ellipsoid bubble shape due to the presence of residual electrons in the bubble regime, we study in detail the electrons nonlinear dynamics with or without laser pulse. To examine the electron dynamical behaviors, a set of typical electrons, which locate initially at the front of the bubble, on the transverse edge and at the bottom of the bubble respectively, are chosen for study. It is found that the range of trapped electrons in the case with laser pulse is a little narrower than that without laser pulse. The partial phase portraits for electrons around the bubble are presented numerically and their characteristic behaviors are discussed theoretically. Implication of our results on the high quality electron beam generation is also discussed briefly. [ABSTRACT FROM AUTHOR]

The combinational laser radiation pressure and plasma bubble fields to accelerate protons are researched through theoretical analysis and numerical simulations. The dephasing length of the accelerated protons bunch in the front of the bubble and the density gradient effect of background plasma on the accelerating phase are analyzed in detail theoretically. The radiation damping effect on the accelerated protons energy is also considered. And it is demonstrated by two-dimensional particle-in-cell simulations that the protons bunch energy can be increased by using the background plasma with negative density gradient. However, radiation damping makes the maximal energy of the accelerated protons a little reduction. [ABSTRACT FROM AUTHOR]

Linear and nonlinear analysis of coupled drift and acoustic mode is presented in an inhomogeneous electron-ion plasma with κ-distributed electrons. A linear dispersion relation is found which shows that the phase speed of both the drift wave and the ion acoustic wave decreases in the presence of superthermal electrons. Several limiting cases are also discussed. In the nonlinear regime, stationary solutions in the form of dipolar and monopolar vortices are obtained. It is shown that the condition for the boundedness of the solution implies that the speed of drift wave driven vortices reduces with increase in superthermality effect. Ignoring density inhomogeniety, it is investigated that the lower and upper limits on the speed of the ion acoustic driven vortices spread with the inclusion of high energy electrons. The importance of results with reference to space plasmas is also pointed out. [ABSTRACT FROM AUTHOR]

The linear and nonlinear properties of low-frequency electrostatic excitations of charged dust particles (or defects) in a dense collisionless, unmagnetized Thomas-Fermi plasma are investigated. A fully ionized three-component model plasma consisting of electrons, ions, and negatively charged massive dust grains is considered. Electrons and ions are assumed to be in a degenerate quantum state, obeying the Thomas-Fermi density distribution, whereas the inertial dust component is described by a set of classical fluid equations. Considering large-amplitude stationary profile travelling-waves in a moving reference frame, the fluid evolution equations are reduced to a pseudo-energy-balance equation, involving a Sagdeev-type potential function. The analysis describes the dynamics of supersonic dust-acoustic solitary waves in Thomas-Fermi plasmas, and provides exact predictions for their dynamical characteristics, whose dependence on relevant parameters (namely, the ion-to-electron Fermi temperature ratio, and the dust concentration) is investigated. An alternative route is also adopted, by assuming weakly varying small-amplitude disturbances off equilibrium, and then adopting a multiscale perturbation technique to derive a Korteweg-de Vries equation for the electrostatic potential, and finally solving in terms for electric potential pulses (electrostatic solitons). A critical comparison between the two methods reveals that they agree exactly in the small-amplitude, weakly superacoustic limit. The dust concentration (Havnes) parameter h=Zd0nd0/ne0 affects the propagation characteristics by modifying the phase speed, as well as the electron/ion Fermi temperatures. Our results aim at elucidating the characteristics of electrostatic excitations in dust-contaminated dense plasmas, e.g., in metallic electronic devices, and also arguably in supernova environments, where charged dust defects may occur in the quantum plasma regime. [ABSTRACT FROM AUTHOR]

We present spatial characteristics of the lithium fluoride plasma generated by the fundamental and second harmonic of a Nd:YAG laser. The plume emission has been recorded spatially using five spectrometers covering the spectral region from 200 nm to 720 nm. The electron density is measured from the Stark broadened line profile of the line at 610.37 nm, whereas the plasma temperature has been determined using the Boltzmann plot method including all the observed spectral lines of lithium. Both the plasma parameters; electron density and plasma temperature decrease with the increase of the distance from the target surface. The thermal conduction towards the target, the radiative cooling of the plasma, and the conversion of thermal energy into kinetic energy are the main mechanisms responsible for the spatially decrease of the plasma parameters. [ABSTRACT FROM AUTHOR]

Using the Vlasov-Maxwell's model, the generalized dispersion relations for parallel propagating electromagnetic modes (R- and L-waves) and electrostatic mode (Langmuir wave) for weakly magnetized relativistic degenerate plasma are derived. The propagation characteristics of these modes are analyzed both analytically and graphically in order to highlight the relativistic and the ambient magnetic field effects in different degenerate plasma environments. Furthermore, the analytical expressions of these modes are extracted for the limiting cases, i.e., non-relativistic (pF/moc<1) and ultra-relativistic (pF/moc>1). It is noted that the relativistic effects shift the cut-off point towards the lower value of frequency and resultantly broaden the propagation domain. Moreover, the cut-off point of R-wave/L-wave move towards the higher/lower frequency as the strength of ambient magnetic field is increased. The shifting of frequency due to the ambient magnetic field becomes more prominent in the non-relativistic regime than in the highly relativistic one because the relativistic effect suppresses the contribution of the ambient magnetic field. [ABSTRACT FROM AUTHOR]

