Character and application of Scandia Doped Dispenser cathodes with concave surfaces

Since the cathodes with concave surfaces are required for the practical applications in most high-power vacuum electron devices, characteristics of nanosized-Scandia Doped Dispenser (SDD) cathodes with concave surfaces have been investigated, especially in dc applications. A space charge-limited (SCL) dc current density of over 50 A/cm² has been measured at 1000 °C_b. An on-going life test with a dc load of up to 40 A/cm² at 970 °C_b has been completed about 3000 hours of operation to date. The emission performance of the cathode was further evaluated in an electron gun test tube, which is a part of an mm wave CW-TWT, before the practical application in the real devices.