Initial studies of an annular cesium iodide cathode

Summary form only given. Cesium iodide (CsI) cathodes have been a topic of research in recent years as efforts have mounted to find a material that has the benefits, without the drawbacks, of explosive field emission cathodes. In particular, when typical explosive field emission cathodes are utilized for high power microwave tubes, microwave pulse shortening can occur due to motion of the cathode plasma across the anode-cathode (A-K) gap. Ultimately, this gap closure can sufficiently change the diode impedance such that the tube can no longer operate under the desired conditions. CsI cathodes have offered one solution to this problem. These cathodes have demonstrated low A-K gap closure times with applied fields in the range of a few tens of kV/cm to several hundred kV/cm with currents into the several kiloampere range. This poster reviews the results of experiments on the Cathode Test Bed at the Air Force Research Laboratory/Phillips Laboratory site. We review experiments on a cathode produced by Voss Scientific, with emphasis on conditioning effects and gas evolution from the cathode.