Thermionic Converter

A thermionic converter consists of a hot electrode which thermionically emits electrons across a potential energy barrier to a cooler electrode, producing a useful electric power output; caesium vapor is often used inside the device to optimize the electrode work functions and to supply ions that neutralize the emitted electrons own space charge. Viewed from physical electronics, thermionic conversion is the direct production of electric power from heat through thermionic electron emission, and from a thermodynamic viewpoint it can be understood as using an electron vapor as the working fluid of a power-producing cycle, with the hot emitter electrode vaporizing electrons that condense at the colder collector electrode after conducting through the plasma between them. A typical converter delivers several amperes of current per square centimeter of emitter surface at a potential difference of only about 0.5 to 1 volt, with thermal efficiency of roughly 5 to 20 percent depending on the emitter temperature, which usually runs between 1500 and 2000 kelvin.