Langmuir probe characteristics in a high pressure plasma in the presence of convection and ionization

The current to a Langmuir probe operating in a high pressure flowing plasma is calculated for the case where convection of electrons or ions into the sheath adjacent to the probe and thermal generation of electrons and ions within the sheath can both be significant factors in determining probe current. In addition to generating explicit relations for planar, spherical and cylindrical probes for the asymptotic case in which only generation need be considered, a solution is also obtained for the extensive transition between this state and the purely convective state, for which explicit solutions already exist. The theory, which enables the electron/ion density to be calculated from the probe current is applicable to both positive and negative probes