plasmapy.diagnostics.langmuir.get_ion_density_LM(ion_saturation_current: Quantity, T_e: Quantity, probe_area: Quantity, gas) Quantity[source]

Implement the Langmuir-Mottley (LM) method of obtaining the ion density.

  • ion_saturation_current (Quantity) – The ion saturation current in units convertible to A.

  • T_e (Quantity) – The electron temperature in units convertible to eV.

  • probe_area (Quantity) – The area of the probe exposed to plasma in units convertible to m2.

  • gas (Quantity) – The (mean) mass of the background gas in atomic mass units.


n_i – Estimate of the ion density in units convertible to m-3.

Return type:



The method implemented in this function obtains the ion density from the ion saturation current density assuming that the ion current loss to the probe is equal to the Bohm loss. The acoustic Bohm velocity is obtained from the electron temperature and the ion mass.

The ion saturation current is given by

\[I_{is} = 0.6 e A_p n_i \sqrt{\frac{T_e}{m_i}}.\]