Continuum Modeling of Charged Particle Transport: RF Breakdown and Discharges of SF6

1986 ◽  
Vol 68 ◽  
Author(s):  
Brian E. Thompson ◽  
Herbert H. Sawun ◽  
Aaron Owens
Keyword(s):  
Electric Fields ◽  
Electron Attachment ◽  
Negative Ions ◽  
Rate Coefficients ◽  
Rf Discharge ◽  
Continuity Equations ◽  
Positive Ions ◽  
Discharge Model ◽  
Rf Breakdown ◽  
Charged Particle Transport

AbstractContinuity equations for the concentration of electrons, positive ions, and negative ions were constructed and solved to predict rf breakdown voltages and the electrical properties of SF, discharges.These balances for the three types of charged species include terms for convection (electric field-driven fluxes), diffusion, and reactions (ionization, electron attachment, and negative-positive ion recombination).The mobilities, diffusivities, and reaction rate coefficients necessary for the rf discharge model are based on reported measurements and calculations of these parameters in dc electric fields.The electric fields developed in the rf discharge are calculated from Poisson's equation and applied voltage conditions.Predictions based on this model are compared with measured rf breakdown characteristics of SF6.

Theory of positive columns in electronegative gases

1980 ◽  
Vol 370 (1742) ◽  
pp. 375-387 ◽  
Keyword(s):  
Electron Attachment ◽  
Negative Ions ◽  
State Theory ◽  
Discharge Column ◽  
Electron Collisions ◽  
Charged Species ◽  
Continuity Equations ◽  
Positive Ions ◽  
Axial Concentration ◽  
Very High

A steady state theory of the positive column of a glow discharge in an electronegative gas is presented. Excitation and ionization are assumed to occur by single-electron collisions with neutral molecules. Both electron attachment and detachment are included in the continuity equations, the latter being due to long-lived excited neutral molecules taken to be uniformly distributed in the gas. Fluid-type momentum equations are used to describe the motion of positive and negative ions and of the electrons. By retaining Poisson’s equation throughout the treatment it is possible to impose physically realistic boundary conditions on all three charged species. It is found that the radial distribution of negative ions in the column is substantially different from that of the positive ions and the electrons. This is caused by the inwardly directed drift velocity of the negative ions, which confines them almost completely to the central region of the discharge column. Since the axial concentration of the negative ions relative to that of the electrons depends on the ratio of the coefficients of attachment to detachment, the concentration can reach very high values indeed when the rate of detachment is low.

Numerical Simulation of Leakage Current on Conductive Insulator Surface

2019 ◽  
Vol 8 (4) ◽  
pp. 9487-9492
Keyword(s):  
Numerical Simulation ◽  
Electric Field ◽  
Leakage Current ◽  
Method Of Lines ◽  
Electron Attachment ◽  
Negative Ions ◽  
Conduction Current ◽  
Insulator Surface ◽  
Finite Difference Approximations ◽  
Positive Ions

The outdoor insulator is commonly exposed to environmental pollution. The presence of water like raindrops and dew on the contaminant surface can lead to surface degradation due to leakage current. However, the physical process of this phenomenon is not well understood. Hence, in this study we develop a mathematical model of leakage current on the outdoor insulator surface using the Nernst Planck theory which accounts for the charge transport between the electrodes (negative and positive electrode) and charge generation mechanism. Meanwhile the electric field obeys Poisson’s equation. Method of Lines technique is used to solve the model numerically in which it converts the PDE into a system of ODEs by Finite Difference Approximations. The numerical simulation compares reasonably well with the experimental conduction current. The findings from the simulation shows that the conduction current is affected by the electric field distribution and charge concentration. The rise of the conduction current is due to the distribution of positive ion while the dominancy of electron attachment with neutral molecule and recombination with positive ions has caused a significant reduction of electron and increment of negative ions.

