Laser-Induced Graphite Plasma Kinetic Spectroscopy under Different Ambient Pressures

The laser induced plasma dynamics of graphite material are investigated by optical emission spectroscopy. Abla- tion and excitation of the graphite material is performed by using an 1064nm Nd：YAG laser in different ambient pressures. Characteristics of graphite spectra as line intensity variations and signal-to-noise ratio are presented with a main focus on the influence of the ambient pressure on the interaction of laser-induced graphite plasma with an ambient environment. Atomic emission lines are utilized to investigate the dynamical behavior of plasma, such as the excitation temperature and electron density, to describe emission differences under different ambient conditions. The excitation temperature and plasma electron density are the primary factors which contribute to the differences among the atomic carbon emission at different ambient pressures. Reactions between the plasma species and ambient gas, and the total molecular number are the main factors influencing molecular carbon emis- sion. The influence of laser energy on the plasma interaction with environment is also investigated to demonstrate the dynamical behavior of carbon species so that it can be utilized to optimize plasma fluctuations.

The effect of forced oscillations on the kinetics of wave drift in an inhomogeneous plasma

The kinetics is analyzed of the drift of non-potential plasma waves in spatial positions and wavevectors due to plasma's spatial inhomogeneity. The analysis is based on highly informative kinetic scenarios of the drift of electromagnetic waves in a cold ionized plasma in the absence of a magnetic field(Erofeev 2015 Phys. Plasmas 22 092302) and the drift of long Langmuir waves in a cold magnetized plasma(Erofeev 2019 J. Plasma Phys. 85 905850104). It is shown that the traditional concept of the wave kinetic equation does not account for the effects of the forced plasma oscillations that are excited when the waves propagate in an inhomogeneous plasma.Terms are highlighted that account for these oscillations in the kinetic equations of the abovementioned highly informative wave drift scenarios.

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.

OH and O radicals production in atmospheric pressure air/Ar/H_2O gliding arc discharge plasma jet

Atmospheric pressure air/Ar/H_2O gliding arc discharge plasma is produced by a pulsed dc power supply. An optical emission spectroscopic（OES） diagnostic technique is used for the characterization of plasmas and for identifications of OH and O radicals along with other species in the plasmas. The OES diagnostic technique reveals the excitation Tx？≈？5550–9000 K, rotational Tr？≈？1350–2700 K and gas Tg？≈？850–1600 K temperatures, and electron density n？（1.1-1.9） ′101 4 cm^（-3） e under different experimental conditions. The production and destruction of OH and O radicals are investigated as functions of applied voltage and air flow rate. Relative intensities of OH and O radicals indicate that their production rates are increased with increasing Ar content in the gas mixture and applied voltage. nereveals that the higher densities of OH and O radicals are produced in the discharge due to more effective electron impact dissociation of H_2O and O_2 molecules caused by higher kinetic energies as gained by electrons from the enhanced electric field as well as by enhanced n e.The productions of OH and O are decreasing with increasing air flow rate due to removal of Joule heat from the discharge region but enhanced air flow rate significantly modifies discharge maintenance properties. Besides, Tgsignificantly reduces with the enhanced air flow rate. This investigation reveals that Ar plays a significant role in the production of OH and O radicals.

A Gyrokinetic simulation model for low frequency electromagnetic fluctuations in magnetized plasmas

We present a new model for simulating the electromagnetic fluctuations with frequencies much lower than the ion cyclotron frequency in plasmas confined in general magnetic configurations.This novel model(termed as GK-E&B)employs nonlinear gyrokinetic equations formulated in terms of electromagnetic fields along with momentum balance equations for solving fields.It,thus,not only includes kinetic effects,such as wave-particle interaction and microscopic(ion Larmor radius scale)physics;but also is computationally more efficient than the conventional formulation described in terms of potentials.As a benchmark,we perform linear as well as nonlinear simulations of the kinetic Alfvén wave;demonstrating physics in agreement with the analytical theories.

Electromagnetic High Frequency Gyrokinetic Particle-in-Cell Simulation

Using the gyrocenter-gauge kinetic theory,an electromagnetic version of the high frequency gyrokinetic numerical algorithm for particle-in-cell simulation has been developed.The new algorithm,being an alternative to a direct Lorentz-force simulation,offers an efficient way to simulate the dynamics of plasma heating and current drive with radio frequency waves.Gyrokinetic formalism enables separation of gyrocenter and gyrophase motions of a particle in a strong magnetic field.From this point of view,a particlemay be viewed as a combination of a slow gyrocenter and a quickly changing Kruskal ring.In this approach,the nonlinear dynamics of high frequency waves is described by the evolution of Kruskal rings based on first principles physics.The efficiency of the algorithm is due to the fact that the simulation particles are advanced along the slow gyrocenter orbits,while the Kruskal rings capture fast gyrophase physics.Moreover,the gyrokinetic formalism allows separation of the cold response from kinetic effects in the current,which allows one to use much smaller number of particles than what is required by a direct Lorentz-force simulation.Also,the new algorithm offers the possibility to have particle refinement together with mesh refinement,when necessary.To illustrate the new algorithm,a simulation of the electromagnetic low-hybrid wave propagating in inhomogeneous magnetic field is presented.