In principle, it is not possible to interpret a Langmuir probe in a strong magnetic field since the modelling of non-ambipolar cross-field transport is uncertain. In some circumstances the portion of the probe I-V characteristic below floating potential may not be contaminated by magnetic field effects, and it can be possible to extract ne and Te from such data; unfortunately, it is not known with any certainty when this situation holds. By using a special probe with a small collecting element (pin) just in front of the principal collecting element (plate) it is possible to correct for the influence of the magnetic field, and to use simple single-probe theory to extract ne and Te. The uncertain influence of the non-ambipolar cross-field transport is entirely circumvented. Using such a probe it is possible to also use the part of the I-V characteristic above floating potential; thus, if the electron distribution is non-Maxwellian, that can be measured.
Analytical density correction for cylindrical Langmuir probes showing end effects