The operation of a cesium plasma thermocouple is described for a range of hot-junction temperatures from 1600°K to 2600°K and for a range of cesium pressures from 10−5 mm Hg to 2 mm Hg. Electromotive force and short-circuit current data are presented for cells containing three different emitter substances: Ta, ZrC, and (ZrC) (UC). In the range of pressure and temperature variation studied, the observed electromotive forces are between 1 and 4.5 volts. Short-circuit current depends markedly on the current emission properties of the hot electrode. The largest short-circuit current density observed for the (ZrC) (UC) emitter, is 62 amperes per square centimeter.
Uranium carbide is found to have the property of high thermionic emission in the observed temperature range from 1400 to 1800°K. The parameters of the Richardson equation which can be used to fit the data are A=7.3×105 amp/cm2 (°K)2 and φ=4.57 v. While these parameters accurately predict the observed saturated currents, it is doubtful that such anomalous values are of theoretical significance within the framework of the Richardson-Dushman derivation. A solid solution form of uranium carbide and zirconium carbide gives substantially the same thermionic emission as uranium carbide, and for other reasons appears to be the more useful emitter. The carbides require no surface preparation or activation schedule for use as emitters.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.