Spatial evolution of the electron-energy distribution in the vicinity of a discharge-tube constriction (original) (raw)

Investigation of a -discharge plasma under an increased pressure of Ar and in narrow tubes

Journal of Physics D: Applied Physics, 1998

The electrokinetic characteristics (the electron energy distribution function, the strength of the longitudinal electric field and the concentration and average energy of electrons) are measured and calculated in a (Hg + Ar)-discharge plasma under a high pressure of argon (up to 30 Torr) and in narrow tubes (the tube radius is less than 1.0 cm). A simple method of treating the second derivative of the probe current with respect to the probe potential is proposed for a straightforward way to obtain the electron energy distribution function under a high pressure of a gas. It is shown that the main assumptions on which modelling of the plasma of mercury luminescent lamps is based are also valid for the plasma in question. This leads to the existence of special similarity laws and gives a new possibility for diagnostics based on the similarity properties of the plasma. The approach proposed in the work can be easily extended to the mixtures of mercury vapour and other rare gases.

Two-dimensional fluid simulation of electronegative discharge plasmas

IEEE Conference Record - Abstracts. 1996 IEEE International Conference on Plasma Science

For radio-frequency discharges of electronegative gases, one-dimensional equilibrium equations for plasma variables are formulated and the scaling formulae of the plasma variables are derived in terms of the control parameters. The control parameters consist of three parameters: p (pressure), lp (halfsystem length), and P (power) or ne (electron density). The classifications of the operating regions are performed according to the prevailing particle-loss mechanism (recombination-loss-dominated or ion-flux-loss-dominated) and according to the main heating mechanism (ohmic-heating-dominated or stochastic-heating-dominated). The variations of the charged particle densities with pressure and absorbed power are estimated and compared with the results of a particle-in-cell simulation.

Electron Acceleration and Excitation Processes in the Vicinity of a Mercury Discharge Constriction

In the present paper axial distributions of plasma and floating potentials, electron and ion densities and EEDF have been measured in the DL region of a Hg discharge constriction. An attempt has been made for the resolution of opposing charged layer structures in DL. Excitation processes in the constriction region are studied. Using the linearization method for the nonstationary balance equations system and choosing appropriate discharge conditions, the step excitation rate by the electron impact for 6 3 P 2 →7 1 S 0 transition in Hg is determined.

Modeling of discharges generated by electron beams in dense gases: Fountain and thunderstorm regimes

Physics of Plasmas, 2001

In this paper we present an analysis of the predicted dynamics of plasmas generated in air and other gases by injecting beams of high-energy electrons. Two distinct regimes are found, differing in the way that the excess negative charge brought in by the ionizing electron beam is removed. In the first regime, called a fountain, the charge is removed by the back current of plasma electrons toward the injection foil. In the second, called a thunderstorm, a substantial cloud of negative charge accumulates, and the increased electric field near the cloud causes a streamer to strike between the cloud and a positive or grounded electrode, or between two clouds created by two different beams. A quantitative analysis, including electron beam propagation, electrodynamics, charge particle kinetics, and a simplified heat balance, is performed in a one-dimensional approximation.

Non-Equilibrium EEDF in Gas Discharge Plasmas”, submitted to special issue of “Nonlocal electron kinetics in low pressure plasmas

2005

Abstract—Nonequilibrium effects associated with spatial and temporal nonlocality between electron energy distribution and electromagnetic field in gas discharge plasmas at low gas pressures are reviewed in this paper. Formation of nonequilibrium EEDF is discussed for capacitive and inductive radio-frequency discharges. The possibility of electron temperature control is considered for gas discharge plasmas at nonequilibrium condition. Index Terms—Electron energy distribution function (EEDF), electron kinetics, gas discharge, nonequilibrium. I.

Ionization front in a high-current gas discharge

Physics of Plasmas, 2007

Spectroscopic measurements of ion/neutral density ratio profiles are made inside the high-current, low-pressure discharge of a coaxial magnetoplasmadynamic thruster and show the existence of a thin ionization front, upstream in the discharge, that effectively ionizes the incoming gas to ionization levels above 50%. The measurements allow an estimate of the width of this ionization front to be on the order of a few millimeters. Due to the known existence of microturbulence in the plasma, which can produce suprathermal electrons, an explanation of the measurements based on the existence of a suprathermal tail in the electron energy distribution function is sought. A theoretical model for the width of the ionization front is combined with a multilevel excitation model for argon and shows that a Maxwellian electron distribution function cannot account for the small length scale of the ionization front, and that the latter is more consistent with an electron distribution function having a suprathermal population, the magnitude of which is estimated by comparing the model to the experiments.

Simulation of electron kinetics in gas discharges

IEEE Transactions on Plasma Science, 2006

We review the state-of-the-art for the simulation of electron kinetics in gas discharges based on the numerical solution of the Boltzmann equation. The reduction of the six-dimensional Boltzmann equation to a four-dimensional Fokker-Planck equation using two-term spherical harmonics expansion enables efficient and accurate simulation of the electron distribution function in collisional gas discharge plasmas. We illustrate this approach in application to inductively coupled plasmas, capacitively coupled plasmas, and direct current glow discharges. The incorporation of the magnetic field effect into this model is outlined. We also describe recent efforts towards simulating collisionless effect in gas discharge plasma based on Vlasov solvers and outline our views on future development of the numerical models for gas discharge simulations

Numerical simulations of runaway electron generation in pressurized gases

Journal of Applied Physics, 2012

Density evolution measurement of hydrogen plasma in capillary discharge by spectroscopy and interferometry methods Appl. Phys. Lett. 99, 141502 (2011) Numerical analysis of plasma evolution on dielectric barrier discharge plasma actuator J. Appl. Phys. 110, 013302 (2011) Neutral gas dynamics in fireballs J. Appl. Phys. 109, 113305 (2011) Space-and time-resolved characterization of nanosecond time scale discharge at pressurized gas J. Appl. Phys. 109, 073312 A plasma needle for generating homogeneous discharge in atmospheric pressure air Phys. Plasmas 17, 093504 Additional information on J. Appl. Phys.

Spatially averaged model of complex-plasma discharge with self-consistent electron energy distribution

Physical Review E, 2004

A global, or averaged, model for complex low-pressure argon discharge plasmas containing dust grains is presented. The model consists of particle and power balance equations taking into account power loss on the dust grains and the discharge wall. The electron energy distribution is determined by a Boltzmann equation. The effects of the dust and the external conditions, such as the input power and neutral gas pressure, on the electron energy distribution, the electron temperature, the electron and ion number densities, and the dust charge are investigated. It is found that the dust subsystem can strongly affect the stationary state of the discharge by dynamically modifying the electron energy distribution, the electron temperature, the creation and loss of the plasma particles, as well as the power deposition. In particular, the power loss to the dust grains can take up a significant portion of the input power, often even exceeding the loss to the wall.