Anode phenomena of thermionic electrodes

Summary form only given. Most studies of discharge-plasma electrode interaction focus on cathode related phenomena. The cathode´s main function is to emit electrons while the anode´s main function is to absorb electrons. For bipolar discharges, as current goes through a current zero the electrode undergoes a transition from electron emission to electron absorption. In an attempt to understand this transition, observations have been made of low work function electrodes during anode and cathode operation in low pressure (a few Torr) rare-gas Hg discharges. The discharge is driven by square wave currents with 10´s to 100´s of mA RMS current. Time dependent cathode and anode fall measurements are measured using probe techniques and time dependent hot spot temperature measurements are inferred from observations of the infrared radiation emitted from the electrode. Time resolved plasma images are presented in an attempt to describe how the plasma attaches to the electrode during the anode phase of the discharge.