Current-Voltage Characteristic of a Partially Ionized Plasma in Cylindrical Geometry

The properties of a partially ionized plasma in a long cylindrical tube subject to a uniform axial electric field are investigated. The plasma is maintained by an external ionizing source balanced by bulk and surface recombinations. Collisions between neutrals, whose density greatly exceeds the density of charged particles, and of neutrals with ions are sufficiently effective for their velocity distribution to be close to a Maxwellian with the same uniform temperature, independent of the external field. The behavior of the plasma is described by a collisional two-fluid scheme with charge neutrality in the interior of the tube. Approximate nonlinear equations for the hydrodynamical moments are obtained from a Boltzmann equation in which electron-neutral, electron-ion and electron-electron collisions are all important. It is found that under certain circumstances the current, and the temperature of the electrons undergo a drastic change, with hysteresis, as the electric field is varied.