Theory of Ion Boundary Layers

Johnson, Roberta; Boer, P. C. T. de

doi:10.2514/3.50173

Cited by 15 publications

(6 citation statements)

References 23 publications

(22 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Therefore we concentrated on the effect of collisions on positive-ion collection by a Langmuir probe. This effect has already been studied extensively; examples of earlier papers on this subject are [13][14][15][16][17][18][19][20][21][22]. Qualitatively speaking the effect of collisions on the positive-ion collection is demonstrated in two ways:…”

Section: The Influence Of Ion-neutral Collisions On Probe Measurementsmentioning

confidence: 99%

An experimental study of plasma density determination by a cylindrical Langmuir probe at different pressures and magnetic fields in a cylindrical magnetron discharge in heavy rare gases

Passoth

Kudrna

Csambal

et al. 1997

J. Phys. D: Appl. Phys.

View full text Add to dashboard Cite

This article presents an experimental study that contributes to the problem of interpretation of cylindrical Langmuir probe data obtained in a non-isothermal low-temperature plasma in magnetic field. A discussion on the influence of positive ion - neutral collisions on the charged particle density estimation is also given and the effect is demonstrated on the experimental data. A Maxwellian electron energy distribution is assumed throughout the present study. The Langmuir probe data are obtained in a cylindrical magnetron discharge in argon at pressures from 1.5 to 6 Pa and magnetic fields between 100 and 500 G. The radially movable Langmuir probe was made of either m or m diameter tungsten wire in order to investigate the effect of the probe dimensions on the estimated plasma density. The electron density is calculated from the electron current at the space potential (used as a reference) and from the OML collisionless theory. The ion density is calculated by using ABR - Chen theory without and with the correction due to the collisions of positive ions in the probe sheath. Also, the recent collisional positive-ion-collection-theory is used for comparison. The resulting numerical values of plasma density are compared over more than one order of magnitude change in the plasma density given by its radial dependence in the cylindrical magnetron discharge. Optical measurements were made in order to quantitatively assess the neutral gas temperature in the discharge and the density of particles in excited states that could induce secondary electron emission from the probe surface and thus apparently enhance the positive-ion density estimated from the probe positive-ion current. The effect of secondary electron emission from the probe surface on the probe data interpretation has been found small compared to the experimental error limits and consequently not substantial for our experimental conditions. In the range of our experimental conditions the ABR - Chen theory with the collisional correction gives the best agreement of the estimated numerical values of ion and electron densities in the whole range of its investigated change. Also from our results it follows that the effect of the magnetic field on the thinner-probe-electron-current at the space potential and hence on the reference-electron-density-estimation is negligible within the experimental uncertainties up to a magnetic field strength of 500 G which was the maximum used in our experimental study.

show abstract

Section: The Influence Of Ion-neutral Collisions On Probe Measurementsmentioning

confidence: 99%

An experimental study of plasma density determination by a cylindrical Langmuir probe at different pressures and magnetic fields in a cylindrical magnetron discharge in heavy rare gases

Passoth

Kudrna

Csambal

et al. 1997

J. Phys. D: Appl. Phys.

View full text Add to dashboard Cite

show abstract

“…This correction has been considered in Ref. 12, and tends to decrease -/. The other correction arises from the effect of diffusion near the edge of the sheath.…”

Section: Ion Boundary Layer On a Flat Plate 1017mentioning

confidence: 94%

“…Ref. 12). The coordinate of the point where TJ* = r\ s is given by £, % 0.52co 2 (for co = 230, £ f w 2.7 x 10 4 ).…”

Section: Ion Boundary Layer On a Flat Plate 1017mentioning

confidence: 99%

“…The convective effects are characterized by the parameter R if the electric effects by the independent parameter co 1/2 . The appropriate mathematical procedure for this case is to stretch both the jq and the x 2 coordinate by setting {=*!/*" 7/-X2/C0 1 / 2 (12) It is assumed that R t , co 112 and I//? all are large, with R t large compared with co 1/2 .…”

Section: Flow Over Flat Platementioning

confidence: 99%

See 1 more Smart Citation

Ion boundary layer on a flat plate.

Boer

1973

AIAA Journal

Self Cite

View full text Add to dashboard Cite

A formal asymptotic theory is presented for the flow of a slightly ionized, continuum gas past a flat plate at large negative electric potential, in the limit of large ion Reynolds number. The appropriate equations are solved by a perturbation method. To lowest order there is an outer region where the flow is unperturbed, and an ion sheath region which is adjacent to the plate. Between these two regions there is a transition region. By solving the equations for the transition region in the next higher order, and by using the method of matched asymptotic expansions, appropriate boundary conditions are found for the ion sheath region. The downstream solution for all quantities of interest in the latter region is obtained by the method of characteristics.

show abstract

“…In general the problem of calculating the current collected by a probe immersed in a continuum plasma is very difficult. However, in many situations where one is only interested in the collection of ion currents by a very negatively biased probe, the problem can be approximated with quite reasonable accuracy by the following model which is discussed in some detail by Kulgein (1968), de Boer and Johnson (1968), Johnson and de Boer (1972) and Clements and Smy (1969). In this model the negative probe is surrounded by a positive space-charge sheath in which essentially all the potential change…”

Section: Introductionmentioning

confidence: 99%

The planar continuum plasma sheath with regeneration and convection of ionization

Noor¹,

Smy²,

Clements³

1977

J. Phys. D: Appl. Phys.

View full text Add to dashboard Cite

Measurements are described on a planar sheath established in a moving flame plasma seeded with potassium. By varying the quantity of seed the ionization density of the flame is altered so as to allow a range of sheath current-voltage characteristics which vary from saturation at low densities to a substantial voltage dependence at high densities. When the sheath is suddenly collapsed the ionization within what was the sheath region is observed to recover towards its equilibrium value. Measurements of current density, ionization density, and sheath thickness taken during these experiments show good agreement with a sheath model in which convection and/or ionization regeneration act as the supply of ions to the sheath.

show abstract

Theory of Ion Boundary Layers

Cited by 15 publications

References 23 publications

An experimental study of plasma density determination by a cylindrical Langmuir probe at different pressures and magnetic fields in a cylindrical magnetron discharge in heavy rare gases

An experimental study of plasma density determination by a cylindrical Langmuir probe at different pressures and magnetic fields in a cylindrical magnetron discharge in heavy rare gases

Ion boundary layer on a flat plate.

The planar continuum plasma sheath with regeneration and convection of ionization

Contact Info

Product

Resources

About