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A plasma discharge due to a sustaining pulse of an alternating current plasma display panel was analyzed using a two-dimensional particle-in-cell code, and basic characteristics of the plasma discharge were calculated. The characteristics of the plasma discharge due to a sustaining pulse are as follows. (i) A large amount of space charge remained after drawing the discharge current. This excess space charge did not contribute to wall charge formation or ultraviolet radiation. (ii) The electron energy distribution function was evaluated and could be well fitted by the Druyvesteyn distribution in the high-energy region. The Druyvesteyn distribution was a consequence of the cross section for electron-Ne elastic scattering. (iii) The calculated ultraviolet radiation efficiency η of the plasma discharge due to a sustaining pulse was between 5.51% and 30.7%. Examination of the sensitivity of the efficiency to the electron temperature showed that reducing the electron temperature was a key to improving the efficiency. (iv) A detailed understanding of the conditions for a stable plasma discharge, memory margin, firing voltage, and electrode voltage of the sustaining pulse were obtained from the voltage transfer curve. The voltage transfer curve could be used to optimize the discharge cell design. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Discusses a study which used spherical and cylindrical many-particle models to stimulate radio frequency discharges. Computational formula for Poisson's equation; Theoretical models for radio frequency discharges; Difference between plasma potential and driven electrode potential.

Focuses on a general one-dimensional model to study the plasma-immersion ion implantation process in different coordinate systems. Analytic expressions for normal ion velocity distribution and other parameters; Effect of a charge-exchange collision on an ion; Equation concerning the average ion velocity at the target.

The use of waves applied by a periodic electrode to controllably modify the particle velocity distribution in a plasma is explored. The applied waves induce a strong wave–particle interaction analogous to Landau damping. However, as the waves are powered by an external circuit, the interaction continues until a new plasma equilibrium is established. At saturation, the velocity distribution is enhanced above the phase velocity of the applied wave and suppressed below. The use of this technique to selectively heat the electron high-energy tail and to enhance the electron-impact ionization rate is demonstrated using particle-in-cell simulation. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Presents a description of an electron transport across the magnetic field on the basis of surface waves perpendicular to the magnetic field. Explanation on the theory of slow transport across the diode; Comparison of growth and wavelength of surface waves to PIC simulations; Results of the slow expansion of the Brillouin hub.

Weakly ionized processing plasmas are studied in two dimensions using a bounded particle-in-cell (PIC) simulation code with a Monte Carlo collision (MCC) package. The MCC package models the collisions between charged and neutral particles, which are needed to obtain a self-sustained plasma and the proper electron and ion energy loss mechanisms. A two-dimensional capacitive radio-frequency (rf) discharge is investigated in detail. Simple frequency scaling laws for predicting the behavior of some plasma parameters are derived and then compared with simulation results, finding good agreements. It is found that as the drive frequency increases, the sheath width decreases, and the bulk plasma becomes more uniform, leading to a reduction of the ion angular spread at the target and an improvement of ion dose uniformity at the driven electrode. [ABSTRACT FROM AUTHOR]

A fully kinetic particle-in-cell (PIC) model is used to self-consistently determine the steady-state potential profile in a collisionless plasma that contacts a floating, absorbing boundary. To balance the flow of particles to the wall, a distributed source region is used to inject particles into the one-dimensional system. The effect of the particle source distribution function on the source region and collector sheath potential drops, and particle velocity distributions is investigated. The ion source functions proposed by Emmert et al. [Phys. Fluids 23, 803 (1980)] and Bissell and Johnson [Phys. Fluids 30, 779 (1987)] (and various combinations of these) are used for the injection of both ions and electrons. The values of the potential drops obtained from the PIC simulations are compared to those from the theories of Emmert et al., Bissell and Johnson, and Scheuer and Emmert [Phys. Fluids 31, 3645 (1988)], all of which assume that the electron density is related to the plasma potential via the Boltzmann relation. The values of the source region and total potential drop are found to depend on the choice of the electron source function, as well as the ion source function. The question of an infinite electric field at the plasma–sheath interface, which arises in the analyses of Bissell and Johnson and Scheuer and Emmert, is also addressed. [ABSTRACT FROM AUTHOR]