Ion accoustic waves or phonon modes are studied with orbital angular momentum (OAM) in an unmagnetized collissionless uniform plasma, whose constituents are the Boltzmann electrons and inertial ions. For this purpose, we have employed the fluid equations to obtain a paraxial equation in terms of ion density perturbations and discussed its Gaussian beam and Laguerre-Gauss (LG) beam solutions. Furthermore, an approximate solution for the electrostatic potential problem is presented, allowing to express the components of the electric field in terms of LG potential perturbations. The energy flux due to phonons is also calculated and the corresponding OAM is derived. Numerically, it is shown that the parameters such as azimuthal angle, radial and angular mode numbers, and beam waist, strongly modify the profiles of the phonon LG potential. The present results should be helpful in understanding the phonon mode excitations produced by Brillouin backscattering of laser beams in a uniform plasma. [ABSTRACT FROM AUTHOR]

The role of nanosecond duration pre-pulse pedestal (Amplified Spontaneous Emission (ASE) pre-pulse) in the propagation of 45 fs, 4 TW Ti:Sapphire laser pulse through a helium gas jet target has been investigated. We observed that the pre-pulse pedestal of about 1 ns duration and intensity 3 × 1012 W/cm2 creates pre-formed plasma with optical guiding channel like structure in the gas-jet at density around 3 × 1019 cm-3. Guiding of the 45 fs laser pulse (IL = 3 × 1018 W/cm2) in the pre-formed plasma channel, over a distance much longer than the Rayleigh length was also observed. The guiding of the laser pulse resulted in the generation of high energy electron beam by laser wake-field acceleration of self-injected electrons. The accelerated electron beam was quasi-monoenergetic with peak energy up to 50 MeV, low divergence in the range of 3-6 mrad, and bunch charge up to 100 pC. [ABSTRACT FROM AUTHOR]

Bernstein mode for a relativistic degenerate electron plasma is investigated. Using relativistic Vlasov-Maxwell equations, a general expression for the conductivity tensor is derived and then employing Fermi-Dirac distribution function a generalized dispersion relation for the Bernstein mode is obtained. Two limiting cases, i.e., non-relativistic and ultra-relativistic are discussed. The dispersion relations obtained are also graphically presented for some specific values of the parameters depicting how the propagation characteristics of Bernstein waves as well as the Upper Hybrid oscillations are modified with the increase in plasma number density. [ABSTRACT FROM AUTHOR]

We present new studies on the optical emission spectra of the laser produced Al 6063 alloy plasma generated by the 1064 nm Nd: YAG laser. The spectrum reveals Rydberg transitions; nd 2D3/2,5/2 → 3p 2P1/2,3/2 (n = 3 - 8), ns 2S1/2 → 3p 2P1/2,3/2 (n = 4-6), and the dominant spectral lines of the other constituent elements. We have extracted the relative abundance of the impurities using the relative intensity ratio method. Besides, we have calculated the electron temperature (∼7580 K) from the Boltzmann plot method and the electron number densities (∼1.4 × 1017/cm3) from the Stark widths of the aluminum spectral lines. The plasma parameters determined in the present work are in agreement with that reported in the literature. The molecular vibrational transitions of the AlO free radical associated with the B 2∑→X 2∑ band system have also been identified. [ABSTRACT FROM AUTHOR]

We present a comparative study of the collinear and orthogonal pre-ablation dual pulse configurations of laser induced breakdown spectroscopy (LIBS) of silver using Nd:YAG lasers. The effect of the inter-pulse delay and the ratio of the laser pulse energies on the signal intensity enhancement for both the dual pulse configurations have been investigated. Using the first laser at 532 nm and second laser at 1064 nm delayed by 5 μs, we achieved nearly 2 times signal enhancement in the collinear double-pulsed configuration and nearly 12 times in the pre-ablation orthogonal configuration as compared to SP LIBS. It is ascertained that at the optimized value of the inter-pulse delay between the two lasers, the intensity ratio of the neutral silver lines follows the local thermo dynamical equilibrium (LTE) condition and it is also in excellent agreement with that of the relative transitions probabilities ratio listed in the NIST data base. [ABSTRACT FROM AUTHOR]

