Shielded Cold Cathodes for High Power Magnetrons

ABSTRACT: This program will investigate cold cathode field emission arrays as electron source for high power magnetrons. The approach uses lateral edge type field emitters which inject electrons horizontally, just above the surface of the substrate. The electrons are extracted laterally by a gate and injected into a vacuum region below magnetron sole electrode, which serves as a shielding structure for the emitters. A pusher electrode is used to direct these electrons radially outward through slits in the sole electrode/shield into the magnetron interaction space to follow a cycloidal trajectory. The cathode is divided into flat facets containing many slits which are joined together around a central metal rod. We will develop and fabricate shielded field emission arrays, on the faceted substrates, which are capable of achieving 10 A/cm2. These cathodes will be tested in a magnetron-like environment to determine reliability and lifetime. Electron emission uniformity and energy distribution will also be measured. Based on the measured and particle trajectory simulation results, a magnetron simulation will be run using ICEPIC. Facet emitters and arrays will be delivered to the sponsor as they are developed and finished shielded cold cathodes for magnetrons will be delivered at the end of Phase II. BENEFIT: The anticipated benefits of these cathodes are long lifetime, higher current denisty, lower operating voltage and potential low cost manufacturing for various applications. Main applications cover the insertion of high current density cold cathodes into existing microwave power tube (MPT) and emerging Micro Vacuum Electron Device (MVED) platforms. MPTs, encompassing primarily TWTs, klystrons, magnetrons, crossed-field amplifiers and gyrotrons are used in military applications such as radar and electronic warfare, civilian applications such as TV and radio broadcasting, microwave ovens and various types of research, and dual-use applications such as satellite broadcasting and communications. In 2008, ABI Research estimated to value of the MPT market to be a little under $1 Bn. Other applications of these cold cathodes include flat panel displays, high efficiency light sources, X-ray sources for medical imaging and industrial non-destructive testing, bio-medical sterilization and nanoelectronics.