Thermal design considerations for fast warm-up cathodes in MM wave magnetrons

The paper discusses the thermal characteristics of various cathode structures for magnetrons using a computer code developed for this purpose. Methods for reducing warm-up time and input heating power for various oxide coated cathode configurations are suggested. A new “semi-indirectly heated” oxide coated cathode configuration with improved thermal characteristics is proposed. Materials with melting points less than that of conventional heater materials are considered for use in some configurations. The computed result of warm-up characteristics of directly heated cathode in actual thermal environment of millimeter wave magnetron is compared with experimental results and possible causes of disagreement between the two are discussed. Methods for improvement in temperature profiles of cathodes with large thermal loads are discussed