Characteristics of a Plasma Thermocouple

Abstract

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.

Plasma Thermionic Converters

“…Also, since the hot wall is only one-half the container and must supply all the electrons which are picked up by the collector one runs into electron emission limitations from the hot wall. Despite these experimental difficulties 30 watt/cm ~ has been observed by increasing both the cesium pressure and emitter temperature (3). With this geometry the maximum short circuit current was about 60 amp/cm 2.…”

Materials Problems in Cesium Thermionic Converters

“…The positions of M relative to that of N depend on the magnitude of the output voltage, V. As long as ~ ~ ~A + V, the energy barrier for electron emission from the cathode is always r (see Fig. 2 a and b), and the current reaching the anode, i.e., the output current, I, assuming zero plasma impedance and negligible back [1] where A is a temperature-and material-independent constant with a theoretical value of 120 amp/ cmf-~ TK is the temperature of the cathode, and k is the Boltzmann constant. Therefore, for V --~ r162 I is a constant at a given temperature T~.…”