Characteristic models

Langmuir comes with several models for the characteristic of Langmuir probes. Each model is represented by a function which, in addition to the voltage V, take a geometry and a species argument. The models have similar signatures and can often be interchanged. geometry is one of the previously mentioned probe geometries (Plane, Cylinder or Sphere), and the species argument is either a single Species object, or a list of Species. If it is a single species, the return value is the current collected from that species alone. This may be sufficient in regimes where the current is dominated by the collection of one species. If the species argument it is a list of species, it is the sum of the currents from all species (there is currently no model which accounts for non-linear coupling between species). If both ions and electrons are included, the characteristics captures both the electron saturation, electron retardation and ion saturation regimes. The model functions also have arguments eta and normalization which will be covered in Normalization.

Contents:

• Analytical theories
  • The orbital motion-limited (OML) theory
  • Thermal currents and the sheath-limited (SL) theory
• Normalization
• Finite length models
  • Current per unit length
  • Total collected current
  • Behind the curtains
• Finite radius models