get_ion_density_OML
- plasmapy.diagnostics.langmuir.get_ion_density_OML(
- probe_characteristic: Characteristic,
- probe_area: Quantity,
- gas,
- visualize: bool = False,
- return_fit: bool = False,
Implement the Orbital Motion Limit (OML) method of obtaining an estimate of the ion density.
- Parameters:
probe_characteristic (
Characteristic
) – The swept probe characteristic that is to be analyzed.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.visualize (
bool
, optional) – IfTrue
a plot of the OML fit is shown. Default isFalse
.return_fit (
bool
, optional) – IfTrue
the parameters of the fit will be returned in addition to the ion density. Default isFalse
.
- Returns:
n_i_OML – Estimated ion density in m-3.
- Return type:
Notes
The method implemented in this function holds for cylindrical probes in a cold ion plasma, i.e. :math:T_i=0` eV. With OML theory an expression is found for the ion current as function of probe bias independent of the electron temperature [mott-smith.langmuir-1926]:
\[I_i \xrightarrow[T_i = 0]{} A_p n_i e \frac{\sqrt{2}}{π} \sqrt{\frac{e \left( V_F - V \right)}{m_i}}\]References
[mott-smith.langmuir-1926]H. M. Mott-Smith, I. Langmuir, Phys. Rev. 28, 727-763 (Oct. 1926)