Cathode fall behavior in a Hg-rare gas discharge with a thermionic cathode

Summary form only given. Using a Langmuir probe, we have made cathode fall measurements, over a wide range of discharge parameters, for a barium oxide coated, thermionic emitting cathode in a Hg-Ar discharge. These measurements agree well with the results of a recently developed model. Cathode fall (plasma potential near the cathode), as well as electron density and temperature were derived from the second derivative of the probe I-V characteristic. The experimental configuration allowed for axial and radial mapping of the plasma parameters in the entire negative glow of the discharge. As such, we present an extensive parameter study of the negative glow of a Hg-Ar discharge.