Wall conduction in a highly magnetized plasma

Abstract

The electron current along the electric field might appear to tend to zero for Wer e--~ ~ in a low-density completely ionized plasma in mutually perpendicular electric and magnetic fields; but this current is not small in all known real systems, and, in any case, it is larger by many orders of magnitude than that calculated from classical formulas. This anomalous conductivity is usually ascribed to noise in the plasma.

However, there is a class of plasma systems for which the anomalous conductivity can be explained, at least partially, in a different way; in this class we should include homopolar systems and also certain accelerators. These systems have insulated walls met almost at right angles by the magnetic field lines, and the electric field lies almost exactly along the wall.

If the plasma density is so small that the electron mean free path is much greater than the transverse size of the channel (along the magnetic field), the conductivity of the discharge gap should be affected by the collisions of the electrons with the wall. This effect tends to be of regular character, in contrast to noise; it should appear in some form even when the magnetic field is zero, but the effects of collisions of electrons with the wall become clearer when the magnetic field is strong, since the ordinary conductivity of the plasma is largely suppressed.