Measurement of barium emitted from thermionic electrodes in steady-state Hg-rare gas discharges

Summary form only given. Using atomic absorption we measure the densities of neutral and ionic barium in the vicinity of the barium oxide coated electrodes in low pressure Hg-rare gas discharges. The technique is sensitive to the small amount of barium that evaporates from the electrode during a steady state discharge. It uses a current modulated barium hollow cathode lamp light source and a phase sensitive detector. In the present work we concentrate on comparing barium densities with electrode temperature. Spatially resolved electrode temperature is measured with a thermal emission based diagnostic developed previously. Comparisons are made with respect to variations of key discharge parameters, such as current and rare gas pressure. As such, we investigate in detail the connection between the electrode temperature and the presence of free barium in the discharge.