Plasma instability between polycrystalline rhenium electrodes in a cesiated thermionic diode

The study of self‐maintained plasma oscillation is performed with a spectrum analyzer to evaluate the electron‐ion interaction mechanism between polycrystalline rhenium electrodes in a variable‐spacing cesium thermionic energy converter (TEC). The phenomenon of spectrum damping brought about by increasing cesium vapor pressure and the broadness of the bandwidth (Δf=250 kHz) in the observed spectrum, at emitter temperatures in the range of 1300 to 1550 K, indicates qualitatively that the volume ionization is the dominant collision process within a bounded plasma.