Study on the Ni–Re–Ir Sponge Oxide Cathode

In order to improve the emission performance and reliability of the oxide cathode for application in a microwave tube, an Ni-Re-Ir sponge reservoir oxide cathode has been developed and is presented in this paper. The emission current, the activity during lifetime, the emission uniformity, and the work function have been tested. The results show that the emission current of the cathode reaches 16 A/cm² with a 10-μs pulsewidth and a 1% duty cycle and that the emission current, after 3000-h lifetime at a temperature of 820 ^°C br, has decreased less than 5% with 1- A/cm² direct current. The analysis and test results of the thermal electron spectrometer indicate that the emission uniformity of the cathode can be improved to ensure that more than 80% of the cathode work-function distribution is in the range of 1.44-1.5 eV. The cathode has been successfully used many times in a miniature grid-controlled pulsed travelling wave tube for the launch of a manned space craft and a communication satellite.