An analysis was made of the-possible thermionic eléctron-emission currents attainable from cesium-coated tungsten accelerator electrodes in ion thrustors. Both an axisymmetric and a rectangular electrode configuration were examined for accelerator temperatures near the values yielding maximum emission. The electron-emission behavior was substantially the same for both configurations. An electron-emission current equal to about 4 percent of the ion-beam current is possible for cases where the neutral-cesium flux to the accelerator electrode comes directly from the ionizer. If a background gas pressure of cesium can build up in the interelectrode space, thermionic electron-emission currents as high as 40 percent of the ion-beam current can result. These values of electron, current are of sufficient magnitude to obscure measurements of the true ion-impingement currents on the accelerator electrode.
展开▼