The parametric decay instability of a dust ion acoustic wave into low-frequency electrostatic dust-lower-hybrid and electromagnetic shear Alfvén waves has been investigated in detail in an inhomogeneous cold quantum dusty plasma in the presence of external/ambient uniform magnetic field. The quantum magnetohydrodynamic model of plasmas with quantum effect arising through the Bohm potential and Fermi degenerate pressure has been employed in order to find the linear and nonlinear responses of the plasma particles for three-wave nonlinear coupling in a dusty magnetoplasma. A relatively high frequency electrostatic dust ion acoustic wave has been taken as the pump wave. It couples with two other low-frequency internal possible modes of the dusty magnetoplasma, viz., the dust-lower-hybrid and shear Alfvén waves. The nonlinear dispersion relation of the dust-lower-hybrid wave has been solved to obtain the growth rate of the parametric decay instability. The growth rate is at a maximum for a small value of the external magnetic field B0. It is noted that the growth rate is proportional to the unperturbed electron number density noe and is independent of inhomogeneity beyond Le=2 cm. An extraordinary growth rate is observed with the quantum effect. [ABSTRACT FROM AUTHOR]

Line emission and broadband x-ray sources with x-ray energies above 10 keV have been investigated using a range of calibrated x-ray detectors for use as x-ray backlighters in high energy density (HED) experiments. The conversion efficiency of short- and long-pulse driven Mo and Ag line-emission backlighters at 17 and 22 keV was measured to investigate the crossover region between short- and long-pulse conversion efficiency. It was found that significant 17 and 22 keV line emissions were observed using a 3 ω, 1 ns long-pulse drive for Mo and Ag targets and a comparison between the measured Mo x-ray spectrum and calculations using an atomic physics code suggests that the line emission is due to thermal emission from N-like Mo atoms. Electron temperatures derived from fits to the continuum region of the x-ray spectra agree well with the Thot scaling as 100×(Iλ2)1/3. The continuum emissions from empty and 1 atm Kr-filled imploded CH shell targets were also measured for the use as broadband backlighters. [ABSTRACT FROM AUTHOR]

Any canonical transformation of Hamiltonian equations is symplectic, and any area-preserving transformation in 2D is a symplectomorphism. Based on these, a discrete symplectic map and its continuous symplectic analog are derived for forward magnetic field line trajectories in natural canonical coordinates. The unperturbed axisymmetric Hamiltonian for magnetic field lines is constructed from the experimental data in the DIII-D [J. L. Luxon and L. E. Davis, Fusion Technol. 8, 441 (1985)]. The equilibrium Hamiltonian is a highly accurate, analytic, and realistic representation of the magnetic geometry of the DIII-D. These symplectic mathematical maps are used to calculate the magnetic footprint on the inboard collector plate in the DIII-D. Internal statistical topological noise and field errors are irreducible and ubiquitous in magnetic confinement schemes for fusion. It is important to know the stochasticity and magnetic footprint from noise and error fields. The estimates of the spectrum and mode amplitudes of the spatial topological noise and magnetic errors in the DIII-D are used as magnetic perturbation. The discrete and continuous symplectic maps are used to calculate the magnetic footprint on the inboard collector plate of the DIII-D by inverting the natural coordinates to physical coordinates. The combination of highly accurate equilibrium generating function, natural canonical coordinates, symplecticity, and small step-size together gives a very accurate calculation of magnetic footprint. Radial variation of magnetic perturbation and the response of plasma to perturbation are not included. The inboard footprint from noise and errors are dominated by m=3, n=1 mode. The footprint is in the form of a toroidally winding helical strip. The width of stochastic layer scales as 12 power of amplitude. The area of footprint scales as first power of amplitude. The physical parameters such as toroidal angle, length, and poloidal angle covered before striking, and the safety factor all have fractal structure. The average field diffusion near the X-point for lines that strike and that do not strike differs by about three to four orders of magnitude. The magnetic footprint gives the maximal bounds on size and heat flux density on collector plate. [ABSTRACT FROM AUTHOR]

The effect of collision on small amplitude dust-acoustic waves is investigated for a plasma with positively charged dust grains. Taking into account the presence of different electron populations in thermal equilibrium, a modified Korteweg-de Vries equation is established. The existence conditions and nature of the waves, i.e., rarefactive or compressive, are found to be mainly dependent on the temperature and the density of the cold electrons. The present model is used to understand the salient features of the fully nonlinear dust-acoustic waves in the lower region of the Earth's ionosphere, at an altitude of ∼85 km with the presence of an external heating source. [ABSTRACT FROM AUTHOR]

In this paper, a charged multiwalled carbon nanotube (MWCNT), which is surrounded by charged nanoparticles, is modeled as a cylindrical shell of electron-ion-dust plasma. By employing the classical electrodynamics formulations and linearized hydrodynamic model, the dispersion relation of the dust-ion-acoustic wave oscillations in the composed system is investigated. We obtain a new low-frequency electrostatic excitation in the MWCNTs, i.e., dust-ion-acoustic wave oscillations. [ABSTRACT FROM AUTHOR]

Drift wave is studied in pair-ion plasmas in the presence of electrons using the Vlasov-Poisson set of equations. The growth rate of this universal instability depends on the concentration of electrons. The real frequency and the growth rate are reduced as the number density of electrons decreases. If the laboratory produced pair-ion plasmas contain relatively small amount of electrons then very low frequency almost stable drift waves can be produced which will indicate that the plasma is not a pure pair-ion plasma. The present investigation can be useful for future experiments on pair-ion plasmas and low density low temperature industrial plasmas which contain negative ions. [ABSTRACT FROM AUTHOR]

