New Soliton Wave Solutions to a Nonlinear Equation Arising in Plasma Physics

The extraction of traveling wave solutions for nonlinear evolution equations is a challenge in various mathematics,physics,and engineering disciplines.This article intends to analyze several traveling wave solutions for themodified regularized long-wave(MRLW)equation using several approaches,namely,the generalized algebraic method,the Jacobian elliptic functions technique,and the improved Q-expansion strategy.We successfully obtain analytical solutions consisting of rational,trigonometric,and hyperbolic structures.The adaptive moving mesh technique is applied to approximate the numerical solution of the proposed equation.The adaptive moving mesh method evenly distributes the points on the high error areas.This method perfectly and strongly reduces the error.We compare the constructed exact and numerical results to ensure the reliability and validity of the methods used.To better understand the considered equation’s physical meaning,we present some 2D and 3D figures.The exact and numerical approaches are efficient,powerful,and versatile for establishing novel bright,dark,bell-kink-type,and periodic traveling wave solutions for nonlinear PDEs.

Transformation Plasma Physics

Plasma technology has widespread applications in many fields, whereas the methods for manipulating plasma transport are limited to magnetic control. In this study, we used a simplified diffusion-migration approach to describe plasma transport. The feasibility of the transformation theory for plasma transport was demonstrated.As potential applications, we designed three model devices capable of cloaking, concentrating, and rotating plasmas without disturbing the density profile of plasmas in the background. This research may help advance plasma technology in practical fields, such as medicine and chemistry.

Brief Introduction to the Foundation of CAI Shidong Award for Plasma Physics

The late Academician Professor CAI Shidong was an outstanding plasma physicist who had made seminal contributions in both fundamental plasma theories and controlled thermonuclear fusion energy research. Professor CAI was also one of the pioneers in China＇s plasma physics research. In 1973, Professor CAI decided to leave U.S.

Solitons and periodic waves for a generalized(3+1)-dimensional Kadomtsev-Petviashvili equation in fluid dynamics and plasma physics

Under investigation in this paper is a generalized(3+1)-dimensional Kadomtsev-Petviashvili equation in fluid dynamics and plasma physics.Soliton and one-periodic-wave solutions are obtained via the Hirota bilinear method and Hirota-Riemann method.Magnitude and velocity of the one soliton are derived.Graphs are presented to discuss the solitons and one-periodic waves:the coefficients in the equation can determine the velocity components of the one soliton,but cannot alter the soliton magnitude;the interaction between the two solitons is elastic;the coefficients in the equation can influence the periods and velocities of the periodic waves.Relation between the one-soliton solution and one-periodic wave solution is investigated.

Tunable energy spectrum betatron x-ray sources in a plasma wakefield

X-ray sources with tunable energy spectra have a wide range of applications in different scenarios due to their different penetration depths.However,existing x-ray sources face difficulties in terms of energy regulation.In this paper,we present a scheme for tuning the energy spectrum of a betatron x-ray generated from a relativistic electron bunch oscillating in a plasma wakefield.The center energy of the x-ray source can be tuned from several keV to several hundred keV by changing the plasma density,thereby extending the control range by an order of magnitude.At different central energies,the brightness of the betatron radiation is in the range of 3.7×10^(22)to 5.5×10^(22)photons/(0.1%BW·s·mm^(2)·mrad^(2))and the photon divergence angle is about 2 mrad.This high-brightness,energy-controlled betatron source could pave the way to a wide range of applications requiring photons of specific energy,such as phase-contrast imaging in medicine,non-destructive testing and material analysis in industry,and imaging in nuclear physics.

Fast weighting method for plasma PIC simulation on GPU-accelerated heterogeneous systems

Particle-in-cell (PIC) method has got much benefits from GPU-accelerated heterogeneous systems.However,the performance of PIC is constrained by the interpolation operations in the weighting process on GPU (graphic processing unit).Aiming at this problem,a fast weighting method for PIC simulation on GPU-accelerated systems was proposed to avoid the atomic memory operations during the weighting process.The method was implemented by taking advantage of GPU's thread synchronization mechanism and dividing the problem space properly.Moreover,software managed shared memory on the GPU was employed to buffer the intermediate data.The experimental results show that the method achieves speedups up to 3.5 times compared to previous works,and runs 20.08 times faster on one NVIDIA Tesla M2090 GPU compared to a single core of Intel Xeon X5670 CPU.

