Skip to Main Content
Laframboise' probe theory in the cylindrical case has been reformulated so that solutions may be obtained easily in a mathematical spreadsheet. Sheath potential profiles and probe currents are given for several cases including probes with radii that are sufficiently large for a potential barrier that results in electron current collection less than that given by the orbit-motion-limited theory. For probes with radii in the range of 1-50 Debye lengths and for electron-to-ion temperature ratios of 1 and 10, the electron current at a fixed bias potential is found to be dependent upon the electron-to-ion temperature ratio because the ions affect the height of the potential barriers. The ion current is found as a function of voltage for probes with radii of 3, 10, and 50 Debye lengths and for electron-to-ion temperature ratios of 1 and 10. The normalized ion current is of the same order as the Bohm current, but the probe characteristics show no ??ion saturation current?? and show a dependence upon both the probe radius and the temperature ratio.