This paper presents a simplified theoretical model for a phenomenon of fast randomization of an electron gas, investigated experimentally in this laboratory. It is assumed that a certain region in constricted electrical discharges, called 'plasma sac' can become the siege of trapped electro-acoustic waves generated by a beam-plasma interaction. The interaction between those waves and the electron gas is treated by a pseudo collisionM method, leading to a generalization of Boltzmann's H theorem. The velocity distribution which is essentially Maxwellian with a significant deficiency in the fast electron tail, is deduced. Β§ 1. The experimental observations
The experimental facts relevant to this investigation have been presented in full detail elsewhere Ell. In this paper only the basic facts with respect to the current theoretical investigations will be presented.
The investigation concerns phenomena occurring in the special region of constricted electrical discharges known in the literature (see e.g. [2]) under the name 'plasma sac'. When a discharge is locally constricted by walls, the cathodic extremity of the constricted part is prolonged by a luminous extension of the bright constricted column. This extension is called 'plasma sac', it projects into the less luminous column, from which it is separated by a space charge region called 'double sheath'. The double sheath consists of a negative layer on the cathode side and a positive layer on the anode side (Fig. 6). The theory of the double sheath was first es-*) Now with the University of Pittsburgh, Pittsburgh (Penn.), U.S.A.