Cage discharge: theory and experiment

A theoretical and experimental study of the plasma formation in a so-called cage discharge is presented. The cage discharge can be attributed to a hollow cathode discharge of a specific geometry. A large longitudinally extended uniform plasma of negative (field-free) glow is generated. Many interesting properties of such a plasma source are found, which can make it a very attractive tool to be used for diverse applications. A self-consistent analytical model of such a discharge is proposed. The most important mechanisms involved in the formation of the electron distribution function in the whole energy range are identified. The theoretical results are compared to experimental observations of radial distributions of different atomic and ionic He lines, which are used to determine the spatial locations of different groups of fast electrons. Probe measurements of the electron distribution function (in the elastic energy range), carried out over a wide range of experimental conditions and at different locations in the plasma volume, are compared to theoretical predictions. Energy and charged particles balance equations are obtained. A condition of self-sustaining of such a discharge is suggested and voltage-current characteristics are calculated. On the whole, a satisfactory agreement is found between predicted and observed plasma parameters.