The mechanism of Pt films to suppress the electron emission of grid in TWTs

Pulsed grid-controlled traveling-wave tubes (TWTs) are widely used in the field of space and defense for navigation and directing of radars, aircrafts, satellites, and guided missiles. In order to attain even higher frequency and power requirements, gun designs for modern microwave tubes have utilized grids, which are very close to cathode. However, during the course of the TWTs work, electron emission substances such as Ba and BaO on the cathode can be evaporated and deposited on the counter electrode. Harmful electron emission from the grid, namely, grid emission, is very likely triggered, this in turn destroys the working condition of the controlled traveling-wave tube, making it necessary to suppress the electron emission properties of the grid. Pt films as an anti-emission material have been widely used, but little is known about its electron emission suppression characteristics and surface composition at high temperature when grids works. In our investigation, Pt films were deposited onto the surface of the molybdenum grids by ion-beam-assisted deposition (IBAD). The mechanism for electron emission suppression of the molybdenum grid coated with Pt films is discussed.