A highly effcient thermionic cathode for thermionic emission and energy conversion

We have developed a highly efficient thermionic cathode that exhibits both strong thermionic emission and thermionic energy conversion (cooling). The cathode consists a triple coiled tungsten filament as its base and the barium strontium oxide coated carbon nanotubes (CNTs) as its emitters. The cathode produces a strong thermionic emission of around 3 A/cm2 at 1400 K. It operates at a much lower cathode fall voltage in a low-pressure Ar plasma, confirming its high efficiency in electron emission. The cathode also exhibits high efficiency in thermionic energy conversion, a large thermionic cooling effect of the emitting cathode surface was observed as a result hot electron emission. Details of the cathode structure and its fabrication process will be presented, along with the measurement results on thermionic emission, cathode fall in plasma environment and thermionic cooling of the emitting surface.