Area Influences and Floating Potentials in Langmuir Probe Measurements
- 1 March 1972
- journal article
- Published by AIP Publishing in Journal of Applied Physics
- Vol. 43 (3), 874-880
- https://doi.org/10.1063/1.1661297
Abstract
An analysis has been conducted on the influence of a relatively small reference electrode in a Langmuir probe measurement of plasma density and temperature. The analysis employs the collisionless theory of Laframboise for spherical and cylindrical probes and in a completely general way includes a broad range of electron densities and temperatures as well as all possible values of ion mass and multiplicity of ionization. It is shown that a ratio α of reference‐electrode area to probe area of 104 will guarantee no distortion of the measurement as a result of a shifting reference‐electrode potential. It is further shown that the constraint on α can be relaxed by approximately two orders of magnitude when the charge‐normalized ion mass mi/Z2 is decreased from 200 to 1 amu and the ratio of reference‐electrode radius to Debye length, Rr/λD, is decreased from 100 to 0. An additional result of the analysis is the dependence of a probe's floating potential on its geometry and radius as well as on the properties of the plasma. A discussion of the latter result reveals in a striking manner the significant differences between the ion‐current responses of spherical and cylindrical probes.Keywords
This publication has 9 references indexed in Scilit:
- Accuracy of Langmuir probe measurements and skin potential on satellitesJournal of Geophysical Research, 1971
- A comparison of the methods of determining electron densities in afterglow plasmas from langmuir probe characteristicsPlasma Physics, 1968
- Perturbation of Electron Energy Distribution by a ProbeJournal of Applied Physics, 1966
- Free-molecule Langmuir probe and its use in flow-field studies.AIAA Journal, 1966
- Ionospheric electron density and body potential measurements by a cylindrical Langmuir probeJournal of Geophysical Research, 1965
- Multiple Probe Measurements in High-Frequency Plasma LasersJournal of Applied Physics, 1964
- Theory of Electrostatic Probes in a Low-Density PlasmaPhysics of Fluids, 1959
- Dynamic probe measurements in the ionosphereJournal of Geophysical Research, 1953
- The Theory of Collectors in Gaseous DischargesPhysical Review B, 1926