The region between a Maxwellian plasma source and an absorbing surface is described theoretically with a static, kinetic plasma–sheath model and modeled numerically with a dynamic, electrostatic particle simulation. In the kinetic theory, Poisson’s equation and Vlasov equations govern the non-Maxwellian velocity distribution of the ions and electrons. The results in this paper for collector potential and plasma transport agree with the bounded model of Emmert et al. [Phys. Fluids 23, 803 (1980)]. However, this approach differs from those using traditional Bohm sheath analysis by ±0.25 (in units of electron temperature) for potential drop through the collector sheath of a hydrogen plasma. In both the theory and simulation, the plasma source injects equal fluxes of ions and electrons with half-Maxwellian velocities and various mass and temperature ratios and is assumed to have a zero electric field. The potential change within a spatially distributed, full Maxwellian source region is represented with the source sheath potential drop that depends primarily on temperature ratio. This source sheath evolves over a few Debye lengths from the source to neutralize the injected plasma. The plasma flows to an electrically floating collector where the more familiar electron-repelling collector sheath appears. The collector potential ψC and source sheath potential drop ψP (in units of electron temperature) are evaluated as a function of mass and temperature ratio. The velocity moments of density, drift velocity, temperature, kinetic energy flux, and heat flux are also derived as a function of ψC and ψP. Comparisons with electrostatic particle simulations are shown for the ion/electron mass ratios of 40 and 100 and temperature ratios of 0.1, 1, and 10. For a deuterium–tritium plasma (single-ion species with a mass of 2.5 amu) with equal ion and electron temperatures, then, ψC=-3.3 and ψP=-0.3. At the collector, the ions... [ABSTRACT FROM AUTHOR]

The steady-state behavior of the magnetized plasma-wall sheath has been studied through twodimensional particle simulations, which have shown that the sheath maintains itself in a strongly nonlinear, turbulent equilibrium, continuously driven by the edge Kelvin-Helmholtz instability. The sheath assumes a thickness of order l[sub x] ∼5ρ[sub i], and maintains large, long-lived vortices, with amplitudes δφ ∼ 2.5 T[sub i]/e, which drift parallel to the wall at half the ion thermal velocity. The sheath also maintains a large, spatially averaged potential drop from the wall to the plasma with Δφ≈ - 2T[sub i]/e, opposite in sign to that of the unmagnetized sheath. Accompanying the long-wavelength vortices are shorter-wavelength fluctuations, which induce an anomalous cross-field transport, scaling in accordance to Bohm diffusion when ω[sub pi] ≥ 2ω[sub ci]. At lower densities, ω[sub pi] < 2ω[sub ci], the diffusion coefficient has an additional factor, proportional to the density. These results permit the modeling of the cross-field sheath by a simple effective boundary condition. [ABSTRACT FROM AUTHOR]

The time-dependent behavior of a transversely magnetized, two-dimensional plasma-wall sheath has been studied through particle simulations, with the aim of modeling plasma behavior in the vicinity of the limiters and walls of magnetized plasma devices. The model assumes a magnetic field perfectly parallel to the confining surfaces. The simulations have shown that the cross-field sheath between a wall and a plasma is a self-sustaining turbulent boundary layer, with strong potential fluctuations and anomalous particle transport. The driving mechanism for this turbulence is the Kelvin-Helmholtz instability, which arises from the sheared particle drifts created near the wall. In this paper, the transient behavior leading to the turbulent steady state is presented, and the processes of linear growth, vortex saturation, and vortex coalescence are examined. An analytic model for the boundary Kelvin-Helmholtz instability is derived and shown to correctly predict the growth rates of the long-wavelength modes. In a companion paper, the steady-state structure and behavior of the cross-field sheath will be discussed in detail. [ABSTRACT FROM AUTHOR]

