Negative Characteristic of a Cylindrical Probe in a Magnetic Field

A magnetic field, impairing the transverse motion of electrons across it, causes a negative current-voltage characteristic to a cylindrical probe whose axis is along the field. This occurs above a certain magnetic field at a low pressure range in neon, argon, krypton, and mercury plasmas. The analysis of this phenomenon is made by using the orbital motion theory inside the sheath. The maximum point in this characteristic is proved to be the space potential. The conventional method for determining the number of concentration of charge particles from this point, however, is no longer valid. The positive ion saturation current is shown to remain useful below 3.3 A 1/2 kilogauss, where A is the atomic mass number of ions.