Particle densities in high current hollow cathode discharges

Abstract

Operating hollow cathode discharges at current densities in excess of 0.1 A/cm2 leads to an efficient production of metal vapor via the process of cathode sputtering. This method of metal vapor production has been exploited in numerous metal ion laser devices and in spectroscopic light sources. In this paper the main processes involved in high current hollow cathode discharges will be discussed for the special case of a Ne–Cu discharge that can be regarded as representative for other sputtering hollow cathode discharges. Starting from a set of balance equations, expressions for the current density dependence of the spatially averaged buffer gas ion-, metal ion-, and metal atom-density are derived. These expressions are verified experimentally by measurements of the spontaneous emission of a Cu II line and yield in a simple manner realistic data of these particle densities. Finally the obtained results are related to the characteristics of a Cu II laser.