Electron plasma waves carrying orbital angular momentum are investigated in an unmagnetized collisionless plasma composed of inertial electrons and static ions. For this purpose, the usual plasmon dispersion relation is employed to derive an approximate paraxial equation. The latter is analyzed with a Gaussian beam solution. For a finite angular momentum associated with the plasmon, Laguerre–Gaussian (LG) solutions are employed for solving the electrostatic potential problem which gives approximate solution and is valid for plasmon beams in the paraxial approximation. The LG potential determines the electric field components and energy flux of plasmons with finite angular momentum. Numerical illustrations show that the radial and angular mode numbers strongly modify the profiles of the LG potential. [ABSTRACT FROM AUTHOR]

The Debye–Hückel and oscillatory wake potentials caused by a test charge are studied in a multi-ion dusty plasma, whose constituents are the Boltzmann distributed electrons and light positive ions, the heavy mobile negative ions, and static but charge fluctuating dust particles. For this purpose, fluid equations are employed to obtain the dielectric constant of the dust-negative-ion acoustic wave involving the negative ions and dust charge fluctuation effects. Theoretical and numerical investigations have revealed the modification in the Debye–Hückel and wake potentials due to the effects of dust relaxation rate, dust absorption frequency, dust grain radius, and negative ion temperature. The present results should be important to form new materials in the presence of negative ions in laboratory as well as dust coagulation/agglomeration in space dusty plasmas. [ABSTRACT FROM AUTHOR]

The existence of small amplitude quantum ion-acoustic double layers is studied in an unmagnetized dense electron-positron-ion plasma. For this purpose, the quantum hydrodynamic model is employed to derive a deformed Korteweg–de Vries (dKdV) equation. The steady state double layer solution of dKdV equation is obtained and its dependence on various parameters is discussed. It is found that only compressive double layers can exist in such plasmas. The analytical and numerical studies reveal that the quantum ion-acoustic double layer structures strongly depend on quantum diffraction effects and positron number density. [ABSTRACT FROM AUTHOR]

The coordinates of the area-preserving map equations for integration of magnetic field line trajectories in divertor tokamaks can be any coordinates for which a transformation to (ψt,θ,φ) coordinates exists [A. Punjabi, H. Ali, T. Evans, and A. Boozer, Phys. Lett. A 364, 140 (2007)]. ψt is toroidal magnetic flux, θ is poloidal angle, and φ is toroidal angle. This freedom is exploited to construct the symmetric quartic map such that the only parameter that determines magnetic geometry is the elongation of the separatrix surface. The poloidal flux inside the separatrix, the safety factor as a function of normalized minor radius, and the magnetic perturbation from the symplectic discretization are all held constant, and only the elongation is κ varied. The width of stochastic layer, the area, and the fractal dimension of the magnetic footprint and the average radial diffusion coefficient of magnetic field lines from the stochastic layer; and how these quantities scale with κ is calculated. The symmetric quartic map gives the correct scalings which are consistent with the scalings of coordinates with κ. The effects of m=1, n=±1 internal perturbation with the amplitude that is expected to occur in tokamaks are calculated by adding a term [H. Ali, A. Punjabi, A. H. Boozer, and T. Evans, Phys. Plasmas 11, 1908 (2004)] to the symmetric quartic map. In this case, the width of stochastic layer scales as 0.35 power of κ. The area of the footprint is roughly constant. The average radial diffusion coefficient of field lines near the X-point scales linearly with κ. The low mn perturbation changes the quasisymmetric structure of the footprint, and reorganizes it into a single, large scale, asymmetric structure. The symmetric quartic map is combined with the dipole map [A. Punjabi, H. Ali, and A. H. Boozer, Phys. Plasmas 10, 3992 (2003)] to calculate the effects of magnetic perturbation from a current carrying coil. The coil position and coil current coil are constant. The dipole perturbation enhances the magnetic shear. The width of the stochastic layer scales exponentially with κ. The area of the footprint decreases as the κ increases. The radial diffusion coefficient of field lines scales exponentially with κ. The dipole perturbation changes the topology of the footprint. It breaks up the toroidally spiraling footprint into a number of separate asymmetric toroidal strips. Practical applications of the symmetric quartic map to elongated divertor tokamak plasmas are suggested. [ABSTRACT FROM AUTHOR]

Streaming instabilities in electron-positron-ion plasmas are investigated using kinetic approach in several different limits. The effects of the variation of background temperatures of electrons Teo and positrons Tpo on the growth rates are also presented for the case of ion beam streaming into electron-positron plasmas and positrons beam streaming into electron-ion plasmas. It is noticed that the increase of number density of positrons gives a destabilizing trend to the electrostatic perturbations in the system. [ABSTRACT FROM AUTHOR]

