What roles do the emitter and collector play in a thermionic power converter?

In a thermionic power converter, the emitter and collector function as the two primary electrodes that facilitate the direct conversion of heat into electricity.1

• The Emitter: This electrode is heated to a high temperature, causing it to act as a source of thermionic emission. By supplying thermal energy, the emitter liberates electrons from its surface. The efficiency of this process depends on the material's electronic work function and the operating temperature, as described by the Richardson–Dushman equation.1
• The Collector: This electrode is maintained at a significantly lower temperature than the emitter. Its role is to receive the electrons emitted from the hot plate. As these electrons strike the collector, a portion of their energy is harnessed to drive an electric current through an external load, completing the conversion of thermal energy into electrical energy.1

To maintain the converter's operation, the collector must be cooled to remove the heat generated by the incoming electrons.1