The inadequate reference electrode, a widespread source of error in plasma probe measurements

Publisher Website
Google Scholar
Abstract
An analysis has been conducted on the influence of the reference electrode area on probe characteristics taken in the electron retarding range of potentials, when the reference electrode, and perhaps also the probe, is in the `blocking effect' régime (where probe dimensions are greater than or equal to the electron and ion mean free paths). A new and more severe criterion for sufficiency of reference electrode area is derived, and it is shown that insufficiency of reference area can lead not only to rounding of the `knee' of the probe characteristic, but can cause an extra, spurious, near-linear section to appear in the (log current against potential) characteristic near space potential, leading to the possibility of grossly inaccurate electron temperature measurements. A number of published results are cited to show that this phenomenon is in fact a frequent source of error in probe measurements.