Characteristics of a Langmuir Probe in a Magnetic Field with High Sweep Frequencies

New, dynamic effects in the characteristic of a Langmuir probe in a strong magnetic field have been identified experimentally and by numerical simulation. The frequency limit of the quasi-static theory of a classical Langmuir probe in a non-magnetized plasma, is ωpi. In a magnetic field, however, the Langmuir characteristic already contains capacitive hysteresis loops on the electron or the ion saturation side, at much lower frequencies than ωci. These can be explained by the ion polarisation current, perpendicular to the magnetic field. The relevant frequencies are determined by the geometry of the return path of the Langmuir current, and by the angle of the magnetic field to the probe surface.