VOLTAGE CURRENT-DENSITY CHARACTERISTICS OF NOBLE-GAS MIXTURE DISCHARGES IN THE CATHODE REGION

Voltage-current density (V-j) characteristics were studied in the cathode region of noble gas mixture glow discharges. Measurements were carried out in He-X (X = Ne, Ar, Kr, Xe) mixtures in plane cathode and hollow cathode arrangements. The partial pressure of the admixed gas was maximum 2% of the total pressure. It was found that at constant voltage the current density increased by mixing Ar to He, while it decreased when Ne, Kr or Xe were added. Above a certain partial pressure value the current density was found to increase again in the case of Ne and Kr admixtures. In He-Xe it decreased, however, in the whole range investigated. These observations are explained, taking into account ionization processes and the differences in secondary electron emission coefficients.