scholarly journals Electrical Breakdown in Air and in SF6

1995 ◽  
Vol 48 (3) ◽  
pp. 453 ◽  
Author(s):  
R Morrow ◽  
JJ Lowke
Keyword(s):  
Electric Field ◽  
Electric Field Distribution ◽  
Electrical Breakdown ◽  
Negative Ions ◽  
Continuity Equations ◽  
Positive Ions ◽  
Positive Space Charge ◽  
Attachment Coefficient ◽  
Positive Space ◽  
Positive Point

A theory is presented for the development of streamers from a positive point in atmospheric air. The continuity equations for electrons, positive ions, and negative ions are solved simultaneously with Poisson's equation. For an applied voltage of 20 kV across a 20 mm gap, streamers are predicted to cross the gap in 26 ns, and the calculated streamer velocities are in fair agreement with experiment. When the gap is increased to 50 mm for the same voltage, the streamer is predicted not to reach the cathode. In this case an intense electric field front rapidly propagates about 35 mm into the gap in 200 ns. For a further 9�5 �s the streamer slowly moves into the gap, until the electric field at the head of the streamer collapses, and the streamer front stops moving. Finally, only positive space-charge remains; this moves away from the point, allowing the field near the point to recover, giving rise to a secondary discharge near the anode. The electric field distribution is shown to be quite different from that found previously for SF6; this is explained by the much lower attachment coefficient in air compared with that in SF6. These results show that streamers in air have a far greater range than streamers in SF6. This greater range cannot be explained by comparison of the values of E*, the electric field at which ionisation equals attachment.

Using the effective recombination coefficient to constrain the positive ion composition in Saturn's ionosphere

2020 ◽  
Author(s):  
Joshua Dreyer ◽  
Erik Vigren ◽  
Michiko Morooka ◽  
Jan-Erik Wahlund ◽  
Stephan Buchert ◽  
...  
Keyword(s):  
Electron Temperature ◽  
Recombination Rate ◽  
Lower Ionosphere ◽  
Negative Ions ◽  
Rate Coefficients ◽  
Recombination Coefficient ◽  
Positive Ions ◽  
Electron Production ◽  
Upper Limits ◽  
Positive Ion

<p>We combine RPWS/LP and INMS data from Cassini's Grand Finale orbits into Saturn's lower ionosphere to calculate the effective recombination coefficient α<sub>300</sub> at a reference electron temperature of 300 K. Assuming photochemical equilibrium at altitudes below 2500 km and using an established method to determine the electron production rate, we derive upper limits for α<sub>300</sub> of ∼ 2.5∗10<sup>-7</sup> cm<sup>3 </sup>s<sup>-1</sup>, which suggest that Saturn's ionospheric positive ions are dominated by species with low recombination rate coefficients.<br />An ionosphere dominated by water group ions or complex hydrocarbons, as previously suggested, is incompatible with this result, as these species have recombination rate coefficients > 5∗10<sup>-7</sup> cm<sup>3 </sup>s<sup>-1</sup> at an electron temperature of 300 K. The results do not give constraints on the nature of the negative ions.</p>

On the effective recombination coefficient in Saturn's ionosphere

2020 ◽  
Author(s):  
Joshua Dreyer ◽  
Erik Vigren ◽  
Michiko Morooka ◽  
Jan-Erik Wahlund ◽  
Stephan Buchert ◽  
...  
Keyword(s):  
Electron Temperature ◽  
Rate Constants ◽  
Recombination Rate ◽  
Negative Ions ◽  
Dissociative Recombination ◽  
Rate Coefficients ◽  
Recombination Coefficient ◽  
Positive Ions ◽  
Electron Production ◽  
Upper Limits

