title: Effect of filament supports on emissive probe measurements.
abstract: We have constructed an emissive probe with a thin tungsten filament spot-welded across two nickel wires insulated with ceramic paint. We show that the ceramic supports covering the nickel wires have a large effect on the potential measurements in low-density plasmas. It is found that the potential measured by the emissive probe is more negative than the potential derived from a Langmuir probe current-voltage (I-V) characteristic curve when the plasma density is so low that the emitting filament remains immersed in the sheaths of the ceramic supports. The length of the filament L needs to be larger than about 2 Debye lengths (L > 2λ(De)) in order to avoid the influence of the ceramic supports and to achieve reliable plasma potential measurements using emissive probes.
authors: Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, Colorado 80309, USA.
authors: X
authors: X
authors: Wang
authors: C T
authors: CT
authors: Howes
authors: M
authors: M
authors: Horányi
authors: S
authors: S
authors: Robertson