The quantum hydrodynamical model is employed to investigate the nonlinear properties of the quantum dust acoustic waves in a magnetized dusty plasma composed of inertialess electrons, ions, and mobile positive/negative charged dust particles. For this purpose, a quantum Zakharov–Kuznetsov equation is derived and the basic features of the electrostatic excitations are investigated by applying the direct method. It is found that positive and negative bell-shaped solitary pulses become explosive pulses depending mainly upon the angles of propagation and dust polarity. Furthermore, the effects due to nondimensional quantum parameter and the external magnetic field are examined on the width of the quantum dust acoustic solitary pulses. The relevance of the present results to semiconductor quantum wells is mentioned. [ABSTRACT FROM AUTHOR]

A new approach to integration of magnetic field lines in divertor tokamaks is proposed. In this approach, an analytic equilibrium generating function (EGF) is constructed in natural canonical coordinates (ψ,θ) from experimental data from a Grad–Shafranov equilibrium solver for a tokamak. ψ is the toroidal magnetic flux and θ is the poloidal angle. Natural canonical coordinates (ψ,θ,φ) can be transformed to physical position (R,Z,φ) using a canonical transformation. (R,Z,φ) are cylindrical coordinates. Another canonical transformation is used to construct a symplectic map for integration of magnetic field lines. Trajectories of field lines calculated from this symplectic map in natural canonical coordinates can be transformed to trajectories in real physical space. Unlike in magnetic coordinates [O. Kerwin, A. Punjabi, and H. Ali, Phys. Plasmas 15, 072504 (2008)], the symplectic map in natural canonical coordinates can integrate trajectories across the separatrix surface, and at the same time, give trajectories in physical space. Unlike symplectic maps in physical coordinates (x,y) or (R,Z), the continuous analog of a symplectic map in natural canonical coordinates does not distort trajectories in toroidal planes intervening the discrete map. This approach is applied to the DIII-D tokamak [J. L. Luxon and L. E. Davis, Fusion Technol. 8, 441 (1985)]. The EGF for the DIII-D gives quite an accurate representation of equilibrium magnetic surfaces close to the separatrix surface. This new approach is applied to demonstrate the sensitivity of stochastic broadening using a set of perturbations that generically approximate the size of the field errors and statistical topological noise expected in a poloidally diverted tokamak. Plans for future application of this approach are discussed. [ABSTRACT FROM AUTHOR]

The fundamental mode frequency of a magnetically insulated transmission line oscillator is investigated theoretically by the equivalent circuit method, and an exact theoretical formula about the fundamental mode frequency is given. The theoretical results are compared with the simulation and experimental results, which shows that the relative error, which is calculated according to the theoretical and simulation frequencies, is less than 3%, so the validity of the theoretical formula is verified. [ABSTRACT FROM AUTHOR]

Theoretical and numerical studies are performed for the nonlinear structures (explosive, solitons, and shock) in quantum electron-positron-ion magnetoplasmas. For this purpose, the reductive perturbation method is employed to the quantum hydrodynamical equations and the Poisson equation, obtaining extended quantum Zakharov–Kuznetsov equation. The latter has been solved using the generalized expansion method to obtain a set of analytical solutions, which reflects the possibility of the propagation of various nonlinear structures. The relevance of the present investigation to the white dwarfs is highlighted. [ABSTRACT FROM AUTHOR]

A coupled linear dispersion relation for the basic electrostatic and electromagnetic waves in the ultracold nonuniform magnetized dense plasmas has been obtained which interestingly is analogous to the classical case. The scales of macroscopic phenomena and the interparticle quantum interactions are discussed. It is important to point out that hydrodynamic models cannot take into account strong quantum effects and they are not applicable to very dense plasmas. The analysis is presented with applications to dense plasmas which are relevant to both laboratory and astrophysical environments. [ABSTRACT FROM AUTHOR]

A highly accurate calculation of the magnetic field line Hamiltonian in DIII-D [J. L. Luxon and L. E. Davis, Fusion Technol. 8, 441 (1985)] is made from piecewise analytic equilibrium fit data for shot 115467 3000 ms. The safety factor calculated from this Hamiltonian has a logarithmic singularity at an ideal separatrix. The logarithmic region inside the ideal separatrix contains 2.5% of toroidal flux inside the separatrix. The logarithmic region is symmetric about the separatrix. An area-preserving map for the field line trajectories is obtained in magnetic coordinates from the Hamiltonian equations of motion for the lines and a canonical transformation. This map is used to calculate trajectories of magnetic field lines in DIII-D. The field line Hamiltonian in DIII-D is used as the generating function for the map and to calculate stochastic broadening from field-errors and spatial noise near the separatrix. A very negligible amount (0.03%) of magnetic flux is lost from inside the separatrix due to these nonaxisymmetric fields. It is quite easy to add magnetic perturbations to generating functions and calculate trajectories for maps in magnetic coordinates. However, it is not possible to integrate across the separatrix. It is also difficult to find the physical position corresponding to magnetic coordinates. For open field lines, periodicity in the poloidal angle is assumed, which is not satisfactory. The goal of this paper is to demonstrate the efficacy of the symplectic mapping approach rather than using realistic DIII-D parameters or modeling specific experimental results. [ABSTRACT FROM AUTHOR]