<p>The present study combines RPWS/LP and INMS data from Cassini's orbit 292, which reached an altitude of 1685 km at the lowest point, to constrain the effective recombination coefficient α<sub>300</sub> from measured densities and electron temperatures at a reference electron temperature of 300 K. Assuming photochemical equilibrium at these low altitudes and linking established methods to calculate the electron production rate and the dissociative recombination rate results in a formula to calculate an upper limit for α<sub>300</sub>. This is then compared against rate constants of individual recombination reactions as measured in the laboratory.<br>We derive upper limits for α<sub>300</sub> of ∼ 2.5∗10<sup>-7</sup>cm<sup>3 </sup>s<sup>-1</sup>, which suggest that Saturn's ionospheric positive ions are dominated by species with low recombination rate coefficients. An ionosphere dominated by water group ions or complex hydrocarbons, as previously suggested, is incompatible with this result, as these species have recombination rate constants > 5∗10<sup>-7 </sup>cm<sup>3 </sup>s<sup>-1</sup> at an electron temperature of 300 K. The results do not give constraints on the nature of the negative ions.</p>

scholarly journals Simulation Study on Positive Corona Discharge of Receptors on Rotating Wind Turbine Blade Tips under Thundercloud Electric Fields

Energies ◽  
2019 ◽  
Vol 12 (24) ◽  
pp. 4696
Author(s):  
Lu Qu ◽  
Yu Wang ◽  
Gang Liu ◽  
Minchuan Liao ◽  
Hansheng Cai ◽  
...  
Keyword(s):  
Wind Speed ◽  
Corona Discharge ◽  
Electric Fields ◽  
Charged Particles ◽  
Multicomponent Diffusion ◽  
Ion Migration ◽  
Positive Ions ◽  
Corona Current ◽  
Blade Rotation ◽  
Discharge Model

Recent lightning simulation experiments have not simulated the influence of blade rotation in the long term after corona inception. This study uses a finite element method and considers the adhesion and collision processes of positive ions, aerosol ions, and neutral particles to establish a two-dimensional positive corona discharge model based on a multicomponent diffusion transport equation. The microscopic distribution of these three types of particles and the influence mechanism of charged particles’ migration under electric fields and wind were studied. The results show that ion migration is affected by both electric field and wind speed. The higher the wind speed, the larger is the deviation amplitude of charged particles along the direction of wind. With an increase in wind speed, the corona current on the receptor surface gradually increases. When the wind speed is 30 m/s, the corona current peak value increases by almost six times when compared with that when no wind is present. From this, it can be inferred that blade rotation reduces the concentration of positive ion in the receptor area, thereby facilitating electron avalanche and streamer-leader conversion.

scholarly journals Electron interaction with copper(II) carboxylate compounds

2018 ◽  
Vol 9 ◽  
pp. 384-398 ◽  
Author(s):  
Michal Lacko ◽  
Peter Papp ◽  
Iwona B Szymańska ◽  
Edward Szłyk ◽  
Štefan Matejčík
Keyword(s):  
Electron Attachment ◽  
Negative Ions ◽  
Electron Collision ◽  
Electron Interaction ◽  
Fragmentation Pattern ◽  
Complex Molecules ◽  
Positive Ions ◽  
Sequential Loss ◽  
Ion Yields ◽  
Resonant Processes

In the present study we have performed electron collision experiments with copper carboxylate complexes: [Cu2(t-BuNH2)2(µ-O2CC2F5)4], [Cu2(s-BuNH2)2(µ-O2CC2F5)4], [Cu2(EtNH2)2(µ-O2CC2F5)4], and [Cu2(µ-O2CC2F5)4]. Mass spectrometry was used to identify the fragmentation pattern of the coordination compounds produced in crossed electron – molecular beam experiments and to measure the dependence of ion yields of positive and negative ions on the electron energy. The dissociation pattern of positive ions contains a sequential loss of both the carboxylate ligands and/or the amine ligands from the complexes. Moreover, the fragmentation of the ligands themselves is visible in the mass spectrum below m/z 140. For the studied complexes the metallated ions containing both ligands, e.g., Cu2(O2CC2F5)(RNH2)+, Cu2(O2CC2F5)3(RNH2)2 + confirm the evaporation of whole complex molecules. A significant production of Cu+ ion was observed only for [Cu2(µ-O2CC2F5)4], a weak yield was detected for [Cu2(EtNH2)2(µ-O2CC2F5)4] as well. The dissociative electron attachment processes leading to formation of negative ions are similar for all investigated molecules as the highest unoccupied molecular orbital of the studied complexes has Cu–N and Cu–O antibonding character. For all complexes, formation of the Cu2(O2CC2F5)4 −• anion is observed together with mononuclear DEA fragments Cu(O2CC2F5)3 −, Cu(O2CC2F5)2 − and Cu(O2CC2F5)−•. All dominant DEA fragments of these complexes are formed through single particle resonant processes close to 0 eV.

