Tungsten matrix for hot cathodes
Microwave vacuum electronic devices are the "heart" of modern and future defense electronic equipment as the power source of various radar, communication, remote sensing and telemetry, electronic countermeasures and precision guidance equipment. The hot cathode is the electron emission source of microwave vacuum electronic devices, and its performance and quality directly affect the working characteristics and service life of devices and systems. The research of hot cathode is one of the core of the research and development of microwave electrovacuum devices. Low operating temperature, high current density, high reliability and long life are the goals of cathode development. At present, the doped diffused hot cathode based on porous tungsten sponge matrix has a high ability of hot electron emission. The porous tungsten matrix is the skeleton of the hot cathode, and the pores in the matrix can store a lot of active emission substances and provide a huge reaction contact surface. Porous tungsten provides a migration and diffusion channel for the reactive barium atoms. The surface of porous tungsten matrix and the active barium atoms migrating from the surface also constitute the surface electron emission system. The ideal tungsten sponge matrix should have the characteristics of uniform pore dispersion, narrow pore size distribution, low closed pore ratio and high skeleton strength. Otherwise, the strength of the skeleton is not enough, and the reliability of the cathode is out of the question. The different pore size, high obturator rate and unequal distribution will lead to the decline of the ability of tungsten porous body to store, activate and transport the emission material, and the cathode is difficult to obtain uniform electron emission, thus the performance and life are limited. Therefore, the preparation technology and method of high quality porous tungsten matrix for hot cathode are very important.