Time-average values from particle simulations of a collisionless, single-emitter plasma device modeling single-ended Q machines or thermionic converters with a negatively biased collector are presented. These results quantitatively confirm the predictions of collisionless, kinetic plane-diode theory for spatial potential profiles that decrease monotonically. However, simulations of negative-bias potential profiles with a single internal maximum differ significantly from previous theoretical predictions which assumed electron phase space to have either (i) no trapped electrons or (ii) trapped electrons isothermal with the passing electrons. A more general class of trapped-electron model distributions is introduced from which new equilibrium potential values can be recovered that closely match the simulations. These simulations clearly demonstrate the sensitive role that trapped electrons play in shaping the potential profiles of the equilibrium (or slowly evolving) states of the simulated systems. The trapped-electron distributions in these simulations are themselves shown to be controlled critically by fluctuations whose levels are varied by the choice of particle injection scheme. These effects, although found and discussed here in the context of a particular model, are believed to be important in many bounded plasma systems where electrons can be trapped in potential wells. [ABSTRACT FROM AUTHOR]

In the alternating current plasma display panel, a widespread discharge can take place accidentally in a large number of cells in the upper or lower panel ends. The undesirable discharge is referred to as global breakdown. This is a serious problem, with consequences not only for display quality, but also for product reliability. The mechanism of the global breakdown was examined experimentally using a surface electrometer and theoretically using plasma simulation. From these examinations, the global breakdown mechanism was clarified as follows. Global breakdown was accompanied by charge separation in the horizontal direction of the panel. This charge separation was caused by electron transport downward in the panel during the address discharge. The electron transport formed a negative wall charge on the phosphor surface. When the wall voltage exceeded the insulation voltage of the protective layer, global breakdown occurred. Furthermore, it was clarified that increasing the front dielectric thickness or reducing the back dielectric thickness could suppress the electron transport during the address discharge. These optimizations of cell geometry could eliminate the global breakdown. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Kinetic simulation of plasmas in which equilibrium occurs over ion time scales poses a computational challenge due to disparity with electron time scales. Hybrid electrostatic particle-in-cell (PIC) algorithms are presented in which most of the electrons reach thermodynamic equilibrium [Maxwell-Boltzmann (MB) distribution function] each time step. Conservation of charge enables convergence of the nonlinear Poisson equation. Energy conservation is used to determine the temperature of the Boltzmann species. This article first develops an algorithm where all the electrons have a MB energy distribution, either with a full MB distribution or with a truncation of the high energy tail. Second, high energy PIC electrons are added to the truncated distribution so that high energy electrons are modeled kinetically by PIC and low energy electrons (the majority) are modeled by the MB distribution. Collisions for PIC electrons are included via a Monte Carlo model, while for the MB electrons, the distributions are integrated with energy dependent cross sections. The MB model is not constrained by the electron time scale which decreases the required computer time by about the square root of the mass ratio of ion to electron. However, the hybrid boundary conditions are more complex and the simulation is not quite self-consistent. Comparison between full PIC and the PIC-MB hybrid is made for simulations of photo-ionized sustained discharges and current-driven dc discharges. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

For electronegative plasmas with low gas pressure and high ion densities, we expect Coulomb collisions between positive and negative ions to dominate over collisions between ions and neutrals. We incorporated Nanbu's cumulative small-angle collision method [K. Nanbu, Phys. Rev. E, 55, 4642 (1997)] into our one-dimensional three-velocity-component particle-in-cell code PDP1 in order to study the effect of Coulomb collisions on low pressure high density electronegative discharges. Nanbu's method treats a succession of small-angle binary collisions as a single binary collision with a large scattering angle, which is far faster than treating each individual small-angle collision. We find that Coulomb collisions between positive and negative ions in low-pressure high-density electronegative discharges significantly modify the negative ion flux, density, and kinetic energy profiles.