a thermionic converter consists of a hot electrode which thermionically emits electrons over a potential energy barrier to a cooler electrode, producing a useful electric power output. caesium vapor is used to optimize the electrode work functions and provide an ion supply (by surface ionization or electron impact ionization in a plasma) to neutralize the electron space charge. == definition == from a physical electronic viewpoint, thermionic energy conversion is the direct production of electric power from heat by thermionic electron emission. from a thermodynamic viewpoint, it is the use of electron vapor as the working fluid in a power-producing cycle. a thermionic converter consists of a hot emitter electrode from which electrons are vaporized by thermionic emission and a colder collector electrode into which they are condensed after conduction through the interelectrode plasma. the resulting current, typically several amperes per square centimetre of emitter surface, delivers electrical power to a load at a typical potential difference of 0.5&ndash;1 volt and thermal efficiency of 5&ndash;20%, depending on the emitter temperature (1500&ndash;2000 k) and mode of operation. == history == after the first demonstration of the practical arc-mode caesium vapor thermionic converter by v. wilson in 1957, several applications of it were demonstrated in the following decade, including its use with solar, combustion, radioisotope and nuclear reactor heat sources. the application most seriously pursued, however, was the integration of thermionic nuclear fuel elements directly into the core of nuclear reactors for production of electrical power in space.{{cite journal| last = mills| first = joseph c.|author2=richard c. dahlberg | title = thermionic systems for dod missions| journal = american institute of physics conference proceedings| volume = 217| issue = 3| pages = 1088â92| date = january 10, 1991| url = http://link.aip.org/link/?apcpcs/217/1088/1| doi = 10.1063/1.4006
Battery_types Electric_power Electrical_generators Nuclear_power_in_space Nuclear_technology