Streaming instabilities in interstellar clouds have been investigated. It is pointed out that the motion of a lighter dust species relative to a plasma containing a heavier dust species can give rise to low frequency electrostatic fluctuations. The dust ion acoustic and dust acoustic waves can become unstable in such plasmas. The instability regions are influenced by the presence of background dust. Since interstellar clouds have relative motions in many cases and contain dust species, therefore the present results indicate the presence of an electrostatic dust ion acoustic wave and dust acoustic wave in such systems. The results have been applied to interstellar medium using particular data and comparisons have been made with previous works. [ABSTRACT FROM AUTHOR]

A simple map [A. Punjabi, A. Verma, and A. Boozer, Phys. Rev. Lett. 69, 3322 (1992)] is the simplest map that has the topology of divertor tokamaks [A. Punjabi, H. Ali, T. Evans, and A. Boozer, Phys. Lett. A 364, 140 (2007)]. Here, action-angle coordinates, the safety factor, and the equilibrium generating function for the simple map are calculated analytically. The simple map in action-angle coordinates is derived from canonical transformations. This map cannot be integrated across the separatrix surface because of the singularity in the safety factor there. The stochastic broadening of the ideal separatrix surface in action-angle representation is calculated by adding a perturbation to the simple map equilibrium generating function. This perturbation represents the spatial noise and field errors typical of the DIII-D [J. L. Luxon and L. E. Davis, Fusion Technol. 8, 441 (1985)] tokamak. The stationary Fourier modes of the perturbation have poloidal and toroidal mode numbers (m,n,)={(3,1),(4,1),(6,2),(7,2),(8,2),(9,3),(10,3),(11,3)} with amplitude δ=0.8×10-5. Near the X-point, about 0.12% of toroidal magnetic flux inside the separatrix, and about 0.06% of the poloidal flux inside the separatrix is lost. When the distance from the O-point to the X-point is 1 m, the width of stochastic layer near the X-point is about 1.4 cm. The average value of the action on the last good surface is 0.19072 compared to the action value of 3/5π on the separatrix. The average width of stochastic layer in action coordinate is 2.7×10-4, while the average area of the stochastic layer in action-angle phase space is 1.69017×10-3. On average, about 0.14% of action or toroidal flux inside the ideal separatrix is lost due to broadening. Roughly five times more toroidal flux is lost in the simple map than in DIII-D for the same perturbation [A. Punjabi, H. Ali, A. Boozer, and T. Evans, Bull. Amer. Phys. Soc. 52, 124 (2007)]. [ABSTRACT FROM AUTHOR]

The drift wave is investigated in a two-ion species plasma in several different cases. The global drift mode is studied in a plasma bounded in a cylinder having Gaussian density profile corresponding to different poloidal wavenumbers. The frequency of the mode becomes a little larger when it is investigated without including the ion cyclotron wave dynamics. The effect of magnetic shear on the wave propagation along the density gradient is studied in a Cartesian geometry assuming absorbing boundary. It is found that the wave amplitude is reduced when two-ion species are present (with the same concentration) compared to pure electron-ion plasma. [ABSTRACT FROM AUTHOR]

The low frequency electrostatic and electromagnetic linear modes in a nonuniform cold quantum electron-ion plasma are studied. The effect of stationary dust on an electrostatic mode is also investigated. The quantum corrections in the linear dispersion relations of a cold dense plasma are presented with possible applications. [ABSTRACT FROM AUTHOR]

The linear and nonlinear properties of the ion-acoustic waves (IAWs) are investigated by using the quantum hydrodynamic equations together with the Poisson equation in a three-component quantum electron-positron-ion plasma. For this purpose, a linear dispersion relation, a Korteweg-de Vries equation and an energy equation containing quantum corrections are derived. Computational investigations have been performed to examine the quantum mechanical effects on the linear and nonlinear waves. It is found that both the linear and nonlinear properties of the IAWs are significantly affected by the inclusion of the quantum corrections. The relevance of the present investigation to dense white dwarfs (where the electron-positron annihilation can be unimportant) is discussed. [ABSTRACT FROM AUTHOR]

The topological effects of magnetic perturbations on a divertor tokamak, such as DIII-D, are studied using field-line maps that were developed by Punjabi et al. [A. Punjabi, A. Verma, and A. Boozer, Phys. Rev. Lett. 69, 3322 (1992)]. The studies consider both long-wavelength perturbations, such as those of m=1, n=1 tearing modes, and localized perturbations, which are represented as a magnetic dipole. The parameters of the dipole map are set using DIII-D data from shot 115467 in which the C-coils were activated [J. L. Luxon and L. E. Davis, Fusion Technol. 8, 441 (1985)]. The long-wavelength perturbations alter the structure of the interception of magnetic field lines with the divertor plates, but the interception is in sharp lines. The dipole perturbations cause a spreading of the interception of the field lines with the divertor plates, which alleviates problems associated with heat deposition. Magnetic field lines are the trajectories of a one-and-a-half degree of freedom Hamiltonian, which strongly constrains the topological features of the lines. Although the field line maps that we use do not accurately represent the trajectories through ordinary space of individual field lines, they do represent their topological structure. [ABSTRACT FROM AUTHOR]