Accurate Solutions of the Plasma Motion Equation May be Composed with the Accurate Solutions of the Burgers Equation

The travelling solutions of the Burgers equation may be used as the seed solutions. According to the fraction-type deforming relation between the Burgers equation and the plasma motion equation, some travelling solutions of the plasma motion equation are achieved with this seed solutions as discussed in this paper.

Surface Wave Analysis of Planar-Type Overdense Plasma with Surface Plasmon Polariton Resonance

Surface waves （SWs） in planar-type overdense plasmas are analyzed and the invariable SW mode caused by the resonant excitation of surface plasmon polaritons （SPPs） is presented. It is found that the electric field peaks at the location where the plasma density equals the cut-off density while the plasma density gradient and the collision rate have different influences on the field amplitude and the peak＇s width. Moreover, the mode conversion between SW of SPPs and electron plasma waves play a significant role in production of overdense plasma.

Quantum Effects on Rayleigh-Taylor Instability of Incompressible Plasma in a Vertical Magnetic Field

Quantum effects on Rayleigh-Taylor instability of a stratified incompressible plasmas layer under the influence of vertical magnetic field are investigated. The solutions of the linearized equations of motion together with the boundary conditions lead to deriving the relation between square normalized growth rate and square normalized wave number in two algebraic equations and are numerically analyzed. In the case of the real solution of these two equations, they can be combined to generate a single equation. The results show that the presence of vertical magnetic field beside the quantum effect will bring about more stability on the growth rate of unstable configuration.

Measurement of Plasma Density Produced in Dielectric Barrier Discharge for Active Aerodynamic Control with Interferometer

We utilize an interferometer to investigate the changes of the refractive index caused by dielectric barrier discharge plasma. The electronic density of the plasma produced is measured and analyzed tentatively. The results show that density of the plasma increases linearly with exciting voltages.

Coulomb Explosion and Energy Loss of Energetic C20 Clusters in Dense Plasmas

The molecular dynamics （MD） method is used to simulate the interactions of energetic C20 clusters with the dense plasma targets within the framework of the linear Vlasov-Poisson theory. The influences of various clusters （H2, N2, C20 and C60 respectively） on stopping power are discussed. The simulation results show that the vicinage effects in the Coulomb explosion dynamics and the stopping power are strongly affected by the variations in the cluster speed and the plasma parameters. Coulomb explosions are found to proceed faster for higher speeds, lower plasma densities and higher electron temperatures. In addition, the cluster stopping power is strongly enhanced in the early stages of Coulomb explosions due to the vicinage effect, but this enhancement eventually diminishes, after the cluster constituent ions are sufficiently separated. For the large and heavy clusters, the stopping power ratio reaches much higher values in the early stage of Coulomb explosion owing to the constructive interferences in the vicinage effect.

PDRK:A General Kinetic Dispersion Relation Solver for Magnetized Plasma

A general,fast,and effective approach is developed for numerical calculation of kinetic plasma linear dispersion relations.The plasma dispersion function is approximated by J-pole expansion.Subsequently,the dispersion relation is transformed to a standard matrix eigenvalue problem of an equivalent linear system.Numerical solutions for the least damped or fastest growing modes using an 8-pole expansion are generally accurate;more strongly damped modes are less accurate,but are less likely to be of physical interest.In contrast to conventional approaches,such as Newton＇s iterative method,this approach can give either all the solutions in the system or a few solutions around the initial guess.It is also free from convergence problems.The approach is demonstrated for electrostatic dispersion equations with one-dimensional and twodimensional wavevectors,and for electromagnetic kinetic magnetized plasma dispersion relation for bi-Maxwellian distribution with relative parallel velocity flows between species.

Research on 2D Model of Capillary Discharge Plasma

The physical process of capillary discharge in a PE tube utilized in electro-thermal-chemical(ETC)guns was investigated.ETC guns can enhance the ignition and combustion of propellant in order to reduce the ignition delay and increase muzzle velocity of the projectile.A key component in ETC gun is the capillary plasma source.In this paper,a 2D steady state model of discharge was built by using magnetic hydrodynamics method.It took the plasma energy balance,material ablation,mass and momentum conservations in a quasi-neutral plasma region into account.Also,the effect of different compositions and PE concentration distribution were considered.In order to evaluate the validation of this model,the simulation results are compared with former works.