Laboratory studies of electron attachment and detachment processes of aeronomic interest

1969 ◽  
Vol 47 (10) ◽  
pp. 1783-1793 ◽  
Author(s):  
A. V. Phelps
Keyword(s):  
Cross Sections ◽  
Ion Beam ◽  
Electron Attachment ◽  
Negative Ions ◽  
High Energy ◽  
Low Energy ◽  
Rate Coefficients ◽  
Dissociative Attachment ◽  
Three Body ◽  
Energy Processes

Techniques for the study of electron attachment and detachment are reviewed. The rate coefficients for the various processes of aeronomic interest are then discussed. The rates of three-body and dissociative attachment by thermal electrons have been successfully determined by swarm techniques and by high frequency studies of electrons produced by high energy particles and by photoionization. Collisional and associative detachment rates for thermal energy negative ions have been measured using the swarm and flowing afterglow techniques. Radiative attachment rates for some atmospheric negative ions have been calculated from measurements of photodetachment cross sections using crossed photon and ion beam techniques. Electron beam studies and measurements of ion kinetic energy have provided much useful information regarding the dissociative attachment process and the structure of molecular negative ions. Rate coefficients for low energy processes such as the three-body attachment to O2, the radiative attachment to O, and the associative detachment of O− in collisions with various atmospheric gases are reasonably well known. Other possibly important low energy processes, such as dissociative attachment to O3, radiative attachment to O2, and the associative detachment of O2− are less well known.

scholarly journals Учет тонкой структуры атомов щелочных металлов при неупругих столкновениях с водородом

2019 ◽  
Vol 127 (8) ◽  
pp. 207
Author(s):  
С.А. Яковлева ◽  
Я.В. Воронов ◽  
А.К. Беляев
Keyword(s):  
Fine Structure ◽  
Alkali Metal ◽  
Alkali Metals ◽  
Negative Ions ◽  
Rate Coefficients ◽  
Hydrogen Atoms ◽  
Positive Ions ◽  
Metal Atoms ◽  
Inelastic Processes

The method for calculations of rate coefficients for inelastic processes in collisions of alkali metal atoms and their positive ions with hydrogen atoms and its negative ions with accounting fine structure levels of alkali metals is proposed. The results of applications of the proposed method are reported in the present work on the examples of collisional systems KH and RbH.

Sensitive, Non-Intrusive, In Situ Measurements of Plasma Electric Fields

1983 ◽  
Vol 29 ◽  
Author(s):  
Richard A Gottscho ◽  
Cameron A. Moore ◽  
Glenn P. Davis
Keyword(s):  
Electric Fields ◽  
High Spatial Resolution ◽  
Band System ◽  
Absolute Measurement ◽  
Laser Induced Fluorescence ◽  
Rf Discharge ◽  
Electrode Surfaces ◽  
Charged Particle Transport ◽  
A New Technique

ABSTRACTWe report a new technique for the in situ, non-intrusive, and sensitive measurement of plasma electric fields with high spatial resolution. Fields as small as 40 V/cm can be characterized by spectrally resolving laser-induced fluorescence from Stark-mixed parity levels. The technique is demonstrated by exciting the A1 11−X 1Σ+ band system of BC1, produced in an rf discharge through BCI3. The characterization and absolute measurement of sheath fields, which have been elusive, are now possible. These fields are preeminent in governing charged particle transport to and between electrode surfaces and in maintaining the glow discharge.

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