By employing the quantum hydrodynamic model and the reductive perturbation technique, a quantum Zakharov-Kuznetsov (QZK) equation is derived for finite but small amplitude ion-acoustic waves in a quantum magnetoplasma. The extended Conte’s truncation method is used to obtain the solitary, explosive, and periodic solutions of the QZK equation. Furthermore, the stability of the solitary wave solution of the QZK equation is investigated by using the small-k perturbation expansion method. [ABSTRACT FROM AUTHOR]

The quantum dust-acoustic double layers (QDADLs) are studied in an unmagnetized, collisionless quantum dusty plasma whose constituents are the electrons, ions, and negatively/positively charged dust particles. By employing the quantum hydrodynamical equations and the reductive perturbation technique, a quantum extended Korteweg–de Vries equation is derived. A steady-state double-layer solution of the latter is presented by taking into account the quantum-mechanical effects. It is numerically found that both compressive and rarefactive QDADLs can exist only for positive charged dust particles under the condition ni0/ne0<1, where ni0(ne0) is the unperturbed number density of the ions (electrons). It is further noted that the formation of the compressive and the rarefactive double layers depends on the quantum plasma parameters. The relevance of the present investigation to the dust charge impurities in laser-solid interactions is discussed. In general, this study should be useful for the diagnostics of charged dust impurities in ultrasmall microelectronic and nanoelectronic components, as well as in astrophysical objects where charged dust particles are inherently present. [ABSTRACT FROM AUTHOR]

Nonlinear interactions involving electrostatic upper-hybrid (UH), ion-cyclotron (IC), lower-hybrid (LH), and Alfvén waves in quantum magnetoplasmas are considered. For this purpose, the quantum hydrodynamical equations are used to derive the governing equations for nonlinearly coupled UH, IC, LH, and Alfvén waves. The equations are then Fourier analyzed to obtain nonlinear dispersion relations, which admit both decay and modulational instabilities of the UH waves at quantum scales. The growth rates of the instabilities are presented. They can be useful in applications of our work to diagnostics in laboratory and astrophysical settings. [ABSTRACT FROM AUTHOR]

By using the dielectric response function of quantum electron plasmas, potential distributions around a moving test charge are calculated. The near-field potential follows the modified Debye-Hückel potential, while the far-field potential turns out to be oscillatory. Both the Debye-Hückel and wake potentials strongly depend on the Fermi energy and the electron quantum correlation strength. The relevance of the present investigation to semiconductor plasmas is discussed. [ABSTRACT FROM AUTHOR]

The existence of new electromagnetic drift modes in nonuniform quantum magnetoplasmas is predicted. For this purpose, new dispersion relations are derived by employing the quantum magnetohydrodynamic equation for plasmas without and with ion motions. The effects of electron corrections due to quantum fluctuations, density gradients, and external magnetic field strengths on the angular wave frequencies and growth/damping rates are examined. The present analytical and numerical investigations are relevant to dense astrophysical objects. [ABSTRACT FROM AUTHOR]

A new dispersion relation for low-frequency compressional electromagnetic waves is derived by employing quantum magnetohydrodynamic model and Maxwell equations in cold quantum dusty magnetoplasmas. The latter is composed of inertialess electrons, mobile ions, and immobile charged dust particulates. The dispersion relation for the low-frequency compressional electromagnetic modes is further analyzed for the waves propagating parallel, perpendicular, and oblique to the external magnetic field direction. It is found theoretically and numerically that the quantum parameter αq=(ni0/ne0)h2/(4memi) affects the real angular frequencies and the phase speeds of the compressional electromagnetic modes. Here, ni0 (ne0) is the equilibrium number density of the ions (electrons), me (mi) is the electron (ion) mass, and h is the Plank constant divided by 2π. [ABSTRACT FROM AUTHOR]

By employing one-dimensional quantum hydrodynamic (QHD) model for a three species quantum plasma, nonlinear properties of dust acoustic solitary waves are studied. For this purpose a Korteweg-de Vries (KdV) equation is derived, incorporating quantum corrections. The quantum mechanical effects are also examined numerically both on the profiles of the amplitude and the width of dust acoustic solitary waves. It is found that the amplitude remains constant but the width shrinks for different values of a dimensionless electron quantum parameter He = √Zd0ℏ²ω²pd)/memdCd4, where Zd0 is the dust charge state, ℏ is the Planck constant divided by 2π, ωpd is the dust plasma frequency, me (md) is the electron (dust) mass, and Cd is the dust acoustic speed. [ABSTRACT FROM AUTHOR]

Expressions for the electrostatic potential and the energy loss are derived for a variety of arrays of dust grain projectiles, arranged at different orientations and separations and moving with a constant velocity along the z axis in an unmagnetized collisionless dusty plasma, using linear dielectric theory. By employing the dielectric constant of dust acoustic wave, the Debye and wake potentials are calculated for the projectiles. It is found that a projectile moving with high speed forms a negative wake behind and a shock in front of it. Further, for particular values of interspacing, the three different assemblies exhibit almost similar behavior of the energy loss and thus permit the possibility of all of them to move in unison to establish a dynamical equilibrium in a hexagonal geometry. [ABSTRACT FROM AUTHOR]