Experimental Study on Plasma Temperature of Semiconductor Bridge

The plasma temperature of the semiconductor bridge (SCB) was measured in real-time according to relative intensity ratio of dual lines of atomic emission spectrum.The plasma temperature under different discharge pulses and the influence of discharge pulse energy on it were studied.The results show that the plasma peak temperature rises gradually with the increase of initial discharging voltage and charging capacitance.For the capacitance of 22 μF,if the initial discharging voltage increases from 21 V to 63 V,the plasma peak temperature rises from 2 000 K to 6 200 K.For the discharging voltage of 39 V,the peak temperature rises from 2 200 K to 3 800 K when the capacitance increases from 6.8 μF to 100 μF.The change of pulse discharge has a very small effect on the plasma temperature at the late time discharge (LTD).In view of the change of plasma temperature with the pulse energy,the discharging voltage has a greater effect on the plasma temperature than the capacitance.The results provide some experimental basis for the further research on SCB ignition and detonation mechanisms.

Growth and Characteristics of Freestanding Hemispherical Diamond Films by Microwave Plasma Chemical Vapor Deposition

Freestanding hemispherical diamond films have been fabricated by microwave plasma chemical vapor deposition using graphite and molybdenum （Mo） as substrates. Characterized by Raman spectroscopy and scanning electron microscopy, the crystalline quality of the films deposited on Mo is higher than that on graphite, which is attributed to the difference in intrinsic properties of the two substrates. By decreasing the methane concentration, the diamond films grown on the Mo substrate vary from black to white, and the optical transparency is enhanced. After polishing the growth side, the diamond films show an infrared transmittance of 35-60% in the range 400-4000 cm^- 1.

CuInSe2 Films Prepared by a Plasma-Assisted Selenization Process in Different Working Pressures

The effects of working pressure on the composition, structure and surface morphology properties of CuInSe2 （CIS） films selenized with a plasma-assisted selenization process is investigated. Higher selenium content, better crystalline quality and much more regular surface particles compared to the others are found in the CIS film with 40 Pa working pressure. A Cu（In,Ga）Se2 device fabricated with the optimized plasma-assisted selenization process is demonstrated to be better than our previous result. After discussion, the reason for these phenomena is attributed to the compromise of electron temperature and plasma density.

Cavity-Defect Plasma Bragg Gratings

Plasma Bragg grating （PBG） is composed of periodic variations of plasma and dielectric or vacuum. The defect mode characteristic of the PBG with a cavity-defect is studied by one-dimensional particle-in-cell （1D PIC） simulation. It is shown that the laser pulse with the defect frequency can be localized around the defect partly and at the same time leak out of both sides of the grating slowly because of the few number of the grating period. This results in local high laser field intensity and high plasma density produced at the defect area, from which the third harmonic is enhanced by one order of magnitude. With the enhancement of the light coupled to the defect and the decrease of the light leaking out of the defect, the conversion efficiency of the third harmonic from the incident laser can be increased.

Effect of Air Gap on Uniformity of Large-Scale Surface-Wave Plasma

The effect of air gap on the uniformity of large-scale surface-wave plasma （SWP） in a rectangular chamber device is studied by using three-dimensional numerical analyses based on the finite difference time-domain （FDTD） approximation to Maxwel1＇s equations and plasma fluid model. The spatial distributions of surface wave excited by slot-antenna array and the plasma parameters such as electron density and temperature are presented. For different air gap thicknesses, the results show that the existence of air gap would severely weaken the excitations of the surface wave and thereby the SWP. Thus the air gap should be eliminated completely in the design of the SWP source, which is opposite to the former research results.

Structures and Dynamics of Two-Dimensional Dust Lattices with and without Coulomb Molecules in Plasmas

Structures and dynamics of two-dimensional dust lattices with and without Coulomb molecules in plasmas are investigated. The experimental results show that the lattices have the crystal-like hexagonal structures, i.e. most particles have six nearest-neighboring particles. However, the lattice points can be occupied by the individual particles or by a pair of particles called Coulomb molecules. The pair correlation function is used to compare the structures between the lattices with or without the Coulomb molecules. In the experiments, the Coulomb molecules can also decompose and recombine with another individual particle to form a new molecule.

Lattice Waves in Two-Dimensional Hexagonal Quantum Plasma Crystals

Lattice waves including a longitudinal wave and a transverse wave in two-dimensional hexagonal quantum plasma crystals are investigated by using the modified Debye-Hückel screening potential. It is shown that there exists an unstable region of lattice parameters, where the system will melt. The general dispersion relations are derived, and the waves propagating parallel to a primitive translation vector are discussed. We find that both the longitudinal and transverse waves are acoustic-like, and the longitudinal wave has a greater sound speed than that of the transverse wave in the long wavelength limit region.