Characteristics of Langmuir Probe in a Strong Magnetic Field

The mechanism of the collection of charged particles by a Langmuir probe in a strong magnetic field is theoretically investigated. The magnetic field is assumed to be sufficiently strong, i.e. the electron cyclotron frequency exceeds the collision frequency of electrons with neutral gas molecules, and the following results are obtained: When the length of the probe in the direction of the magnetic field is larger than the average gyration diameter of electrons, the probe current is determined by the gyration diameter, whereas when the probe length is smaller, the probe current is free from the effect of the magnetic field. Discussions are also given for the case where as electric field exists between the probe and the plasma. Experimental results concerned with the saturation electron current agree with the calculated values.