Orbital motion theory and operational regimes for cylindrical emissive probes Articles uri icon

publication date

  • February 2017

start page

  • 1

end page

  • 9

issue

  • 2

volume

  • 24

International Standard Serial Number (ISSN)

  • 1070-664X

Electronic International Standard Serial Number (EISSN)

  • 1089-7674

abstract

  • A full-kinetic model based on the orbital-motion theory for cylindrical emissive probes (EPs) is presented. The conservation of the distribution function, the energy, and the angular momentum for cylindrical probes immersed in collisionless and stationary plasmas is used to write the Vlasov-Poisson system as a single integro-differential equation. It describes self-consistently the electrostatic potential profile and, consequently, the current-voltage (I-V) probe characteristics. Its numerical solutions are used to identify different EP operational regimes, including orbital-motion-limited (OML)/non-OML current collection and monotonic/non-monotonic potential, in the parametric domain of probe bias and emission level. The most important features of the potential and density profiles are presented and compared with common approximations in the literature. Conventional methods to measure plasma potential with EPs are briefly revisited. A direct application of the model is to estimate plasma parameters by fitting I-V measurements to the theoretical results.

keywords

  • space-charge; electron-emission; collisionless plasma; langmuir probe; limited regime; sheath; collection