Generalized expressions for the Debye potential and the wake field potential are derived due to an axial propagation of dust grain projectiles. The dust grain projectiles are assumed to lie on sets of concentric circles propagating through the dusty plasma with a constant velocity along the z axis. Each circle carries N number of dust grain projectiles having radius rl and angular position (2πm)/N. A couple of specific cases of electrostatic potential due to four and eight projectiles are studied in some detail both analytically and numerically. [ABSTRACT FROM AUTHOR]

In our method of maps [Punjabi et al., Phy. Rev. Lett. 69, 3322 (1992), and Punjabi et al., J. Plasma Phys. 52, 91 (1994)], symplectic maps are used to calculate the trajectories of magnetic field lines in divertor tokamaks. Effects of the magnetic perturbations are calculated using the low MN map [Ali et al., Phys. Plasmas 11, 1908 (2004)] and the dipole map [Punjabi et al., Phys. Plasmas 10, 3992 (2003)]. The dipole map is used to calculate the effects of externally located current carrying coils on the trajectories of the field lines, the stochastic layer, the magnetic footprint, and the heat load distribution on the collector plates in divertor tokamaks [Punjabi et al., Phys. Plasmas 10, 3992 (2003)]. Symplectic maps are general, efficient, and preserve and respect the Hamiltonian nature of the dynamics. In this brief communication, a rigorous mathematical derivation of the dipole map is given. [ABSTRACT FROM AUTHOR]

The low MN map is derived from the general theory of maps and the generating function thr the low mn perturbation. The unperturbed magnetic topology of a single-null divertor tokamak is represented by the symmetric simple map. The perturbed topology is represented by the low MN map. The method of maps is applied to calculate the effects of low mn perturbation on the stochastic layer and the magnetic footprint. The low mn perturbation organizes the stochastic layer into large scale spatial structures. This is reflected in the phase portraits, safety factor, Liapunov exponents, magnetic footprints, and the semiconnection length. For the expected range of the amplitude of the low mn perturbation, the fraction of magnetic flux escaping the stochastic layer, the width of stochastic layer, the area of the magnetic footprints increase, while the number of hot spots and the fraction of flux going into the hot spots both decrease. The key features of the complex patterns in the heat deposition on the collector plates in divertor tokamaks are quite well recovered from the results of the low MN map. [ABSTRACT FROM AUTHOR]

The expressions for the Debye and the wake potential are derived by incorporating dust-charge fluctuations of a single projectile, as well as of an array of dust grain projectiles, propagating through a partially ionized dusty plasma with a constant velocity. Numerically, the effects of the dust-charge fluctuations and the dust–neutral collisions on the electrostatic potential for a single, three, six and ten projectiles are examined. The dust-charge relaxation rate modifies the shape of the Debye as well as the wake potential. For smaller values of the relaxation rates a potential well is formed instead of Debye potential. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

In this paper, the method of maps is used to calculate the effects of high toroidal and poloidal mode number perturbation on the trajectories of magnetic field lines in a single-null divertor tokamak. First, a simplified derivation of the dipole map from the Hamiltonian mechanics of magnetic field is given. This map represents the effects of an externally located current carrying coil on the motion of field lines. The unperturbed magnetic field topology of a single-null divertor tokamak is represented by the symmetric simple map. The coil is placed across from the X-point on the line joining the X-point and the O-point at a fixed distance from the last good confining surface. The effects of coil on the stochastic layer and magnetic footprint are calculated using the symmetric simple map and the dipole map. Self-similarities, singularities, and topological equivalences in the pattern of physical parameters are found that characterize the stochastic layer and the magnetic footprint. The dipole perturbation increases the area of footprint, drastically reduces the fraction of heat flux escaping the stochastic layer, disperses the heat flux more evenly over a wider area, and reduces number of hotspots on the collector plate. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The dielectric response function for modified dust acoustic waves is studied, incorporating the dipole moment and moment of inertia of finite sized elongated dust grains. Using this dielectric constant, generalized expressions for the Debye potential and for the wake potential are obtained due to a cluster of N² dust grain projectiles moving with a constant velocity along the z-axis through a multi-component dusty plasma. For illustration, numerical results due to single, three, and six projectiles are presented with and without a dipole effect. A negative wake potential is observed behind each projectile in different geometeries. [ABSTRACT FROM AUTHOR]

The shielded potential and the energy loss of N² projectiles propagating through a multicomponent dusty plasma are studied. Analytically general expressions have been obtained for the potential and for the energy loss, taking into account the two-body correlation effects. However, numerical calculations have been performed for one, three, and six projectiles, incorporating interference between two consecutive projectiles. It is found that the correlation effect causes distortion in the potential profile depending upon the separation between the two projectiles. The distortion becomes pronounced for separation smaller than the Debye length. [ABSTRACT FROM AUTHOR]