An experimental study of plasma density determination by cylindrical Langmuir probe in a flowing afterglow plasma at elevated pressures
- Charles Univ., Prague (Czech Republic); and others
The collection of positive ions by a cylindrical Langmuir probe at the pressures when the ion mean free path is much shorter than the probe sheath thickness (usually called the collisional case of positive ion collection) has been treated by several authors. The idea, that the ions can only be scattered by collisions with neutral particles and hence the effect of collisions results in the reduction of the ion current to the probe had to be corrected owing to the experimental facts which showed that the ion current in the presence of collisions can be greater than in the collisionless; case and hence results in greater apparent ion density compared to the electron one. A simple explanation of the fact that the ion current can be increased by the effect of collisions of positive ions with neutrals, has been brought up by Zakrzewski and Kopiczynski in and was based on the fact that the collisions can destroy the ion orbital motion in the space charge sheath surrounding the Langmuir probe and the ions have hence greater chance to be collected by the probe. The upper limit for the ion current increase has been set in to be the current calculated by the radial motion theory by Allen, the collisionless, current limit has been taken after Laframboise. Quantitatively this effect is described by a factor {gamma}{sub 1} which ranges from 1 in the collisionless case to the ratio I{sub A}/I{sub L}, where I{sub A} and I{sub L} are the ion collisionless. Simultaneously it is supposed in the work that the collisions can scatter ions which leads to the decrease of the ion current, the effect is described quantitatively by a factor {gamma}{sub 2}.
- OSTI ID:
- 212858
- Report Number(s):
- CONF-950749-; CNN: Grant GACR-0295; Grant GAUK-306; TRN: 96:010027
- Resource Relation:
- Conference: 22. international conference on phenomena in ionized gases, Hoboken, NJ (United States), 31 Jul - 4 Aug 1995; Other Information: PBD: 1995; Related Information: Is Part Of XXII International conference on phenomena in ionized gases. Contributed papers 2; Becker, K.H.; Carr, W.E.; Kunhardt, E.E. [eds.]; PB: 226 p.
- Country of Publication:
- United States
- Language:
- English
Similar Records
Current collection by a cylindrical probe in a partly ionized, collisional plasma
Particle-in-cell simulations of planar and cylindrical Langmuir probes: Floating potential and ion saturation current